sensory receptors

Question 1

all sense require 3 common steps

Answer 1

They require a physical stimulus

They all must transform the stimulus into nerve impulses
This occurs in the peripheral nervous system

They all evoke a response to the signal in the form of perception or conscious experience of sensation
This occurs in the central nervous system

Question 2

sensory receptors located

Answer 2

in the periphery

Question 3

sensory transduction

Answer 3

conversation of energy in env to electrochemical signs

Question 4

5 main senses

Answer 4

Photo receptors-sight
Chemicals- smell – olfactory transduce chemical into electrical
Taste- chemical- electrical
Touch- less specific, several receptors
Hearing- transduction – mechanical sound- electrical hair cells
Cochlea inner ear

Question 5

thermal senses

Answer 5

interbal and external neon’s with specials nerve endings rather than specific receprotsr

Question 6

pain- visercal

Answer 6

organ/internal pain

nociceptors afferent neurons

Question 7

balance and proprioception

Answer 7

Balance: Hair cells (branch of hearing system?? Simialr strucutre using mechanical stimuli
Proprioception- body parts in relation to space
Muscle spindles

Question 8

hearing

stimulus, receptor and location

Answer 8

mechanical
mechanorecprtor
cochlea

Question 9

balance (stim, recp, loc)

Answer 9

mechanical
mechanoreceptor
vestibular sys

Question 10

vision (stim, rep, loc)

Answer 10

light
photorecpeot
retina

Question 11

touch (stimulus, receptor and location)

Answer 11

mechinal
mechanorecpetor
skin

Question 12

temp ((stimulus, receptor and location)

Answer 12

mechinal
mechanoreceptor
skin

Question 13

pain (stimulus, receptor and location)

Answer 13

mechanical, thermal, chemical
nociceptor
skin, internal organs

Question 14

proprioception (stimulus, receptor and location)

Answer 14

mechanical
mechanorecpeot
muscles, tendons, joints

Question 15

olfaction (stimulus, receptor and location)

Answer 15

chemical
chemoreceptor
nasal cavity

Question 16

taste (stimulus, receptor and location)

Answer 16

chemical
chemoreceptor
tongue, pharynx, palate, epiglottis

Question 17

cascade

Answer 17

1) stimulis
2) sensory receptor activated
3)membrane permeability altered in sensory cell
4) a receptor potneial developes
((5)) neurotransmitter is released onto afferent neuron terminals
6)an action potent is generated in afferent neurone terminal
7)AP propagates to CNS
8) info integrated by CNS

Question 18

what is different about the cascade for touch receptors

Answer 18

misses out the neurotransmitter part because
receptor potential causes action potential in afferent nerve terminal directly because the sensory cell and th afferent nerve are the same thing

Question 19

graded potentials in sensory receptors

Answer 19

Activation: g protein

Membrane – more permeable to cations –makes more positive

‘receptor potential’ = a graded potential

All sensory receptors always initially use a graded potential

Tends to be glutamate released to generate AP

Question 20

difference between graded and action potentials

Answer 20

Graded receptor potentials increase in size in response to increases in stimulus amplitude
Action potentials are always the same size, but have a threshold for activation

graded:
The input is directly related to the size of the stimulus
Propagates slightly long the axon to the area where AP are generate
If the GP is big enough it will cause an AP
AP uses frequency to indicate stimulus size

Question 21

example of cascade including synapse: taste receptors

Answer 21

stimulus is chemical (e.g. Na in salt)

membrane depolarises in a graded response

voltgage gated ca+ channaled open allowing calcium influx

synaptic vesical fusion triggers

releasing neurotransmitter

afferent nuron depolarised

Question 22

example of cascade with direct activation= olfactory receptors

Answer 22

stimulis is chemical (odorant)

local changes in membrane permeability cause a graded receptor potential within a receptor cilium

large enough receptor potential cause depolarisation in the cell soma
triggering action potentials that travel along the olfactory nerve

