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Flashcards in How Nerves Work Deck (38):
1

Give the three subdivisions of the nervous system

- the brain
- the spinal cord
- peripheral nerves

2

What are the two subdivisions of the peripheral nervous system?

- sympathetic nervous system
- autonomic nervous system

3

Give the five components of the neurone

- cell body/soma
- dendrites
- initial segment
- axon
- axon terminals

4

What part of the neurone contains the nucleus?

Soma

5

At what part of the neurone is the information for making action potentials arranged?

Initial segment

6

What part of the neurone is an important route for the information from other neurones?

Dendrites

7

What part of the neurone takes the action potential elsewhere?

Axon

8

What part of the neurone connects with other nerves/muscles and releases neurotransmitter?

Axon terminals

9

What is the typical RMP of neurones?

around -70mV

10

What pumps are present in the cell membrane?

Sodium/potassium pumps

11

What do potassium specific ions channels in the membranes allow?

Potassium to flow out down the conc gradient through facilitated diffusion

12

The electrical gradient pulling the potassium back into the cell eventually becomes equal to the conc gradient pushing the ions out of the cell. This alone would create a resting potential of -90mV, so why is RMP closer to -70mV?

Due to the permeability of the membrane to other ions and leaky channels

13

How do neurones communicate?

Using action potentials

14

What are action potentials?

Large all or nothing signals that can self propagate

15

What needs to happen before an AP can be fired?

A graded potential must reach a significant level

16

Give features of graded potentials

- vary in intensity with intensity of stimulus
- decremental
- can only transmit over very short distances
- can be inhibitory or excitatory depending on which ion channels are open
- can summate through temporal or spatial summation

17

What happens once a graded potential reaches the correct threshold?

Action potential will be fired
- voltage gated sodium channels in the membrane open
- sodium rushes in
- this causes huge depolarisation of the neurone
- this in turn causes K+ channels to open
- cell repolarises then hyper polarises

18

What effect do these graded potentials have?

Change the potential of the neurone to around +40mV

19

Are action potentials graded or all or nothing?

All or nothing

20

Intensity of an AP is not shown in amplitude but instead by

frequency

21

Action potentials are

self-propagating, since the charge created by influx of Na+ ions spreads a bit up the axon, opening the channels there too, allowing further influx and propagation of the signal

22

What three types of nerve fibre are there and what are their functions?

Afferent (sensory) - detect changes or sensory stimuli

Interneurones - contained within the spinal cord, decide what to do about the stimulus

Efferent (motor) - if an excitatory response is warranted, these neurones carry the signal to the effector tissues or cells

23

Neurones can be ___ or ___,
and ___ or ___

large or small

myelinated or unmyelinated

24

Large axons allow for

a much faster transmission speed, since resistance is decreased

25

Faster transmission speed allows for

the charge to travel further up the axon when Na+ channels are opened, which in turn allows them to be placed further apart and less are needed

26

Since the most time consuming part is the opening of these channels, reducing the number needed

increases transmission time

27

Myelination also speeds up transmission by

surrounding the axon in a lipid sheath formed from Schwann cells (replaced by oligodendrocytes in the CNS)

28

Sodium channels are only found

in the nodes of Ranvier between these sheaths which allows the transmission to travel further due to the insulation provided

29

Give an example of a demyelinating disease

Multiple sclerosis

30

Describe the consequences of demyelinating disease

- eat holes in the Schwann cells
- results in rapid decay of APs
- preventing APs from reaching the next node and from propagating
- conduction falls

31

At the NMJ, the motor end plate from the neuronal axon comes to the muscle and

forms a synapse

32

On the muscle side of the synapse lies the

sarcolemma

33

The membrane of the sarcolemma has junctional folds with

ACh receptors, leading deeper into the muscle allowing for deeper contraction

34

Describe the process of neuromuscular transmission

- AP in axon opens Ca2+ channels in presynaptic terminal
- triggers fusion of vesicles and ACh is released into the cleft
- diffuses across and binds to receptors in the junctional folds
- ligand gated Na+/K+ channels are opened
- local end plate potential is produced which always reaches threshold so AP is fired, opening up voltage gated Na+ channels
- ACh is removed by acetylcholinesterase

35

Neuronal synapses are similar to the neuromuscular junctions, but the few differences make a huge amount of differences. List these differences

- wide range of neurotransmitters
- range of postsynaptic potentials
- anatomical arrangements of synapses
- synaptic connectivitty

36

Give the four types of postsynaptic potentials

- fast EPSPs
- slow EPSPs
- fast IPSPs
- slow IPSPs

37

Give the three anatomical arrangements of synapses

- axo-somatic
- axo-dendritic
- axo-axonal

38

Give the two types of synaptic connectivity

- convergence
- divergence