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Chapter 12
Nervous system Exam III
74
Anatomy
Undergraduate 2
11/05/2011

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Term
Nervous System: Overview
Definition
THE master control and communications center in the body
Communication occurs via electrical signals
Term
Nervous system: Functions
Definition
Sensory receptors monitor changes
Integration (processing and interpreting)
Response (motor output)
Term
Centeral nervous system
Definition
Brain and spinal cord, integrative and control centers.
Term
Peripheral nervous system
Definition
Cranial nerves and spinal nerves, communication lines between the CNS and the rest of the body.
Term
Sensory (afferent) division, under PNS
Definition
Somatic and visceral nerve fibers, conducts impulses from receptors to the CNS
Term
Motor (efferent) division, under PNS
Definition
Motor nerve fibers, conducts impulses from the CNS to effectors (muscles and glands)
Term
Somatic nervous system, under motor division
Definition
Somatic motor (voluntary), conducts impulses from the CNS to skeletal muscles.
Term
Autonomic nervous system, under motor division
Definition
Visceral motor (involuntary), conducts impulses from the CNS to cardiac muscles, smooth muscles, and glands.
Term
Sympathetic division, under ANS
Definition
Mobilizes body systems during activity
Term
Parasympathetic division, under ANS
Definition
Conserves energy, promotes house-keeping functions during rest.
Term
Sensory (afferent) simplified function
Definition
Carry signals TO brain/spinal cord
Term
Motor (efferent) simplified function
Definition
Carry signals FROM brain/spinal cord.
Term
Somatic simplified function
Definition
Structures external to visceral cavity.
Term
Visceral
Definition
Organs
Term
Somatic sensory
Definition
Pain, pressure, vibration, temperature
Includes proprioception (sense that detects the amount of stretch in mm, tendons and joint capsules)
Term
Special somatic sensory
Definition
Hearing, equilibrium, vision
Term
Somatic motor (voluntary)
Definition
Muscle contraction
Term
Visceral sensory
Definition
Stretch, pain, temperature from viscera
Term
Special visceral sensory
Definition
Taste and smell
Term
Visceral motor (involuntary)
Definition
autonomic nervous system, Smooth and cardiac mm, gland secretion
Term
Components of Neuron
Definition
Cell body, dendrites, axons
Term
Cell body
Definition
Contains one nucleus, Metabolic center of neuron (contains organelles)
Term
Group of cell bodies in CNS
Definition
Nucleus
Term
Group of cell bodies in PNS
Definition
Ganglia
Term
Dendrites
Definition
Branched processes that extend from cytoplasm of cell body (also have organelles like soma)
Receive stimuli and conduct impulses to cell body
Term
Axons
Definition
If myelinated or large, have increased electrical conduction speed
Lengths vary; have axon terminals at end (bulbs)
Is a cytoplasmic extension from cell body
Term
Axons conduct impulses...
Definition
away from cell body.
Term
Myelinated Sheaths: overview
Definition
Myelin speeds up conduction and is produced by: Schwann cells in PNS, Oligodendrocytes in CNS
Term
Oligodendrocytes
Definition
CNS, Nodes of Ranvier also present but not as frequent
Term
Schwann cells
Definition
PNS, Gaps called nodes of Ranvier because cells don’t touch
Term
Special characteristics of nervous tissue
Definition
Extreme longevity – Live and function for a lifetime
Do not divide – Can’t replace themselves
High metabolic rate – Need oxygen and glucose to survive
Term
Synapses
Definition
Junction that controls information transfer from one neuron to the next, Synapse can be excitatory or inhibitory
Term
Synapses: Presynaptic neuron
Definition
conducts signal towards synapse
Term
Synapses: Postsynaptic neuron
Definition
conducts signal away from synapse
Term
Neuron structure types
Definition
Multipolar, Bipolar, Unipolar
Term
Neuron structure types: Multipolar
Definition
Most of body’s neurons – many dendrites and an axon (motor neurons, most interneurons)
Term
Neuron structure types: Bipolar
Definition
Processes extend from two sides of body (rare, sensory)
Term
Neuron structure types: Unipolar
Definition
One process that divides like a “T” (sensory neurons)
Term
Neuron types functional
Definition
Sensory (afferent), motor (efferent), interneurons
Term
Neuron types functional: sensory neurons
Definition
carry signal TO CNS
Term
Neuron types functional: motor neurons
Definition
carry signal AWAY from CNS
Term
Neuron types functional: Interneurons (association neurons)
Definition
are between sensory and motor neurons – located ONLY in CNS
Term
Neuroglia: overview
Definition
Have central cell body and branching processes, are smaller than neurons. In general they provide a scaffold of support for neurons and cover non-synaptic parts (to insulate and keep them from interfering with each other)
Term
Neuroglia outnumber neurons in CNS
Definition
10 to 1
Term
Neuroglia make up what % of brain mass?
