OCR B1D- The Nervous System

Organ; Receptor; Dectection:

• Skin; Touch and Pain Receptors; Pressure
• Tongue; Salt/Sweet; Taste
• Eye; Retina (Rods and Cones); Light/Dark/Colours
• Ear; Hammer/Stirrup/Anvil, Bones vibrate; Sound
• Nose; Chemoreceptors; Smell 

The nervous system consists of the Brain, the Spinal Cord, and the Nerves. There are motor nerves (for movement) and sensory nerves (for senses). The CNS (Central Nervous System) is the Brain and the Spinal Cord. The nervous system enables you to control your body and it gives you feedback about the world.

The reflex arc is the order of how the body responds to a stimulus, like a bee sting. It is rapid and automatic, and is designed to avoid harm.

Stimulus ---> Receptor ---> Sensory Neurone ---> Relay Neurone (CNS) ---> Motor Neurone ---> Effector (Muscles) ---> Response

The Myelin Sheath is insulation to stop the impulses escaping.

Motor Neurone disease: The Myelin Sheath decays and gradually the myscles and organs stop working. There is no cure. 

All nerve impulses are electrical.

This is a synapse. The gap between the receptors and the transmitter is called the synaptic gap. A chemical is diffused across the synaptic gap, which passes the electrical impulse on. 

Long Sightedness:

• Hypermetrophia
• Can see distant objects clearly 
• Can't focus on near objects
• Lens focuses behind the retina
• Eyeball is too short
• Use a convex lens for glasses

Short Sightedness…