FUNCTIONAL ANATOMY - Peripheral Sensory Receptors

Question 1

What are the five main functional classfications of sensory receptors?

Answer 1

Mechanoreceptors
Chemoreceptors
Thermoreceptors
Photoreceptors
Nociceptors

Question 2

What is the receptive field of sensory (afferent) neurones?

Answer 2

Receptive field is a defined area of the body where sensory stimuli will activate that specific neurone

Question 3

What is lateral inhibition?

Answer 3

Lateral inhibition is the process in which sensory (afferent) neurones inhibit the activity of adjacent neurones to sharpen the localisation and pattern recognition of sensory information

Question 4

What are dermatomes?

Answer 4

Defined regions of the skin innervated by sensory (afferent) neurones from a single dorsal nerve root

Question 5

What are the five structural classifications of skin sensory receptors?

Answer 5

Free-nerve ending
Pacinian corpuscle
Ruffini corpuscle
Merkel cells
Meissners corpuscle

Question 6

Which two sensory stimuli are detected by free-nerve endings?

Answer 6

Pain
Temperature

Question 7

Why is it essential to have ‘hot’ and ‘cold’ free nerve endings to differentiate between temperatures?

Answer 7

It is essential to have ‘hot’ and ‘cold’ free nerve endings to differentiate between hot and cold temperatures as the action potential frequency is the same at 15°C and 40°C and thus without two distinct types of free nerve endings, it would be impossible to differentiate between hot and cold temperatures

Question 8

Which sensory stimulus is detected by pacinian corpuscles?

Answer 8

Local pressure

Question 9

Which sensory stimulus is detected by ruffini corpuscles?

Answer 9

Skin stretching

Question 10

Which sensory stimulus is detected by merkel cells?

Answer 10

Skin deformation

Question 11

Which modality is detected by meissners corpuscles?

Answer 11

Sideways shearing of skin

Question 12

What is sensory adaptation?

Answer 12

Adaptation is a decrease in neural response due to a continued application of a stimulus to sensory receptors

Question 13

Which sensory modality does not exhibit adaptation?

Answer 13

Pain does not exhibit adaptation

Question 14

What are centrally-projecting tracts?

Answer 14

Sensory (afferent) neuronal pathways transmitting sensory information from the periphery to the central nervous system

Question 15

What are the two main centrally-projecting tracts for sensory information from the skin?

Answer 15

Medial lemniscal system
Extralemniscal system

Question 16

What sensory information is transported by the medial lemniscal system from the skin to the central nervous system?

Answer 16

Precise sensory information such as touch and proprioception

Question 17

What sensory information is transported by the extralemniscal system from the skin to the central nervous system?

Answer 17

Sensory information such as pain and temperature

Question 18

Describe how the the medial lemniscal tranmits sensory information from the skin to the somatosensory cortex

Answer 18

The medial lemniscal system transmits sensory information through the ipsilateral dorsal funiculus of the spinal cord to the brain stem followed by relaying the sensory information through the thalamus followed by the somatosensory cortex

Question 19

Describe how the the extralemniscal tranmits sensory information from the skin to the somatosensory cortex

Answer 19

The extralemniscal system transmits sensory information through the contralateral ventro-lateral funiculi of the spinal cord to the brain stem, followed by relaying the sensory information through the thalamus followed by the somatosensory cortex

Question 20

What are the two sensory receptors found in muscle?

Answer 20

Muscle spindles
Golgi tendon organs

Question 21

What are the two components of muscle spindles?

Answer 21

Extrafusal fibres
Intrafusal fibres

Question 22

What type of LMN (efferent) fibre innervates extrafusal fibres?

Answer 22

Alpha motor fibres

Question 23

What type of LMN (efferent) fibre innervates intrafusal fibres?

Answer 23

Gamma motor fibres

Question 24

What are the two classifications of intrafusal fibres?

Answer 24

Nuclear bag intrafusal fibres
Nuclear chain intrafusal fibres

Question 25

What are the two classifications of sensory neurones which coil around intrafusal fibres?

Answer 25

Type Ia fibres
Type II fibres

Question 26

What information is transmitted by type Ia sensory fibres?

Answer 26

Information on how far and fast the muscle is stretched

Question 27

What information is transmitted by type II sensory fibres?

Answer 27

Information on how far the muscle is stretched

Question 28

Why is alpha/gamma co-activation essential for proprioception?

Answer 28

Coordinated activation of alpha and gamma motor (efferent) neurones stimulates the coordinated contraction of both extrafusal fibres and intrafusal fibres. Contraction of extrafusal fibres is responsible for generating force and movement, however this can slacken the intrafusal fibres, making coordinated contraction of both fibres essential to maintain the position of the sensory neurone wrapped around the intrafusal fibres, to maintain the sensitivity of changes in muscle length even during active contraction - allowing the muscle spindle to provide precise proprioceptive information to the central nervous system

Question 29

What is the key function of the golgi tendon organs?

Answer 29

Prevent excessive muscle tension