Reflex Response System

The nervous system consists mainly of the

1) Brain
2) Spinal Chord
3) Nerve Cells (Neurones)

Stimuli-

is a change such as temperature , light, sound, pressure, pain, movement, touch, chemicals etc

Neurones-

Nerve fibres are made up of lots nerve cells called neurones

Types of Neurones

Relay Neurone-

carry electrical impulses through the spinal cord and up to the brain and from the brain back down along the spinal cord.

Reflexes are fast, automatic protective biological control systems that link a stimulus to a response

Reflex reaction happen without you having to think about them- they are involuntary

What is a synapse?

Describe the Reflex in the finger?

-a stimulus triggers the receptors to send an electrical impulse along the sensory neurone to the relay neurone

-In the spinal cord which is part of the CNS

-Due to a synapse the chemical neurotransmitter diffuses from a high conc to a low conc between the sensor neurone and relay neurone

The eye

Cornea- provides protection for the eye, seals in the aqueous humour. first part that focuses light

Aqueous Humour- helps keep cornea in rounded shape

Iris- controls the amount of light that enters the eye

Retina- light sensitive inner lining of the eye. where images form

Optical Nerve- transmits image seen by retina to brain

Suspensory Ligaments-holds lens in position and changes the focus of the lens

Rods

-Black+White images produced
-Very sensitive to light (works well even at low light)
-Low acuity (resolving power)
-highest conc of rods around edge of retina
-we have more rods than cones

The control of light entering the eye

When the pupil gets smaller the circular muscles contract and the radial muscles relax

When light travels to the eye from a distant object, the rays are almost parallel and need to bent very slightly to be brought back into focus. So when viewing a distant object, the lens must be made thinner and less convex