The Sensory And Motor Elements Of The Peripheral Nervous System

Question 1

Describe A alpha fibres

Answer 1

•Alpha motor neurones – to skeletal muscle
•Group Ia sensory neurones – from muscle spindles
•Group Ib sensory neurones – from golgi tendon organs

Question 2

Describe A gamma fibres

Answer 2

Motor fibres to muscle spindles

Question 3

Describe A beta fibres

Answer 3

• Involved in the perception of touch and pressure
• Carry sensory input from mechanoreceptors

Question 4

What are the 4 different types of mechanoreceptors

Answer 4

•Meissner corpuscle
- responsible for sensitivity to light touch
•Merkel cell
- conveys information about texture, curvature, and object shape with high spatial acuity
• Pacinian corpsuscle
- believed to be responsible for the encoding of high-frequency vibration
• Ruffini ending
- detect tension deep in the skin and fascia

Question 5

Describe A delta fibres

Answer 5

•Aδ fibers are afferent fibers, nociceptors
•Convey fast pain and temperature sensation
•Synapse in laminae I and V of dorsal horn
•Free nerve endings in skin

Question 6

Describe C fibres

Answer 6

• C fibers are afferent fibers, nociceptors
• Convey slow pain and temperature sensation
• Synapse in laminae I and II of dorsal horn
• Free nerve endings in skin

Question 7

Describe C sympathetic fibres

Answer 7

• Postganglionic sympathetic fibres
• Convey impulses from autonomic ganglia to target organs

Question 8

What is sensory transduction

Answer 8

Sensory transduction is the conversion of a physical stimulus into a string of action potentials that can be interpreted by the sensory cortex

Question 9

Transduction of mechanical to action potentials in Pacinian Corpuscle

Answer 9

Question 10

Describe transduction in nociceptors

Answer 10

-Nociceptors only respond to intense stimuli that are potentially damaging
-Activation results in pain sensation
-Thermal, mechanical, chemical stimuli
-Mechanisms are highly complex and involve a wide range of receptors

Question 11

Give an example of transduction in nociceptors

Answer 11

-One example is a class of thermal receptors, known as “transient receptor potential” or TRP channels
-Each receptor can be activated by a particular temperature range

Question 12

Threshold of neuronal activation

Answer 12

Threshold:
-The threshold for discharge of an axon in response to externally applied current is inversely related to the diameter of the axon

-Large axons will have lower thresholds than smaller axons

Question 13

Mechanisms of neuromuscular transmission

Answer 13