Sensory Nerves/body sensation

Question 1

What is sensory modality?

Answer 1

That different type of stimulus are picked up by specialised receptors

Question 2

What are mechanoreceptors?

Answer 2

Sensory receptors that are stimulated by mechanical stimuli - touch stretch, pressure, deformation.
Detect many stimuli, balance hearing

Question 3

What are proprioceptors?

Answer 3

Mechanoreceptors in joints and muscles that signal information information related to body or limb position.

Question 4

What are nociceptors?

Answer 4

Respond to painful stimuli

Question 5

What is a graded membrane potential change called in a sensory nerve?

Answer 5

Receptor potential or a generator potential

Transduction always results in the opening or closing of ion channels

Question 6

When do you get a higher frequency of action potentials?

Answer 6

When there is a larger stimulus since this causes a larger receptor potential, can also activate more receptors too

Question 7

What is meant by adaptation of a mechanoreceptor?

Answer 7

When the mechanoreceptor stops producing action potentials to a maintained stimulus and only activates on a change or a novel event

Question 8

Give an example of a sensory receptor that does not adapt?

Answer 8

Nociceptor, because it is important not o ignore a painful stimuli.

Question 9

What is a pacinian corpsucle responsive to?

Answer 9

Vibration and pressure

Question 10

Describe the structure of a pacinian corpsucle

Answer 10

Myelinated nerve, naked nerve ending. The nerve ending is enclosed in a connective tissue capsule. This capsule contains layered membrane lamellae separated by fluid.

Question 11

How are action potentials generated from a pacinian corpsucle

Answer 11

Mechanical stimuli deforms the capsule and nerve ending, causing ion channels to open, - generator potential and then action potential.

Question 12

How is the pacinian corpsucle capable of rapid adaptation?

Answer 12

Fluid redistribution of corpsucle rapidly dissipates stimulus, nerve ending no longer stretched

Question 13

What happens to the pacinian corpsucle when the stimulus is withdrawn?

Answer 13

Capsule springs back - more action potentials

Question 14

What type of structure is the pacinian corpsucle?

Answer 14

Specialised Non-neural accessory structure

Question 15

What is the receptive field?

Answer 15

The area that a stimuli will activate a sensory neurone

Question 16

What does the ability to tell apart two points on the skin depend on?

Answer 16

The size of the receptive field and neuronal convergence

Question 17

What is meant by convergence?

Answer 17

When multiple presynaptic neurones synapse with fewer post synaptic neurones

Question 18

What does convergence allow?

Answer 18

Allows sub threshold stimuli to sum at the secondary neurone forming and initiating action potentials

Question 19

How can we locate a stimulus so precisely?

Answer 19

Lateral inhibition of sensory neurones that are at the edge of the stimulus and those which are close to each other but have different strength of APs (Find exact location of pin prick)

Question 20

What must depolarisation reach in sensory neuron to cause an action potential?

Answer 20

Voltage-gated sodium channels in first node of Ranvier

Question 21

Does all adaptation occur at the same speed?

Answer 21

No, some receptors and fast/moderately adapting or slow adapting

Question 22

Why do some receptors adapt?

Answer 22

Not all information is relevant, constant light pressure of back is not as important to be aware of as gaining or losing that pressure

Question 23

What is the acuity of the back and hands?

Answer 23

Back - low acuity (fails two point discrimination test due to convergence and larger receptive field
Hand - high acuity (low convergence and small receptive fields, accurate two point discrimination)

Question 24

How does sensory receptor information travel through the CNS?

Answer 24

Afferent nerve fibre synapses with interneuron which carries information up spinal cord to thalamus and somatosensory cortex

Question 25

What is the relationship between sensitivity of body area and size of somatosensory cortex section used for that area?

Answer 25

The larger the area of somatosensory cortex dedicated to that area the more sensitive it is to stimuli (more discriminatory too)