Chapter 48 ~ Nervous System

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Chapter 48 Nervous System
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The Nervous System
http//outreach.mcb.harvard.edu/animations/synapti
c.swf

• Neurons
• Glial cells
• Soma
• Axon
• Dendrite
• Synapse
• Neurotransmitters
• Action potential

• Motor neurons
• Interneurons
• Sensory neurons
• Myelin sheath
• Schwann cells
• Reflex arc

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Nervous systems

• Effector cells muscle or gland cells
• Nerves bundles of neurons wrapped in connective
  tissue
• Central nervous system (CNS) brain and spinal
  cord
• Peripheral nervous system (PNS) sensory and
  motor neurons

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Structural Unit of Nervous System

• Neuron structural and functional unit
• Cell body nucelus and organelles
• Dendrites impulses from tips to neuron
• Axons impulses toward tips
• Myelin sheath supporting, insulating layer
• Schwann cellsPNS support cells
• Synaptic terminals neurotransmitter releaser
• Synapse neuron junction

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Simple Nerve Circuit
http//msjensen.cehd.umn.edu/1135/Links/Animations
/Flash/0016-swf_reflex_arc.swf

• Sensory neuron convey information to spinal cord
• Interneurons information integration
• Motor neurons convey signals to effector cell
  (muscle or gland)
• Reflex simple response sensory to motor
  neurons
• Ganglion (ganglia) cluster of nerve cell bodies
  in the PNS
• Supporting cells/glia nonconductiong cell that
  provides support, insulation, and protection

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Neural signaling
http//bcs.whfreeman.com/thelifewire/content/chp44
/4403s.swf
http//outreach.mcb.harvard.edu/animations/actionp
otential.swf

• Membrane potential (voltage differences across
  the plasma membrane)
• Intracellular/extracellular ionic concentration
  difference
• K diffuses out (Na in) large anions cannot
  follow.selective permeability of the plasma
  membrane
• Net negative charge of about -70mV

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Neural signaling
http//bcs.whfreeman.com/thelifewire/content/chp44
/4402s.swf
http//www.mind.ilstu.edu/curriculum/neurons_intro
/flash_electrical.php?modGUI232compGUI1827item
GUI3158

• Excitable cells cells that can change membrane
  potentials (neurons, muscle)
• Resting potential the unexcited state of
  excitable cells
• Gated ion channels (open/close response to
  stimuli) photoreceptors vibrations in air
  (sound receptors) chemical (neurotransmitters)
  voltage (membrane potential changes)

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Neural signaling

• Graded Potentials (depend on strength of
  stimulus)
• 1- Hyperpolarization (outflow of K) increase in
  electrical gradient cell becomes more negative
• 2- Depolarization (inflow of Na) reduction in
  electrical gradient cell becomes less negative

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Neural signaling

• Threshold potential if stimulus reaches a
  certain voltage (-50 to -55 mV).
• The action potential is triggered.
• Voltage-gated ion channels (Na K)
• 1-Resting state both channels closed
• 2-Threshold a stimulus opens some Na channels
• 3-Depolarization action potential generated
  Na channels open cell becomes positive (K
  channels closed)
• 4-Repolarization Na channels close, K
  channels open K leaves cell becomes
  negative
• 5-Undershoot both gates close, but K channel
  is slow resting state restored
• Refractory period insensitive to depolarization
  due to closing of Na gates

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Neural signaling

• Travel of the action potential is
  self-propagating
• Regeneration of new action potentials only
  after refractory period
• Forward direction only
• Action potential speed
• 1-Axon diameter (larger faster 100m/sec)
• 2-Nodes of Ranvier (concentration of ion
  channels) saltatory conduction 150m/sec

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Synaptic communication

• Presynaptic cell transmitting cell
• Postsynaptic cell receiving cell
• Synaptic cleft separation gap
• Synaptic vesicles neurotransmitter releasers
• Ca influx caused by action potential vesicles
  fuse with presynaptic membrane and release.
• Neurotransmitter

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Signal transmission
http//www.bayareapainmedical.com/neurtrns.html
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Neurotransmitters
http//www.blackwellpublishing.com/matthews/neurot
rans.html

• Acetylcholine (most common) skeletal muscle
• Biogenic amines (derived from amino
  acids) norepinephrine dopamine
  serotonin
• Amino acids
• Neuropeptides (short chains of amino
  acids) endorphin

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Nervous System

• Central Nervous System
• Crainial Nerves
• Spinal Nerves
• Peripheral Nervous System
• Sensory (afferent) Division
• Sensing external environment
• Sensing internal environment
• Motor (Efferent) Division
• Autonomic Nervous System
• Sympathetic Nervous System
• increase energy consumption
• Parasympathetic Nervous System
• conservation of energy
• Somatic Nervous System
• voluntary, conscious control, muscles

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Vertebrate PNS
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The Brain

• Meninges
• Cerebrospinal fluid
• Ventricles
• Brain Stem
• Medulla oblongata
• Pons
• midbrain

• Diencephalon
• Thalamus
• Hypothalamus
• Cerebellum

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The Vertebrate Brain

• Forebrain
• cerebrummemory, learning, emotion
• cerebral cortexsensory and motor nerve cell
  bodies
• corpus callosumconnects left (analytical) and
  right (creative) hemispheres
• thalamus (main input/output from cerebrum)
  hypothalamus (hormone production)
• Midbrain
• inferior (auditory) and superior (visual)
  colliculi
• Hindbrain cerebellumcoordination of
  movement medulla
  oblongata/ ponsautonomic, homeostatic functions
  

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Pituitary Gland
Corpus Callosum
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Cerebrum

• Cerebral hemispheres
• Cerebral cortexgray matter
• Convolutions
• Cerebral lobes
• Frontal lobeconscious thought and muscle
  control.

• Parietal Lobesreceive information from skin
  receptors.
• Occipital Lobereceives visual input.
• Temporal Lobehas areas for hearing and smelling.

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