• Created by: amm242
  • Created on: 09-05-18 11:16

Nervous System

1. Collects, processes and responds to information in the environment

2. Co-ordinates the working of organs and cells in the body

Central nervous system 

  • brain - centre of all concious awareness
  • spinal cord - reflex actions

Peripheral nervous system

  • transmits messages via neurons
  • autonomic nervous system - governs vital body functions eg. breathing, heart rate, stress responses
  • somatic nervous system - controls muscle movement and recieves info from sensory receptors
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Endocrine System

Works alongside nervous system to control body functions using hormones.

Glands - Produce hormones - major gland is pituitary gland controls release of all hormones

Hormones - Secreted into bloodstream and affect any cell with receptor

Flight or fight response - Works with sympathetic branch.  Stress hormone adrenaline is released from adrenal medulla which triggers physiological changes eg. increased heart rate.  Parasympathetic branch slows it down again.

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Sensory neuron - carry messages from PNS to CNS.  Have long dendrites & short axons.

Relay neuron - connect sensory neurons to motor or other relay neurons.  Have short dendrites, short axons and no myelin sheath

Motor neuron - connect CNS to effectors such as muscles and glands.  Have short dendrites & long axons

Cell body - contains genetic material

Dendrites - carry nerve impulses from other neurons to cell body

Axon - carries electrical impulses down length of neuron

Myelin sheath - protects axon

Nodes of ranvier - speed up transmission of impulse

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Synaptic transmission

Synapse - tiny gap separating one neuron from the next

1. Nerve impulse travels down axon

2. Reaches synaptic terminal

3. Triggers release of neurotransmitters 

4. Fired into synaptic gap

5. Binds with receptors on dendrites of adjacent neuron

6. Taken up by post-synaptic neuron

7. Chemical message is converted back to electrical impulse

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Excitation & Inhibition

Negatively charged neuron is less likely to fire

Postively charged neuron is more likely to fire (action potential)


  • Adrenaline - excitatory, increases +ve charge of postsynaptic neuron
  • Serotonin - inhibitory, increases -ve charge of postsynaptic neuron
  • Dopamine - equally excitatory and inhibitory
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