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23 Cards in this Set
- Front
- Back
- 3rd side (hint)
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What are the steps in Neuromuscular Transmission?
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1) Action potential propagated down motoneuron until presynaptic terminal depolarized
2) Voltage-gated Ca++ channels open which allows Ca++ influx (at nerve terminal) 3) Exocytosis of stored acetylcholine (ACh) into synaptic cleft 4) ACh diffuses across synaptic cleft to muscle-end plate where it binds to nicotinic ACh receptors (AChR) 5) Nicotinic AChR is also an ion channel for Na+ and K+. ACh binding causes channel to open 6) Na+ down respective gradient causing depolarization to occur (termed end plate potential) 7) Depolarization spreads to neighboring regions of the muscle fiber 8) Muscle fibers depolarized to threshold and fire action potentials which initiates sequence of events to cause contraction |
AP--> Ca++ Channels--> Exocytosis of ACh--> opens up Na+ and K+ channels--> depolarization--> spreads--> muscle contraction
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What is the enzyme that breaks down acetylcholine in the synaptic cleft?
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Acetylcholine Esterase
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Is there a pre/post ganglia involved in the propagation of AP to striated muscle?
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No
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Which of the following could potentially cause the symptoms associated with myasthenia gravis?
a) Dehydration b) Acetylcholine receptor antibody c) Acetylcholinesterase inhibition |
b) Acetylcholine receptor antibody
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What happens in MG?
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Inability of ACh to attach to AChR--> No opening of ion channels--> No action potential--> No muscular contraction
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What type of medication could with MG?
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Pyridostigmine, an acetylcholinesterase inhibitor, prevents breakdown of acetylcholine in the synaptic cleft. High levels of acetylcholine in the synaptic cleft can help overcome the resistance put up by the antibodies
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How does Clostridium Botulinum work?
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It produces a toxin that blocks the release of ACh from motoneuron terminals thereby causing total blockade of neuromuscular transmission.
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What is Fiber hypertrophy?
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An increase in the number of actin and myosin filaments in each muscle fiber as a result of increased work (e.g. resistance training)
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Hypertrophy is NOT hyperplasia (only under rare conditions of extreme muscle force do the actual number of muscle fibers increase!)
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What is Fiber atrophy?
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Occurs if the muscle remains unused for many weeks.
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Final stages include destroyed muscle fibers with replacement by fibrous and fatty tissue (at this point, which is in about 1-2 years, there is a total loss of contractile function with no capability of regenerating myofibrils).
Additionally, fibrous tissue that replaces muscle fibers has a tendency to continue shortening for many months. |
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What is a Contusion?
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Trauma by a hard object results in local hemorrhage manifesting as ecchymoses
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What is a hematoma?
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A large area of local hemorrhage .
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Do not have to be the result of an injury.
May not have superficial ecchymoses (may be deep). Hematomas can cause pain as blood accumulates and exerts pressure on nerve endings. Hematomas take much longer to subside than contusions. Hematomas may become infected because it may act as a culture medium. |
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Will a contusion blanche?
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No
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What is a Strain?
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Stretching injury to a muscle or a musculotendinous unit caused by mechanical overloading.
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Guess what clinical maneuver causes pain with a strain? Any kind of resistance test
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What is a Sprain?
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Caused by abnormal and excessive movement of a joint (may be slightly torn to complete avulsion).
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Guess what clinical maneuver causes pain with a sprain?
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What heals faster, tendon or ligament?
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Tendon, has better blood supply
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What does DCAP-BTLS stand for?
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Deformities
Contustions Abrasions Punctures/Penetrations Burns Tenderness Lacerations Swelling |
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What are the stages of bone healing?
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Hematoma Formation
Cellular Proliferation and Callus Formation Ossification Remodeling |
1) Hematoma Formation - Clotting factors initiate formation of fibrin meshwork, which serves as framework for ingrowth of fibroblasts and new capillary buds (very important!)
2) Cellular Proliferation and Callus Formation - Fibrocartilaginous callus allows bridge to form, which connects bone fragments 3) Ossification - Mineralization of the fibrocartilaginous callus 4) Remodeling - Reorganization of mineralized bone along lines of mechanical stress |
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What is the single most important element in obtaining union of the fracture fragments?
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Immobilization
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What are the fractures that are prone to nonunion if not immobilized quickly enough?
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1) Scaphoid Fracture
2) Proximal fifth metatarsal fracture (Jones fx) 3) Tibial fractures |
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What is an Osteosarcoma?
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The most common type of malignant bone cancer, accounting for 35% of primary bone malignancies. There is a preference for the metaphyseal region of tubular long bones. 50% of cases occur around the knee. It is a malignant connective (soft) tissue tumor whose neoplastic cells present osteoblastic differentiation and form tumoral bone.
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What is the Epiphysis?
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Growth center
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What is the Metaphysis?
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Area lies just beneath the physis (growth plate)
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What is the Diaphysis?
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Shaft
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