UPDATED ch 16 nervous system

• CNS (central nervous system)


  brain and spinal cord
• PNS (peripheral nervous system)

  All nervous structures outside of CNS
• Neurons=

  Nerve cells
• Nerve cells:

  Possess electrical excitability
• Nerve=

  Bundles of many axons of neurons
• Sensory

  1st basic fxn of a neuron

  Afferent fxn

  Detects stimuli
• Integrative/Associative


  2nd basic fxn of a neuron

  Analyzing, decision making
• Motor


  3rd basic fxn of a neuron

  Efferent fxn
• Somat=


  "Body"
• Somatosensory=

  Info from skin, sk ms, joints, special spenses
• Somatomotor=


  To sk ms
• Auto=

  "Self"
• Nomic=

  "Law"
• Visceral (autonomic) sensory=

  Info from smooth organs in thorax, abdomen, and pelvis
• Visceral (autonomic) motor=

  CNS to smooth ms, cardiac & glands
• Sympathetic


  1st division of ANS

  "Fight or flight"
• Parasympathetic


  2nd division of ANS

  "Rest and digest"
• Enteric

  3rd division of ANS

  specialized for GI tract
• Soma

  •=nucleus+cytoplasm

  •Nissl bodies (RER)

  •Cytoskeleton

  •Lipofuscin=aging pigment
• Dendrites

  •extensions of PM on soma

  •increase S.A to receive signals
• Axon

  •Axon hillock-generates AP (action potential)

  •axoplasm

  •axolemma

  •axon collaterals=branches

  •telodendria

  •terminal button
• Presynaptic neuron

  •carries impulse to synapse

  •releases neurotransmitter (NT)
• Neurotransmitter

  •chemical released into synaptic cleft

  •presynaptic neuron can store 2-3 types of NT's
• Synaptic cleft

  •space b/n presynaptic neuron & postsynaptic membrane
• Post-synaptic neuron

  •receives signal/NT
• Effector cell=

  Ms or gland
• Neuromuscular jxn***

  Presynaptic membrane+synaptic cleft+motor end plate (MEP)
• Note that NT=

  Acetylcholine (ACh)
• Action potential used to release NT

  1) AP reaches axon terminal

  2) Calcium (Ca2+) channels open

  3) Ca2+ binds to a protein that helps release NT

  4) NT transverse synaptic cleft to receptor on postsynaptic membrane

  5) Change occurs at postsynaptic membrane
• Axodendritic


  Type of synapse b/w neurons

  Axon to dendrite
• Axosomatic


  Type of synapse b/w neurons

  Axon to cell body (soma)
• Axoaxonic


  Type of synapse b/w neurons

  Axon to axon
• Electrical synapse


  1st type of synapse

  •gap jxn's b/w membranes

  •signal flows thru connexons

  •not as common

  •rapid, uniform coordinated mvmts
• Chemical synapse

  2nd type of synapse

  •releases NT

  •AP (action potential) arrives at synaptic bulb

  •voltage-gated CA2+ channels open>influx CA2+

  •exocytosis of NT

  •ion channels on postsynaptic membranes open/close

  •typical neuron gets 1k-10k synapses

  •sum of all excitatory/inhibitory input determines is AP occurs
• 3 methods of neurotransmitter removal

  1. NT diffuses away

  2. NT broken down (AChEsterase breaks down Ach into acetic acid & choline)

  3. NT transmitted back into presynaptic membrane (reuptake)
• Adrenaline

  A type of neurotransmitter

  Fight or flight, made is stressful situations
• Noradrenaline

  A type of neurotransmitter

  Concentration, affects attention & responding actions in brain
• Acetylcholine


  A type of neurotransmitter

  Learning, involved in thought, learning & memory
• Structural classifications of neurons

  multipolar, bipolar, unipolar
• Multipolar neuron


  most common, many dendrites and one axon, all motor (efferent)