1.4 General Principles of Sensing Flashcards

1
Q

What are sensory receptors

A

the receive stimuli from the environment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are Neural pathways

A

that conduct information from receptors to CNS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How does sensory processing proceed

A

Transduction of stimulus energy into receptor potentials and then APs in afferent neurones
o The pattern of APs in particular neurones is a code that provides information about the stimulus
 Intensity, location and specific type of energy
o Primary areas if CNS receive input and communicate with brain for processing
 May involve reflex responses, perception, storage, etc…

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what do sensory receptors do at peripheral ends of afferent neurones

A

they transduce information about the environment into graded potentials
- these potentials initiate APs that travel to CNS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what can receptor refer to

A

either sensory or receptor proteins on their membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what are different classes of receptors

A
o Mechanoreceptors 
o Thermoreceptors 
o Photoreceptors 
o Chemoreceptors 
o Nociceptors – pain
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What does the transduction process involve

A

involves the opening and closing of ion channels

- causes a change in membrane potential and causes a graded potential called a receptor potential

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is not generated in the receptor region

A

AP

  • local current flows to a trigger zone along the axon where there are channels
  • if higher than the threshold then AP triggered
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How long does the APs fire for

A

as long as the receptor potential is sufficient

  • increase in receptor potential (RP) causes increase in firing freq of AP
  • magnitude of AP is not affected
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what controls the magnitude of RP

A

stimulus strength, rate of change of stimulus strength, temporal summation of RP and adaption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is primary sensory coding

A

Coding is the conversion of stimulus energy into a signal that conveys relevant sensory information to the CNS
o Type of energy, intensity, and location of body it affects

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

single afferent neurone

A

with all its receptor endings makes up a sensory unit

o Generally the peripheral end divides into many fine branches each terminating with a receptor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Receptive field

A

Area of body that when stimulated leads to activity in a particular neurone
o Receptive fields of defend sensory units often overlap so single activation rarely occurs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what codes stimulus type (or modality)

A

coded by the type of sensory receptor that a stimulus activates

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

are receptors of a single afferent neurone sensitive to the same or different stimulus

A

the same type of stimulus
o Adjacent sensory units may be sensitive to different modalities
o As receptive fields overlap, a single stimulus source can give rise to multiple sensations (i.e. ice cube –> touch and temperature)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what does the frequency of APs convey

A

information about the magnitude of stimulus

larger stimulus is, larger receptor potential so a higher frequency of APs

17
Q

what happens if strength of local stimulus increases

A

receptors pf adjacent branches on an afferent neurone are activated
the summation of their local currents so greater AP reference

18
Q

whats recruitment

A

the process where stronger stimuli also affect a greater area so activate similar receptors on other afferent neurones

19
Q

what are labelled lines

A

Stimulus location is coded by the site of a stimulated receptor as well as the specific neural pathway the information is received on and these pathways are labelled lines

20
Q

whats acuity

A

the degree with which one stimulus can be located and differentiated from an adjacent one
o Depends upon the amount of convergence of the input in the ascending pathways
 The greater the convergence, the lower the acuity

21
Q

what does acuity depend on

A

depends on the size of the receptive field, the density of sensory units and the amount of overlap of receptive fields

22
Q

what allows better simulus location

A

smaller receptive fields

Receptive field overlaps aid stimulus location

23
Q

why do afferent neurones respond most vigorously to stimuli applied at the centre of its receptor field

A

This is due to greater receptor density

 More receptors activated and more APs generated

24
Q

w/ regards to stimulus location, and increase in AP rate

A

due to location or intensity
 Overlap means many sensory units will trigger so neurones at periphery of stimuli fire at lower frequency than central ones
 This provides better localisation and also intensity

25
what does lateral inhibition enable
greater localisation of a stimulus iste for some sensory systems
26
when does lateral information occur
at any stage, but usually at an early stage
27
Lateral inhibition used in pathways provides...
... the most accurate localisation o In the retina to create sharp visual acuity o Skin hair movements
28
what happens to information from afferent neurones whose receptors are at the edge of a stimulus
strongly inhibited compared to information from the stimulus centre o Increases contrast between relevant and irrelevant information, thereby focussing on important messages
29
afferent sensory pathways are formed by...
chains of three of more neuronesconnected by synapses o These chains travel in bundles of parallel pathways to the CNS o Also called ascending pathways as they go up to the brain
30
where do central processes of afferent neurones enter
enter the brain or spinal cord and synapse upon many interneurons through divergence or convergence
31
sensory pathways can be specific ascending pathways that...
carry information about one stimulus modality o Go to different cortices: somatosensory, visual, auditory, olfactory (there can also be non-specific pathways)