Transcript Functional Human Physiology for the Exercise and Sport Sciences

Functional Human Physiology
for the Exercise and Sport Sciences
The Nervous System
Jennifer L. Doherty, MS, ATC
Department of Health, Physical Education, and
Recreation
Florida International University
Overview of the Nervous System

Two major anatomical divisions
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The central nervous system (CNS)
1)
2)
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Brain
Spinal Cord
The peripheral nervous system (PNS)
1)
2)
Afferent Division
Efferent Division
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Somatic Nervous System
Autonomic Nervous System
Overview of the Nervous System
 Functional Divisions of the PNS
 Afferent = Sensory
1) Somatic sensory
2) Visceral sensory
 Efferent = Motor
1) Somatic motor
2) Visceral motor
Overview of the Nervous System
 Divisions of the PNS according to type of
control
 Somatic nervous system
1) Voluntary
 Autonomic nervous system
1) Involuntary
2) Further divided according to the overall effect on
the organs:
 Sympathetic division = “Fight or Flight”
 Parasympathetic division = “Rest and Repair”
Functions of the Nervous System
 Collecting information
 Peripheral Nervous System
1) Sensory or afferent input
 Evaluation and decision making
 Central Nervous System
 Integration and comparison to:
 Homeostatic ranges
 Previous or learned experiences
 Elicits responses
 Peripheral Nervous System
1) Motor or efferent output
General Anatomy of the CNS
 Glial Cells
 Supporting cells for neurons in the CNS
 5 types
1)
2)
3)
4)
5)
Oligodendrocytes = form myelin in the CNS
Schwann Cells = form myelin in the PNS
Microglia Cells = macrophages of the CNS
Ependymal Cells = line cerebral ventricles
Astrocytes = develop neuronal connections
General Anatomy of the CNS
 Cranium/Skull
 Protects this soft tissue of the brain
 Vertebral Column
 Protects the spinal cord
 Meninges
 Connective tissue membranes that separate the
soft tissue of the CNS from surrounding bone
1) Dura Mater
2) Arachnoid mater
3) Pia Mater
General Anatomy of the CNS
 Cerebrospinal Fluid (CSF)
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Clear, watery fluid that bathes the CNS
Acts as a shock absorber to prevent injury
Provides nutrients to glial cells
Removes waste products
Maintains normal ionic concentrations
surrounding neurons
General Anatomy of the CNS
 The CNS requires an abundant blood
supply due to the high metabolic rate of
neuronal tissue
 Brain accounts for 20% of all O2 used
 Brain accounts for 50% of all glucose used
 Blood-Brain Barrier
 A physical barrier between the CSF and blood
 This semi-permeable membrane functions to
protect the environment surrounding the neurons
in the CNS
General Anatomy of the CNS
 Classification of Neurons
 Classified according to the direction that the nerve
impulse travels in relation to the central nervous system.
 Sensory / Afferent Neurons
 Receptors: located in the periphery
1) sensitive to changes inside or outside of the body
 Nerve impulses: travel toward the CNS
General Anatomy of the CNS
 Interneurons
 Also call Association / Internuncial neurons
 Function: link between afferent and efferent
neurons
1) Relay information from one part of the CNS to
another for processing, interpreting, and eliciting a
response
 Motor / Efferent Neurons
 Nerve impulses: travel away from the CNS toward
effector organs
General Anatomy of the CNS
 Gray Matter
 Areas of the CNS consisting primarily of:
1) Cell bodies
2) Dendrites
3) Axon terminals
 Area where synaptic transmission and neural integration
occurs
 White Matter
 Areas in the CNS consisting primarily of myelinated axons
1) Function to rapidly transmit action potentials over relatively
long distances
The Spinal Cord
 Cylinder of nervous tissue
 Continuous with the lower portion of the brain
 Branches into 31 pairs of spinal nerves
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Cervical nerves (C1 – C8)
Thoracic nerves (T1 – T12)
Lumbar nerves (L1 – L5)
Sacral nerves (S1 – S5)
Coccygeal nerve (C0)
The Spinal Cord
 Gray matter: concentrated in the butterflyshaped interior region of the spinal cord
 Ventral Horn
 Contains Efferent Neurons
1) Interneurons
2) Cell bodies
3) Dendrite
 Dorsal Horn
 Contains Afferent Neurons
1) Axon terminals
The Spinal Cord
 Afferent Nerve Fibers
 Cell bodies are located outside the spinal cord in
clusters called dorsal root ganglia
 These fibers form the dorsal roots
 Efferent Nerve Fibers
 Cell bodies are located in the spinal cord
 These fibers for the ventral roots
The Spinal Cord
 Spinal Nerves
 Contain both afferent and efferent axons
 Joining of the dorsal root and the ventral root
 Called Mixed Nerves
Spinal Cord
