Download Human Nervous System Lecture

Final Project
This final project represents one lecture in a series of lectures for a course on clinical pathology for
physical therapist assistant students. The lecture will be presented through Blackboard (an online course
management system). The student will self-direct the material, with some facilitation cues to open slides and web
links for additional information. The sections on neurological disorders will include specific web links for the
student to read more about each disorder. The web link for each disorder will be imbedded in the title of the
disorder. The lecture will consist of the purpose of the lecture, lesson objectives, lecture material, web links and
power point slides to compliment the lecture, specific assigned readings, a section on terminology and testing of that
terminology at the conclusion of the lecture. This testing will cover the definitions of terms used in the text. The
terms will be highlighted throughout the text in red. Multiple choice and short answer exams will be given
throughout the course to assess the student’s learning of the course material. Each lecture will consist of a clinical
case study, which the student will use to develop a physical therapy treatment plan.
Human Nervous System Lecture
Purpose
The purpose of this lecture is to provide an understanding of the workings of the human nervous system, its
relationship to movement, the effects of nervous system dysfunction on physical function, and the role of the PTA in
neurological rehabilitation, including neurological assessment tools and treatment techniques.
Objectives
Upon completion of this lecture, the student will be able to:
-describe the role of the human nervous system in maintaining homeostasis
-identify the principle parts of the brain and spinal cord
-classify the organs of the nervous system into central and peripheral divisions
-develop an architectural plan of the tracts of the spinal cord
-discuss the major effects of central nervous system damage on the motor system
-list the clinical symptoms of stroke, cerebral palsy, multiple sclerosis, and Parkinson's disease.
-describe the assessment tools used to assess the following: muscle tone, reflexes, and balance
-design a physical rehabilitation treatment plan for a neurologically impaired patient based on a clinical case study
-define terminology specific to the central nervous system
Introduction
Nervous tissue is highly sensitive to change, therefore the properties of the extracellular fluid environment
must be maintained within very specific homeostatic levels. Any change that occurs in homeostasis is automatically
met with resisting factors to maintain steady state conditions. For example, a rise in blood sugar levels produces an
increase in the thirst response in an attempt to dilute the concentration of sugar in the extracellular fluid. The ability
of the body to maintain homeostasis under conditions of change depends on a number of cooperating mechanisms
acting simultaneously or successively to maintain glucose concentration, temperature, and acid-base balance. These
physiological control systems function to keep the physical and chemical parameters of the body constant. One
control system is the neuroendocrine control system. During periods of stress, the neuroendocrine system responds
to protect the body against any threat to homeostasis produced by the stress. The immediate response to stress
produces stimulation of the sympathetic nervous system resulting in the release of catecholamines. These
catecholamines increase the body’s attention and arousal state as noted by an increase in heart and respiratory rates,
dilation of the pupils, dry mouth, moist hands and feet, and decreased gastrointestinal tract activity. This is referred
to as the fight or flight response. The glucocorticoid hormones produced by the endocrine system have an effect on
immune responses, blood glucose levels, protein synthesis, kidney function, and hematopoiesis (open Stress and
Adaptation slide).
Structure and Function of the Central Nervous System (CNS)
The CNS consists of the brain and spinal cord. The spinal cord is an oval shaped cylinder that lies within a
cavity extending from the foramen magnum to the level of first lumbar vertebra. The spinal cord performs two
specific functions. It acts as a conduction pathway for nerve fiber tracts traveling to and from the brain. It also
serves as the reflex center for all spinal reflexes (http://www.merck.com/pubs/mmanual_home/illus/60i1.htm). The
brain is divided on an embryological basis into five major regions. The telencephalon is the center for man’s
highest functions and is composed of the cerebral hemispheres and the basal ganglia. The outer surface of the
hemispheres (cerebral cortex) contains nerve cell bodies while the inner portion consists of white matter fiber tracts.
