1. Compare the features and functions of lysosomes and peroxisomes.
Features
Lysosomes: vesicular organelles (250-750 nm), lipid
bilayer
Peroxisomes: vesicular organelles, lipid bilayer
Peroxisomes: vesicular organelles, lipid bilayer
Lysosomes: Product of Golgi apparatus
Peroxisomes: self-replicating / or from SER
Peroxisomes: self-replicating / or from SER
Lysosomes: enzymes= hydrolases, lysozyme, lysoferrin
Peroxisome enzymes: oxidases,(esp.catalase)
Peroxisome enzymes: oxidases,(esp.catalase)
Functions:
Lysosomes:
·
Intra-cellular digestive function
·
Regression of tissues
·
Autophagy
·
Bactericidal action (lysozyme, lysoferrin)
Peroxisomes: Detoxification action (enzyme oxidases)
2.
Mr.
Ali goes to a hilly area at an altitude of 10,000 feet. What will be the effect
on erythropoiesis? Explain the mechanism of this effect.
Erythropoiesis will increase because of increase in erythropoietin.
When a person is placed in an atmosphere of low oxygen,
erythropoietin begins to be formed within minutes to hours, and it reaches max
production within 24 hours. RBCs appear in the circulating blood about 5 days
later.
Mechanism: high altitude (low PO2) Ã dec. tissue oxygenation (renal
tissue hypoxia) Ã
increased tissue levels of hypoxia inducible factor-1 (HIF-1) , a transcription
factor for erythropoietin gene à inc.
erythropoietin à stimulation
of pro-erythroblasts from hematopoietic stem cells in the bone marrow à rapid development of
subsequent stages in the erythroid series
(this rapid erythropoiesis continues until the person
remains in the high altitude area or until enough RBCs are formed to compensate
for the lower partial pressure of oxygen in the high altitude area.)
3.
Mr.
Jamal developed intravascular blood clot. Explain the mechanism of this blood
clotting with the help of a sketch.
Intravascular blood clot is caused by the intrinsic
pathway (trauma to blood, caused by contact with rough surface)
Intrinsic Pathway mechanism:
diagram credits: Guyton & Hall Textbook of Medical Physiology
4.
Define
Refractory Period and its types. What is its mechanism? Give the normal value
of Absolute Refractory Period of the ventricular muscle.
Refractory period is the period during which an action potential cannot be elicited in an excitable tissue.
It has two types.
(i)
Absolute Refractory Period:
period during which a second action potential cannot be elicited even with a
very strong stimulus. (Lasts till the end of first third of repolarization
phase)
Mechanism: shortly after Na+ channels are opened to cause
depolarization, their gates are in their inactive state and cannot be re-opened
to cause another depolarization.
(ii)
Relative Refractory Period: period
during which stronger than normal
stimulus can cause a second action potential.
Mechanism: most of Na+ channel gates have changed from
their inactive (non-excitable) state to their closed (excitable) state.
Normal value of Absolute Refractory Period of ventricular
muscle is 0.25 to 0.30 second.
5.
What
is end plate potential? How is it produced? In which disease end-plate
potential is of low voltage?
End plate potential is a local positive potential produced inside the muscle fiber membrane
(causing membrane potential to rise by as much as 50 to 70 mV in the positive
direction). End plate potential is responsible for initiation of action potential in the muscle fiber.
End plate potential is produce when Ach-gated channels
open due to arrival of nerve action potential. Sudden influx of Na+ into the
muscle fiber causes the end plate potential.
Disease affecting End plate potential (EPP): In
Myasthenia Gravis, EPP is decreased.
6.
A
middle aged man riding on a bicycle was hit by a speedy car. He got multiple
injuries and fell on the ground. He was taken to emergency department of the
hospital after one hour. He was bleeding profusely from wounds. He was drowsy.
On examination, radial pulse was rapid and thread. Skin was pale, cold and
clammy. Arterial blood pressure was 70/50 mmHg.
a)
Which
type of shock was he having?
b)
Why
was radial pulse rapid and thready?
c)
Why
was skin pale, cold and clammy?
d)
Why
was arterial blood pressure low?
a) Type
of shock: Hypovolemic (Hemorrhagic) shock
b)
Radial Pulse was
rapid, because
of increased heart rate (to compensate decreased cardiac output due to
decreased blood pressure) and
thready
(weak), because of decreased blood pressure
c) Skin
was pale and cold because of generalized vasoconstriction including
vasoconstriction of cutaneous blood vessels to divert the blood towards more
important organs
d) Arterial
blood pressure was low because of decreased blood volume.
