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A 23 year old male patient demonstrating severe face and arm muscle spasms…
A 23 year old male patient demonstrating severe face and arm muscle spasms was brought to the emergency department by his brother. The patient can hardly speak, so you try to get more information from the brother. You note that the patient has many tattoos, including a fresh one on his shoulder. The brother tells you that the patient just got that tattoo yesterday, and that the tattoo parlor was “sketchy.” You order blood tests, and after a little while you get the results. Lab tests show that he is infected with Clostridium tetani, a common bacterium found in soil that can be transmitted by using dirty needles. The patient was never vaccinated against this bacterium. Clostridium tetani produces a toxin that affects neurons and their ability to release neurotransmitters. The worried brother asks you what is going on?
Upstream
Indirect Cause
Introduction of bacteria Clostridium tetani to the patient through a dirty needle used for tattooing
Direct Cause
Tetanus neurotoxin (TeNT) produced, causing muscle spasms and inability to control motor function due to its effects at the NMJ and spinal cord
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Background
Clostridium tetani
Behavior at NMJ
TeNT binds to presynaptic membrane of the NMJ, is internalized, and transported retroaxonally to the spinal cord, where it blocks the release of inhibitory neurotransmitters
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The difference between a twitch, summation, and tetany.
Muscle twitch: an involuntary contraction of a group of muscles, also known as a fasciculation, usually caused by an electric stimulus in a lab setting
Summation: the process by which a sequence of stimuli that are individually inadequate to produce a response are cumulatively able to induce a nerve impulse
Tetany: Spasms of the hands a feet, cramps, spams of the larynx, and overactive neurological reflexes; often due to low blood calcium (hypocalcemia)
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The chain of events at the neuromuscular junction,
- A motor neuron fires an action potential down its axon.
- The motor neuron's axon terminal releases acetylcholine into the synaptic cleft.
- Acetylcholine binds receptors on the junctional folds of the sarcolemma.
- Acetylcholine binding causes a local depolarization called an end plate potential.
Systems Involved
Circulatory System
Made up of heart, lungs, arteries, veins, coronary and portal vessels
Responsible for flow of blood, nutrients, oxygen, and hormones to and from cells
How it's involved: cardiac muscle can become paralyzed due to tetanus toxin; toxin and bacteria can circulate in body through blood vessels
Muscular System
Made up of skeletal, smooth, and cardiac muscles
Responsible for movement of the body, posture, stabilization of joints, and production of heat
How it's involved: muscles contract uncontrollably due to the blockade of inhibitory neurotransmitters; the nervous system can't turn the muscles "off"
Nervous System
Made up of brain, spinal cord, and nerves
Responsible receiving and processing input, higher order function, forming and sending commands to rest of body, and regulation of all body functions
How it's involved: tetanus neurotoxin binds to presynaptic membrane of the NMJ, is internalized, and transported retroaxonally to the spinal cord, where it blocks the release of inhibitory neurotransmitters
Integumentary System
Made up of hair, skin, nails, and sebaceous and sweat glands
Responsible for acting as a barrier to protect the body from the outside world, retaining body fluids, protecting against disease, eliminating waste products, and regulating body temperature
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