B10 The Nervous System

Question 1

What is the central nervous system (CNS)?

Answer 1

The part of the nervous system where information is processed. It is made up of the brain and spinal cord.

Question 2

What is the cerebral cortex

Answer 2

Region of the brain associated with consciousness, memory, and language.

Question 3

What is the cerebellum?

Answer 3

Region of the brain concerned with coordinating muscular activity and balance.

Question 4

What are the ciliary muscles?

Answer 4

Muscles that contract and relax to change the shape of the lens of the eye.

Question 5

What are the coordination centres?

Answer 5

Areas that receive and process information from receptors.

Question 6

What are effectors?

Answer 6

Areas (usually muscles or glands) that bring about responses in the body.

Question 7

What is homeostasis?

Answer 7

The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function, in response to internal and external changes.

Question 8

Systematic Error

Answer 8

These occur when measurements are out by a certain amount each time. They are harder to spot because the scientist will not know what the true value is. They are caused by an instrument measuring the wrong value each time.

Question 9

What do receptors do?

Answer 9

Detect stimuli (changes in the environment)

Question 10

What does homeostasis keep in check?

Answer 10

• blood glucose concentration
• body temperature
• water levels.

Question 11

Name all of the control centres.

Answer 11

• cells called receptors, which detect stimuli (changes in the environment)
• coordination centres (such as the brain, spinal cord and pancreas) that receive and process information from receptors
• effectors, muscles or glands, which bring about responses which restore optimum levels.

Question 12

What does the nervous system enable us to do?

Answer 12

The nervous system enables humans to react to their surroundings and to coordinate their behaviour

Question 13

How does the CNS system work?

Answer 13

Information from receptors passes along cells (neurones) as electrical impulses to the central nervous system (CNS). The CNS is the brain and spinal cord. The CNS coordinates the response of effectors which may be muscles contracting or glands secreting hormones.

stimulus-receptor-coordinator-effector-response

Question 14

What are reflex reactions?

Answer 14

Reflex actions are automatic and rapid; they do not involve the conscious part of the brain and allow us to avoid dangers at speed.

Question 15

How do reflex reactions work? (6 marker)

Answer 15

A RECEPTOR in your skin is stimulated. an ELECTRICAL IMPULSE passes along a SENSORY NEURONE to the CNS. When an IMPULSE from the sensory neurone arrives at the SYNAPSE with a RELAY NEURONE, a NEUROTRANSMITTER is released. It diffuses across the SYNAPSE to the RELAY NEURONE, setting off another ELECTRICAL IMPULSE which travels down the RELAY NEURONE. Once the impulse reaches the synapse connecting the RELAY NEURONE and the MOTOR NEURONE, the same procedure which occurred at the previous synapse is repeated. The ELECTRICAL IMPULSE travels down the motor neurone to the EFFECTOR ORGAN. The EFFECTOR ORGAN is stimulated for a response - muscle CONTRACTS, moving away from danger (STIMULUS).

Question 16

Define the reflex reaction reflex pathway. (Diagram)

Answer 16

STIMULUS - RECEPTOR - SENSORY NEURONE - RELAY NEURONE - MOTOR NEURONE - EFFECTOR - RESPONSE

Question 17

What does the brain do?

Answer 17

The brain controls complex behaviour. It is made of billions of interconnected neurones and has different regions that carry out different functions.

Question 18

What is the medulla and what does it do?

Answer 18

The medulla is concerned with unconscious activities, such as controlling the heartbeat, the movements of the gut, and breathing.

Question 19

How have neuroscientists been able to map certain parts of the brain?

Answer 19

Neuroscientists have been able to map the regions of the brain to particular functions by studying patients with brain damage, electrically stimulating different parts of the brain and using MRI scanning techniques. The complexity and delicacy of the brain makes
investigating and treating brain disorders very difficult.

Question 20

Why is it difficult to study the brain and its parts?

Answer 20

Being inside of the skull, the brain is in a very difficult place to reach. Not only this, but being the consistency of yoghurt the brain is very delicate. Drugs do not always reach the brain because of the many protective membranes surrounding. Surgery is difficult because it is not fully understood what each part of the brain actually does.

Question 21

What are the main parts of the eye?

Answer 21

• retina
• optic nerve
• sclera
• cornea
• iris
• ciliary muscles
• suspensory ligaments.

Question 22

What is accommodation?

Answer 22

Accommodation is the process of changing the shape of the lens to focus on near or distant objects.

Question 23

How do you focus on a nearby object?

Answer 23

To focus on a near object:
* the ciliary muscles contract
* the suspensory ligaments loosen
* the lens is then thicker and refracts light rays strongly.

Question 24

How do you focus on a far away object?

Answer 24

To focus on a distant object:
* the ciliary muscles relax
* the suspensory ligaments are pulled tight
* the lens is then pulled thin and only slightly refracts light rays.

Question 25

What are two common defects of the eye?

Answer 25

Two common defects of the eyes are myopia (short sightedness) and hyperopia (long sightedness) in which rays of light do not focus on the retina.

Question 26

What is a tradition method of fixing my/hyperopia?

Answer 26

Generally these defects are treated with spectacle lenses which
refract the light rays so that they do focus on the retina.

Question 27

What is a new method of fixing my/hyperopia?

Answer 27

New technologies now include hard and soft contact lenses, laser surgery to change the shape of the cornea and a replacement lens in the eye.

Question 28

How is body temperature controlled?

Answer 28

Body temperature is monitored and controlled by the thermoregulatory
centre in the brain. The thermoregulatory centre contains receptors
sensitive to the temperature of the blood. The skin contains temperature receptors and sends nervous impulses to the thermoregulatory centre. If the body temperature is too high, blood vessels dilate (vasodilation) and sweat is produced from the sweat glands. Both these mechanisms cause a transfer of energy from the skin to the environment. If the body temperature is too low, blood vessels constrict (vasoconstriction), sweating stops and skeletal muscles contract (shiver).