Chap 12 & 13 : Nervous System And Eye

Question 1

What does your central nervous system consist of

Answer 1

Brain and spinal cord

Question 2

What does your peripheral nervous system consist of

Answer 2

Cranial and spinal nerves

Question 3

Name the 3 types of neurones and their function

Answer 3

Sensory : Transmit nerve impulses from sense organ to CNS
Motor : Nerve impulse from CNS to effector organ
Relay : intergrate info, may send impulses to motor neurones

Question 4

What is the difference between axon and dendron ?

Answer 4

An axon is a nerve fibre that transmits nerve impulses away from the cell body while a dendron is a nerve fibre that transmits nerve impulses toward the cell body

Question 5

What is the function of the myelin sheath

Answer 5

Layer of fatty substance which insulates and shields the nerve fibre, maintains the nodes of ranvier

Question 6

What is the function of the nodes of ranvier

Answer 6

Region where myelin sheath is absent. Allows nerve impulses to jump from node to node speeding up transmission

Question 7

What is the synapse ?

Answer 7

Junction between 2 neurones or bewteen neurone and effector

Question 8

How are nerve impulses transmitted across the synapse

Answer 8

Presynaptic cell secrets a chemical signal ( neurotransmitter )
Neurotransmitter binds to a specific receptor on the postsynaptic cleft

Question 9

What is a nerve

Answer 9

It is a bundle of nerve fibres enclosed in a sheath of connective tissue

Question 10

What does grey matter contain and where is it found

Answer 10

Cell bodes of neurones, inner layer of spinal cord outer layer of brain

Question 11

What is white matter composed of and where is it found

Answer 11

Nerve fires , central part of brain and outer layer of spinal cord

Question 12

How many pairs of spinal nerves do you have

Answer 12

31

Question 13

What is the difference between the dorsal root and ventral root

Answer 13

Dorsal root contains only sensory neurones, Ventral root contains only motor neurones
Dorsal root is above the ventral root
Dorsal root has a dorsal root ganglion which is where the cell bodies are

Question 14

Describe the pathway of the reflex arc

Answer 14

1 a receptor or sense organ
2 sensory neurone
3 relay neurone
4 Motor neurone
5 effector

Question 15

How does our iris control the amount of light entering our eye

Answer 15

Circular and Radial muscles, a pair of antagonistic muscles.
In bright light, circular muscle contract, radial muscles relax
In dim light, vice versa

Question 16

Focusing or accommodation occurs when focusing on objects at different distances, how does a person focus on a distant object

Answer 16

Cilliary muscles relax, pulling on the suspension ligaments
Super sorry ligaments become taut, pulling on the edge of the lens
The lens becomes thinner and less convex, INCREASING FOCAL LENGTH
Light rays are focused onto the retina , stimulating photoreceptors
Nerve impulses are transmitted o the brain, which is interpreted by the brain that allows a person to see the object

Question 17

How does a person focus on a near object

Answer 17

Cilliary muscles contract, replacing their pull on suspensory ligaments
Suspensory ligaments slacken their pull on the lens
Lens become thicker and more convex, decreasing in focal length
Light is focused onto retina stimulating photoreceptors

Question 18

What are rods ?

Answer 18

Enable us to see in dim light, but only black and white.
Contain a pigment called visual purple, which gets bleached in bright light
Time is taken for visual purple to reform the rods, that’s why when moving from one place to another roof different brightness, we are unable to see
Formation of visual purple requires vitamin a, person with vitamin a deficiency suffers night blindness

Question 19

What are cones

Answer 19

Allow us to see colour in bright light
3 different types of cones containing 3 different pigments (RGB)
Cones do not work well in dim light