[Cells & Control2]Nervous system + the eye Flashcards
What is a stimulus?
A change in internal or external environment or surroundings
What is a response?
A reaction to the change
State the order that the coordinated response happens in (5)
STIMULUS RECEPTOR COORDINATOR EFFECTOR RESPONSE
What does a response organ do?
It detects a stimulus
What does an effector organ do?
Carries out the response
What does a receptor do?
Detects the change in the environment and changes its energy form into electrical energy, which can then be sent via the nervous system
Give two examples of a receptor and what energy it converts into nerve impulses
Eye coverts light energy into nerve impulsesEar converts sound energy into nerve impulses
What is Transduction?
The changing of energy from one form to the other
What do motor nerves do?
Carry information FROM the central nervous system (CNS)
What do sensory nerves do?
Carry information TO the Central Nervous System (CNS)
What is the central nervous system?
The brain and spinal cord
What is the peripheral nervous system?
Sensory nerves and motor nerves
What is the function of the nervous system?
To carry messages to and from the brain to all parts of the body
What are the parts of a neuron?
Nerve cell bodyCytoplasmNucleus DendritesAxon
What is the axon and what does it do?
It is long and fibrous and connects the cell body to parts of the body (eg muscles)
What do the dendrites do?
Connect various nerve cell bodies together
What do motor neurons do?
Transmit impulses to muscles enabling a response
What do the sensory neurons do?
Impulses from the receptors pass along then until they reach the CNS (brain or spinal cord)
Where is the cell body found on a motor neuron?
At the start
Where is the cell body found in a sensory neuron?
In the middle
What does the cell body do on a sensory neuron?
It decides where the impulses go (brain or spinal cord)
What does the axon do on a sensory neuron?
Carries out decision
Give an example of a stimulus
Heat, pain, sound or anything else that makes sense lol
What is reaction time?
The interval time between the presentation of a stimulus and the start of the muscular response
What are stimulants? Give an example
Drugs that increase brain activity eg nicotine caffeine ecstasy
What are depressants? Give an example
Drugs that slow down brain activity eg alcohol solvents temazepan
What is a synapse?
The gap between the axon of a sensory neuron and the sense ok of a motor neuron.
How do synapses work?
Electrical impulse travels along axonTriggers nerve ending of neuron to release neurotransmitters (chemicals)These chemicals diffuse across synapse and bind with receptor molecules on the membrane of next neuronThe receptor molecules bind only to the specific chemicals released from first neuronThis stimulates second neuron to transmit the electrical impulse
How do synapses affect your reaction time?
Make it slower because it takes time for chemicals to diffuse across synapse
What is a reflex action?
A rapid, involuntary response to a stimulus
What is the purpose of a reflex action?
To protect the body
What does an involuntary response mean?
That it is not started by impulses from the brain
Give 3 examples of reflexes
Startle reflexWithdrawal reflexIris reflex
What does the grey matter in the spinal cord contain?
Mainly cell bodies (intellectual part)
What does the white matter in the spinal cord contain?
Axons and fatty myelin sheath
Function of cornea
It refracts the light and protects the eye
Function of iris
Controls how much light enters the pupil
How does the iris work
It changes the shape of the pupils using circular and radial muscles
What characteristic to circular and radial muscles have?
They are antagonistic
What does the iris do in bright light?
Circular muscles contract Radial muscles relaxPupils constrict
What does the iris do in dim light?
Circular muscles relaxRadial muscles contractPupils dilate
Function of the lens
Focuses light onto the retina
Function of the ciliary muscles
Help change the shape of the lens in accommodation
What is the process called that controls how your eyes focus
Accommodation
What is accommodation?
When the lens changes shape to cause more or less refraction depending on the distance of the object controlled by the ciliary muscles and suspensory ligaments
What happens in accommodation with a distant object
Ciliary muscles relax Suspensory ligaments tighten Lens is pulled thin (to allow more refraction)
What happens in accommodation with a close object
Ciliary muscles contractSuspensory ligaments slacken Lens becomes fatter (to allow less refraction)
Function of the optic nerve
The bundle of sensory neutrons that carry impulses to the brain
Function of the retina
Layer of tissue at the back of the eye that contains photoreceptors cells called rods and cones
When do rod cells work and what colour to they see in
In dim light and can only see in black and white
When do cone cells work and what colour do they see in
In bright light and detect the colours red, green and blue
Function of the fovea
Area of the retina with the highest concentration of cone cells that provide sharp vision
Function of the aqueous humour
Maintains the pressure in the eye and nourishes the cornea
Function of the vitreous humour
Maintains the shape of the eye and attaches to the retina
Function of the sclera
Tough outer layer that extra-ocular muscles can attach to
Function of the pupil
Hole in the centre of the eye that lets light in
What makes up a neurone?
cell bodyDendritesAxon
What is the job of sensory neurones
Carry information from the sense organs to the CNS and detect changes outside the body
What is the job of motor neurones?
To carry instructions from the CNS to the effector organs (muscles and glands)
What is the job of neurones?
To carry electrical impulses
What controls the amount of light entering your eye?
The pupil reflex
What do chemical transmitters do?
They diffuse across the synapse to reach the next neurone
What does a relay Neuron do?
Pass messages between neurons in the CNS
What do we need for a coordinated response?
A stimulus and a response
