6 Coordination And Response Flashcards
Receptor
Receives / detects the stimulus
Coordinator
Determines the response
Effector
Carries out the response
Together the brain and spinal chord are known as the …
Central nervous system
Iris
Controls how much light enters the eye
Pupil
Space in the iris through which light passes
Cornea
Transparent front part of the eye that causes some bending of light
Conjunctiva
Thin transparent protective outer covering that helps prevent the entry of microorganisms
Retina
Layer of light sensitive cells that can sense different coloured light as well as cells that don’t sense colour at all
Lens
Refracts light to obtain a focused image
Optic nerve
A bundle of neurons that carries impulses from the retina to the brain
Eye focused on a distant object:
- ciliary muscles relax
- suspensory ligaments pulled tight
- lens pulled thin
Eyes focused on nearby object:
- ciliary muscles contract
- suspensory ligaments slackened
- lens allowed to bulge
Adaptions of the nerve cells: (3)
Long length - to carry impulses long distances Insulating sheath - to allow rapid transmission of impulses Branching ends (dendrites) - to receive or pass impulses from or to many other nerve cells
What happens when an impulse reaches a synapse: (6)
- The impulse reaches the synaptic bulb (the end of the neurone)
- vesicles containing the transmitter move towards the cell membrane at the synapse by diffusion
- vesicles release their neurotransmitter into the gap between the two cells
- neurotransmitter diffuses across the gap
- the neurotransmitter reaches the membrane of the next cell
- when enough neurotransmitter reaches the next cell an impulse will occur
Voluntary actions
Actions which we have conscious control over
Reflex actions
Unconscious actions which tend to be much faster as they use the reflex arc to do away with “thinking time”. Used as a means of protection.
Order of reflex arc
- pain receptor
- sensory neurone
- into spinal nerve
- impulses across relay neurone
- impulses across motor neurone
- message from motor neurone makes muscle contract
Low levels of glucose:
- Normal levels of glucose in blood
- Insulin not produced by the pancreas
- Less glucose absorbed by body cells
- Blood glucose remains the same
High levels of glucose
Too much glucose in blood
Pancreas produces insulin which enters the blood
Insulin allows glucose to be absorbed by body cells
Blood glucose reduced