Control And Coordination Class 12 | Control and coordination class 12 notes
Choose the correct alternative
Exercise | Q 1.01 | Page 218
The nervous system of mammals uses both electrical and chemical means to send signals via neurons. Which part of the neuron receives impulse?
Axon
Dendron
Nodes of Ranvier
Neurilemma
Solution:
Dendron
Exercise | Q 1.02 | Page 218
___________ is a neurotransmitter.
ADH
Acetyl CoA
Acetyl choline
Inositol
Solution:
Acetyl choline is a neurotransmitter
Exercise | Q 1.03 | Page 218
The supporting cells that produce myelin sheath in the PNS are _________.
Oligodendrocytes
Satellite cells
Astrocytes
Schwann cells
Solution:
The supporting cells that produce myelin sheath in the PNS are Schwann cells.
Exercise | Q 1.04 | Page 218
A collection of neuron cell bodies located outside the CNS is called _________.
Tract
Nucleus
Nerve
Ganglionl
Solution:
A collection of neuron cell bodies located outside the CNS is called Ganglionl.
Exercise | Q 1.05 | Page 218
Receptors for protein hormones are located ________.
in cytoplasm
on cell surface
in nucleus
on Golgi complex
Solution:
Receptors for protein hormones are located on the cell surface.
Exercise | Q 1.06 | Page 218
If the parathyroid gland of man is removed, the specific result will be ___________.
onset of aging
disturbance of Ca++
onset of myxoedema
elevation of blood pressure
Solution:
If the parathyroid gland of man is removed, the specific result will be a disturbance of Ca++.
Exercise | Q 1.07 | Page 218
Hormone thyroxine, adrenaline, and nonadrenaline are formed from _____________.
Glycine
Arginine
Ornithine
Tyrosine
Solution:
Hormone thyroxine, adrenaline, and nonadrenaline are formed from Tyrosine.
Exercise | Q 1.08 | Page 218
Pheromones are chemical messengers produced by animals and released outside the body. The odour of these substance affects _____________.
skin colour
excretion
digestion
behaviour
Solution:
Pheromones are chemical messengers produced by animals and released outside the body. The odour of these substances affects behaviour.
Exercise | Q 1.09 | Page 218
Which one of the following is a set of discrete endocrine glands?
Salivary, thyroid, adrenal, ovary
Adrenal, testis, ovary, liver
Pituitary, thyroid, adrenal, thymus
pituitary, pancreas, adrenal, thymus
Solution:
Pituitary, thyroid, adrenal, thymus
Exercise | Q 1.1 | Page 218
After ovulation, the Graafian follicle changes into ___________.
Corpus luteum
Corpus albicans
Corpus spongiosum
Corpus callosum
Solution:
After ovulation, the Graafian follicle changes into Corpus luteum.
Exercise | Q 1.11 | Page 218
Which one of the following pairs correctly matches a hormone with a disease resulting from its deficiency?
Parathyroid hormone - Diabetes insipidus
Leutinising hormone - Diabetes mellitus
Insulin - Hyperglycemia
Thyroxine - Tetany
Solution:
Insulin - Hyperglycemia
Exercise | Q 1.12 | Page 218
___________ is in direct contact of brain in human.
Cranium
Duramater
Arachnoid
Piamater
Solution:
Piamater is in direct contact with the brain in a human.
Very very short answer question.
Exercise | Q 2.01 | Page 218
What is the function of the red nucleus?
Solution:
Near the centre of the midbrain is a mass of grey matter scattered within the white matter. It is called the red nucleus. It plays an important role in controlling posture and muscle tone, modifying some motor activities, and motor coordination.
Exercise | Q 2.02 | Page 218
What is the importance of Corpora quadrigemina?
Solution:
The corpora quadrigemina are four rounded elevations on the dorsal surface of the midbrain. The two superior colliculi are involved in visual reflexes and the two inferior colliculi are relay centres for auditory reflexes that operate when it is necessary to move the head to hear sounds more distinctly.
Exercise | Q 2.03 | Page 218
What does the cerebellum of the brain control?
Solution:
Cerebellum: It is the second-largest part of the brain and consists of two lateral hemispheres and a central vermis. It is composed of white matter with a thin layer of grey matter, the cortex. The white matter intermixes with the grey matter and shows a tree-like pattern called arborvitae. The surface of the cerebellum shows convolutions (gyri and sulci) a number of nuclei lie deep within each lateral or cerebellar hemisphere. Over 30 million neurons lie in the cortex. Three pairs of myelinated nerve bundles called cerebellar peduncles connect the cerebellum to the other parts of the CNS.
Functions: It is an important center that maintains the equilibrium of body, posture, balancing orientation, moderation of voluntary movements, maintenance of muscle tone. It is a regulatory center for neuromuscular activities and controls rapid activities like walking, running, speaking, etc. All activities of the cerebellum are involuntary (though may involve learning in early stages).
Exercise | Q 2.04 | Page 218
Name the three ossicles of the middle ear.
Solution:
Middle ear: It consists of a chain of three ear ossicles called Malleus (hammer), Incus (anvil), and Stapes (stirrup-the smallest bone). On receiving the vibrations from the tympanic membrane, the ear ossicles amplify the vibrations and transfer these to the cochlea.
