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Gymnastics and tumbling > Chapter 26 (The nervous system) Neurones part > Flashcards

Chapter 26 (The nervous system) Neurones part Flashcards

1
Q

Function of cell body?

A

Contains nucleus surrounded by cytoplasm
Cytoplasm contain large number of ER and mitochondria for production for neurotransmitters.
Also contains other cell organelles

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2
Q

Function of dendrons?

A

Short extensions of the cell and cytoplasm from the cell body
Increase SA to receive nerve impulses from other neurones into the cell body.
Subdivide into smaller branches - dendrites
Function - transmit electrical impulses towards cell body.

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3
Q

Function of axons?

A

Singular, elongated nerve fibres extending from cell body.
Transmits impulses away from cell body
Surrounded by plasma membrane.

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4
Q

Definition of an action potential?

A

The change in electrical potential associated with the passage of an impulse along the membrane of a neurone.

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5
Q

What is a resting potential?

A

When a neurone is not transmitting an action potential there is a potential difference across the membrane of the neurone during the resting period. ~ -65mV

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6
Q

What is a generator potential?

A

(receptor potential)
A stationary depolarisation of a receptor that occurs in response to a stimulus

not finished

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7
Q

What is an action potential?

A

The change in the electrical membrane which causes the transmission of a nerve impulse.

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8
Q

What is an impulse?

A

..ghghgh

NOT FINISHED

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9
Q

Function of sensory neurone?

A

Carry impulse from receptor to relay neurone

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10
Q

Function of relay neurone?

A

Carries impulse from sensory neurone to motor neurone

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11
Q

Function of motor neurone?

A

Carries impulse from relay neurone to effector

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12
Q

What is a reflex?

A

Rapid automatic response to a stimulus that aids survival by protecting body from harm or damage.
no conscious thought involved.
Involuntary response
Simplest nerve pathway

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13
Q

What is a reflex arc

A

Nervous pathway

stimulus -> receptor -> sensory neurone -> relay neurone -> motor neurone ->effector cell

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14
Q

Different types of reflex arc?

A

Spinal reflex
Involves spinal cord (as coordinating part of CNS)
eg, knee jerk, removal of hand from hot object

Cranial reflex
Involves lower genre of brain but not spinal cord
Eg, iris reflex, blinking, salivation

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15
Q

What is the plantar reflex?

A

Used as diagnostic tool.
Reflex occurs when sole of foot is stimulated with blunt instrument or finger.
Normal response - foot flexes downwards
Abnormal response - foot flexes upwards (indicates brain or spinal cord damage/ disease of spine/damage to specific nerves in leg.

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16
Q

Blink reflex information?

A

Blinking reflex is one of last to be lost as person becomes unconscious. Indicates a coma.

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17
Q

Pupillary Light reflex (PLR) or photo pupillary reflex information?

A

Reflex occurs when light shone into eye.
Normal response - both pupils constrict to same degree
Abnormal response - pupils constrict differently, indicates possible brain/optic nerve damage.

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18
Q

Advantages of reflexes?

A

Involuntary
- Decision-making parts of brain not involved, so brain can deal with more complex responses.

Does not have to be learnt

  • Present at birth
  • Provide immediate protection

Extremely fast

  • Reflex arc is very short
  • Only 1 or 2 synapses
  • so Less delay caused by chemical NT diffusion
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19
Q

What is the myelin sheath?

A

Found on neurones within PNS
Axons have Schwann cells wrapped around them, and if wrapped many times, they produce multiple layers of plasma membrane called the myelin sheath.

20
Q

Purpose of myelin sheath?

A

Insulating layer impermeable to sodium and potassium ions.
Small gaps between adjacent Schwann cells - Nodes of Ranvier. They are the site of depolarisation and allow movement of Na+ and K+ ions.
Enables saltatory conduction
Results in faster conduction of nerve impulse.

21
Q

What happens if there was no myelin sheath?

A

No insulation - axon becomes permeable to Na+ and K+ - no saltatory conduction occurs - slower transmission

22
Q

Why do action potentials travel faster in myelinated neurones?

A
  1. Myelinated axons transfer electrical impulses faster than non-myelinated neurones
  2. Depolarisation only occurs at Nodes of Ranvier
  3. At Nodes of Ranvier Na+ ions pass through protein channels
  4. The action potential jumps to the next adjacent node
  5. It takes time for the channels to open and ions to diffuse across the membrane, so if areas where there are no channels - less channels have to open
  6. So speed of action potential transmission is sped up.
23
Q

Examples of neurotransmitters

A 
Acetylcholine
Noradrenalin
Glutamate
Serotonin
GABA
24
Q

Types of postsynaptic potentials?