 White Matter: consists of Tracts providing
communication between
1) Different levels of the spinal cord, or
2) The brain and various levels of the spinal cord
 Ascending Tracts
 Transmit information from the spinal cord to the
brain
 Descending Tracts
 Transmit information from the brain to the spinal
cord
The Brain
 Forebrain
 Largest and most superior portion of the brain
 Divided into right and left hemispheres
 Consists of the Cerebrum and Diencephalon
 Cerebellum
 Located inferior to the forebrain
 Functions include motor coordination, balance, and
feedback systems
 Brainstem
 Connects the forebrain and cerebellum to the spinal cord
 Consists of the Midbrain, Pons, and Medulla Oblongata
The Brain – Cerebrum (Forebrain)
 Cerebral Cortex
 Thin, highly convoluted layer gray matter
 Responsible for conscious initiation of voluntary
movements
 Regions of the Cerebral Cortex
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Frontal Lobes
Parietal Lobes
Temporal Lobes
Occipital Lobe
The Brain – Cerebrum (Forebrain):
Areas of Specialized Function
 Primary Somatosensory Cortex
 Involved in processing somatic sensory
information associated with:
1) Somesthetic sensations such as touch, temperature
and pain perception
2) Proprioception which is the awareness of muscle
tension, joint position, and limb position
 Primary Motor Cortex
 Initiates voluntary movement
The Brain – Cerebrum (Forebrain)
 The cerebral cortex is topographically organized
 Areas may be mapped according to function
 Called somatotopic organization
 Motor and Sensory Homunculi
 Map of the cerebral cortex corresponding to the part of
the body served by a particular region
 The size of the body part on the homunculus is
proportional to the amount of brain dedicated to that body
part
1) For Example, the hand is very large on both the sensory and
motor homunculus because it has many sensory receptors
and requires very fine motor control.
The Brain – Cerebrum (Forebrain)
 Subcortical Nuclei
 Regions of gray matter within the cerebrum
 Includes the Basal Nuclei (Basal Ganglia)
 Masses of gray matter scattered deep within the
cerebral hemispheres
 Components of the basal nuclei include:
1) The caudate nucleus
2) The putamen
3) The globus pallidus
 Important role in modifying movement
The Brain - Basal Nuclei
 Normally inhibit motor function thereby
controlling muscle activity
 Receive input from:
 The entire cerebral cortex
 Other subcortical nuclei
1) Such as the subthalamic nucleus of the diencephalon,
substantia nigra, and the red nucleus
 No direct connections with the motor
pathways
 Send information to the Primary Motor Cortex through the
thalamus
The Brain - Basal Nuclei
 Complex role in motor control
 Important in starting, stopping, and monitoring
movements executed by the primary motor cortex
 It is particularly involved in slow, sustained, or stereotyped
movements
1) Examples: arm swing during gait, riding a bicycle, or eating
 Inhibit antagonistic (unnecessary) movements
 Enhances the ability to perform several tasks at once
 Impairment results in:
 Disturbances in muscle tone and posture
 Tremors
 Abnormally slow movement
The Brain – Diencephalon
(Forebrain)
 The diencephalon includes two structures:
1) Thalamus
2) Hypothalamus
Thalamus
 Referred to as the “gateway” to the cerebral
cortex
 Most afferent neurons synapse with at least
one of the thalamic nuclei
 The major relay station for all sensory input
(except smell)
 A relay station for impulses that regulate emotion
 Also a relay station for motor impulses from the
cerebellum and basal ganglia
Thalamus
 Consists of many separate groups of nuclei
 Each receiving a certain kind of information
 Information is sent from the thalamic nuclei to a
particular region of the cortex
 Nuclei of the Thalamus
 Ventral Posterolateral Nucleus
 Ventral Lateral Nucleus
 Medial and Lateral Geniculate Bodies
Thalamus
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The Ventral Posterolateral Nucleus
 Receives somatic sensory information (touch, pressure, pain)
 Relays information to the somatosensory region of the cerebral
cortex
 The Ventral Lateral Nucleus
 Receives motor information from the basal nuclei and
cerebellum
 Relays information to the motor region of the cerebral cortex
 The Medial and Lateral Geniculate Bodies
 The medial geniculate body sends auditory information from the
auditory receptors to the auditory region of the cerebral cortex
 The lateral geniculate body sends visual information to the
occipital region of the cerebral cortex
Hypothalamus
 Located inferior to the thalamus and superior to
the brain stem
 It is interconnected to the cerebral cortex,
thalamus, and other parts of the brain stem
 It consists of a collection of many different
nuclei.
