The Nervous System - Poudre School District
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The Nervous System
Poudre High School
By:
Ben Kirk
Functions
Regulation of all body function
Sensory: Information reception
Response: Response transmission
Integrate: Integrate and interpret all body
changes/stimuli
Organization
Central Nervous System (CNS): Brain
and Spinal Cord
Control center for the entire nervous system
Receives, processes, integrates and
produces responses to all stimuli
Higher Functioning (the brain primarily):
intelligence, memory, thought, emotion and
learning
The Central Nervous System
http://www.sruweb.com/~walsh/cns_pns.jpg
Organization
Peripheral Nervous System (PNS): All
neural tissue outside the CNS
Delivery of sensory information from sensory
glands/organs to the CNS
Transmission of motor information from the
CNS to effectors glands/organs
Organization
Peripheral Nervous System
Somatic Nervous System: Voluntary
Controls voluntary muscle contractions (skeletal
muscle)
Autonomic Nervous System: Involuntary
Involuntary movements, processes and reflexes
Visceral organs, cardiac muscle, smooth muscle
and glands (heart rate, vessel diameter,
digestion, etc…)
Organization
Autonomic Nervous System
Sympathetic Nervous System: Expenditure of
energy
Fight or Flight
Increased Heart Rate
Parasympathetic Nervous System: Restoration
and conservation of energy
Rest and Digest
Slows Heart Rate
http://www.sirinet.net/~jgjohnso/nervous.html
Histology
Neuroglia: Glial Cells
6 Types of glia cells
Primary Function is to protect and support
neurons
Smaller and more numerous (5-10X) than
neurons
Common source of tumors (Gliomas)
40-45% of all brain tumors
Histology
Neurons: Conduct impulses from one part of
the body to another
Cell Body (Soma):
Large, pronounced nucleus
No myotic apparatus in cytoplasm
Neuron reproduction/regeneration is compromised
Dendrites:
Highly branched processes extending from cell body
Each neuron in the CNS has 10,000-100,000 dendrite
branches.
Each branch has 100,000-1million sensory inputs!!!
Histology
Neurons:
Axon: Single thin extension that sends
electrical impulses to other neurons or
tissues
1mm-1meter in length
Axon Terminal contains neurotransmitters that
are released to trigger subsequent impulses
Axon Hillock: Where all electrical impulses
are summated to trigger an impulse, or not.
The Neuron
Histology
Neuron:
Myelin (myelin sheath): Multiple layered,
lipid and protein sheath covering neuron
axons (not all axons are myelinated)
Electrically insulates axon and increases
conduction speed (Ex. Leaky garden hose)
Multiple Sclerosis: Autoimmune disease that
breaks down the myelin sheath in the CNS.
Tremors: Unregulated electrical impulses
Histology
Neurons:
Myelin:
Myelin Production
Schwann cells (PNS): Myelinate a single segment of a single
axon.
Have limited ability to regenerate PNS neural tissue
Oligodendrocyte (CNS): A single oligodendrocyte can
myelinate multiple segments of multiple axons
CNS neuron regeneration is very complex and relatively
nonexistent.
Myelination = White
Unmyelinated = Gray
Classification of Neurons
Structural: Based on the # of processes
extending from the cell body
Multipolar: many dendrites and one axon
Most cells of the CNS
Bipolar: One dendrite and one axon
Retina of eye, inner ear and nose
Unipolar: Has one continuous branch with both an
axon and a dendrite (cell body off to side)
Dorsal root ganglia (sensory cell bodies of spinal nerves)
Classification of Neurons
Functional: Based on the direction of impulse
propagation
Sensory (Afferent): Transmit impulses from
receptors in skin, muscles, sensory organs, joints,
and viscera to the CNS
Motor (Efferent): Transmit impulses from the CNS
to peripheral effectors (muscles and glands)
Interneuron (Association): Carry impulses from
sensory neurons to motor neurons within the CNS
Make up the majority of human neurons
Grouping of Neural Tissue
Nerve Fiber: Any process projecting from a
cell body
Axon or dendrite
Nerve: A group of many fibers within the PNS
Not a neuron
Usually contain both sensory and motor nerve fibers
sciatic nerve, ulnar nerve
Ganglia: Group of cell bodies and synapses
within the PNS.
Grouping of Neural Tissue
Tract: Bundle of fibers within the CNS
May run long distances up or down the spinal
column or connecting parts of the brain
Ascending tracts carry information upward (sensory)
Descending tracts carry information downward
(motor)
White Matter: Group of myelinated axons from
many neurons
Look white due to myelination
Grouping of Neural Tissue
Gray Matter: Unmyelinated axons,
dendrites, or cell bodies within the CNS
Found covering the outer surfaces and in the
deeper regions (nuclei) of the brain
Compose the “horns” of the spinal cord