Physiology MCQs: Excitable tissue – nerve, muscle, neurotransmission, reflexes, pain

07/05/02

  1. The following pairs are correct EXCEPT
  1. Angiotensin 2 – activates phospholipase C
  2. Insulin – increases tyrosine kinase activity of cytoplasmic portions of transmembrane receptors
  3. ANP – increases cGMP in cell
  4. Acetyl choline – activates / inhibits adenyl cyclase
  5. Thyroid hormones – act to increase transcription of selected mRNAs
  1. Regarding body fluid compartments
  1. 60% of body weight is water
  2. Total blood volume is about 8% of body weight
  3. Intracellular fluid volume can be calculated by subtracting the ECF volume from the total body water
  4. Osmolality is not affected by the volume of the various solutes in solution or the temperature
  5. All of the above are true
  1. Regarding cell membranes / transport across cell membranes
  1. The Na+K+ ATPase pump has a coupling ratio of 3:2 – 3K+ into cell / 2Na+ out of cell
  2. The acetyl choline receptor is a typical voltage gated channel
  3. Calcium is transported across the membrane with sodium via a symport
  4. Active transport of sodium and potassium accounts for 33% of the energy utilised by cells
  5. Tetrodotoxin binds to chloride channels and blocks them
  1. Regarding nerve fibre types
  1. Type C fibres have preganglionic autonomic function
  2. Type B fibres are more susceptible to the effects of hypoxia than are type A or C
  3. Type A fibres have the slowest conduction velocity
  4. The smaller diameter nerve fibres have a shorter absolute refractory period compared with the larger diameter fibres
  5. The larger axons are concerned primarily with proprioception, motor function and temperature
  1. Regarding membrane potentials
  1. Decreasing the external sodium concentration decreases the size of the resting membrane potential
  2. The equilibrium potential for sodium in the nerve cells is about +60mV
  3. Decreasing the external sodium concentration decreases the size of the resting membrane potential
  4. The initial segment of a myelinated neuron has the greatest number of sodium channels/um2
  5. Chloride efflux is responsible for repolarisation in the neuron
  1. Regarding skeletal muscle
  1. The resting membrane potential of skeletal muscle is about –50 mV
  2. Myosin has a molecular weight of 70000
  3. Long muscles of the back contain mostly type 2 fibres
  4. Troponin T inhibits the interaction of myosin with actin
  5. ‘Fast” muscle fibres have twitch durations as short as 7.5 ms
  1. Visceral smooth muscle
  1. Has a stable membrane potential of –90 mV
  2. Acetyl choline decreases intestinal smooth muscle membrane potential and spikes become more frequent
  3. Progesterone decreases the membrane potential of uterine smooth muscle
  4. Is dependent on neural stimulation for contraction
  5. Increases in intracellular cAMP increase vascular smooth muscle contraction
  1. Regarding neurotransmitters
  1. Glutamate is the main inhibitory transmitter in the brain
  2. Histamine is converted to melatonin in the pineal gland
  3. Dopamine 4 receptors have greater affinity than the other dopamine receptors for clozapine
  4. Catechol – O – methytransferase is plentiful in nerve endings
  5. Muscarinic receptors are present at neuromuscular junctions and at junctions between neurons
  1. Regarding muscle spindles
  1. Each muscle spindle consists of up to 100 muscle fibres
  2. There are 4 nuclear bag fibres per spindle
  3. Flower spray endings are terminations of group 1a afferent fibres
  4. When the spindle is stretched nerves from primary endings on the nuclear chain fibres show a static response
  5. The spindles have innervation from the A alpha and B motoneurons
  1. Pain is a common ED presentation
  1. Allodynia is the phenomenon where gentle stimuli produce intense pain (breeze or touch of clothes)
  2. There are relatively few pain receptors in viscera therefore visceral pain is never particularly severe
  3. Fast pain is due to activity in the C pain fibres
  4. Thalamic syndrome is usually caused by obstruction to a branch of the middle cerebral artery
  5. Pain impulses are transmitted to the CNS via afferents which end in the ventral horn

Answers

  1. C
  2. E
  3. D
  4. A
  5. B
  6. E
  7. B
  8. C
  9. D
  10. A