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The Supraoptic Nucleus
The Paraventricular Nucleus
The Preoptic Nucleus
The Ventromedial Nucleus
Hypothalamus
 The hypothalamus has many roles in regulating
homeostasis
 It senses the chemical and thermal qualities of the
blood
 It is involved in:
 Regulation of heart rate and arterial blood pressure;
 Control of movements and glandular secretions of the
stomach and intestines;
 Regulation of respiratory rate;
 Regulation of water and electrolyte balance; and
 Control of hunger and regulation of body weight.
Limbic System
 A diverse collection of closely associated cerebral
cortical regions
 Encircle the upper part of the brain stem lending is name,
limbus (refers to ring)
 The structures of the limbic system include:
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The hippocampus
The mammillary bodies of the diencephalon
The hypothalamus
The anterior nucleus of the thalamus
The amygdaloid body
Several gyri and fiber tracts (fornix) that have not yet been
specifically identified
Limbic System
 Controls the emotional aspects of behavior
 Connected to the cerebral cortex and brain stem
 Allows for perception and response to a wide variety of
stimuli
 Communicates with the prefrontal lobes to elicit a
relationship between feelings and thoughts.
 This explains why emotions sometimes override thoughts
and why reason can override emotion when an emotional
response would be inappropriate.
 Part of the system, the hippocampus and the
amygdaloid body are involved in memory
The Brain - Cerebellum
 Located inferior to the forebrain and posterior
to the brainstem
 Functions:
 Coordination of muscular activity
1) Skilled movements, posture, and balance
 Regulate muscle tone
 The cerebellum has no direct connections
with muscles
 It functions at an unconscious level
The Brain - Cerebellum
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Receives a variety of information
 Information about voluntary muscle activity from the motor
region of the cerebral cortex
 Sensory information from proprioceptors throughout the body
 Information from the visual and equilibrium pathways
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Integrates this information and determines how to
integrate the sensory information with the motor
functions to elicit a coordinated response
 Sends its coordination plan to the primary motor cortex
 The primary motor cortex then signals the muscles to elicit
the desired response
The Brain - Cerebellum
 Cortical Control of Voluntary Movement
 Pyramidal Tracts
 Direct pathways from the primary motor cortex to the
spinal cord, called Corticospinal tracts
 Control small groups of muscles that contract
independently of each other
 Extrapyramidal Tracts
 Indirect connections between the brain and spinal cord
 Includes all motor control pathways outside the pyramidal
system
 Control large groups of muscles that contract together to
maintain posture and balance
Pyramidal Tracts
 Axons of neurons in these tracts terminate
in the ventral horn of the spinal cord
 Called Upper Motor Neurons
 Axons of neurons in these tracts cross over
to the opposite side of the CNS in the area
of the medulla
 Called Medullary Pyramids
Pyramidal Tracts
 Lateral and Ventral Corticospinal Tracts
 Carry nerve impulses for skilled, voluntary
contraction of the skeletal muscles
 Large motor pathways that descend from
the cerebral motor cortex to the motor
neurons in the ventral horn of the spinal
cord
 The largest and most important motor tracts in
the body
Pyramidal Tracts
 The Lateral Corticospinal tracts cross over
in the region of the medulla, called the
medullary pyramids
 The Ventral Corticospinal tracts cross over
in the spinal cord
Pyramidal Tracts
 From the medulla, the corticospinal tracts
descend to the spinal cord level of the muscle
to be innervated
 Both lateral and ventral corticospinal tracts synapse
with either:
1) Interneurons, or
2) Motor neurons in the ventral horn of the spinal cord
 Interneurons synapse with lower motor
neurons that travel directly to the
neuromuscular junction of the skeletal muscle
the CNS wants to activate
Pyramidal Tracts
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The Corticospinal Tracts connect the left cerebral