A short Eustachian tube connects the middle ear to the pharynx. It equalizes air pressure on both sides of the eardrum.
Exercise | Q 2.05 | Page 218
Name the hormone which is an anti-abortion hormone.
Solution:
Progesterone
Exercise | Q 2.08 | Page 219
What is the cause of abnormal elongation of long bones of arms and legs and of the lower jaw?
Solution:
Excessive secretion of Growth Hormone causes abnormal elongation of long bones of arms and legs and of the lower jaw.
Exercise | Q 2.09 | Page 219
Name the hormone secreted by the pineal gland.
Solution:
Melatonin
Exercise | Q 2.1 | Page 219
Which endocrine gland plays an important, role in improving immunity?
Solution:
Thymus gland
Exercise | Q 3 | Page 219
Match the organism with the type of nervous system found in them.
| 1. Neurons | a. Earthworm |
| 2. Ladder-type | b. Hydra |
| 3. Ganglion | c. Flatworm |
| 4. Nerve net | d. Human |
Solution:
| 1. Neurons | d. Human |
| 2. Ladder-type | c. Flatworm |
| 3. Ganglion | a. Earthworm |
| 4. Nerve net | b. Hydra |
Very short answer question
Exercise | Q 4.1 | Page 219
Describe the endocrine role of islets of Langerhans.
Solution:
Islets of Langerhans are endocrine cells of the pancreas. They are four types of cells in Islets of Langerhans which have an endocrine role i.e. they secrete hormones.
i. Alpha cells (α cells): They constitute 20% of Islets of Langerhans. They secrete hormone glucagon. Glucagon stimulates glycogenolysis (the breakdown of glycogen) in the liver which causes hyperglycemia.
ii. Beta cells (β cells): They constitute 70% of Islets of Langerhans. They secrete insulin which stimulates glycogenesis (formation of glycogen) in the liver and muscles. Insulin causes hypoglycemia by increasing the uptake of glucose by cells.
iii. Delta cells (δ cells): They constitute 10% of Islets of Langerhans. These cells secrete somatostatin which inhibits the secretion of insulin and glucagon. It also lowers gastric secretions, motility, and absorption in the digestive tract. Somatostatin inhibits the release of growth hormone.
iv. PP cells or F cells: These cells secrete pancreatic polypeptide (PP) and inhibit the release of pancreatic juice.
Exercise | Q 4.2 | Page 219
Mention the function of testosterone?
Solution:
The group of hormones secreted by testis is androgens such as testosterone.
Functions of androgens:
i. It is also responsible for the appearance of secondary sexual characters such as facial and pubic hair, deepening of the voice, broadening of shoulders, male aggressiveness, etc.
ii. It involves in development of testis.
Exercise | Q 4.3 | Page 219
Give symptoms of the disease caused by hyposecretion of ADH.
Solution:
This condition causes excessive micturition or polyuria, polydipsia (increased thirst), etc.
Short answer question
Exercise | Q 5.01 | Page 219
Rakesh got hurt on his head when he fell down from his motorbike. Which inner membranes must have protected his brain? What other roles do they have to play?
Solution:
i. When Rakesh fell down from his motorbike the inner membranes called meninges protected his brain from injury.
ii. These meninges form a protective covering around the brain and spinal cord. They act as shock absorbers.
Exercise | Q 5.02 | Page 219
Give a reason - Injury to medulla oblongata may prove fatal.
Solution:
i. The medulla oblongata is a part of the brain stem.
ii. It controls involuntary vital functions like heartbeat, respiration, vasomotor activities, and peristalsis.
iii. It also controls non-vital reflex activities like coughing, sneezing, swallowing, vomiting, yawning, etc.
iv. Thus, damage or injury to medulla oblongata may disrupt these vital functions. Therefore, injury to medulla oblongata may prove fatal.
Exercise | Q 5.03 | Page 219
Distinguish between the sympathetic and parasympathetic nervous system on the basis of the effect they have on: a. Heartbeat b. Urinary Bladder
Solution:
i. Heart: Sympathetic nervous system accelerates the heartbeat whereas the parasympathetic nervous system decelerates the heartbeat.
ii. Urinary bladder: Sympathetic nervous system inhibits bladder contraction whereas the parasympathetic nervous system stimulates bladder contraction.
Exercise | Q 5.04 | Page 219
While holding a teacup Mr. Kothari’s hand's rattle. Which disorder he may be suffering from and what is the reason for this?
Solution:
1. This condition is due to Parkinson’s disease.
2. It is due to the degeneration of dopamine-producing neurons in the CNS.
3. 80% of the patients develop this condition along with stiffness, difficulty in walking, balance, and coordination.
Exercise | Q 5.05 | Page 219
List the properties of the nerve fibres.
