Senses and Reflexes Flashcards
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?
Stimuli
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
MOTOR NEURONE: - dendrites - nucleus - cell body - axon - electrical impulse - insulating sheath SENSORY NEURONE: - 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
include:
- 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
include:
- 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
Cornea
Refracts light - bends it as it enters the eye
Iris
Controls how much light enters the pupil
Lens
Further refracts light to focus it onto the retina
Retina
Contains the light receptors
Optic Nerve
Carries impulses between the eye and the brain
Sclera
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
include:
- 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
label a diagram of an eye in bright light and an eye in dim light
include:
- pupil
- iris
- scelera
- radial muscles contract
- circular muscles contract
what happens to the muscles in the pupil in bright light
in bright light, the circular muscles contract and the radial muscles relax, making the pupil smaller. this prevents damage to the light sensitive cells on the retina
what happens to the muscles in the pupil in dim light
in dim light, the radial muscles contract and the circular muscles relax, making the pupil bigger and allowing more light into the eye
describe how the amount of light entering or leaving the eye is controlled
- the amount of light entering the eye is controlled by the iris
- this contains muscle which is able to contract and change the size of the pupil, which is a hole in the centre of the eye
- the iris contains two types of muscle; circular and radial
what is the bending of light called?
refraction
why do peoples vision get worse when they age
their lens becomes less bendy
what is the difference between a simple and conditioned reflex?
a simple reflex is natural and automatic, whereas a conditioned reflex is learnt
in a neurone, the axon carries information along the neurone as…
…electrical impulses
what is homeostasis
the maintenance of a constant internal environment. The nervous system and hormones are responsible for this. e.g the concentration of carbon dioxide in the blood being carefully controlled, body temperature, body water content
What are auxins in plants?
- Auxins are a family of plant hormones. They are mostly made in the tips of the growing stems and roots, which are known as apical meristems, and can diffuse to other parts of the stems or roots.
- Auxins control the growth of plants by promoting cell division and causing elongation in plant cells (the cells get longer).
- Stems and roots respond differently to high concentrations of auxins:
- cells in stems grow more
- cells in roots grow less
how do auxins cause plants to grow toward light
In a stem, the shaded side contains more auxin and grows longer, which causes the stem to grow towards the light. It is vital to note that the plant does NOT bend towards the light.
