PATHO15

Neuromuscular unit containing motor neurons

Myoneural junction

Muscle fibers

Spinal cord

Descending pathways from the brain stem circuits

Components of the Neuromuscular System

Extensors

Muscles that increase the angle of a joint

e) quads

Flexors

Muscles that decrease the angle of a joint

e)hamstrings

Agonists

Promote movement

Antagonists

Oppose movement

Synergists

Assist the agonist muscles by stabilizing a joint or contributing additional force to the movement

The Motor Unit

The motor unit consists of the motor neuron and the muscle fibers it innervates.

Upper motor neurons

• project from the motor cortex to the brain stem or spinal cord.

• Directly or indirectly innervate the lower motoneurons or contracting muscles.

• Motor unit is a motor neuron and all the muscle fibers it innervates.

motor

muscle strength

cerebellar motor function

rhythmic movement and steady posture

vestibular motor function

posture and balance

sensory motor function

position and sense

Neuromuscular Junction

• Serves as a synapse between a motor neuron and a skeletal muscle fiber.

• Consists of the axon terminals of a motor neuron and a specialized region of the muscle membrane called the end plate

• The transmission of impulses is mediated by the release of the neurotransmitter acetylcholine from the axon terminals.

• Acetylcholine binds to receptors in the end plate region of the muscle fiber surface to cause muscle contraction.

Motor Systems

Extrapyramidal System

Pyramidal Motor System

Pyramidal Motor System

• DIRECT

• Originates in the motor cortex

• Provides control of delicate muscle movement

• stroke cx issues among these systems; characterized by paralysis

Extrapyramidal System

• INDIRECT

• Originates in the basal ganglia

• Provides background for the more crude, supportive movement patterns

• Parkinsons disease would cx involuntary movement rigidity or immobility wo paralysis

Basal Ganglia

A group of deep, interrelated subcortical nuclei that play an essential role in control of movement

They receive indirect input from the cerebellum and from all sensory systems, including vision, and direct input from the motor cortex.

They function in the organization of inherited and highly learned and rather automatic movement programs.

They also are involved in cognitive and perception functions.

primary motor cortex

responsible for execution of a movement.

premotor cortex

generating a plan of movement.

supplemental motor cortex

rehearsing motor sequences of movement

Upper Motor Neuron Lesions

• Can involve the motor cortex, the internal capsule, or other brain structures through which the corticospinal or corticobulbar tracts descend, or the spinal cord

Lower Motor Neuron Lesions

Disrupt communication between the muscle and all neural input from spinal cord reflexes, including the stretch reflex, which maintains muscle tone

Muscular Atrophy

If a normally innervated muscle is not used for long periods, the muscle cells shrink in diameter, lose much of their contractile protein, and weaken.

Muscular Dystrophy

• Genetic disorders that produce progressive deterioration of skeletal muscles because of mixed muscle cell hypertrophy, atrophy, and necrosis. Most forms begin in childhood.

• involves atrophy

• primary tissue issue

• kids 2-3y/o

• imbalance of antagonist and agonist muscles in hips and shoulder first; scoliosis

Myasthenia Gravis

• Disorder of transmission at the neuromuscular junction that affects communication between the motorneuron and the innervated muscle cell.

• SS:

  • drooping eyelids, weak extremities, voice change, dysphagia, rapid fatigue, smooth forehead, drooping of mouth corners

• TX:

  • NONE

• DX: physical, blood test for acetylcholine

• CX:

  • Autoimmune disease caused by antibody-mediated loss of acetylcholine receptors in the neuromuscular junction

Peripheral Neuropathy

• Definition

  • Any primary disorder of the peripheral nerves

• Results

  • Muscle weakness, with or without atrophy and sensory changes

• Involvement

  • Can involve a single nerve (mononeuropathy) or multiple nerves (polyneuropathy)

  • myelin loss decrease nerve conduction

  • axon loss decreases amplitude of nerve conduction

Immune mechanisms (Guillain-Barré syndrome)

Toxic agents (arsenic polyneuropathy, lead polyneuropathy, alcoholic polyneuropathy)

Metabolic diseases (diabetes mellitus, uremia)

