Senses

Question 1

What happens when a stimulus is present?
permeability?
membrane potential?
AP?

Answer 1

stimulus, receptor, change in ionic permeability of afferent nerve endings, change in membrane potential of nerve ending, generation of AP in different nerve terminal, propagation of AP to CNS, integration of info into CNS

Question 2

All sensory receptors are..

Answer 2

transducers

Question 3

Sensory transduction route?

Answer 3

stimulus, local change in membrane permeability, ions flow across the membrane(recpetor current), receptor (generator) potential, release of NETs onto nerve, burst of AP from attached nerve

Question 4

Sensory receptors transmit 4 types of info:

Answer 4

modality (quality) - vision, hearing, taste
location - recpetive fields, projection pathways to CNS
intensity = firing frequency, low threshold fibres for weak stimuli
duration - phasic or tonic recpetors

Question 5

Can have 2 types of lateral inhibition

Answer 5

lateral inhibition pre-synaptic

lateral inhibition post-synaptic

Question 6

Convergence and divergence?

Answer 6

convergence = multiple pathways come together
divergence= pathways seperates into different directions

Question 7

Location:
Inhibitory synapses function?
3 types of inhibition?

Answer 7

prevent unrestricted spread of excitation
feedback inhibition - gain adjustment
descending inhibition - higher control (eg. block transmission to focus on other stimuli)
lateral inhibition (eg. contrast enhancement on eye)

-2 neurons can converge onto one secondary neuron(secondary neuron can’t distinguish between 2)
-lateral inhibition= activity in one neuron suppresses anothers activity (pre and post can occur)
non-specific multi-modal pathway can receive info from other modalities

Question 8

Intensity:

Answer 8

high number of neurons =changes threshold so spreads over more

Question 9

Duration:
phasic receptors?
tonic receptors?

Answer 9

phasic receptors = burst, fast adaptation
Tonic recpetors = slow adaptation eg. postural

TO remember = ‘phasic’ = quick like a teenage phase

Question 10

Receptor classification

• modality
• origin
• distribution

Answer 10

modality: mechano, thermo, chemo receptors etc
Origin:
-internorecpetors = internal organs, visceral pain
-proprioceptors = muscles,tendons, joints
- nociceptors = high threshold mechano and thermo
-exteroreceptors= vision, hearing
Distribution:
-general sense (somesthetic) touch, pressure, stretch
- special sense - head, innervated by cranial nerves

Question 11

Free nerve endings

Unencapsulated nerve endings

Answer 11

location: widespread in epithelia and connective tissues
modality: pain, heat, cold

Question 12

Hair follicles

Unencapsulated nerve endings

Answer 12

technically unencapsulated
location: widespread in epithelia
modality: varied according to type
both rapid and slowly adapting subtypes

Question 13

Tactile/ Merkel Discs

Unencapsulated nerve endings

Answer 13

location: superficial skin (epidermis)
modality: light, touch, texture
slowly adapting

Question 14

Pacinian Corpuscle (or lamellated)
(Encapsulated nerve endings)

Answer 14

location: dermis, joint capsules, viscera
modality: deep pressure, vibration, tickle
Sensitive to: 250 - 350 Hz
rapidly adapting (phasic)

Question 15

Meissner ( or tactile ) corpuscles

Encapsulated nerve endings

Answer 15

location: dermal papillae of skin (esp. palms)
modality: light, touch, texture (movement)
sensitive to: 30 - 50 Hz
rapidly adapting (phasic)

Question 16

Ruffini Corpuscles

Encapsulated nerve endings

Answer 16

location:epidermis, joint capsules, subcutaneous tissue
modality: heavy touch, pressure, joint movement
-kind of proprioceptor?
slowly adapting (tonic)

Question 17

Muscle spindles

Answer 17

= skeletal muscles near tendon, to allow muscle stretch ( proprioception)

Question 18

Golgi Tendon organs = tendons

Answer 18

tension on tendons (proprioception)

Question 19

Integration of info by CNS

Answer 19

1st order:
reticulo-spinal fibres
2nd order:
spino-thalamic
spino-reticular

(somesthetic pathways = pain)