motor cortex with the muscles on the right side of the
body and vice versa
For example:
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The brain has received and processed sensory information that
causes it to direct the biceps muscles to contract to lift a weight
The brain sends impulses down the corticospinal tracts to the
C5-C7 levels of the spinal cord to synapse with the appropriate
motor neurons
The nerve impulse is propogated along the ventral roots of the
brachial plexus, to the musculocutaneous nerve, which
innervates the biceps
The biceps muscle contracts to lift the weight
Extrapyramidal Tracts
 Motor control pathways outside of the
pyramidal system
 Indirect connections between the brain and
spinal cord
 Neurons in these tracts do NOT form
synapses with motor neurons
 Include two tracts
 Reticulospinal tracts
 Rubrospinal tracts
Extrapyramidal Tracts
 Reticulospinal Tracts
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The Lateral, Anterior, and Medial Reticulospinal tracts
are motor (efferent, descending)
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Descend from the reticular formation, which is located in the
pons and medulla
 Elicits involuntary motor responses
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Functions:
 Facilitate extensor motor neurons (promotes muscle tone)
 Facilitate visceral motor function, and
 Control unskilled movements
Extrapyramidal Tracts
 Rubrospinal tracts
 Motor (efferent, descending) tracts descending from the
red nucleus (rubro-) of the midbrain
 These tracts cross over in the brain stem
 Elicits involuntary motor responses
 Functions:
 Synapse with motor neurons that will transmit impulses to
the neuromuscular junction of the muscle that will contract
 Result in muscle contractions that maintain muscle tone in
the flexor muscles on the opposite side of the body
Functional Human Physiology
for the Exercise and Sport Sciences
The Nervous System: Sensory Systems
Jennifer L. Doherty, MS, ATC
Department of Health, Physical Education, and
Recreation
Florida International University
Sensory Receptors
 Specialized neuronal structures that detect
a specific form of energy in either the
internal or external environment
 Energy is detected by the dendritic end organs of
sensory (afferent) neurons
 This information is transmitted to the CNS
 Receptors may change one form of energy
to another
 For example, chemical to electrical at the NMJ
Types of Sensory Receptors
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Chemoreceptors
 Sensitive to chemical concentrations such as in smell and taste
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Nociceptors or pain receptors
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Thermoreceptors
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Sensitive to tissue damage
Sensitive to temperature, either to heat or cold
Mechanoreceptors
 Sensitive to changes in mechanical energy such as pressure or the
movement of fluids
1)
2)
3)
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Baroreceptors detect the blood pressure in certain arteries and veins.
Stretch receptors are sensitive to changes in the amount of inflation in the
lungs.
Proprioceptors are sensitive to changes in tension in the muscles, tendons,
and ligaments.
Photoreceptors
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Sensitive to light intensity and are found only in the eyes.
Sensory Transduction
 Sensory impulses are generated by receptors
 The energy of the stimulus is absorbed
 The energy is then transduced into an electrical signal
 Receptor potential
 A stimulus that exceeds the threshold intensity
 Graded potential
 The electrical signal that is produced when threshold is
reached
 Propagation of a nerve impulse
Sensation
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The awareness of a stimulus
Perception
 The brain’s interpretation of the sensory information provided by
the sensory receptors
 Since all nerve impulses are the same, the only differences
are:
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The type of receptor that was stimulated, and
The region of the brain to which the receptor is connected.
