Nervous System

Question 1

What are the two control systems that work together to help the human body respond to change?

Answer 1

Nervous System and Endocrine system (hormones)

Question 2

Why do we need to react to the changes that occur in our environment? How do we detect these changes?

Answer 2

Because our environment is constantly changing, we need to be able to react to these changes so that we can avoid danger, find food and water, or a mate. Our senses are what allow us to detect these changes which are known as stimuli.

Question 3

How are stimuli picked up?

Answer 3

Stimuli are picked up by special cells called receptors. These are usually found working together in groups in special sense organs

Question 4

What is a stimulus?

Answer 4

A change in the internal or external environment which is detected by receptor cells and influences a response by the organism

Question 5

An example of an internal and an external stimulus that you may need to respond to

Answer 5

External - change in temperature

Internal - change in blood sugar

Question 6

Examples of senses and the stimulus and their sense organs

Answer 6

Touch (skin) - temperature, pressure and pain
Taste (tongue) - chemicals tastes (in food and drinks)
Smell (nose) - chemicals in the air
Sight (eyes)- light
Hearing (ears)- sound
Balance (ears)- body position

Question 7

What is the central nervous system made up of?

Answer 7

Brain and spinal cord

Question 8

What happens when a stimulus is detected by a receptor?

Answer 8

When a stimulus is detected by a receptor, the sensory neurone carries the impulses from the receptor to the central nervous system through the spinal cord to the brain where the brain decides what to do and is taken back down the spinal cord by the motor neurone to the effector organ which causes a response.

Question 9

What can the effector organ be?

Answer 9

Either a muscle or a gland

Question 10

SUUMARY: What is an sensory neurone, motor neurone and relay neurone?

Answer 10

Sensory neurone - carry impulses from receptor to the central nervous system

Motor neurone - carry impulses from the central nervous system to effector organ

Relay neurone - carry impulses from sensory neurone and pass them to motor neurone within the central nervous system

Question 11

When neurones are grouped into bundles, what are they called?

Answer 11

In the body, neurones are grouped into bundles of the long axons making up a nerve fibre.

Question 12

What are synapses? How does it work?

Answer 12

When one neurone meets another neurone, special connections are made called synapses.

They are slight gaps between two neurones which enables the impulse to be transmitted from one neurone to the next.

As the impulse arrives at the end of the first neurone, it stimulates from one neurone to the next. As the impulse arrives at the end of the first neurone, it stimulates vesicles containing special chemicals called neurotransmitters to release their contents into the gap. The neurotransmitters diffuse across the gap and stimulate the generation of an impulse in the next neurone.

Question 13

What changes when it goes through the synapse?

Answer 13

Transmission across the synapse involves a change in the type of message from an electrical impulses to a chemical transmission while its going across the synapse and then changes back to electrical again in the next neurone

Question 14

What are effector organs?

Answer 14

They bring about the correct response to the stimulus. They are usually muscles in which they contract to bring about a movement to respond to the stimulus

Or they are glands in which they secrete chemical substances such as enzymes or hormones to respond to the stimulus

Question 15

Diagram of reflex arc

Answer 15

On sheet - quite simple tho - the weird pump thing is the muscle meaning effector organ
The thing that is coming into contact with the item (e.g. a hand coming into contact with a candle), the candle is the stimuli and the cell in the hand, the pain receptor is the receptor in the skin
The neurones, you can tell by knowing that sensory is the one going to the brain/spinal cord and the motor is the one coming back.

Question 16

What are reflexes? Do they happen slowly or quickly? Whats an reflex arc?

Answer 16

Rapid responses which are intended to avoid danger and harm. They happen quickly because they bypass (go past) the conscious areas of the brain so that you are not often aware of it until it has actually happened. The nerves involved in a reflex action follow a simple pathway called a reflex arc

Question 17

What happens in an reflex arc?

Answer 17

When the receptor detects the danger, it causes the nerve impulses to pass along a sensory neurone which transmits the impulse to the spinal cord. In the spinal cord, a relay neurone transmits the impulse to a motor neurone. The motor neurone transmits the impulse to an effector which carries out a response. In this case, a muscle contracts and the finger is pulled away.