Definition
50%
Term
Types of Neuroglia in CNS
Definition
Astrocytes, microglia, ependymal cells, oligodendrocyte
Term
Types of Neuroglia in PNS
Definition
Satellite cells and Schwann cells
Term
Astrocytes
Definition
Most abundant neuroglia
Key component of blood brain barrier
Regulate passage of molecules from blood to brain
Only allow small molecules through to brain
Term
Microglia
Definition
Smallest and least abundant neuroglia
Phagocytes, thorny-looking
Term
Ependymal cells
Definition
Form simple epithelial layer that lines central cavity of brain and spinal cord
Term
Oligodendrocytes
Definition
Produce myelin sheath around nerve cell axons
Fewer branches than astrocytes
Term
Satellite cells
Definition
Surround cell bodies in ganglia
Term
Schwann cells
Definition
Surround all axons in PNS
Produce myelin sheath (gaps = nodes of Ranvier)
Term
Nerves: overview
Definition
Collection (bundle) of neurons outside CNS (in PNS)

Nerves often contain both sensory and motor neurons (mixed nerves)
Some are sensory or motor only though (cranial nerves)
Term
Nerves: Naked eye can see a .... but not an ....
Definition
Nerve, neuron
Term
Nerves: are composed by many...
Definition
axons
Term
Nerves: Neurons are held together by...
Definition
CT
Term
Nerves: Endoneurium
Definition
surrounds each axon (loose CT)
Term
Nerves: Perineurium
Definition
surrounds bundle of axons (fascicle)
Term
Nerves: Epineurium
Definition
surrounds entire nerve (bunch of fascicles)
Term
Reflex arcs: Overview
Definition
Chains of neurons that create reflexes, Unlearned and involuntary, somatic or visceral.
Term
Reflex
Definition
rapid, automatic, motor response to a stimulus
Term
Components of reflex arcs
Definition
Receptor, sensory neuron, integration center, motor neuron, effector.
Term
Reflex arcs: Receptor
Definition
site where stimulus acts
Term
Reflex arcs: Sensory neuron
Definition
transmits signal to CNS
Term
Reflex arcs: Integration center
Definition
one or more synapses
Term
Reflex arcs: Motor neuron
Definition
conducts impulse from integration center
Term
Reflex arcs: Effector
Definition
muscle of gland that responds
Term
Types of reflex arcs: Monosynaptic
Definition
One synapse is involved (no interneuron)
Fastest of all reflexes
Classic example is knee jerk
Term
Types of reflex arcs: Polysynaptic
Definition
One or more interneurons are part of reflex pathway
Most contain one interneuron (are 3-neuron reflexes)
Most common reflex
Term
Gray matter
Definition
means cell bodies. Is H-shaped in spinal cord (dorsal half has bodies of interneurons and ventral half has bodies of motor neurons)
Term
White matter
Definition
axons (often myelinated)
Term
Tracts
Definition
bundles of axons
Term
Multiple sclerosis
Definition
Most common neural disability in young adults
Progressive, destroys patches of myelin
Cause is not well understood - autoimmune
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