Solution:
i. Excitability/Irritability: Nerve fibres have polarized membranes, thus they have the ability to perceive stimulus and enter into a state of activity.
ii. Conductivity: It is the ability of the nerve to transmit impulses along the whole length of the axon.
iii. Stimulus: It is any detectable, physical, chemical, electrical change in the external or internal environment which brings about excitation in a nerve/muscle/organ/organism. A stimulus must have a minimum intensity called threshold stimulus, in order to be effective. The subliminal (weak) stimulus will have no effect while the supraliminal (strong) stimulus will produce the same degree of impulse as the threshold stimulus.
iv. Summation effect: A single subliminal stimulus will have no effect but when many such weak stimuli are given again and again they may produce an impulse due to summation of effects.
v. All or none law: The nerve will either conduct the impulse along its entire length or will not conduct the impulse at all. This occurs in the case of a subliminal or weak stimulus.
vi. Refractory period: It is the time interval (about a millisecond) during which a nerve fails to respond to a second stimulus even if it is strong.
vii. Synaptic delay: The impulse takes about 0.3 to 0.5 milliseconds to cross a synapse. It is required for the release of neurotransmitters from the axon terminal and excitation in the dendron of the next neuron.
viii. Synaptic fatigue: The transmission of nerve impulses across the synapse stops temporarily due to the depletion of the neurotransmitter.
ix. Velocity: The rate of transmission of impulse is higher in long and thick nerves. It is higher in homeotherms than in poikilotherms. The velocity of transmission is higher in voluntary fibres (100 - 120 m/s in man) as compared to autonomic or involuntary nerves (10-20 m/s). In medullated nerve fibre, the velocity of transmission is higher as an impulse has to jump from one node of Ranvier to the next.
Exercise | Q 5.06 | Page 219
How does the tongue detect the sensation of taste?
Solution:
The tongue detects the sensation of taste due to gustatoreceptors.
Exercise | Q 5.07 | Page 219
State the site of production and function of Secretin, Gastrin, and Cholecystokinin.
Solution:
i. Site of production: Secretin, gastrin, and cholecystokinin are secreted in the gastrointestinal tract
ii. Functions:
Secretin: It is responsible for the secretion of pancreatic juice from the pancreas and bile from the liver.
Gastrin: It stimulates gastric glands to produce gastric juice.
Cholecystokin in CCK/ Pancreozymin PZ: It stimulates the pancreas to release enzymes and also stimulates the gall bladder to release bile.
Exercise | Q 5.08 | Page 219
An adult patient suffers from low heart rate, low metabolic rate, and low body temperature. He also lacks alertness, intelligence, and initiative. What can be this disease? What can be its cause and care?
Solution:
i. The patient may be suffering from myxoedema.
ii. It is caused due to the deficiency of thyroid hormones (hypothyroidism) in adults.
iii. Care: Patients should take prescribed medications regularly and eat food rich in iodine.
Exercise | Q 5.09 | Page 219
Where is the pituitary gland located? Enlist the hormones secreted by the anterior pituitary.
Solution:
The pituitary gland located just below the hypothalamus.
Hormones secreted by anterior pituitary:
i. Somatotropic Hormone (STH) / Somatotropin / Growth Hormone (GH): The secretion of GH is high till puberty later its secretion becomes low. However, it is continuously secreted throughout life for repair and replacement of body tissue or cells.
Functions:
a. It stimulates the growth of the body and the development of all tissues.
b. It accelerates protein synthesis and cell division.
c. It stimulates the release of growth hormone.
ii. Thyroid Stimulating Hormone (TSH) / Thyrotropin:
Function:
It stimulates the thyroid gland to produce the hormone thyroxine.
iii. Adrenocorticotropic Hormone (ACTH) / Adrenocorticotropin:
Functions:
a. It stimulates the adrenal cortex to produce its hormones.
b. It maintains the functioning of the adrenal cortex.
iv. Prolactin / Luteotropin/ Mammotropin : The secretion of this hormone is regulated by PIF (Prolactin inhibiting factor) of the hypothalamus.
Functions:
a. Activates the growth of mammary glands during pregnancy (mammotropin).
b. Stimulates milk production and secretion of milk (lactogenic) by the mammary gland after childbirth.
v. Gonadotropins:
a. Follicle Stimulating Hormone (FSH): In males, it stimulates the development of seminiferous tubules. In females, it stimulates the growth of ovarian follicles.
b. Luteinizing hormone (LH): LH induces the ruptured follicles to develop into corpus luteum and for the production of progesterone FSH and LH are responsible for the stimulation of ovaries to produce estrogen.
c. ICSH: In males, it stimulates the testes to produce the androgen called testosterone. Testosterone is responsible for the development of secondary sexual characters.
Exercise | Q 5.1 | Page 219
Explain how the adrenal medulla and sympathetic nervous system function as a closely integrated system.
Solution:
i. The adrenal medulla is the inner region of the adrenal gland. It is the modified sympathetic ganglion of the autonomic nervous system (ANS).
ii. The chromaffin cells of the adrenal medulla secrete hormones rather than releasing a neurotransmitter. These cells are innervated by sympathetic pre-ganglionic neurons of the autonomous nervous system (ANS).
iii. The autonomous nervous exerts direct control over the chromaffin cells, thus the hormones – adrenaline and nor adrenaline can be released quickly into the blood.
iv. The impulses from the hypothalamus stimulate sympathetic pre-ganglionic neurons which in turn stimulate the chromaffin cells to secrete adrenaline to nor-adrenaline.
v. The fight-or-flight response is initiated by nerve impulses from the hypothalamus to the sympathetic nervous system, including the adrenal medulla. This response rapidly increases circulation, promotes ATP production, and decreases non-essential activities.
Thus, the adrenal medulla and sympathetic nervous system function in a closely integrated manner.
Exercise | Q 5.11 | Page 219
Name the secretion of alpha, beta, and delta cells of islets of langerhans. Explain their role.
