Nerves

Question 1

Central Nervous System- components and function

Answer 1

1) Brain
2) Spinal
It processes information provided by a stimulus and provides a response

Question 2

Peripheral Nervous System (2)

Answer 2

1- Somatic NS

2- Autonomic NS

Question 3

Somatic NS

Answer 3

Pairs of nerves branching/ originating from the brain and spinal cord
Carry impulses from receptors to CNS (sensory) and CNS to effectors (motor)

Question 4

Autonomic NS

Answer 4

Unconscious control of internal organs (heartbeat and breathing)

Question 5

Stimulus

Answer 5

Detectable change in external or internal environment of an organism

Question 6

Neurone and 3 types

Answer 6

Highly specialised cells that carry impulses in one direction. Neurones bundled together form nerves
1- Sensory
2- Relay
3- Motor

Question 7

Sensory Neurone

Answer 7

Carries impulses from receptor cells to CNS (co-ordinator) via the dorsal root
Short and cell body in dorsal root ganglion

Question 8

Relay neurone

Answer 8

Connector/ intermediate in CNS which connects sensory and motor neurones.
Receives impulse from sensory neurone and passes it onto the motor neurone.
Short and found in grey matter

Question 9

Motor neurone + Effectors (2)

Answer 9

Carries impulses from CNS (co-ordinator) to the effector organs via ventral root to initiate a response. LONG
Effectors-
1- Muscle- contraction of muscle
2- Gland- secretion of hormone

Question 10

Reflex action

Answer 10

Rapid/ fast, automatic and involuntary response to a stimulus, which is unconscious and does not involve the brain. Protective- prevents damage, harm and injury.

Question 11

Reflex arc

Answer 11

Path travelled by impulses during reflex action.

Stimulus -> Receptor -> Sensory -> Relay -> Motor -> Effector -> Response

Question 12

White and Grey matter

Answer 12

White- mainly axon and myelin and no cell bodies

Grey- darkly stained nuclei and cell bodies of neurones

Question 13

Dendrite

Answer 13

Extensions that connect neighbouring neurones.

Carry impulses towards cell body

Question 14

Axon

Answer 14

Slender/ long cytoplasmic extension which carries impulses away from the cell body

Question 15

Cell body

Answer 15

Contains nucleus, rER, ribosomes to produce neurotransmitters and protein channels and mitochondria for ATP to carry impulse

Question 16

Schwann Cells

Answer 16

Surround and support nerve fibres. Grow around axon to form the myelin sheath, which consists of many layers of phospholipid bilayers

Question 17

Myelin sheath

Answer 17

Acts as electrical insulator around axon and speeds up transmission of impulses

Question 18

Node of Ranvier

Answer 18

Areas where myelin sheath is missing, so the membrane can be depolarised in those regions

Question 19

Axon terminal

Answer 19

Secretes neurotransmitter (synthesised in synaptic knob) to transmit impulse to adjacent neurone

Question 20

Nerve nets

Answer 20

Simplest type of nervous system with 1 type of nerve cell. Short extensions joined and branched in different directions

• In jellyfish and hydra (invertebrates)
• Ganglion cells connect while sensory cells detect light and touch
• Hydra (radial symmetry) have simple pattern, easy to manipulate and regenerate fast
• Cannot detect direction of stimulus
• Hydra senses light and chemicals and responds with locomotion, hunt and feed
• Bigger intensity of stimulus = greater response

Question 21

Nerve nets vs CNS

Answer 21

• It has 1 type of cell vs 3
• Non-myelinated vs myelinated
• Can transmit impulses in both directions
• Shorter neurones vs longer
• Slower transmission/ response vs faster transmission of impulses
• Small no of effectors vs greater no
• Respond to limited number of stimuli
• Impulse passes in all directions vs 1 direction

Question 22

Why slower transmission in nerve nets?

Answer 22

• Non-myelinated so impulse has to travel across whole length of neurone/ axon
• In mammals, nodes/ myelin causes saltatory conduction which is faster as impulse jumps from node to node and not across entire length