Test 89    (physiology)

1. The effect of noradrenaline on the heart include:

a. tachycardiac

b. increased duration of the cardiac action potential

c. decreased potassium conductance of the membranes 
    of pacemaker cells

d. increased strength of cardiac contraction

e. increased concentration of free calcium in the myoplasm

Answera.T   b.F  c.F  d.T  e.T
The decreased in the potassium conductance of the 
membranes of the pacemaker cells contributes to the increase in rate of depolarization. 
Noradrenaline decreases the duration of the cardiac action potential.

2. The following are true about potassium:

a. hypokalaemia decreases the time of cardiac 
    repolarization

b. hyperkalaemia decreases cardiac contraction

c. hyperkalaemia relaxes vascular smooth muscle 

d. hyperkalaemia is seen in decreased aldosterone 
    secretion. 

e. fruits such as banana are high in potassium
 

Answera.T   b.T   c.T  d.F  e.T
Increased aldosterone secretion increases the
tubular secretion of potassium leading to hypokalaemia.

3. The following are true about aldosterone:

a. it is secreted by the adrenal medulla 

b. its secretion is stimulated by decreased blood volume

c. it stimulates active reabsorption of sodium in the distal 
    renal tubules.

d. it causes increased secretion of potassium by the distal
    renal tubules.

e. abnormal secretion occurs in Conn's syndrome.

Answera.F   b.T  c.T   d.T  e.T
Aldosterone, a mineralocortisone is secreted by the adrenal cortex.
.

4. True statements about aldosterone include:

a. secretion is mainly under the control of 
    adrenocorticotrophic (ACTH) hormone secretion

b. increases hepatic gluconeogenesis

c. its secretion is stimulated by angiotensin

d. in the kidney, mainly acts on the proximal convoluted 
    tubules

e. metabolic alkalosis occurs with over-secretion.

Answera.F  b.F  c.T  d.F   e.T
ACTH has little effect on aldosterone secretion; its secretion is controlled mainly from angiotensin. 
Unlike glucocorticoids, aldosterone is concerned mainly with electrolyte balance.
Aldosterone acts mainly on the distal convoluted tubules.
Aldosterone increases secretion of potassium by 
the renal tubules. This leads to an exit of potassium ions from the cells. To maintain electrical neutrality, 
positively charged hydrogen ions enters the cells leading to a fall in the hydrogen ions concentration in the extracellular fluid and hence alkalosis.

5. Following a major operation in a normal person, the following
    are seen:

a. fluid retention

b. decreased metabolic rate

c. potassium retention

d. decreased heart rate

e. fall in blood glucose concentration

Answera.T   b.T  c.F  d.F  e.F
Following major operation, there is an increased secretion of cortisol and adrenaline.
Cortisol causes fluid retention, increased potassium 
secretion and sodium secretion and increased blood glucose concentration.
Adrenaline increases the heart rate.

 
 

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