Topic 5a The nervous system

Question 1

Define Homeostasis

Answer 1

Homeostasis is the regulation of conditions inside the body and cells to maintain a stable internal environment, in response to changes both internal and external conditions

Question 2

Give two example conditions in your internal environment that need regulating and maintaining

Answer 2

Blood glucose content Body temperature Body water content

Question 3

What is a stimulus

Answer 3

A change in your environment which may require a response

Question 4

Name the part of the automatic control system that receives information about a stimulus and organises a response

Answer 4

Co-ordination centre

Question 5

The water content in the body is monitored by a control system. If it gets to low, a negative feedback mechanism is triggered. Briefly outline the stages in this feedback system

Answer 5

• Receptors of detect a stimulus when the water content of the body is to low -This information is sent to the co-ordination centre, which organises an appropriate response from the effectors - The effectors respond to counteract the change bringing its level back to the optimum level. Receptor detect stimulus - co-ordination centre organises response - effector bring water level to optimum

Question 6

What categories are the control systems which regulate your internal environment categorised into

Answer 6

Nervous and Hormonal (chemical communication systems)

Question 7

What type of effector secretes hormones

Answer 7

Glands secrete hormones

Question 8

A sensory neurone is a type of neurone. Name two other types of neurone

Answer 8

Relay found in CNS Relay neurone = Carry electrical impulses from the sensory neurones to the motor neurones and are found in the Central Nervous System Motor neurone = The neurones that carry the electrical impulses from the CNS to the effectors

Question 9

A dog hears a cat moving in the garden and runs toward it. - What is the stimulus in this situation. - What detects the stimulus in this situation - What type of neurone transmits the information about the stimulus to the CNS

Answer 9

Stimulus - That sound of the cat moving Receptors in the dogs ears detect the stimulus (receptors sensitive to sound) Sensory neurone transmits the information to the CNS

Question 10

What type of neurone transmits information from the CNS to an effector

Answer 10

Motor Neurone

Question 11

How do nerve impulses travel between two neurones

Answer 11

The nerve signal is transferred by chemicals which diffuse across the synapse which sets off an electrical impulse in the next nuerone

Question 12

What is a reflex

Answer 12

Reflexes are fast automatic responses to specific stimuli

Question 13

Give an example of the bodies natural automatic reflex response

Answer 13

Bright light shinning in the eye. Your pupils automatically get smaller to prevent excessive amounts of light getting into your eye and damaging your sight.

Question 14

Do reflex arcs travel through conscious parts of your brain

Answer 14

No - they are automatic responses which bypass your conscious part of the brain completely when a fast response is required

Question 15

What trick can be used to remember the reflex arc

Answer 15

SRSRMER Stimulus - Receptor -Sensory N - Relay N - Motor N -Effector - Response

Question 16

David steps on a drawing pin and immediately pulls his foot up What is the stimulus in this response? What is the effector in this response, How does it respond?

Answer 16

Stimulus = would be the pain felt from stepping on the pin The effector in this response would be the muscles contracting in order for David to lift his foot off the ground (moving foot away from the source of pain)

Question 17

What is reaction time

Answer 17

The time taken to respond to a stimulus

Question 18

Name the region of the brain that is important for consciousness

Answer 18

Cerebral Cortex - outer wrinkly layer of the brain responsible for consciousness, intelligence, memory and language Cerbral cortex = memory, intelligence, conciousness

Question 19

Where in the brain is the cerebellum located

Answer 19

At the back of the brain behind the medulla and spinal cord on diagram. It is responsible for muscle co-ordination.

Question 20

Where is the Medulla located

Answer 20

The medulla is at the base of the brain, at the top of the spinal cord. It controls unconscious activity (thing that you don’t have to think about) like breathing and your heart beat.

Question 21

Ataxia is brain condition which can cause difficulty with walking. What part of the brain may be affected with ataxia.

Answer 21

The cerebellum as this is the part of the brain responsible for muscle co-ordination

Question 22

What ways can neuro-scientists associate different parts of the brain with specific functions

Answer 22

• Studying patients with brain damage e.g. If a patient has a stroke damaging the back of the brain and the patient loses their vision we can identify that the back of the brain has something to do with vision
• Electrically stimulating the brain using electrodes to send electrical impulses to different parts of the brain and observing response
• MRI Scans Magnetic Resonance Imaging scanner to monitor brain activity

Question 23

What type of organ is the eye

Answer 23

The eye is a sense organ

Question 24

Name the different parts of the eye and their function

Answer 24

Sclera - Tough supporting wall of the eye

Cornea - Transparent outer layer found at the front of the eye. It refracts (bends)light into the eye

