Lecture 14- Sensory physiology

Question 1

why do we have senses? what do they accomplish?

Answer 1

information about the environment
information about ourselves

Question 2

what are 5 conscious special senses?

Answer 2

vision
hearing
taste
smell
balance

Question 3

what are 5 conscious somatic senses?

Answer 3

touch
temperature
pain
itch
proprioception (position of your body, ex. when you walk and when your joints are straight or bent)

Question 4

what are 2 unconscious somatic stimuli?

Answer 4

muscle tension
proprioception

Question 5

what are some visceral unconscious senses?

Answer 5

blood pressure
glucose
osmolarity
oxygen content of blood
CO2 content of blood

Question 6

what are the 5 general properties of sensory systems?

Answer 6

1. (modality)
2. sensory transduction converts stimuli to graded potentials
3. sensory neurons have receptive fields
4. the CNS integrates sensory information
5. properties of the stimulus are determined by coding and processing

Question 7

1. what are the two meanings of a receptor?

Answer 7

a protein that binds a ligand
a structure that detects sensory information (the one we’ll be using for this lecture)

Question 8

1. what is a modality and how is it detected?

Answer 8

when receptors are more sensitive to certain forms of energy or stimuli (ex. eyes stimulated by light)
they are detected by receptors

Question 9

1. what are the differences between simple receptors, complex receptors and special senses?

Answer 9

simple have free nerve endings
complex have the nerve ending surrounded by non-neuronal cells
special senses have a transducer cell at synapse

Question 10

1. what do simple receptors detect?

Answer 10

pH, O2, temperature

Question 11

1. what do complex receptors detect?

Answer 11

vibration and pressure

Question 12

1. what do special sense receptors detect?

Answer 12

smell, vision, taste

Question 13

2. what does the transduction process do?

Answer 13

changes the membrane potential of sensory neurons

Question 14

2. what are the 3 ways sensory neurons can experience a graded potential in transduction process?

Answer 14

chemical (ion gated channel)
mechanoreceptor, thermoreceptor gated channels (touch, temp, pressure, hearing, balance)
vision (channels modulated through second messenger pathways

Question 15

2. what is an adequate stimulus?

Answer 15

prefered type of stimulus for a receptor

Question 16

2. what is a receptor threshold?

Answer 16

minimum stimulus to activate a receptor

Question 17

2. what does it mean when theres a larger graded potential?

Answer 17

higher frequency and therefore a release of more neurotransmitters

Question 18

3. what does it mean that each sensory neuron has a receptive field?

Answer 18

specific region of sensory space in which an appropriate stimulus can drive an electrical response in a sensory neuron
ex. finger pad

Question 19

3. if the receptive field is larger what does that ential?

Answer 19

larger the receptive field is, the greater the area that it detects changes in but also less precise perception

Question 20

3. what does it mean that primary sensory neurons converge onto secondary neurons?

Answer 20

the more convergence (coming together) of primary sensory neurons onto secondary neurons the larger the receptive field and lower the acuity (strength of a sensory function)

Question 21

3. what is an example of sensory neurons having a receptive field?

Answer 21

she tries to determine whether she feels 1 or 2 pokes (stimuli) on her hand
when he touched with 2 she felt 1 therefore higher acuity
this occurs because the poke is activating two parts of the receptive fields therefore the receptive field is large

Question 22

3. areas of high acuity represent more or less convergence?

Answer 22

less

Question 23

4. where is sensory information processed

Answer 23

level of the spinal cord/ brainstem
cortex

Question 24

4. what makes sensory information travel through the spinal cord/ brainstem or the cortex?

Answer 24

spinal: unconscious perception
cortex: conscious perception

Question 25

4. with some sensory information processed in the cortex a stimulus may activate a primary sensory neuron but may not have enough intensity to surpass perceptual threshold, what is perceptual threshold?

Answer 25

level of stimulus necessary to be aware of particular sensation
ex. if youre scared of spiders and you watch a show with spiders on it, if theres some sort of breeze on your neck you might think its a spider

Question 26

what is the olfactory pathway?

Answer 26

not well developed in humans but more developed in animals
olfactory senses can stimulate information and emotions stronger and helps with memory
ex. smell nates cologne and think of him

Question 27

5. all stimuli are converted into graded potentials then action potentials but how does the CNS determine the properties of each stimulus?

Answer 27

modality of the stimulus
location of the stimulus
intensity and duration of the stimulus reflected by graded potential and action potentials

Question 28

5. specific groups of neurons within the brain are associated with specific modalities, what does that mean?

Answer 28

cant just change where our receptors are because we’ve grown up with it. we can’t just put photoreceptors on our fingertips, it will just feel like texture

Question 29

5. what is the labeled line processing?

Answer 29

each modality has its own wiring system from the receptor to higher processing centre

Question 30

5. what is the location of the stimulus? what does it depend on?

Answer 30

depends on what receptive fields are activated
determined by labelled line processing

Question 31

5. where are stimulus from adjacent areas of the body processed?

Answer 31

in adjacent areas of the brain
ex. sensory info from fingers are processed in adjacent areas

Question 32

5. what is lateral inhibition? example

Answer 32

mechanism to increase contrast between activated receptive fields and non- activated ones
ex. pin touching your skin, the main point you touch will activate the primary sensory neuron (high frequency of AP), but the neurons beside the primary will also be slightly activated (lower frequency of AP). the primary neuron will then inhibit the lateral neurons and only the primary will feel the stimulus.

Question 33

what is the difference between tonic receptors and phasic receptors?

Answer 33

tonic receptors will get a stimulus and continue to get action potentials. (will fire AP for as long as the stimulus is there)
phasic receptors will get a stimulus, get a couple action potentials then stop (even when the stimulus is still there)
ex. step in dog shit and it stinks, then after a bit you dont smell it no more even though its still there