Functional areas of the cerebral cortex are concerned with all functions of the human body: sensory, motor, auditory,
visual, language, consciousness, emotions, and memory. The basal ganglia consist of several groups of nuclei
buried deep in the cerebral hemispheres. The nuclei are interconnected by nerve fibers (tracts) that receive input
from and provide output to other areas of the CNS. The basal ganglia play an important role in regulating habitual
or automatic motor functions as well as setting an appropriate level of muscle tone. For example, walking,
swimming, and maintaining posture, The diencephalon is a small area between the cerebral hemispheres and
consists of the thalamus and hypothalamus. The thalamus is the main relay center for sensory impulses while the
hypothalamus is a the vital area concerned with life preserving function such as temperature control, emotional
states, and control over the autonomic nervous system. The mesencephalon is also known as the midbrain for its
location between the diencephalon and the pons. The area houses the nuclei of 3 rd and 4th cranial nerves and the
nuclei of basal ganglia involved in muscle control. Many fiber tracts pass through the midbrain along the pathways
to and from the telencephalon. Embryologically the pons and cerebellum is one region however are two separate
structures. The pons lies between the midbrain and the medulla oblongata. It houses the nuclei of the 5th, 6th, and 7th
cranial nerves as well as various ascending and descending tracts. The pons also contains the pneumotaxic centers
that help regulate respiration. The cerebellum is the second largest structure of the brain and lies just under the
occipital lobe of the cerebral hemispheres. Nerve fibers pass back and forth between the cerebellum and pons all
having to do with the control of skeletal muscles. The cerebellum works with the cerebral cortex to produce skilled
movements, it helps control posture and maintain balance. The fifth region of the brain is the medulla oblongata.
This region is continuous with the spinal cord at the foramen magnum. The medulla contains ascending and
descending fiber tracts, nuclei of the 8th through 12th cranial nerves, and a network of matter called the reticular
formation. Located in the reticular formation are the nuclei for the cardiac, respiratory, and vasomotor control
centers. Explore the nervous system by clicking the following link:
http://faculty.washington.edu/chudler/nsdivide.html
Conduction Pathways in the Spinal Cord
Tracts are both structural and functional organizations of axonal nerve fibers. Structurally, tracts are
organized in that all the axons of the tract originate from nerve cell bodies located in the same area of the CNS and
terminate in a single structure somewhere else in the CNS. For example, the fibers of the spinothalamic tract all
originate from cell bodies in one specific area of the spinal cord and terminate in the thalamus. Functionally, all the
axons of tracts serve the same function. Again, using the spinothalamic tract as an example, all the fibers of the tract
contain sensory information transmitting impulses that produce the sensations of touch, pain, and temperature.
Ascending tracts carry sensory information from the spinal cord to the brain. Descending tracts conduct motor
impulses from the brain to the spinal cord. The tracts are divided into four major sensory tracts and five major
motor tracts. Below is a listing of the major tracts of the CNS. A complete overview of the spinal cord, tracts, and
reflexes can be found at http://thalamus.wust.edu/course/spinal.html.
Major Ascending Sensory Pathways
Posterior Column pathway
Carries fine touch, pressure, vibration & proprioception information
First-order sensory neurons (s.c.) synapse in the nuclei gracilis & cuneatus (m.o.)
