Download Organization of the Nervous System and the Neuron

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HUMAN BRAIN= 100 BILLION
NEURONS
SPINAL CORD = 13.5 MILLION
NEURONS
HUMAN BRAIN = 1 TO 10
TERABYTES OF INFORMATION
STORED
1 TERABYTE= 1024 GIGABYTES
1 GIGABYTE = 1024 MEGABYTES
SO…….
1 TERABYTE = 1,048,576 MEGABYTES
Organization of
the
Nervous System
and the
Neuron
Organization of the
Nervous System
The Nervous System “maintains
body homeostasis with electrical
signals; provides
for sensation, higher mental
functioning, and emotional
response; and activates muscles
and glands.”
3 Overlapping Functions of Nervous
System
SENSORY INPUT-
INTEGRATION-
MOTOR INPUT-
Works with the Endocrine System to
maintain homeostasis.
1.Nervous System2.Endocrine System-
Organization of the nervous system
can be
based on:
1. Structural ClassificationA. CNSB. PNS2.Functional ClassificationA. AfferentB. Efferent-
STRUCTURAL CLASSIFICATION
FUNCTIONAL
CLASSIFICATION
Nervous Tissue
Nervous tissue is made up of two types of
cellsSupporting and Neurons
Supporting cells of the CNS are called
Neuroglia or “nerve glue”.
Neuroglia includes many types of cells
that generally support, insulate, and
protect neurons.
Types of Neuroglial cells•Astrocytes-
•Microglia•Ependymal cells•Oligodendrocytes-
What about
“gliomas”???
Supporting Cells of the
Peripheral Nervous System
•Satellite cells•Schwann cellsMyelin
Neurilemma is found covering the
neuronsof the Peripheral Nervous
System and helps regenerate
damaged nerve fibers
Which brings us to bundles of nerve
fibers•Tracts•Nerves-
And gray matter vs. white matter-
THE NEURON
THE
NEURON
•Nerve fibers may be microscopic
•May extend 3 to 4 feet
•Neurons never touch each other
•Axonal terminals release
neurotransmitters into the synapse
Neurons classified according
to structure and function
1. FunctionalSensory or AfferentMotor or EfferentAssociative or Interneurons-
2. Structural- based on # of processes
extending from cell body
Physiology of
Neurons
Neurons have two major functions
1.Irritability-
2. Conductivity-
Irritabililty- the short version
•Resting or inactive neuron is polarized
•A stimulus excites the neuron to become
and generate an impulse
active
•The stimulus changes the permeability of the
neuron’s membrane
• Sodium gates open and Na diffuses into the cell
•Neuron is now depolarized
• Depolarization activates the neuron to transmit
an action potential or nerve impulse
Depolarization is followed almost
immediately by repolarization
Until the neuron repolarizes it cannot
conduct
another impulse= absolute refractory
period
There also exists a relative refractory
period when a stronger than usual
stimulus is required
The Action Potential
GENERATION OF AN ACTION
POTENTIAL
Alcohol, sedatives, anesthetics-
Cold and continuous pressureWarm or remove pressure-
Conductivity
No contact between neurons
except at electrical
synapses (escape
reflexes, retina, heart)
Axonal terminals release
neurotransmitters which
cause depolarization of
next neuron
Neurotransmitter is removed
from synapse by reuptake at axonal terminal
or enzymatic breakdown
YouTube - Neurotransmitter Synapse 3D
Animation
Peripheral Nervous System
• Those nerves found outside the central
nervous system
• Each nerve is made of bundles of neuron
fibers
• Neuron fibers are surrounded by a delicate
tissue sheath
• Groups of fibers are bound by coarser
connective tissue wrapping to form bundles
called fascicles
CRANIAL
NERVES
•
•
•
•
SPINAL NERVES
•
•
•
•
Spinal Nerves
DISORDERS AFFECTING
NEURONS
POLIOMYELITIS
MULTIPLE SCLEROSISBELL’S PALSYSHINGLES-
And then there’s…
CARPAL TUNNEL
SYNDROME-
http://www.youtube.com/watch?v=SGyKQch
SEJ4&feature=related