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The Nervous System
Functions
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Reception
Interpretation
Integration
Control of homeostasis
Mental Acuity
Control of Muscle and Glands
Anatomic Divisions of
the Nervous System
The Central Nervous System
Brain and Spinal Cord
The Peripheral Nervous System
Nerves and Ganglia
Physiologic Divisions of
the Peripheral Nervous
System
1. Sensory- (Afferent) carries messages to
the CNS
2. Motor- (Efferent)
Somatic- Carries messages away from
the CNS, from the brain to the skeletal
muscle. This is voluntary action
Autonomic –Controls cardiac muscle,
smooth muscle and glands and is under
involuntary control
Enteric- associated with digestive tract
The Nervous System
Cell
• The neuron
Consists of a cell body,
dendrites and axons
They receive the stimuli and
transmit the action potential
The Electrical Impulse
Resting Membrane Potential
Action Potential
The Synapse
Reflexes
The Nervous System
Tissue
• Neuron
• Neuroglia- support cells
• Myelin Sheaths – axon is either
myelinated or unmyelinated
• White matter and Gray MatterGray- cortex and nuclei in the
brain and ganglia of PNS
White_ nerve tracts in CNS and
nerves in PNS
The Neuralgia
The Brain Divisions
Cerebrum
Diencephalon
Cerebellum
Brainstem
The Brain Division
• CerebrumConsists of Two Hemispheres
Hemispheres are Subdivided
into Lobes
Frontal
Parietal
Occipital
Temporal
The Hemispheres of the
cerebrum
• Each hemisphere controls the
opposite half of the body
• Commissures connect the two
hemispheres
• The left hemisphere dominates
in analytical skills , the right
dominates for spatial
perception and musical ability
Divisions of the Brain
• Diencephalon
Thalmus- main sensory
relay center
Epithalmus- pineal gland
Hypothalamus- maintains
homeostasis
Brain divisions
• Cerebellum- in back attached to
the brainstem
Cerebellum
• The Cerebellum is involved in
balance and muscle coordination.
• An important function of the
cerebellum is to compare the
intended action with what is
occurring and modify it
• If damage to the cerebellum, there is
a decrease in muscle tone and,
balance
Division of Brain
BrainstemAscending and descending tracts
Divisions:
Medulla Oblongata- heart rate , breathing, swallowing
and balance
Pons- relay nuclei between cerebrum and cerebellum
Midbrain- involved in visual and hearing reflexes
Reticular formation- maintains consciousness and
sleep wake cycles
BRAINSTEM
The Twelve Cranial
Nerves
I
II
III
IV
V
VI
VII
VIII
IX
X
XI
XII
Olfactory
Optic
Oculomotor
Trochlear
Trigeminal
Abducens
Facial
Vestibulocohlear
Glossopharyngeal
Vagus
Accessory
Hypoglossal
The Cranial Nerves –
nerves coming right off the
brain
• There are twelve Cranial Nerves
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3 are sensory
•
4 are motor
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1 both motor and sensory
•
1 somatic motor and
parasympathetic
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3 with all three functions
•
4 are parasympathetic
The Meninges or
Coverings
• The Central Nervous System is
covered by three protective
layers:
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Dura Matter
•
Arachnoid Matter
•
Pia Matter
The Ventricles
• In the brain and spinal cord
there are fluid filled cavities :
• lateral ventricle
• third ventricle
• cerebral aqueduct
• fourth ventricle
• central canal
The Cerebrospinal Fluid
• The Cerebrospinal Fluid is formed in
the ventricles
• How does it circulate?
• It is made by the choroid plexus
then exists through the fourth
ventricle and it reenters the blood
through the arachnoid granulations
in the superior sagital sinus
The Spinal Cord
• Extends from the foramen magnum
to the second lumbar vertebrae after
which it is called the cauda equina
• Central part is Gray matter and the
Peripheral part is White Matter
forming the nerve tracts
• Roots of the Spinal Nerves Extend
out of the cord
Spinal Nerves: 31 pairs
of Spinal Nerves
• Exit from the cervical, thoracic,
and sacral regions
The nerves are grouped into Plexuses
Cervical Plexus- contains
Phrenic Nerve
Brachial Plexusnerves to upper limb
Lumbosacral Plexusnerves to the lower limb
How do we sense
Ascending Tracts
transmit the action potential
from the periphery to the brain
each tract contains a specific
type of sensory information
• Project to the primary area of
the cerebral cortex
Ascending Tracts
• Spinothalmic- pain temp, light
touch tickle itch
• Dorsal Column proprioception,
deep pressure and vibration
• Spinocerebellar- proprioception
to the cerebellum
How do we respond
Descending Tracts
• Upper motor neurons in the cerebral
cortex connect to the lower motor
neurons in the spinal cord, brainstem
and cerebellum and send out a
specific motor response
Descending Tracts for
movement Table 8.5
• Direct
lateral corticospinal
anterior corticospinal
Indirect
Rubrospinal
reticulospinal
vestibulospinal
Ascending
Descending
Simple Reflex
Autonomic Nervous
System
• Divided into
Sympathetic N.S.
Parasympathetic N.S.
Enteric N.S.
Sympathetic N.S.
• Prepares person for action by
increasing heart rate, blood
pressure and respiration rate.
“The Fight or Flight Response”
• Associated with the thoracic
and lumbar nerves ( T1- L2)
Parasympathetic N.S.
• Involved in vegetative activities
such as digestion of food,
defecation and urination. Slows
heart rate and respiration
• Located in
cranialnervesIII,VII,IX, X and
sacral nerves S2-S4
Enteric N.S.
• Associated with the digestive
tract
Neurotransmitters
• Acetylcholine-
• Norepinephrine-