B10 - The Human Nervous System

Question 1

Define Homeostasis

Answer 1

the balancing act of regulating the internal conditions of a cell or organism to maintain optimal conditions for functioning in response to internal and external changes.

Question 2

Why is Homeostasis important?

Answer 2

Enzymes work the best in certain conditions, such as in a specific pH or temperature, and so to control functions of a cell it is important to maintain optimum conditions. If not optimal, then enzymes can denature, reducing their ability to catalyse metabolic reactions

Question 3

Controlled internal conditions

Answer 3

include – temperature, water content and blood glucose

Question 4

Stimuli

Answer 4

changes in the internal or external environment detected by receptors

Question 5

Receptors

Answer 5

cells that detect stimuli

Question 6

Example of sense organ

Answer 6

skin, eye, nose

Question 7

Coordination Centers

Answer 7

areas which receive and process the information from the receptors and then send out signals and coordinate the responses of the body. Include: the brain, the spinal cord and some organs (the pancreas)

Question 8

Effector

Answer 8

muscles or glands that respond to stimuli, the muscles contract and the glands secrete chemical substances and hormones

Question 9

Nerves

Answer 9

bundles of neurons (cells that pass along the electrical impulses

Question 10

CNS

Answer 10

(central nervous system) made up of the brain and spinal cord

Question 11

Sensory Neurons

Answer 11

The cells that carry the impulses to your CNS from your sense organs

Question 12

Motor neuron

Answer 12

carry information from the CNS to the rest of your body where the effectors respond.

Question 13

Reflex arc

Answer 13

A receptor detects a stimulus. The electrical impulse travels at through the sensory neurone to a CNS where the sensory neurone passes the impulse to the relay neurone via a synapse. The impulse is passed along to a muscle or gland, the effector.

Reflex actions are automatic, rapid and do not involve the conscious parts of the brain

Question 14

Synapses

Answer 14

junctions between neurones which form physical gaps. When an impulse reaches a synapse, a chemical is released which then diffuses across the synapse and then starts a new electrical impulse.

Question 15

Cerebral cortex

Answer 15

concerned with consciousness, intelligence, memory and language

Question 16

Cerebellum

Answer 16

concerned mainly with coordination muscular activity and balance

Question 17

Medulla

Answer 17

concerned with unconscious activities such as controlling your heartbeat, the movements of the gut and breathing

Question 18

Hypothalamus

Answer 18

controls body temperature

Question 19

Pituitary gland

Answer 19

produces hormones

Question 20

Electrically simulating different parts of the brain

Answer 20

this is when scientists expose the brain by removing the top of the scull and stimulate different areas to see the effects. This tends to be done on conscious patients as there are no sensory nerve endings in the brain.

Question 21

MRI scans

Answer 21

magnetic resonance imaging, is used to see which area of the brains affected after a
tumour or stroke

Question 22

Sclera

Answer 22

white outer layer, tough and strong to protect the eyeball.

Question 23

Cornea

Answer 23

transparent area at the front of the eye to let in light, curves surface refracts lights to focus on the retina

Question 24

Iris

Answer 24

controls size of the pupil by contracting or relaxing muscles

Question 25

Pupil

Answer 25

hole through which lights enters the eye

Question 26

Lens

Answer 26

a clear disk held in place by suspensory ligaments and cilary muscles. Fine tunes the light rays to produce a clear image on the retina.
If light is focused either in front or behind the reitna, the image is blurred.

Question 27

What do pupils do depending on the light intensity?

Answer 27

In dim light, the pupil is dilated to let more light in and in bright light the pupil becomes constricted to prevent damage to the light- sensitive cells in the retina

Question 28

Define Accomodation

Answer 28

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

To focus on distant objects: the ciliary muscles relax, suspensory ligaments tight and the lens flattens/thins

To focus on a near object: the ciliary muscles contract, suspensory ligaments loose and the lens gets thicker/ more curved

Question 29

Myopia

Answer 29

Short sightedness - result of curved lens or long eyeball, Treated with a concave leans. Image formed in front the retina

Question 30

Hyperopia

Answer 30

long sightedness - result of a flat and thin lens or short eyeball. Treated with a convex lens. Image formed behind the retina.

Question 31

Ways to treat eye problems

Answer 31

contact lenses, laser eye surgery (changes shape or thickness of the lens), replacement lenses.

Question 32

The body’s negative feedback loop

Answer 32

When our internal conditions are optimal, the body does not need to respond. If an internal condition changes and is no longer optimal, this stimulus is detected and the body works to counteract (reverse) the change and return conditions to the optimum. This process is called negative feedback and needs all of the components of the nervous system to work together.

Question 33

Positive Feedback

Answer 33

It makes a small change even bigger. An example of positive feedback in the body is the release of oxytocin (hormone), which increases the number of contractions during childbirth.

Question 34

Neurotransmitters

Answer 34

chemicals that diffuse across synapses and bind to receptors on the next neurone

Question 35

What happens at a synapse?

Answer 35

1. The electrical impulse reaches the end of the neurone before the synapse. This triggers the release of chemicals called neurotransmitters
2. The neurotransmitters diffuse across the synapse.
3. The neurotransmitters bind to receptors on the next neurone.
4. The presence of the neurotransmitter causes the production of an electrical impulse in the next neurone.