Solution:
Islets of Langerhans are endocrine cells of the pancreas.
They are four types of cells in Islets of Langerhans which have an endocrine role i.e. they secrete hormones.
i. Alpha cells (α cells): They constitute 20% of Islets of Langerhans. They secrete hormone glucagon. Glucagon stimulates glycogenolysis (the breakdown of glycogen) in the liver which causes hyperglycemia.
ii. Beta cells (β cells): They constitute 70% of Islets of Langerhans. They secrete insulin which stimulates glycogenesis (formation of glycogen) in the liver and muscles. Insulin causes hypoglycemia by increasing the uptake of glucose by cells.
iii. Delta cells (δ cells): They constitute 10% of Islets of Langerhans. These cells secrete somatostatin which inhibits the secretion of insulin and glucagon. It also lowers gastric secretions, motility, and absorption in the digestive tract. Somatostatin inhibits the release of growth hormone.
iv. PP cells or F cells: These cells secrete pancreatic polypeptide (PP) and inhibit the release of pancreatic juice.
Exercise | Q 5.12 | Page 219
Which are the 2 types of goitre? What are its causes?
Solution:
Hypersecretion of thyroid hormones: It is caused by an increase in the levels of thyroid hormones. This increases metabolic rate, sensitivity, sweating, flushing, rapid respiration, bulging of eyeballs, and affects various physiological activities. Graves’ disease: Hyperthyroidism in adults results in this disorder. It is characterised by protruding eyeballs, increased BMR, and weight loss. Increased BMR produces a range of effects like increased heartbeat, increased B.P., higher body temperature, nervousness, irritability, and tremor of fingers.
Simple goitre: It is iodine deficiency goitre. Iodine is required for the synthesis of thyroid hormone and if there is a deficiency of iodine in the diet, it causes enlargement of the thyroid gland leading to simple goitre. This disease is common in hilly areas. Addition of iodine to table salt prevents this disease. The size of the thyroid gland is increased but the total output of thyroxine is decreased.
Exercise | Q 5.13 | Page 219
Name the ovarian hormone and give their functions.
Solution:
Ovaries secrete the following hormones:
i. Progesterone: It is secreted by the corpus luteum of the ovary after ovulation. It is essential for the thickening of the uterine endometrium, thus preparing the uterus for implantation of the fertilized ovum. It is responsible for the development of mammary glands during pregnancy. It inhibits uterine contractions during pregnancy.
ii. Oestrogen: It is secreted by developing follicles. Estradiol is the main oestrogen. It is responsible for the development of secondary sexual characters in females.
iii. Relaxin: It is secreted by the corpus luteum of the ovary at the end of the gestation period. It relaxes the cervix of the pregnant female and the ligaments of the pelvic girdle to ease out the birth process.
iv. Inhibin: It is secreted by the corpus luteum. Inhibin inhibits FSH and GnRH production.
Answer the following.
Exercise | Q 6 | Page 219
Complete the table.
| Location | Cell Type | Function |
| PNS | ___________ | Produce myelin sheath |
| PNS | Satellite cells | _____________ |
| ___________ | Oligodendrocytes | Form myelin sheath around central axon |
| CNS | ___________ | Phagocytose pathogens |
| CNS | ___________ | Form the epithelial lining of brain cavities and central canal. |
Solution:
| Location | Cell Type | Function |
| PNS | Schwann cells | Produce myelin sheath |
| PNS | Satellite cells | Support the function of neurons |
CNS | Oligodendrocytes | Form myelin sheath around the central axon |
| CNS | Microglia or brain macrophages | Phagocytose pathogens |
| CNS | Ependymal cells | Form the epithelial lining of brain cavities and central canal. |
Long answer question.
Exercise | Q 7.01 | Page 219
Explain the process of conduction of nerve impulses up to the development of action potential.
Solution:
Polarisation and Depolarisation along a nerve
i. The nerve impulse is a wave of bioelectrical or electrochemical disturbances passing along a neuron.
ii. Neurons have a charged cellular membrane with a voltage that is different on the outer and inner side of the membrane. The plasma membrane separates the outer and inner solutions of different chemical compounds but having approximately the same total number of ions.
iii. The external tissue fluid has both Na+ and K+ but there is a predominance of Na+ and Cl-, while K+ is predominant within the fibre or in the intracellular fluid. This condition of a resting nerve is also called a polarised state.
iv. The polarized state of a neuron is established by maintaining an excess of Na+ on the outer side. On the inside, there is an excess of K+ along with large negatively charged protein molecules and nucleic acid.
v. Some amount of Na+ and K+ always leaks across the membrane. The Na+/K+ pump actively maintains the ionic gradient across the resting membrane. The sodium pump or Na-K allows the entry of K+ inside the membrane and exit of Na+.
vi. The difference in the distribution of Na+ and K+ on the two sides of the membrane produces a potential difference of – 50 to –100 millivolts (average is – 70 millivolts).
vii. The potential difference seen in a resting nerve is thus called resting potential (–70 millivolts) and it is mainly due to differential permeability of the resting membrane, which is much more permeable to K+ than to Na+. This results in slightly more K+ diffusing out than Na+ moving inside and causing a slight difference in polarity.
