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B2 Revision:Nervous System (Key words: (Sensory receptors (Groups of cells…
B2 Revision:Nervous System
Key words:
Stimuli
Change in environment
Neurones
Nerve cells
Transmits information information as electrical impulses to and from the CNS
Nervous system
What allows you to react to your surroundings
Made up of nerurones
Sensory receptors
Groups of cells that detect stimuli and initiate responses for them
Receptors in eye detect light
Receptors in skin detect pressure(touch), temperature change, tissue damage(causes you to feel pain)
Effectors:
Muscles or glands which respond to nervous impulses and bring about a response to stimuli
Muscles Contract
Glands secrete chemical substances called hormones
Central Nervous System (CNS)
Where all information from sensory receptors are sent
Where reflexes and actions are coordinated
In vertebrates:
Consists of brain and spinal cord(long column of neurones that run from base of brain, down spine) only, sending information between the brain and the rest of the body
In mammals
Connected by sensory nerurones and motor neurones
Neurones
Motor
Carries electrical impulses from the CNS to effectors
Many short dendrites from CNS to cell body.
1 long axon from cell body to effector cells
Myelin sheath on axons
Relay
Carries electrical impulses from sensory neurons to motor neurons
Found in the CNS
Short dendrites from sensory neurons to cell body
1 axon from cell body to motor neurons
Sensory
Carries electrical information from sensory receptors to CNS
1 long dendron carrying impulses from receptor cells to cell body
1 short axon from cell body to CNS
Structure:
Cell body
Has extensions connecting to other neurones
Dendrons carry nerve impulses towards the cell body
Axons carry nerve impulses away the cell body
Some axons are surrounded by a
myelin sheath
which is a fatty layer which acts as an electrical insulator, speeding up the electrical impulses.
Synapses:
The connection between two neurons
Neurotransmitters(chemical) transfers signal between neurons which diffuse across the gap, which then set off a new electrical signal in the next neuron
Slows down transmission of nerve impulse as diffusion between the gap takes time
Reflexes:
Fast, automatic responses to certain stimuli as it doesn't pass through the conscious brain when a quick response is needed
Reduces chance of being injured
Reflex arc
is the passage in a reflex which goes through the spinal cord or an unconscious part of the brain
Stimuli, sensory neurone, relay neurone, motor neurone, effector which will cause a quick response