Download Test-MID TERM (2-4-2012) Answer keys

SDV1 Second Semester
MID TERM TEST – Physiology II
2 April 2012 (Time 10:00 – 11:30 AM)
Name ……………………………….…………..
Matric No. ……………………………
PART A
Answer briefly.
1. Discuss erythropoiesis.
(7 marks)
•
All blood cells originate from the pluripotent stem cells, hemocytoblasts.
•
Again hemocytoblasts differentiate to myeloid stem cells. It further differentiates to rubriblast,
the precursor of the RBCs.
•
Rubriblast --- prorubricyte --- rubricyte --- metarubricyte --- reticulocyte --- erythrocyte
Erythropoietin from kidney
The lower O2 level in the blood entering the kidneys stimulates kidney to secret the hormone,
erythropoietin, from the kidney and it is carried to the bone marrow where it causes them to
produce
Nutrient supply
Adequate supply of corresponding nutrients (such as folic acids, vitamin B12, irons, etc.), are
necessary to sufficiently produce RBCs in the bone marrow.
2. Describe how blood clot is formed in an injured blood vessel.
(7 marks)
When blood vessels are injured platelets adhere to collagens and also other proteins in the
damaged connective tissues. Platelets releases secretory granules containing many of the coagulation
factors (proteins, calcium, serotonin, ADP, ATP); all assist or potentiate the coagulation process.
The surfaces of damaged blood vessels lose their smoothness and wettability that attract platelets
to be adhered. These activated platelets stimulate other platelets by secreting thromboxane A2 (TXA2)
to those already present, thus making platelet plug. It may be sufficient to occlude very small vessels.
For more serious or large vessel damage clot or thrombus formation, in addition to platelet
aggregation, is necessary.
A clot is relatively solid gel plug with meshed fibrins and entraps the plug. If the plug contains only
platelets - a white thrombus. If red blood cells are present - a red thrombus. Prostacyclin (PGI2)
secreted by intact undamaged endothelial cells acts to stop the growth of platelet plug.
Finally, the clot must be dissolved in order for normal blood flow to resume following tissue repair.
The dissolution of the clot occurs through the action of plasmin.
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3. What are the functions of capillaries? Answer relating to the structures.
(6 marks)
Functions -- exchange of fluid, nutrients, electrolytes, hormones, and other substances as proteins
between the blood and the interstitial fluid.
-
To serve this role, the capillary walls are very thin and have numerous minute capillary pores
(intercellular cleft) permeable to water and other small molecular substances.
-
Capillary bed – 4% of total blood volume.
-
But the vast number of capillaries provides a large total cross-sectional area that leads to slow
rate of blood flow favouring transcapillary exchange.
4. Discuss the blood brain barrier.
(7 marks)
 Unlike in other organs, endothelial cells of the capillaries in the brain have tight junctions.
 So, most substances in the blood cannot readily enter the cells of CNS.
 This limitation is k/s Blood-brain-barrier.
 Lipid soluble substances like O2 and CO2 can readily diffuse.
 Some molecules, such as glucose, needs special methods (active transport)
 Transport for most substances is provided by astrocytes which are interposed between the
CNS cells and capillaries.
Functions:
 Protects the brain from "foreign substances" in the blood that may injure the brain.
 Protects the brain from hormones and neurotransmitters in the rest of the body.
 Maintains a constant environment for the brain.
5. Describe importance of coronary circulation.
(7 marks)
- Circulation of blood in the blood vessels of the heart muscle (the myocardium)
- Normally Coronary arteries, superficial and deep, deliver oxygen-rich blood to the myocardium.
at levels appropriate to the needs of the heart muscles.
-
Relatively narrow vessels, commonly affected by atherosclerosis, or thrombosis and later
become blocked, causing angina or a heart attack.
Coronary arteries, due to the only source of blood supply to the myocardium, are regarded as
"end circulation“. Also the heart has very little redundant blood supply.
- Narrowing and/or blockage of these vessels can be so critical as the supply of blood and
oxygen to the heart slow down or stop.
-
Myocardial ischaemia – infarction – degeneration of cardiac muscles
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6. Write the characteristics of lymphatic system.
o
o
o
o
o
o
o
(7 marks)
The system has blind beginnings at lymph capillaries. These capillaries lie in the
interstitial spaces (between the cells and outside of the blood vessels).
