Question

For each effect of pregnancy A–E, select the most appropriate option from the following list of physiological terms. 

1. Smooth muscle relaxation. 

2. Smooth muscle constriction. 

3. Brainstem reflex. 

4. Sacral spinal cord reflex. 

5. Decreased metabolic rate.

6. Increased metabolic rate. 

A. The pregnant woman feels excessively hot in quite cool conditions; she dresses more lightly than most people and is keen to have windows opened for ventilation. 

B. The pregnant woman has suffered several episodes of urinary frequency with a burning sensation on passing urine; this has been attributed to urinary infection, from which she has not previously suffered. 

C. The pregnant woman suffers frequently from a burning sensation referred to the mid line of the chest; she didn’t have it before pregnancy, it is not related to taking exercise, but indigestion tablets seem to help. 

D. The woman in early pregnancy feels severely nauseated and quite frequently vomits, particularly first thing after getting up. 

E. Despite eating more than usual, the pregnant woman suffers from decreased frequency and difficulty in defaecation.

Answer 1

A. Option 6 Increased metabolic rate. These symptoms are like those of hyperthyroidism; in both cases the resting metabolic rate is increased; this leads to a parallel increase in heat production, so a cooler environment is needed for thermoneutrality. 

B. Option 1 Smooth muscle relaxation. The hormones of pregnancy induce smooth muscle relaxation in many parts of the body; loss of tone in the bladder hinders complete emptying and favours reflux into the ureters; the urinary stasis favours infection. 

C. Option 1 Smooth muscle relaxation. This time the muscle involved is the cardiac sphincter; loss of tone favours reflux of acid from the stomach into the oesophagus where the very low pH causes burning pain – ‘heartburn of pregnancy’. 

D. Option 3 Brainstem reflex. ‘Morning sickness’ is a classical sign of early pregnancy; the vomiting reflex is stimulated, possibly by the sudden change in hormonal levels, sharp rise in chorionic gonadotrophin, and rises in oestrogen and progesterone. 

E. Option 1 Smooth muscle relaxation. Again this is the problem, this time affecting the lower bowel so that emptying of the rectum is inefficient.