Medical Physiology MCQ and Answers

1. The process through which cells develop different characteristics in structure and function is called:
a. specialization
b. maturation
c. differentiation
d. hybridization
e. clonal expansion
Answer: Differentiation
• Differentiation and stem cells
 As an individual unit, the cell is capable of metabolizing its own nutrients, synthesizing many types of molecules, providing its own energy, and replicating itself in order to produce succeeding generations.
 In a multicellular organism, cells become specialized to perform different functions through the process of differentiation.
 Most types of animal cells differentiate at an early stage – they become specialized for a particular function and cannot change into different types of cell
 Stem cells can be made to differentiate to form different types of cell, such as nerve cells.

2. Jejunal mucosal cells are similar to proximal convoluted tubular cells in that both
A. Absorb glucose by a process linked with sodium absorption.
B. Absorb chloride ions actively.
C. Absorb amino acids actively.
D. Are rich in mitochondria.
E. Possess microvilli on their luminal border.
A. True – In both cases, glucose absorption is blocked by phlorhizin.
B. False – In both, these follow passively the absorption of sodium.
C. True – Again the process requires active absorption of sodium.
D. True – Both expend considerable energy.
E. True – The two types of cell have very similar functions.

3. During intrauterine life, formation of red blood cells begins in:
a. Mesoderm of yolk sac
b. Bone marrow
c. Spleen
d. Liver
e. Lymph nodes
Correct answer: (a) Mesoderm of yolk sac
• During intrauterine development, erythrocytes are produced FIRST by the mesoderm of yolk sac and then by the developing spleen during the third month of gestation, until the bone marrow is formed in the seventh month and takes over erythrocyte production exclusively

4. The white blood cells having receptors for IgE on their membranes are:
a. Neutrophils
b. Eosinophils
c. Basophils
d. Lymphocytes
e. Monocytes
Correct answer: (c) Basophils
• Immunoglobulin E (IgE) is a type of antibody found in mammals.
• IgE is synthesized by plasma cells.
• IgE also has an essential role in type I hypersensitivity.
• IgE primes the IgE-mediated allergic response by binding to Fc receptors found on the surface of BASOPHILS and mast cells.

5. In a patient having first degree atrioventricular block, the ECG shows prolonged:
a. QT interval
b. QRS interval
c. PR interval
d. RR interval
e. VAT (ventricular activation time)
Correct answer: (c) PR interval is prolonged during first-degree atrioventricular block
• First-degree AV block manifests as fixed prolonged PR interval (>0.20 sec); PR interval can be as long as 0.60 sec
• Can also be found in normal persons with:
o Increased vagal tone,
o Medications such as (digoxin, Ca++ Channel blockers, Beta blockers), and
o Occasional ischemia
• Patients are asymptomatic; no treatment required

6. Normally about 65% of the total blood volume is present in:
a) Veins
b) Arteries
c) Arteriovenous anastomes
d) Arterioles
e) Capillaries
Correct answer: (a) Veins
• Veins are also called capacitance vessels or blood reservoirs because they can hold up to 65% of the body’s blood supply at any time.
• Veins have thinner walls that easily expand to hold large amounts of blood
• Systemic arteries and arterioles hold about 15% of blood volume in body
• Capillaries hold about 5 % of blood volume in the body

7. Which one of the following effects would occur if the blood flow in the hypophyseal portal system is interrupted
a. Direct inhibition of the milk ejection reflex
b. Stimulation of cortisol production
c. Stimulation of thyroid hormone production
d. Suppression of ovulation
e. Decreased water reabsorption in the collecting ducts
Ans. (d)
a. This statement applies to oxytocin, which does not pass through the hypophyseal portal vessels.
b. Cortisol secretion would drop
c. Thyroid hormone production would drop
d. GnRH must pass through the hypophyseal portal vessels to reach the anterior pituitary where it stimulates release of LH and FSH. FSH stimulates the ovarian follicles to develop then LH stimulates ovulation. Therefore, interruption of the hypophyseal portal vessels would suppress ovulation.
e. Wrong. This statement applies to vasopressin, which does not pass through the hypophyseal portal vessels.

