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Co-ordination & Response (Brief Notes) (Parts of the eye (Pupil - Hole…
Co-ordination & Response (Brief Notes)
Innvolves
STIMULUS
- the change in the environment
RECEPTOR CELLS
- adapted to detect stimuli & are found in sens organs
EFFECTORS
- It's a Muscle or Gland
When impulse arrives at muscle it contracts
When impulse arrives at gland Hormones secreted (e.g. Adrenaline, Osetrogen etc)
Impulses
Electrical impulses carry info from receptors along nerve cells (neurones) to CNS
2 Parts of CNS
Brain
Spinal cord
Nerve cells
Connect sense organs to CNS
CNS connects to effector
Brain & Spinal cord made up of neurones, adapted by having many ending sto connect with other neurones so electrical impulses can be sent to long cell extensions (axons & detrons)
Sensory Neurones
- Links sense organs to CNS
Relay Neurones
- Within CNS, very short( also called intermediate or connecting neurones)
Motor Neurones
- Connects CNS to an effector (muscle or galand)
Synapses
Tiny gap between 2 neurone ends
Electrical impulse doesn't cross gap
It cause chemicals called neurotransmitters to be released from end of 1 neurone across synapse by diffusion
When neurotransmitter reaches next neurone it causes a new electrical impulse
Travels in 1 direction
Synapses alows 1 neurone to pass/recieve impulses to/from several others at the same time
Reflexes
Definition - A rapid automatic response to a stimulus
Action often protects the body
Nerve pathway of a reflex is the reflex arc the structures involved are
STIMULUS
RECEPTOR
SENSORY NEURONE
RELAY NEURON
(in spinal cord)
MOTOR NEURONE
EFFECTOR
RESPONSE
Parts of the eye
Pupil
- Hole in the centre of iris, allows light into the eys
Iris
- Controls amount of light that is let into the eye
Suspensory Ligament
- Attaches lens to ciliary muscle
Ciliary Muscle
- Circular muscle around lens ehich helps to change it's shape
Sclera
- Protective white oter layer
Choroid layer
- contains dark pigment to absorb light
Retina
- Contains light sensitive receptor cells
Fovea
- Most sensitive part of the retina
Optic Nerve
- Carries electrical impulses to the brain
Blind Spot
- Where optic nerve attaches to retina there are no light sensitive cells
Cornea
- Refracts light