the nervous system & neurons

• what is the nervous system?

  • network of cells in body & our main internal communication system
• what are the 2 sub divisions of nervous system?

  1. central nervous system
  2. peripheral nervous system
• what does cns consist of?

  1. brain
  2. spinal cord
• function of cns?

  • controls behaviour & regulates bodys physiological processes
  • eg breathing, digestion, heartbeat
• function of brain?

  • provides conscious awareness
  • deals with higher order skills
  • eg problem solving
  • brain stem connnects brain & spinal cord
  • controls involuntary processes
• function of spinal cord?

  • relays information from brain to body
  • transfers messages to pns
  • carries out reflex actions without brain
• function of pns?

  • transmits millions of neurons to & from cns
• what are the 2 sub divisions of pns?

  1. autonomic
  2. somatic
• what are the 2 sub divisions of autonomic?

  1. sympathetic
  2. parasympathetic
• function of autonomic nervous system?

  • transmits & receives messages from organs
  • automatic
• function of sympathetic nervous system?

  • fight or flight - bodily arousal
  • increases heart rate, blood pressure
• function of parasympathetic nervous system?

  • returns body to normal resting rate - bodily calm
• function of somatic nervous system?

  • transmits & receives messages from senses & controls muscle movement
  • conscious control
  • consists of sensory receptors & motor pathways
• what are neurons?

  • nerve cells that allow nervous system to communicate by sending information using chemical & electrical signals
• main structures in neuron?

  1. cell body
  2. nucleus
  3. dendrites
  4. axon
  5. myelin sheath
  6. nodes of ranvier
  7. axon terminal buttons
• what does the cell body include?

  • nucleus - contains genetic material of cell
• dendrites?

  • branch like structures
  • carry nerve impulses from neurons toward cell body
• axon?

  • carries impulses away from cell body
• myelin sheath?

  • covers & protects axon
  • speeds up electrical transmission
• nodes of ranvier?

  • myelin sheath broken up into chunks so there are gaps between it
  • GAPS ARE NOR
  • makes electrical transmission even faster - forces impulse to jump across gaps along axon
• axon terminal buttons?

  • at end of axon
  • communicate with next neuron in chain across gap called synapse
• function of sensory neuron?

  • sends signals from sense organs to brain
  • sends messges from pns to cns
• structure of sensory neuron?

  • short axons
  • long dendrites
• function of relay neuron?

  • connects sensory neuron to motor neuron
• structure of relay neurons?

  • short axon
  • short dendrites
  • no myelin sheath
• function of motor neuron?

  • connects cns/brain to effectors such as muscles/glands
• structure of motor neurons?

  • long axons
  • short dendrites
• link neurons to nervous sytem?

  • sensory receptors detects stimulus (change in environment)
  • electrical impulse carried along sensory neuron
  • reaches cns
  • brain coordinates huge amount of information
  • produces a response & sends it along motor neuron to effector organs
  • effector organs will produce a response
• what is synaptic transmission?

  • refers to how neurotransmitters transmit info across synaptic cleft from one neuron to another
• syanaptic transmission process?

  1. action potential (electrical impulse) triggers vesicles containing nt in pre synaptic neuron to post synaptic neuron
  2. vesicles fuse with membrane & releases nt into synaptic cleft
  3. nt diffuse across synaptic cleft & bind to receptor sites on post synaptic cell membrane
  4. once enough receptors have nt bound to them signal is transmitted
  5. stimulation of receptors by nt result in either excitation/inhibition of post synaptic neuron
  6. summation occurs - net effect of excitatory/inhibitory potentials
  7. whichever nt is most attached leads to that effect
• explain excitation?

  • leads to positive charge so message is more likely to fire
• explain inhibitory?

  • leads to negative charge in post synaptic neuron so message is less likely to fire