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Topic 6 Organisms response to change > Nerves > Flashcards

Nerves Flashcards

1
Q

What two systems do animals have

A

Nervous and hormonal/endocrine

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2
Q

What are the chemical coordinators of the Endocrine system and where are they secreted

A

Hormones which are secreted into the blood

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3
Q

What are the chemical coordinators of the Nervous system

A

Neurotransmitters

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4
Q

Which of the endocrine and nervous system is longer lasting

A

Endocrine system

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5
Q

Which of the endocrine and nervous system have a faster speed of effect

A

Nervous system

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6
Q

What order does a stimulus move down the nervous system

A

Stimulus
Receptor
Sensory neurone
Co-ordinator
Motor neurone
Response

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7
Q

What is a motor neurone

A

A nerve cell that carries out an impulse from the CNS to an effector

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8
Q

What is a stimulus

A

A change in the external or internal environment that brings about a response in an organism

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9
Q

What is a co-ordinator

A

Region of Central nervous system where sensory information is interpreted

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10
Q

What is a receptor

A

a structure that detects a stimulus and generates a nerve impulse

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11
Q

What is a response

A

Action behavior brought about by an effector

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12
Q

What is a sensory neurone

A

A nerve cell that carries an impulse from a receptor to the CNS

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13
Q

What does the CNS consist of

A

Brain, Spinal cord,

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14
Q

What nerves are part of the peripheral nervous system

A

Cranial nerves
Spinal nerve
Peripheral nerves
Sensory neurons
Motor neurons

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15
Q

Describe how the component part of the nervous system bring about a reflex

A

The stimulus activate receptors
An electron impulse travels along the sensory neuron to the closest CNS
An electrical impulse travels to the motor neuron to the effector
The response is brought out

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16
Q

What 5 structures make up a myelinated axon

A

Cell body
Dendrites
Axon
Myelin Sheath
Nodes of Ranvier

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17
Q

What is the cell body in the myelinated sheath

A

Contains the nucleus, cytoplasm, Endoplasmic reticulum and neurotransitters

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18
Q

What are the dendrites in the myelinated sheath

A

Finger-like projections of cytoplasm of cell body
Receive information and carry it towards the cell body

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19
Q

What are the Axons in the myelinated sheath

A

Extension of cytoplasm which transmits impulses away from the cell body

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20
Q

What are the nodes of Ranvier in the myelin sheath

A

Junctions between Schwann cells

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21
Q

What do axons do

A

take information away from the cell body

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22
Q

What are some structural features of an axon

A

No ribosomes
Smooth surface
Branched further from the cell body
can have myelin insulation

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23
Q

What do dendrites do

A

Bring information towards the cell body

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24
Q

How many axons per cell

A

1 generally

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25
Q

How many dendrites per cell

A

many dendrites per cell

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26
Q

What are some structural features of a dendrite

A

Rough surface
Has ribosomes
never has myelin insulation
branched near cell body

27
Q

What is resting potential difference across the membrane

A

-70mv

28
Q

Is the interior axon positive or negative

A

negative

29
Q

How is resting potential maintained

A

Active transport in the sodium potassium pump- 3Na+ out and 2K+ in

Facilitated diffusion - more K+ ions leak out than Na+ ions leak in through the closed facilitated diffusion channels

30
Q

What is meant by a reflex action

A

The rapid response carried out by the unconscious part of the brain
An innate reaction which occurs everytime

31
Q

How does the hormonal system differ from the nervous system

A

Slower than neuron
Chemical not electrical
Long lasting not short lasting

32
Q

You smell

A

I know

33
Q

How long does active potential last

A

about 3 milliseconds

34
Q

What is action potential

A

When neurons are stimulated by a change in the resting potential

35
Q

What is seen in the axon membrane during action potential

A

The voltage inside axon raises from -70mv to +40mv which is caused by voltage gated channels opening which allow ions to diffuse

36
Q

What happens during depolarisation

A

Voltage gated Na+ ion channels open
This leads to Na+ ion flooding down the conc gradient into the axon
So the inside of axon becomes positive