A

Excitatory postsynaptic potentials

Inhibitory postsynaptic potentials

25
Q

What are excitatory postsynaptic potentials?

A

Increase likelihood of AP occurring
NT causes membrane to become less negative and closer to threshold value.
Eg, glutamate - open. Na+ channels in postsynaptic membrane - Na+ ions enter.

26
Q

What Inhibitory postsynaptic potentials?

A

Decrease likelihood of AP OCCURRING.
NT causes membrane to become more negative and further away from threshold, ie hyperpolarises postsynaptic membrane)
EG, GABA, open K+ channels in postsynaptic membrane - K+ ions leave post synaptic neurone.

27
Q

Types of NT?

A

Excitatory
- NT results in depolarisation of postsynaptic neurone
- if threshold is reached in postsynaptic membrane, an action potential is triggered
Eg, acetylcholine

Inhibitory
-NT results in hyperpolarisation of postsynaptic membrane
- Prevents action potential being triggered
Eg, GABA, glutamate.

28
Q

What is a synapse?

A

A junction between 2 neurones (or neurone and effector cell)

Impulses are transmitted across synapses using diffusion of neurotransmitters (specialised chemicals)

29
Q

What is the synaptic cleft?

A

Gap which separates axon on 1st neurone from dendrite of next neurone

30
Q

What is the presynaptic neurone?

A

Neurone along which nerve impulse has arrived

31
Q

What is postsynaptic neurone?

A

Neurone that receives NT

The postsynaptic membrane has chemical gated sodium ion channels that have receptor sites for Ach.

32
Q

What is the synaptic knob?

A

Swollen end of presynaptic neurone - contains many mitochondria and high density of SER to produce NT.

33
Q

What are synaptic vesicles?

A

Vesicles containing NT which can fuse with presynaptic membrane to release NT into synaptic cleft via exocytosis

34
Q

What are NT receptors?

A

Specific receptor molecules in postsynaptic membrane which have complementary shape to NT

35
Q

What is the role of synapses?

A

Ensures impulses are unidirectional
- NT receptors are only located on postsynaptic membrane, so impulses can only travel across synaptic cleft in one direction (pre to post synaptic membrane)

Synaptic divergence

  • Allows impulses from one neurone to be transmitted to number of neurones at multiple synapses.
  • One stimulus - simultaneous responses

Synaptic convergence

  • Many neurones can connect to one neurone, so enables information to be amplified.
  • Enables stimuli from different receptors to interact to produce a single result.
36
Q

Definition of summation?

A

If a stimulus is weak, only a small quantity of NT will be released into synaptic cleft, which may not stimulate action potential
Summation occurs when effect of NT is combined.

37
Q

Types of summation?

A

Spatial summation

Temporal summation

38
Q

What is spatial summation?

A

Occurs when number of presynaptic neurones connect to one postsynaptic neurone
Each releases NT which accumulates to high level in synapse and triggers action potential in single postsynaptic neurone.

39
Q

What is temporal summation?

A

Occurs when single presynaptic neurone releases NT as a result of an action potential several times over short period of time. NT builds up in synapse until quantity is high enough to trigger action potential.

40
Q

Other factors affecting the speed of action potential transmission.

A

Temperature - Higher temps - more kinetic energy of ions - faster diffusion of ions.
Axon diameter - Larger axon diameter, faster transmission due to less resistance to flow of ions in cytosol.

41
Q

Depolarisation definition

A

When potential difference becomes more positive

42
Q

Repolarisation definition

A

When potential difference becomes more negative

43
Q

Hyperpolarisation definition

A

When potential difference is lower than resting potential

44
Q

Definition of an impulse?

A

A signal transmitted along a nerve fibre.

45
Q

Importance of the refractory period?

A

Without it, the axon could be immediately depolarised after an action potential, so the action potential could travel backwards, so it wouldn’t reach its target cell.

Limits frequency of nerve impulses.

46
Q

All or nothing response info

A

The greater the stimulus, more frequent impulses are sent. Once threshold is reached, action potential occurs. If not reached, no response
A larger stimulus will increase frequency of action potential not alter size of action potential.

Gymnastics and tumbling (29 decks)

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