viii. Also, ions like negatively charged proteins and nucleic acids inside the cell make the overall charge negative on the inside and positive charge on the outside. The nerve membrane not only has leakage channels but also has many gated channels for Na+ /K+. These are also called voltage-gated channels. These channels enable the neuron to change its membrane potential to active potential in response to stimuli. The Na+ /K+ gated channels are separate so the transport of both these ions is separately done. However, during resting potential, both these gates are closed and the membrane resting potential is maintained.
ix. The resting potential of the membrane is maintained unless the stimulus reaches the neuron. Any change or disturbance to the membrane will cause Na+ to enter into the membrane and lower the potential difference (lesser than –70 millivolts). Thus, the membrane becomes more permeable to Na+
x. During resting potential, both gates are closed, and resting potential is maintained. However, during depolarization, the Na+ gates open and the K+ gates remain closed. This causes Na+ to rush into the axon and bring about depolarisation (opposite of polarity).
xi. The Extra Cellular Fluid (ECF) becomes electronegative with respect to the inner membrane which becomes electropositive. The value of action potential reaches +30 millivolts to +60 millivolts. This triggers depolarization in the next part while it itself starts going to repolarisation.
Exercise | Q 7.02 | Page 219
Draw the neat labelled diagram of the human ear.
Solution:
Exercise | Q 7.02 | Page 219
Draw the neat labelled diagram of the Sectional view of the human eye.
Solution:
Exercise | Q 7.02 | Page 219
Draw the neat labelled diagram of L. S. of the human brain.
Solution:
Exercise | Q 7.02 | Page 219
Draw the neat labelled diagram of Multipolar Neuron.
Solution:
Answer the question after observing the diagram given below
Exercise | Q 7.03 | Page 220
What do the synaptic vesicles contain?
Solution:
Synaptic vesicles contain neurotransmitter molecules.
Exercise | Q 7.03 | Page 220
What process is used to release the neurotransmitter?
Solution:
A neurotransmitter is released by the process of exocytosis.
Long answer question
Exercise | Q 7.03 | Page 220
What should be the reason for the next impulse to be conducted?
Solution:
a. When a neuron receives an impulse, it passes it to the next neuron. The impulse travels along the axon of the pre-synaptic neuron to the axon terminal.
b. Pre-synaptic neurons or axons have synaptic knobs at their ends or terminals. These synaptic knobs have synaptic vesicles that contain neurotransmitter molecules.
c. When the impulse reaches a synaptic knob, Ca+ channels open and Ca+ ions diffuse inward from the extracellular fluid.
d. This causes the release of neurotransmitters that bind to the receptors of the post synaptic cell.
e. The neurotransmitter is destroyed by the enzyme cholinesterase. A new impulse/ next impulse is generated and conducted to the synaptic gap.
Exercise | Q 7.03 | Page 220
Will the impulse be carried by the postsynaptic membrane carried even if one pre-synaptic neuron is there?
Solution:
a. A pre synaptic neuron when receives an impulse, releases a neurotransmitter into the synaptic cleft which is required to cross the gap between the axon terminal and the next neuron.
b. For further transmission of impulse, a pre-synaptic neuron is required that initiates the release of neurotransmitters that facilitate the movement of impulses across synapses.
Exercise | Q 7.03 | Page 220
Answer the question after observing the diagram given below.
Solution:
The ligand-gated ion channel is responsible for the transmission of the impulse.
Exercise | Q 7.04 | Page 220
Explain the Reflex Pathway with the help of a neat labelled diagram.
Solution:
i. The reflex pathway comprises at least one afferent neuron (receptor) and one efferent (effector or excitor) neuron appropriately arranged in a series.
ii. The afferent neuron receives a signal from a sensory organ and transmits the impulse via a dorsal nerve root into the CNS (at the level of the spinal cord).
iii. The efferent neuron then carries signals from CNS to the effector. The stimulus and response thus form a reflex arc as shown below in the knee jerk reflex.
Exercise | Q 7.05 | Page 220
Krishna was going to school and on the way, he saw a major bus accident. His heartbeat increased and hands and feet become cold. Name the part of the nervous system that had a role to play in this reaction.
Solution:
The sympathetic nervous system controls body activities during fight, fright, or flight situations. It activates the release of the hormones adrenaline and nor-adrenaline due to which the heartbeat increased, hands and feet become cold.
Exercise | Q 7.06 | Page 220
What will be the effect of thyroid gland atrophy on the human body?
Solution:
Thyroid gland atrophy causes hypothyroidism.
For effects of thyroid gland atrophy on the human body:
Hyposecretion of thyroid hormone: It is caused by a deficiency of thyroid hormones or removal of the thyroid gland (Thyroidectomy).
a. Cretinism: It is caused due to deficiency of thyroid hormones in infants. A cretin (individual suffering from cretinism) has reduced BMR and low oxidation. They are short-statured because the skeleton fails to grow. They are mentally retarded, show stunted growth and delayed puberty. They show dry skin, thick tongue, prolonged neonatal jaundice, lethargy and constipation. This can be treated by early administration of thyroid hormones.
b. Myxoedema: It is caused due to the deficiency of thyroid hormones in adults. It is characterised by a peculiar thickening and puffiness of skin and subcutaneous tissue particularly of the face and extremities. The patient lacks alertness, intelligence. The patient suffers from slow heart rate, low B.P., low body temperature (feels cold) and stunted sexual development.
c. Simple goitre: It is iodine deficiency goitre. Iodine is required for the synthesis of thyroid hormone and if there is a deficiency of iodine in the diet, it causes enlargement of the thyroid gland leading to simple goitre. This disease is common in hilly areas. Addition of iodine to table salt prevents this disease. The size of the thyroid gland is increased but the total output of thyroxine is decreased.
