9.2

Question 1

peripheral nervous system

Answer 1

afferent
-sensory
efferent
-motor

Question 2

central nervous system

Answer 2

central -brain and spinal chord
peripheral - pairs of nerves which originate from the brain or spinal chord

Question 3

efferent nervous sytem

Answer 3

somatic
-under voluntary control
autonomic
-involuntary

Question 4

autonomic nervous system

Answer 4

sympathetic
-positive stimulation
-speed up
-fight or flight
parasympathetic
-inhibitory
-slows down activity
-resting and digesting

Question 5

compare and contrast sym and para

Answer 5

sim -
NS fibres leave the CNS in a ganglion (collection of nerve fibres)
dis-
sym, ganglia close to the CNS
para, ganglia close to the effector organ y

Question 6

compare and contrast sym and para funtions

Answer 6

sym
-produces noradrenaline
-fight or flight response
-activated in times of stress or active
-adrenergic synapses

para
-slower, inhibitory effect
-acetychloine neurotransmitter produced
-maintains normal functioning of the body
-chloinergic synapses

Question 7

resting potential

Answer 7

inside of the axon is negatively charged compared to the outside of the axon
outside ions more concentrated
axon is polarised
-70mV

Question 8

sodium pottasium pump

Answer 8

requires energy
3 Na+ ions moved out of the membrane for every 2 K+ ions in
ATPase in pump uses ATP to move cations

Question 9

how is resting potential maintained

Answer 9

sodium pottasium pump
Na+ out K+ in
K+ move through pottasium chanells
NA chanells close
outside more positive than inside

Question 10

action potential

Answer 10

stimulus is recieved
causes a tempary reversal of the charge on the axon membrane - inside less negative
moves to about +40mv
membrane depolarised

Question 11

depolarisation

Answer 11

-resting potential some k voltage-gated channels are open but Na channels are closed
-the stimulus causes some Na gates in the axon membrane to open and therefore some sodium ions move into the axon via facilitated diffusion
as they are +vly charged they trigger a reversal in the pd
-as it is more +ve more voltage-gated sodium channels open - +ve feedback
-once the action potential is around +40mv the voltage-gated sodium ion channels close
-excess sodium ions are pumped out by Na-K pump

Question 12

repolarisation

Answer 12

-voltage-gated potassium channels open so K ions move out the axon by facilitated diffusion down the conc grad
-cell is repolarised and becomes more negative

Question 13

hyperpolarisation

Answer 13

-more potassium flows out
- the inside is more negative than the outside so more negative than the resting potential

Question 14

after hyperpolarisation

Answer 14

gates on K+ channels now close and Na-K pumps Na to be out and K in
-70 mv is reestablished

Question 15

action potential simplified

Answer 15

Na+ voltage gated channels open
Na+ diffuse rapidly into axon
potential difference reversed
Na+ voltage gates close
K+ voltage gated chanells open
K+ diffuse out of axon
inside axon returns to negative
resting potential restored

Question 16

absolute refractory period

Answer 16

sodium chanells are completly blocked and the resting potential hasnt been restored
milisecond
second stimulus will not trigger a second action potential

Question 17

relative refractory period

Answer 17

pottasium chanells are able to repolarise the membrane and pottasium ions difuse out of axon
Normal resting potential can not be restored until these K channels are closed.
Last several milliseconds.
During this time, a greater than normal stimulus is required to initiate an action potential.

Question 18

refractory period

Answer 18

time taken for an area of the axon membrane to recover after an action potential
depends on
-Na/K pump
-membrane permeability to potassium ions

Question 19

purpose of a refractory period

Answer 19

enure action potentials are only in one direction
produce discrete impulses - action potentials are separated
limits the number of action potentials

Question 20

events at synapse

Answer 20

Action potential depolarises the presynaptic neuron.( increases the permeability )
Calcium channels open and calcium diffuses in down conc grad
Synaptic vesicles move to and fuse with the pre-synaptic membrane.
The neurotransmitter is released into the synaptic cleft.
Neurotransmitter moves across cleft by diffusion.
Neurotransmitter binds to specific protein receptors on the sodium channel on the post synaptic membrane..
Sodium channels open and sodium diffuses in.
This causes a change in the potential difference of the membrane and an excitatory post-synaptic potential (EPSP) to be set up.
if there are enough epsp the +ve charge exceeds the threshold level and an action potential is set up

Question 21

types of synapse

Answer 21

cholinergic
adrenergic
-use noradrenaline

Question 22

Inhibitory post-synaptic potential (IPSP)

Answer 22

is a kind of synaptic potential that makes a postsynaptic neuron less likely to generate an action potential.
Here, different ion channels open in the membrane, allowing inward movement of negative ions.
This makes the post-synaptic cell more negative than normal resting potential.
This means an action potential is less likely to occur.