In a reflex action, the brain isn’t involved and instead the relay neurone takes it straight to the motor neurone.

Question 18

Function of the eye

Answer 18

In humans, the eye is the sense organ that responds to the light stimulus. It contains specialised receptor cells that detect the light passing into the eye and send electrical impulses to the brain along the optic nerve.

Question 19

Structure of the eye

Answer 19

Look at diagram on sheet

Question 20

What are the two different types of light sensitive cells in the retina?

Answer 20

Cone cells - they respond to light of a certain wavelength and therefore colour. Cones only work in bright light so we can only see colour if the light is bright enough. They are clustered around the fovea where most light falls in bright conditions

Rod cells - they respond to differences in light intensity not wavelength and are found throughout the retina. They work better than cones at low light intensities, but they only give black and white images.

Question 21

Cornea

Answer 21

Transparent area of the sclera which helps to bend light rays onto the retina

Question 22

Lens

Answer 22

Clear disc which focuses light onto the retina

Question 23

Aqueous humour

Answer 23

Fluid that fills the front of the eye and helps bend light rays on the retina

Question 24

Vitreous humours

Answer 24

Jelly like fluid which maintains the shape of the eyeball and also helps bend light rays onto the retina

Question 25

Pupil

Answer 25

The hole through which light enters the eye

Question 26

Retina

Answer 26

Layer of light sensitive cells which when stimulates send impulses to the brain along the optic nerve

Question 27

Fovea

Answer 27

Small area of the retina which contains only cones

Question 28

Blind spot

Answer 28

Point at which the optic nerve leaves the eyeball and there is no retina

Question 29

Optic nerve

Answer 29

Carries electrical impulses to the brain

Question 30

Eyelid

Answer 30

Protects the eye from physical harm

Question 31

Ciliary muscles

Answer 31

Change the shape of the lens when they contract

Question 32

Conjunctiva

Answer 32

Thin, transparent protective layer over the surface of the eye

Question 33

Suspensory ligaments

Answer 33

Hold the lens in place and connect it to the ciliary muscles

Question 34

Choroid layer

Answer 34

Dark pigmented layer which absorbs light and stop it being reflected back into the eye

Question 35

Iris

Answer 35

Coloured sheet of muscle which controls how much light enters the eye by changing the size of the pupil

Question 36

Sclera

Answer 36

Tough, strong protective outer layer well supplied with blood vessels to supply the retina with food and oxygen

Question 37

How is the amount of light entering the eye controlled?

Answer 37

It is controlled by the iris. This contains muscle which is able to contract and change the size of the pupil which is a hole in the centre of the eye.

Question 38

What does the iris contain?

Answer 38

Contains two types of muscle - radial and circular

Question 39

What happens in bright light?

Answer 39

The circular muscles contract and the radial muscles relax, making the pupil constrict. This prevents too much light from entering the eye and so prevents damage to the light sensitive cells on the retina

Question 40

What happens in dim light?

Answer 40

The radial muscles contract and the circular muscles relax, making the pupil dilate allowing more light into the eye so that we can see better.

Question 41

What about light from a distance?

Answer 41

When light enters the eye from an object in the distance, the light rays are almost parallel when they enter the eye. This means that they need less refraction to come to a focus on the retina. The cornea starts to bend the rays and the lens is less involved.

Question 42

The shape and lens of the eye when light enters from a distance

Answer 42

Long and thin. To get the lens into this shape, special muscles called sclera muscles relax and the lens is pulled thinner by the suspensory ligaments.

Question 43

What about light from a close object?

Answer 43

Light rays from near objects are diverging when they enter the eye and so they need much more bending to get them into focus on the retina. To do this, the lens must change shape and become rounder and fatter.

Question 44

How do you get the lens to change shape when lights comes from a close object?

Answer 44

To enable this, the ciliary muscles contract which means that the suspensory ligaments are pulled less and the lens become more rounded. This bends the light to produce a focussed image on the retina. The bending of light is called refraction.