Solutions-Class-12-Biology-Chapter-9-Control and Coordination-Maharashtra Board

(b) Dendron

(c) Acetyl choline

(d) Schwann cells

(d) Ganglionl

(b) on cell surface

(b) disturbance of Ca++

(d) Tyrosine

(d) behavior

(c) Pituitary, thyroid, adrenal, thymus

(a) Corpus luteum

(c) Insulin - Hyperglycemia

(d) Piamater

Red nucleus plays an important role in controlling posture and muscle tone. modifying some motor activities and motor coordination.

Corpora quadrigemina consists of 4 solid rounded structures. viz. superior and inferior colliculi. Superior colliculi control visual reflexes while inferior colliculi control

auditory reflexes.

Cerebellum of brain is an important centre which maintains equilibrium of body posture. balancing orientation, moderation of voluntary movements and maintenance of muscle tone

(i) Malleus [hammer], (ii) incus [anvil] and (iii) stapes [stirrup] are the three ossicles of the middle ear

Progesterone is anti-abortion hormone

Placenta is a temporary endocrine gland.

Steroid hormones

Hypersecretion of growth hormones in adults causes abnormal elongation of long bones of arms and legs and of lower jaw i.e. acromegaly.

Pineal gland secretes a hormone called melatonin also known as sleep hormone.

The endocrine gland, thymus plays an important role in improving immunity.

Endocrine cells of pancreas form groups of cells called Islets of Langerhans. There are four kinds of cells in islets of Langerhans which secrete hormones.

• Alpha (α) cells : They are 20% and secrete glucagon. Glucagon is a hyperglycemic hormone. It stimulates liver for glucogenolysis and increases the blood glucose level.
• Beta (β) cells : They are 70% and secrete insulin. Insulin is a hypoglycemic hormone. It stimulates liver and muscles for glycogenesis. This lowers blood glucose level.
• Delta (δ) cells : They are 5% and secrete somatostatin. Somatostatin inhibits the secretion of glucagon and insulin. It also decreases the gastric secretions. Motility and absorption in digestive tract. In general, it is a growth inhibiting factor.
• PP cells or F cells : They form 5%. They secrete pancreatic polypeptide (PP) which inhibits the release of pancreatic juice.

Testosterone is a steroid sex hormone secreted by testes and cortex of adrenal glands. It controls the secondary sexual characters in males.

Polydipsia, i.e. frequent thirst and polyuria i.e. frequent urination are the symptoms of the dlsease caused by hyposecretion of ADH.

When Rakesh fell down from his motorbike, the inner membranes that protected his brain were meninges, viz. dura mater, arachnoid membrane and pia mater. Morevover, CSF must have also acted as a shock absorber.

• Dura mater : It is the outer tough membrane protective in function.
• Arachnoid membrane : It is the middle web-like membrane which communicates with fluids of upper sub dural space and lower sub arachnoid space.
• Pia mater: It is the innermost highly vascularised nutritive membrane in close contact with brain and spinal cord.

• Medulla oblongata is the region of the brain that controls all the involuntary activities.
• Vital activities such as heartbeats, respiration, vasomotor activities, peristalsis. etc. are under the control of medulla oblongata.
• Thus, damage or injury to medulla oblongata may disrupt these vital functions and lead to serious complications such as respiratory failure, cardiac arrest, and shock.
• Therefore, injury to medulla oblongata may prove fatal

• This condition is due to Parkinson's disease.
• It is due to degeneration of dopamine-producing neurons in the CNS.
• 80% of the patients develop this condition along with stiffness. difficulty in walking, balance and coordination.

• Excitability/irritability
• Conductivity
• Stimulus
• Summation
• All or none law
• Refractory period
• Synaptic delay
• Synaptic fatigue

• The surface of tongue is with gustatoreceptors.
• These receptors are sensitive to the chemicals like sweet. salt, sour, bitter and umami (savory) which is present in the food.
• The receptor cells get stimulated. Generate the impulse which is given to the sensory neuron.

(i) Secretin :

• Site of production : Duodenal mucosa
• Functions : Stimulates secretion of pancreatic juice and bile from pancreas and liver respectively.

(ii) Gastrin :

• Site of production : Gastric mucosa
• Functions : Stimulates gastric glands to secrete gastric juice.

