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module 5 – communication, homeostasis & energy > 5.3 Neuronal communication > Flashcards

5.3 Neuronal communication Flashcards

1
Q

What is a synapse

A

Junction between two neurones

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2
Q

What chemical transmit impulses across synapse

A

Neurotransmitters

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3
Q

What is the function of synapses

A

Electrical impulses that cannot cross junction
Neurotransmitters send impulses between neurones/from neurones to effectors for excitatory or inhibitory response
Summation of sub threshold impulses

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4
Q

Describe the structure of a synapse

A

Presynaptic neurone ends in synaptic knob- lots of mitochondria, ER and vesicles of neurotransmitters
Synaptic cleft- gap which separates the axon of one neurone from the dendrite of the next neurone

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5
Q

What happens in the presynaptic neurone when an action potential is transmitted between neurones

A

Wave of depolarisation travels down presynaptic neurone, causing voltage gated calcium channels to open
Vesicles move towards and fuse with presynaptic membrane
Exocytosis of neurotransmitter into synaptic cleft

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6
Q

How do neurotransmitters cross the synaptic cleft

A

Simple diffusion

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7
Q

What happens in the postsynaptic neurone when an action potential is transmitted between neurones

A

Neurotransmitter binds to specific receptor on postsynaptic membrane
Sodium ion channels open
If influx of sodium ions raises membrane to threshold potential,action potential is generated.

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8
Q

What features are common to all sensory receptors

A

Act as energy transducers which establish a generator potential
Respond to specific stimuli

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9
Q

Describe the features of all neurones

A

Cell body - contains organelles and high proportion of RERR
Dendrons- branch into dendrites which caddy impulses towards the cell body
Axon - long,unbranched fibre carries nerve impulses away from cell body

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10
Q

Describe the structure and function of a sensory neurone

A

Usually unipolar

Transmits impulses from receptors to CNS

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11
Q

Describe the structure and function of a relay neurone

A

Usually bipolar

Transmits impulses between neurones

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12
Q

Describe the structure and function of a motor neurone

A

Multipolar

Transmits impulses from the relay neurones in the CNS to effectors

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13
Q

Describe the additional features of a myelinated neurone

A

Schwann cells- Wrap around axons
Myelin sheath- made from myelin rich membranes
Nodes of Ranvier- very short gaps between neighbouring Schwann cells where there is no myelin sheath

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14
Q

What 3 process Schwann cells are involved in

A

Electrical insulation
Phagocytosis
Nerve regeneration

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15
Q

What is resting potential

A 
Potential difference(voltage) across neurone membrane when not stimulated
Usually about -70mV in humans
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16
Q

How is resting potential established

A

Membrane is more permeable to K+ than Na+
Sodium potassium pump actively transports 3Na+ out of cell and 2k+ into cell
Requires ATP energy from respiration

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17
Q

Name the stages in generating an action potential

A

Depolarisation
Repolarisation
Hyper polarisation
Return to resting potential

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18
Q

What happens during de polarisation

A

Stimulus -> causes facilitated diffusion of sodium ions into cell down electrochemical gradient
p.d across membrane becomes more positive
If membrane reaches threshold potential of -50mv voltage gates Na+ channel opens

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19
Q

What happens during REpolarisation

A

Voltage-gated sodium ion channels close and voltage-gates K+ channel open
Facilitated diffusion of K+ ions out of cell down their electromechanical gradient
p.d across membrane becomes more negative

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20
Q

What happens during hyperpolarisation

A
  1. ‘Overshoot’ when K+ ions diffuse out =
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21
Q

What is resting potential

A

Resting axon on where the inside of axon always have a negative electrical potential compared to the outside of axon

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22
Q

What is the potential difference of resting potential

A

-70mV

Lower than the outside of the axon

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23
Q

What two factors are considered for the establishment of resting potential

A

Active transport of sodium and potassium ions

Differential membrane permeability

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24
Q

Explain the process of the AT of sodium and potassium ions

A

Uses carrier protein called sodium and potassium pump, present in membranes of neurone
Uses ATP , 3 sodium ions out for every 2 potassium ion in
More positive ions outside the axon
Creates electrochemical gradient

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25
Q

Explain the differential membrane permeability have on resting potential

A

Allow sodium and potassium ion to move via facilitated diffusion
Protein channels less permeable to sodium ions then potassium ions
Potassium faster rate > sodium

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26
Q

What is action potential

A

Occurs via a brief change in the distribution of electrical charge caused by rapid movement of sodium and potassium ion across axon membrane

Action potentials travel as a wave of depolarisation across the length of the neurone.

27
Q

What happens into transmission along an axon

A

An action potential triggered in the neurone causes depolarisation of that section of the axon
Opening of sodium ion channels, influx generating an action potential
Previous section of the axon is in the repolarisation stage
Makes action potential discrete, impulse can only travel one direction

28
Q

Define the channel proteins that allow sodium or potassium ions or diffuse through the cell membrane

A

Voltage gated channel proteins
Depending on electrical potential
Closed when axon membrane is in resting potential

29
Q

What happens after the action potential has been initiated in the neurone

A

Depolarisation moves in one direction along the entire length of an axon like a wave

30
Q

What goes on in the transmission of electrical impulses along an axon

A

The action potential(AP) causes depolarisation of the section of the axon
Current causes sodium ion channels causes an influx of sodium, generating an AP
Previous section of axon in repolarisation (closing of sodium ion channel,opening of potassium ion)
Travels in one direction,discrete

31
Q

What is the all or nothing principle

A

Impulse is only transmitted if the initial stimulus is sufficient to increase the membrane potential above a threshold potential

32
Q

What happens if the stimulus is weak

A

The receptor cells won’t be sufficiently depolarised as a result the sensory neurone will not be depolarised

