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IP Secondary 4 Biology > Chapter 4 - Nervous System > Flashcards

Chapter 4 - Nervous System Flashcards

1
Q

What is a stimulus?

A

A change in the environment that causes a reaction

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2
Q

What is a response?

A

An organism’s reaction to a stimulus

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3
Q

What is sensitivity?

A

The ability of an organism to detect and respond to changes in the environment

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4
Q

What is the role of the nervous system in humans?

A
  • Allows organisms to detect changes in their surroundings and respond to it
  • Enables the coordination of the different parts of the body
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5
Q

What are involuntary actions?

A

Automatic activities that are not controlled consciously

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6
Q

What are voluntary actions?

A

Activities that are controlled consciously

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7
Q

Which of the following are voluntary actions, and which are involuntary?

  • Heart beating
  • Digesting food
  • Throwing a ball
  • Waking up in the morning
  • Breathing
A 
Voluntary: 
- Throwing a ball
- Waking up in the morning
Involuntary: 
- Heart beating
- Digesting food
- Breathing
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8
Q

Voluntary actions: What happens when a cat rubs against your leg? Describe the entire process

A
  1. Touch receptors in leg are stimulated
  2. Nerve impulses are transmitted through the sensory neurones to the spinal cord
  3. Relay neurones conduct nerve impulses to the brain
  4. The brain evaluates the information and decides on a response (e.g. pat the cat)
  5. The brain initiates the generation of nerve impulses
  6. The nerve impulses are transmitted along the relay neurones to the motor neurones
  7. Impulses are transmitted to the effector muscles that cause the muscles of your arms to contract and hence, pat the cat
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9
Q

What are the components of the human nervous system?

A
  • Central Nervous System (CNS) consists of the brain and spinal cord
  • Peripheral Nervous System (PNS) consists of cranial nerves and spinal nerves
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10
Q

What does nervous tissue consist of?

A

Consists of nerve cells known as neurones

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11
Q

What are the 3 types of neurones?

A
  • Sensory neurones
  • Motor neurones
  • Relay or intermediate neurones
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12
Q

What is a neurone made up of?

A

A cell body, an axon and a dendron

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13
Q

What does the cell body of the neurone contain?

A

Nucleus and cytoplasm

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14
Q

What is the relationship between the three types of neurones?

A 
Nerve impulse travels from: 
Sense organ (receptor) → sensory neurone (receptor neurone) → relay neurone (in the central nervous system) → motor neurone (effector neurone) → muscle fibres (effectors)
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15
Q

Function of motor neurones

A

Transmit nerve impulses from the central nervous system to the nerve effectors

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16
Q

Structure of a motor neurone: Dendrons

A

Nerve fibres that transmit nerve impulses towards the cell body

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17
Q

Structure of a motor neurone: Dendrites

A

Dendrites of the dendron receive nerve impulses from other neurones
Dendrites of the axon transmit nerve impulses to the effector

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18
Q

Structure of a motor neurone: Cell body

A

Irregular in shape

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19
Q

Structure of a motor neurone: Axons

A

Nerve fibres that carry impulses away from the cell body

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20
Q

Structure of a motor neurone: Myelin sheath

A

A layer of fatty substance that shields and insulates the nerve fibre

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21
Q

Structure of a motor neurone: Neurilemma

A

A thin membrane that surrounds the myelin sheath

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22
Q

Structure of a motor neurone: Motor end plate

A

The junction between the dendrite and muscle fibre

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23
Q

Function of sensory neurones

A

Transmit nerve impulses from the sense organs to the central nervous system

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24
Q

Structure of a motor neurone: Nodes of Ranvier

A

Regions where the myelin sheath is absent

Speed up transmission by allowing impulses to jump from node to node

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25
Q

Comparison between a sensory neurone and a motor neurone: Length of fibre

A

Sensory neurone: Long dendron and short axon

Motor neurone: Short dendron and long axon

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26
Q

Comparison between a sensory neurone and a motor neurone: Function

A

Sensory neurone: Conducts impulse from receptor to central nervous system
Motor neurone: Conducts impulse from central nervous system to effector

27
Q

What is a synapse?

A

The junction or connection between two neurones

28
Q

________ are transmitted from ________ to ________ across a synapse

A

impulses
an axon
a dendron

29
Q

Transmission across a synapse is by ________ means, through ________

A

chemical

neurotransmitters

30
Q

What is a nerve?

A

A nerve is a bundle of nerve fibres enclosed in a sheath of connective tissue

31
Q

What are cranial nerves?

A

Nerves that emerge from the brain

32
Q

What are spinal nerves?