Question 23

if sensory receptor is a neuron itself

Answer 23

G protein coupled receptor

Question 24

sensory receptors convey 4 types of info about stimulus

Answer 24

modality
location
intensity
timing

Question 25

modality is determined by

Answer 25

the type of energy transmitted by the stimulus and the receptors that are specialised to detect that energy

Question 26

labelled line code

Answer 26

• the receptor is selective for one type of stimulus energy
• the axons of the receptor/associated afferent neutron acts as a modality specific line of communication
• axons from these neurones make connections with specific areas in the CNS

Question 27

synesthesia

Answer 27

the labelled line code is faulty

Question 28

receptive fields in somatic system

Answer 28

region of skin innervated by the terminals of the receptor neuron

Question 29

receptive fields int he visual system

Answer 29

the receptive field of a photoreceptor is the region of the visual field projected onto that receptor

not every single bit of light will activate all photoreceptors

depends which patches of photorecptors are activated in the retina

Question 30

receptive field in the auditory system

Answer 30

arrangement of receptors enables frequency discrimination

can’t compute stimulus location just in the cochlea

different frequencies along cochlea length and location is actually registered downstream of the cochlea in the brainstem

Question 31

overlapping receptive fields

Answer 31

bigger stimulus

activates multiple neurones stimulated

1 receptor=1 neuron

Question 32

stimulus intensity

Answer 32

total amount of stimulus energy delivered to the receptor

Question 33

sensory threshold

Answer 33

the lowest stimulus strength that can bed detected

Question 34

intensity is determined by

Answer 34

resposne amplitude of the receptor and this the ring frequency of the afferent neurones

more intense stimulus also activates more receptors

Weak stimulus intensities activate low threshold fibres
Strong stimulus intensities activate high threshold fibres

Question 35

onset timing determined

Answer 35

when the stimulus energy is received by the receptor and causes it to fire

Question 36

stimulus duration is determined by

Answer 36

adaptation rates of receptors

Adaptation = In response to continuous stimuli, the firing rate of action potentials decreases

Question 37

slowly adapting receptors

Answer 37

tonic receptors

respond to prolonged stimulation

Question 38

rapidly adapting receptors

Answer 38

phasic receptors

response at the beginning and end of a stimulus

Question 39

divergence

Answer 39

allows primary afferent neurones to signal to more than one relay neuron

Question 40

convergence

Answer 40

ensures that relay neurons have larger receptive fields than primary afferent neurones

Convergence point is receiving information across both receptive fields

Question 41

inhibitory neurons

Answer 41

ensures the single in the most active neutron is portage e.g this enables contrast enhancement in the eye

Question 42

how is stimulus intensity encoded in sensory system1

Answer 42

the frequency of action potential firing

Question 43

stimulus intensity

Answer 43

Stimulus intensity is the total amount of stimulus energy delivered to a receptor, e.g. a louder sound has a greater stimulus intensity than a quieter sound

Question 44

what is special about the olfactory receptor cells?

Answer 44

they are the sensory cell and the afferent neurone
so the graded receptor potential will initiate action potential firing IF the graded receptor potential takes the membrane potential above the threshold for action potential firing

If the stimulus is larger, the graded receptor potential will be larger, this will keep the cell above the threshold for action potential firing for longer and will result in more action potentials being produced i.e. the frequency of action potential firing will increase

Question 45

an increase in a graded receptor potential size will

Answer 45

NOT increase the amplitude of the action potential produced

Question 46

sensory cell separate to primary afferent neuron

Answer 46

taste and hair cells e.g.

greater stimulus intuit would cause larger graded receptor potential in the sensory cell which would result in more neurotransmitter being released from the sensory cell onto the primary afferent neuron

More neurotransmitter would activate more receptors on the afferent neuron, creating a larger excitatory post-synaptic potential (EPSP) in the afferent neuron. The larger EPSP would have the same effect as a larger graded receptor potential and would keep the afferent neuron above the threshold for firing an action potential for longer, resulting in a greater frequency of action potential firing.