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23 year old has severe face and muscle spasms (Normal Physiology &…
23 year old has severe face and muscle spasms
Possible Direct Upstream Cause
Bacteria
Clostridium tetani
Possible Indirect Upstream Cause
-Tattoo parlor (most probable cause for the patient having the bacteria)
-Dirty Needle
-Not vaccinated against Clostridium tetani
Ion Channels (2 Classes)
Voltage Gated Ion Channels
open or close in response to voltage changes in membrane potential
Chemically Gated Ion Channels
opened by chemical messengers such as neureotransmitters
Anatomy of Motor Neurons & Neuromuscular Junction
Axons
(long, threadlike extensions of motor neurons)
-travel from central nervous system to skeletal muscle
Axon Terminal
(end of axon)
end of axon and muscle fiber separated by gel-filled space called synaptic cleft
Motor End Plate
-oval shaped
-highly excitable region of sarcolemma
-Divide into many branches as it enters muscle
Axon ends on muscle fiber, creating a neuromuscular junction
Events at the Axon Terminal
1
.
AP arrives at axon terminal
2.
Voltage-gated calcium channels open, calcium enters motor neuron
3.
Calcium entry causes release of ACh (neurotransmitter) into synaptic cleft
4.
ACh diffuses across to ACh receptor (Na+ chemical gates) on sarcolemma
5.
ACh binding receptors open gates, allowing Na+ to enter, resulting in end plate potential
6.
Acetylcholinerase (enzyme) degrades ACh
Generation of AP Across Sarcolemma
1. End Plate potential
-ACh released from motor neuron binds to ACh receptors on sarcolemma
-Chemically gated channels open
-Na+ diffuses in muscle fiber
-Interior becomes less negative
2. Depolarization
-generation & propagationof an Action potential
-if end plate potential causes enough change in membrane,voltage to reach critical level called threshold
Voltage gated channels in membrane will open
3. Repolarization
-restoration of resting conditions
-Na+ channels close, K+ channels open
-K+ flowout of cell, brings back to initial resting membrane
-Ionic conditions of resting state restored by Na+ K+ pump
Refractory Period
muscle fiber can't be stimulated for specific amount of time,until repolarization is complete
results in depolarization
Steps in E-C Coupling
1.
AP propogates long sarcolemma & down T tubules
2.
Calcium ions are released
-Transmission of AP along t tubules of triads cause voltage sensitive tubule proteins to change shape.
-Shape change opens Ca=release channels in terminal cisterns of SR, Ca+ flows out
Cross Bridge Cycling
1. Cross bridge formation
-high energy myosin heads attaches to actin thin filament active site
2. Working (power) stroke
-myosin head pivots & pulls thin filament toward M line
3. Cross bridge Detachment
-ATP attaches to myosin head
-causes cross bridge to detach
4. Cocking of Myosin Head
-Energy from hydrolysis of ATP"cockes" myosin head into high energy state
-Energy used for power stroke in next cross bridge cycle
E-C Coupling
1 more item...
Normal Physiology & Homeostatic Set Points
Brain sends message to specific body part
Neuromuscular junction process occurs
Contraction occurs
Relevant Intracellular Energy/Nutrition/Metabolism Pathways
ACh is released from the synaptic vesicles
ACh attaches to motor end plates
Ion channels open and sodium ions flow across membrane to muscle cell
Generation of Muscle Action Potential
-flow of sodium ions generates Muscle AP
Action potential travels across sarcolemma and through t tubules
ACh is broken down by acetylcholinerase in the synaptic cleft
Clostridium tetani makes its way into the body
Releases toxin tetanospasmin
Toxin blocks the release of inhibitory neurotransmitters
Once toxin binds to synapses, an antitoxin is useless
Muscles relax after being contracted
Tetanospasmin prevents release of neurotransmitters
This causes muscles spasms throughout the body as well as pain
medication need to treat, vaccine availalble
Specific Problem #1:
Patient's inability to speak
Possible Direct Downstream Effect
Muscles are not in use due to Clostridium tetani
Possible Indirect Downstream Effects
-Bacteria causes lockjaw and muscle stiffness
-Can even have difficulty swallowing food
Specific Problem #2
Fresh tattoo
Possible Direct Downstream Effect
Fresh wound is a portal of entry for bacteria
Possible Indirect Downstream Effect
-Many infections can occur ( ex: clostridium tetani)
Specific Problem #3
Infected with Clostridium tetani
Possible Direct Downstream Effect
Bacteria releases toxins into the motor neurons
Possible Indirect Downstream Effect
Muscles begin to have spasms , lockjaw, many body systems affected b
Specific Problem #4
Patient not vaccinated against bacteria
Possible Direct Downstream Effect
-Body is easily targeted by bacteria
-No type of antibodies
Possible Indirect Downstream Effects
Person's immune system is weak when tetanolysin enters the body through the open wounds
Specific Problem #5
Toxins affect neurons
Possible Direct Downstream Effects
Toxin, tetanospasmin blocks release of neurotransmitters at motor nerve endings throughout the body (muscles specifically)
Possible Indirect Downstream Effects
Blockage leads to activation of motor neurons, in turn leading to muscle spasms throughout the body
Neurotransmitters Involved
Acetylchole (ACh)
chemical messenger that helps carry signals acros nerve synapse
Epinephrine
-Enters bloodstream and initiates several responses
-Provides energy so major muscles of body can respond to perceived to threat
Norepinephrine
-Released wenan electrical impulse
-Increases rate of contractions of hart
Steps Involved in Exocytosis
Material approaches vesicle
Bubble forms around the material
Cell releases to the outside of the cell
Twitch
simplest contraction resulting from muscle fiber's response to single action potential from motor neuron
3 phases:
latent period
2.Period of Contraction
3.Period of Relaxation
Summation
Increases the force of contraction by increasing frequency of stimulus of muscle fibers
Tetaus
Sustained contraction that occurs when frequency of stimulation so fast that there's no relaxation