Nervous System

• Sensory perception


  Involves making sense of the information from receptors (largely the function of the brain)
• Sensory elements are sensory reception and sensory perception
• Sensory receptors

  • Specialised cells that detect and respond to stimuli from the environment
  • They convert different forms of stimuli into nerve impulses that are sent to the brain
• Types of sensory receptors

  • Photoreceptors
  • Thermoreceptors
  • Chemoreceptors
  • Mechanoreceptors
  • Nociceptors
• Receptors


  Receive (detect) and respond to information from stimuli our environment
• Neurons


  Nerve cells in our body that enable us to pass messages quickly
• Passing a message along a neuron

  1. Change or stimuli detected by a receptor

  2. Electrical message passed along neuron to axon terminal/synapse

  3. Chemical neurotransmitters pass messages across gap to the next neuron
• The myelin sheath protects parts of the neuron and prevents the message from becoming lost
• Nerve

  The basic unit of the nervous system is a nerve cell, or neuron
• Neuron

  • Large cell body that connects to a long thin axon (nerve fibre)
  • Axon carries the nerve impulse away from the cell body
  • Axons can be up to 1 metre long
• Synaptic terminal

  Small bulb at the end of the axon where messages are passed to the next neuron
• Axons


  • Covered by a fatty layer called the myelin sheath
  • Myelin sheath helps to speed up a nerve impulse along an axon by controlling its path
• Multiple sclerosis

  Damaged myelin sheaths disrupt, block or allow escape of nerve impulses along the axon, causing movement and sensory problems
• Dendrites

  • Nerve endings that branch out of the cell body
  • Highly sensitive, thin branches that receive information and form contacts with axons of other neurons
• Information flow between neurons


  1. Dendrites bring information to the cell body

  2. Axons take information away from the cell body

  3. Information flows from one neuron to another across a synapse
• Synapse

  Small gap separating neurons where neurotransmitters drift out of the synaptic terminal of an axon and across the gap to the dendrite of the next neuron
• Specialised types of neuron

  • Sensory neurons (afferent neurons)
  • Motor neurons (efferent neurons)
  • Interneurons (connector neurons)
• Sensory neurons


  • Sensitive to various stimuli, collecting information from either the body's internal environment or the outside world
  • Send the information they have collected to the central nervous system for processing
• Motor neurons


  • Carry messages from the central nervous system to muscle cells throughout the body, which then carry out the response
• Interneurons

  • Link sensory and motor neurons, as well as other interneurons
  • Most common neuron in the body
  • Only make connections with other neurons
• Sensory receptors


  Specialised cells that detect and respond to stimuli from the environment
• Function of sensory receptors


  They convert different forms of stimuli into nerve impulses that are sent to the brain

  Receive (detect) and respond to information from stimuli our environment
• Role of sensory receptors

  • Photoreceptors
  • Thermoreceptors
  • Chemoreceptors
  • Mechanoreceptors
  • Nociceptors
• Function of sensory receptors

  Receive (detect) and respond to information from stimuli in our environment
• Sensory input


  Sensory receptors (e.g. eyes, nose) gather information from the environment and send it to the brain
• Integration

  The brain processes and understands the sensory input and decides what should be done in response
• Motor output


  Messages are sent from the brain to the muscles or glands to cause a response
• Central Nervous System (CNS)


  Made up of brain and spinal cord

  Receives information from the body, processes it and decides what to do
• Peripheral Nervous System (PNS)


  Nerves that branch off the brain and spinal cord
• Nervous system


  A communication network that controls what you do and what other body systems do
• Central Nervous System (CNS)


  Receives information from the body, processes it and decides what to do
• Peripheral Nervous System (PNS)


  • Receives information from the environment (using senses) and sends it to the CNS (brain)
  • Passes signals from the CNS and sends it to parts of the body such as muscles (effectors)
  • Nerves that branch off the brain and spinal cord
• Neurons

  Nerve cells that send electrical messages (called impulses) to your brain and from your brain
• Examples of neuron functions

  • Making our muscles contract when we run
  • Our heart rate increasing in a stressful situation
  • Our bodies shivering when we are cold
• Sensory neurons

  Go from your sensory organs to your brain (CNS), telling your brain about the outside environment
• Motor neurons

  Go from the brain (CNS) to your muscles, causing your muscles to contract
• Motor messages


  Brain to muscles
• Electrochemical messages


  Neurons transmit electrical signals along the length of the neuron and chemical signals (neurotransmitters) from one neuron to the next
• Synapse


  The gap between neurons where neurotransmitters pass from one neuron to the next
• Everything that you think about, what you remember, your personality, is all transmitted by the exact same path: dendrites -> cell body -> axon -> axon terminal -> across the synapse