(iii) Cholecystokinin :

• Site of production : Duodenal mucosa
• Functions : Stimulates pancreas and gall bladder to release pancreatic enzymes and bile respectively.

• The above symptoms indicate that the person is suffering from Myxoedema.
• Myxoedema is condition caused due to hypothyroidism.
• Hypothyroidism causes deficiency of thyroid hormones like T₃ and T₄ (thyroxine). This results in low BMR.
• This condition can be cured by giving injections of thyroxine or tablets containing hormone preparation.

• The pituitary gland is attached to hypothalamus on the ventral surface of
• It is lodged in a bony depression called sella turcica of sphenoid bone.

It secretes following hormones :

• GH : [Growth Hormone/STH : Somatotropic Hormone]
• TSH/TTH - [Thyroid Stimulating Hormone/Thyrotropic Hormone]
• ACTH - [adrenocorticotropic hormone]
• PRL - [prolactin]
• Gonadotropins - (a) FSH [follicle stimulating hormone], (b) LH/ICSH — [leutinizing hormone/ interstitial cells stimulating hormone]

• Adrenal medulla originates from embryonic neuro-ectoderm.
• It consists of rounded group of large granular cells called chromaffin cells. They are modified post-ganglionic cells of sympathetic nervous system which have lost normal processes and acquired glandular function.
• These cells are connected with pre-ganglionic fibres of sympathetic nervous system.
• Hence adrenal medulla is an extension of sympathetic nervous system.
• Thus adrenal medulla and sympathetic nervous system functions as a closely integrated system.

(i) Alpha cells :

• Secretion : Glucagon
• Role : Stimulates glycogenolysis in the liver

(ii) Beta cells :

• Secretion : Insulin
• Role : Stimulates glycogenesis in the liver and muscles

(iii) Delta cells :

• Secretion : Somatostatin
• Role : Inhibits the secretion of glucagon and insulin. It also decreases the gastric secretions, motility and absorption in digestive tract.

Goitre is the enlargement of thyroid gland. It is easily visible at the base of neck when a person is suffering from it. Goitre is of two types.

• Simple goitre : It is also called endemic goitre. This is due to iodine deficiency in the food. This causes iodine deficit in blood. In an attempt to take more iodine from blood, the blood supply to the gland increases. This results in swelling on the
• Exophthalmic goitre : It is also called toxic goitre. This is due to hyperactive thyroid gland. This can happen if there is overstimulation of thyroid due to excess of ACTH. This disorder is also called Graves disease or hyperthyroidism.

Ovaries produce following hormones :

• Oestrogen : It is responsible for secondary sexual characters in female.
• Progesterone : 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.
• Relaxin : It relaxes the cervix of the pregnant female and ligaments of pelvic girdle during parturition.
• Inhibin : It inhibits the FSH and GnRH production.

• The origin and maintenance of resting potential depends on the original state of no stimulation.
• Any stimulus or disturbance to the membrane will make the membrane permeable to Na⁺ This causes rapid influx of Na⁺ ions.
• The voltage gated Na⁺/K⁺ channels are unique. They can change the potential difference of the membrane as per the stimulus received and also the gates operate separately and are self closing.
• During resting potential, both gates are closed and resting potential is maintained.
• However during depolarization, the Na⁺ channels open but not the K⁺ This causes Na⁺ to rush into the axon and bring about a depolarisation. This condition is called action potential.
• Extra cellular fluid (ECF) becomes electronegative with respect to the inner membrane which becomes electropositive.

Synaptic vesicles contain a neurotransmitter — acetyl choline.

Exocytosis.

Removal of neurotransmitter by the action of acetyl cholinesterase.

Yes. As far as impulse is transmitted by pre-synaptic neuron, it will be received by post-synaptic neuron.

Ca⁺⁺ channel is responsible for their transmission

Reflex action : Reflex action is defined as a quick, automatic involuntary and often unconscious action brought about when the receptors are stimulated by external or internal stimuli.

Reflex arc : Reflex actions are controlled by CNS. Reflex arc is the structural or functional unit of reflex action. Simple reflex arc is formed of the following five components.