37
Q

What happens during repolarisation

A

Na+ voltage gated channels close
K+ voltage gated channels open and K+ ions flood down conc gradient of axon
Inside the axon returns to -70mv

38
Q

What is repolarisation

A

Where the axon recovers its resting potential after the membrane reaches +40mv

39
Q

What happens during hyperoplarisation

A

Too many K+ ions leave the axon so cytoplasm temporarily more negative than -70mv until the k+ ions close

40
Q

What is the all or nothing principal

A

Action potential can only be generated if the stimulus reaches a certain threshold intensity and below the threshold action potential won’t be reached

41
Q

How does size change between action potentials

A

It doesn’t all action potentials are the same size

42
Q

How does a strong stimulus differ in production in action potential to a weaker stimulus

A

A strong stimulus produces more action potentials and is likely to cause action potential in more neurones

43
Q

What is a refractory period

A

for a brief time after an impulse where
The k+ channels close and so do the Na+ channels
No matter what stimulus is applied they will not reopen to allow Na+ in
This means no impulse can pass

44
Q

What is the importance of the refractory period

A

No overlapping of potentials
Ensures a.p only travels in one direction
Limits the number of a.ps

45
Q

What are the effects of myelination

A

The myelin sheath greatly increases the speed at which impulses are conducted over the axon

46
Q

How does the myelin sheath help to increase speed

A

Insulates the axon so depolarisation can only occur at nodes of Ranvier and the impulse jumps from node to node

47
Q

How are unmyelinated sheaths slower

A

The entire axon membrane is exposed and must undergo depolarisation so impulse conduction is slower

48
Q

What are the effects of the diameter of an axon

A

Impulse will be conducted at a higher speed along neurones with thicker axons
they have a greater Surface area over which diffusion of ions can occur

49
Q

What are the effects of temperature on an axon

A

Doesn’t usual affect the speed of nerve impulses
However colder conditions can slow down the conduction of nerve impulses

50
Q

The blink reflex is caused by what type of stimuli
(7)

A

Pressure
light
touch
temperature
chemicals
smell
noise

51
Q

What event starts depolarisation

A

Sodium channels open

52
Q

Why would a hydrophobic molecule be able to pass into neurones

A

they are lipid soluble

53
Q

Why might damage to myelin sheaths lead to problems controlling muscle contraction

A

Causes hyperpolarisation or preventing depolarisation

54
Q

Why would a myelinated axon conduct impulses faster than a non-myelinated axon

A

In myelinated action potential only at nodes so impulses jump from node to node and action potential does not travel whole length

55
Q

Give 3 factors that effect the speed of nerve impulses

A

Temperature
Axon diameter
Myelination

56
Q

Why is it important that a neurotransmitter is transported back out of synapses?

A

If it isn’t removed it will keep binding to receptors
This means it will keep causing depolarisaion in post synaptic membranes

57
Q

Explain how resting potential is reestablished

A

Active transport of sodium out of axon and
Active transport of potassium into axon

58
Q

Describe how resting potential is established in an axon

A

Pump Na+ ions out of axon and diffusion of K+ into axon
Little diffusion of Na+ into axon

59
Q

Why can Na+ and K+ only pass through the axon membrane through proteins

A

Can not pas through phospholipid bilayer as they are charged

60
Q

Describe the sequence of events leading to the acetylcholine and its binding to the postsynaptic membrane

A

calcium ions enter synaptic knob
Vesicles fuse with membrane
Acetylcholine diffuses across synaptic cleft
Binds to receptors

61
Q

Explain the importance of reflex actions

A

Automatic/involuntary
Reducing damage to tissues
Posture and balance
Escaping from predators
Finding food

62
Q

Describe the sequence of events which allows information to pass from one neurone to the next neurone across a cholinergic synapse

A

Impulse causes calcium ions to enter axon
Vesicles fuse with presynaptic membrane
This releases acetylcholine
Acetylcholine diffuses across the synaptic cleft where it binds with receptors on the postsynaptic membrane
Sodium ions enter neurone
Depolarisation of postsynaptic membrane
If above the threshold action potential is produced

63
Q
A

Topic 6 Organisms response to change (2 decks)

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