Coordination and Response Flashcards
What is a nerve impulse?
An electrical signal that passes along nerve cells called neurons
What does a receptor do?
Detects a change in stimulus
What does the central nervous system consist of?
Brain and spinal cord
What does the peripheral nervous system contain?
Every other part- nerves
Define voluntary action
An action completed with conscious thought and under our own will
Define involuntary action
An action completed without conscious thought
What is a relay neurone?
Short and are located in the CNS , connecting sensory and motor neurones
What is a sensory neurone?
Long and have a cell body branching off the middle of an axon. Carry impulses from sense organ to CNS
What is a motor neurone?
Long and have a cell body at one end with long dendrites branching off. Carry impulses from the CNS to muscles and glands.
Describe the simples reflex arc
- Stimulus is detected by receptor in the skin
- Sensory neurone sends electrical impulses to spinal cord
- Electrical impulse is passed on to a relay neurone in spinal cord
- Relay neurone carries impulse to motor neurone which carries it to a muscle in the arm
- Muscle contracts and pulls hand up and away from hot object
Define reflex action
Automatically and rapidly integrating and coordinating stimuli with the responses of effectors
Define synapse
Junction between two neurones
Describe a synapse
The impulse reaches the end of one neurone
Vesicles release neurotransmitters into synaptic gap
Neurotransmitter diffuses across gap and binds with receptors
New impulse is triggered in the next neurone
What do synapses ensure?
That impulses travel in one direction only
What substances affect synapses?
Heroin
alcohol
nicotine
Define sense organs
Groups of receptor cells responding to specific stimuli: light, sound, touch, temperature and chemicals
What does the cornea do?
Refracts light and helps to focus it
What does the iris do?
Controls how much light enters the pupil
What does the lens do?
Refracts light to focus it into the retina
What does the retina do?
Contains light receptors some sensitive to light of different colours
What is the optic nerve?
Transmits electrical impulses from retina to brain
What happens when the eye gets exposed to bright light?
The radial muscle contracts and the circular muscle relaxes and the pupil decreases in size letting less light in
What happens when the eye gets exposed to a lack of light?
The radial muscle relaxes and circular muscles contract and the pupil increases in size to let more light in
What happens when we are looking at a distant object?
Ciliary muscles relax
Suspensory ligaments stretch thin
lens become thinner
light is refracted less
What happens when we are looking at a near object?
Ciliary muscles contract
Suspensory ligaments slack
Lens becomes fatter
light is refracted more
Which cells do we have in our eye?
Rods and cones but there are more rods than cones
What does the fovea contain?
Only cone cells
What is the fovea?
An area on the retina with lots of photosensitive cells so it has the highest visual activity
When do rods function?
In low light intensities= night vision- greater sensitivity
What do cones do?
They detect red blue and green.