Second-order neurons cross-over in the medulla oblongata go to the thalamus
Third-order neurons (thalamus) projection to the primary sensory cortex
Lateral Spinothalamic pathway
Carries crude touch, pressure, pain & temperature information
First-order sensory neurons synapse with interneurons in spinal cord
Second-order interneurons cross-over in the spinal cord & go to the thalamus
Third-order neurons (thalamus) projection to the primary sensory cortex
Anterior Spinothalamic pathway
Carries information about position of skeletal muscle, tendons & joints
First-order sensory neurons synapse with interneurons in spinal cord
Second-order interneurons traveling in the posterior tract cross-over in the spinal cord & go to the
cerebellum
Second-order interneurons traveling in the anterior tract do not cross-over, they go directly to the cerebellum
* There are no third-order neurons
Major Descending Motor Pathways
From cerebral cortex, brainstem, cerebellum to effector
Pyramidal system
conscious control of skeletal muscles
Corticobulbar tracts - neurons descend through cranial nerves 3-7, 9, 11, 12
Control muscles in the eye, jaw, face & neck
Corticospinal tracts - located in anterior & lateral columns
Control muscles below neck level
85% of the neurons cross-over in the medulla oblongata, travel down the spinal cord & then synapse
with a motor neuron
15% of the neurons travel down the spinal cord & then cross-over before synapsing with the motor
neuron
Medial pathway
subconscious control of trunk & proximal limb muscles
Reticulospinal, vestibulospinal, & tectospinal tracts located in anterior columns
Only motor neurons in tectospinal tracts show cross-over
Lateral pathway
subconscious control of distal limb muscles
Rubrospinal tracts located in lateral columns
Cross-over in mesencephalon
The Movement Model
The efficiency of the motor system depends on the interactive functioning of the nervous and muscular
systems. All movement involves the higher-order functions of the brain including the premotor cortex and the
motor cortex. The thalamus provides continuous sensory feedback from the muscles and the cerebellum adjusts
errors in timing or sequencing. The basal ganglia provide the proximal support required for movement and stretch
reflexes in the joints and muscles provide the appropriate muscle tone. The vestibular system inputs maintain stable
postural support for movement. Every motor function involves parallel processing and interactive communication
between all parts of the neuromuscular system.
The Movement Model depicts the neural and muscular interactions that contribute to motor control and
physical motion. These interactions produce the skill, grace, and temporal smoothness of human movement (open
Movement Model slide).
Disorders of Motor Function
Damage to the nervous system resulting from lesions in the voluntary motor pathways may cause
a range of skeletal muscle dysfunctions including muscle weakness or paralysis, changes in muscle tone,
and disruption of spinal reflexes. The axons of upper motor neurons (UMN) in the motor cortex travel
down through the brain to the medulla. At the medulla, the fibers cross the midline to form the pyramids
and become the lateral corticospinal tract to the spinal cord. Upper motor neurons carry motor
information via the corticospinal tract to lower motor neurons located in the anterior horn of the spinal
cord.
Signs of upper motor neuron lesions include weakness, hyperreflexia, and increased tone. The
hyperreflexia and increased tone seen with corticospinal lesions appears to be caused by damage to pathways that
travel in close association with the corticospinal tract rather than directly by damage to the corticospinal tract itself.
With acute upper motor neuron lesions there is often flaccid paralysis with decreased tone and decreased reflexes.
Over time (hours to weeks), increased tone and hyperreflexia usually develop. Increased tone can occur in upper
motor neuron lesions, but can also occur in basal ganglia dysfunction. In addition, slow or awkward fine finger
movements or toe tapping in the absence of weakness can signify a subtle abnormality of the corticospinal
pathways, but can also occur in lesions of the cerebellum or basal ganglia. Signs of lower motor neuron lesions
include weakness, atrophy, fasciculations, and hyporeflexia (reduced reflexes). See table 1 for comparison of UMN
and LMN lesions.
Table 1: Signs of Upper Motor Neuron (UMN) and Lower Motor Neuron (LMN) Lesions
Sign
Weakness
Atrophy
Fasciculations
Reflexes
Tone
*Mild atrophy may develop due to disuse.
UMN Lesions
Yes
No*
No
Increased
Increased
LMN Lesions
Yes
Yes
Yes
Decreased
Decreased
Symptoms of Neurological Disorders
As the nervous system has varied and complex functions, the symptoms of neurological damage
affecting the motor system can be as diverse. Although some symptoms are common among disorders,
each pathology presents with its own clinical symptoms. The Nervous System Disorders slide introduces
several major categories of disorders. Some of these disorders will be discussed in the section that follows.