8. In the small intestine
A. The enzyme concentration in intestinal juice is lower in the ileum than in the jejunum.
B. Vitamin B12 is absorbed mainly in the jejunum.
C. Water absorption is dependent on the active absorption of sodium and glucose.
D. Absorption of calcium occurs mainly in the terminal ileum.
E. Glucose absorption is dependent on sodium absorption.
A. True – Being proteins, enzymes are digested by proteolytic enzymes as they pass down the gut.
B. False – It is absorbed mainly in the terminal ileum.
C. True – Water is absorbed passively down the osmotic gradient set up by active sodium and glucose absorption.
D. False – It occurs mainly in the duodenum.
E. True – Sodium is required at the luminal surface for glucose to be absorbed by an active carrier-mediated process.

9. The cells of the liver
A. Help to maintain the normal blood glucose level.
B. Deaminate amino acids to form NH4, which is excreted as ammonium salts in the urine.
C. Synthesize Vitamin D3 (cholecalciferol)
D. Manufacture most of the immune globulins.
E. Inactivate steroid hormones manufactured in the gonads.
A. True – When blood glucose falls, liver glycogen is broken down to form glucose; when glucose levels rise above normal, glucose is taken up by the liver and stored as liver glycogen.
B. False – The NH4 is converted into urea and excreted in the urine; NH4 is toxic.
C. False – Cholecalciferol in produced in skin by the action of sunlight; the liver converts it to 25-hydroxycholecalciferol and the kidney completes its activation by further hydroxylation.
D. False – They manufacture most of the plasma proteins but lymphocytes manufacture immune globulins.
E. True – The failure to inactivate estrogens in men with liver failure can lead to breast enlargement.

10. In normal healthy people, urinary
A. Specific gravity ranges from 1.010–1.020.
B. Osmolality ranges from 200–400 mosmol/liter.
C. Color is due to small quantities of bile pigments.
D. pH falls as dietary protein rises.
E. Calcium excretion is increased by parathormone.
A. False – It may range from 1.004 to 1.040.
B. False – It may range from 100 to 1000 mosmol/liter.
C. False – It is due to ‘urochrome’, a pigment of uncertain origin.
D. True – Dietary proteins lead to acid residues such as sulphates and phosphates.
E. True – More calcium is filtered due to the raised blood level, so more is excreted.

11. Aldosterone secretion tends to raise the volume of
A. Plasma.
B. Interstitial fluid
C. Intracellular fluid
D. Urine
E. Cerebrospinal fluid
A. True – By retention of sodium chloride and water in the extracellular fluid compartment
B. True – This, like plasma, is a sub-compartment of the extracellular fluid.
C. False – The sodium chloride/water retention is confined to the extracellular compartment.
D. False – It reduces it by retaining salt and water.
E. False – CSF is a secretion classified as transcellular fluid; it is not a sub-compartment of ECF.

12. Stimulation of the vagus nerves causes
A. A reduction in the strength of ventricular contraction
B. Secretion and vasodilatation in the salivary glands
C. Mucous secretion from bronchial mucosal cells
D. The spleen to contract
E. The gallbladder to contract
A. False – Ventricles have little vagal innervation.
B. False – The vagus does not supply parasympathetic nerves to the salivary glands.
C. True – It also contracts bronchial smooth muscle.
D. False – It is sympathetic activity that causes the spleen to contract.
E. True – This together with relaxation of the sphincter of Oddi drives bile into the duodenum.

13. Generalized sympathetic activity is characterized by
A. Contraction of the radial muscle in the iris
B. Increased urinary excretion of catecholamines.
C. Lipolysis in adipose tissue
D. Decreased conduction rate in the atrio-ventricular bundle
E. Relaxation of sphincteric smooth muscle in the alimentary tract
A. True – This dilates the pupil.
B. True – Derived from activity in the adrenal medulla and sympathetic nerve endings.
C. True – This provides fatty acids for energy production.
D. False – It increases and the PR interval shortens; higher heart rates are made possible.
E. False – Sympathetic activity inhibits most smooth muscle in gut but contracts the sphincters.

14. The severity of an obstructive airways disease is indicated by the degree of change in the
A. Total ventilation/perfusion ratio
B. Peak expiratory flow rate
C. Respiratory quotient
D. Tidal volume
E. Work of breathing
A. False – It may well be normal.
B. True – It is a sensitive indicator.
C. False – RQ is related to the mixture of substrates being metabolized.
D. False – This also may be normal.
E. True – This is related to the increased airway resistance.

