Nerves and the eye Flashcards
Biological name for nerve cells
Neurones
Name the two human biological systems that help us carry out a coordinated response
Nervous and endocrine system
What 3 things does a coordinated response require?
Stimulus, receptor, effector
What is a stimulus?
the change in the animals surroundings
What is a receptor?
The organ which detects the change
What are the effectors when catching a ball?
Muscles - they contract as you catch the ball
What system makes the link between the stimulus and the response?
The nervous system
What do receptors detect and how do they respond?
detect the stimulus and change its energy into nervous impulses
What does the central nervous system (CNS) consist of?
Brain and spinal cord
What does the CNS do?
Coordinates all of the nervous responses such as moving or reflexes
What does the peripheral nervous system (PNS) consist of?
All of the other nerves
What do the components of the PNS do?
Send impulses to all the effectors
Name the 3 types of neurones
Sensory, relay and motor
What type of neurone do impulses from receptors pass along?
Sensory neurones (until they reach the CNS)
In the CNS, what type of neurone do impulses pass to?
Relay
When an impulse is passed to effectors (muscles or glands), along what type of neurone do they travel?
Motor
What does the nucleus of a motor neurone contain?
All the genetic information of the cell
What are dendrites?
Tree-like projections which connect to different neurones
What is the cell body of a motor neurone?
Main section of the cell, contains the nucleus
What is the axon in a motor neurone?
The long section in which the signal is sent
What is the myelin sheath in a motor neurone?
sections along the neurone which wrap around the axon
What are reflexes?
Automated actions which do not involve the brain
What is a reflex arc?
The movement of the impulse from receptor to effector
What is the gap between neurones called?
A synapse
How do we “see” things?
- eye detects light + sends impulse to brain
- brain converts information into an image
What is the cornea and what is its job?
Curved transparent disc at front of the eye, does most of the focusing
What is the pupil?
A circular opening whose size is controlled by the iris
What is the iris and what is its job?
Ring of muscles with a hole in the middle, controls how much light enters the eye.
What is the job of the lens?
Its shape can be changed acutely to finely tune the focusing of light onto the retina
What is the ciliary muscle?
Ring of muscle at the edge of the eye which circles the lens
When the ciliary muscle contracts, lens gets …………
fatter
When the ciliary muscle relaxes, lens gets …………
thinner
What is the suspensory ligament?
Strong fibres which attach the lens to the ciliary muscle
What does the retina contain?
Light sensitive cells called rods and cones
What does the optic nerve consist of?
Many neurones which carry impulses from retina to brain
What is the fovea?
The region of the retina with the greatest number of cones
What is the conjunctiva?
A mucous membrane that covers the eye to prevent infection
When in dim light, the radial muscles ……………
relax
When in bright light, the radial muscles ……………
contract