Cerebral Vascular Accident (CVA/Stroke) http://www.stroke.org/about.cfm
A CVA, more commonly known as stroke, causes permanent damage to brain tissue often resulting in long
term motor and/or sensory impairment. A stroke can be the result of an occlusion of an artery in the brain or a
hemorrhage due to a rupture in the brain’s blood supply. When the blood is blocked (occluded) and cannot get to
an area of the brain or there is extensive bleeding in an area of the brain, the brain cells in that region become
damaged from a lack of oxygen. This is referred to as ischemia.
Either a thrombus or embolus can occlude an artery in the brain. A thrombus is an arteriosclerotic plaque
that forms in a cerebral artery and blocks the flow of blood. Most often a thrombus forms in the middle cerebral
artery where it stays and causes an occlusion of the blood supply. An embolus is generally a piece of plaque or a
blood clot that travels through the bloodstream to the cerebral arteries from another part of the body. An embolus
commonly originates in the coronary or carotid arteries, travels through the cerebral blood supply, and there
occludes one of the cerebral arteries.
The major risk factors for a stroke are hypertension, diabetes, smoking, obesity, high cholesterol, and
coronary heart disease (CAD). Although strokes are more common among the elderly, they can occur at any age.
Approximately two thirds of all strokes result in some long-term disability. Rehabilitation includes long-term
medication to thin the blood and reduce the recurrence of a stroke as well as physical therapy to restore functional
abilities.
The resulting physical, sensory, and /or cognitive impairments of a stroke depend on the area of the brain
affected by the stroke and the extent of damage tot hat area. In general certain characteristics of a stroke are
common to specific areas of the brain.
Right Cerebral Hemisphere
weakness/paralysis/spasticity of left side of body
left hemianopsia
left side neglect
emotional lability
decreased attention span
memory deficits
impulsive behaviors
Left cerebral Hemisphere
weakness/paralysis/spasticity of right side of body
right hemianopsia
aphasia
dysphagia
motor apraxia
decreased processing of information
increased frustration
Brainstem
hemiplegia or quadriplegia
Decreased or loss of consciousness
Unstable vital signs
Inability to speak
Cerebellum
decreased balance and coordination
decreased ability for postural alignment
ataxia
nystagmus
Parkinson's Disease (PD) http://www.apdaparkinson.com/
Parkinson’s disease is a degenerative disorder of the basal ganglia that affects motor control and
movement. It is a slowly progressing, non-fatal disease with no known cause and no know cure. PD is the result of
a loss of dopamine producing neurons in the substantia nigra. Dopamine is a neurotransmitter substance that sends
impulses to the striatum (caudate nucleus and putamen) in order to produce smooth muscle activity. Acetylcholine
(AcH), another neurotransmitter, is also found in the striatum. The effect of AcH are exaggerated when dopamine
levels are low. The imbalance between AcH and dopamine increases the symptoms of PD.
Treatment for PD has been concentrated in the area of drug therapy to reduce the symptoms of the disease
and help slow its progression. The most common drug provided is Levodopa or L-dopa (also known as Sinemet), a
chemical substance which brain cells use to make dopamine. Although drug therapy has some benefit in reducing
the symptoms of PD, they often have side effects that can cause additional debilitation such as memory loss,
confusion, and dyskinesia.
Over one million people in the United States are presently diagnosed with PD. Generally the signs of PD
develop between the ages of 40 and 70 years although recently there have been several diagnosed cases in people
younger the 40 years. The most well known person in this group is the actor, Michael J. Fox (see Symptoms of
Parkinson’s Disease slide).
*The lecture on disorders will continue to include cerebral palsy, multiple sclerosis, and peripheral neuropathies.
However, to save time and space for this final project, the lecture will continue from here to include clinical tools
and a clinical case study.
Clinical Assessment Tools
A problem-oriented approach to treatment of any neurological disability is a key element to rehabilitation.
