coordination

Question 1

stimulus

Answer 1

a stimulus is a change in an animal’s surroundings

Question 2

response

Answer 2

a response is a reaction to the stimulus

Question 3

receptors

Answer 3

receptors are cells/tissues or organs that detect changes in stimuli

Question 4

the role of receptors

Answer 4

the role of any receptor is to detect the stimulus by changing its energy into the electrical energy of the nerve impulses, this impulse travels down nerve cells (neurons) to the central nervous system and to an effector, the effector creates the response

Question 5

receptors and type of energy received

Answer 5

• eye (retina)= light
• ear (organ of hearing)= sound
• ear (organ of balance)= mechanical (kinetic)
• tongue (taste buds)= chemical
• nose (organ of smell)= chemical
• skin (touch/pressure/pain receptors)= mechanical (kinetic)
• skin (temperature receptors)= heat
• muscle (stretch receptors)= mechanical (kinetic)

Question 6

biological name for a nerve cell

Answer 6

neurone

Question 7

how impulses work

Answer 7

the impulses that travel along a neurone are caused by movements of charged particles (ions) in an out of the neurone.

Question 8

the nervous system is made of

Answer 8

the central nervous system: brain, spinal chord

nerves made of cells called neurones: sensory neurones, motor neurones, relay neurones

Question 9

adaptations of a motor neurone

Answer 9

• cell body: contains the nucleus
• long axon: carries impulses long distances
• many dendrite connections: collect information from other neurones
• many nerve endings: sends information to neurones
• myelin sheath: protects and insulates the axon, speeds up the conduction of impulses

Question 10

multiple sclerosis

Answer 10

immune system attacks the myelin sheath that protects nerve fibres, causes communication problems between the brain and the rest of the body

Question 11

functions of the human eye

Answer 11

detects light, can form a proper image, can distinguish colors

Question 12

structure of the retina

Answer 12

the retina contains light sensitive cells called photoreceptors, rods are sensitive to light and dark, cones are sensitive to red, green, and blue

Question 13

sclera

Answer 13

tough outer coat of the eye, the visible, white part of the eye

Question 14

forming an image

Answer 14

in order to form an image on the retina, light needs to be bent or refracted. in the eye light is first refracted at the air/cornea boundary, then again at the lens. as a result of refraction at the cornea and lens, the image on the retina is inverted. the brain interprets the image the right way up.

Question 15

the role of the iris

Answer 15

the role of the iris is to control the amount of light entering the eye, by changing the size of the pupil

Question 16

the iris muscles

Answer 16

the iris contains two types of muscles: circular muscles form a ring shape in the iris, and radial muscles lie like the spokes of a wheel.

In bright light the pupil is constricted (made smaller) because the circular muscles contract and the radial muscles relax

in dim light the pupil is dilated (made bigger) because the circular muscles relax and the radial muscles contract

Question 17

the iris reflex

Answer 17

whenever our eyes look from a dim light to a bright one, the iris rapidly and automatically adjusts the pupil size (reflex action). the purpose of the iris reflex is to allow the right intensity (brightness) of light to fall on the retina. Light that is too bright could damage the rods and cones, and light that is too dim would not form an image.

Question 18

iris reflex route from stimulus to response

Answer 18

stimulus (Light intensity)

retina (receptor)

sensory neurones in optic nerve

unconscious part of brain

motor neurones in nerve to iris

iris muscles (effector)

response (change in size of pupil

Question 19

the blind spot

Answer 19

there is one area of the retina where an image cannot be formed, this is where the optic nerve leaves the eye. at this position there are no rods or cones, so it is called the blind spot. the retina of each eye has a blind spot but because the brain puts the images from each eye together, the blind spots of both eyes are cancelled. additionally the optic nerve leaves the eye towards the edge of the retina where vision is not very sharp anyways.

Question 20

when focusing on a distant object

Answer 20

the ciliary muscles relax, the suspensory ligaments are pulled tight, the lens is less convex (flatter)

Question 21

when focusing on a nearby object

Answer 21

the ciliary muscles contract, the suspensory ligaments slack, the lens is more convex (rounded)

Question 22

accommodation

Answer 22

the changes that take place in the eye which allow us to see objects at different distances

Question 23

a reflex arc is

Answer 23

the nerve pathway of a reflex

Question 24

reflex arc detailed example

Answer 24

the stimulus is detected by temperature or pain receptors in the skin. these generate impulses in sensory neurones which enter the central nervous system through a part of the spinal cord called the dorsal root. in the spinal cord the sensory neurones connect by synapses with short relay neurones, which in turn connect with motor neurones. the motor neurones emerge from the spinal cord through the ventral root, and send impulses back to the muscles of the arm. these muscles then contract, pulling the arm (and thus finger) away from the harmful stimulus.