5.1.3 Neuronal Communication

Question 1

what does the sensory neurone do

Answer 1

carry electrical messages from sensory receptors to CNS

Question 2

what does motor neurone do

Answer 2

carry action potential from CNS to effector such as muscle/gland

Question 3

what does relay neurone do

Answer 3

connect sensory and motor neurones - interneurones

Question 4

what do interneurones do

Answer 4

carry info between other neurones only found in the brain and spinal cord

Question 5

cell body

Answer 5

round, centrally located structure
contain DNA
controls protein manufacturing
directs metabolism
no role in neural signalling

Question 6

dendrites

Answer 6

info collectors from CNS
recieve inputs from neighbouring neurones- relay
input may be thousands

Question 7

dendritic growth

Answer 7

new dendrites can growth
provides room for more connections to other neurones
new connection are basis for learning
mature neurones generally can’t divide

Question 8

axon

Answer 8

cells output structure
1 axon per cell - 2 distinct parts
tube-like structure branches at end that connect to dendrites of others

Question 9

myelin sheath

Answer 9

act as electrical insulators
not present on all cells - presnt in motor and sensory neurones
made of schwann cells

Question 10

schwann cells

Answer 10

type of lipid

Question 11

which neurones can conduct impulses faster

Answer 11

myelinated neurones

Question 12

where are chemoreceptors found

Answer 12

taste buds and aortic and cartoid bodies

Question 13

what energy is detected by chemoreceptors

Answer 13

chemical stimuli in environment or blood

Question 14

where are photoreceptors found

Answer 14

rods and cones in retina of eye

Question 15

what energy is detected by photoreceptors

Answer 15

detect changes in light

Question 16

where are thermoreceptors found

Answer 16

skin
hypothalmus

Question 17

what energy is detected by thermoreceptors

Answer 17

changes in heat

Question 18

where are mechanoreceptors found

Answer 18

touch and pressure receptors
inner ear

Question 19

what energy is detected by mechanoreceptors

Answer 19

mechanical deformation of receptor cell membrane

Question 20

where are nocioreceptors found

Answer 20

internal and external

Question 21

what energy is detected by nocioreceptors

Answer 21

pain receptors
higher threshold for activate than do other receptors
need more intense stimulus required to activate

Question 22

where are propioreceptors found

Answer 22

muscle spindles
golgi endon
joint receptors

Question 23

what energy is detected by propioreceptors

Answer 23

sense of body position and allow fine control of skeletal movements

Question 24

what does pacini corpuscle detect

Answer 24

pressure changes

Question 25

examples of internal enviroment

Answer 25

blood glucose conc internal temperature water potential cell pH

Question 26

external enviroment

Answer 26

humidity external temperature light intensity new or sudden sound

Question 27

Depolarisation ion movenment

Answer 27

pottasium gates close sodium gates open sodium ions move into cell by diffusion voltage gated sodium ions open inside of neurone becomes less negative

Question 28

Resting potential ion movenment

Answer 28

sodium poattasium pumps open 3 Na go out and 2 K ions go in the inside of neurone is more negative charged

Question 29

Repolarisation and hyperpolarisation ion movement

Answer 29

K+ move out of cell K+ channels open Na+ channels close inside neurone is more negatively charged

Question 30

Back to resting potential ion movenment

Answer 30

Na+ closed K+ closed sodium pottasium pump open 3 Na+ out 2K+ in

Question 31

Action potential

Answer 31

occurs when a nerone sends info down an axon when stimulated membrane potential is briefely depolarised stimulus causes membrane at one part of neurone to increase in permeability to Na+

Question 32

peak of action potential

Answer 32

once action potential of +40 mV has been estabilished the voltage gates on Na channel close

Question 33

hyperpolarisation

Answer 33

slight overshoot in movement of K+ meaning that the inside of the axon is more negative than usual gates on K+ channels now close

Question 34

refraction period

Answer 34

time after each action potential cell membrane can't be stimulated to pass another signal as it takes time to recover from the last one

Question 35

why do you need a refraction period

Answer 35

makes sure action potential is only transmitted in one direction

Question 36

AP - Repolarisation

Answer 36

K+ rush out making inside cell more negative

Question 37

synaptic cleft

Answer 37

the gap which seperates the axon of one neurone from the dendrite of the next neurone approx. 20-30 nm across

Question 38

presynaptic neurone

Answer 38

neurone along which the impulse has arrived

Question 39

postsynaptic neurone

Answer 39

neurone that recieves the neurotransmitter

Question 40

synaptic knob

Answer 40

swollen end of presynaptic neurone contains many mitchondria and large amounts of endoplasmic reticulum to enable it to manufacture neurotransmitters

Question 41

synaptic vesicles

Answer 41

vesicles containing neurotransmitters vesicle fuse with presynaptic membrane and release their contents into synaptic cleft

Question 42

neurotransmitter receptor

Answer 42

receptor molecules which the neurotransmitter binds to in the postsynaptic membrane

Question 43

excitatory neurotranmitters

Answer 43

results in depolarisation of the postsynaptic neurone if threshold is reached in postsynaptic membrane an action potential is triggered

Question 44

inhibitory neurotransmitter

Answer 44

results in hyperpolarisation of

Question 45

why does synaptic transmission occur

Answer 45

-action potential reaches end of the presynaptic neurone -depolaristaion of the presynaptic neurone causes Ca2+ channels to open -Ca2+ diffuse into presynaptic knob -causes synaptic vesicles containing neurotransmitters to fuse with presynaptic membrane -neurotransmitter is released into synaptic cleft by exocytosis -neurotransmitter diffuses across synaptic cleft and binds to specific receptor molecule on postsynaptic membrane -causes Na+ channels to open and Na+ to diffuse into postsynaptic neurone -triggers action potential and impulse is propagated along postsynaptic neurone

Question 46

what does a synapse act as

Answer 46

junctions

Question 47

2nd step for synapse - neurotransmitter release

Answer 47

influx of Ca2+ cause synaptic vesicles to fuse with presynaptic membrane releases neurotransmitter into cleft Ca2+ cause release of neurotransmitter

Question 48

3rd step for synapse - sodium channels

Answer 48

neurotransmitter released into synaptic cleft moves across by diffusion Acetylcholine binds to receptor site on Na+ channels Na+ channels open Na+ diffuse in postsynaptic neurone depolarise

Question 49

4th step for synapse - new action potential

Answer 49

depolarisation inside postsynaptic neurone must be above threshold value-55mV if threshold reached a new action potential is sent along the axon of post synaptic neurone

Question 50

5th step for synapse

Answer 50

hydrolytic enzyme acetylcholinesterase breaks acytylcholoine into acetyl(ethanoic acid) and choline Na+ channels close 2 bits diffuseback across cleft into presynaptic neurone to allow neurotransmitter to be recycled

Question 51

6th step for synapse

Answer 51

ATP released is used to recombine acetly and choline to recycle acetylcholine which is stored in synaptic vesicles more acetylcholine can be made in SER synapse is now ready to be used again

Question 52

roles of synapses

Answer 52

ensure impulses are undirectional allow impulses from one neurone to be transmitted to a number of different neurones at multiple synapses number of neurones may lead in to same synapse with a single postsynaptic neurone