The Nervous System

Question 1

Define stimulus

Answer 1

• a change in environment that triggers a reaction (response)
• organism responds in way that benefits itself

Question 2

Define Response

Answer 2

• organism reaction to stimulus

Question 3

Define sensitivity

Answer 3

• ability of organism to detect and respond to changes in environment
• survival dependent on appropriate response to stimuli

Question 4

Role of nervous system

Answer 4

• control activities of body and how it reacts to stimuli
• transmit info as nerve signals
• senses stimuli in surroundings, determines and directs responses to surroundings
• enable coordination of diff parts of body
• consist of well-developed brain, spinal cord, spianl nerves, highly specialised sense organs

Question 5

Define involuntary actions

Answer 5

• automatic activities

- not controlled consciously

Question 6

Define voluntary actions

Answer 6

• activities that are controlled consciously

Question 7

Voluntary actions (e.g. patting cat) Nervous pathway

Answer 7

1. cat rubs against leg (stimuli)
2. touch receptors at leg stimulated
3. nerve impulses transmitted thru sensory neurones to spinal cord
4. relay neurones conduct nerve impulses to brain
5. brain evaluates info, decides response (pat cat)
6. brain generate nerve impulses
7. nerve impulses transmitted along relay neurones to motor neurones
8. impulses transmitted to effector muscles (causes contraction of arm muscles, pat cat)

Question 8

Sense organs

Answer 8

1. help body adjust quickly to stimuli

2. enable various parts of body to coordinate quickly

Question 9

Central Nervous System (CNS)

Answer 9

• brain
• spinal cord
• integrate and process impulses received frm PNS

Question 10

Peripheral Nervous System (PNS)

Answer 10

• cranial nerves
• spinal nerves
• provide comm link between CNS and other parts body

Question 11

How does nervous system process info? (nervous pathway)

Answer 11

1. info gathered by receptors (sense organs)
2. info converted to electrical signals (nerve impulses)
3. nerve impulses transmitted by peripheral nerves to CNS
4. brain process info based on pattern of impulses
5. sends nerve impulses to effectors (muscle/glands)
6. intended action carried out

Question 12

Nervous tissue (neurones)

Answer 12

• consist of 3 types of nerve cells (neurones)

- sensory, relay, motor neurones

Question 13

Basic structure of neurone

Answer 13

• cell body (nucleus, cytoplasm)
• axon
• dendron
• dendrites

Question 14

Cell body

Answer 14

• 1 nucleus and cytoplasm
• mitochondria and ribosomes present
• metabolic activities carried out

Question 15

Dendron

Answer 15

• receives info
• nerve fibres (conduct impulses towards cell body)
• small, break up into terminal branches (dendrites)

Question 16

Dendrites

Answer 16

• many short branching processes frm dendron (increase SA:V, faster transmission rate)
• specialised in receiving excitation, stimuli, impulses frm another neurone, conducting impulses towards cell body

Question 17

Axon

Answer 17

• long nerve fibre, sometimes branced (may rch more than 1m)
• 1 axon per neurone
• diameter frm 0.5mm (increase SA:V)
• conduct impulse from dendrites, away frm cell body to synapse

Question 18

Structure of motor neurone (Dendron, dendrites, axon)

Answer 18

• Dendron: nerve fibres that transmit nerve impulses towards cell body
• Dendrites: receive nerve impulses frm other neurones
• Axon: nerve fibres that carry impulses away frm cell body, ends of axon transmit nerve impulses to effector
• Pathway: dendrites, dendron, cell body, axon, effectors

Question 19

Nodes of Ranvier

Answer 19

• regions where myelin sheath is absent on cell fibre

- speed up transmission of impulses (allow them to jump frm node to node)

Question 20

Myelin sheath

Answer 20

• layer of fatty substance
• shields and insulates nerve fibre
• surrounded by neurilemma (thin membrane)
• ensures impulse isn’t lost (lesser needs to be generated)

Question 21

Motor end plate

Answer 21

junction between axon terminal and muscle fibre

Question 22

What happens if Myelin Sheath is damaged?

Answer 22

-some glands won’t work, muscles might not contract (may lead to paralysis)

Question 23

Sensory neurone

Answer 23

• found between sensory receptors and CNS
• transmit nerve impulse frm sense organs to CNS
• pathway: Dendrites, dendron (towards cell body in middle of neurone), axon, relay neurone in CNS

Question 24

Diff between sensory and motor neurone (3)

Answer 24

• S: long dendron, short axon ; M: short dendron, long axon
• S: circular cell body ; M: irregular shaped cell body
• S: conducts nerve impulse frm sensory receptors to CNS ; M: conducts impulse frm CNS to effectors

Question 25

Synapse

Answer 25

• junction/connection between 2 neurones
• impulses transmitted frm axon to dendron across a synapse
• transmission across synapse is via chemical means (thru transmission of neurotransmitters in synaptic vesicles)

Question 26

Define nerves

Answer 26

• bundle of nerve fibres bundled in sheath of connective tissue
• cranial nerves: nerves frm brain
• spinal nerves: nerve frm spinal cord, mixed fibres (sensory and motor nerve fibres)

Question 27

Grey matter

Answer 27

• contains cell bodies of neurones

- found at outer layer of brain, central parts of spinal cord

Question 28

White matter

Answer 28

• contains mainly nerve fibres of neurones

- found in central part of brain, outer layer of spinal cord

Question 29

Spinal cord and spinal nerves

Answer 29

• spinal cord encased in vertebral column
• spinal nerves emerge frm spinal cord (31 pairs)
• grey matter in central part of spinal cord “H” shape
• known as central canal, contains cerebrospinal fluid (runs thru middle of spinal cord)

Question 30

Spinal nerve (dorsal and ventral roots)

Answer 30

• each spinal nerve divides into 2 roots
• subdivides into branches, supply nerve fibres to various parts of body
• dorsal (top)root: contain only sensory neurones
• dorsal root ganglion: cluster of sensory neurones (bulge)
• ventral (bottom) root: contains only motor neurones

Question 31

Relay neurones (nerve impulse transmission)

Answer 31

• relay neurones lie within grey matter of spinal cord
• transmit nerve impulses from sensory neurones to brain; brain to motor neurones; sensory neurones to motor neurones (reflex)
• relay neurones form synapses with sensory and motor neurones