coordination & response Flashcards
What is the role of nervous system?
What does it contain?
What does it split into?
1) coordination & regulation of body function
2) Contains neurones/nerve cells which go to all parts of body.
3) splits into CNS PNS.
define cns
brain & spinal cord
define pns
nerves outside of brain & spinal cord.
Describe the process/steps in a reflex arc
- Neurones in reflex arcs go to through the spinal cord or through an unconscious part of the brain.
- Stimulus -> detected by receptors -> impulses sent along a sensory neurone to the CNS.
- When impulses reach synpase between sensory neurone & relay neurone the impulses are sent along the relay neurone.
- When the impulses reach a synapse between relay neurone & motor neurone, the impulses are sent along the motor neurone.
- Impulses travel along the motor neurone to the effector e.g muscle, causing it to contract or move.
Define reflex action
automatically & rapidly integrating
and coordinating stimuli
with the responses of effectors (muscles and glands)
define synapse
what its purpose?
- junction between 2 neurones
- ensure impulses travel in one direction only.
Describe the events at a synapse
- An impulse stimulates release of neurotransmitter molecules from vesicles into the synaptic gap
- The neurotransmitter molecules diffuse across the synaptic gap
- Neutrotransmitter molecules bind w/ receptor proteins on the next neurone
- Impulse in then stimulated in the next neurone.
define sense organs
groups of receptor cells
responding to specific stimuli:
light, sound, touch,
temperature and chemicals
Function of cornea, iris, lens, retina, optic nerve
Cornea - refracts light
Iris - contains radial & circular muscles which control diameter of pupil therefore how much light enters pupil
Lens - focuses light onto the retina
Retina - contains light receptors, some sensitive to lights of diff colors
Optic nerve - carries impulses from the receptors on the retina, to the brain.
Iris reflex (pupil reflex)
Low light intensity
- Radial muscles in the iris contract, become shorter, & pull the pupils, making it wider.
- Circular muscles relax.
- Wider pupil = more light can enter eye, clear image is formed at retina.
Iris reflex (pupil reflex)
High light intensity
- Circular muscles in the iris contract, causing the pupil to get smaller.
- Radial muscles relax.
- Smaller pupil = less light can enter eye, protecting retina from damage.
Looking at nearby objects:
- Ciliary muscles contract, suspensory ligaments slackened.
- Lens become more fat
- This increases the amount by which it refracts light.
Looking at distant objects:
- Ciliary muscles relax, suspensory ligaments pulled tight.
- Lens pulled thin.
- This refracts light by a smaller amount.
2 types of receptors in retina, function of them, distribution
Rods
* Sensitive to dim lights
* Allows us to see in dim light, only in black & white.
* Distributed around the edge of retina except blind spot & fovea.
Cones
* Sensitive to light of diff colors/bright light (red, green, blue)
* Gives color vision.
* Most located in fovea; tightly packed together