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Year 2 Biology > Topic 8 > Flashcards

Topic 8 Flashcards

1
Q

8.1 Know the structure and function of sensory, relay and motor neurones including the role of Schwann cells and myelination.

A

Spicy, Rice, Spicy, Rice, More, Egg, Rice
Stimulus, receptor, sensory, relay, motor, effector, response

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2
Q

Sensory Neurone

A
  • one long dendron (impulses from receptor cells to cell body)
  • cell body is in the middle
  • one short axon (impulses from cell body to CNS)
  • always myelinated
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3
Q

Relay neurone

A
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4
Q

Motor neurone

A
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5
Q

Describe the differences in the structure of a myelinated sensory neurone and a myelinated motor neurone.

A
  • cell body in the middle of the sensory neurone whereas the cell body is at the end of the motor neurone
  • sensory neurone has one long dendrone whereas motor neurone has many small dendrites
  • sensory neurone has a shorter axon than a motor neurone
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6
Q

The role of Schwann cells

A
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7
Q

Myelination

A
  • fatty, white substance that coats the axon of some neurones, forms an electrically insulating layer
  • main function is it increase the speed impulses that travel along the axon
  • Myelin sheath speeds up the transmission of action potentials using Saltatory conduction, as the action potential “jumps” to the nodes of Ranvier.
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8
Q

8.2 Understand how the nervous systems of organisms can cause effectors to respond to a stimulus

A
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9
Q

Understand how a pupil dilates and contracts

A

Dim light —> photo receptors in eye —> processes info —> radial muscles in iris are stimulated —>Radial muscles contract = pupil dilation

Bright lights —> photo receptors in the eye —> processes info —> Circular muscles in the iris are stimulated —> Circular muscles contract = pupil contraction

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10
Q

Nervous system

A
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11
Q

Endocrine system

A
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12
Q

The peripheral nervous system (PNS)

A
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13
Q

The autonomic nervous system

A
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14
Q

Dendrites/Dendrons

A
  • extensions of neurones that receive signals from other cells and conduct action potentials towards the cell body (in the sensory neurone, the dendron is myelinated)
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15
Q

Axons

A
  • extensions of neurones that conduct action potentials away from the cell body to other cells
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16
Q

Cell body of a neuron

A
  • also called the soma
  • is the spherical part of the neurone that contains the nucleus
17
Q

Difference between a nerve cell and a neuron

A

A neuron is the smallest unit of nervous tissue that is also known as a nerve cell, contains dendrites, cell body, axon and axon terminal.

A nerve is a bundle of axons of several neurons that helps in transmitting signals among various body parts.

18
Q

The sodium potassium pump

A
  • some intrinsic proteins actively transport K+ into the axon and Na+ out - the NaK pump.
  • uses ATP to simultaneously pump 3Na+ out of the cell and 2K+ in.
  • results in an overlay negative charge inside the axon.
19
Q

X

A
20
Q

How do nerve impulses start?

A
  • Neurones are stimulated by receptor cells
  • These contain special Na+ channels that are not voltage - gated, but are gated by the appropriate stimulus
  • e.g. chemical - gated Na+ channels in tongue taste receptor cells open when a certain chemical in food binds to them
21
Q

Resting potential

A
  • achieved by active transport of the NaK pump ( 3 sodium ions out for 2 potassium ions in )
  • membrane is more permeable to potassium, so sodium remains outside the neurone and potassium also leaks back out
  • leads to a negative potential difference of -70mV
22
Q

Action potential

A
  • when an action potential arrives/ the neurone is stimulated
  • sodium channels open and sodium rushes into the neurone by facilitated diffusion
  • causing depolarisation
  • At threshold of -50mV more voltage gated Na channels open
  • At +30mV Na channels close and K channels open.
  • K leaves the neurone by facilitated diffusion and Na is pumped out by active transport.
  • Repolarisation
  • Hyperpolarisation occurs as too much potassium leaves the cell
  • potassium channels close
  • resting potential is restored
23
Q

Saltatory conduction

A
  1. Depolarisation at node of Ranvier
  2. Electric current between nodes
  3. Potential difference reduced at next node, initiating another action potential
24
Q

Factors affecting the speed of an action potential
(Myelin sheath)

A
  • Myelin is an electrical insulator
  • no insulation at the Nodes of Ranvier
  • The depolarisation/action potential jumps from one Node of Ranvier to another
  • SALTATORY CONDUCTION
  • this means that the entire axon doesn’t need to depolarise, which speeds up the nerve impulse

E.g myelinated - 90 ms-1
Unmyelinated - 30ms-1

25
Q

Factors affecting the speed of an action potential
(Diameter of an axon)

A
  1. Diameter of an axon - greater diameter = faster conduction
    - due to an increased surface area (not sa:vol) for ion movement
26
Q

Factors affecting the speed of an action potential
(Temperature)

A
  • higher temperature = faster nerve impulse (rate of diffusion is faster, enzyme activity is faster e.g. ATPase
27
Q

Refractory period

A
  • time after depolarisation, where no new AP can start
  • time is needed to restore the ions, gated proteins and resting potential
  • Na+ channels cannot be opened, as it can not be depolarised again.
28
Q

The all - or - nothing principle

A

Action potential only happens if the stimulus reaches a threshold value
- stimulus is strong enough to cause an action potential
- once it starts it travels to the synapse
- (-55mV)
- AP is always the same size
- An AP is the same size all the way along the axon
- The transmission of the AP along the axon is the nerve impulse

29
Q

How do we detect the size of a stimulus?

A
  • The number of impulses in a given time - the larger the stimulus, the more impulses generated.
  • By having neurones with different threshold values-the brain interprets the number and type of neurones and thereby determines the size.
  • The number of neurones stimulated can also demonstrate the size
30
Q

Stimulus

A

Any change in the internal or external environment is called a stimulus.

Year 2 Biology (4 decks)

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