Diseases of muscle and peripheral nerve: review of the CNS blood supply Flashcards
Cerebrum
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Frontal lobe
cognition, motor activity
Parietal lobe
sensory input
temporal lobe
memory storage
Occipital lobe
visual perception
hypothalamus
vital center for regulation of body temperature and blood circulation
Cerebellum
right and left hemispheres
equilibrium and coordination
brainstem
midbrain, pons, medulla
vital centers: respiration, heart rate, blood pressure
spinal cord
traversed by nearly all the nerves carrying information to and from the body.
cervical: arms, diaphragm (respiration)
thoracic: chest, abdomen
lumbo-sacral: legs, urinary blader, rectum reproductive organs.
Peripheral nervous system
crania (sensory and motor) nerves: eye muscles, ear, face, tongue, mouth and viscera
spinal (sensory and motor) nerves: limbs and trunk, skin, musculoskeletal and viscera.
meninges
fibrous tissue covering the brain
- dura: tough outer layer, separates cranial activity into compartments
- pia-arachnoid: thin inner layers containing many blood vessels
4 ventricular system
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- cerebrospinal fluid (CSF)
produced by choroid plexus, flows through the ventricles and is reabsorbed by special cells of the pia-arachnoid (arachnoid villi)
- Lateral ventricle with inter ventricular foramen
- third ventricle with cerebral (sylvian) aqueduct
- forth ventricle with a median aperture (magnedie) and two lateral foramina (luschka)
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Neuron components
cell body: resides in grey matter
axons: may be extremely long, mainly contained in white matter
myelin sheath: multiple lamellae of specialized cell membrane surround and insulate axons (speed conduction)
neuron metabolic activity
very high, requires a high demand for glucose and oxygen and very susceptible to a lack of them
upper motor neuron
cell body: resides in grey matter of the frontal lobe. axon travels great distance to braistem and spinal cord to synapse with corresponding lower motor neuron (efferent motor).
lower motor neuron
cell body in spinal cord grey matter
axon exists in anterior nerve root to become peripheral motor nerve (efferent motor)
innervates skeletal muscles
Glia
astrocytes: supporting cell, proliferate in area of injury to form a “scar”
Oligodendrocytes: produce and maintain myelin sheath in CNS
microglia: function not well understood, may be macrophages of CNS
Schwann cell: produce and maintain myelin sheath in PNS.
Etiology of diseases
genetic/heredity traumatic infectious inflammatory vascular/connective tissue metabolic toxic neoplastic
Neurogenic atrophy
degeneration of peripheral nerves which in turn may all lead to atrophy of skeletal muscles.
results in a pattern of atrophy referred to as GOUP ATROPHY.
Small fibers with angular outlines occur together in groups in fascicles that may also have fibers of normal size and morphology or hypertrophied fibers.
Two types of muscle fibers
type 1: acidic condition stains darker. has lots of mitochondria and lipid droplets ==> sustained contractions
type 2: basic condition gets darker, less mitochondria, has glycogen, undergo glycolysis to provide quick energy.
birds on the ground: all type 2 (white muscle)
fly birds: all red, type 1
human: mix
Mechanism of neurogenic/denervation atrophy
progression of denervation and renervation results in grouping of same muscle fiber types.
if disease continue, they will continue to die ==> angular outlined fibers, shrunk and angulated.
characteristics: 1. they are grouped 2. they are atrophic
Myopathies (primary disease of skeletal muscle)
Muscular dystrophy
genetically determined, inherent loss or abnormality of the contractile proteins in the muscle resulting in weakness.
Most common disease: PROGRESSIVE (DUCHENNE) MUSCULAR DYSTROPHY. sex-linked, recessive disorder affects male children.
loss of an important contractile protein DYSTROPHIN
deficiency of dystrophin molecule ==> actin is not anchored in the cell membrane ==> after multiple muscle contraction cell membrane breaks down, influx of Ca2+ into the cell attracts macrophages and kill the cell.
progressive, fatal outcome ~20
epineurium
connects all the neuronal fascicles together. contains blood vessels
endoneurium
connective tissue in between individual nerve fibers
features of muscular dystrophy
- lack of dystrophin molecule
- necrosis
- release of Ca2+ and macrophages come in
- fibrosis
- can document absence of dystrophy by the antibody molecule
axonal degeneration
disease in peripheral nerves results from mechanical insults such as compression or transection.
under suitable conditions, nerve regeneration may be observed.
features of axonal degeneration
myelin sheath break down but schwann cells remain ==> WALLERIAN DEGENERATION
myelin debris phagocytize by macrophages entering the basal lamina surrounding each nerve fiber.
retrograde proximal to the site of injury.
axon regeneration after removal of debris
nerves damaged by closed injuries (crush and freeze) are more likely to regenerate with return of function. Open injuries (penetrating wounds) commonly result in aberrant regenerative sprouting in the form of TRAUMATIC NEUROMA (scar tissue build up, which blocks the growth of axon to its original place).
regeneration forms an axonal CLUSTER
most common trauma to peripheral nerves
metabolic (acquired) and toxic. 50%
==> inflammatory/infectious, hereditary, cytogenic 10-20% each
==> neoplastic 5-10%
