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Science for Medicine > Nerves > Flashcards

Nerves Flashcards

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Biology 101 flashcards
1
Q

What is a soma?

A

Cell body, contains the nucleus

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2
Q

What is the function of dendrites?

A

Transfer information between neurones

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3
Q

What is the function of the initial segment?

A

Arranges all the information for making action potentials

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4
Q

What is the function of an axon?

A

Takes the action potential elsewhere

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5
Q

What is the function of axon terminals?

A

Transfers the action potentials to other nerves or muscles. They relates neurotransmitters

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6
Q

What is the typical value of the resting membrane potential?

A

-70mV

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7
Q

What generates the resting membrane potential?

A

Na+/K+ pump and K+ specific ion channels

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8
Q

What is the function of the Na+/K+ pump?

A

Separates Na+ and K+ by pumping K+ into the cell and Na+ out

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9
Q

What is the function of K+ specific ion channels?

A

They allow K+ to flow down their concentration gradient by facilitated diffusion, which creates an electrochemical gradient which pulls the K+ back into the cell. Equilibrium is eventually reached

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10
Q

Why is the resting membrane potential -70mV and not -90mV?

A

Leaky channels and the membranes permeability depolarise the cell slightly

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11
Q

What are graded potentials?

A

They are decremental potentials which are denoted by their amplitude and can only travel over short distances. Their intensity varies with the intensity of the stimulus. They can be inhibitory or excitatory and can undergo temporal or spatial summation

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12
Q

What does inhibitory mean?

A

Hyperpolarisation

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13
Q

What does excitatory mean?

A

Depolarisation

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14
Q

What determines wether or not a graded potential is inhibitory or excitatory?

A

Which channels are open

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15
Q

What is temporal summation?

A

Intense stimulation form one presynaptic neurone which causes EPSPs to spread from one synapse to a trigger zone

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16
Q

What is spatial summation?

A

Simultaneous stimulation by several presynaptic neurones which causes EPSPs to spread from several synapses to a trigger zone

17
Q

How do neurones communicate?

A

Action potentials

18
Q

What is required before an action potential can be fired?

A

The graded potential must reach a significant level

19
Q

What are action potentials?

A

Large all or nothing signals that can self-propagate, which are denoted by their frequency

20
Q

What is the process by which action potentials function?

A

An action potential is fired when a graded potential reaches the correct threshold. This causes the charge of the neurone to change to +40mV., which opens voltage gated Na+ channels which causes Na+ to come rushing through the membrane. This causes great depolarisation which cases K+ channels to open. This results in repolarisation followed by hyperpolarisation

21
Q

What is self-propogation?

A

The charge due to the large increase in Na+ spreads up the axon which opens channels along the axon which caused further influx and propagation of the signal

22
Q

What are afferent neurones?

A

They are sensory neurones that detect changes or sensory stimuli

23
Q

What are interneurones?

A

They are contained with the spinal cord and decide what to do with the stimulus

24
Q

What are efferent neurones?

A

They are motor neurones that carry the signal to effector tissue or cells if the interneurones decides an excitatory response is needed

25
Q

What is conduction velocity?

A

The speed of nerve transmission

26
Q

What increases connection velocity?

A

Larger axons and myelination

27
Q

Why do lager axons have a large conduction velocity?

A

They have less resistance so the charge can travel further up the axon when Na+ channels are open so there are less Na+ channels which take up a lot of time in order to open

28
Q

How does myelination increases conduction velocity?

A

It causes saltatory propagation which increase conduction by providing insulation so the signal can travel further

29
Q

What is myelin?

A

It is a lipid sheath that surrounds the axon which is formed from Schwann cells.

30
Q

Where are the Na+ channels found in myelin?

A

In the nodes of Ranvier between the sheath

31
Q

What replaces Schwann cells in the CNS?

A

Ogliodendrocytes

32
Q

What are the affects of demyelination?

A

Rapid decay of action potentials which prevents them from reaching the next node and prevents them from propagating. This results in failure of conduction

33
Q

How is a neuromuscular junction formed?

A

When the motor end plate form the neuronal axon comes to the muscle and forms a synapse

34
Q

What is the sarcolemma?

A

A post-synpatic membrane that consist of junction folds which holds ACh receptors which allows deeper contractions

35
Q

What is the function of the neuromuscular junction?

A

Muscle contraction

36
Q

How do neuronal synapses differ from the NMJ?

A

Wide range of neurotransmitters, range of postsynaptic fibres, anatomical arrangement and synaptic connectivity

37
Q

What are the range of postsynaptic fibres?

A

Fast/slow EPSPs and IPSPs

38
Q

How are synapses anatomically arranged?

A

Axo-somatic, axo-dendritic and oxo-axonal

39
Q

What are the 2 different ways in which synapses connect?

A

Convergence and divergence

Science for Medicine (19 decks)

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