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Neurons and Synapses > Neurons and Synapses > Flashcards

Neurons and Synapses Flashcards

1
Q

What is a Neurone

A

a specialised single nerve cell transmitting impulses

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2
Q

What is a synapse

A

A site of communication between two neurones

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3
Q

What is a neurotransmitter

A

A chemical released by a neurone which causes an effect at another cell

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4
Q

What is a membrane potential

A

the difference in electric potential between the interior and the exterior of a biological cell OR the electrical charge across a cell membrane.

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5
Q

Approximately how many neurones does the brain have

A

100,000,000,000

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6
Q

what are nerve impulses

A

are changes in membrane potential that travel down a nerves

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7
Q

What is a cell membrane made up of and what is it highly impermeable to

A

Made up of fat and is highly impermeable to ions

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8
Q

Membrane potential is a result of what

A

Ion gradient (unequal ion distribution)

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9
Q

why cant ions cross the cell membrane

A

cell membrane composes of fat and fat and ions don’t mix well

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10
Q

what is a passive diffusion

A

movement of substances across the cell membrane from an area of high concentration to lower concentration - no energy is needed to move molecules across membrane. Examples include oxygen, carbon dioxide, ethanol and weak acids/bases - these diffuse straight across the cell membrane

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11
Q

What is a Facilitated Diffusion

A

The process of passive transport of molecules or ions across a biological membrane via specific transmembrane integral proteins – does not require energy. Used by molecules which are large such glucose, sodium and potassium ions, Cl, Ca2+, H2O polar molecules – uses ion channel which is a hole through a membrane formed by a protein and only allows specific substances – transports substances down their gradient

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12
Q

What is active transport

A

the movement of molecules across a membrane from a region of lower concentration to a region of higher concentration—against the concentration gradient. Active transport requires ATP to achieve this movement. For example, Calcium, Sodium + Potassium

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13
Q

neurones (nerve cells) transmit information as what

A

electrical signals (nerve impulses or action potential)

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14
Q

which direction does action potential travel

A

travels one way from dendrites to axons

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15
Q

what happens when action potential or electrical signal reaches the axon terminal

A

Releases neurotransmitter

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16
Q

what does the axon terminal do

A

communicates with other neurones/muscles etc

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17
Q

what is action potential and what is ion gradient

A

Name for electrical impulse that travels along the neurone and is formed by the changes in ion gradient -movements of ions from outside the neurone to the inside of the neurone

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18
Q

Signals received at the dendrites causes what

A

Dendritic Depolarisation

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19
Q

At rest neurones are what

And what is polarisation

A

At rest neurones are polarised
polarisation -outside of the membrane is positively charged and the inside of the membrane is negatively charged - has negative membrane potential

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20
Q

What is depolarisation

and what channels does it open

A

The state which the cell membrane change from positive to negative charge outside the cell and from negative to positive charge inside the cell.
Depolarisation opens voltage gated sodium channels

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21
Q

Whats the most common excitatory neurotransmitter in the brain

A

Glutamate

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22
Q

whats the threshold potential

A

-55 mV

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23
Q

what happens when the stimulus does or doesn’t pass the threshold potential

A

does pass - the cell is depolarised enough and fires action potential if the stimuli isn’t big enough it wont fire AP.

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24
Q

what does the threshold mean

A

the amount of depolarisation required to open the first voltage gated sodium channel

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25
Q

the change in voltage from -55 to +40 mV causes which channels to open

A

voltage gated potassium channels

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26
Q

what us a refractory period

A

The cell cant fire AP again - because it has sodium inside cell and potassium outside in order to fire AP, whereas it needs Na outside and K inside in order to fire AP

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27
Q

What is myelination

A

the wrapping of a fatty substances around the axons of the neurones

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28
Q

By which cells does myelination happen in the CNS

A

oligodendrocytes

29
Q

By which cells does myelination happen in the PNS

A

Schwann cells

30
Q

During myelination, what are the small sections of the axons called which are left exposed and what does it do

A

Node of Ranvier -speeds up neurotransmission and makes it makes energy efficient.

31
Q

How does myelination speed up neurotransmission

A

It’s speeded up by a process called saltatory conduction.

32
Q

•Axons in most vertebrate neurones are myelinated – mostly covered in which substance

A

myelin

33
Q

which voltage gated channels are found are found at the nodes of ranvier

A

voltage gated sodium channels

34
Q

what is saltatory conduction and why does it happen

A

Action potential jumps from one node to the next- missing out large sections of the axon – which increases the speed of neurotransmission
it does this because when one voltage gated sodium channel opens – the myelin is highly insulating, it can’t store charge.

35
Q

In the absence of myelination, neurotransmission/ action potential speed is determined by what

A

the diameter of an axon

36
Q

What happens when an action potential reaches an axon terminal

A

the depolarisation causes voltage-gated calcium ion channels to open, calcium ions flood in to the synaptic terminal, which causes vesicles(contains neurotransmitters) to fuse with the presynaptic membrane which causes the neurotransmitter to be released into the synapse (gap between one neurone and the next cell or neurone).

