Functional Human Physiology for the Exercise and Sport Sciences The Nervous System

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Functional Human Physiologyfor the Exercise and
Sport Sciences The Nervous System

• Jennifer L. Doherty, MS, ATC
• Department of Health, Physical Education, and
  Recreation
• Florida International University

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Overview of the Nervous System

• Two major anatomical divisions
• The central nervous system (CNS)
• Brain
• Spinal Cord
• The peripheral nervous system (PNS)
• Afferent Division
• Efferent Division
• Somatic Nervous System
• Autonomic Nervous System

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Overview of the Nervous System

• Functional Divisions of the PNS
• Afferent Sensory
• Somatic sensory
• Visceral sensory
• Efferent Motor
• Somatic motor
• Visceral motor

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Overview of the Nervous System

• Divisions of the PNS according to type of control
• Somatic nervous system
• Voluntary
• Autonomic nervous system
• Involuntary
• Further divided according to the overall effect
  on the organs
• Sympathetic division Fight or Flight
• Parasympathetic division Rest and Repair

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Functions of the Nervous System

• Collecting information
• Peripheral Nervous System
• 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
• Motor or efferent output

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General Anatomy of the CNS

• Glial Cells
• Supporting cells for neurons in the CNS
• 5 types
• 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

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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
• Dura Mater
• Arachnoid mater
• Pia Mater

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General Anatomy of the CNS

• Cerebrospinal Fluid (CSF)
• 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

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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

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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
• sensitive to changes inside or outside of the
  body
• Nerve impulses travel toward the CNS

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General Anatomy of the CNS

• Interneurons
• Also call Association / Internuncial neurons
• Function link between afferent and efferent
  neurons
• 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

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General Anatomy of the CNS

• Gray Matter
• Areas of the CNS consisting primarily of
• Cell bodies
• Dendrites
• Axon terminals
• Area where synaptic transmission and neural
  integration occurs
• White Matter
• Areas in the CNS consisting primarily of
  myelinated axons
• Function to rapidly transmit action potentials
  over relatively long distances

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The Spinal Cord

• Cylinder of nervous tissue
• Continuous with the lower portion of the brain
• Branches into 31 pairs of spinal nerves
• Cervical nerves (C1 C8)
• Thoracic nerves (T1 T12)
• Lumbar nerves (L1 L5)
• Sacral nerves (S1 S5)
• Coccygeal nerve (C0)

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The Spinal Cord

• Gray matter concentrated in the butterfly-shaped
  interior region of the spinal cord
• Ventral Horn
• Contains Efferent Neurons
• Interneurons
• Cell bodies
• Dendrite
• Dorsal Horn
• Contains Afferent Neurons
• Axon terminals

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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

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The Spinal Cord

• Spinal Nerves
• Contain both afferent and efferent axons
• Joining of the dorsal root and the ventral root
• Called Mixed Nerves

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Spinal Cord

• White Matter consists of Tracts providing
  communication between
• Different levels of the spinal cord, or
• 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

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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

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The Brain Cerebrum (Forebrain)

• Cerebral Cortex
• Thin, highly convoluted layer gray matter
• Responsible for conscious initiation of voluntary
  movements
• Regions of the Cerebral Cortex
• Frontal Lobes
• Parietal Lobes
• Temporal Lobes
• Occipital Lobe

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The Brain Cerebrum (Forebrain) Areas of
Specialized Function

• Primary Somatosensory Cortex
• Involved in processing somatic sensory
  information associated with
• Somesthetic sensations such as touch, temperature
  and pain perception
• Proprioception which is the awareness of muscle
  tension, joint position, and limb position
• Primary Motor Cortex
• Initiates voluntary movement

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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
• 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.

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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
• The caudate nucleus
• The putamen
• The globus pallidus
• Important role in modifying movement

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The Brain - Basal Nuclei

• Normally inhibit motor function thereby
  controlling muscle activity
• Receive input from
• The entire cerebral cortex
• Other subcortical nuclei
• 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

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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
• 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

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The Brain Diencephalon (Forebrain)

• The diencephalon includes two structures
• Thalamus
• Hypothalamus

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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

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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

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Thalamus

• 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

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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.
• The Supraoptic Nucleus
• The Paraventricular Nucleus
• The Preoptic Nucleus
• The Ventromedial Nucleus

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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.
  