Exercise | Q 7.08 | Page 220
Explain the role of the hypothalamus and pituitary as a coordinated unit in maintaining homeostasis?
Solution:
i. The hypothalamus controls the secretory activity of the pituitary gland (anterior pituitary) by producing, releasing, and inhibiting hormones.
ii. Anterior pituitary and intermediate lobes are connected to the hypothalamus through the hypophyseal portal system. Various hormones secreted by the hypothalamus reach the pituitary gland through the hypophyseal portal system.
iii. The portal vein collects blood from various parts of the hypothalamus and opens into the anterior lobe of the pituitary. From the pituitary, the vein finally carries the blood into the superior vena cava. It helps in the feedback mechanism for hormonal control.
iv. Also, a negative feedback mechanism takes place in the form of hormones released by the target glands to decrease the secretion of the pituitary gland.
v. In such a negative feedback mechanism, the secretion of ACTH, TSH, and gonadotropins (FSH and LH) decreases when their target gland hormone levels rise.
e.g. Adrenocorticotropic hormone (ACTH) stimulates the cortex of the adrenal gland to secrete glucocorticoids, mainly cortisol. In turn, an elevated blood level of cortisol decreases secretion of both corticotropin and corticotropin-releasing hormone (CRH) by suppressing the activity of the anterior pituitary corticotrophs and neurosecretory cells.
Exercise | Q 7.09 | Page 220
What is adenohypophysis? Name the hormones secreted by it?
Solution:
Adenohypophysis: It is an outgrowth from the roof of the buccal cavity. This outgrowth is called Rathke’s pouch. It grows upwards towards the brain. It is the larger lobe of the pituitary gland. It is a highly cellular and vascular part of the pituitary gland. It contains various types of epitheloid secretory cells, acidophils, basophils, chromatophores. It is further divided into three parts - Pars distalis, pars tuberalis, and pars intermedia. Pars intermedia is poorly developed in human beings. It is a small reduced part lying in the cleft between the anterior and posterior lobe. It secretes Melanocyte Stimulating Hormone (MSH) in some lower vertebrates. MSH stimulates the dispersion of melanin granules in melanocytes and is responsible for skin pigmentation.
The pituitary gland located just below the hypothalamus.
Hormones secreted by anterior pituitary:
i. Somatotropic Hormone (STH) / Somatotropin / Growth Hormone (GH): The secretion of GH is high till puberty later its secretion becomes low. However, it is continuously secreted throughout life for repair and replacement of body tissue or cells.
Functions:
a. It stimulates the growth of the body and the development of all tissues.
b. It accelerates protein synthesis and cell division.
c. It stimulates the release of growth hormone.
ii. Thyroid Stimulating Hormone (TSH) / Thyrotropin:
Function:
It stimulates the thyroid gland to produce the hormone thyroxine.
iii. Adrenocorticotropic Hormone (ACTH) / Adrenocorticotropin:
Functions:
a. It stimulates the adrenal cortex to produce its hormones.
b. It maintains the functioning of the adrenal cortex.
iv. Prolactin / Luteotropin/ Mammotropin: The secretion of this hormone is regulated by PIF (Prolactin inhibiting factor) of the hypothalamus.
Functions:
a. Activates the growth of mammary glands during pregnancy (mammotropin).
b. Stimulates milk production and secretion of milk (lactogenic) by the mammary gland after childbirth.
v. Gonadotropins:
a. Follicle Stimulating Hormone (FSH): In males, it stimulates the development of seminiferous tubules. In females, it stimulates the growth of ovarian follicles.
b. Luteinizing hormone (LH): LH induces the ruptured follicles to develop into corpus luteum and for the production of progesterone FSH and LH are responsible for the stimulation of ovaries to produce estrogen.
c. ICSH: In males, it stimulates the testes to produce the androgen called testosterone. Testosterone is responsible for the development of secondary sexual characters.
Exercise | Q 7.1 | Page 220
Describe in brief, an account of disorders of the adrenal gland.
Solution:
Disorders of the adrenal gland:
i. Addison’s disease: It is caused due to hypersecretion of glucocorticoids (hormone secreted adrenal cortex). It is characterized by low blood sugar, low Na+, and high K+ concentration in plasma increased loss of Na+ and water in urine. It leads to weight loss, weakness, nausea, vomiting, and diarrhoea.
ii. Cushing’s disease: It is caused due to Hyposecretion of mineralocorticoids (a hormone secreted by the adrenal cortex) It leads to high blood sugar levels, excretion of glucose in the urine, rise in Na+ level in the blood, high blood pressure, obesity, and wasting of limb muscles.
Exercise | Q 7.12 | Page 220
Describe in brief an account of disorders of the thyroid.
