Physiology

Question 1

Stretch reflex

Answer 1

AKA myotatic reflex; monosynaptic reflex
Receptor: Muscle spindle
Detects: length of the muscle
Afferent : Group 1a endings & group II endings
Efferent: Alpha motor neuron
Centre for the reflex: Spinal cord
Effect: contraction of muscle due to activation of alpha motor neuron.

Question 2

Inverse stretch reflex

Answer 2

AKA Lengthening reaction; disynaptic reflex
Receptor: Golgi tendon organ
Detects: muscle tension
Afferent: Group 1b endings
Efferent: alpha motor neuron
Centre: spinal cord
Effect: Relaxation of the muscle due to inhibition of alpha motor neuron

Question 3

J receptor reflex

Answer 3

Stimulated by pulmonary edema, pulmonary congestion, hyperinflation of lungs
Receptor: Juxtapulmonary receptors
Afferent: unmyelinated vagal C fibers
Effect: apnea followed by rapid breathing, bradycardia, hypotension

Question 4

Gastrin

Answer 4

It is a peptide hormone
Produced by G cells present in the gastric antrum
• ↑ acid production & pepsin.
• ↑ gastric motility.
• Contraction of lower esophageal sphincter.
• Trophic action : Stimulates mucosal growth.
• Stimuli that increase gastrin secretion : Distension, peptides.
• Stimuli that decrease gastrin secretion : Acid, somatostatin.
• Acts via CCK B receptor.

Question 5

Bainbridge reflex

Answer 5

↑Venous return → Right Atria enlarges → stretch receptors stimulated → transmits signals via vagus nerve to medulla → sympathetic nerve stimulated → SA node activated → ↑HR.

Question 6

Bezold-Jarisch reflex

Answer 6

In MI → accumulation of serotonin → ↓HR, ↓BP