14: Coordination and response Flashcards
Where do electrical impulses travel?
Along neurones
What does the central nervous system (CNS) consist of?
The brain and the spinal cord
What does the peripheral nervous system (PNS) consist of?
The nerves OUTSIDE the brain & spinal cord
Describe the role of the nervous system
Coordination and regulation of body functions
Identify sensory, relay & motor neurones
- Sensory neurones are long and have a cell body branching off the middle of the axon
- Relay neurones are short and have a small cell body at one end with many dendrites branching off it
- Motor neurones are long and have a large cell body at one end with long dendrites branching off it
Describe a simple reflex arc
stimulus –> receptor –> sensory neurone –> relay neurone –> motor neurone –> effector –> response
Describe a reflex action
A means of automatically and rapidly integrating and coordinating stimuli with the responses of effectors (muscles and glands)
What is a synapse?
A junction between two neurones
Describe the structure of the synapse
- the presence of vesicles containing neurotransmitter molecules
- the synaptic gap
- receptor proteins
Describe events at a synapse
- the impulse stimulates the release of neurotransmitter molecules from vesicles into the synaptic gap
- the neurotransmitter molecules diffuse across the gap
- neurotransmitter molecules bind with receptor proteins on the next neurone
- an impulse is then stimulated in the next neurone
Which direction do synapses travel in?
They only travel is ONE direction
Describe sense organs
Groups of receptor cells responding to specific stimuli: light, sound, touch, temperature & chemicals
Function of the cornea
Refracts light
Function of the iris
Controls how much light enters the pupil
Function of lens
Focuses light on to the retina
Function of retina
Contains light receptors, some sensitive to light of different colours
Function of optic nerve
Carries impulses to the brain
What is the pupil reflex?
- dim light the pupil dilates (widens) in order to allow as much light into the eye as possible
- bright light the pupil constricts (narrows) in order to prevent too much light entering the eye and damaging the retina
What is the pupil reflex in terms of antagonistic action?
DARK –> radial contract, circular relax, wide pupils, more light enters
BRIGHT –> radial relax, circular contract, narrow pupils, less light enters
Explain accomodation to view near objects
The ciliary muscles contract (the ring of muscle decreases in diameter)
This causes the suspensory ligaments to loosen
This stops the suspensory ligaments from pulling on the lens, which allows the lens to become fatter
Light is refracted more
Explain accomodation to view distant objects
The ciliary muscles relax (the ring of muscle increases in diameter)
This causes the suspensory ligaments to tighten
The suspensory ligaments pull on the lens, causing it to become thinner
Light is refracted less
Describe distribution of rods and cones in the retina of a human
Rods = all over the cells (other than the area where the optic nerve attaches to the retina)
Cones = in the blind spot
Function of rods
Greater sensitivity of rods for NIGHT VISION
Function of cones
3 diff types of cones
- absorbs ligth of different colours for colour vision