33
Q

What faceless affect the speed of conduction across a neurone

A

Myelination
Diameter of an axon
Temperature

34
Q

How does diameter affect the speed of conduction

A

Impulses will be conducted at a higher speed along with a thicker axon as they will have an axon membrane, greater SA, greater rate of diffusion via protein channels

35
Q

How does temperature affect the speed of conduction

A

Cooler temperature means there is less kinetic energy available for facilitated diffusion of potassium and sodium ions

36
Q

What is a summation

A

Sometimes impulses is insufficient to generate an action potential in the post synaptic neurone, therefore the effect of multiple impulses can be added to gen an action potential

37
Q

What are the benefits of summation

A

Effect of a stimulus can be magnified
Combination of different stimuli can trigger a response
Avoids the NS to being overwhelmed

38
Q

What are the 2 types of summation

A

Temporal and spatial

39
Q

Temporal

A

Multiple impulses arrive within quick succession

40
Q

Spatial

A

Multiple impulses arriving simultaneously at different synaptic knobs

41
Q

What does excitory neurotransmitters have an effect on the post synaptic neurone

A

Stimulate the generation of an action potential by opening the sodium ion channels in the post synaptic membrane, causing depolarisation

42
Q

What affect does inhibitory neurotransmitter

A

Prevent the generation of an action potential

Opening of potassium ion channels in the post synaptic membrane resulting in hyper-polarisation

43
Q

What is the cell membrane of muscle fibres and the muscle cells cytoplasm

A

Sarcolemma

Sarcoplasm

44
Q

How are transverse tubles made

A

Bits of sarcolemma fold inwards across the muscle fibre and stick into the sarcoplasm. These folds are called T tubles and spread electrical impulses throughout the sarcoplasm to reach parts of muscle fibre

45
Q

What do muscle fibres contain

A

Sarcolemma
Sarcoplasm
Sarcoplasmic reticulum
Myofibrils

46
Q

What do myofibrils contain

A

Thick myosin filaments - A bands
Thin actin filaments - I bands
Many short units called sarcomere

47
Q

What are the features of a MYOSIN filaments

A

Globular heads that are hinged

Binding site for actin and for ATP

48
Q

What are the features of an actin filament

A

Binding site for myosin
2 other proteins called tropomyosin and troponin are found between actin filaments. Proteins attach to each other and help myofilaments move past each other

49
Q

What occurs in the myofibrils when at rest

A

Muscle actin myosin binding site is blocked by tropomyosin

Held in place by troponin

50
Q

List the 5 structures of the brain

A

Hypothalamus - controls body temperature
Cerebrum - allows you to see,hear, learn and think
Pituitary gland - controls hormone release by body glands
Medulla Oblongata - controls BR and HE
Cerebellum - co ordinates muscle,balance and posture

51
Q

Which part of the nervous systems controls unconscious activities

A

Autonomic nervous system e.g digestion

52
Q

Explain the process of muscle contraction

A

Action potential from motor neurone,stimulates a muscle cell,depolarises sarcolemma
Spread down t tubles to the sarcoplasm reticulum
SR releases stored calcium ions into the sarcoplasm
Calcium ion binds onto troponin,change shape
Pulls out tropomyosin out
Exposes binding site
Calcium ions activate ATPase which breaks down ATP for muscle contraction
Provides energy to break actin myosin cross bridge

53
Q

State one internal factor which causes a response in: plant and animal

A

water potential in plant cells Blood pH

54
Q

Describe how cells are able to communicate with one another

A

Cells releases a chemical which has an effect on a target cell

55
Q

how and why is co ordination is required in multicellular organisms

A

Organism needs to respond to internal/external changes for survival
Occurs by electrical impulses/nervous system in animals
Different organs work together to ensure homeostasis e.g brain and skin in temperature control
Cells communicate through cell signalling

56
Q

State the difference between the function of a motor and a sensory neurone

A

sensory neurone transmit impulses to the CNS/from receptor whereas motor neurones transmit impulses from the CNS to an effector

57
Q

Describe the difference between a myelinated and non myelinated neurone

A

Axon of a myelinated neurone is covered in myelin, Electrical insulator, sheath is formed formed by Schwann cells, gaps in the myelin sheath known as nodes of Ranvier, saltatory conduction, impulse transmits much faster

58
Q

Describe the role of a sensory receptor in the body

A

Detect stimuli, convert energy into a nervous impulse

59
Q

State the transformation that takes place in a cone cell

A

Light energy is converted into a nervous impulse/action poetical

60
Q

Explain how your body detects that your finger has touched a pin

A

Touch pin -> exerts mechanical pressure on your skin, pacnian corpuscle found within skin detects pressure -> changes shape of Pacinian corpuscle -< stretch mediates sodium channel in neuronal membrane stretches -> channel widens -> sodium ion diffuse into a membrane -> membrane is depolarised/ generator potential created

61
Q

State how the body detects the difference between a small and a large stimulus

A

The larger the stimulus the more frequent the nerve impulse/action potential

62
Q

State the difference between depolarisation,repolarisation and hyper polarisation

A

Depolarisation – voltage/potential difference becomes more positive; repolarisation – voltage/potential difference becomes more negative hyperpolarisation – when potential difference is lower than resting potential

63
Q

Describe what would happen if a refractory period did not exist

A

The axon could be immediately depolarised after an action potential (1); therefore the action potential could travel backwards / in both directions / not reach target cell (1)

64
Q

Describe how the movement of ions establishes an action potential

A

Resting potential: sodium potassium pump actively transports sodium and potassium ions, 3 NA+ move out 2 KA+ move in, ka + can diffuse through potassium ion channels, sodium ions can not
More positive ions outside than inside the axon

module 5 – communication, homeostasis & energy (6 decks)

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