·
Do you guys still remember the nervous system in I/GCSE Biology?
The Nervous System
- In I/GCSE Biology, reaction time = Time between hearing the gun and reacting to it
- Nervous system = brain, spinal cord and neurons (or nerve cells)
- Receptors = cells that detect stimuli or change in environment
- Receptors in the:
- Eyes – sensitive to light
- Ears – sensitive to sound + change in position (help keep out balance)
- Tongue – sensitive to chemicals (enables us to taste)
- Nose – sensitive to chemicals (enables us to smell)
- Skin – sensitive to touch, pressure, pain and temperature change
- Each receptor cell = nucleus + cytoplasm surrounded by cell membrane (animals and humans)
- Three types of neurons:
- Sensory neurons = carry impulses from receptor to spinal cord
- Relay neurons = carry impulses through spinal cord, up to the brain and from the brain back down the spinal cord
- Motor neurons = take impulses from spinal cord to an effector
- In I/GCSE Biology, effector:
- Muscle = made to contract
- Gland = secretes a chemical (e.g. hormone)
- Step 1 – Receptors cells detect stimuli or change in environment
- Step 2 – Information from receptor (e.g. something burning – nose) passes info along neurons to brain
- Step 4 – Information passes along the neurons as signals called impulses
- Step 5 – Brain coordinates a response – sends information to appropriate organ
- Neurons not joined together – small gap between them = synapse
- When impulse reaches end of neuron – chemical released
- Chemical travels across gap and starts an impulse in next neuron
- Message can only travel in one direction (1D lol)
Reflex actions
- In I/GCSE Biology, reflex actions means automatic + very quick response
- Needed to protect us from being hurt or damage a tissue
- Step 1 – Pain detected by receptor
- Step 2 – Sends impulse along sensory neurone to relay in spinal cord
- Step 3 – Relay neuron sends impulse via an arc to motor
- Step 4 – Motor neuron sends impulse to effector
- Step 5 – Muscle contracts or gland secrets
- Other types: e.g. coughing or blinking
That's all~
