Q 1. (a) Draw and label action potential of a nerve fiber . (3 marks)
Ans. (scanned answer picture coming soon)
Q 1. (b) Give advantages of the saltatory conduction. (2 marks)
Ans. Saltatory conduction has three advantages:
(i) First, by causing the depolarization process to jump long intervals along the axis of the nerve fiber, the mechanism increases the velocity of nerve transmission in myelinated fibers as much as 5- to 50- fold.
(ii) Second, saltatory conduction conserves energy for the axon because only the nodes depolarize, allowing perhaps 100 times less loss of ions than would otherwise be necessary, therefore requiring little metabolism for re-establishing the sodium and potassium concentration differences across the membrane after a series of nerve impulses.
(iii) Also, it allows repolarization to occur with little transfer of ions.
Q 2. A man of 30 years with complaints of severe muscle weakness and rapid onset of fatigue during voluntary actions consulted a physician. He was having drooping of eyelids. When a short acting anticholine estrase was given intravenously, marked improvement occurred.
(a) From which disease the man was suffering? (1 mark)
Ans: Myasthenia Gravis
(b) What is the pathophysiology of this disease? (3 marks)
Ans: (1) autoimmune disease in which the auto-antibodies are formed against the receptors of acetyl-choline present on muscular end-plate.
(2) Most of the receptors are destroyed rendering acetyl-choline ineffective
(3) This results in a weak end-plate potential that fails to elicit an action potential in the muscle fiber member.
(4) Consequently the muscle fails to contract properly and weakness of muscle is the observed symptom.
(c)Which drug is given in this type of patient? (1 mark)
This disease can be treated by either:
(1)Anti-choline esterases (e.g neostigmine, physostigmine)
or (2) immunosuppressants (glucocorticoids etc.)
or a combination of these two categories of drugs.
Drug of choice is neostigmine.
Q. 3. (a) Which cell organelles contain hydrolases? ( 1 mark)
Ans. Lysosomes
(b) Give features and functions of these organelles? (3 marks)
features: size, diameter, membrane bound, contain,
functions: digestion of foreign bodies, autophagy of old cell parts, regression of tissues, hydrolysis, anti-bacterial action of lysozymes and lysoferrin by oxidation of bacterial cell membrane and rendering them unable to repair their cell membrane.
(c) What is Tay-Sachs disease?
It is a lysosomal Lipid storage disease. In this disease there is an absence of lipid hydrolyzing enzymes in the lysosomes. This results in accumulation of lipids, especially in the brain tissue, leading to mental retardation.
Ans. (scanned answer picture coming soon)
Q 1. (b) Give advantages of the saltatory conduction. (2 marks)
Ans. Saltatory conduction has three advantages:
(i) First, by causing the depolarization process to jump long intervals along the axis of the nerve fiber, the mechanism increases the velocity of nerve transmission in myelinated fibers as much as 5- to 50- fold.
(ii) Second, saltatory conduction conserves energy for the axon because only the nodes depolarize, allowing perhaps 100 times less loss of ions than would otherwise be necessary, therefore requiring little metabolism for re-establishing the sodium and potassium concentration differences across the membrane after a series of nerve impulses.
(iii) Also, it allows repolarization to occur with little transfer of ions.
Q 2. A man of 30 years with complaints of severe muscle weakness and rapid onset of fatigue during voluntary actions consulted a physician. He was having drooping of eyelids. When a short acting anticholine estrase was given intravenously, marked improvement occurred.
(a) From which disease the man was suffering? (1 mark)
Ans: Myasthenia Gravis
(b) What is the pathophysiology of this disease? (3 marks)
Ans: (1) autoimmune disease in which the auto-antibodies are formed against the receptors of acetyl-choline present on muscular end-plate.
(2) Most of the receptors are destroyed rendering acetyl-choline ineffective
(3) This results in a weak end-plate potential that fails to elicit an action potential in the muscle fiber member.
(4) Consequently the muscle fails to contract properly and weakness of muscle is the observed symptom.
(c)Which drug is given in this type of patient? (1 mark)
This disease can be treated by either:
(1)Anti-choline esterases (e.g neostigmine, physostigmine)
or (2) immunosuppressants (glucocorticoids etc.)
or a combination of these two categories of drugs.
Drug of choice is neostigmine.
Q. 3. (a) Which cell organelles contain hydrolases? ( 1 mark)
Ans. Lysosomes
(b) Give features and functions of these organelles? (3 marks)
features: size, diameter, membrane bound, contain,
functions: digestion of foreign bodies, autophagy of old cell parts, regression of tissues, hydrolysis, anti-bacterial action of lysozymes and lysoferrin by oxidation of bacterial cell membrane and rendering them unable to repair their cell membrane.
(c) What is Tay-Sachs disease?
It is a lysosomal Lipid storage disease. In this disease there is an absence of lipid hydrolyzing enzymes in the lysosomes. This results in accumulation of lipids, especially in the brain tissue, leading to mental retardation.