Similar structure to blood capillaries and veins
One way system toward the heart (unidirectional flow)
No pump
Lymph flows toward the heart by

Contraction of surrounding skeletal muscles

Rhythmic contraction of smooth muscle in the lymphatic vessel walls

Pressure changes in the thoracic cavity during respiration
Largest lymphatic vessels join with the large veins just cranial to the heart
no lymph vessels in the brain (CSF)
7. Discuss the mucosa-associated lymphoid tissue (MALT)?
(7 marks)
The MALTs are lymph nodules or lymph patches located in the mucosal lining of different body
systems such as intestinal, respiratory, reproductive and urinary systems. They are also found in
lymph nodes, spleen, thymus and tonsils.
Although they are in different locations and sometimes given different names (e.g Payer’s
patches) they essentially have similar structures and functions.
They are unencapsulated aggregate of lymphoid nodules associated with the mucosa lining
and lack afferent lymphatic vessels.
They rely on the proximity of epithelial surface (to make contact with antigens and may have
crypts that increase surface area.
As these structures contain lymphocytes and macrophages, they remove microorganisms,
debris, and antigens from the digestive, respiratory tract, reproductive tract, urinary system, etc.
8. Discuss the functions of the lymphatic system.
(7 marks)
(1) Multiple interrelated functions
- removal of interstitial fluid from tissues
- absorbs and transports fatty acids and fats as chyle from the digestive system
- transports WBCs to and from the lymph nodes into the bones
(2) Body defence
Transports antigen-presenting cells (APCs), such as dendritic cells, to the lymph nodes where an
immune response is stimulated.
It is the body’s most important defence mechanism against invasion by pathogens. WBCs also
produce important immunoglobulins
(3) Filters lymph and blood.
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9. What are important cells of lymphatic system?
(7 marks)
Describe memory cells of lymphatic system.
Important cells
T Cells (T lymphocytes)
T cells mature and divide in the thymus; attack foreign cells or body cells infected by viruses.
Rresponsible for cell-mediated immunity (protection directly from living cells)
B Cells (B lymphocytes)
Responsible for antibody-mediated immunity (humoral immunity); a percentage of circulating
B lymphocytes mature into plasma cells; plasma cells produce and secrete antibodies
(immunoglobulins) which destroy antigens
NK Cells (natural killer cells)
Attack foreign cells and cells infected with viruses and cancer cells; also abnormal body cells
Memory cells
•
Some B and T cells have what is called “memory”.
•
Memory Cells have the ability to divide on short notice to produce more of all of the B and T
cells.
•
This is the basis of acquired immunity.
•
B and T cells amplified in response to antigen are reserved and circulate in lymphatic system
for years or even life.
•
If same antigen enters body again immune response will take place rapidly and without fullblown illness.
10. (a) Describe the formation of P-QRS-T complex in electrocardiographic recording.
•
(5 marks)
If negative (−ve) and positive (+ve) electrodes were placed approximately in line, it would result
in the voltmeter (i.e. the ECG machine) detecting the depolarisation wave travelling from the
SA node, across the atria, in the general direction of the +ve electrode. On the ECG recording,
all positive deflections are displayed as an upward (i.e. positive) deflection on the ECG paper,
and negative deflections are displayed downwards. The atrial depolarisation wave therefore
creates an upward excursion of the stylus on the ECG paper. When the whole of the atria
become depolarised then there is no longer an electrical potential difference and thus the
stylus returns to its idle position – referred to as the baseline. The brief upward deflection of
the stylus on the ECG paper creates the P wave, representing atrial electrical activity. The
muscle mass of the atria is fairly small and thus the electrical changes associated with
depolarisation are also small.
TheQwaves
• Initially the first part of the ventricles to depolarise is the ventricular septum, with a small
depolarisation wave that travels in a direction away from the +ve electrode. This creates a
small downward, or negative, deflection on the ECG paper – termed the Q wave.
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The Rwave
• Then the bulk of the ventricular myocardium is depolarised. This creates a depolarisation wave
that travels towards the +ve electrode. As it is a large mass of muscle tissue, it usually creates
a large deflection – this is termed the R wave.
