The nervous System Flashcards
What are electrical impulses?
electric signals that pass through nerve cells as neurones
a nerve is…
a bundle of neurons
Sensory neurons are…
- long
- cell body branching off the middle of the axon
Relay neurons are…
- short
- small cell body at one end
Motor neurons are…
- long
- large cell body at one end, with dendrites branchin off it
Voluntary response:
- conscious decision making
- starts with brain as coordinator
- slow
Involuntary response:
- for protection
- rapid
- unaware action has been done
Pathway of the reflex arc:
stimulus, receptor, sensory neurone, relay neurone, motor neurone, effector, response
what is a synapse?
a junction between two neurones
How is an impulse passed across a synapse?
electrical impulse travels across the first axon
chemical messengers (neurotransmitters) fuse with the presynaptic membrane
neurotransmitters diffuse across the gap and bind with receptor molecules
Stimulates a second electrical impulse that travels down the second axon
neurotransmitters are then destroyed
What is the cornea?
transparent lens that refract light
What is the iris?
controls how much light enters the pupil
what are the lens?
transparent disc that can focus light to the retina
what is the retina?
contains rods (detects light intensity) and cones (detects colour)
Optic nerve:
sends impulses between the eye and brain