For example,
1) When heat receptors in the 2nd finger of the right hand are
stimulated by a lit match, the region of the brain corresponding to
that part of the body will perceive pain
2) If light receptors were transplanted to the region of the brain that
senses smell, then stimulation of the light receptors would result in
an odor being perceived
Sensory Adaptation
 Sensory adjustment that occurs when
receptors are continuously stimulated
 Sensory Coding
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Receptors respond to continuous stimulation by firing at slower
and slower rates
Eventually the receptors may fail to send any signal at all
The sense of smell is particularly subject to sensory
adaptation
For example
 When you are in a room with a strong odor you will notice
that soon you cannot smell the odor, or it is much reduced
 The smell receptors have adapted and are not stimulated
again until the stimulus changes
 Clothing against skin is another example
The Somatosensory System
 The Somatosensory Cortex
 Postcentral Gyrus of Cerebrum
1) Sensory homunculus
2) Somatic sensory and proprioception
The Somatosensory System
 Somatosensory Pathways
 Dorsal Column-Medial Lemniscus
1) Transmit sensory impulses from mechanoreceptors and
proprioceptors to the thalamus
2) Crosses over in the region of the medulla
 Spinothalamic Tract
1) Transmits sensory impulses from thermoreceptors and
nocioceptors to the thalamus after crossing to the other side
in the spinal cord
2) Crosses over in the spinal cord
Spinothalamic Tracts
 The Lateral and Anterior Spinothalamic
Tracts are sensory (afferent, ascending)
 Travel from the spinal cord to the thalamus
 Receive sensory input from the receptors
for:
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Pain (from free nerve endings)
Temperature (from Pacinian corpuscles)
Deep pressure (from Meissners corpuscles)
Touch (from End bulbs of Krause )
Spinothalamic Tracts
 Sensory information crosses to the opposite
side in the spinal cord
 The sensory information ascends to the
thalamus
 A synapse occurs with one of the thalamic nuclei
 The sensory information is sent from the
thalamus to sensory cortex of the cerebrum
 Located in the post central gyrus
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For example:
 A heat receptor (free nerve ending) located in the L3
dermatome on the anterior thigh is stimulated by the heating
pad you have put on the quadriceps muscle group of your sore
right thigh
 The impulse travels along the peripheral nerve through the
sensory neuron in the dorsal root ganglion and on to a synapse
with an internuncial neuron in the dorsal horn of segment L3
 From there the fiber carrying the next impulse crosses over to
the left side of the spinal cord to the lateral spinothalamic tract,
and ascends to the thalamus.
 Another synapse occurs in the thalamus and the next impulse is
sent to the sensory cortex of the cerebrum where the brain will
perform its integrative and decision making functions.
 A decision will be made whether to instruct the muscles of your
hands and arms to remove the heating pad because it is too hot
or leave it in place.
Pain Perception
 Mediated primarily through free nerve endings
 Sensitive to a variety of painful or noxious stimuli
 Changes in chemical composition of body fluids,
such as decreased pH or accumulation of
metabolic wastes can stimulate pain receptors.
 Adaptation to pain is practically non-existent
 Pain sensation can be triggered by a single stimulus and
is longer lasting than many other types of stimuli, such as
hot, cold, or smell
Pain Pathways
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Pain impulses are transmitted through the ascending pathways
of the spinal cord, primarily the lateral spinothalamic tracts to
the brain
 Nocioceptors (pain receptors) located in the skin
 When stimulated, send pain information along a first order
neuron
 First order neurons
 Deliver sensory impulses from the receptor to the dorsal horn of
the spinal cord where it synapses on a second order neuron
 Second order neruons
 Travel in the spinothalamic tract to the thalamus which relays
the information to the appropriate area of the primary
somatosensory cortex
Pain Pathways
 Within the brain most of the pain sensation
terminates in the reticular formation and are
processed by the thalamus, hypothalamus
and the cerebral cortex
 The brain, after evaluating the extent of the
pain, sends information back along a
designated motor tract to the muscles that
require contraction to move the limb away
from the source of pain
Visceral Pain
 Usually not very well localized
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It may feel as though it is coming from another part of the body
than from the organ actually affected
 Referred pain
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Results from common nerve pathways that bring sensory
information from skin or muscles of another part of the body in
addition to that of an organ.
For Example,
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Pain impulses from the heart are conducted along the same
neural pathways as pain from the left arm and shoulder
Thus, the brain interprets heart pain as the more familiar
shoulder and arm pain
Modulation of Pain Signals
 In cases of extreme pain, impulses are capable of
stimulating the release of biochemicals that can
block pain impulses
 Among these biochemicals are:
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Neuropeptides
Serotonin
Enkephalin
Endorphins
 These biochemicals can bind to pain receptors and
block the sensation of severe or acute pain
The Nervous System:
Autonomic and Motor Systems
Jennifer L. Doherty, MS, ATC
Department of Health, Physical Education, and
Recreation
Florida International University
The Autonomic Nervous System
 Peripheral Nervous System
 Somatic NS
 Autonomic NS
1) Sympathetic
2) Parasympathetic
 The involuntary part of the PNS
 Operates without conscious control
 Primary function is to maintain homeostasis
The Autonomic Nervous System
 Controls the following:
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Smooth muscle of the blood vessels;
Abdominal and thoracic viscera;
Certain glands; and
Cardiac muscle.
