coordination & response

Question 1

What is the role of nervous system?
What does it contain?
What does it split into?

Answer 1

1) coordination & regulation of body function
2) Contains neurones/nerve cells which go to all parts of body.
3) splits into CNS PNS.

Question 2

define cns

Answer 2

brain & spinal cord

Question 3

define pns

Answer 3

nerves outside of brain & spinal cord.

Question 4

Describe the process/steps in a reflex arc

Answer 4

1. Neurones in reflex arcs go to through the spinal cord or through an unconscious part of the brain.
2. Stimulus -> detected by receptors -> impulses sent along a sensory neurone to the CNS.
3. When impulses reach synpase between sensory neurone & relay neurone the impulses are sent along the relay neurone.
4. When the impulses reach a synapse between relay neurone & motor neurone, the impulses are sent along the motor neurone.
5. Impulses travel along the motor neurone to the effector e.g muscle, causing it to contract or move.

Question 5

Define reflex action

Answer 5

automatically & rapidly integrating
and coordinating stimuli
with the responses of effectors (muscles and glands)

Question 6

define synapse
what its purpose?

Answer 6

1. junction between 2 neurones
2. ensure impulses travel in one direction only.

Question 7

Describe the events at a synapse

Answer 7

• An impulse stimulates release of neurotransmitter molecules from vesicles into the synaptic gap
• The neurotransmitter molecules diffuse across the synaptic gap
• Neutrotransmitter molecules bind w/ receptor proteins on the next neurone
• Impulse in then stimulated in the next neurone.

Question 8

define sense organs

Answer 8

groups of receptor cells
responding to specific stimuli:
light, sound, touch,
temperature and chemicals

Question 9

Function of cornea, iris, lens, retina, optic nerve

Answer 9

Cornea - refracts light
Iris - contains radial & circular muscles which control diameter of pupil therefore how much light enters pupil
Lens - focuses light onto the retina
Retina - contains light receptors, some sensitive to lights of diff colors
Optic nerve - carries impulses from the receptors on the retina, to the brain.

Question 10

Iris reflex (pupil reflex)
Low light intensity

Answer 10

• Radial muscles in the iris contract, become shorter, & pull the pupils, making it wider.
• Circular muscles relax.
• Wider pupil = more light can enter eye, clear image is formed at retina.

Question 11

Iris reflex (pupil reflex)
High light intensity

Answer 11

• Circular muscles in the iris contract, causing the pupil to get smaller.
• Radial muscles relax.
• Smaller pupil = less light can enter eye, protecting retina from damage.

Question 12

Looking at nearby objects:

Answer 12

• Ciliary muscles contract, suspensory ligaments slackened.
• Lens become more fat
• This increases the amount by which it refracts light.

Question 13

Looking at distant objects:

Answer 13

• Ciliary muscles relax, suspensory ligaments pulled tight.
• Lens pulled thin.
• This refracts light by a smaller amount.

Question 14

2 types of receptors in retina, function of them, distribution

Answer 14

Rods
* Sensitive to dim lights
* Allows us to see in dim light, only in black & white.
* Distributed around the edge of retina except blind spot & fovea.

Cones
* Sensitive to light of diff colors/bright light (red, green, blue)
* Gives color vision.
* Most located in fovea; tightly packed together