Question 23

saltatory conduction

Answer 23

mylenated neurones ions can only pass in and out of the axon freely at the nodes of ranvier
action potential can only occur at the nodes
so apear to jump
speed up transmition as the ionic movemetns happen less frequently taking less. time

Question 24

transmission in unmylenated axons

Answer 24

A current (change in potential difference) occurs in a part of the neuron.
This is detected in the adjacent part of the membrane.
When it detects the current, it causes voltage gated channels to open and an action potential will occur when the threshold is reached.
The nerve impulse is transmitted as a self-propagating wave of depolarisation.

Question 25

mylenated nerves

Answer 25

schwann cell membrane wraps around cell many times to form mylein sheith gaps called nodes of ranvier -speeds up transmittion and protects from damage

Question 26

factors affecting nerve impulses

Answer 26

mylenation axon diamater -speed of transmission temperatures -rate of diffusion increases

Question 27

breakdown of neurotransmitters

Answer 27

Neurotransmitters are broken down by hydrolytic enzymes in the synaptic cleft They then move back across the cleft, back into the synaptic knob, and are recycled.

Question 28

acethycholine

Answer 28

Acetylcholine is the neurotransmitter which is found at the majority of synapses in humans. nerves using acetylcholine are called cholingernic nerves usually results in excitation at the post synaptic membrane After it attaches to the receptors on the sodium channels, it is broken down by an enzyme called acetylcholinesterase. It hydrolyses acetylcholine into separate acetate and choline. The acetyl and choline diffuse back across the cleft into the presynaptic neuron. This allows the neurotransmitter to be recycled.

Question 29

affects of drugs increasing the response

Answer 29

-increases amount of neurotransmitter -increases release of neurotransmitter from vesicles at the presynaptic membrane -binds to post-synaptic receptors and activates them or increases affect of normal neurotransmitter -prevents the degradtion of neurotransmitter by enzymes or prevents reuptake into presynaptic knob

Question 30

affects of drugs decreasing the response

Answer 30

-blocks synthesis of neurotransmitter -causes neurotransmitter to leak from vesicles and be destroyed by enzymes -prevents releases of neurotransmitter from vesicles -blocks receptors and prevents neurotransmitter binding

Question 31

nicotine

Answer 31

-mimics the effect of acetylcholine and binds to specific receptors in post synaptic membranes -triggers action potential -receptor remains unresponsive for some times -raised heart rate and blood pressure -triggers release of neurotransmitter dopamine

Question 32

lidocaine

Answer 32

-anastethic block voltage-gated sodium chanells preventing action potential - no pain -prevent heart arthimias raises depolarisation threshold so prevents early or extra action potentials

Question 33

cobra venom

Answer 33

toxic and fatal -binds reversibly to acetylcholine receptors in post synaptic membranes and neuromuscular junctions -prevents the transmission of impulses across synapses -including neuromuscular junctions between motor neurons and muscles -muscles not stimulated to contact and person becomes gradually paralysed when reaches muscles for breathing causes death - in low doses can relax muscles of trachea and bronchi in asthma attacks

Question 34

transduction in the eye

Answer 34

converts light into nerve impulses occurs in the retina by cones and rods which are attached to receptors

Question 35

rod cells

Answer 35

spread evenly across retina more rod than cone provides images in black and white -cant distinguish between wavelengths detect at low intensity certain threshold must be detected before a generator potential can occur cannot distingush between close together things as only one impulse is generated connected to bipolar neurone - sensory neuron - optic nerve

Question 36

generator potential

Answer 36

generated by the breakdown of the pigment rhodopsin- bleaching (low light intensities) when bleaching occurs Na ion channels close sodium pump still works so sodium ions removed inside rod cells more negative that normal as hyperpolarisation occurs this is a generator potential if meets threshold can cause action potential rhodopsin must be resythesised before can occur again do not follow the all or nothing rule

Question 37

retianal convergence

Answer 37

allows a generator potential to be reached with low levels of stimulus

Question 38

cone cells

Answer 38

tightly packed in fovea 3 different types for dif wavelengths seperqate bipolar neurones high light intensity can distinguish between seperate sources high light intensity breaks down iodopsin different types of iodoposin larger stimulus required to reach generator potential

Question 39

fovea

Answer 39

part where the light is focused on recieves greatest intensity no rod cells

Question 40

bleaching

Answer 40

Rhodopsin is formed from opsin and retinal. Retinal exists as 2 different isomers: cis-retinal & trans-retinal. In the dark all retinal is in the cis form. When a photon of light hits the rhodopsin, it converts from cis to trans form. This changes the shape of the retinal and puts strain on the bonding between opsin and retinal, breaking up the molecule.

Question 41

nervous system structure

Answer 41

neurons transmit impulses from receptor cells to effector cells or groups of them called sense organs 3 types of neurone

Question 42

eye structure

Answer 42

Question 43

brain structure

Answer 43

Question 44

spinal chord

Answer 44