 Serves an important role in maintaining:
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Heart rate
Blood pressure
Breathing
Body temperature
The Autonomic Nervous System
 Dual Innervation of the ANS
 The sympathetic division of the ANS is
responsible for readying the body for
strenuous physical activity or emotional
stress
 Fight or Flight Response
 Prepares the body to deal with disturbances
to homeostasis (threatening situations)
Anatomy of the ANS
 The ANS consists of efferent pathways
 Each efferent pathway contains 2 neurons
that are arranged in series to each other
 Provides communication between the CNS
and the effector organ
Anatomy of the ANS
 Autonomic Ganglia
 Provide communication pathways via synapses between
neurons
 Preganglionic Neurons
 Travel from the CNS to the ganglia
1) Sympathetic chain ganglion,
2) Collateral ganglion, or
3) Parasympathetic ganglion
 Postganglionic Neurons
1) Neurons that travel from the ganglion to the effector
organ
Sympathetic Nervous System
Thoracolumbar Division
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Preganglionic Neurons
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Arises from the ventral roots of all thoracic spinal nerves
Arises from the ventral roots of lumbar spinal nerves 1-3
Originate in the Lateral Horn of the spinal cord
Cell bodies are located in the thoracic and upper lumbar regions
of the spinal cord
Short Myelinated Axons
Postganglionic Neurons
 Synpase with preganglionic neurons in the Sympathetic
Chains (Trunks)
 Long Unmyelinated Axons
Sympathetic Nervous System
 Sympathetic Chains (Trunks)
 Where preganglionic and postganglionic neurons
synapse in the Sympathetic NS
 Comprised of sympathetic nerves that are
connected to a string of nerve cell bodies
 Called the Sympathetic (Paravertebral) Chain
Ganglia
 These interconnected ganglia are located close
to the spinal cord
 Far away from the structures it innervates
Parasympathetic Nervous System
Craniosacral Division
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Preganglionic Neurons
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Arises from the cranial nerve nuclei in the brain stem
Arises from the ventral roots of sacral spinal cord
Those originating in the cranial nerve nuclei travel with axons of
cranial nerves and terminate in ganglia near the effector organ
Those originating in the sacral spinal cord synapse with other
parasympathetic preganglionic neurons to form pelvic nerves
that terminate near the effector organ
Long Myelinated Axons
Postganglionic Neurons
 Travel to the effector organ
 Short Unmyelinated Axons
Mixed Composition of ANS Nerves
 Both systems function utilizing two neurons that
communicate through a ganglion
 Preganglionic nerve fibers arise in the CNS
 Myelinated axon leaves the CNS as part of a cranial
nerve or spinal nerve
 Travels to an autonomic nervous system ganglion
 Preganglionic nerve fibers synapse with the
postganglionic nerve fibers in the ganglion
 Postganglionic nerve fibers travel to the
appropriate effector organ
Effects of the ANS
 The two divisions have opposite effects
on the organs and structures innervated
 Sympathetic Nervous System
 Acetylcholine = neurotransmitter at the synapse
with the ganglion
 Norepinephrine = neurotransmitter at the
synapse with the effector organ
 Parasympathetic Nervous System
 Acetylcholine = neurotransmitter at both
synapses
Effects of the ANS
 Cholinergic Neurons
 Adrenergic Neurons
 Release Acetylcholine

Cholinergic Receptors
 Nicotinic receptors
1) Excitatory
2) Opens Na+ and K+
channels
 Muscarinic receptors
1) Excitatory or Inhibitory
2) Uses G-proteins to open
specific ion channels
 Release
Norepinephrine

Adrenergic Receptors
 Alpha receptors
1) Excitatory
 Beta receptors
1) Excitatory or Inhibitory
Effects of the ANS
 The sympathetic division generally
produces a whole body response when
stimulated.
 The overall function of the sympathetic division is
the fight or flight response.
 The parasympathetic division generally
produces a single response at a specific
effector organ.
 The overall function of the parasympathetic
division is rest and repair.
Comparison: Somatic and Autonomic
Nervous Systems