Biology > Neuronal communication > Flashcards

Neuronal communication Flashcards

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1
Q

what is coordination in the body required for?

A
  • body systems to continue its function as most of the body cannot work in isolation
  • homeostasis
  • cell signalling
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2
Q

what is a stimulus?

A

any change in the environment of an organism that causes a response
- can be internal or external environment

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3
Q

what is a receptor?

A

a cell which detects a stimulus

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4
Q

what do receptors do?

A

convert energy from one form to another
- they are specific to the type of light energy they receive and then convert

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5
Q

where is the Pacinian capsule found?

A

in the skin dermis and in abundance in fingers and soles of feet

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6
Q

what does the Pacinian do?

A

detects mechanical pressure

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7
Q

what is an effector?

A

a muscle or gland that brings about a response

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8
Q

what is a response?

A

the change that occurs because of initial stimulus

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9
Q

what does the central nervous system consist of?

A

brain and spinal cord

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10
Q

what is the peripheral nervous system?

A

sensory and motor neurones connecting CNS to sensors and effectors around the body

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11
Q

what is a reflex?

A

fast, automatic response to a stimulus. it does not involve conscious thought

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12
Q

what are the three types of neurones?

A
  • sensory neurones
  • relay neurones
  • motor neurones
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13
Q

where do sensory neurones go between?

A

impulses from receptor to relay neurone/CNS

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14
Q

where do relay neurones go between?

A

impulses from sensory to motor neurones

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15
Q

where do motor neurones go between?

A

impulses from relay/CNS to effector

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16
Q

what do dendrites do?

A

connect to other neurones

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17
Q

what are key features of neurones?

A
  • long
  • voltage gated ion channels in the cell surface plasma membranes
  • sodium potassium pumps in the cell surface membrane
  • have a myelin sheath
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18
Q

what is a cell body?

A

contains nucleus and produces neurotransmitters

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19
Q

where do dendrons go between?

A

to cell body and axon away from cell body

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20
Q

what is myelination?

A

a fatty sheath around a neurone

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21
Q

what do myelination consist of?

A

many layers of the plasma membranes of schwann cells

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22
Q

what does myelination do?

A
  • insulates the neurone
  • increases the speed of action potential
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23
Q

what is a myelin sheath?

A

a series of schwann cells wrapped in layers around the axon

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24
Q

what are nodes of ranvier?

