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52-year-old female experiencing progressive muscle weakness genetically…
52-year-old female experiencing progressive muscle weakness genetically tested positive for ALS
Physiology
Neuron Structures
Gray matter (horns)
Dendrites:
receives signals and sends them to cell body
Unmyelinates axons:
carries impulses away from cell body slowly due to no fatty layer (myelin sheath) insulating the axon; continuous conduction
Cell bodies:
contains nucleus and majority of organelles
White matter (tracts)
Myelinated axons:
quickly carries impulses away from cell body and axon is insulated by myelin sheath keeping electrical signal inside; saltatory conduction
Neurons in Ascending & Descending Tracts
Ascending Tract:
sensory tracts with 3 neurons. Information collected from receptors travels UP to the brain to be processed
3rd order neuron: located in the thalamus that connects with cerebral cortex
2nd order neuron: interneuron in the spinal cords dorsal horn
1st order neuron: contains receptors and transports information to spinal cord
Descending Tract:
motor tracts with 2 neurons. Brain or brainstem provide direction for skeletal muscle
Upper motor neuron: brain or brainstem
Lower motor neuron: synapses with muscle
Spinal Cord & Neurons
Ventral gray horn:
anterior gray matter that contains cell bodies of motor neurons that travel to skeletal muscles
Motor Neurons:
carries impulses away from CNS to effectors
Dorsal root:
posterior side of spinal cord where sensory neurons enter
Sensory Neurons:
transmits impulses toward CNS from sensory receptors
White matter funiculi:
superficial layer of spinal cord containing myelinated axons
Lateral gray horn:
lateral gray matter that contains automatic motor neurons
Visceral Autonomic Motor Neurons:
carries impulses away from CNS to effectors (involuntary; smooth and cardiac muscle)
Ventral root:
anterior side of spinal cord where motor neurons exit and travel to muscles and glands
Somatic Motor Neurons:
carries impulses away from CNS to effectors (voluntary; skeletal muscle)
Dorsal root ganglion:
Enlargement on the dorsal root
Sensory Neurons:
transmits impulses toward CNS from sensory receptors
Central canal:
Contains Cerebrospinal fluid
Dorsal median sulcus:
Narrow groove on the posterior side
Dorsal gray horn:
posterior gray matter that contains cell bodies of interneurons
Interneurons:
impulses within the CNS that predict motor function
Ventral median fissure:
Wide groove on the anterior side
Process of Movement
Precentral gyrus:
Contains neurons that initiate muscle contraction. Consists of the motor humunculus which gives insight on how many different motor neurons travel to a specific area on the body
Cerebellum:
smooths out muscle movement. Collects motor information and compares it to the sensory information; what should be happening vs. what is happening. Makes necessary corrections
Basal Nuclei:
regulates muscle movement by preventing things like tremors; unwanted movement. Made of gray matter nuclei
Descending Tract:
The Cerebellum and basal nuclei both located in the brain, receive information that they later send to the spinal cord. During intoxication, Cerebellum becomes less functional and as a result movements become less smooth and coordinated (i.e. can't walk in a straight line, can't follow light with eyes, can't locate nose). In someone with Parkinson's disease or Tourette's, the basal nuclei is blocked from regulating muscle movement which results in tremors or random outbursts
Cerebrum
Occipital lobe:
Processes visual information and memories
Parietal lobe:
Responsible for general sensory functions
Longitudinal fissure:
Separates the left and right hemisphere
Frontal lobe:
Responsible for motor functions and personality
Central sulcus:
Indention separating the parietal and frontal lobe
Temporal lobe:
Processes hearing and smell
Postcentral gyrus:
Primary sensory area responsible for regulating sensory functions
Insula:
Interpretes taste
Precentral gyrus:
Primary motor area responsible for regulating motor functions
Cerebellum:
Regulates motor movements & helps maintain equilibrium
Arbor vitae:
Provides sensory information
Vermis:
Regulates posture and receives somatic sensory information
Examples of Ascending & Descending Tracts
Ascending
Spinothalamic Tract:
"Spino-": Spinal Cord, "thalamic": Thalamus, "Tract": White matter
2nd -
Dorsal gray horn
: gray matter posterior to spinal cord containing cell bodies of interneurons
