Nervous

• Types of nervous systems

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


  Brain & spinal cord
• Peripheral Nervous System (PNS)


  Nerves (carry messages; connected to either spinal cord/ brain & brain stem)
• Types of nerve tissue cells

  • Neuroglia: nourishes/protect/insulate neurons
  • Neurons: transmit infos in form of electrical nerve impulses
• Parts of a neuron

  • Dendrite: has receptors that receive stimuli (pain, cold, pressure, heat) & transmit infos to bell body& often branch from the neuron cell body
  • Cell body: has organelles (nucleus); electrical nerve impulse pases through the cell body
  • Axon: carries infos away from the cell to axon terminal (end)
• Types of nerve impulses


  • Electrical: transmit signal WITHIN a neuron; then be transmitted across synapse(gap btwn neurons) to the next dendrite
  • Chemical: PROCESS signal from a neuron to another/ muscle cell
• Action potential


  Electricity pulse that travels along the axon when a nerve impulse reaches the end
• Chemical process of interaction between neurons and effector (target) cells


  1. Axon terminals produce and store chemical substances called neurotransmitters

  2. Neurotransmitters released by the presynaptic (before the synapse) membrane

  3. Neurotransmitters seep across the gap to receptors on the receiving neuron's postsynaptic (after the synapse) membrane

  4. Neurotransmitters bind to these receptors cause changes that can slow/speed up impulse & allow ions to pass in & out of the receiving cell
• Main parts of the brain

  • Cerebrum: largest & center of thought/intelligence
  • Cerebellum: body movements; smooths movements of voluntary muscles & body's balance
  • Brain stem: connects cerebrum to spinal cord
• Cerebrum


  • Divided into 2 hemispheres: right - control movement & activities, left - control right side
  • Cerebral cortex: outermost layer& consists of billions unmyelinated neurons (grey matter); highest function: reasoning, memory, consciousness, speech, voluntary muscle movement, vision, hearing, sensation
• Cerebellum


  • Injury causes muscle weakness, loss of coordination
• Brain stem


  • Midbrain & pons: relay messages btwn medulla & cerebrum
  • Medulla: below the pons; controls heart rate, breathing, blood cells, swallowing, coughing & vomiting
• Brain connects to the spinal cord at the lower end of the medulla
• Meninges: 3 layers of connective tissues covering brain & spinal cord


  • Dura meter: outer tough covering, lies next to skull partially protects brain from movement
  • Arachnoid: middle layer
  • Pia meter: inner layer, adheres to brain directly & contains blood vessels surrounding the brain
• Arachnoid space


  Space btwn middle & inner layers, filled w/ Cerebrospinal fluid
• Cerebrospinal fluid


  Circulates around brain and spinal cords, protects CNS and cushions shocks that could injure brain & spinal cord
• Parts of the Peripheral Nervous System (PNS)

  • 12 pairs of cranial nerves
  • 31 pairs of spinal nerves
• Cranial nerves


  Conduct impulses btwn brain, head, neck, chest, abdomen , impulses for smell, vision, hearing, pain, touch, temperature, pressure, voluntary & involuntary muscle control
• Vagus nerve


  Only cranial nerve that has extensive association with the entire body
• Spinal nerves


  Carry impulses form skin & hand/foot & internal body structures by cranial nerve
• Parts of the Autonomic Nervous System


  • Sympathetic: fight or flight responbse & often speed up functions
  • Parasympathetic: maintaining relax/normal (rest & digest)condition; more active when symp has been stimulated for too long