Causes of Polyneuropathies

Guillain-Barré syndrome

• acute polyneuropathy that follows systemic infection

  • e)myelinating or axon issue

• CAN NOT RECEIVE VACCINES

• SS:

  • parasthesia, weak extremities, cranial neuropathy

• loss of movement starts at bottom

• TX:

  • ventilation, immunoglobulin, nutrients

Cerebellum-associated movement disorders

• Types

  • Vestibulocerebellar ataxia

  • Decomposition of movement

  • Cerebellar tremor

• CX:

  • Congenital defect, vascular accident, or growing tumor, stroke, toxins

• Coordination of motor movement

• Tremor

• Tics

• Chorea

• Athetosis

• Ballismus

• Dystonia

• Dyskinesias

Types of Involuntary Movement Disorders

Parkinson Disease

• A degenerative disorder of basal ganglia function that results in variable combinations of tremor, rigidity, and bradykinesia

• affects movement, balance, control

• common in M 40-70

• 1-5 STAGES

• CX:

  • lack of dopamine < the ability to coordinate movement

  • acetylcholine active and cx imbalance of rest and excitement

• SS:

  • drooling, loss of all movement, decrease smell, rigidity, dementia, stooped posture, shuffling and short stride, forward tilt, tremors in leg and hands

• TX:

  • L-DOPA, neurosurgery, neurostimulation

• Clinical syndrome

  • Parkinsonism : cx by drug-induced psychotics or stroke

Amyotrophic Lateral Sclerosis (ALS)

• A devastating neurologic disorder that selectively affects motor function

• kills motor neurons

• Ages 40-70; 2-5 year life span

• SS:

  • inhibit speech, swallow, walk, breath

  • NO CURE

Multiple Sclerosis (MS)

• A demyelinating disease of the CNS

• Most common nontraumatic cause of neurologic disability among young and middle-aged adults; COMMON in F 20-50

• Autoimmune response as a result viral infection; genetically prone

• T cells didn’t leave CNS post infection in white matter of spinal cord

• NO CURE

• SS:

  • dysarthria, dysphagia, ataxia, weakness, parasthesia, incontinence, fatigue, moody, paresthesias, diarrhea,

Spinal Cord Injury (SCI)

• Definition

  • Damage to the neural elements of the spinal cord

• Causes

  • Motor vehicle crashes, falls, violence, and sporting activities

• Involvement

  • Most SCIs involve damage to the vertebral column and/or supporting ligaments as well as the spinal cord.

  • Commonly involve both sensory and motor function

• Types

  • Central cord syndrome

    Anterior cord syndrome

    Brown-Séquard syndrome

    Conus medullaris syndrome

Central cord syndrome

• narrowing or stenotic changes in the spinal canal; OLDER

  • E) arthritis, congenital stenosis

• location: gray or white matter

• motor function of upper extremities affected; possible lower

• bowel, bladder, and sexual function affected

• AFFECTS CHEST UP BODY MOTOR FUNCTION

Anterior cord syndrome

• damage of infarction to interior spinal arterial resulting in damage to interior 2/3 of cord

• loss of motor function provided by corticospinal tracts

• loss of pain and temperature sensation

• posterior 3rd of cord unaffected

• AFFECTS SENSORY AND MOTOR FUNCTION FROM NECK DOWN

Brown-Séquard syndrome

• damage to hemisection of posterior and anterior

• affect ipsilateral loss of volunteering motor function from the corticospinal tract

• loss of contralateral loss of pain and temperature sensation from lateral spinal thalamic tract for all levels located below the lesion

• AFFECTS ONE SIDE OF BODY MOTOR AND OTHER SIDE SENSORY

Conus medullaris syndrome

• damage to conus medullaris or sacral cord of the long bernaral roots of sacral canal

• SS:

  • facet bowel and bladder( no tone), altered sexual function, motor function in legs and feet impaired wo sensory impairment

monoplegia

a type of paralysis that affects a single limb, usually an arm, but can also affect a leg

hemiplegia

a condition that causes partial or complete paralysis on one side of the body, affecting the arm, leg, and sometimes the face:

diplegia

a condition that causes paralysis or weakness in symmetrical parts of the body, such as both arms or both legs

paraplegia

a chronic condition that results in the loss of motor or sensory function in the lower half of the body, including the legs, feet, and sometimes the abdomen.