Solution:
Hormones are released in very minute quantities. They produce their effect on the target cells by binding to hormone receptors. The hormone receptors are present on the cell membrane (i.e. membrane receptors) or maybe intracellular receptors.
i. Mode of hormone action through membrane receptors:
a. Hormones like catecholamines, peptide, and polypeptide hormones are not lipid-soluble and they cannot enter their target cells through the plasma membrane. These non-steroid water-soluble hormones interact with surface receptors and initiate metabolic activity.
b. Molecules of amino acid derivatives, peptide hormones bind to specific receptor molecules located on the plasma membrane.
c. The hormone-receptor complex causes the release of an enzyme adenylate cyclase from the receptor site. This enzyme forms cyclic AMP from ATP of the cell.
d. cAMP activates enzymatic actions. The hormone acts as the first messenger and the cAMP acts as the second messenger.
e. Some other secondary messengers are Ca++, cGMP, and IP3 (Inositol triphosphate), etc.
ii. Mode of action through intracellular receptors:
a. Steroid and thyroid hormones are lipid-soluble and can easily pass through the plasma membrane of the target cell into the cytoplasm.
b. In the cytoplasm, they bind to specific intracellular receptors proteins forming a hormone-receptor complex that enters the nucleus.
c. The hormone-receptor complex binds to a specific regulatory site of DNA, in the nucleus.
d. The activated genes transcribe mRNA which directs protein synthesis and enzymes in the cytoplasm.
e. The action of lipid-soluble hormones is slow but long-lasting,
Very Short Answer | Q 7
Name the hormone secreted by Pars intermedia in lower vertebrates.
Solution:
Melanocyte stimulating hormone (MSH) is secreted by Pars intermedia in lower vertebrates.
control and co-ordination class 12 notes pdf state board
Unicellular organisms have a simple
organisation of their life processes. However
a multicellular organisation of the body
organs and organ systems required both, a
control over their life processes as well as a
coordination between the various systems in
order to maintain homeostasis of the organism.
Plants and animals both show a control and
coordination mechanism.
In plants this done
by sending chemical signals and brining about
various types of movements (e.g. phototropic,
chemotactic, thingmotactic, etc). Animals,
specially the higher vertebrates show a gradual
increase in the complexity of their control and
coordination by giving both electrical and
chemical singles. In this chapter now you will
study about development of nervous system
in different animal groups and details of the
system in humans.
The porifera (sponges) are the most
primitive of the animal phyla
Even though there are different types of
cells in sponges for carrying out different
functions, a proper nervous system is lacking.
However to bring about efficient working of
the body these multicellular animals show
division of labour among the cells. This leads to
specialization of cells for the various activities
like digestion, respiration, excretion and others.
Later in the higher animals, phyla the different cells form tissues, organs and systems which
must work in coordination with each other for
smooth internal functioning of the body. Also
the organism must be able to respond and
coordinate with respect to various stimuli or
changes in the external environment.
In the lower animals like Hydra and
Planaria the nervous system achieves this
function, while in higher more complex
animals, it is done by two coordinating systems
- the nervous (elctrical) system and endocrine
(chemical) control system. These two systems
will be studied separately though they work in
coordination with each other.
Nervous System in Hydra :
Hydra, a cnidarian shows the diffused
nervous system, which is the most primitive
nervous system. The cnidarians are thus the
first animal group showing true simple nervous
system. It consists of the sensory cells and the
nerve cells or neurons along with their fibres.
The nerve cells are scattered or distributed
throughout the body and inter connected to
each other by synapses between their fibres to
form the nerve net. There are two nerve nets
both in the mesoglea, one connected towards
the epidermis and second towards the gastrodermis. There are sensory cells scattered in the body wall and tentacles, but sense organs are
lacking.
Neurons have fibres but there are no
sensory and motor nerves. The nerve impulse
shows no polarity or direction. Thus in Hydra,
activation of sensory cells can happen at any
point, and from this point impulse can be carried
through out the body in any direction, thus
bringing movements of the body or tentacles
eg. catching of prey during feeding.
The diffused types of nervous system is the
first important landmark in the nervous system.
It is seen in the ctenophora as well as in the
enteric system or gut wall of higher animals
including man.
Nervous System in Planaria (flatworm) :
Planaria is a flatworm belonging to the
phylum platyhelminthes. It is the most primitive
animal with a central nervous system (CNS)
located on the ventral side of body. It consists
of a mass of cerebral or cephalic ganglion
appearing like an inverted U shaped brain.
These lie in the anterior or head region and from
each ganglion arise nine branches towards the
outer side. Ventrally from below the ganglia
arise a pair of Ventral Nerve Cords (VNC) or
long nerve cords. These are inter connected
to eachother by transfer nerve or commissure
in a ladder like manner. The peripheral nerve
plexus arising laterally from VNC. The PNS
Transmission of nerve impulse :
The neurons are cells with some specials
features. The cells can be excited. The
nerve impulse is a wave of bioelectrical or
electrochemical disturbances passing along a
neuron. The transmission of the nerve impulse
along the long nerve fibre/axon tube is a
result of electrical charges across the neuronal
membrane during conduction of an excitation.
Each neuron has a charged cellular membrane
with a voltage which is different on the outer
and inner side of the membrane. The plasma
membrane separates the outer and inner
solutions of different chemical compounds but
having approximately the same total number
of ions. The external tissue fluid has both Na+
and K+ but there is predominance of Na+
and
Cl-
, while K+ is predominant within the fibre
or in the intracellular fluid. This condition of
a resting nerve is also called a polarised state
and it is established by maintaining an excess
of Na+
on the outerside. On the inside there is
an excess of K+ along with large negatively
charged protein molecules and nucleic acid.
