MS. HARBORTH ANATOMY AND PHYSIOLOGY CHAPTER 7 NERVOUS
SYSTEM
Slide 2
STRUCTURAL CLASSIFICATION Central nervous system (CNS) consists
of the brain and spinal cord. Command center Peripheral nervous
system (PNS) part of body outside of CNS. Spinal nerves carry
impulses to and from spinal cord Cranial nerves carry impulses to
and from the brain
Slide 3
PNS Sensory (afferent) carries impulses FROM sensory organs TO
the brain Motor (efferent) carries impulses FROM the brain TO
effector organs, muscles, and glands. Somatic nervous system
control skeletal muscles Autonomic nervous system regulates
automatic events (smooth and cardiac muscle) Sympathetic
Parasympathetic
Slide 4
NERVOUS TISSUE Supporting cells of CNS neuroglia Astrocytes
barrier between neurons and capillaries Microglia phagocytes that
clean Ependymal cells beat cilia to circulate cerebrospinal fluid
Oligodendrocytes form myelin sheaths Supporting cells of PNS:
Schwann cells form myelin sheaths Satellite cells protective,
cushioning cells Neurons Cell body (Nissl substance &
neurofibrils) Processes (fibers) Myelin sheath, Schwann cells
(PNS), nodes of Ranvier Dendrites (toward cell body) Axons (away
from cell body) Axonal terminals, neurotransmitters, synaptic
cleft, synapse
MULTIPLE SCLEROSIS Immune system gradually destroys myelin
sheaths, converting to scleroses (hardened processes)
Slide 8
VOCAB Nuclei clusters of cell bodies in the CNS Ganglia small
collections of cell bodies found in the PNS. Tracts bundles of
nerve fibers in the CNS Nerves bundles of nerve fibers in the PNS
White matter myelinated fibers in the CNS Gray matter unmyelinated
fibers and cell bodies in the CNS
Slide 9
CLASSIFICATION OF NEURONS Functional (direction of nerve
impulse) Sensory (afferent) neurons neurons carrying impulses from
sensory receptors to the CNS. Cell bodies are found in ganglion
outside of CNS. Cutaneous sense organs, proprioceptors Motor
(efferent) neurons neurons carrying impulses to viscera and/or
muscles and glands. Cell bodies are in the CNS. Association neurons
(interneurons) connect motor and sensory neurons in neural
pathways.
Slide 10
CLASSIFICATION OF NEURONS Structural Multipolar neuron several
processes extending from cell body. All motor and association
neurons Bipolar neuron axon and dendrite extend from cell body
Rare. Found in some special sense organs. Unipolar neuron short,
single process that usually divides into proximal and distal
fibers. Axon conducts nerve impulses both toward AND away from the
cell body. Sensory neurons found in PNS ganglia
Slide 11
NEURON PHYSIOLOGY Nerve impulse Irritability 1. Inactive neuron
is polarized (more negative inside) 2. Stimulus excites neuron,
permeability increases 3. Depolarization Action Potential 4.
Repolarization Saltatory conduction occurs on myelinated nerves
FASTER Cold and continuous pressure hinder conduction Conductivity
When action potential reaches axonal endings, tiny vesicles fuse
with axonal membranes, rupture, and releases neurotransmitters
which start impulse in next neuron Electrochemical event
animation
Slide 12
NEURON PHYSIOLOGY Reflex Arc Autonomic reflexes Regulate
activity of smooth muscles, heart, and glands. Ex: salivary reflex
and pupillary reflex. Somatic reflexes Reflexes that stimulate
skeletal muscles Minimum of five elements: Sensory receptor
Afferent neuron Integration center Efferent neuron Effector
organ
Slide 13
CENTRAL NERVOUS SYSTEM Embryonic development: Neural tube
develops 4 th week anterior end of neural tube expands and brain
formation begins. Central canal of neural tube becomes 4
ventricles
Slide 14
FUNCTIONAL ANATOMY OF THE BRAIN Cerebral Hemispheres
Diencephalon Cerebellum Brain Stem
Slide 15
CEREBRAL HEMISPHERES Gyri : elevated ridges of tissue Sulci :
shallow grooves Fissures : deeper grooves which separate large
regions of the brain Hemispheres separated by longitudinal fissure
Lobes are named for cranial bones that surrounding them
Slide 16
CEREBRAL HEMISPHERE Parietal lobe : posterior to central sulcus
Somatic sensory area localizes and interprets impulses from sensory
receptors. Sensory pathways cross (left -> right, right ->
left) Occipital lobe : visual area Temporal lobe : auditory and
olfactory area Frontal lobe : Higher intellectual reasoning in
anterior part Primary motor area - Axons of motor neurons form
pyramidal (corticospinal) tract which descends to spinal cord.
