Receptors and Function

Question 1

Where is somatosensation?

Answer 1

All over the body

Question 2

What does the somatosensory system do?

Answer 2

Tells us what the body is up to and what is going on in the environment, by providing bodily sensations - touch, temperature, pain, position in space
allows us to distinguish between what the world does to us and what we do to it - closer relationship with movement than the other senses

Question 3

Where are the receptors?

Answer 3

All over: skin, muscles, tendons, joints

Question 4

What does increased receptors mean?

Answer 4

Increased sensitivity to stimulation than areas with relatively fewer receptors (hands, lips)

Question 5

What is sensitivity to different somatosensory stimuli due too?

Answer 5

Having different kinds of receptors - encodes different stimuli

Question 6

What is the skin?

Answer 6

The largest sensory organ, humans have two kinds of skin

Question 7

What are the two kinds of skin?

Answer 7

Hairy skin (such as on back of hand, don’t touch things) - low sensitivity

Glabrous skin (palms) - skin doesn’t have hair follicles but contains larger numbers of sensory receptors than other skin areas (such as hands, feet, lips). Sensitive to a wide range of stimuli - due to needing to explore world with these parts

Question 8

Why have we evolved to have two skin types?

Answer 8

So that we have useful resources allocated where we need, depending on what we are doing e.g. no hair on back of hands as don’t use them

Question 9

What is the two point discrimination test?

Answer 9

Have a cumpus, with 2 points on, see if you can discrminate between them
reveals differences in skin sensitivity across the body
fingertips are most sensitive - high density of receptors, with small fields, the brain devotes a lot of resources
brain devotes less resources to less sensitive places as don’t use them
back - can’t distinguish the two points

Question 10

What are the three types of somatosensory perception?

Answer 10

Nocioception
Hapsis
Proprioception

Question 11

What are nocioception receptors for?

Answer 11

Perception of pain and temperature e.g. pin prick from a needle

Question 12

What are hapsis receptors for?

Answer 12

Perception of fine ouch and pressure, e.g. grasping a beer

Question 13

What are proprioception receptors for?

Answer 13

Perception of the location and movement of the body e.g. stretching

Question 14

What do nociception receptors consist of?

Answer 14

Free nerve endings - which is where pain is detected
If there is sharp pain or heat, there is a chemical response
Damage to dendrite or surrounding cells release chemicals that stimulate dendrite and produces an AP
It is either damage to the free nerve endings or chemical release which stimulates these receptors
When AP occurs, transmitted to spinal cord

Question 15

What hapsis receptors consist of?

Answer 15

These receptors are attached to hair, connective tissue or dendrite - all over the body
They have lots of functions: distinguishes touch, pull, vibration
Commanility: it is mechanical stimulation (pulling, pushing) which triggers an AP in these neurons containing the haptic receptors
The composition of the capsule determines the type of mechanical energy conducted

Question 16

What do proprioception receptors consist of?

Answer 16

3 types of body awareness, which tell you when things are occurring
muscle spindles - muscle stretch
Golgi tendon organs - tendon stretch
joint receptors - joint movement
Movement stretch the receptors to mechanically stimulate dendrites and produces an AP

Question 17

What does ibruprofen do?

Answer 17

Blocks prostaglandin synthesis - so there is less of an inflammatory response, can tolerate more pain

Question 18

Where are neoreceptors not found?

Answer 18

In the CNS

Question 19

What is the difference between the 3 receptors in terms of how they elicit action potentials?

Answer 19

Nocioception - damage to dendrite release chemicals that stimulate dendrite and produces an AP
Hapsis - mechanical stimulation elicits an AP
Proprioception - when you stretch, stimulate the dendrites producing an AP

Question 20

What is the difference between the surface and then the deeper end of haptic receptors?

Answer 20

Surface - light touch, detects changes
Deeper - detect deeper pressure, receptors respond to deep touch
They all send info to the spinal cord

Question 21

What do somatosensory receptors tell you?

Answer 21

2 things about a sensory event: when it occurs and whether it is still occurring

Question 22

What are the two categories of receptors?

Answer 22

Rapidly adapting receptor - body sensory receptor which responds briefly to the beginning of a stimulus and the end of a stimulus on a body, not during

Slowly adapting receptor - body sensory receptor that responds as long as a sensory stimulus is on the body, respond the whole time

Question 23

What does adaptation mean?

Answer 23

Changes in the way the receptor fires based on how long the stimulus is on there for

Question 24

What type of adaption receptors do the sensations have?

Answer 24

Nocioception (pain and temperature) - very slow, signals the presence of a long sustained stimulus (makes sense, don’t want pain to stop immediately)

Hapsis (fine touch and pressure) - mixed types of adaption

Proprioception (body awareness) - both types

Question 25

What is good about the rapid receptor?

Answer 25

Motions of objects on the skin, gives good responses to repeated stimuli - for example, fish nibbling, coming back and forth, get the detection on and off

Question 26

Where does all of the information go through?

Answer 26

Dorsal route ganglion neurons - transmit information from the body to the spinal cord
if the cell bodies in spinal cord - ganglion cells
central nervous system - nuclei

Question 27

What are dorsal route ganglion neurons?

Answer 27

Dendrite and axon are continuous, carry sensory info from the skin to the CNS via the spinal cord. Tip of the dendrite is responsive to sensory info. Each spinal cord segment has one dorsal route ganglion on each side that contains many dorsal root ganglion neurons. In the spinal cord, the axons of these neurons may synapse onto other neurosn or continue to the brain

Contains cell bodies of sensory neurons that bring information from the periphery to the spinal cord

Question 28

What are the difference in the axons of the 3 perception receptors?

Answer 28

Propioceptive and haptic neurons - carry information about location and movement, and touch and pressure, fast. Have large, well myelinated axons, so the info goes through very quickly

Nociceptive neurons - pain and temperature information, there are small axons with little or no myelination, pain is slow, just remains there (like a toothache)

Question 29

What is deafferentiation?

Answer 29

This is when there is damage to axons or sensory fibres or loss of input to a structure - these leads to loss of incoming sensory input

Question 30

What is the consequence of deafferentiation?

Answer 30

Patient G O lost sensation due to peripheral neuropathy after influenza
Didn’t lose motor control but simple actions for prolonged periods would require visual feedback. Could not perform many daily tasks
Afferent feedback is required for fine movements