Sensory module

Question 1

Afferent

Answer 1

PNS
towards

Question 2

Efferent

Answer 2

PNS
away

• somatic
• autonomic

Question 3

somatic

Answer 3

voluntary

Question 4

autonomic

Answer 4

involuntary

Question 5

3 neuron classes

Answer 5

1. afferent neurons - provide environmental info to CNS (towards)
2. interneurons
3. efferent neurons - carry instructions from CNS to effector organs (away)

Question 6

patella tendon reflex

Answer 6

• patella gets stretched when tapped
• stretch detected in muscle spindles (afferent) sends input to CNS
• information integrated by interneuron
• sends info via efferent neurons to muscles which get extended and result is a knee kick

Question 7

affarent nervous system

Answer 7

somatic

general: touch
special: vision, hearing, balance

autonomic

general: nociception (pain)
special: taste, smell

Question 8

why do we need sensory system

Answer 8

• homeostasis
• perception of the world
• motor coordination
• conscioussness

Question 9

sensory receptors

Answer 9

have low thresholds to specific stimulus types

• translate stimulus into electrical signal
  = sensory transduction

Question 10

mechanosensory ion channels

Answer 10

??

Question 11

receptor potential

Answer 11

determines the rate and pattern of action potential firing in a sensory neuron - which is what determines if that stimulus gets sent to the brain

a graded depolarisation of the membrane by the relevant stimuli

Question 12

separate receptor cell

Answer 12

example: taste bud

the pores of the taste bud detect the chemicals on food or whatever, and send signals to the sensory neurons which sends an action potentialse to the CNS

Question 13

specialised afferent ending

Answer 13

olfactory epithelium
……

Question 14

tonic receptors

Answer 14

adapt slowly or never

Question 15

phasic receptors

Answer 15

adapt rapidly

e.g. pacinis corpsucle

Question 16

univariance

Answer 16

regardless of the stimulus origin, receptors will always produce a given response type

Question 17

lateral inhibition

Answer 17

improves acuity when the receptor fields overlap

Question 18

sensory modality

Answer 18

type of sense

Question 19

receptor types

Answer 19

photoreceptors - light
chemoreceptors - chemicals
mechanoreceptors - touch
osmoreceptors - body fluids
nociceptors - pain
thermoreceptors - heat and cold

Question 20

sensory information

Answer 20

direction
location
intensity
timing

Question 21

perception

Answer 21

conscious interpretation of external world
- what we perceive not real world
e.g. illusions

Question 22

bottom-up

Answer 22

data-driven provided by photoreceptors

Question 23

top down

Answer 23

expectations supplied by the CNS are used to interpret and modify data

(or based on previous experience)
e.g, determining handwriting. one word by itself is hard but in a sentence you could see it become one

Question 24

cornea

Answer 24

• transparent
• mechanical protection (layered)
• most refractive power
• fixed focusing power
• 5 layers

Question 25

lens

Answer 25

- layered - fibres made of crystalline - transparency depends on organisation - adaptive focusing power - damage accumulates (e.g. cateracs) - focus light (via accomodation) - UV filter

Question 26

retina

Answer 26

receptor layer - where we detect photons very thin layer at the back of the eye

Question 27

rods vs cones

Answer 27

....

Question 28

fovea

Question 29

adaptation

Answer 29

pupil: - vision constriction (pupillary) - parasympathetic stimulation of circular muscle - sympathetic stimulation of radial muscle

Question 30

phototransduction cascades

Answer 30

this is for rods (process same for cones) visual pigments (opsins): 1. light photon triggers isomerisation - all-trans retinal doesn't fit binding site - opsin changes conformation - transducins are activated - PDE are activated (PDE catayses cGMP to GMP) - cGMP-gated cation channels close - hyperpolarisation closes v-gated Ca channel all these steps lead to a large amplification of the signal when this conversion happens, it closes the channels and causes the .. to hypoerpolarise

Question 31

2 different types of photoreceptors

Answer 31

rods and cones they both have synaptic terminals and an inner segment with the nucleus and mitochondria etc but specialised outer segments

Question 32

visual pigments

Answer 32

protein opsin + retinal in rods its called: rhodopsin = scotopsin + retinal retinal gives opsins their colours

Question 33

photoreceptor hyperpolarisation

Answer 33

the base of the rod is depolarised 1. cation channels continuously active 2. inner segment leaks K+ 3. phototransduction hyperpolarise the rod 4. the signal from 1 photon is above the noise cones are less sensitive but are faster and dont saturate

Question 34

walds cycle

Answer 34

note* need to regenerate cis-retinol so it can go again