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Questions and Answers
Which enzyme directly facilitates the conversion of tyrosine to DOPA in the synthesis of noradrenaline?
Which enzyme directly facilitates the conversion of tyrosine to DOPA in the synthesis of noradrenaline?
- Phenylalanine hydroxylase
- Monoamine oxidase
- Dopamine β-hydroxylase
- Tyrosine hydroxylase (correct)
What is the primary mechanism for the removal of secreted noradrenaline from the synaptic cleft, according to the text?
What is the primary mechanism for the removal of secreted noradrenaline from the synaptic cleft, according to the text?
- Diffusion into the bloodstream and subsequent removal
- Destruction by MAO located on the outer surface of the mitochondria
- Re-uptake into the adrenergic nerve endings via active transport (correct)
- Metabolic breakdown by COMT in the surrounding tissues
Which statement accurately describes the location of the enzyme MAO (monoamine oxidase) in relation to noradrenaline removal?
Which statement accurately describes the location of the enzyme MAO (monoamine oxidase) in relation to noradrenaline removal?
- It is mainly present in blood plasma.
- It is found on the outer surface of mitochondria. (correct)
- It is located in the surrounding body fluids.
- It is found within the adrenergic nerve endings.
Which of the following enzymes is NOT directly involved in the synthesis of noradrenaline?
Which of the following enzymes is NOT directly involved in the synthesis of noradrenaline?
In contrast to MAO, where is COMT (catechol-O-methyl-transferase) primarily located with regards to adrenergic nerve terminals?
In contrast to MAO, where is COMT (catechol-O-methyl-transferase) primarily located with regards to adrenergic nerve terminals?
Which of the following best describes the distribution of cholinergic fibers in the autonomic nervous system?
Which of the following best describes the distribution of cholinergic fibers in the autonomic nervous system?
The complex mechanism that maintains the internal environment's temperature is primarily controlled by which brain structure?
The complex mechanism that maintains the internal environment's temperature is primarily controlled by which brain structure?
What is the immediate precursor of acetylcholine in the synthesis pathway?
What is the immediate precursor of acetylcholine in the synthesis pathway?
Stimulation of the preoptic area within the anterior hypothalamus would likely result in which physiological response?
Stimulation of the preoptic area within the anterior hypothalamus would likely result in which physiological response?
Where is the enzyme choline acetyltransferase primarily located?
Where is the enzyme choline acetyltransferase primarily located?
Which of the following best describes the origin of simple reflexes like micturition and defecation?
Which of the following best describes the origin of simple reflexes like micturition and defecation?
What is the functional role of mitochondria within the synaptic knobs of cholinergic fibers?
What is the functional role of mitochondria within the synaptic knobs of cholinergic fibers?
Which of the following is a specific function of some postganglionic sympathetic cholinergic fibers?
Which of the following is a specific function of some postganglionic sympathetic cholinergic fibers?
Which neurotransmitter is most associated with the chemical transmission between pre- and postganglionic neurons, as well as between postganglionic neurons and autonomic effectors within the autonomic nervous system?
Which neurotransmitter is most associated with the chemical transmission between pre- and postganglionic neurons, as well as between postganglionic neurons and autonomic effectors within the autonomic nervous system?
Which brain region primarily controls reflexes related to light and accommodation?
Which brain region primarily controls reflexes related to light and accommodation?
If a drug inhibits the reuptake of choline into cholinergic neurons, what would be the most immediate and direct result?
If a drug inhibits the reuptake of choline into cholinergic neurons, what would be the most immediate and direct result?
Stimulation of the posterior and lateral nuclei of the hypothalamus would most likely cause which of the following?
Stimulation of the posterior and lateral nuclei of the hypothalamus would most likely cause which of the following?
What is the role of the suprarenal medulla in response to the stimulation of acetylcholine?
What is the role of the suprarenal medulla in response to the stimulation of acetylcholine?
Where is the majority of stored acetylcholine found in cholinergic nerve fibers?
Where is the majority of stored acetylcholine found in cholinergic nerve fibers?
What term best describes a chemical substance that binds to a specific site on a receptor, potentially mimicking or blocking the action of a neurotransmitter?
What term best describes a chemical substance that binds to a specific site on a receptor, potentially mimicking or blocking the action of a neurotransmitter?
