Senses and perception

Question 1

Tactile imput what do we need to know?

Answer 1

What type of touch,
how big is it?
how long?
how often?
where? location on body

Question 2

How do we convert a stimulus into an electrical signal (action potential)?

Answer 2

down to recruitment and activation of modality- specific sensory receptors
This information is then transmitted faithfully through the nervous system to the sensory cortex through modality-specific sensory pathways

Question 3

What is a sensory nerve cell (neuron) basic function?

Answer 3

relay info from periphery into the central nervous system

Question 4

What is the structure of a sensory nerve cell (neuron)?

Answer 4

sudo unipolar feature-
cell body- axon branches into two directions- periphery-to skin (receptor endings) and CNS (synaptic endings)

Question 5

Describe a simple stimulus of a sensory nerve cell (skin receptor)

Answer 5

stimulus in periphery activates receptor endings causing a generation of electrical signal or action potential which is relayed centrally causing release of neurotransmitter from central terminal and recruitment of post synaptic targets

Question 6

what are three sensory mechanism components which have to be considered?

Answer 6

Type of receptor- modality-specific- features?
Transduction of stimulus- generate an electrical signal
coding of stimulus properties- quality, intensity, duration, location

Question 7

give the stimulus and receptor relating to 1- Touch 2-Temperature 3-Pain

Answer 7

1- mechanical, mechanoreceptor
2- thermal, thermoreceptor
3- noxious, nociceptor

Question 8

Describe free nerve endings? what are they characteristics of, do they have any speciality?

Answer 8

Nociceptors- allow us to notice painful stimuli, no known as naked they are simply “free”

Question 9

What type of receptors have particularly difficult histological components

Answer 9

mechanoreceptors- Merkle disk, hair follicle receptor, Pacinian corpuscle- tactile stimuli

Question 10

With respect to receptive field properties, each sensory neuron has a cluster of what?

Answer 10

peripheral nerve branches, each with recepetor endings

Question 11

What defines what’s known as the receptive field?

Answer 11

The distribution of these receptor endings attached to the cluster of peripheral nerve branches

Question 12

In regards to receptive fields of individual neurons what do all receptor endings share?

Answer 12

a sensory axon

Question 13

What is one factor that allows receptive fields to vary in size?

Answer 13

different body regions

Question 14

Where are you more likely to find small receptive fields and where are you likely to find large?

Answer 14

small in periphery large on the central/trunk regions

Question 15

What is two point discrimination?

Answer 15

ability to discern two seperate mechanical stimuli- can measure a spatial resolution, indication of size

Question 16

Describe temporal sequence of stimulus transduction?

Answer 16

stimulus– change in receptor membrane permeability– influx of cations— depolarisation- receptor potential—provided this is sufficient it generates an action potential

Question 17

What are two types of receptor subtypes?

Answer 17

ionotropic- faster kinetics- mechanoreceptors and chemoreceptors and G-protein coupled recptors- slower kinetics- chemoreceptors

Question 18

Give 4 coding stimulus properties

Answer 18

Quality, magnitude (intensity), Duration (timing), location

Question 19

Are all action potentials the same?

Answer 19

yes

Question 20

stimulus intensity is coded by what?

Answer 20

the number of neurons activated
different receptors have different thresholds- increase in stimulus intensity- increase in action potential frequency.

Question 21

What is stimulus duration coded in and by?

Answer 21

in real time by the duration of action potential firing

Question 22

What is sensory location coded by?

Answer 22

receptive field activated

Question 23

What gives rise to a sensory axon within a sensory nerve?

Answer 23

motor neuron

Question 24

What provides structural support and mechanical protection to the peripheral nerve fassicle?

Answer 24

epineurium

Question 25

What are the two types of axons in a peripheral nerve?

Answer 25

myelinated axon and unmyelinated axon

Question 26

What does a myelin sheath do?

Answer 26

speeds up conduction

Question 27

What axons have the largest diameter?

Answer 27

A alpha- skeletal muscle, then Abeta, then Adelta, the C

Question 28

what does the dorsal root contain?

Answer 28

centrally projecting axons of sensory neurons

Question 29

Where does the cell bodies of motor neurons originate?

Answer 29

the ventral horn of the grey matter

Question 30

What does the cell bodies of motor neurons give rise to?

Answer 30

an axon that leaves the horn via the ventral roots that is continues wtth the peripheral nerve- innovating muscle groups

Question 31

what are the three branches of the trigeminal nerve?

Answer 31

opthalmic branch of V- skin on forehead ect
maxillary branch of V- over lateral aspect of face- both sensory
mandibular branch of V- side of face, jaw skin- mixed sensory and motor

Question 32

Where is the axons of 1-The primary sensory neuron 2- secondary sensory neuron and tertiary sesnory neuron found?

Answer 32

10- most in periphery 2-cns spinal chord and brainstem 3- Thalamus cns

Question 33

Why is the body image distorted?

Answer 33

every sensory neuron is represented in the cortex however. body regions with high sensory innervation have greater cortical representation- leading to discrimination values

Question 34

Describe the pathway related to somatic mechanosensation

Answer 34

involves 3 inter connected neurons
afferent nerve relays signal throught the spinal chord, through the spinal chord (neuron 1) the axon in the brainstem targets the second order neuron the axon crosses the opposit side of body before being relayed through the brainstem up towards thalamus (neuron 2), synapse with the axon.

Question 35

What can the sensory Homunculus help us to understand?

Answer 35

which part of the brain relates to what part of the body

Question 36

What is meant by sensation?

Answer 36

The process of sensing our environment by activation of sensory receptors and associated sensory pathways

Question 37

What is meant by perception of senses?

Answer 37

the interpretation of sensory input

Question 38

what does the term stereognosis refer to?

Answer 38

The mental perception of objects referenced by touch.
invloves high degree of cortical processing- integration of info on several aspects of touch, ability to retrieve previous experiences

Question 39

what does the term proprioception (kinesthesia) mean?

Answer 39

the sense of self movement and body position.
integration of mechanosensory input, balance organs in the ear, muscle receptors/joints, mechanoreceptors, peridontal receptors

Question 40

Structure of a pain pathway?

Question 41

structure of tactile pathway?