nervous system

• Functions of the Nervous System

  • Maintaining homeostasis
  • Receiving sensory input
  • Integrating information
  • Controlling muscles and glands
  • Mental activity such as emotions, consciousness, thinking & memory
• Anatomical divisions of the Nervous System

  • Central Nervous System (CNS)
  • Peripheral Nervous System (PNS)

  
• Physiological divisions of the Nervous System


  • Autonomic Nervous System
  • Somatic Nervous System

  
• Nervous tissues


  • Neurons
  • Neuroglial cells
  • Brain, spinal cord, ganglia

  
• Astrocyte


  Support for neurons and blood vessels. BBB

  
• Ependymal


  Line cerebral ventricles and produce CSF
• Oligodendrocyte


  Provide myelin sheath to nerves in CNS
• Schwann cell


  Provide myelin sheath to nerves in PNS
• Satellite cells

  Support for neuron cell body
• Types of Neurons (Structural)


  • Multipolar – in CNS and motor neurons
  • Bipolar – some specialized sensory organs
  • Unipolar – most sensory neurons

  
• Types of Neurons (Functional)

  • Sensory neurons
  • Motor neurons
  • Interneurons (99%)

  
• Senses


  • General Senses
  • Somatic (Touch, Pressure, Proprioception, Temperature, Pain)
  • Visceral (Pressure, Pain)
  • Special Senses (Taste, Smell, Sight, Hearing, Balance)
• Types of Sensory Receptors


  • Mechanoreceptors-sensitive to mechanical stimuli (touch, pressure, proprioception, hearing, balance)
  • Chemoreceptors -sensitive to chemicals (smell and taste)
  • Photoreceptors -sensitive to light (sight)
  • Thermoreceptors-sensitive to changes in temperature
  • Nociceptors-sensitive to extreme mechanical, chemical and thermal stimuli (pain)
• Depolarization


  Local reversal of the polarity of across the plasma membrane
• Repolarization


  Restoration of the resting membrane potential (RMP)
• Myelin sheath


  Important for electrical insulation and salutatory conduction
• Saltatory conduction


  Action potential is caused by local depolarisation of plasma membrane, triggering depolarisation down the axon. Myelin acts to insulate parts of the axon, so that the local changes in electrical current caused by the action potential "leaps" from node to node.
• Synapse


  Junction between a neuron and the cell it innervates. May be electrical or chemical.
• Neurotransmitters


  Chemicals released from presynaptic neuron that affect the postsynaptic neuron. Can be stimulatory or inhibitory on postsynaptic neuron (action depends on receptors on postsynaptic membrane). Modulate the signal i.e. can amplify, prolong or inhibit. Examples; Acetylcholine, serotonin, dopamine, norepinephrine, GABA
• Divisions of the Nervous System

  • Enteric division

  
• Reflex


  Automatic (subconscious), unlearned, fast, usually homeostatic, vary in complexity
• Reaction


  Voluntary, can learn/improve, slower
• Examples of Reflexes


  • Patellar reflex
  • Pupillary reflex
  • Babinski reflex
  • Moro reflex
  • Baroreceptor reflex
• Simple reflex


  Simplest is a monosynaptic reflex pathway
• label the brain and functions

  1. frontal lobe- personality, behaviour, emotions, problem solving, speech, body movement
• temporal lobe - hearing, memory, emotion, language
• parietal lobe - touch, pain, temperature, pressure, taste, smell, language comprehension
• occipital lobe - vision
• cerebellum - balance, coordination, posture, muscle tone, learning motor skills
• cerebellum - balance, coordination, posture, fine motor control
• brain stem - controls basic life processes such as breathing, heart rate, blood pressure, digestion, sleep/wake cycle
• spinal cord - transmits sensory information from skin to brain and sends messages back down to muscles