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Flashcards in Senses and Reflexes Deck (41)
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Why do we need to be able to sense changes in our environment?

So that we can respon - for safety


What do we call changes in the environment?



How do we detect stimuli/ changes in the environment?

Using receptors


Name the sense organ and stimulus to the sense: touch

Sense organ: skin
Stimulus: pressure, pain, temperature


Name the sense organ and stimulus to the sense: taste

sense organ: tongue
stimulus: chemicals in food & drink


Name the sense organ and stimulus to the sense: smell

sense organ: nose
stimulus: chemicals in the air


Name the sense organ and stimulus to the sense: sight

sense organ: eyes
stimulus: light


Name the sense organ and stimulus to the sense: hearing

sense organ : ears
stimulus: sound


how are organisms able to respond to changes in their environment?

- using receptors to detect the stimuli


The Central Nervous System

- CNS made up of the spinal chord and the brain
- Peripheral nervous system carries information to or from the CNS
- When a stimulus is detected by a receptor, impulses pass down neurones to the CNS which sends more impulses out along neurones to an effector which causes a response


label a diagram of a sensory and motor neurone

- dendrites
- nucleus
- cell body
- axon
- electrical impulse
- insulating sheath
- dendrites
- nucleus
- cell body
- axon
- electrical impulse
- insulating sheath


what are synapses

- the gaps between neurones are called synapses
- the impulse is transmitted from one side to the other using neurotransmitters, which travel across the gap via diffusion
- synapses mean that nerve impulses are unidirectional, meaning they only travel in one direction
- they can also connect more than one neurone


label a diagram of a synapse

- end of neurone
- neurotransmitters
- neurone
- sacs containing neurotransmitters
- synapse


What are neurones?

-specialised cells which make up nerves
- sensory neurones carry impulses from sense organ to CNS
- relay neurones are found inside the CNS and connect sensory and motor neurones
- motor neurones carry impulses from the CNS to effectors (muscles or glands)


draw a diagram of the reflex arc

- sensory neurone
- motor neurone
- relay neurone
- spinal chord
- impulse
- receptor
- effector


what is a reflex

a reflex is an automatic and rapid response, such as when you touch something hot or sharp.


Describe as a series of statements how a person moves their hand from a hot object?

- receptors in the sense organs detect a stimulus such as high temperature
- an impulse is transmitted along the sensory neurone to the spinal cord
- the impulse is passed to a relay neurone
- the relay neurone transmits the impulse to the motor neurone
- the motor neurone causes the muscle in the arm to contract
- the hand is moved away from the hot object



Refracts light - bends it as it enters the eye



Controls how much light enters the pupil



Further refracts light to focus it onto the retina



Contains the light receptors


Optic Nerve

Carries impulses between the eye and the brain



Tough white outer layer of the eye. It helps protect the eye from injury


Describe the pupil reflex

pupils get smaller in bright light to regulate the amount of light which enters the eye


Describe the blink reflex

the blink reflex- eyes blink when there is near movement to potentially protect the eyes from damage,


Describe the swallowing reflex

makes it harder to swallow straight after having swallowed just before, to prevent the throat from over filling and therefore preventing choking


What part of the hand is most sensitive and why?

the palm of the hand is most sensitive as this area is designed to detect stimuli as the palm of the hand has more receptors than the other parts.


how does the eye focus light from a close object?

- light rays from a near object are diverging when they enter the eye and so need more bending to focus them onto the retina
- to do this, the lens must change shape and become more rounded
- to enable this, the ciliary muscles contract which means that the suspensory ligaments are pulled less and the lens becomes more rounded.


how does the eye focus light from a distant object?

- when light enters the eye from a distance, the light rays are almost parallel when they enter the eye
- this means they need less rarefaction to be focused onto the retina
- the cornea starts to bend the rays and the lens is less involved
- to get the lens into this shape, special muscles called ciliary muscles relax and the lens is pulled thinner by the suspensory ligaments


label a diagram the eye

- choroid layer (contains dark pigment to absorb light and prevents light from being reflected back into the eye)
- sclera (protective white outer layer, contains many blood vessels which supply the retina with food and oxygen)
- ciliary muscle (circular muscles around lens which helps to change its shape when they contract)
- cornea (refracts light)
-suspensory ligament (attaches lens to ciliary muscle)
- aqueous humour (fills the front of the eye and helps bend light onto the retina)
-iris (controls amount of light entering the eye)
-pupil (hole in centre of iris which lets light in)
- lens (helps focus image)
- vitreous humour (fluid which keeps shape of eyeball)
- blind spot (where the optic nerve attaches to the retina, there are no light sensitive cells)
- optic nerve (carries electrical impulses to the brain)
- fovea (the most sensitive part of the retina- contains only cones, makes image sharper)
- retina (contains light sensitive receptor cells)
- conjuctiva- thin clear layer over surface of they and lining of the eyelids