• Receptor organ : The sensory part that receives the stimulus is called receptor organ. It can be any sense organ that receives the stimulus and converts it into the impulse. e.g. skin, eye, ear, tongue, nasal epithelium, etc.
• Sensory neuron or afferent neuron : Sensory part carrying impulse from receptor organ to CNS is called sensory neuron. Its cyton is located in dorsal root ganglion. Its dendron is long and connected to receptor while the axon enters in the grey matter of spinal cord to form a synapse.
• Association, adjustor or intermediate neuron : It is present in the grey matter of spinal cord. Receiving impulse from sensory neuron, interpreting it and generating motor impulse are done by association neuron.
• Motor neuron (effector) : The cyton of motor neuron is present in the ventral horn of grey matter and axon travels through ventral root. It conducts motor impulse from spinal cord to effector organ.
• Effector organ : Effector organ is a specialized part of the body which is excited by receiving the motor impulse. It gives proper response to the stimulus, e.g. muscles or glands. The path of reflex action is followed by the unidirectional impulse. It originates in the receptor organ and ends in effector organ through CNS.

• The part of the nervous system that had a role to play in Krishna’s reaction is the sympathetic nervous system.
• Emergency conditions trigger sympathetic nervous system to stimulate adrenal medulla.
• The cells of adrenal medulla secrete catecholamines like adrenaline and nor-adrenaline. These hormones have direct effect on the pacemaker of the heart which causes increase in the heart rate and other associated symptoms.
• This system controls body activities during fight, fright, or flight situations, by intervention of sympathetic nervous system.

• Atrophy means degeneration. Atrophy of thyroid gland will result in deficient secretion of thyroid hormones leading to hypothyroidism. Deficiency of thyroid hormones [T₃ and T₄] and thyrocalcitonin will cause following effects on the body.
• Decrease in BMR i.e. basal metabolic rate, decrease in the blood pressure, heart beat, body temperature. etc.
• Occurrence of myxoedema in which there is abnormal deposition of fats under the skin giving puffy appearance in adults.
• Irregularities in menstrual cycle in case of female patients.
• Hair become brittle and fall.
• Calcium metabolism also disturbs due to lack of thyrocalcitonin.

TSH by adenohypophysis

Relaxin by degenerating corpus luteum of the ovary.

Secretin by duodenal mucosa

Calcitonin [hypocalcemic hormone] by thyroid and parathormone [hypcrcalcemic hormone] by parathyroid glands.

ADH by hypothalamus

Atrial natriuretlc factor by atria of heart.

Aldosterone by adrenal cortex

T₃ and T₄ by thyroid gland.

Oxytocin by hypothalamus.

Adrenaline. non-adrenaline [stimulation] and acctylcholine [inhibition] by adrenal medulla.

GHRF by hypothalamus.

FSH by anterior pituitary.

• Homeostasis is maintenance of constant internal environment of the body.
• When certain hormones from any endocrine glands are secreted in excess quantity, the inhibiting factors from hypothalamus, automatically exert negative feedback and stop the production of stimulating hormones from pituitary.
• Similarly, if any hormone is in deficit, then the concerned gland is given message through releasing factor. This way the hormone production remains in a balanced state or homeostasis.
• g. If thyroxine from (hyrold gland is secreted in excess, the secretion of TSH from pituitary is stopped by stopping the production of TRF from hypothalamus.
• Though most of the endocrine glands are under the influence of pituitary gland, it is in turn controlled by hypothalamus.
• Hypothalamus secretes releasing factors and inhibiting factors and hence regulate the secretions of pituitary (hypophysis).
• There is negative feedback mechanism in controlling the secretions of the endocrine glands.
• Hypothalamus forms the hypothalamo-hypophyseal through which transportation of neurohormones take place.

Following are the releasing and inhibiting factors produced by hypothalamus :

• Somatotropin/GHREF : It stimulates release of growth hormone.
• Somatostatin/GHRIF : It inhibits the release of growth hormone,
• Adrenocorticotropin Releasing Hormone/CRF : It stimulates the release of ACTH by the anterior pituitary gland.
• Thyrotropin Releasing Hormone/TRF : It stimulates the release of TSH by anterior pituitary gland.
• Gonadotropin Releasing Hormone (GnRH) : It stimulates pituitary to secrete gonadotropins.
• Prolactin Inhibiting Hormone (Prolactostatin) : It inhibits prolactin released by anterior pituitary gland.
• Gastrin Releasing Peptide (GRP).
• Gastric Inhibitory Polypeptide (GIP).

