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Science for Medicine Taz > How nerves work > Flashcards

How nerves work Flashcards

1
Q

Name the parts of the brain!!

A 
Front - frontal lobe
Middle - parietal lobe
Back - Occipital lobe
Bottom lobe - temporal 
Cerebellum - controls basic function - at the bottom too
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2
Q

what are low and high grooves in the brain called?

A

low - sulcus

high - gyrus

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3
Q

what nerves go to and from the brain - not via the spinal cord ?

A

cranial nerves

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4
Q

name the 3 subdivisions of the nervous system

A

autonomic, somatic, enteric

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5
Q

What nerves are sensory and what are motor?

A

Sensory - afferent

Motor - efferent

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6
Q

Describe what each part of the nerve does from the dendrite to the axon terminal

A

dendrite - receives information
cell body (soma) - makes things
Axon hillock (initial segment) - triggers action potential
Axon - sends action potential
Axon terminal - releases neurotransmitter

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7
Q

what roots does the sensory information come in, and what root does the motor information leave?

A

In - dorsal root (back)

Out - ventral root (front)

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8
Q

What is grey matter and what is white matter- which one makes the cross shape?

A

white - axons
grey - cell bodies
Grey is the middle bit

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9
Q

What does glia do - and how much of the CNS is it?

A

Cells that keep nerves happy - 90% of the central nervous system.

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10
Q

What do astrocytes do?

A

Maintain a good environment and protect the blood brain barrier.

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11
Q

what do oligodendrocytes do?

A

make myline sheaths

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12
Q

what do microglia do?

A

Phagocytotic hoover - mop up infection

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13
Q

What do ependyma cells do?

A

On surface - produce cerebral spinal fluid

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14
Q

name the three parts of the brain stem

A

midbrain
poms
medulla oblongata

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15
Q

what are the hypothalamus and the thalamus called together?

A

diencephalon

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16
Q

What causes the resting membrane potential -describe steps.

- 70v

A

Na K pump pumps 3 Sodium out and 2 potassium in. (charge still equal on both sides)
Leaky potassium channels cause potassium to leave the cell due to its concentration gradient.
Reaches equilibrium potential (when electrical gradient and conc gradient are exactly opposite and equal)
Should be -90 but its -70 due to a few other leaky channels E.g calcium etc.

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17
Q

What does the action potential do?

A

Transmits signals over a distance

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18
Q

what does the graded potential do?

A

decides when to fire the action potential

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19
Q

what does the resting membrane potential do?

A

Gets the cell ready to respond

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20
Q

If the extracellular potassium concentration increases - this causes depolarisation. (it will be less negative as outside is more negative). How does this fail to cause damage?

A

Blood brain barrier - network of blood vessels that can block substances. So the tight capillaries in the brain does not get affected - however, the heart might

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21
Q

there is a high level of potassium within the cell. What ions have a high level outside the cell?

A

Na +
Cl -
Ca 2+

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22
Q

When will an action potential fire?

A

If the threshold is reached -55v.

This occurs due to sodium channels opening - and sodium rushing into the cell down it’s concentration gradient.

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23
Q

What is an action potential? and what occurs after it?

A

A massive depolarisation
over shoot to about +30
Then repolarisation
Hyperpolarisation

24
Q

What is the purpose of the myline sheath?

A

Insulation - less current leaks out of the membrane so Na+ channels can be far apart . - faster signal

25
Q

Action potentials are not graded - they are all the same high (amplitude). So how does a bigger stimulus provide a bigger reaction?

A

More frequency - not amplitude - so there are more action potentials that spend more time above the threshold.

26
Q

Why can action potentials only travel forward??

A

refractory states - the ones that sodium has just depolarised are recovering.

27
Q

Action potentials self propagate - what does this mean?

A

they spread and promote themselves.

28
Q

lots of different axons work in a slightly different way. (Compound action potential??) How do big axons compare to small axons??

A

big axons - more sensitive to pressure and anoxia (lack of oxygen)
Small axons - More sensitive to local anaesthetic

29
Q

Are action potentials decremental or non decremental?

A

Non - decremental - do not loose steam as such

30
Q

graded potentials can summate. what does this mean?

A

they can add together - build up.
Integration to meet the threshold.

May be ISPS and ESPS - ISPS might cancel out ESPS - need to add them all up

31
Q

What is temporal summation and what is spatial summation?

A

Temporal - multiple from a single neuron

Spatial - multiple from different neurones

32
Q

What is an ESPS?

