Introduction
 Control and communication center of the body
 interprets incoming data
 Fight or flight
 Generates thoughts
 Controls behaviors
Organs
 Brain
 Spinal Cord
 Nerves
 Specialized sense organs
 Eyes, ears and skin receptors
Neuron
 Neuron = Nerve cell
 Transmits information from one cell to
another
 Can amplify or dampen signal
 Consist of cell body, dendrites and an
axon
 Three main types of neuron:
 Sensory Neurons
 Motor Neurons
 Associative Neurons
Sensory Neurons
 Afferent neurons
 Emerge from sensory organs (ex. Skin)
 Transmit impulses toward the brain or spinal cord
Motor Neurons
 Efferent Neurons
 Carry impulses away from the brain or spinal cord to
muscles and glands of the body
Associative Neurons
 Interneurons
 Carry impulses from sensory neurons to motor
neurons
Structure
 Cytoplasmic extentions  Dendrite:
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receives information
Cells may have several, one or none
Typically short and branched
 Axon:
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


Transmits impulses away
Cell has only one
Long
Branch at their ends – Axon Terminals
 Make contact with dendrites of other neurons
Structure Cont .
 Multipolar: neuron with many dendrites
 Most neurons of the brain and spinal cord
 Bipolar: neuron with only one dendrite
 Receptor cells in: inner ear, nose, retina
 Unipolar: only one extension; serves as both an axon
and a dendrite
Myelin Sheath
 Neurilemma
 Insulating material that covers axon of neuron
 Similar to plastic around electrical wire
 Gives nerves there white appearance
 Made up of Schwann Cells (neurolemmocytes)
 Nodes of Ranvier: Gaps on myelin sheath
 Gaps allow substances (needed for energy) to flow from
extracellular fluid to axons
 Capable of regeneration. Not found in brain or spinal cord.
Neuroglial Cells
 Insulate, support, and protect neurons
 Do not conduct nerve impulses
 Schwann Cells
 Astrocytes:
 Star shaped
 Part of the blood brain barrier
 Oligodendroglial cells:
 Support
 Create myelin located in the brain and spinal cord
 Microglial cells:
 Protect neurons (phagocytosis)
 Ependymal Cells:
 Produce CSF in ventricals
 Help to move CSF
Nerves
 A group of peripheral nerve fibers
 Each axon is surrounded by endoneurium
 Wrapped axons are grouped fascicles
 Fascicles are surround by perineurium
 The whole nerve is covered by epineurium
Nerve Impulses
 A self-propagating wave of electrical disturbance
 Must be initiated by a stimulus
 Resting neurons have a slight positive charge on the
outside and a slight negative charge on the inside
Nerve Impulses, cont’d
 When the membrane is stimulated, sodium rushes in
causing a reverse of the charges
 If the membrane is covered in myelin, the impulse
jumps in what is called saltatory conduction
Synapse
 Three structures:
 Synaptic knob
 Synaptic cleft
 Plasma membrane of the
postsynaptic neuron
Synapse
 Area between the terminal branches of an Axon and
the ends of a branched Dendrite
 Axons and Dendrites never actually touch. Nerve
signals “jump” the space between the two called the
synaptic cleft
 How do nerve signals jump? Neurotransmitters
Neurotransmitters
 Neurotransmitters: chemical messengers, found in
synaptic knobs
 Acetycholine
 Epinephrine (autonomic)
 Dopamine
 Seratonin
 Endorphins
 Enkephalins
Synapse and Synaptic Cleft
Reflex Arcs
 Involuntary reaction to an external response.
 Two neuron and three neuron arcs
 Only allow impulse conduction in one direction
 Starts at the beginning of dendrites to its cell body in
the ganglion,
Reflex Arcs
 The dendrites of the sensory neuron pick up a signal
and send it to the cell body in the ganglion.
 The axon of the sensory neuron travels from the cell
body and ends near the dendrites of a motor neuron.
