B10 Human nervous system

Question 1

what is homeostasis

Answer 1

regulation of internal conditions to maintain optimum cell function in response to internal and external changes

Question 2

what are 3 internal conditions that need to be kept balanced

Answer 2

body temperature

body water content

blood glucose concentration

Question 3

what is an automatic control system

Answer 3

the system that detects changes and responds to them for example nervous responses in nervous system and chemical responses in hormone system

Question 4

what are receptors

Answer 4

cells that detect changes (stimuli) in the internal or external environment

Question 5

what is a coordination centre

Answer 5

areas that receive and process information from receptors. They send out signals and coordinate the response of the body eg brain, spinal cord and pancreas

Question 6

what are effectors

Answer 6

muscles or glands that bring about responses to the stimulus that has been received

Question 7

what happens when a sensory receptor detects a stimulus

Answer 7

the information is sent as an electrical impulse that passes along special cells called neurones (found in bundles known as nerves)
The impulse travels along the sensory neurone until it reaches the CNS (brain)
The brain sends impulses out along motor neurones which carry the information to the effectors which respond

Question 8

what are reflexes

Answer 8

responses that are so fast that they happen subconsciously eg blinking

Question 9

what are relay neurones

Answer 9

found in the CNS and they connect a sensory neurone and a motor neurone

Question 10

what is the reflex arc pathway

Answer 10

receptor - sensory neurone- CNS - relay neurone- motor neurone- effector organ

Question 11

what are synapses and how do they work

Answer 11

gaps between neurones. The electrical impulses have to travel across the synapses by chemical diffusion which is slower than the speed they travel in the neurone but is the only way

Question 12

how is the reflex pathway different from a normal conscious action

Answer 12

in a reflex action the coordinator is a relay neurone either in the spinal cord or the unconscious area of the brain

Question 13

what is the function of the cerebral cortex

Answer 13

consciousness, intelligence, memory and language

Question 14

what is the function of the cerebellum

Answer 14

coordinating muscular activity and balance

Question 15

what is the function of the medulla

Answer 15

unconscious activities eg controlling heartbeat, breathing and movement of the gut

Question 16

what is the function of the hypothalamus

Answer 16

controlling body temperature

Question 17

what is the sclera

Answer 17

white outer layer of the eye. tough and strong making the eyeball not easy to damage

Question 18

what is the cornea

Answer 18

the transparent area at the front of the sclera. lets light into the eye and the curved surface is important for changing the direction of light as it enters the eye so that when they enter they are focused on the retina

Question 19

what is the role of the muscular iris

Answer 19

controls the size of the pupil by contracting or relaxing to control the amount of light that enters the eye

Question 20

what holds the lens in place in the eye

Answer 20

suspensory ligaments and ciliary muscles

Question 21

what does the optic nerve do

Answer 21

carries impulses form the retina to the brain

Question 22

how does the eye focus on a distant object

Answer 22

ciliary muscles relax so that the suspensory ligaments are pulled tight and the lens is pulled flat and thin. Only refracts light rays slightly so they are focused on the retina

Question 23

how does the eye focus on a near object

Answer 23

ciliary muscles contract so the suspensory ligaments loosen. The lens is then thicker and more curved and refracts light rays strongly so they are focused on the retina

Question 24

what causes you to see blurred images

Answer 24

when the light rays aren’t focused on the retina

Question 25

why do many old people need reading glasses

Answer 25

as you age, the lens hardens, accomodation gets more difficult making it harder to focus on close objects

Question 26

what is myopia

Answer 26

when you can’t see things far away because the light is focused in front of the retina maybe as a result of a lens that is too curved or a long eyeball
treated by wearing glasses with a concave lens

Question 27

what is hyperopia

Answer 27

when close objects are blurred maybe as a result of a lens that is too flat and thin or a short eyeball. The light is focused behind the retina. Treated by wearing glasses with a convex lens

Question 28

why is it difficult to study the brain

Answer 28

encased in the skull

delicate, easy to damage

Question 29

why is it difficult to treat brain disorders

Answer 29

easy to cause damage during surgery

many drugs can’t pass through the surrounding membranes

Question 30

how does light from an object form an image on the retina

Answer 30

light rays enter the eye through the cornea where they are refracted a little. they then travel through the pupil and lens. they are then refracted further to meet the retina and form an image upside down