The Nervous System

Question 1

Relationship between receptors, the central nervous system and the effectors.

Answer 1

Stimuli—>central nervous system—-> effectors

Question 2

What is reflex arc

Answer 2

A reflex arc is the shortest pathway by which nerve impulses travel from the receptor to the effector in a reflex action.

Question 3

Function of sensory neurones

Answer 3

Transmits nerves impulses from the sense organs to the central nervous system.

Question 4

Function of relay neurone

Answer 4

Transmits never implises from the sensory neurone to the motor neurone

Question 5

Function of motor neurone

Answer 5

Transmits nerve impulses from the central nervous system to the effectors.

Question 6

Reflex centres

Answer 6

• Cranial reflexes—> controller by the brain( unconsciously)

- Spinal reflexes—> controlled by the spinal cord

Question 7

What happens when you touch a hot object?

Answer 7

1. The heat on the object stimulates the thermal receptors in your skin. Electrical impulses are produced.
2. The electrical impulses travel along the sensory neurone to the spinal cord.
3. In the spinal cord, the electrical impulses are transmitted first across a synapse to a relay neurone, then across another synapse to the motor neurone.
4. The motor neurone transmits the electrical impulses from the spinal cord to the muscle tissues in the affected arm.
5. The biceps muscle contract and causes the hand to withdraw suddenly.

Question 8

Function of iris

Answer 8

Structure: a circular sheet of muscles
Functions:
1. It contains a pigment that gives the eye its colour
2. It controls the amount of light entering the eye with the circular muscles and radial muscles

Question 9

Function of conjunctiva

Answer 9

Structure: a thin transparent membrane covering the sclera
Function:
1. It secretes mucus to keep the eyeball moist.

Question 10

Sclera or sclerotic coat

Answer 10

Structure: A tough white outer covering of the eyeball
Function:
1. Protects the eyeball from mechanical injuries.

Question 11

Pupil

Answer 11

Structure: A hole in the Centre of the iris
Function: allows light to enter the eye.

Question 12

Eyelashes

Answer 12

Function: shield the eye from dust particles

Question 13

Eyelids

Answer 13

Functions:
1. Protects the cornea from mechanical injuries.
2.

Question 14

Tear gland

Answer 14

1. Secretes tears—> wash away dust

Question 15

Ciliary body

Answer 15

1. Contains ciliary muscles which control the curvature/thickness of the lens

Question 16

Suspensory ligament

Answer 16

1. A connective tissue that connects the edge of the lens to the ciliary body

Question 17

Cornea

Answer 17

1. Refracts light into the eye

Question 18

Aqueous chamber

Answer 18

The space between the lens and the cornea—>filled with aqueous humour

1. Keeps the front of the eyeball firm
2. Helps to refract light into the pupil

Question 19

Lens

Answer 19

1.focuses light onto the retina

Question 20

Choroid

Answer 20

1. It is pigmented black to prevent internal reflection of light
2. It contains blood vessels that transport oxygen and nutrients to the eyeball and remove excretory products from the eye

Question 21

Vitreous chamber

Answer 21

The space behind the lens—>filled with vitreous humour

1. Keeps eyeball firm
2. Helps refract light onto the retina

Question 22

Yellow spot/fovea

Answer 22

Contains the greatest concentration of cones but no rods

1. Where images are normally focused

Question 23

Optic nerve

Answer 23

1. Transmits nerve impulses to the brain when photoreceptors in the retina are simulated

Question 24

Blind spot

Answer 24

Not sensitive to light

Question 25

Retina

Answer 25

Contains photoreceptors—> connected to the nerve endings from the optic nerve

Question 26

Function of cones and rods

Answer 26

Cones: Enable is to see colors in bright light Rods: more sensitive than cones —> enable us to see in dim light but only in black and white

Question 27

Pupil reflex in bright light

Answer 27

BCCRRPC 1. The circular muscles of the iris contract 2. The radial muscles of the iris relax 3. The pupil constricts—> reducing the amount of light entering the eye.

Question 28

Pupil reflex in dim light

Answer 28

DRCCRPD 1. The radial muscles of the iris contract 2. The circular muscles of the iris relax 3. The pupil dilates—>increasing the amount of light entering the eye.

Question 29

Focusing on a distant object

Answer 29

DOCRPSL 1. The ciliary muscles relax, pulling on the suspensory ligaments. 2. Suspensory ligaments become taut, pulling on the edge of the lens. 3. Lens becomes thinner and less convex, increasing its focal length. 4. Light rays from the distant object are sharply focused on the yellow spot. 5. Cones in the yellow spot are stimulated. 6. Electrical impulses produced are transmitted by optic nerve to the brain—> interprets the impulses, allowing the person to see the distant object.

Question 30

Focusing on near object

Answer 30

NOCC 1. Ciliary muscles contract, relaxing their pull on the suspensory ligaments. 2. Suspensory ligaments slacken, relaxing their pull on the lens. 3. The lens becomes thicker and more convex, decreasing its focal length. 4. Light rays from the near object are sharply focused on the yellow spot. 5. Cones in the yellow spot are stimulated. 6. Electrical impulses are produced and transmitted by the optic nerve to the brain—>interprets the impulses, allowing the person to see the near object.

Question 31

Definition of hormone

Answer 31

It is a chemical substance, produced by a gland, carried by the blood, which alters the activity of one or more specific target organs and is then destroyed by the liver.

Question 32

What is an endocrine gland?

Answer 32

The hormone produced by an endocrine gland directly enters the bloodstream. The islets of Langerhans secrete hormones insulin and glucagon directly into the bloodstream.

Question 33

Effects of adrenaline

Answer 33

1.

Question 34

Signs of diabetes mellitus

Answer 34

- persistently high blood glucose level - presence of glucose in the urine after a meal - healing of wounds is slow and difficult

Question 35

Effects of glucagon

Answer 35

The target of glucagon is the liver 1. Stimulates the liver cells to convert glycogen into glucose 2. Stimulating the conversion of fats and amino acids into glucose