15. Which of the following statements regarding the respiratory system are true? [Select all that apply]
a) Half the cardiac output passes through the lungs
b) In an upright man, pulmonary blood flow is greatest at the apex of the lung
c) The lungs inactivate all circulating vasoactive materials
d) In a healthy lung, the distance between the alveolar air and the blood in the pulmonary capillaries is less than 1μm
e) The vital capacity is equal to the total lung capacity
f) At the functional residual volume, the elastic recoil of the lungs is balanced by the elastic forces tending to expand the chest
d) In a healthy lung, the distance between the alveolar air and the blood in the pulmonary capillaries is less than 1μm
f) At the functional residual volume, the elastic recoil of the lungs is balanced by the elastic forces tending to expand the chest
The measured cardiac output is the output of the left ventricle. As the pulmonary and systemic circulations are in series all the cardiac output passes through the lungs (around 5 liters min-1 at rest). In an upright man, pulmonary blood flow is greatest at the base of the lung. Although the lungs inactivate many vasoactive materials, they convert angiotensin I to angiotensin II which is a potent vasoconstrictor. The total lung capacity is equal to the vital capacity plus the residual volume.

16. Fertilization of the human ovum normally [Select all that apply]
a. Occurs in the uterus
b. Prevents further spermatozoa from entering the ovum
c. Occurs 2–5 days after ovulation
d. Occurs 5–7 days before implantation
e. Leads to the secretion of human chorionic gonadotropin (hCG) within two weeks
A – False – It occurs in the outer third of the uterine tube
B – True – The zona pellucida becomes impermeable
C – False – The ovum remains viable for only about a day
D – True – During this time, the fertilized ovum travels along the uterine tube and spends several days free in the uterus.
E – True – This is necessary to maintain ovarian hormone production whose withdrawal causes endometrial necrosis

17. Secretion of testosterone [Select all that apply]
a. Depresses pituitary secretion of LH
b. Causes the epiphyses of long bones to unite
c. May lead to a negative nitrogen balance
d. Stimulates growth of scalp hair
e. Stimulates growth of body hair
A. True – This negative feedback keeps blood testosterone constant.
B. True – Sexual precocity can cause short stature.
C. False – Testosterone is anabolic and leads to skeletal muscle hypertrophy.
D. False – Scalp hair tends to recede.
E. True – This is a male secondary sexual characteristic

18. Poor balance is more likely when there is
A. Semicircular canal rather than cochlear damage
B. Impairment of basilar rather than carotid artery blood flow
C. Spinothalamic tract rather than posterior column damage
D. Dim rather than bright light
E. Recent rather than long-standing destruction of one labyrinth
A. True – The cochlea does not contribute sensory information needed for balance.
B. True – The basilar artery supplies brain stem areas particularly concerned with balance.
C. False – The posterior columns transmit proprioceptive information needed for balance.
D. True – Vision can compensate for loss of proprioception.
E. True – Abrupt loss of input causes severe disturbance followed by gradual adaptation.

19. In someone with short-sightedness (myopia)
A. The eye tends to be longer than average from lens to retina.
B. A convex lens is required to correct the refractive error.
C. Close vision is affected more than distance vision.
D. The near-point is farther than normal from the eye.
E. A circular object tends to appear oval.
A. True – Hence distant objects are focused in front of the retina.
B. False – A concave lens is required.
C. False – It is distant objects that appear out of focus
D. False – Myopic people can focus on objects closer to the eye than normal people
E. False – This is caused by an asymmetrical cornea (astigmatism)

20. A feeling of anxiety before a sporting event may be associated with an increase in
A. Heart rate
B. Parasympathetic activity
C. Beta adrenoceptor blockade
D. Circulating levels of adrenaline
E. Resting respiratory rate
A. True – An increased heart rate is a feature of increased sympathetic drive.
B. False – This tends to produce a relaxed, drowsy state as after a large meal.
C. False – Beta blocking drugs reduce the tachycardia and tremor, which exacerbate anxiety.
D. True – This produces tachycardia and tremor.
E. True – This is another physical correlate of anxiety.

21. Concerning metabolism during exercise:
a) Fats are the main source of energy during exercise.
b) The contribution made by anaerobic exercise increases during prolonged exercise
c) Carbohydrates provide the main source of energy in exercise.
d) Plasma glucose falls significantly during a period of exercise at half the maximal rate lasting for 2 hours.
c) Carbohydrates provide the main source of energy in exercise.
Carbohydrates are the main source of energy during exercise but plasma glucose changes very little unless the exercise is exceptionally severe and prolonged. The contribution made by anaerobic exercise decreases during prolonged exercise.

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