Muscle Pathology
What causes depolarization of the motor end plate and initiation of action potentials in the muscle fiber?
ACh
What is required during the contraction-relaxation of muscles?
ATP
What is the thin filament?
Actin
What cause contraction of skeletal muscle fibers?
Action potentials
What happens when ACh travels to the post synaptic end plate and binds to nicotinic cholinergic receptors?
Allows entry of extracellular sodium into motor end plate --> depolarizing motor end plate --> depolarizing muscle fibers
What is the patho behind Malignant Hyperthermia?
Anesthetic agents and succinylcholine may cause cytoplasmic Ca2+ levels to remain elevated during general anesthesia --Ca2+ causes cross bridge cycling to go indefinitely burning a lot of ATP and generating a lot of heat tx: dantrolene
What is Myasthenia Gravis?
Antibodies against postsynaptic ACh receptors --fluctuating fatigue and weakness
What is Lambert-Eaton Myasthenic Syndrome?
Antibodies against the voltage-gated calcium channels of the presynaptic terminal --weak limb muscles
What is each muscle supplied by?
At least 2 spinal roots and 1 peripheral nerve
What ion is responsible for excitation-contraction resulting in muscle movement?
Calcium
What muscle types are under involuntary control?
Cardiac and Smooth
What is the patho behind Dermatomyositis/Polymyositis?
Due to humoral attack to the muscle capillaries and small arterioles (endothelium) -MAC, B and T cells destroy the capillaries --Muscles undergo microinfarction
What is anaerobic glycolysis?
In the absence of oxygen or mitochondria -- product of glycolysis is lactate
What is aerobic glycolysis?
In the presence of oxygen -- product of glycolysis is pyruvate
What is the function of Troponin?
Influences the position of tropomyosin on actin -binds calcium ions in contraction process
What disease state is caused by antibodies to presynaptic calcium channels resulting in impaired ACh release?
Lambert Eaton syndrome
What is the final common pathway for all voluntary movement?
Lower Motor Neuron
What happens in tetanus?
Motor neuron function becomes un-inhibited --> spastic paralysis
What disease state is caused by antibodies toward post-synaptic ACh receptors?
Myasthenia gravis
What is the thick filament?
Myosin
Which contractile protein is known as the thick filament?
Myosin
What are the contractile proteins?
Myosin and Actin --connect to each other (regulates the process of contraction)
What regulates the length of thin filaments (actin)?
Nebulin
What is the point of contact between nerve terminal and skeletal muscle?
Neuromuscular junction
What happens when action potentials depolarize the motor nerve terminal?
Opens voltage gated Ca2+ channels --> Stimulating Ca2+ dependent release of ACh from the terminals
What happens when there is oxygen present for muscle metabolism?
Pyruvate enters the TCA cycle, then oxidative phosphorylation, yielding HIGH ATP
What happens when oxygen is absent in muscle metabolism?
Pyruvate is converted to lactate, yielding much LESS ATP --lactate enters circulation and can lead to lactic acidosis
What does it mean that muscle tissue is excitable?
Responds to chemical, electrical, mechanical stimuli by changes in membrane potential
What kind of muscle is striated and under voluntary control?
Skeletal
What is Muscular Dystrophy?
Slow death of muscle cells due to deficiencies of one of the many proteins --progressive weakening of muscles
What type of muscle is unstriated?
Smooth
What is the most common medication to cause drug induced myopathy?
Statins
What is the sliding filament theory?
This term refers the theory explaining muscle action: A myosin cross-bridge attaches to an actin filament, and then the power stroke drags the two filaments past one another.
What is the elastic protein?
Titin --organization and alignment of thick filaments in sarcomeres
What is Botulism?
Toxin binds irreversibly to presynaptic membranes --weakness, blurred vision, diplopia, ptosis, unreactive pupils
What protein extends over length of thin filament (actin) and covers myosin binding sites?
Tropomyosin
Which regulatory protein covers myosin binding sites?
Tropomyosin
What send axons to synapse with lower motor neurons?
Upper Motor Neurons