3rd -
Thalamus
: Sorts info. to the right parts of the cerebrum
1st - Dorsal root ganglion:
Dorsal root enlargement
Spinocerebellar Tract:
"Spino-": Spinal cord, "cerebellar": Cerebellum, "Tract": White matter
1st -
Dorsal root ganglion:
Dorsal root enlargement
2nd -
Cerebellum:
regulates motor movement & helps with equilibrium
Descending
Corticospinal Tract: "Cortico-": Cerebral Cortex, "Spinal": Spinal cord, "Tract": White matter. Direct motor tract: cerebral cortex sends direction of movement
Upper -
Precentral gyrus:
anterior to central sulcus. Located in primary motor area and regulates motor functions
Lower -
Ventral gray horn:
anterior gray matter that contains cell bodies of motor neurons that travel to skeletal muscles
Vestibulospinal Tract:
"Vestibulo-": Vestibule (Equilibrium; Semicircular canals, saccule, utricle), "Spinal": Spinal cord, "Tract": White matter. Indirect motor tract: directions come from the brainstem rather than the brain
Upper -
Brainstem:
Contains midbrain, pons, and medulla oblongata. Controls basic body functions
Lower -
Ventral gray horn:
anterior gray matter that contains cell bodies of motor neurons that travel to skeletal muscles
Anatomy
Neuron Structures
Gray matter (horns)
Dendrites
Unmyelinated axons
Cell bodies
White matter (tracts)
Myelinated axons
Neurons in Ascending & Descending Tracts
Ascending Tract
2nd order neuron
1st order neuron
3rd order neuron
Descending Tract
Upper motor neuron
Lower motor neuron
Spinal Cord & Neurons
Ventral gray horn
Motor Neurons
Dorsal root
Sensory Neurons
Lateral gray horn
Visceral Autonomic Motor Neurons
Ventral root
Somatic Motor Neurons
Dorsal root ganglion
Sensory Neurons
Central canal
Dorsal gray horn
Interneurons
Dorsal median sulcus
Ventral median fissure
White matter funiculi
Process of Movement
Precentral gyrus
Cerebellum
Basal nuclei
Descending Tract
Cerebrum
Occipital lobe
Parietal lobe
Longitudinal fissure
Frontal lobe
Central sulcus
Temporal lobe
Postcentral gyrus
Insula
Precentral gyrus
Cerebellum
Vermis
Arbor Vitae
Examples of Ascending & Descending Tracts
Ascending
Spinothalamic Tract
2nd order neuron - Dorsal gray horn
3rd order neuron - Thalamus
1st order neuron - Dorsal root ganglion
Spinocerebellar Tract
1st order neuron - Dorsal root ganglion
2nd order neuron - Cerebellum
Descending
Corticospinal Tract
Upper motor neuron - Precentral gyrus
Lower motor neuron - Ventral gray horn
Vestibulospinal Tract
Upper motor neuron - Brainstem
Lower motor neuron - Ventral gray horn
Downstream Effects
Nervous System:
detects and responds to stimuli
Complication:
(i.e. brain, spinal cord) speech impairments and dementia may arise
Treatment:
Speech therapy. Rehabilitation and Occupational Therapy
Digestive System:
breaks down food
Complication:
(i.e. mouth, esophagus) lack of nutrition and hydration may occur due to inability to swallow . Pneumonia may also occur due to build up of food, liquid, and saliva in lungs
Treatment:
feeding tube and possible visit to a gastroenterologist
Muscular System:
Aids in movement and heat production
Complication:
(i.e. Skeletal muscle) Muscle twitching, muscle weakness, muscle cramps, inability to walk effortlessly (tripping or falling more frequently)
Treatment:
Anti-flammatory medication assists with muscle spasms and cramping
Immune System/Lymphatic System:
Protects against pathogens
Complication:
immune response affects motor neurons in the spinal cord. ALS can form macrophages which disposes of healthy neurons
Treatment:
Body's production of "resolvin D1" produced by omega-3 fatty acid DHA which blocks inflammatory proteins made by the macrophages
Respiratory System:
regulates gas exchange
Complication:
(i.e. Lungs, Diaphragm) as muscles continue to weaken breathing gets harder and airways may close. Respiratory failure leading to death may occur
Treatment:
Breathing device that aids in keeping airways open and pressure regulated. Another option is is for a patient to get a tracheostomy. Respiratory therapist
Upstream Causes
Indirect cause
Hereditary disorder also seen in brother and father. Age, sex, race, genetics, and environmental factors all possible factors leading to development
Direct cause
Motor neurons aren't able to function properly when regulating voluntary muscle movement, ultimately leading to loss of muscle control due to abnormal protein buildup in nerve cells located in the hypoglossal nuclei and ventral horns being targeted. Descending tract