Functions of the nervous system
1. sensory function
2. integration function
3. motor function
Overall maintains the homeostasis
of body
-with
endocrine system
-homeostasis
-what
is maintained
-what occurs when homeostasis is not maintained
Organization of Nervous System
Two principles parts
1. central
nervous system
2. peripheral
nervous system
Central Nervous system
-consists of
-control center for
-all body sensations
-all nerve impulses
Peripheral Nervous System
-consists of
-receptors
-effectors
Neurology
Histology
-two principal kinds of cell
1. neurons
(nerve cells)
2. neuroglial
cells
Neuroglial Cells
-features
-functions of
Neurons
1. structure
-variations
of
-consists
of
a) cell body
b) dendrites
c) axon
2. Cell Body
-consists of
-lack
3. Dendrites
-consist
of
-function
to
4. Axons
-consist
of
-variation
in length
-have side branches
-distal ends
-synaptic end bulb
-functions to
-nerve fiber
-many axons are surrounded by
-myelin sheath
-white matter
-unmyelinated axons
Classification of Neurons
A. functional classification
1. sensory
neurons
2. associative
neurons
3. motor neurons
-effectors =
Physiology of the Neuron
Nerve Impulse
-general features
-reaction time
-events that occur:
1. Before
anything occurs the neuron has an electric potential difference between
the
outside
and the inside of the neurons membrane. This is called the resting state.
The potential
is due to the fact that there are more positive ions on the outside of
the
membrane
and more negative ions on the inside.
2. When
a sufficient stimulus (threshold stimulus) is applied to the nerve, the
result is a
change
in polarity. This occurs due to a change in the permeability, allowing
ions to flow
across
the membrane. The result is a depolarized membrane where the outside is
now
more
negative and the inside is now more positive. The change in the polarity
is called
a nerve
impulse. The change in polarity only lasts for .001 sec with a resulting
reestablishment
of the original polarity (repolarized).
3. The
next region of the neuron becomes depolarized etc. The nervous impulse
then
spreads
down the neuron.
-what cells can do this
-excitability
-refractory period
Characteristics of the Nerve Impulse
1.
2. all-or-none law
3.
4.
Speed of the impulse
-varies
-myelinated neurons
-unmyelinated neurons
Synaptic transmission
-when an impulse reaches the
end of an axon
-synapse
-synapse is the same as
-steps of
1. When
the nerve impulse reaches the end of the axon, the synaptic end bulb releases
the neurotransmitter
substance into the synapse.
2. These
chemicals diffuse across the synapse and combine with the receptor sites
on
the adjacent
dendrite.
3. This
causes the membrane to depolarize and a new impulse is started on this
next
neuron.
(An example
of a neurotransmitter is acetylcholine which is also involved in muscle
contraction.
Certain
chemicals act to inhibit the impulse. An example is norepinephrine in the
brain's
neurons.
These are useful when a cell is receiving many stimuli. Acts as a buffer.)
4. Enzymes
present in the synapse break down the released neurotransmitters so as
to
stop
their effect. Example is acetylcholinesterase.
Clinical Applications
1. myasthenia gravis
2. curare
3. nerve gas
4. Botulism toxin
5. tranquilizers and anesthetics
6. caffeine and nicotine
7. pressure on nerves
Regeneration
Organization of Neurons
-neuronal pools
Disorders Involving Neurons
1. shingles
-what
is it
-due to
-chickenpox
-caused by
-herpes zoster
-what
occurs
-what causes
-results in
2. Multiple Sclerosis (MS)
-what
is it
-what occurs
-plaques
-occurs when
-symptoms
-remission
-as the disease progresses
-speed of disease
-results
in
-cure
-cause
3. Poliomyelitis (Polio)
-called
infantile paralysis
-when occurs
-caused by
-virus found
-what is it
-symptoms
-sever cases
-final result
-incidence of
-Salk and Sabin vaccines
Groupings of Neural Tissue
1. white matter
2. gray matter
3. nerve
4. ganglia
5. tracts
Structure of the Spinal Cord
A. General Features
B. Protective Coverings
1. Vertebral column
2. meninges
C. Cerebrospinal Fluid
D. Physical Attachments
Structure of the Brain
A. General Features
B. Principal parts
1. brainstem
2. diencephalon
3. cerebrum
4. cerebellum
Brainstem
1. medulla
oblongata
2. pons
3. midbrain
(mesencephalon)
Diencephalon
1. thalamus
2. hypothalamus
Cerebrum
-has
four lobes
1. temporal
2. frontal
3. parietal
4. occipital
Cerebellum
C. Protective Coverings
1. cranial
bones
2. cranial meninges
D. Cerebrospinal Fluid
-what
is it
-amount of it
-description of
-contains
-two principal
functions
E. Blood Supply
-well
supplied
-utilizes
-most metabolically active
-use of oxygen
-interruption
of blood flow
-glucose use
Parts of the Brain
A. Brainstem
1. medulla
oblongata
-what is it
-location of
-tracts of
-crossing over
-four cranial nerves
2. Pons
-location of
-size
-connects
3. midbrain
(mesencephalon)
-location
-cranial nerves
B. Diencephalon
1. thalamus
-location
-description of
-embedded in
2. hypothalamus
-location
-pituitary gland (hypophysis)
-neurons from it
C. Cerebrum
-size
-weight
-number of neurons
-surface compose of
-cerebral cortex
-beneath cerebral cortex
-development
of
-convolutions
-fissures
-longitudinal fissure
-hemispheres
-corpus collosum
-lobes
of hemispheres
1. frontal
2. temporal
3. parietal
4. occipital
-insula
Divisions
of the Gray Matter (of the cerebrum)
1. olfactory bulb
2. limbic system
3. basal ganglia (cerebral nuclei)
4. cerebral cortex
White
Matter (of the cerebrum)
-location
-consists of
1. associative fibers
2. commissural fibers
3. projection fibers
D. Cerebellum
-size
-location
-connected to
-vermis
-hemispheres
-cortex
-arbor
vitae
Peripheral Nervous System (PNS)
-consists
of
-two main
parts
1. afferent system
2. efferent system
Efferent System (two parts)
1. somatic nervous system
(SNS)
2. autonomic nervous system
(ANS)
Autonomic Nervous System (two parts)
1. sympathetic division
2. parasympathetic division
-general functions
Nerves
-description
-two categories
1. spinal
nerves
2. cranial
nerves
Spinal Nerves
-number of
-how are named
-consist of
Cranial Nerves
-consist of
-originate from
-exit through foramens of skull
-designated by
-contain
Receptors
-what are they
-stimuli
-what sorts of stimuli
-stimulus causes
-range in structure
Effectors