nervous system

• The nervous system controls and coordinates our movement.

  • It allows us to interact with our surroundings by use of receptors and effectors (such as muscles)
  • It also controls many of the autonomic functions of the body - those over which we have no conscious control.
  • These include the movement of food along the gut in digestion, regulation of the breathing rate and regulation of heart rate.
• • The peripheral nervous system consists of the nerves of the body which connect to the CNS (brain and spinal cord)
  • The PNS carries nerve impulses from receptors that act as the body's sensors towards the CNS along sensory neurones. For example if we touch something hot the receptors in our skin detect that it is hot through touch and send a signal to the brain.
  • Nerves carry nerve impulses away from and towards the CNS.
• The central nervous system (CNS) consists of the brain and the spinal cord.

  • The brain is where sensory inputs (hearing, touch, vision etc) are processed and responses (such as movement) are initiated. The brain sends impulses via motor neurones to effector organs (usually muscles)

  e.g. moving your hand away from a hot plate.
• Dendrites 


  that make connections with other neurones, mostly within the CNS
• • The cell body containing the nucleus and other organelles.
  • The axon which carries the nerve impulse from the cell body
  • The myelin sheath consists of Schwann cells, wrapped around the axon like insulation on an electric cable.
  • There are small gaps between the Schwann cells called Nodes of Ranvier. These nodes and the myelin sheath increase the rate at which the nerve impulse is carried along the axon.
  • At the end, the axon branches to form axon endings or terminals that make connections usually with the muscle cells.These are called synaptic ends or synaptic knobs
• Information is passed along the axon of a neuron as an electrical impulse known as action potential
• Action potential needs to be transferred to another neuron by crossing over the synaptic gap between the presynaptic neuron and the post synaptic neuron
• Synaptic vesicles at the end of the neuron's axon terminal contain neurotransmitters
• When the action potential reaches the synaptic vesicles, they release neurotransmitters
• Neurotransmitters carry the signal across the synaptic gap by binding to receptor sites on the post synaptic cell
• This process completes the synaptic transmission
• • Information is passed down the axon of a neuron as an electrical impulse known as action potential.
  • Once the axon potential reaches the end of the axon it needs to be transferred to another neuron or tissue. It must cross over the synaptic gap between the presynaptic neuron and the post synaptic neuron
  • At the end of the neuron (in the axon terminal) are the synaptic vesicles, which contain chemical messengers called neurotransmitters.
• • When the electrical impulse (action potential) reaches these synaptic vesicles, they release their contents of neurotransmitters. Neurotransmitters then carry the signal across the synaptic gap.
  • They bind to the receptor sites on the post synaptic cell, thereby completing the process of synaptic transmission.
  • The most common neurotransmitter is acetylcholine
• • Pressure receptors changes in blood pressure
  • Temperature receptors are located in the skin and detect the external temperature and in the CNS where they detect core body temperature.
  • Sound receptors in the inner ear detect sound waves and allow us to hear
  • Light receptors are located in the retina of the eye and are involved in vision
  • Touch receptors are a type of pressure receptor located in the skin and allow us to experience a range of sensations, from gentle caress to a sharp slap, or to explore our surroundings using touch.
• • Pain receptors are located throughout the body. Their function is to signal to the CNS when njury has occurred. The ability to feel pain gives us an important survival advantage, particularly if it means we can avoid more serious injury.
  • However, there are no pain receptors in the brain, which is why some types of brain surgery can be performed using just a local anaesthetic
• • Taste receptors are of two types;
  • Receptors on the tongue (taste buds) can detect 5 main types of taste;
  • Sweet, sour, bitter, salt, umami (savoury taste we get from fried food, fish sauce or mushrooms)
  • Olfactory receptors in the nasal passages, detect smells or scents which enable us to taste
• • The autonomic nervous system is a component of the peripheral nervous system that regulates involuntary processes including heart rate, blood pressure respiration and digestion
  • The autonomic nervous system works without us being aware of it. It consists of the sympathetic and parasympathetic nervous systems
  • The nerves of these systems generally run with other nerve fibres in bundles, although there are a few nerves,

  that are

  completely autonomic (involuntary or unconscious)

  The actions of the parasympathetic and sympathetic nerves are often opposite to one another.
• sympathetic system

  it trigger in emergency situation. the hormone adrenaline is secreted from the adrenaline gland in the kidney's and its effect is to raise heart rate and breathing and causing sweating and a dry mouth. it is know as the fight, fright or flight response and in danger situation the body will do one of these 3 things
• parasympathetic system

  is linked to peace and contentment and is in control most of the time when we are relaxed. it slows heart rate and breathing and helps is to digest food.