Pathways are crossed. Brocas area speech. Only found in one
hemisphere Speech area junction of temporal, parietal, and
occipital lobes. Sound out words. One hemisphere. Gray matter (
cerebral cortex ): cell bodies of neurons White matter : fiber
tracts carrying impulses to or from the cortex Corpus callosum :
large fiber tract that connects cerebral hemispheres. Allows halves
to communicate with one another. Basal nuclei : islands of gray
matter buried in white matter. Modify instructions sent to
muscles.
Slide 17
Slide 18
Slide 19
Slide 20
DIENCEPHALON Thalamus Encloses third ventricle Relay station
for sensory impulses Hypothalamus Regulation of temperature, water
balance and metabolism. Regulates pituitary Limbic system
emotional-visceral brain. Thirst, appetite, sex, pain, pleasure
centers. Mammillary bodies reflex involved in olfaction Epithalamus
Pineal body Choroid plexus of third ventricle
Slide 21
DIENCEPHALON
Slide 22
BRAIN STEM Midbrain Cerebral aqueduct canal that connects third
ventricle of diencphalon to fourth ventricle below Cerebral
peduncles convey ascending and descending impulses Corpora
quadrigemina reflex centers for vision and hearing Pons Mostly
fiber tracts, but does have some nuclei involved in controlling
breathing Medulla oblongata Merges into spinal cord. Regulate vital
visceral activities. Controls heart rate, blood pressure,
breathing, swallowing, and vomiting Reticular formation Neurons
involved in motor control of the visceral organs. RAS (reticular
activating system) plays a role in consciousness and awake/sleep
cycles. Damage to this area results in coma.
Slide 23
BRAIN STEM
Slide 24
CEREBELLUM Two hemispheres Timing for skeletal muscle activity
and controls balance/equilibrium Takes info from eyes, ears and
muscles to coordinate movements in a smooth fashion
Slide 25
MENINGES Three connective tissue membranes covering and
protecting brain and spinal cord Dura mater outermost layer.
Double-layered, forms periosteum and meningeal layer. Arachnoid
mater span subarachnoid space to attach to innermost membrane
Subarachnoid space filled with cerebrospinal fluid. Arachnoid villi
protrude through dura mater. Dural sinuses absorb fluid into blood
through arachnoid villi. Pia mater delicate layer clings tightly to
surface of brain and spinal cord. Meningitis inflammation of
meninges
Slide 26
Slide 27
Cerebrospinal fluid (CSF) similar to blood plasma. continually
formed from blood by choroid plexuses continually moving.
Blood-brain barrier any changes in fluid around brain could be
detrimental. Barrier composed of the LEAST permeable capillaries in
whole body. Water, glucose and essential amino acids can pass
through.
Slide 28
SPINAL CORD 17 inches long, thickness of a thumb Extends from
foramen magnum to 1 st or 2 nd lumbar vertebrae, right below ribs
Cauda equina
Slide 29
Slide 30
PERIPHERAL NERVOUS SYSTEM Endoneurium Perineurium Fascicles
Epineurium Nerves are classified by which direction they transmit
Mixed nerves Afferent (sensory) Efferent (motor)
Slide 31
CRANIAL NERVES 12 pairs (table 7.1) Serve head and neck (except
vagus nerves extend to thoracic and abdominal cavities) I.
Olfactory II. Optic III. Oculomotor IV. Trochlear V. Trigeminal VI.
Abducens VII. Facial VIII. Vestibulochochlear IX. Glossopharyngeal
X. Vagus XI. Accessory XII. Hypoglossal
Slide 32
SPINAL NERVES/ NERVE PLEXUSES 31 pairs of spinal nerves formed
by combo of ventral and dorsal roots of spinal cord. Named for
region of spinal cord from which they arise. Each spinal nerve
divides into dorsal and ventral rami Dorsal rami serve skin and
muscles of posterior body trunk Ventral rami of T 1 T 12 form
intercostal nerves Ventral rami of other spinal nerves form 4
plexuses (Table 7.2)
Slide 33
AUTONOMIC NERVOUS SYSTEM Motor subdivisions that control
automatic activities (cardiac and smooth muscle, and glands)
Sympathetic and parasympathetic Sympathetic mobilizes body during
extreme situation (fear, exercise, rage, etc.) Parasympathetic
allows us to unwind and conserve energy