Pupil - The hole at the centre of the eye through which light enters Iris - Contains muscles which allow it to control the diameter of the pupil and therefore control how much light enters

Retina - Layer at the back of the eye which contains 2 light receptor cells one for light intensity and the other which is sensitive to colour

Lens - focuses the light into the Retina Cillary muscles and Suspensory ligaments control the shape of the lens

Optic nerve - carries impulses from the receptors on the retina to the brain

Question 25

Describe how the eye responds to bright light

Answer 25

A reflex is triggered making the pupil smaller. The circular muscles in the iris and the radial muscles relax thus reducing the amount of light that can enter the eye.

Question 26

Describe how the iris reflex protects the eye

Answer 26

Bright light can damage the retina. The iris reflex to bright light quickly reduces the amount of light which is able to enter the eye and in turn protects the retina from damage.

Question 27

In relation to the eye what is accommodation

Answer 27

The process of the eye focusing light on the retina by changing the shape of the lens

Question 28

What does a diagram of an eye looking at a distant object look like

Answer 28

The lens cillary muscles relax not touching the lens and the lens looks thinner

Question 29

What happens when the eye wants to focus on an object nearby

Answer 29

• Cillary muscles contract which slacken the suspensory ligament - The lens becomes fat and more curved - This increases the amount by which it refracts light into the eye

Question 30

What happens when the eye wants to focus on an object in the distance

Answer 30

• The cillary muscles relax which allows the suspensory ligaments to tighten - This makes the lens go thin (less curved) - So it refracts light by a smaller amount

Question 31

What causes a person to be long or short sighted

Answer 31

When the lens cannot focus the light in the correct place on the retina

Question 32

What is long sightedness

Answer 32

Long sightedness refers to people who are unable to focus on a near object - In long sighted people images are brought into focus behind the retina

Question 33

What is the medical term for long sightedness

Answer 33

Long sightedness = Hyperopia Can be corrected by convex lens (curves outwards which refracts the light rays so they can focus on the retina)

Question 34

What is the medical term for short sightedness

Answer 34

Short sightedness = Myopia Can be corrected by concave lens (curves inwards which refracts the light so the light rays can focus on the retina)

Question 35

What is short sightedness

Answer 35

Short sightedness refers to people who are unable to focus on distant objects. This occurs when the lens is the wrong shape or the eyeball is too long

Question 36

what is a contact lens

Answer 36

a thin lens that sight on the surface of the eye and are shaped to compensate for the fault in focusing

Question 37

Name some alternative treatments for myopia and hyperopia other than glasses

Answer 37

Laser eye surgery - laser used to vaporise the tissue thus changing the shape of the cornea which effects how strongly it refracts light into the eye Contact lenses - Thin lens sits on surface of the eye and is shaped to compensate for the fault in focusing Replacement lens surgery - natural lens is removed and replaced with a plastic artificial one.

Question 38

What is the thermoregulatory centre

Answer 38

Is a part of the brain which controls your bodies core internal temperature. Ideal temp 37c

Question 39

Where does the thermoregulatory centre receive inputs about body temperature?

Answer 39

Information is received from receptors in the skin (cells which react to stimuli) sensitive to the temperature blood flowing through the brain as well as receptors in the skin sensitive to skin temperature which send information to the brain via nerve impulse

Question 40

In what way does the body respond to an increase in core body temperature

Answer 40

• Hairs on the skin lie flat reducing the air trapped near the surface of the skin. This allows heat to be transferred from the skin to the environment more easily - Sweat is produced by sweat glands, When sweat evaporates from the skin, it transfers energy to environment helping to reduce body temperature. - Blood vessels supplying the skin capillaries dilate (get wider). This allows more blood to flow close to the surface of the skin. This is called VASODIALATION. It helps transfer energy to the environment.

Question 41

In what way does the body respond to a drop in core body temperature

Answer 41

• Hairs stand up on the skin trapping the air near the surface of the skin and creating an insulating barrier to reduce the amount of energy transferred to the environment - No Sweat is produced - blood vessels supplying skin capillaries constrict to reduce the skins blood supply (VASOCONSTRICTION). It reduces the amount of blood that flows close to the surface of the skin and so less energy is transferred from the skin to the environment

Question 42

What is the order of response to a stimulus

Answer 42

Receptor is stimulated - signal sent along neurones to the brain - brain co-ordinates a response - signal sent along neurones to the effector

Question 43

What are neurones

Answer 43

Neurones are individual nerve cells which are bundled into nerves