Treatment should be based on methods that provide the best combinations of available treatment alternatives to meet
individual needs and differences. Because many different areas of the CNS may be affected, a thorough assessment
must be performed to determine the extent of neurological and functional involvement. Data can be obtained
through the patient’s history, systems review, and relevant assessment tests and measures. The severity of problems,
state of disease (acute, subacute, or chronic), age, and other factors must all be taken into account when structuring
the assessment. The following list includes specific areas of assessment and relative tests that can be used to
examine function in neurologically impaired patients. An overview of assessment tools can be found at
http://www.greatseminarsandbooks.com/TOC/pw_toc.htm Direct links to specific tests can be found below.
Neurological Assessment Tests and Tools
-cognitive function: assess memory, attention, concentration, problem solving. Mini Mental Status Exam (MMSE)
http://www.levymd.com/html/mini_mental_status_examination.htm
https://www.highmark.com/health/professionals/gerbinder.html click on Dementia Management: AMMSE
-sensory integrity: superficial and deep sensation, pain, temperature, proprioception, stereognosis. Full sensory test
-pain: determine pain behavior and reaction during specific movements and provoking stimuli. VAS
https://www.highmark.com/health/professionals/gerbinder.html (click on Pain Scales)
-range of motion: functional ROM and specific deficits. Goniometry
-motor function: muscle tone, muscle strength, reflexes (normal/abnormal i.e. Babinski). Ashworth Scale, MMT
http://www.wemove.org/spa_pal.html#a_tis
-gait, locomotion: gait parameter and characteristics, stability, and safety. The Get Up & Go Test
https://www.highmark.com/health/professionals/gerbinder.html click on Tools
http://www.vard.org/jour/00/37/1/wall371.htm
-balance: static and dynamic, reactive, anticipatory, and synergistic strategies. Berg Balance Scale, FR Test
https://www.highmark.com/health/professionals/gerbinder.html click on Tools
http://www.chcr.brown.edu/Balance.htm
-aerobic capacity, endurance: resting vital signs before, during, after activity, perceived exertion. RPE
http://www.vqfitpros.com/borg.html
-functional activities: bed mobility, transfers, ambulation with/without device.
Case Study
Mr. R is a 68-year-old man with a 7-year history of Parkinson’s disease. He now falls two to three times a
day, has difficulty eating and weakness in his right hand. On assessment he has moderate rigidity in all extremities;
right side worse than left, and most noted in the wrist, forearm, and hand. Shoulder flexion and abduction lack 15
degrees bilaterally. Joint range of motion is within functional limits with the exception of a 10-degree knee flexion
contracture on the right. Muscle strength is grossly 4 throughout all muscle groups. Sensation is within normal limits
throughout. Static and dynamic sitting balance is good, standing balance is fair.
The patient sits with a posterior pelvic tilt, rounded shoulders, and forward head. On coming to stand
position, he does not lean forward as he stands. He momentarily loses his balance upon rising from a chair. When
pushed gently on the sternum, he takes one or two steps backward. When pushed from behind, he takes several
steps forward to recover his balance. He was unable to maintain his balance when trying to catch a large ball
thrown toward his side. His gait pattern exhibits a shortened step, flat foot contact, festination, difficulty with
starting and stopping and an absence of arm swing or trunk rotation. His gait is slow and he is unable to increase his
speed measurably in a 25-foot walk. The patient is on l-dopa/carbidopa and deprenyl.
The patient has always been active and enjoys golf, swimming and skiing. He was able to ski until last
winter. At that time, he found that he could not get up after a fall. He also no longer swims because he has difficulty
coordinating his breathing with the swim strokes. He does not play golf because he is so slow in walking and it takes
him too long to complete the course. He would like to return to some of these activities, including golf once a week.
Based on the information provided in the case study, develop a physical therapy rehabilitation plan for this
patient. The plan must include a list of the physical and functional problems, short and long term goals, outline
treatment activities, length and duration of the treatment plan, and the rationale for the activities selected.