neurones definitions.

Question 1

what is meant by the term polarised?

Answer 1

a membrane that has a potential difference across it

Question 2

depolarisation def?

Answer 2

loss of polarisation acrossa membrane
+40mV
refers to the period when Na+ channels open and Na+ ions diffuse by facilitated diff into the membrane.

Question 3

resting potential def?

Answer 3

the pd of a neurone at rest when there is no action potential being transmitted.
-70mV

Question 4

action potential def?

Answer 4

the depolarisation of the cell membrane

Question 5

hyperpolarization def?

Answer 5

when the pd overshoots slightly and influx of K+ ions facilitated diff out of neurone membrane resulting in the membrane pd becoming more -ve than at restig potential of -70mv.

Question 6

refractory period ?

Answer 6

The time after an action potential has passed + no more APs can be stimulated across the membrane as the Na+ channels are closed.
Na+/K+ pump is used to return the membrane back to resting to potential by redistributing the ions to their correct places.

Question 7

threshold potential def?

Answer 7

a pd across a membrane at -55mv . If a stimulus does not reach threshold potential an action potential will not be generated.

Question 8

generator potential def?

Answer 8

a small change in the potential difference within a cell due to some Na+ diffusing into the cell.

Question 9

all or nothing principle def?

Answer 9

the principle that a stimulus must reach at least threshold potential (-55mv) for an action potential to be generated.
No matter how large the stimulus the action potential will always be the same size

Question 10

repolarisation def?

Answer 10

when a membrane is restored back to its resting potential

Question 11

saltatory conduction def?

Answer 11

when an action potential jumps between nodes of ranvier + depolarisation ONLY occurs at the unmylinated NOR

Question 12

potential difference def?

Answer 12

the difference in charge inside + outside of a neuron

Question 13

local current flow ?

Answer 13

movement of action potential down conc gradient inside the neuron membrane from high Na+ => low Na+
leads to +ve feedback as Na+ channels open leading to more Na+ ions diffusing into membrane.

Question 14

potential def?

Answer 14

• the term used to be describe the movement of charged particles across a membrane of a cell.

Question 15

nerve impulses?

Answer 15

an action potential potential that is along an axon to other end of a neuron.

Question 16

what is a synapse?

Answer 16

a gap between 2 neurons

Question 17

what is the synaptic cleft?

Answer 17

the space that separates the axon of one neuron and another dendrite
it is the space where NT are released by exocytosis + where they diffuse towards post synaptic neuron.

Question 18

what is the presynaptic neuron?

Answer 18

the neurone wihch the AP is sent from / neuron where hte neurotransmitters are released by exocytosis from

Question 19

what is the post synaptic neuron?

Answer 19

the neuron where the neurotransmitter binds to (on the receptors on the membrane)

Question 20

what is the synaptic knob?

Answer 20

the swollen end of a presynaptic neuron where Mt and SER are present to make neurotransmitters which are released by exocytosis.
contains neurotransmitters

Question 21

what is the synaptic vesicle?

Answer 21

the neurotransmitter receptor that the NT bind to on the post synaptic neuron.

Question 22

what are neurotransmitter vesicles?

Answer 22

vesicles in the presynaptic neuron that contain the NTs

Question 23

what are excitatory synapses?

Answer 23

a synapse where the NTs eg Ach bind to post synaptic membrane causing depolarisation so that an action potential can be propgated.

Question 24

what are inhibitory synapses?

Answer 24

a synapse where neurotransmitters eg GABA hyperpolarise the membrane pf the post synaptice membrane ( ie making inside more -ve than RP) so that action potentials cant be fired

Question 25

what is synaptic divergence?

Answer 25

when one neurone joins with many others to disperse info (APs ) to different parts of the body.

Question 26

what is synaptic convergence?

Answer 26

when MULTIPLE neurons connect to ONE neuron so that info can be amplified.

Question 27

give 5 examples of neurotransmitters?

Answer 27

serotonin 
epinephrine 
dopamine 
adrenaline 
Acetylcholine

Question 28

function of Acetylecholinesterase?

Answer 28

enzyme that breaks down Ach in synaptic cleft to choline + acetic acid + choline by HYDROLYSIS.

Question 29

what is summation?

why is it needed?

Answer 29

this is where the effect of NTs can be combined to stimulate an action potential
- summation may be needed when there is a WEAK STIMULUS (not a small AP bc all AP same size) that causes a few NTs to be released into the synaptic cleft. -> this may not be enough to excite the post synaptic membrane to threshold + thus may not be enough to stimulate an action potential.

Question 30

temporary summation?

Answer 30

this is when multiple action potentials are fired rapidly in a quick succession one after the other within a short time frame.

Question 31

why does the firing of AP across a neuron need to be in a short timeframe in temporal succession?

Answer 31

• so that the AP can add on to each other to reach threshold potential

Question 32

spatial summation?

Answer 32

when action potentials on several different presynaptic neuron simultaneously arrive at the post syn neuron to reach threshold + trigger an action potential in the post synaptic neuron.

Question 33

benefit of summation?

Answer 33

synapses can accurately process the information received.

Question 34

how do synapses ensure that the impulses are transmitted one way only?

Answer 34

• receptors for the neurotransmitters are only found on the post synaptic neuron.

Question 35

what are the 4 main roles of synapses?

Answer 35

unidirectional transmission from presynaptic neuron to post synaptic by having receptors o the POST syn only

• can cause multiple responses from one stimulus (divergent synapse)
• can receive multiple responses for one response (convergence synapse)