nervous system

Question 1

what is a stimuli?

Answer 1

change in environment causing organism to respond

Question 2

main parts of nervous system

Answer 2

1. central nervous system (CNS)– brain + spinal cord
2. peripheral nervous system (PNS) – cranial nerves, spinal nerve and sense organs

Question 3

how nervous system responds to a stimulus

Answer 3

1. receptors detect stimulus, transmits nerve impulse
2. nerve impulse is transmitted across sensory neurone to CNS
3. CNS integrates and interpret information. Initiates an appropriate response
4. In CNS, nerve impulse is transmitted across a synpase from sensory neurone to relay neurone thenacross another synapse from relay neurone to motor neurone. (by release of neurotransmitters)
5. nerve impulse leaves CNS along motor neurone to effector to carry out the response.

Question 4

what are neurones and what do they contain

Answer 4

• specialised cells adapted for transmission of nerve impulses
• consists of a cell body, synaptic knobs, myelin sheath (schwann cell) and nerve fibers (axons and dendrons)

Question 5

types of neurones

Answer 5

1. sensory neurones: transmit nerve impulses from the receptors to the CNS
2. motor neutones: transmit nerve impulses from the CNS to the effectors
3. relay neurones: transmit nerve impulses from the sensory neurone to motor neurone INSIDE THE CNS

Question 6

cell body in neurone

Answer 6

has nucleus and organelles

Question 7

nerve fibres in a neurone

Answer 7

• cytoplasmic extensions from the cell body

dendrons:
* transmit nerve impulses towards the cell body
* receive impulses
* branch into many smaller, numerous dendrites

axons:
* transmits impulses away from the cell body

Question 8

schwann cell (and myelin sheath) in a neurone

Answer 8

• wrap around nerve fibers at regular intervals
• membranes of the schwann cells form the myelin sheath.
• neurones which are enclosed by schwann cells are called myelinated neurones

nodes of ranvier: 1mm gaps between schwann cells where myelin sheath is absent

Question 9

functions of myelin sheath

Answer 9

• provides protection and insulation
• prevents the loss of current
• speeds up transmission of nerve impulse

Question 10

synaptic knobs in a neurone

Answer 10

• bulbous structures found at the end of axons
• relay nerve impulses from 1 neurone to another through the release of chemicals called neurotransmitters in synaptic vesicles

Question 11

What is a nerve?

Answer 11

bundle of nerve fibre covered by connective tissue

Question 12

Nerves may contain

Answer 12

• sensory nerve fibres only
• motor nerve fibres only
• both sensory and motor nerve fibres

Question 13

gray matter vs white matter

Answer 13

GRAY MATTER:
* consist mainly of cell bodies
* forms outer layer of brain and central part of spinal cord

WHITE MATTER:
* consist mainly of nerve fibres (axon + dendron)
* forms outer layer of spinal cord and central part of brain

Question 14

1.

what are spinal nerves

Answer 14

consist of dorsal roots and ventral roots

dorsal roots : axons from sensory neurones into spinal cord

ventral roots : axons from motor neurones into spinal cord

Question 15

definition of voluntary action

Answer 15

action under the control of a will

Question 16

definition of reflex action

Answer 16

immediate response to a specific stimuli without concious control

Question 17

reflex action can be classified as

Answer 17

1- spinal reflexes:
* controlled by the spinal cord
* occurs below neck

2 - cranial reflexes:
* controlled by the brain (NOT OF CONSCIOUS WILL)
* occurs in head region

Question 18

reflex arc definition and components of the reflex arc

Answer 18

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

components:
1. receptor
2. sensory neurone
3. relay neurone in the CNS
4. motor neurone
5. effector

Question 19

Spinal reflex: withdrawal of hand from hot pan

Answer 19

1. heat from the pan stimulates temperature receptors in the skin, generates nerve impulses
2. nerve impulse is transmitted across sensory neurone to spinal cord
3. In spinal cord, nerve impulse is transmitted across a synpase from sensory neurone to relay neurone then across another synapse from relay neurone to motor neurone. (by release of neurotransmitters)
4. nerve impulse leaves spinal cord along motor neurone to bicep muscles. bicep muscles contract to bring out the sudden and immediate withdrawal of hand
5. at spinal cord, relay neurone also transmits the nerve impulses to the brain (Not part of the reflex arc)
   this makes the brain aware of what is happening

Question 20

reflex vs voluntary action

Answer 20

reflex
- does not involve conscious control
- stimulus is always involved
- faster
- the same stimulus will always result in the same response

voluntary
- involves conscious control
- stimulus may not always be involed
- slower
- the same stimulus may not always result in the same response

Question 21

nervous vs endocrine system

Answer 21

nervous system
- involves nerve and chemical impulses
- impulses are transmitted by neurones
- quick responses
- responses are short- lived
- may be voluntary or involuntary
- usually localised

endocrine system
- involved hormones
- hormones are transmitted by blood
- usually slower responses
- responses may be short or long lived
- always involuntary
- tend to affect one or more target organs