B3 Flashcards
What components make up the structure of a nervous system?
🟡CNS(brain + spinal chord)
🟡sensory, motor, relay neurones
🟡receptors and effectors
🟡synapses
What is a neuron?
A nerve cell, carrying impulses from one component to another
Describe a sensory neurone:
Carries electrical impulses from receptor cells to the CNS
🟣cell body in the middle of the cell
🟣ends surrounded with dendrites (to connect neurones)
🟣axon surrounded by mycelin
Describe a motor neurone
Carry’s an electrical impulse from the CNS to an dendrites
🟣cell body near dendrites
🟣ends have dendrites
🟣axon surrounded with mycelin
What do relay neurones do?
Carry an impulse from a sensory neurone to a motor neurone
What is a synapse and how does it work?
The gap impulse two nerve cells(neurones)
🟡electrical current turned into chemical current
🟡chemical (neurotransmitter) diffuses across the gap
🟡turned back into an electrical impulse
What are receptors?
Cells that detect a stimuli, creating an electrical impulse
What are effectors?
Muscles / glands that carry out the response
Describe how the nervous system produces a co ordinated response
🔴Can go to many parts of the body at once (many different motor neurones at once
🔴many different sensory receptors are able to bring in the impulse at once
Describe a reflex arc
Stimulus
Receptor
Sensory neuron
Spinal cord (relay neuron)
Motor neuron
Effector
How is the reflex arc adapted to serve its function?
Instead of going through the whole CNS(brain + spinal chord), it only goes to spinal chord
🟣making it fast and automatic
* to protect the body from danger
Can signals move along a neurone in any direction ?
No, an electrical impulse can travel in one direction only
Describe the cornea
🟣transparent outer layer
🟣refracts light onto the retina
Describe the iris
🟣coloured ring muscle
🟣controls how much light enter the eye
Describe the pupil
Central hole allowing light to come into the eye
Describe the lens
🟣transparent biconvex disk
🟣focuses light onto the retina
Describe the retina
Tissue at the back of the eye, containing photoreceptors (convert tissues to electrical signals)
Optic nerve
Carries impulses between the eye and the brain
Ciliary body
What happens when it contracts?
🟡Muscular tissue that Alters the shape of the lens
*If it contracts it gets closer to the lens, making it fatter(short sight), this means the suspensory ligaments slack
Suspenseful ligaments
🔵Ligament tissue connecting ciliary muscle to eye
* does the opposite to ciliary muscle
Describe short sightedness and how to overcome
🔵eyeball is too long
🔵image focused in front of the retina
🟢concave lens in glasses
Describe long sightedness and how to overcome
🔵the eyeball is too short
🔵image focussed behind the retina
🟢convex lens in glasses
What happens to lens to focus on nearby and far objects?
🟣nearby, lens gets fatter , ciliary muscle contracts
🟣far away, let’s goes thinner , ciliary muscle relaxes
Describe colourblindness and how to overcome
🟣inability to tell the difference between different colours die to lack/defects in receptors in retina
🟣tinted lenses
