Receptors and Neurons

Question 1

sensory neuron

Answer 1

sends nerve impulses from receptors to cns

Question 2

relay neuron

Answer 2

sends nerve impulses from sensory to motor neuron

Question 3

motor neuron

Answer 3

send nerve impulses from cns to effectors

Question 4

chain reaction from a stimulus to effectors

Answer 4

stimulus, receptors, via sensory neuron to the cns, via motor neurone to effectors, response

Question 5

sensory receptors

Answer 5

act as transducers, convert energy of a stimulus into electrical energy

Question 6

potential difference at rest

Answer 6

resting potential

Question 7

what does a stimulus do to a receptor

Answer 7

excites the cell membrane, increases permeability, more ions move in and out.

Question 8

change in potential difference due to a stimulus

Answer 8

generator potential

Question 9

how to trigger an action potential

Answer 9

generator potential needs to reach the threshold level

Question 10

pacinian corpus

Answer 10

mechanoreceptor that detects mechanical stimuli like touch, found in the skin and contain a sensory nerve ending

Question 11

what is a sensory nerve ending wrapped in

Answer 11

lamellae

Question 12

stimulating a pacinian corpus

Answer 12

e.g tap on arm. lamellae get deformed and press on sensory nerve ending, this causes a deformation of stretch mediated sodium channels, they open Na+ ions diffuse in, if GP reaches threshold action potential is triggered

Question 13

structure of sensory neuron

Answer 13

many short dendrites that carry a nerve impulse from receptors to cell body via one long dendron, then this nerve impulse travels to cns via short axon

Question 14

structure of motor neuron

Answer 14

many short dendrites that carry nerve impulses from cns to cell body, 1 long axon carries from cell body to effectors

Question 15

structure of relay neuron

Answer 15

short dendrites carry nerve impulses from sensory neuron to cell body and one axon to the motor neuron

Question 16

what happens at a neurones resting state in terms of charge

Answer 16

outside of membrane is more + charged than inside , membrane is polarised

Question 17

what is the resting potential (number)

Answer 17

-70mV

Question 18

how is the resting potential of a neurone maintained

Answer 18

na/k pumps move 3 Na+ ions out and brings in 2 K+ ions in (active transport). membrane impermeable to Na+ but some K+ ions diffuse out of cell via facilitated diffusion

Question 19

1) Action potentials: Stimulus

Answer 19

stimulus excites cell membrane, becomes more permeable Na+ diffuses in via channels

Question 20

2) Action potentials: Depolarisation

Answer 20

if PD reaches -55mV, voltage gated Na+ channels open so more Na+ enters the neurone this is POSITIVE FEEDBACK

Question 21

3) Action potentials: Repolarisation

Answer 21

PD reaches +30mV this causes Na+ channels to close and voltage K+ channels to open and diffuse OUT, resting potential is maintained

Question 22

4) Action Potentials: Hyperpolarisation

Answer 22

K+ channels are slow to close this causes an ‘overshoot”. PD becomes more negative than -70mV, Na/K pumps restore resting potential

Question 23

Refractory Period

Answer 23

After an action potential, ion channels are recovering and can’t be opened.

Question 24

How does a wave of depolarisation occur

Answer 24

when Na+ diffuses out sometimes they diffuse sideways this causes the Na channels in the next region to open and this process repeats.

Question 25

effect of a bigger stimulus

Answer 25

more frequent action potentials

Question 26

Myelinated neurones

Answer 26

have a myelin sheath which is made from Schwann cells, they are electrical insulators

Question 27

Nodes of Ranvier

Answer 27

bare membrane, Na channels concentrated here, depolarisation in myelinated neurones occurs here, impulse jumps from node 2 node - salatory conduction

Question 28

myelinated vs non myelinated

Answer 28

myelinated is faster