Unit 2.5 - Response and Regulation

Question 1

Define a sense organ

Answer 1

An organ comprised of a group of receptor cells which responds to a particular stimulus.

Question 2

What stimuli do the sense organs respond to?

Answer 2

Eyes - light
Ears - sound
Skin - Touch/Temperature/Pressure
Nose - Chemicals (smell)
Mouth - Chemicals (taste)

Question 3

What is the nervous system made up of?

Answer 3

The brain, spinal chord and all the body’s nerves

Question 4

What are the central nervous system and peripheral nervous system?

Answer 4

CNS - Brain and Spinal Chord

PNS - Nerves that carry information to or from CNS

Question 5

What are the properties of a reflex action?

Answer 5

Fast, automatic/involuntary, some are protective

Question 6

In the reflex action of a hand being damaged by a cactus, what are the different components of the reflex arc?

Answer 6

Stimulus - Spines on cactus
Receptor - Receptor cells in skin
Sensory neurone - Neurone carrying impulse from receptor cells in skin to co-ordinator
Co-ordinator - Spinal chord
Relay neurone - Inside spinal chord, relays impulse from sensory neurone to motor neurone
Motor neurone - neuron carrying impulse from co-ordinator to effector
Effector - Muscles in arm
Response - pulling away from the cactus

Question 7

What is a synapse and where does it appear in a reflex arc?

Answer 7

It is a small gap between the neurones over which the electrical impulse must pass when it goes from one neurone to another.

Question 8

Define the sclera

Answer 8

Protective, tough white outer coat of eye

Question 9

Define the cornea

Answer 9

The clear part of the sclera, which allows light to enter and refracts light entering.

Question 10

Define the pupil

Answer 10

The hole in the center of the iris which allows light to enter.

Question 11

Define the iris

Answer 11

Muscles which alter the size of the pupil to control the amount of light entering the eye.

Question 12

Define the lens

Answer 12

The lens changes shape to focus light onto the retina.

Question 13

Define the choroid

Answer 13

A pigmented layer which absorbs light to prevent reflection, also contains blood vessels.

Question 14

Define the retina

Answer 14

A light sensitive layer where the image is formed and sent to optic nerve.

Question 15

Define the optic nerve

Answer 15

The nerve which carries impulses from the eye to the brain.

Question 16

Define the blind spot

Answer 16

The point where the optic nerve leaves the eye, so there are no light sensitive cells here.

Question 17

Why must animals keep their internal conditions constant and which conditions must be kept constant?

Answer 17

Metabolism (all the chemical reactions in cells, including respiration) only operates within a narrow range of temperature and pH, and requires appropriate nutrients and water - keeping internal conditions constant is called homeostasis.

Question 18

What are hormones?

Answer 18

Chemical messengers released by glands and carried by the blood which control many body functions.

Question 19

Why is homeostasis of blood glucose levels important?

Answer 19

Glucose is required for respiration, so it is important that blood glucose levels are kept at a constant level.

Question 20

What happens when blood glucose levels increase and when might this happen?

Answer 20

After eating a meal containing sugar or starch - pancreas releases the hormone insulin (a protein) into the blood, which causes the liver to convert glucose to insoluble glycogen, and the storing it, decreasing the blood glucose level.

Question 21

What happens when blood glucose levels decrease and when might this happen?

Answer 21

After exercising, or a while after eating - pancreas releases glucagon, which breaks down glycogen stored in the liver into glucose, raising the blood glucose level.