Y10 EoY

Reflexes:

• Cells of multicellular organisms need to communicate with each other

The Nervous System:

• Central Nervous System (CNS) = brain and spinal cord. Connected to the body by sensory neurones and motor neurones. 
• Sensory Neurones = the neurones that carry information as electrical impulses from receptors to the CNS
• Motor Neurones = the neurones that carry electrical impulses from the CNS to effectors. 
• Effectors = all muscles and glands that respond to nervous impulses
• The CNS is the co-ordination centre. It recieves information from the receptors and then co-ordinates a response. The response is carried out by effectors.

Synapses and Reflexes:

• Neurones quickly transmit information to and from the brain, and the brain quickly decides what to do. Reflexes are much quicker and don't involve the brain. 
• The connection between two neurones is called a synapse. 
• The nerve signal is transferred by chemicals which diffuse (move) across the gap. 
• These chemicals then set off a new electrical signal in the next neurone. 
• Reflexes are rapid, automatic responses to certain stimuli that don't involve the conscious part of the brain. They can reduce the chances of getting injured. 
• The hormone adrenaline is the body's response to shock. 
• The passage of information in a reflex (from receptor to effector) is called a reflex arc. 
• The reflex arc goes along the central nervous system. They go through the spinal cord or an unconscious part of the brain. 
• When a stimulus is detected by receptors, impulses are sent along a sensory neurone to a relay neurone in the CNS. 
• When the impulses reach a synapse between the sensory neurone and the relay neurone, they trigger chemicals to be released. These chemicals cause impulses to be sent along the relay neurone. 
• When the impulses reach a synapse between the relay neurone and a motor neurone, the same thing happens. Chemicals are released and cause impulses to be sent along the motor neurone. 
• The impulses then travel along the motor neurone to the effector (which is usually a muscle, like in this example). 
• The muscle then contracts and moves your hand away from the bee. 
• Because you don't have to think about the response, reflex responses are faster than normal responses. 

The Eye:

Parts of the eye:

• The sclera is the tough, supporting wall of the eye 
• The cornea is the transparent outer layer found at the front of the eye. It bends light into the eye. 
• The iris contains muscles that allow it to control the diameter of the pupil and therefore how much light enters the eye. 
• The lens focuses the light onto the retina (which contains receptor cells sensitive to light intensity and colour)
• The shape of the lens is controlled by the ciliary muscles and suspensory ligaments
• The optic nerve carries impulses from the receptors on the retina to the brain. \

The iris reflex:

• Bright light can damage the retina, so the iris is the reflex that protects it. 
• When light receptors in the eye detect bright light, a reflex is…