Some amount of Na+
and K+ is always leaks
across the membrane. The Na+
/K+ pump in the
membrane actively restores the ions to their
appropriate side. Against the concentration and
electrochemical gradient, Na+
is being forced
out and K+ isbeing forced inside the membrane.
This process is called sodium pump or Na-K
exchange pump. This active process requires
ATP energy. The difference in distribuiton of
Na+
and K+ on the two sides of the membrane
produces a potential difference of -50 to -100
millivolts (average is -70 millivolts).
This potential difference seen in a resting
nerve is thus called resting potential. (-70
millivolts) and it is mainly due to differential
permeability of the resting membrane which
is much more permeable to K+
than to Na+
.
This results in slightly more K+
diffusing out
than Na+ moving inside and causing slight
difference in polarity. Also ions like negatively
charged proteins and nucleic acids inside the
cell make the overall charge negative on the
inside and positive charge on the outside.
The nerve membrane not only has leakage
channels but also has many gated channels for
Na+
/K+
.
These are also called voltage gated
channels. These channels enable the neuron
to change it membrane potential to active
potential in response to a stimuli. The Na+
/K+
gated channels are separate so transport of
both these ions is separately done. However
during resting potential, both these gates are
closed and the membrane resting potential is
maintained.
Disorder related to pancreas :
Diabetes mellitus (Hyperglycemia)
This is the most common metabolic
endocrine disorder of pancreas. It leads to
increase in blood glucose level. This is due to
under activity of Beta cells, which results in
reduced secretion of insulin. In children, such a
condition is called insulin dependent diabetes
mellitus/ Type I (IDDM) The other form of
diabetes is Non insulin dependent diabetes
mellitus/ Type II (NIDDM). It is caused due
to failure of insulin to facilitate the movement
of glucose into cells. Reduced sensitivity to
insulin is called insulin resistance.
In both disorders, blood glucose level
increases. Some of the glucose is excreted in
urine. It also causes excessive urination and
dehydration of body tissues. Degradation
of fats increases formation of ketone bodies
(ketosis). Administration of insulin lowers
blood glucose level.
I. Gonads :
Gonads are sex organs (the testes and the
ovaries).
i. Ovaries : They produce
1. Estrogen : These are secreted by developing
follicle. Estradiol is the main oestrogen. It is
responsible for secondary sexual characters
in female.
2. Progesterone : It is secreted by corpus
luteum of the ovary after ovulation. This
hormone is essential for thickening of
uterine endometrium, thus preparing the
uterus for implantation of fertilized ovum. It
is responsible for development of mammary
glands during pregnancy. It inhibits uterine
contractions during pregnancy.
3. Relaxin : It is secreted by the corpus luteum
of the ovary at the end of gestation period.
It relaxes the cervix of the pregnant female
and ligaments of pelvic girdle for easy birth
of young one.
4. Inhibin : It is secreted by the corpus
luteum. Inhibin inhibits the FSH and GnRH
production.
ii. Testes :
Testes secrete male sex hormones called
androgens such as testosterone.
Testosterone : It is secreted from interstitial
cells or Leydig cells by the influence of
luteinising hormone (LH).
Rise in testosterone
level in blood above normal inhibits LH
secretion.
It is also responsible for appearance of
secondary sexual characters such as facial and
pubic hair, deepening of voice, broadening of
shoulders, male aggressiveness, etc. It also
helps in maintenance of testes.
J. Diffuse endocrine glands
Placenta :
It is the intimate connection between foetus
and uterine wall of the mother for physiological
exchange of the material. Placenta is a
temporary endocrine gland.
During pregnancy, placenta secretes
hormones such as estrogen, progesterone, hCG
(Human Chorionic Gonadotropin) and human
placental progesterone. These hormones check
the contraction of uterine muscles and also
maintain the thickness of uterine endometrium
thus they help to maintain pregnancy.
Gastro intestinal tract :
In the gastrointestinal mucosa, certain cells
are endocrine in function. These cells produce
hormones which play vital role in digestive
processes and flow of digestive juices.
1. Gastrin : It stimulates gastric glands to
produce gastric juice.
2. Secretin : It is responsible for secretion of
pancreatic juice and bile from presence and
liver.
3. Cholecystokinin CCK/ Pancreozymin PZ
: This hormone stimulates the pancreas to
Chemicals that operate between members of the same species are social hormones or
pheromones. These are commonly also called sex attractants or external hormones.
A pheromone is a volatile substance produced and discharged by an organism, which
induces a physiological response in other organism of the same species. Pheromones are
produced by many species of insects. Some pheromones enhance the chance of mating between
the sexes.
These are called signaling pheromones used to induce a behavioral response. Social
insects such as ants make use of signaling pheromones to locate food sources and warn of
danger.
Worker bees are females maintained in a sterile state by the pheromone called anti– queen
factor produced by queen. The factor spreads among the workers preventing maturation of
the ovaries of workers as long as the queen is present in the bee hive. Increase in colony size
results in dilution of pheromones and second queen may develop.
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