37
Q

vesicles at the presynaptic membrane contain what

A

neurotransmitters

38
Q

what can be found at the presynaptic membrane

A

mitochondria, calcium ion channels, vesicles , neurotransmitter re-uptake pump

39
Q

*Which channels cause neuronal depolarisation

A

Sodium Channels

40
Q

*which channels cause neuronal Repolarisation

A

Potassium channels

41
Q

what is the nerst equation used for

A

calculation of the membrane potential of an ion

42
Q

what is post-synaptic density

A

Collection of proteins which forms the structure of the post-synapse and allows neurotransmitter receptors to be position in the right place to receive neurotransmitter release at the pre-synapse.

43
Q

*Name all the excitatory neurotransmitters

A

glutamate - in brain
acetylcholine -responsible for inhibiting signals exchanged by the nerve cells.
Monoamines - important in brain they are - dopamine, serotonin, noradrenaline

44
Q

*Name all the inhibitory neurotransmitters

A

GABA - in brain - contributes to motor control, vision
Glycine - important in PNS
endorphines - pain relief

45
Q

*what are the two basic types of neurotransmitter receptors and give example of them

A

1) Ionotropic: works by binding a neurotransmitter to a receptor at the post-synaptic receptor which opens voltage gated channel – if ions are positive = depolarisation and activation of post-synaptic cell, if negative = they cause hyperpolarisation and inactivation of post-synaptic cell. Their responses are faster. Glutamate, GABA, glycine.
2) Metabotropic do not have channels. Metabotropic receptors activate a G-protein that in turn activates a secondary messenger, that in turn will activate something else: Monoamines and Histamines

Some have both kinds such as GABA and glutamate

46
Q

Function of (Multipolar (motoneuron)

A

Receives dendritic inputs from different sources and that determines whether they fire action potential or not e.g. motoneuron

47
Q

Function of (Unipolar (sensory neurone)

A

In addition to pain and touch, they also carry information about temperature, taste. E.g. sensory neurones

48
Q

function of Bipolar (interneuron)

A

carries info from one neurone to another, interneuron can be excitatory or inhibitory

49
Q

what percentage of the brain does glial cells make up

A

60%

50
Q

Name all glial cells

A

Astrocytes, microglia, oligodendrocytes

51
Q

where are Glial Cells found

A

CNS (brain and spinal ord)

52
Q

Roles of Astrocytes

A
  • Outnumbers neurones + main role is support
  • site of communication between blood vessels + neurones
  • forms important part of the blood-brain barrier
  • takes nutrients from the blood to the neurones
  • takes waste products from neurones back to the blood
  • forms scar tissue when you have brain damage
  • role in regulating synaptic stability: tripartite synapse – three parts – pre-synapse, post-synapse and astrocyte
53
Q

Role of Microglia

A

brains own immune system sort like macrophages found in the CNS

54
Q

Role of Oligodendrocytes

A
  • produces myelin sheath – surrounds axons – can myelinate many axon
  • Schwann cell can only myelinate on axon and only found in periphery- both does this by wrapping around its membrane around the axons forming a fatty sheath around the axons – leaving the rod of Ranvier exposed allowing saltatory conduction
55
Q

what is neuromuscular junction

A

site of chemical communication between a nerve fibre and a muscle cell. In other words – specialised synapse at either skeletal muscle in the somatic nervous system or a smooth muscle in the PNS.

56
Q

what are the two basic types of neurotransmitters

A

excitatory and inhibitory

57
Q

Apart from neurones, which other cells are in the brain

A

astrocytes , oligodendrocytes and microglia

58
Q

What are the features of a smooth muscle NMJ

A

1) Metabotropic receptors
2) Under autonomic control - entirely involuntary
3) Neurotransmitters include: acetylcholine, noradrenaline, adrenaline

59
Q

What are the features of skeletal muscle NMJ

A

1) Ionotropic receptors
2) Under somatic control - controls voluntary muscle
3) Acetylcholine as neurotransmitter

60
Q

Which muscle is controlled by at the PNS and SNS

A

SNS - skeletal muscle

PNS - Smooth muscle

61
Q

At Skeletal muscle NMJ - by what is the signal ended

A

Acetylcholinesterase

62
Q

At skeletal muscle muscle NMJ - why is the receptor called nicotinic acetylcholine receptor

A

Because the chemical nicotine binds to and activates it in the same way acetylcholine does

63
Q

which NMJ is important pharmacological target

A

Smooth muscle NMJ

64
Q

Features of SNM

A

1) part of the PNS
2) Comprises of spinal nerves
3) controlled by the brain

65
Q

What receives sensory information from the SNS

A

Somatosensory Cortex

66
Q

what controls motor neurones and skeletal muscle movements

A

Motor cortex

67
Q

How does the somatosensory cortex + motor cortex communicate with the PNS

A

Via ascending and descending tracts

68
Q

what does the ascending tract and the descending tract do

A

1) Relays sensory information from the spinal cord to the sensory cortex using sensory neurones
2) relays information from the motor cortex spinal cord using motor neurones

Neurons and Synapses (3 decks)

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