Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

14. The Autonomic Nervous System

Neurotransmitters of the ANS

Anatomy & Physiology

14. The Autonomic Nervous System

Neurotransmitters of the ANS

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Problem L3.1

Textbook Question

The poison curare (kyoo-RAH-ray) blocks the binding of acetylcholine to its receptors at the neuromuscular junction. What effects would you predict from such a poison? Can you think of any useful applications for it? Why might an overdose of it be lethal?

Verified step by step guidance

Understand the role of acetylcholine (ACh) at the neuromuscular junction: Acetylcholine is a neurotransmitter that binds to receptors on the muscle cell membrane (sarcolemma) to initiate muscle contraction. Blocking this binding prevents the muscle from receiving the signal to contract.

Predict the effects of curare: Since curare blocks ACh from binding to its receptors, it would lead to muscle paralysis. This is because the muscle fibers cannot depolarize and initiate contraction without the ACh-receptor interaction.

Consider potential applications: Curare or similar compounds can be used in controlled medical settings as muscle relaxants during surgeries to prevent involuntary muscle movements. This is particularly useful in procedures requiring complete muscle relaxation.

Explain why an overdose could be lethal: An overdose of curare could paralyze critical muscles, such as the diaphragm and intercostal muscles, which are essential for breathing. Without the ability to contract these muscles, respiratory failure would occur, leading to death if not treated promptly.

Discuss possible treatments for overdose: In cases of curare poisoning, treatments may include mechanical ventilation to support breathing and the administration of acetylcholinesterase inhibitors, which increase the concentration of acetylcholine in the synaptic cleft to compete with curare for receptor binding.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Neuromuscular Junction

The neuromuscular junction is the synapse or connection point between a motor neuron and a muscle fiber. It is where the transmission of signals occurs, allowing muscles to contract. Acetylcholine, a neurotransmitter, is released from the motor neuron and binds to receptors on the muscle fiber, triggering muscle contraction. Understanding this process is crucial for predicting the effects of curare.

Acetylcholine Receptors

Acetylcholine receptors are specialized proteins located on the surface of muscle cells that bind acetylcholine. When acetylcholine binds to these receptors, it initiates a series of events leading to muscle contraction. Curare's action of blocking these receptors prevents muscle contraction, leading to paralysis. This concept is essential for understanding the physiological effects of curare.

Toxicology and Lethality

Toxicology is the study of the adverse effects of substances on living organisms. An overdose of curare can be lethal because it causes paralysis of the respiratory muscles, leading to respiratory failure. Without the ability to breathe, the body cannot obtain oxygen, resulting in death. This highlights the importance of dosage and the potential dangers of neurotoxic substances.

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Related Practice

Textbook Question

Receptors that bind acetylcholine at the postsynaptic membrane are:

(a) Chemically gated channels

(b) Voltage-gated channels

(d) Mechanically gated channels

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Textbook Question

Since at any moment a neuron is likely to have thousands of neurons releasing neurotransmitters at its surface, how is neuronal activity (to fire or not to fire) determined?

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Textbook Question

In the Netherlands a young man named Jan was admitted to the emergency room. He and his friends had been to a rave. His friends say he started twitching and having muscle spasms which progressed until he was 'stiff as a board.' On examination, staff found a marked increase in muscle tone and hyperreflexia involving facial and limb muscles. In his pocket, he had unmarked dark yellow tablets with dark flecks. Analysis of the tablets showed them to contain a mixture of ecstasy and strychnine. Ecstasy would not cause this clinical picture, but strychnine, which blocks glycine receptors, could. Explain how.

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Textbook Question

The drug neostigmine blocks the activity of the enzyme acetylcholinesterase in the synaptic cleft. Predict the effects of this drug.

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Textbook Question

Match the following neurotransmitters with their correct description.

_____ GABA

_____ Dopamine

_____ Substance P

_____ Acetylcholine

_____ Glutamate

_____ Endorphins

_____ Norepinephrine

a. Neuropeptide involved in transmission of pain

b. Neurotransmitter released at the neuromuscular junction

c. Major excitatory neurotransmitter in the brain

d. Major inhibitory neurotransmitter in the brain

e. Neuropeptide involved in relief of pain

f. Catecholamine involved in the autonomic nervous system

g. Catecholamine involved in movement and behavior

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Textbook Question

Which neurotransmitter(s) is/are used by sympathetic postganglionic neurons?

a. Epinephrine

b. Norepinephrine

c. Acetylcholine

d. Both a and b

e. All of the above

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Textbook Question

Many chemical warfare agents, such as the poisonous gas sarin, block the enzyme acetylcholinesterase in the synaptic cleft. What effects will this poison have on muscle contraction? What effects will it have on the autonomic nervous system? What symptoms would you expect to see from this poison?

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Textbook Question

Mrs. Jones has had a progressive decline in her mental capabilities in the last five or six years. At first her family attributed her occasional memory lapses, confusion, and agitation to grief over her husband's death six years earlier. When examined, Mrs. Jones was aware of her cognitive problems and was shown to have an IQ score approximately 30 points less than would be predicted by her work history. A CT scan showed diffuse cerebral atrophy. The physician prescribed an acetylcholinesterase inhibitor and Mrs. Jones showed slight improvement. What is Mrs. Jones's problem? Why did the acetylcholinesterase inhibitor help?

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