 The signal jumps the synapse and is sent down the
dendrites to the cell body and to the axon of the motor
neuron to the “effectors” organ
Functions
 Sensory
 Integrative
 Motor
Reflex Arcs
 3 Neuron Reflex
 The sensory neuron’s axon synapses with the dendrites of
the interneuron
 The signal is send down the interneuron to the dendrites of
the motor neuron
 The “withdrawal” reflex
 All interneurons lie within the gray matter of the brain and
spinal cord
Day 2
Divisions of the Nervous System
 Central Nervous System
 Brain
 Spinal Cord
 Peripheral Nervous System
 Nerves
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
Cranial Nerves
Spinal Nerves
Divisions of the PNS
 Somatic Nervous System (SNS):
 Connects CNS to Skin, Skeletal Muscle
 Initiates voluntary responses
 Autonomic Nervous System (ANS):
 Connects the CNS to Visceral Organs
 Initiated involuntary responses
 Sympathetic
 Fight or Flight
 Parasympathetic
 Restores homeostatic balance
Divisions
 Brainstem
 Medulla oblongata
 Pons
 Midbrain
 Cerebellum
 Diencephalon
 Hypothalamus
 Thalamus
 Cerebrum
The Brain
 Responsible for all human physical and mental
functions
 Gray Matter: Cell Bodies
 White Matter: bundles of Axons (covered in Myelin)
Meninges
 Protective tissues that surround the brain and spinal cord
 Dura (outermost)
 Tough fibrous connective tissue
 Does not attach directly to the vertebrae. Space between
vertebra and dura is termed Epidural space
 Arachnoid
 Thin, weblike
 Pia
 Space between the arachnoid and pia layers is termed the
subarachnoid space
Cerebral Cortex
 Surface
layer of the
brain
Cerebrum
 Largest portion of the human brain
 Gyri: convolutions
 Sulci: deep grooves (fissures)
 Divided into two hemispheres by the Longitudinal
Fissure
 Transverse Fissure: separates the cerebrum from the
cerebellum
Cerebrum Cont.
 Right Hemisphere:
 Nonverbal, intuitive behaviors
 Left Hemisphere:
 Speech, computational, analytical skills
 What hemisphere dominates you?
 90% Left
Cerebrum Cont.
 Sulci and gyri also divide the cerebrum into lobes
named for the bone that covers it:
 Frontal
 Temporal
 Parietal
 Occipital
Ventricles & CSF
 Interconnected canals and cavities
 Filled with clear, colorless fluid (CSF)
Cerebellum
 Essential role in movements
 Produces smooth, coordinated movements, maintain
equilibrium, and sustain normal posture
 Bell shaped structure under the occipital lobe
Diencephalon
 Consists of 2 major structures
 Hypothalamus helps control vital functions, water
balance, and body temp.
 Thalamus helps produce sensations and associates
sensations with emotions
Mesencephalon
 Midbrain
 Contains white
matter and gray
matter
Brainstem
 Composed of 3 structures
 Medulla-upward extension of spinal cord located
above foramen magnum.
Blood Supply
 Carotid artery
 Anterior cerebral artery
 Middle cerebral artery
 Median anterior spinal artery
Spinal Cord
 Provides two-way conduction
 Ascending tracts direct impulses to the brain
 Descending tracts direct impulses away from the brain
Day 3
Cranial Nerves
 I – Olfactory
 II – Optic
 III – Oculomotor
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IV – Trochlear
V – Trigeminal
VI – Abducens
VII – Facial
VIII – Vestibulocochlear
IX – Glossopharyngeal
X – Vagus
XI – Accessory
XII – Hypoglossal
Cranial Nerves Cont.
Spinal Nerves
 31 total
 8 cervical
 12 thoracic
 5 lumbar
 5 sacral
 1 coccygeal
Neoplasms
 Primary- neural tissues or meninges
 Secondary- metastatic lesions
 Intracranial tumors- diagnosed with CT
 Compression
 Destruction
 Irritation
 Increase intracranial pressure