Nervous System

Question 1

What are the components of a nervous system?

Answer 1

Sensory receptors -> detect changes in environment/ stimuli.
Energy transducers: convert energy from 1 form to another.
Receptors connect to them to send info via N.I to CNS.
Brain co-ordinates response (sends N.I to motor neurone to effector).

Question 2

What stimulus does machanoreceptor detect?

Answer 2

Detects touch (stimulus) -> pacinian capsule -> skin and joints (sense organ).

Question 3

Chemoreceptors

Answer 3

Chemoreceptor -> chemicals > olfactory -> nose

Question 4

Thermoreceptor

Answer 4

Temp -> skin

Question 5

Photoreceptor

Answer 5

Photoreceptor -> wavelength -> retina.

Question 6

What does pacinian capsule do?

Answer 6

• Detects mechanical pressure.
• sensory nerve ending in middle
• connective tissue rings around nerve
• pressure on skin changes -> ring of tissue = deformed -> pushes against nerve ending

Question 7

How do receptors trigger nerve impulses?

Answer 7

1- end of neurone has Na+ channels in membrane -> permeability changes to Na+ when they change shape.
2- resting state: stretch mediated Na+ channels in membrane closed
3- memb -= polarised (more + outside) -> resting potential.
4- when pressure is applied, pacinian capsule changes shape.
5- Stretch mediated Na+ channels open.
6- charge diff across memb reverses -> memb depolarised -> “generator potential”.
7- If it exceeds the threshold potential, an A.P is triggered
Increases stimulus = increases G.P = more likely to react T.P for A.P

Question 8

Definition of these terms:
- dentrites
-cell body
- axon
- Schwann cells
- nodes of ranvier
- axon terminal

Answer 8

Dendrites/dendrons - carry impulse towards cell body
Cell body - usual organelles, lots of SER, RER, mitochondria, golgi (modifies lipids and proteins)
Axon - carries impulse away from cell body
Schwann cells - secrete myelin sheath
Nodes of ranvier - gaps in myelin sheath.
Axon terminal - where neurone connects to another neurone/ effector via synapse.