B12 Homeostatis and the nervous system

Question 1

What is homeostasis and what does it do?

Answer 1

the regulation of the internal conditions of a cell’s or organism in response to internal or external changes.

maintains optimal conditions for enzyme action and all cell functions.

Question 2

What conditions do homeostasis control?

Answer 2

• blood glucose concentration
• body temperature
• water and ion levels

Question 3

What type of communication do automatic control systems use?

Answer 3

nervous and hormonal

Question 4

What do all control systems include?

Answer 4

• 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 5

What does the nervous system allow us to do?

Answer 5

enables humans to react to their surroundings and to coordinate their behaviour

Question 6

Describe the pathway through the nervous system, starting at the receptor.

Answer 6

• information from the receptors passes to the central nervous system
• the CNS coordinates the response of effectors, ie muscles contracting or glands secreting hormones

Question 7

What’s the central nervous system?

Answer 7

brain and spinal cord

Question 8

describes how the body makes a response.

starting at the stimulus

Answer 8

stimulus –> Receptor –> Coordinator –> Effector –> Response

Question 9

What is a reflex action?

Answer 9

an automatic and rapid response to a stimulus so they can protect the body

they do not involve the conscious part of the brain

Question 10

How do we detect pain?

Answer 10

1) pain stimulus is detected by receptors
2) impulses from the receptor pass along a sensory neurone to the CNS
3) From the CNS An impulse then passes through a relay neurone
4) A motor neurone carriers impulses to the effector
5) the effector (usually a muscle) responds

Question 11

What is the role of a sensory neurone?

Answer 11

A sensory neurone carries signals from the receptors to the spinal cord or brain.

Question 12

What is the role of a relay neurone?

Answer 12

A relay neurone carries messages from one part of the CNS to another

Question 13

What is the role of a motor neurone?

Answer 13

Motor neurones carry signals from the CNS to effectors.

Question 14

How are electrical impulses carried between neurones?

Answer 14

Between neurons are junctions called synapses. electrical impulses trigger the release of chemical signals - neurotransmitters. The neurotransmitter diffuses across the synapse where it is then converted back into an electrical impulse.

neurones are not directly connected to each other

Question 15

What does the brain control and what is it made up of it?

Answer 15

The brain controls complex behaviour.

It is made of billions of interconnected neurones and has different regions that carry out different functions.

Question 16

What are the main regions of the brain?

Answer 16

cerebral cortex, medulla and the cerebellum

Question 17

What is the role of the cerebral cortex?

Answer 17

The cerebral cortex is concerned with:

Consciousness
Intelligence
Memory
Language

Question 18

What is the role of the cerebellum?

Answer 18

The cerebellum coordinates movement and balance.

Question 19

What is the role of the medulla?

Answer 19

The medulla controls unconscious (automatic) activities such as controlling heartbeat, breathing and the movements of the gut.

Question 20

Explain why it is difficult to investigate and treat brain disorders.

Answer 20

The complexity and delicacy of the brain makes investigating and treating brain disorders very difficult.

Drugs do not always reach the brain through the membranes that surround it.

investigation of brain function could cause physical damage to the brain or increased problems with brain function

Question 21

How do scientists use patients with brain damage to study the brain?

Answer 21

the effect the brain damage has on the patient can tell you a lot about what the damaged part of the brain does

Question 22

How do scientists use electrically stimulating to study the brain?

Answer 22

• by pushing a tiny electrode into the tissue and giving it a small zap of electricity
• by observing what stimulating different parts of the brain does, it’s possible to get an idea of what these parts do

Question 23

How do scientists use MRI scans to study the brain?

Answer 23

by producing very detailed pictures of the brain’s structure, scientists can use it to find out what areas of the brain are active when people are doing activities

Question 24

What does the retina do?

what is it?

what does it contain?

Answer 24

contains receptor cells that are sensitive to the brightness and colour of light

allows us to detect light intensity and light colour

Question 25

What does the optic nerve do?

Answer 25

carries impulses from the retina to the brain

Question 26

What does the sclera do?

Answer 26

tough supporting wall of the eye

protects the eye from serious damage

Question 27

What does the cornea do?

Answer 27

transparent outer layer founded at the front of the eye

it refracts light into the eye

Question 28

What does the iris do?

Answer 28

contains muscles that allow it to control the diameter of the pupil and therefore how much light enters the eye

Question 29

What does the ciliary muscles and suspensory ligaments do?

Answer 29

changes the shape of the lens to focus light on the retina

Question 30

What happens to the eye when the light receptors in the eye detect bright light

Answer 30

• reflex is triggered that makes the pupil smaller
• circular muscles in the iris contract and the radial muscles relax
• this reduces how much light can enter

Question 31

What happens to the eye when the light receptors in the eye detect dim light

Answer 31

• radial muscles contract

- circular muscles relax which makes the pupil wider

Question 32

What is accommodation?

Answer 32

the process of changing the shape of the lens to focus on a near or far object

Question 33

What does the eye do to focus on a near object?

Answer 33

• cilliary muscles to contract
• suspensory ligaments loosen
• lens is then thicker and more curved. refracts light stronger

Question 34

What does the eye do to focus on a far object?

Answer 34

• ciliary muscles loosen
• suspensory ligaments are pulled tight
• lens is pulled thin and only slightly refracts light rays

Question 35

What are the two common defects of the eye?

Answer 35

myopia and hyperopia

Question 36

What is myopia?

how is the eye

Answer 36

short-sightedness

• lens is too curved, so too thick, distant objects appear blurry
• eyeball is too long = light rays focused on a point in front of the retina

Question 37

What is hyperopia?

how is the eye

Answer 37

long-sightedness

• lens too flat, not thick enough, cannot refract light enough
• eyeball too short = light rays focus behind the eye

Question 38

How is myopia fixed?

Answer 38

uses glasses with a concave lens

• lens curve inwards to correct it so that the light rays focus on the retina, by partially unfocusing the light before it enters the eye

Question 39

How is hyperopia fixed?

Answer 39

glasses with a convex lens

• lens refract light rays so they focus on the retina

Question 40

What are the different types of treatments for the eye?

Answer 40

• spectacle lenses
• hard and soft contact lenses
• laser surgery to shape the cornea and add replacement lens

Question 41

What happens to the muscle when it detects pain?

Answer 41

it contracts
it becomes smaller

• this moves the muscle away from the object hurting it = protection