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Flashcards in How Nerves Work Deck (38)
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1

what are the 3 subdivisions of the nervous system?

Somatic nervous system
Autonomic nervous system
Enteric nervous system

2

What are the 6 different regions of spinal nerves

Cranial
cervical
thoracic
lumbar
sacral
coccygeal

3

what is a ganglion?

collection of nerve cell bodies

4

what types of information do afferent and efferent neurones convey?

afferent - sensory
efferent - motor

5

what types of information do the dorsal and ventral roots correspond to ?

dorsal - afferent
ventral - efferent

6

what is the function of the dendrites?

receive information from other neurons

7

what are the 3 parts of the axon and their functions?

initial segment (axon hillock) - triggers action potential
Axon - sends action potential
Axon terminals (presynaptic) - release transmitter

8

what separates interneurones from afferent and efferent neurones?

interneurones are found only within the central nervous system

9

what are glia?

specialised cells in the CNS, they compose 90 percent of cells in the CNS

10

name 3 types of glia and their function

astrocytes - surround blood vessels and produce the blood brain barrier
oligodendrocyes - form myelin sheaths in the CNS

11

what is the resting membrane potential?

the resting electrical charge across a cell membrane (usually around -70mV)

12

what is the equilibrium potential?

when the electrical gradient pulling potassium into the cell equals the concentration gradient drawing potassium out of the cell

13

what is the effect of a raised ECF concentration of potassium?

depolarises the cell (reduces resting membrane)

14

how does the blood brain barrier resist changes in extracellular potassium?

astrocytes and tight junctions between capillaries in the brain keep the potassium confined to the capillaries; hence no change in ECF potassium.

15

why is the RMP closer to -70mV as opposed to the -90mV resting potential of potassium?

other leaky channels such as sodium and chlorine
electrogenic nature of the sodium potassium pump
large, negatively charged intracellular molecules.

16

what is the purpose of a graded potential?

to "decide" whether or not to fire an action potential

17

give 4 examples of graded potentials

generator potentials
postsynaptic potentials
endplate potentials
pacemaker potentials

18

why are graded potentials only useful over short distances?

they are decremental so they cannot travel over long distances without the signal dissipating

19

what signals the intensity of a stimulus in a graded potential?

amplitude.

20

are graded potentials depolarising or hyperpolarising?

Can be either; depolarising would be an EPSP, hyperpolarising would be an IPSP.

21

how would a hyperpolarising postsynaptic potential hyperpolarise a cell?

open Cl- channels (fast IPSP) or open more K+ channels (slow IPSP)

22

how would a depolarising postsynaptic potential depolarise a cell?

open channels that are permeable to both Na+ and K+; more sodium enters the cell than potassium escapes (fast EPSP). closes channels that allow K+ out of the cell (slow EPSP)

23

are postsynaptic potentials produced by ligand or voltage gated channels?

ligand gated

24

are action potentials produced by ligand or voltage gated channels?

voltage gated

25

graded potentials can summate; true or false?

true

26

what is the difference between temporal and spatial summation?

temporal summation is when the same stimulus is applied more than once, spatial summation is when 2 different stimuli are applied.

27

what is the purpose of synaptic integration?

the process of summating all the synaptic inputs to determine whether the initial segment reaches threshold and an action potential is fired.

28

Chemically, what causes the massive depolarisation that leads to an action potential being fired?

massive influx of sodium into the cell.

29

what is the refractory period?

length of time after firing the action potential where the cell is unable to be excited.

30

what signals stimulus intensity in action potentials?

frequency.

31

how do action potentials self propagate?

the massive depolarisation caused by the influx of sodium causes the next set of sodium channels to also become depolarised and open; more sodium flows into the cell and the action potential self propagates.

32

why can an action potential only self propagate in one direction?

because the sodium channel "behind" the one that is open is in its refractory period, which means it is unable to open and so the wave of depolarisation can only spread "down" the cell.

33

what is the effect of myelination of a nerve cell?

increases the distance an action potential can travel without dissipating. sodium channels are only present at the gaps (nodes of ranvier) between the myelin sheaths.

34

what is the clinical importance of de-myelination?

action potentials cannot travel far enough down the axon to make the next node depolarise to threshold and hence, conduction fails - multiple sclerosis, guillain barre syndrome.

35

how would a compound action potential be viewed on a graph?

fastest conducting APs are registered first (obviously), then the slower ones.

36

what triggers contraction in muscles?

Action potential in the sarcolemma

37

what are the steps that lead to contraction in muscle with regard to the neuromuscular junction?

AP travels down motor neurone
opens voltage gated calcium channels in the presynaptic terminal
causes release of ACh across synapse.
Ach binds to nicotinic receptors
opens ligand gated Na/K channels
evokes an end plate potential which always depolarises adjacent membrane to threshold
Depolarisation opens more voltage gated Na+ channels - new AP
ACh is removed by acetylcholinesterase.

38

What differences are there between synapses in the NMJ and the CNS?

much wider range of transmitters in CNS
Range of postsynaptic potentials.
Synaptic integration
CNS synapses can have different anatomical arrangements (axo somatic, axo dendritic and axo axonal)
Convergence and divergence in synaptic connectivity.
feedback inhibition
monosynaptic and polysynaptic pathways