nervous coordination and muscles

Question 1

state differences between the hormonal and nervous system

Answer 1

HORMONAL
- communication is via hormones
- transmission is via the bloodstream
- transmission is usually slow
- response is slow
- response is long lasting
- NERVOUS SYSTEM
- communication is via nerve impulses
- transmission is via neurones
- transmission is very rapid
-response is rapid
- response is short lived

Question 2

what is the function of the cells body in a neurone

Answer 2

contains cell organelles - large amounts of RER though which is associated with the production of proteins and neurotransmitters

Question 3

what is the function of a dendron

Answer 3

extensions of the cell body which subdivide into dendrites ( smaller branched fibres).
they will carry impulses towards the cell body

Question 4

what is the function of the axon

Answer 4

a single long fibre that carries impulses away from the cell body

Question 5

what is the function of schwann cells

Answer 5

provide electrical insulation, they also carry out phagocytosis

Question 6

what is the function of the myelin sheath

Answer 6

forms a covering to the axon

Question 7

what is the function of nodes of ranvier

Answer 7

constrictions between adjacent Schwann cells - electrical impulses can jump making transmission faster

Question 8

what is the function of a relay neurone

Answer 8

transmit impulses between neurones

Question 9

what is the resting potential in humans

Answer 9

-65mV

Question 10

when the axon has a resting potential what is it said to be

Answer 10

polarised

Question 11

describe how a resting potential is established

Answer 11

• sodium ions are actively transported out of the axon by na/k pumps
• potassium ions are actively transported into the axon by the Na/K pumps
  for every 3 sodium’s moved out two potassium’s move in.
  -an electrochemical gradient will be established due to a differential in charges
• sodium will diffue back in
• potassium will diffuse back out
  -however most of the potassium channels are open and the sodium ones will close

Question 12

what happens when the axon becomes depolarised

Answer 12

an action potential is reached. the charge inside the membrane is +40mV

Question 13

what happens in inhibiton

Answer 13

the presynaptic neurone releases a type of neurotransmitter that binds to a chloride ion protein channels on postsynaptic neurone.
- the neurotransmitter causes the chloride ion channels to open.
- chloride ions move into the post synaptic neurone by facilitated diffusion
-this binding causes the K+ channels to open
-k+ions move out of the postsynaptic neurone into the synapse
- the combined effect of cl- moving in and k+ moving out will make the postsynaptic membrane more negative than the outside

Question 14

what si the function of a synapse

Answer 14

acts as a junction to allow a single impulse to initiate new impulses in numerous neurones. and or a number of impulses to be combined at the synapse.

Question 15

what is temporal summation

Answer 15

where a presynaptic neurone releases neurotransmitter many times over a short period - if the concentration of neurotransmitter exceeds the threshold value then an action potential can be is triggered in the postsynaptic neurone

Question 16

what is spatial summation

Answer 16

in which a number of presynaptic neurones together release a number of neurotransmitters to exceed the value to stimulate an action potential in the postsynaptic neurone.

Question 17

where are the neurotransmitters stored

Answer 17

synaptic vesicles

Question 18

what are features of synapses

Answer 18

• unidirectionality
• summation

Question 19

what is a cholinergic synapse

Answer 19

a synapse where the neurotransmitter that is secretes acetylcholine

Question 20

what are some factors that will affect the speed of a nervous impulse

Answer 20

• nodes of ranvier ( jumping or poshly described as saltatory conduction) this will increase the speed of conductance.
• the diameter of the axon - the greater the diameter of the axon the faster the speed of conductance

-temperature - this will affect the rate of diffusion of Na/K ions
higher = faster however denaturing of plasma proteins

Question 21

what is the all or nothing principle

Answer 21

the threshold value of stimulus which is needed to trigger an action potential. nothing will happen without this threshold value so no action potential.
its all or nothing

Question 22

what is the refractory period

Answer 22

when the sodium ion channels are closed - during this time it is impossible for a further action potential to be generated

Question 23

what is the purpose of a refractory period

Answer 23

• it ensures that action potentials are only propagated in one direction
• it allows for action potentials to be separated from one another
• it limits the number of action potentials and therefore the strength of the stimulus that can be detected

Question 24

what is a receptor

Answer 24

a protein or cell that can detect stimulus

Question 25

define a neurotransmitter

Answer 25

a chemical which is secreted by a neurone within the nervous system to stimulate a target cell

Question 26

what are the main ways that drugs act on the synapse

Answer 26

• drugs can mimic a neurotransmitter
• stimulate the release of a neurotransmitter
• inhibit the enzyme that breaks down the neurotransmitter
• block a receptor channel

Question 27

describe the signal transmission of ACh at the cholinergic synapse

Answer 27

• an action potential arrives at the end of the presynaptic neurone
• this depolarises the membrane and stimulates the voltage-gated Ca2+ channels to open and an influx of Ca2+ to enter the synaptic knob
• this influx of Ca2+ causes the vesicles containing ACh to fuse to the presynaptic membrane and releasing ACh intot he cleft via exocytosis
• ACh diffuses across the cleft and binds to the specific receptors on the postsynaptic membrane - which will cause a slight delay in impulse
• the neurotransmitter binds to the Na+ channels which open and an influx of sodium depolarises the postsynaptic membrane

Question 28

what happens when acetylcholine diffuses across to the postsynaptic neurone

Answer 28

acetylcholinesterase hydrolyses acetylcholine into choline and ethanoic acid, which diffuses back across the synaptic cleft intot he presynaptic neurone. this is advantageous because discrete transfer of acetylcholine can occur across the synapse