3.8 The nervous system

Question 1

What is the role of the nervous system?

Answer 1

To transmit signals from the brain to the rest of the body, detecting processing and protecting

Question 2

What is a stimulus?

Answer 2

A detectable change in the internal or external environment producing a response

Question 3

What is a receptor?

Answer 3

A transducer of energy converting it to electrical
provide organisms with senses

Question 4

What are the 8 senses?

Answer 4

Sight
touch
taste
smell
hearing
pain
temperature
balance

Question 5

What is the CNS made up from?

Answer 5

Brain, Brainstem and spinal cord
Mostly intermediate neurones

Question 6

What does the CNS do?

Answer 6

Processes information form a stimulus

Question 7

What is the PNS made up from?

Answer 7

Neurones outside of the CNS
sensory and motor neurones

Question 8

What is the spinal chord made up of?

Answer 8

Unmyelinated neurones bundled in a column

Question 9

What are the divisions of the PNS?

Answer 9

The somatic nervous system
The autonomic nervous system

Question 10

What is the function of the Somatic nervous system?

Answer 10

voluntary movements
sensory and motor neurones of the skeletal muscles

Question 11

What is the general function of the autonomic nervous system? and what are its divisions?

Answer 11

unconscious control
Sympathetic and parasympathetic

Question 12

What is the function of the sympathetic system?

Answer 12

‘Fight or flight’
increases energy functions
e.g. increases heart rate or sweating

Question 13

What is the function of the parasympathetic system?

Answer 13

‘rest and relax’
lowers energy functions

Question 14

What is a reflex arc?

Answer 14

A neural pathway taken by impulses in rapid unconscious actions to protect the body

Question 15

What is the general route of a reflex arc?

Answer 15

Stimulus–Receptor—CNS—Effector—Response

Question 16

What tissue type is an effector?

Answer 16

Gland or muscle

Question 17

What is the reflex arc for heat withdrawal?

Answer 17

Heat—temperature receptors—Impulse up spinal chord to intermideate neurone—motor neurone contracts muscle

Question 18

What organism has a nerve net?

Answer 18

hydra

Question 19

What is a nerve net? and what it it made of?

Answer 19

A basic nervous system with no brain
Ganglia cells allowing signals in all directions and sensory cells that detect stimuli

Question 20

What is the charge of a resting potential?

Answer 20

-70 mv

Question 21

How do sodium and potassium move at rest?

Answer 21

K+ diffuses out
Na+ diffuses in
3 Na+ for every K+

Question 22

How does the sodium potassium pump work?

Answer 22

1. 3 Na+ bind to protein inside the cell
2. ATP losses a Phosphate to the protein causing it to shift, releasing Na out of the cell
3. 2 K+ bind to protein outside the cell
4. P leaves protein releasing K into the cell

Question 23

What causes an action potential?

Answer 23

Energy from stimulus opens gated Na channels
Rapid diffusion of Na+ into cell causes depolarisation

Question 24

What voltage is a depolarized cell?

Answer 24

+ 40 V

Question 25

What causes repolarisation?

Answer 25

1. at +40v Na gates shut 2. K gates open and K+ diffuses out of the cell 3. membrane is repolarised

Question 26

What causes hyperpolarisation?

Answer 26

K+ gates remain open and excessive K leaves Na/K pump restores -70v

Question 27

What voltage is hyperpolarisation at?

Answer 27

-90 V

Question 27

What voltage is hyperpolarisation at?

Answer 27

-90 V

Question 28

What voltage is the action potential threshold at?

Answer 28

-55 V

Question 29

What is the 'All or Nothing Law'?

Answer 29

Stimulus threshold must be met to generate an action potential AP is always at +40V but frequency can increase

Question 30

What factors impact conduction speed?

Answer 30

Temperature-faster ions diameter of axon- more ions flowing myelination- salutary conduction length of axon number of channels

Question 31

What is Saltatory conduction?

Answer 31

Ap jump from node to node increasing conduction speed

Question 32

What steps occur at the synapse? (9)

Answer 32

1. Impulse arrives at bulb of pre-synaptic neurone 2. Ca ion channels open in membrane 3.Ca ions diffuse down conc gradient 4. Vesicles of neurotransmitters fuse with presynaptic membrane 5. exocytosis of neurotransmitters into synaptic cleft 6. neurotransmitters diffuse across cleft and bind to receptor on post synaptic membrane 7. Receptor proteins change shape 8. Na ion channels open, Na diffuses down conc gradient 9. depolarisation occurs and AP is generated

Question 32

What steps occur at the synapse? (9)

Answer 32

1. Impulse arrives at bulb of pre-synaptic neurone 2. Ca ion channels open in membrane 3.Ca ions diffuse down conc gradient 4. Vesicles of neurotransmitters fuse with presynaptic membrane 5. exocytosis of neurotransmitters into synaptic cleft 6. neurotransmitters diffuse across cleft and bind to receptor on post synaptic membrane 7. Receptor proteins change shape 8. Na ion channels open, Na diffuses down conc gradient 9. depolarisation occurs and AP is generated

Question 33

What are the properties of a synapse? (4)

Answer 33

Move impulses in 1 direction transmit between neurones protect response system from overstimulation filter out low level stimuli

Question 34

What is a drug?

Answer 34

Molecule that has a physiological effect on the body when absorbed or injected