Wk4-5 SENSORY

Question 1

each vesicle contains

Answer 1

a similar amount of neurotransmitter

Question 2

amplitude of PSP is related to

Answer 2

neurotransmitter relese/ vesicle activation

Question 3

EPSP decays exponentially

Answer 3

as distance from synapse increases

passive conduction (no voltage gated channels)

Question 4

what is the membrane time constant and temporal summation efficacy

Answer 4

how quickly it leaks charge

Question 5

what is the membrane length constant and spacial summation efficacy

Answer 5

how far charge can propagate

Question 6

distal synapses produce…

Answer 6

larger EPSPs to compensate for large distance they have to travel to soma

Question 7

what is shunting inhibition

Answer 7

inhibiting current flow from soma to axon hillock using Cl IPSP.

Question 8

Axo axonal synapse regulate…

Answer 8

Ca entry into axon terminal

can cause pre synaptic inhibition

Question 9

paired pulse facilitation of Ca

Answer 9

2 APs follow each other
first release of Ca not all vesicles released
2nd release even more Ca influx
larger post synaptic change
this only occurs if Pr is low
if Pr was high vesicles would all release on first AP

Question 10

what is Pr

Answer 10

probability of vesicle release

Question 11

autoreceptor Ca regulation

Answer 11

found on pre synaptic axon terminal
monitor neurotransmitter release
negative feed back
packaging of neurotransmitters into vesicles

Question 12

metabotropic Ca regulation

Answer 12

magnification affected by cAMP.

changes in membrane resistance by channels

Question 13

astrocyte Ca regulation

Answer 13

buffer K in EC space

can absorb neurotransmitter in cleft causing modulation

Question 14

backwards conduction Ca regulation

Answer 14

AP at axon hillock back propagates to dendrites
info received from previous neuron synapse
can signal to strengthen desired synapse

Question 15

what is sensation

Answer 15

the process of encoding events and stimuli by the nervous system.

Question 16

what is perception

Answer 16

the process by which the brain interprets sensory information

Question 17

what is transduction

Answer 17

conversion between forms of energy.

a physical stimulus is transducer causing change in mpot.

Question 18

what is mullers law

Answer 18

when we perceive, our nerves are doing something known to differentiate between stimuli from different senses.

he was wrong as we now know about sensory coding

Question 19

2 types of sensory coding

Answer 19

rate codes = change rate of AP occurrence

temporal codes = no. spikes in certain time frame matters

Question 20

pupil

Answer 20

transparent membrane where light enters the eye

Question 21

iris

Answer 21

muscles that control pupil diameter

Question 22

optic nerve

Answer 22

where neurons leave the eye. has no photoreceptors

Question 23

cornea and lens

Answer 23

focus image on the retina (back of eye)

Question 24

fovea

Answer 24

region of highest acuity

most photoreceptors

Question 25

emmetropia

Answer 25

normal eye

light focus on the proper space

Question 26

myopia

Answer 26

short/near sightedness
lens is too strong or
eyeball too long = focusses before fovea from far sources

Question 27

hyperopia

Answer 27

farsightedness
lens is too weak or
eyeball too short = focusses after fovea from near sources

Question 28

2 types of photoreceptors

Answer 28

RODS
high light sensitivity
active in low light
single range of wavelength sensitvity

CONES
low light sensitvity
active in high light
3 types correspond to different wavelength ranges
blue, green, red (inc wavelength)

Question 29

describe photoreceptors mechanism

Answer 29

opsin molecules in foldings of membrane absorb light
triggers g protein cascade
cGMP to GMP
low conc of cGMP causes Na channels to close and hyperpolarisation
light on = less glutamate release
more negative mpot = less glutamate release

Question 30

describe pupillary light reflex

Answer 30

axonal projections to
pretectum, 
edinger westphad nucleus, 
ciliary ganglion, 
ciliary muscles

Question 31

convergence ratio is

Answer 31

ratio of ganglion cell to photoreceptor

Question 32

convergence ratio in peripheral retina

Answer 32

spread out cones and rods
many : 1
low spatial acuity

Question 33

convergence ratio in central retina

Answer 33

densely packed cones no rods
1 : 1
high spatial acuity

Question 34

what is a visual receptive field

Answer 34

region of visual space in which light affects a cells mpot.