• Adenohypophysis is the large anterior lobe of pituitary gland.
• It is derived from embryonic ectoderm in the form of Rathke‘s pouch which is a small outgrowth from the roof of embryonic
• It is made up of epitheloid secretory cells.

It secretes following hormones :

• GH : [Growth Hormone/STH : Somatotropic Hormone]
• TSH/TTH - [Thyroid Stimulating Hormone/Thyrotropic Hormone]
• ACTH - [adrenocorticotropic hormone]
• PRL - [prolactin]
• Gonadotropins - (a) FSH [follicle stimulating hormone], (b) LH/ICSH — [leutinizing hormone/ interstitial cells stimulating hormone]

Disorders of adrenal cortical secretions are caused due to hyporsecretion and hypersecretion of adrenal corcoid harmones.

Hyposecretion of corticosteroids causes Addison's disease :

• The symptoms of Addison's disease are low blood sugar, low body temperature, feebie heart action, low BP. acidosis. low Na⁺ and K⁺ concentration in plasma. excessive loss of Na⁺ and water in urine, impaired kidney functioning and kidney failure. etc. it leads to weight loss, general weakness. Nausea, vomiting and diarrhoea.

Hypersecretion of corticoid Cushing's disease :

• The symptoms of Cushings disease are high blood sugar level, glucosuria, alkalosis, enhancement of total quantity of electrolytes in extracellular fluid, polydipsia, increased BP muscle paralysis, obesity, wasting of limb muscles. etc.

The hormones always act on their target organs or tissues to induce their effects.

The target tissues have specific binding sites or receptor sites which contain hormone receptors.

Steroid hormones :

• The steroid hormones are lipid soluble and can easily cross the lipoproteinous plasma membrane.
• The hormone receptors for steroid hormones are present in cytoplasm or in nucleus.
• Hormone-receptor complex formed in cytoplasm enters the nucleus and regulate the gene expression or chromosome function.
• In some cases the receptors are present inside the nucleus where hormone receptor complex is formed.
• These complexes interact with the genome to evoke biochemical changes that result in physiological and developmental functions.

Protein hormones :

• The hormone receptors for protein hormones are present on the cell membrane (i.e. membrane bound receptors).
• When the hormone binds to its receptor, it forms hormone-receptor complex. Each receptor is specific to a specific hormone.
• The hormones which interact with membrane bound receptors normally do not enter the target cell but generate second messengers. Such as cyclic AMP, Ca⁺⁺ or IP (Inositol triphosphate), etc.
• This leads to certain biochemical changes in the target tissue.
• Thus the tissue metabolism and consequently the physiological functions are regulated by hormones.

Disorders of thyroid gland are of three types. viz. hypothyroidism, hyperthyroidism and simple goitre.

• Hypothyroidism : Hypothyroidism is deficient secretion of thyroxine. This hyposecretion causes two types of disorders. viz. cretinism in children and myoxedema in adults.
• Cretinism : Hyposecretion of thyroxine in childhood causes cretinism. The symptoms of cretinism are retardation of physical and mental growth.
• Myxoedema : Deficiency of thyroxine in adults causes this disorder. It is also referred to as Gull‘s disease. Symptoms are thickening and puffiness of the skin and subcutaneous tissue particularly of face and extremities. Patients with low BMR. It also causes mental dullness. loss of memory, slow action.
• Hyperthyroidism: Excessive secretion of thyroxine causes exophthalmic goitre or Grave's disease. There is slight enlargement of thyroid gland. It increases BMR, heart rate, pulse rate and BP. Reduction in body weight due to rapid oxidation, nervousness, irritability. Peculiar symptom is exophthalmos, i.e. bulging of eyeballs with staring look and less blinking. This is caused by deposition of fats behind the eye balls in eye sockets. There is muscular weakness and loss of weight.
• Simple goitre (Iodine deficiency goitre) : Simple goitre occurs due to deficiency of iodine in diet or drinking water. Simple goitre causes enlargement of thyroid gland. Thyroid gland in an attempt to get more iodine from the blood, swells due to
• increased blood supply. Prevention of goiter can be done by administering iodized table salt. It is also called endemic goitre as it is common in hilly areas.