1what is produced when Na channels open and there is an influx of Na ion in the cell causing a change in potential difference
generator potential
2what is the role of a Na/K pump in the membrane
actively pumps 3Na ions out the cell and 2K ions into the cell
3when all channel proteins are closed, Na/K pump creates a ____________ ________. the conc of Na ions out the cell is ____ and the conc of K ions in the cell is ____
concentration gradient, high, high
4process of depolarisation
->na channels open = na moves into cell and decreases conc gradient= creates change in potential difference across memb= cell becomes less negative compared to outside
5motor neurones carry the --- from the --- to an ---. sensory neurones carry the --- from --- --- to the ---. relay neurones connect the two neurones
Ap, cns, effector, Ap, sensory receptor, cns
6---carry impulses towards the cell body and --- carries impulses away from cell body
dendrites, axon
7schwann cells role
insulate cell from electrical activity in other nearby nerve cells
8in myelinated neurones --- --- are tightly wrapped around the neurone. this only allows --- to move across the memb at --- ---- ---. this makes --- more rapid
schwann cells, ions, nodes of ranvier, conduction
9in non myelinated neurones, several neurones may be enshrouded in 1 --- wrapped --- --- . therefore the ---moves along the neurones in a ----
schwann cells, loosely, ap, wave
10potential difference across the membrane at rest
-60mV, memb is polarised, more negative in cell than out, large anions in cytoplasm makes more negative
11activities when neurone is at hh
OPEN= Na/K pump using atp [3Na out and 2K in] CLOSED= gated Na ion channels and most gated K ion channels
12how is an action potential created
enough gated Na channels must open -> generator potentials(small depolarisations) combine ->makes larger depolariation which must overcome a threshold to create an a.p
13why is depolaroation of memb an example of positive feedback
changes in potential difference across memb opens opens V.G na channels -> small depolariation causes a change that causes further depolarisation
14potential difference across memb during depolarisation
40mV
15stages of an action potential-8
1.starts at rest 2. Na+ ch. open, some na+ diffuses into cell 3.memb depolarises and reaches threshold 4.+ feedback- nearby V.G na+ ch. open many na+ diffuse in 5.potential difference reaches 40mV 6.na ch. Close and k.ch open 7.k+ diffuses out cell- revitalisation 8.hyperpolarisation- pot diff slightly overshoots and cell returns to rest
16___ ___ allows cell to recover after an action potential. the conc of --- and --- in and out of cell is restored by --- --- pumps
refractory period , na, k
17the influx of na+ into the neurone creates ___ ____ . na moves along the neurone to regions of ___ conc of na.
local current , lower
18what do local currents cause
-> slight depolarisation of memb -> & na ch. to open further along the memb( + feedback) full depolarisation
19how are local currents
-> AP occurs-> V.G na ch. open->na diffuse in ->na diffuses sideways along neurone away from high conc of na
20why does action potential move in same direction why are
conc of na behind the action potential is still high
21the correct term for action potentials jumping between nodes
saltatory conduction
22saltatory conduction occurs in
- myelinated neurones
- unmyelinated neurones
23why are local currents in myelinated neurones described as elongated
na and k can't diffuse thru myelin sheath-> nodes of ranvier are gaps between schwann cells-> ionic movements that create an ap only occr at nor-> na diffuse along neurone from one nor to the next
24advantages of saltatory conduction
*ap only occurs at nor *ap jumps between nodes,speed up transmission *ap conducted quicker
25how is a more intense stimulus detected
more na ch. open in sensory receptor--> more generator potentials produced--> more frequently ap enters cns from sensory receptor
26what is a synapse
junction between 2+ neurones where 1 neurone can communicate with another neurone.
27what is a synaptic cleft
small gap between 2 neurones
28what happens to an action potential at the synapse
--> a.p in presynaptic neurone causes release of neurotransmitters --> neurotransmitter diffuse across synaptic cleft --> generates new a.p in post synaptic neurone
29what is a cholinergic synapse what
A synapse that uses acetylcholine as its neurotransmitters.
30features of pre synaptic bulb
many mitochondria, lots of SER, lots of vesicles with N.T, V.G ca2+ channels on p.memb
31the post synaptic membrane contains ---channels which consist of --- polypeptide molecules. 2 of these have --- site with a shape complementary to the shape of --- molecule
na+ , 5, receptor, acetylcholine/NT
32what happens when acetylcholine is present in the synaptic cleft
acetylcholine binds to the 2 receptor sites and causes the na+ channels to open
33describe the process of transmission of an action potential across the synapse. start with ap at synaptic cleft and end with it traveling down post synaptic neurone
--> a.p at synaptic cleft --> V.G ca2+ channel open --> ca2+ diffuse into synaptic bulb--> ca2+ causes synaptic vesicles to move and fuse with pre synaptic memb --> acetylcholine released via exocytosis and diffuses across cleft --> it binds to receptor site on na channel in post synaptic memb--> creates generator potential or EPSP --> if enough combine= pot reaches threshold --> new ap created in post SN --> ap passes down post SN
34acetylcholinesterase is an ---- found in the ---
enzyme, synaptic cleft
35role of acetylcholinesterase
hydrolysis acetylcholine into ethanoic acid/ acetate and choline --> stops transmission of signals so a.p not continually produced --> as acetylcholine will cont to open na+ channels and cause a.p if left at large.
36what does EPSP stand for
excitatory post synaptic potentials
37what happens to products of acetylcholine when hydrolysed in synaptic cleft by the enzyme acetylcholinesterase
ethanoic acid and choline recycled --> reenter synaptic bulb and recombine to form acetylcholine and stored in vesicles for future use.
38divergence of neurones and when it's useful
one neurone sending signals out to several neurones diverging to different effectors --> useful in reflex arcs
39convergence of neurones
several neurones converging on one neurone --> spatial summation
40action potential is passed down --- to ---. this causes a few vesicles to fuse with --- synaptic memb. a small no. of --- diffuse across cleft. this produces a small --- which is called ----. which is not sufficient to cause an --- in post synaptic memb
axon, synapse, pre ,acetylcholine, depolarisation, epsp, action potential
41what is summation
many epsp combine to increase memb depolarisation until it reaches the threshold
42what is temporal summation 9
summation resulting from many action potentials arriving from many different pre- synaptic neurones .
43what is spatial summation and why is it useful
summation resulting from action potentials arriving from many different pre synaptic neurones --> useful when several different stimul warn of danger
44what does IPSP stand for
inhibitory post synaptic potentials
45role of ipsp and what produces it
some pre synaptic neurones can make ipsps which decrease effect of summation and prevent a.ps in post synaptic neurone --> combo of many epsps prevented from making ap
46what happens if low level stimuli is persistent
low level a.p can be amplified by summation, generate several successive a.p in pre synaptic neurone. many acetylcholine released enable epsp to combine to make a.p
47why do neurones get fatigued
repeated stimulation causes synapse to run out of vesicles with n.t so neurone no longer responds and we become habituated to stimulus