The S wave
• Following depolarisation of the majority of the ventricles, the only remaining parts are basilar
portions. This creates a depolarisation wave that travels away from the +ve electrode and is a
small mass of tissue. Thus, this creates a small negative deflection on the while the different
parts of the QRS waveform can be identified, it is often easier to think of the whole ventricular
depolarisation waveform as the QRS complex. This will avoid any confusion over the correct
and proper naming of the different parts of the QRS complex.
The T wave
• Following complete depolarisation (and contraction) of the ventricles they then repolarise in
time for the next stimulus. This phase of repolarisation creates a potential difference across the
ventricular myocardium, until it is completely repolarised. This results in a deflection from the
baseline – termed the T wave. The T wave in dogs and cats is very variable, it can be negative
or positive or even biphasic (i.e. a bit of both). This is because repolarisation of the
myocardium in small animals is a little random, unlike in humans, for example, in which
repolarisation is very organised and always results in a positive T wave. Thus, the diagnostic
value obtainable from abnormalities in the T wave of small animals is very limited, unlike the
very useful features of abnormal T waveforms seen in humans.
(b) Mention sequence of heart sounds in animals.
(5 marks)
•
The sequence of heart sound occurrence is thus 4-1-2-3. The intensity of the third and fourth
sounds is less than that of the first and second and the complex can be described as du LUBB
DUP boo. In some horses, the third or fourth sound may be inaudible so that 1-2, 4-1-2 and 12-3 variations occur.
•
The name gallop rhythm is frequently applied when these extra sounds occur. Gallop rhythms
also occur in cattle and may be due to the occurrence of a fourth or third sound or to true
splitting of the components of the first heart sound. In sheep, goats and pigs only two heart
sounds are normally heard. The occurrence of a third or fourth heart sound in horses and cattle
is not an indication of cardiovascular abnormality, as it is in other species.
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PART B
Mark squares with “T” if the answer is true or “F” if the answer is false.
Note: there can be more than one true or one false answer in each question.
1. Carbaminohemoglobin is the HB which is bound with
T A. CO2.
F B. CO.
F C. CO2 and CO.
F D. H2O and CO2.
F E. H2O and O2.
(1 mark)
2. Diapedesis is
T A. the ability of WBCs to leave blood vessels and enter tissue space.
F B. prevention by white blood cells from entering the pathogens into the blood.
F C. the action of WBCs engulfing bacteria into their cytoplasm.
F D. a type of antigen-antibody reaction.
F E. an attack of bacteria to the tissues.
(1 mark)
3. Eosinophil counts above normal can be found when an animal
T A. has an allergic conditions.
T B. is infected with paraistes.
F C. is kept under high environmental temperature.
F D. has not fed enough food.
F E. has not been provided with ample water.
(1 mark)
4. Spleen is
T A. capable of contraction and thereby expresses RBCs into the blood vessels.
T B. the largest lymphoid organ of the body.
T C. capable of expressing RBCs into the blood vessels.
T D. the only organ organized to filter the blood.
F E. not responsible for the immune response of the body.
(1 mark)
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5. The first heart sound is caused by
F A. closure of the semilunar valves.
F B. opening of the semilunar valves.
T C. closure of the A-V valves and contraction of the ventricles.
F D. opening of the A-V valves and contraction of the atria.
F E. ventricular filling.
(1 mark)
6. Surfactant
T A. is produced by Type II alveolar cells of the lung.
T B. Is a mixture of proteins and phospholipids.
T C. reduces surface tension of the lung alveoli.
T D. protects alveoli from their collapse during expiration.
T E. has bactericidal action.
(1 mark)
7. The pig lymph node
T A. produces B memory lymphocytes as lymph nodes of other livestock animals.
T B. contains lymph nodules as in lymph nodes of other livestock animals.
T C. has lymph vessels entering from the hilus.
F D. has lymph vessels entering from the cortex.
F E. cannot produce memory cells as in other livestock animals.
(1 mark)
8. Which of the following are symptoms of shock.
T A. tachycardia
T B. cool extremities
T C. hypotension
T D. pale mucus membrane
T E. all of them
(1 mark)
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