A

gaps at intervals along the neurone

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25
how many peripheral neurones are myelinated?
1/3
26
what do some degenerative diseases cause?
demyelination
27
what does white matter contain?
- nerve fibres - many axons and no dendrites
28
what does grey matter contain?
- mainly cell bodies - short axons
29
what is repolarisation?
a change in potential difference from positive back to negative across the membrane of a neurone
30
what is depolarisation?
a change in the potential difference from negative to positive across the membrane of a neurone
31
what is a refractory period?
after the action potential, there is a short period of time when the axon cannot be excited again
32
what is summation?
build up of neurotransmitters in a synapse to trigger sufficient levels to trigger an action potential
33
what is an example of positive feedback in a neurone?
change in the charge caused by the movement sodium ions into the axon causes more sodium ion channels to open, allowing more sodium ions to diffuse into the axon
34
what are neurotransmitters?
chemicals involved in communication across a synapse between adjacent neurones or a neurone and a muscle cell
35
what is a stimulus?
a detectable change in the external or internal environment of an organism
36
what is hyperpolarisation?
many potassium ions diffuse out of the axon resulting in the inside of the axon becoming more negative than its normal resting state
37
what is the definition of a myelin sheath?
a membrane rich in lipids which surround the axon of some neurones, speeding up impulse transmission
38
what is an effector?
a muscle or gland which carries out the body's response to a stimulus
39
what is a threshold value?
a certain level of stimulus always triggers a response. if this level is reached, an action potential will always be created
40
what is a voltage gated ion channel?
protein channels in the axon membrane that change shape as a result of the change in voltage across a membrane. this results in the channels opening or closing
41
what is a resting potential?
the potential difference across the membrane of the axon of a neurone at rest (-70MmV)
42
what is an action potential?
the change in the potential difference across the neurone membrane of the axon when stimulated (+40mV)
43
see IRL flashcard for a diagram of a motor neurone
/
44
see IRL flashcard for a diagram of a sensory neurone
/
45
what is the structural info and function of the cell body?
- animal cell - organises and keeps the cell functional
46
what is the structural info and function of the dendron?
- extensions of the cytoplasm - transfers signals to other cells and organs
47
what is the structural info and function of the axon?
- extensions of cytoplasm - transfers signals to other cells and organs
48
what is the structural info and function of the myelin sheath?
- made of schwann cells - increases the the speed of the signal
49
what is the structural info and function of the nerve muscle?
- dendrite meets muscle - joins dendrite to muscle
50
what is the structural info and function of the sensory receptors?
- specialised cells - detects change in the environment
51
what is the structural info and function of the dendrites?
- extensions of the cell body - receive signals
52
see IRL flashcard for diagram of schwann cells
/
53
what are neyrones organised into and what are they surrounded by?
organised into bundles and surrounded by a perineurium
54
what is the difference in charge due to in resting potential?
due to the movement of ions across the membrane
55
how is resting potential maintained? see irl flashcard for diagram
1) sodium potassium pumps actively transport - 3 Na+ out of the axon - 2 K+ into the axon - uses ATP 2) the surplus of positive ions on the outside makes it more positive on the outside - polarised 3) K+ ion channels are open in the membrane 4) K+ ions diffuse out of the membrane down their electrochemical gradient 5) increasing the positive charge on the outside of the membrane 6) most of the voltage gated sodium ion channels are closed 7) sodium is not able to diffuse back into the axon 8) further maintaining the positive charge on the outside of the membrane
56
what is the role of glycoproteins in the cell surface membrane?
- cell signalling - cell adhesion - receptors for neurotransmitters or peptide hormones
57
glycolipids are similar to _____________. They are lipids with attached ____________ chains. Theses molecules called cell markers or ________ can be recognised by cells of the immune system as self or non self
- glycoproteins - carbohydrates - antigens
58
how does the presence of cholesterol molecules stabilise plasma membranes?
- stops proteins gathering together in one space and crystallising - regulates fluidity - pulls phospholipids together - prevents it becoming too solid
59
what is the structure of channel proteins?
hydrophobic R group on external surfaces
60
what is the structure of carrier proteins?
hydrophobic R group on external surface
61
what is the function of channel proteins?
facilitated diffusion
62
what is the function of carrier proteins?
active and passive transport
63
what is the structure of extrinsic proteins?
- only go through one layer of the membrane - hydrophilic R groups on outer surfaces and interact with polar heads of phospholipids or with intrinsic proteins
64
what is the all or nothing response?
when a receptor detects a stimulus, there needs to be enough energy to generate an action potential. a stimulus that reaches the threshold potential will always generate an action potential. if the threshold potential is not reached, there is no action potential generated
65
where is the threshold value for the all or nothing response?
when the membrane is depolarised to -50mv/-40mv
66
what happens to the all or nothing response if there is a smaller or larger stimulus?
no matter the size of the stimulus, the action potential will always be the same size, a larger stimulus just increases the frequency of the action potentials generated
67
what are the stages in transmission of an action potential?
1) polarised- resting state -65mv/-70mv - sodium potassium pump is working - K+ ion channels open, Na+ ion channels closed 2) Na+ voltage gated channels open - energy from stimulus opens Na+ voltage gated channels so membrane becomes more permeable to Na+ ions 3) threshold potential -40mv/-50mv - if enough Na+ diffuse down electrochemical gradient, threshold potential is reached 4) depolarisation +40mv - Na+ flood into axon which causes depolarisation - Na+ cause more Na+ ion channels to open (pos feedback) 5) repolarisation - at +40mv Na+ voltage gated channels close and K+ voltage gated channels open - K+ ions flood out down electrochemical gradients via diffusion 6) hyperpolarisation -75mv - potential difference overshoots so the PD is more negative on the inside compared to the resting state 7) resting state -65mv/-70mv - K+ voltage gated channels shut - Na+/K+ pump works again to restore resting potential
68
what happens in the propagation of action potentials?
- a stimulus causes a sudden influx of sodium ions causing the depolarisation of the axon membrane - the depolarisation acts as a stimulus for the next region of the axon, causing voltage gated sodium ion channels to be opened - this region is now depolarised - as the next region becomes depolarised the voltage gated sodium ion channels and the voltage gated potassium ion channels open. this region is now said to be repolarised - ATP continues to be propagated along the axon and the repolarised region of the axon membrane causes the forward, unidirectional propagation of the action potential - following the repolarisation of the membrane, voltage gated potassium ion channels close and the resting potential is restored
69
what is the refractory period?
a short period of time when an action potential can not be generated
70
why does the refractory period happen?
the sodium ion channels are closed and can not be stimulated to open immediately
71
why do synaptic knobs contain many mitochondria?
to meet significant energy demands the neurotransmitter release and synaptic transmission
72
describe how the arrival of an impulse at the synapse causes depolarisation of the post synaptic membrane?
it triggers the release of neurotransmitters into the synaptic cleft. these neurotransmitters then bind to the receptors on the post-synaptic membrane, causing ion channels to open
73
how does the post synaptic membrane become repolarised?
when excitatory neurotransmitters bind to their receptors, causing ion channels to open and allow positively charged ions like sodium and calcium to flow
74
see IRL flashcard for diagram of Pacinian corpuscle
75
list the order of events when pressure is applied to the skin leading to an action potential being generated?
1) pressure is applied to the skin 2) Pacinian corpuscle goes out of shape, causing the membrane to stretch 3) sodium ion channels open 4) sodium ions diffuse into the neurone 5) action potential is generated if enough sodium flows in -> the more pressure applied, the more sodium ions diffuse
76
see IRL flashcard for diagram of reflex arc
77
distinguish between a monosynaptic and a polysynaptic reflex arc and give an example for each?
monosynaptic- involves only one CNS synapse (knee jerk reflex) polysynaptic- 2 or more CNS synapses (pain withdrawal reflex)
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