Question 35

OFF/ON bipolar cells

Answer 35

OFF
shine on bipolar cell = hyper polarisation
shine on surroundings = depolarisation
ionotropic glutamate gated cation channels

ON
opposite of above
metabotropic g protein coupled reactions

Question 36

Lateral geniculate nucleus receives…

Answer 36

90% of retina projections going towards the brain. sends them to the cortex.

Question 37

what is a hemifield

Answer 37

everything left or right of your finger in vision.

left hemifield processed on right side of brain. vice versa

Question 38

what is partial decussation of the Optic nerve

Answer 38

where some fibres from left and right eye cross over. this occurs at the chiasm

Question 39

outline simple cells in primary visual cortex

Answer 39

spatially segregated on/off regions
rotation of rectangle centred on a point
receives inputs from LGN with aligned spatial fields
edges perception

Question 40

outline complex cells in primary visual cortex

Answer 40

spatially homogenous receptive fields
receptive field equivalent to 3 simple cells which have preferred orientation but slightly different spatial positions for receptors.

Question 41

what is sound

Answer 41

a pressure wave comprising of successive cycles of compression and rarefaction of air molecules.

Question 42

What frequencies can humans hear

Answer 42

20-20,000 Hz

most sensitive to 500-3000 Hz

Question 43

pinna

Answer 43

sound filter and funnel sounds to tympanic membrane

Question 44

ossicles

Answer 44

middle ear bones that connect tympanic membrane to oval window

mechanical lever giving 1.3x increase in force

Question 45

cochlea

Answer 45

fluid filled bony structure containing receptor neurons where transduction takes place

Question 46

what is the attenuation response

Answer 46

contraction of tympani and stapedius muscles, reducing movement of ossicles and amplification of loud sounds.

Question 47

inner ear mechanism

Answer 47

fluid moves in the vestibuli and tympani causing vibration of the basilar membrane.
low frequencies closer to apex.

Question 48

Perilymph and endolymph

Answer 48

perilymph: in scala vestibuli and tympani, usual ECF
endolymph: in scala media, high K, baths transfusing hair cells. causes high mpot

Question 49

outer hair cells

Answer 49

sit under tectorial membrane
stereocilia on hairs stick into the scala media.
tip link proteins connect adjacent stereocilia
deflection to the right causes cation channel opening and sound is transduced. K flow down electrical gradient, depolarisation, Ca channels neurotransmitter release.

Question 50

intramural time delay

Answer 50

compares time taken to reach each ear

uses phase locking to localise sound

Question 51

what is phase locking

Answer 51

where AP is produced at the same time of cycles

Question 52

coincidence detector neurons

Answer 52

receive inputs from left and right nerves
the coincidence detector that has both sides reach at same time is signalled, referring to a unique time difference and spatial recognition of sound.

Question 53

2 streams of visual information

Answer 53

parietal/dorsal pathway = position and motion

temporal/ventral pathway = object form and identification

Question 54

outline parasol cells

Answer 54

large soma, arbor, receptive field
project to magnocellular LGN layers
rapidly changing stimuli

Question 55

outline midget cells

Answer 55

small soma, arbor, receptive field
colour sensitive
project to parvocellular LGN layers
fine stimuli

Question 56

outline LGN structure

Answer 56

6 layers each representing a part of centralateral visual field
adjacent neurons = adjacent field
vertically down = same spatial receptive field

Question 57

types of channels in skin

Answer 57

mechanically gated cation channels = membrane tension and stretching

linking proteins = open due to another channel opening,

g protein coupled receptors

Question 58

cell bodies of neurons in skin are found in the

Answer 58

dorsal root ganglion

Question 59

4 types of mechanoreceptors

Answer 59

merkell cell (SA1)
pacinian corpuscle (RA2)
meissner corpuscle (RA1)
ruffini ending (SA2)

Question 60

Individual axons in skin are

Answer 60

only associated with 1 type of mechanoreceptor

Question 61

Receptive field depends on

Answer 61

how deep the mechanoreceptor is.

Question 62

Structure of pacinian corpuscle

Answer 62

concentri fluid filled layers of connective tissue around axon terminal.

Question 63

touch sense thresholds

Answer 63

human threshold of perception: lowest amplitude of a vibration that can be reliably detected.

neural threshold of perception: lowest stimulus intensity that reliably evokes 1 AP/cycle

Question 64

somatosensory cortex neurons stimuli response

Answer 64

6% of area 3B neurons: increased spike in response to specific point in space

majority: complex receptive fields where increased and suppressed spiking occurs. suppression allows for edges in space and time to be noticed.