A

Nerves that emerge from the spinal cord

33
Q

What fibres are spinal nerves made up of?

A

Made up of sensory and motor nerve fibres (mixed fibres)

34
Q

What are the regions in the brain and spinal cords?

A

Grey matter and white matter

35
Q

Composition of grey matter

A

Cell bodies of neurones

36
Q

Location of grey matter

A

Outer layers of the brain

Central parts of the spinal cord

37
Q

Composition of white matter

A

Mainly nerve fibres of neurones

38
Q

Location of white matter

A

Central parts of the brain

Outer layers of spinal cord

39
Q

What encases the spinal cord?

A

The vertebral column

40
Q

Where do spinal nerves emerge from?

A

At intervals along the length of the spinal cord

41
Q

How many spinal nerves are there?

A

31 pairs

42
Q

Describe the general structure of the spinal cord

A
  • The grey matter of a spinal cord is roughly in the shape of a letter ‘H’
  • A narrow central canal, containing cerebrospinal fluid, runs through the middle of the spinal cord
43
Q

How do spinal nerves join the spinal cord?

A

Each spinal nerve divides into 2 roots—the dorsal root and the ventral root—before it joins the spinal cord

44
Q

What does the dorsal root contain?

A

Contains only sensory neurones

45
Q

What does the ventral root contain?

A

Contains only motor neurones

46
Q

What does the dorsal root ganglion contain?

A

Cell bodies of sensory neurones are clustered together inside

47
Q

What does the grey matter in the spinal cord contain?

A

Contains mainly the cell bodies of motor and relay neurones

48
Q

What does the spinal nerve contain?

A

Contains nerve fibres from the dorsal root and ventral root

49
Q

Hoe does the spinal nerve join the rest of the body?

A

It subdivides into branches to supply nerve fibres to various parts of the body

50
Q

Relay neurones (that lie within the grey matter of the spinal cord) transmit nerve impulses from:

A
  • Sensory neurones → brain
  • Brain → motor neurones
  • Sensory neurones → motor neurones
51
Q

Relay neurones form ________ with the sensory and motor neurones

A

synapses

52
Q

How does the nervous system process information?

describe the entire process

A
  1. Information is gathered by receptors
  2. Information is converted into electrical signals (nerve impulses)
  3. Nerve impulses are transmitted by the peripheral nerves to the central nervous system
  4. Brain processes information based on the pattern of nerve impulses
  5. Brain sends nerve impulses to the effectors
  6. Intended action is carried out
53
Q

What is a reflex action?

A

An immediate response to a specific stimulus without conscious control

54
Q

What is the characteristics of reflex actions?

A

Involuntary and not under the control of a person’s will

56
Q

What happens when you touch a hot object?

A
  1. Heat stimulates the receptors in your skin
  2. Nerve impulses are produced and they are transmitted along the sensory neurone to the spinal cord
  3. In the spinal cord, nerve impulses are transmitted to the relay neurone, and then to the motor neurone
  4. At the same time, nerve impulses are transmitted to the brain
  5. Upon receiving the nerve impulses from the relay neurone, the motor neurone transmits nerve impulses to the effector
  6. The effector muscle contracts, resulting in the withdrawal of the hand from the hot object
57
Q

What are spinal reflexes?

A

Reflexes that are controlled by the spinal cord

58
Q

What are examples of spinal reflexes?

A

Withdrawal reflexes

Knee-jerk reflexes

59
Q

What are cranial reflexes?

A

Reflexes that are controlled by the brain, but occur without a person’s consciousness

60
Q

What are examples of cranial reflexes?

A

Pupil reflex

Salivation

61
Q

Describe the knee-jerk reflex

A
  1. Stimulus: The tendon under the kneecap is tapped
  2. Nerve impulses are sent to the spinal cord by a sensory neurone
  3. The information is passed from sensory neurone to
    - relay neurone
    - motor neurone
  4. The motor neurone sends an impulse to a thigh muscle
  5. Response: The muscle contracts and causes the lower leg to jerk upwards (i.e extend outwards)
62
Q

Describe the pupil reflex

A

In bright light the eye pupils constrict to reduce the amount of light entering the eye
In dim light the eye pupils dilate to increase the amount of light entering the eye

64
Q

What are the parts of the reflex arc?

A
  1. Receptors in skin
  2. Sensory neurone
  3. CNS (brain or spinal cord)
  4. Motor neurone
  5. Effector (muscle)
66
Q

What are the two type of reflex actions?

A

Spinal reflexes

Cranial reflexes

72
Q

What is a reflex arc?

A

The shortest pathway which nerve impulses travel from the receptor to the effector in a reflex action

IP Secondary 4 Biology (6 decks)

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