A

Excitatory post synaptic potential

33
Q

What is an ISPS?

A

Inhibitory post synaptic potential

34
Q

Where on the neurone would ESPS have a larger effect?

A

If they are closer to the axon hillock

35
Q

Are graded potentials decremental or non-decremental ?

A

Decremental - fade as u go along further away from the stimulus

36
Q

Name 4 different types of graded potentials and where they are found.

A

Pacemaker ps -in pacemaker tissue - they rymthically fire action potentials
Generator ps - at sensory receptors
Postsynaptic ps - at synapses
Endplate ps - at neuromuscular junctions

37
Q

How is the size of the stimulus accounted for in graded potentials??

A

Amplitude !!
Large stimulus = bigger amplitude

Large stimulus - more current flow - bigger potential

38
Q

Describe ESPS. (fast and slow)

A

fast - neurotransmitter opens channel. Na goes in, Potassium goes out. (more Na+ goes in)

slow - g protein coupled. shuts potassium leaky channels - slow depolarisation.

39
Q

Describe ISPS (fast and slow)

A

fast - neurotramitter opens channel - cl- goes in, cell hyper polarises.

slow - g protein opens potassium channel - potassium
goes comes out .

40
Q

what is a synapse?

A

Connection between one neurone and the other.

Or neuromuscular junction is between a motor neurone and a muscle fibre.

41
Q

is a chemical or an electrical synapse more common?

A

Chemical

42
Q

In vague terms - why does the muscle contract at the neuromuscular junction?

A

Action potential comes down the axon.
Passes across synaptic cleft.
Stimulates response in the SARCOLEMMA (cell membrane of the striated muscle fibre)
Muscle contracts.

43
Q

Describe the action potential going down the motor neurone and stimulating muscle contraction - in detail.

A

Action potential in motor neurone ,
Opens voltage gated calcium channels in the presynaptic terminal
This triggers fusion of vesicles
Acetylcholine is released
They diffuse across the synaptic cleft
They bind to aCH (nicotinic) receptors
This opens ligand gated Sodium potassium channels
This evokes a graded local potential - end plate potential
Depolarises adjacent membrane to the threshold
Opens voltage gated Na channels -
Action potential
Acetylcholinesterase removes Ach to stop the action potential.

44
Q

How do tetrodotoxin, jorospider toxin, botulinum toxic, curare affect the neuromuscular junction?

A

blocks the signal from occurring.

45
Q

How does anti cholinesterase work?

A

IT blocks the Ach breakdown - so increases the transmission at the NMJ.

46
Q

How does tetrodotoxin work?

A

Blocks Na+ channels - near the end of the process - action potential is not fired.

47
Q

How does toro spider toxin work?

A

It blocks the Ca+ channels at the start of the process - stops vesicle fusion and transmitter release

48
Q

how does botulinum toxin work?

A

disrupts the release machinery - transmitter is not released.

49
Q

How does curare work?

A

Blocks Ach receptors - end plate potential does not occur.

50
Q

how does the neuromuscular junction and the CNS synapses differ in terms of neurotransmitters?

A

CNS has lots of neurotransmitters with lots of receptors.
E.g Ach, ATP, Peptides, Dopamine, Seretonin, Histamine, Glycine etc.

neuromuscular junction - just has one

51
Q

Name a fast ESPS and A fast ISPS neutrannsmitter in the CNS synapse.

A

ESPS - Glutamate

ISPS - GABA

52
Q

How does the neuromuscular junction and the CNS synapse differ in terms of post synaptic potential .

A

Neuromuscular junction just has one end plate potential.

CNS hasFAST EPSP (ionotrophic - ligand gated)
FAST EPSP (metabotropic)
SLOW IPSP
FAST IPSP
this enables complex synaptic integration

53
Q

Central nervous system synapses have different arrangements. Name some.

A

Axo-Somatic
Axo-Dendritic
Axo-axonal

54
Q

CNS synapses display divergence and convergence. Do neuromuscular junctions do anything like this?

A

Only a tinnnnyyyy bit of divergence.

55
Q

CNS synapses also can do feedback inhibition, and can have monosynaptic and polysynaptic pathways. What do polysynaptic pathways lead too?

A

more modulation.

56
Q

Why do CNS system synapses have more synaptic integration?

A

They fire smaller potentials than Neuromuscular junction.

Science for Medicine Taz (14 decks)

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