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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
• 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

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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

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The Brain - Cerebellum

• Located inferior to the forebrain and posterior
  to the brainstem
• Functions
• Coordination of muscular activity
• Skilled movements, posture, and balance
• Regulate muscle tone
• The cerebellum has no direct connections with
  muscles
• It functions at an unconscious level

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The Brain - Cerebellum

• 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
• 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

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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

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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

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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

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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

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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
• Interneurons, or
• 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

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Pyramidal Tracts

• The Corticospinal Tracts connect the left
  cerebral motor cortex with the muscles on the
  right side of the body and vice versa
• For example
• 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

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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

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Extrapyramidal Tracts

• Reticulospinal Tracts
• The Lateral, Anterior, and Medial Reticulospinal
  tracts are motor (efferent, descending)
• Descend from the reticular formation, which is
  located in the pons and medulla
• Elicits involuntary motor responses
• Functions
• Facilitate extensor motor neurons (promotes
  muscle tone)
• Facilitate visceral motor function, and
• Control unskilled movements

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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

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Functional Human Physiologyfor 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

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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

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Types of Sensory Receptors

• Chemoreceptors
• Sensitive to chemical concentrations such as in
  smell and taste
• Nociceptors or pain receptors
• Sensitive to tissue damage
• Thermoreceptors
• Sensitive to temperature, either to heat or cold
• Mechanoreceptors
• Sensitive to changes in mechanical energy such as
  pressure or the movement of fluids
• 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
• Sensitive to light intensity and are found only
  in the eyes.

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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

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Sensation

• The awareness of a stimulus
• Perception
• The brains interpretation of the sensory
  information provided by the sensory receptors
• Since all nerve impulses are the same, the only
  differences are
• The type of receptor that was stimulated, and
• The region of the brain to which the receptor is
  connected.
• For example,
• 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
• 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

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Sensory Adaptation

• Sensory adjustment that occurs when receptors are
  continuously stimulated
• Sensory Coding
• 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

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The Somatosensory System

• The Somatosensory Cortex
• Postcentral Gyrus of Cerebrum
• Sensory homunculus
• Somatic sensory and proprioception

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The Somatosensory System

• Somatosensory Pathways
• Dorsal Column-Medial Lemniscus
• Transmit sensory impulses from mechanoreceptors
  and proprioceptors to the thalamus
• Crosses over in the region of the medulla
• Spinothalamic Tract
• Transmits sensory impulses from thermoreceptors
  and nocioceptors to the thalamus after crossing
  to the other side in the spinal cord
• Crosses over in the spinal cord

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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
• Pain (from free nerve endings)
• Temperature (from Pacinian corpuscles)
• Deep pressure (from Meissners corpuscles)
• Touch (from End bulbs of Krause )

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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.

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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

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Pain Pathways

• 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

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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

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Visceral Pain

• Usually not very well localized
• It may feel as though it is coming from another
  part of the body than from the organ actually
  affected
• Referred pain
• 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,
• 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

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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
• Neuropeptides
• Serotonin
• Enkephalin
• Endorphins
• These biochemicals can bind to pain receptors and
  block the sensation of severe or acute pain

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The Nervous SystemAutonomic and Motor Systems

• Jennifer L. Doherty, MS, ATC
• Department of Health, Physical Education, and
  Recreation
• Florida International University

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The Autonomic Nervous System

• Peripheral Nervous System
• Somatic NS
• Autonomic NS
• Sympathetic
• Parasympathetic
• The involuntary part of the PNS
• Operates without conscious control
• Primary function is to maintain homeostasis

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The Autonomic Nervous System

• Controls the following
• Smooth muscle of the blood vessels
• Abdominal and thoracic viscera
• Certain glands and
• Cardiac muscle.
• Serves an important role in maintaining
• Heart rate
• Blood pressure
• Breathing
• Body temperature

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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)

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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

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Anatomy of the ANS

• Autonomic Ganglia
• Provide communication pathways via synapses
  between neurons
• Preganglionic Neurons
• Travel from the CNS to the ganglia
• Sympathetic chain ganglion,
• Collateral ganglion, or
• Parasympathetic ganglion
• Postganglionic Neurons
• Neurons that travel from the ganglion to the
  effector organ

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Sympathetic Nervous System

• Thoracolumbar Division
• Arises from the ventral roots of all thoracic
  spinal nerves
• Arises from the ventral roots of lumbar spinal
  nerves 1-3
• Preganglionic Neurons
• 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

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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

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Parasympathetic Nervous System

• Craniosacral Division
• Arises from the cranial nerve nuclei in the brain
  stem
• Arises from the ventral roots of sacral spinal
  cord
• Preganglionic Neurons
• 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

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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

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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

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Effects of the ANS

• Cholinergic Neurons
• Release Acetylcholine
• Cholinergic Receptors
• Nicotinic receptors
• Excitatory
• Opens Na and K channels
• Muscarinic receptors
• Excitatory or Inhibitory
• Uses G-proteins to open specific ion channels

• Adrenergic Neurons
• Release Norepinephrine
• Adrenergic Receptors
• Alpha receptors
• Excitatory
• Beta receptors
• Excitatory or Inhibitory

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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.

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Comparison Somatic and Autonomic Nervous Systems