Which of the following does not act as a center of the autonomic reflexes?
Which of the following does not act as a center of the autonomic reflexes?
What is the primary mechanism by which acetylcholine is released from nerve terminals?
What is the primary mechanism by which acetylcholine is released from nerve terminals?
Which enzyme is primarily responsible for the rapid breakdown of acetylcholine in the synaptic cleft?
Which enzyme is primarily responsible for the rapid breakdown of acetylcholine in the synaptic cleft?
Where is the enzyme acetylcholinesterase (AChE) NOT found in high concentrations?
Where is the enzyme acetylcholinesterase (AChE) NOT found in high concentrations?
What happens to the choline molecules after acetylcholine is broken down?
What happens to the choline molecules after acetylcholine is broken down?
What type of fibers release noradrenaline (norepinephrine) as their primary chemical transmitter?
What type of fibers release noradrenaline (norepinephrine) as their primary chemical transmitter?
Where is noradrenaline (norepinephrine) primarily synthesized?
Where is noradrenaline (norepinephrine) primarily synthesized?
In what form is noradrenaline (norepinephrine) stored within the granulated dark vesicles?
In what form is noradrenaline (norepinephrine) stored within the granulated dark vesicles?
Which of the following statements is correct regarding the comparison between AChE and PsChE?
Which of the following statements is correct regarding the comparison between AChE and PsChE?
Flashcards
What controls simple autonomic reflexes?
What controls simple autonomic reflexes?
The simple reflexes, like urination and defecation, are controlled by the sacral segments of the spinal cord.
What controls complex autonomic reflexes?
What controls complex autonomic reflexes?
The medulla oblongata controls complex autonomic reflexes, like respiration (breathing) and blood pressure regulation.
What controls eye reflexes?
What controls eye reflexes?
The midbrain handles eye reflexes, like response to light and focusing.
What part of the brain is the master of homeostasis?
What part of the brain is the master of homeostasis?
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What parts of the brain control emotional reflexes?
What parts of the brain control emotional reflexes?
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Why is the hypothalamus called the HEAD ganglion of the autonomic nervous system?
Why is the hypothalamus called the HEAD ganglion of the autonomic nervous system?
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What is the parasympathetic part of the hypothalamus?
What is the parasympathetic part of the hypothalamus?
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What is the sympathetic part of the hypothalamus?
What is the sympathetic part of the hypothalamus?
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Tyrosine Hydroxylase
Tyrosine Hydroxylase
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DOPA Decarboxylase
DOPA Decarboxylase
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Dopamine β-Hydroxylase
Dopamine β-Hydroxylase
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Reuptake of Norepinephrine
Reuptake of Norepinephrine
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Monoamine Oxidase (MAO)
Monoamine Oxidase (MAO)
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What are cholinergic fibers?
What are cholinergic fibers?
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What are adrenergic fibers?
What are adrenergic fibers?
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Which autonomic fibers are cholinergic?
Which autonomic fibers are cholinergic?
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Which postganglionic fibers are cholinergic?
Which postganglionic fibers are cholinergic?
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Which postganglionic sympathetic fibers are cholinergic?
Which postganglionic sympathetic fibers are cholinergic?
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Where is acetylcholine synthesized?
Where is acetylcholine synthesized?
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How is acetylcholine synthesized?
How is acetylcholine synthesized?
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Where is acetylcholine stored?
Where is acetylcholine stored?
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Acetylcholine Release
Acetylcholine Release
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Acetylcholinesterase (AChE)
Acetylcholinesterase (AChE)
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Acetylcholine
Acetylcholine
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Cholinergic Fiber
Cholinergic Fiber
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Noradrenaline Synthesis
Noradrenaline Synthesis
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Adrenergic Fiber
Adrenergic Fiber
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Granulated Dark Vesicles
Granulated Dark Vesicles
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Chromogranin
Chromogranin
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Study Notes
Autonomic Nervous System: Centers & Chemical Transmission
- The autonomic nervous system (ANS) regulates involuntary functions like heart rate, digestion, and breathing.
- The ANS has centers for various reflexes, including simple ones (like micturition and defecation) and more complex ones (regulating respiration and blood pressure).
- Centers are located in the spinal cord, medulla, midbrain, hypothalamus, and limbic system, and cerebral cortex.
- The center in the body coordinating various reflexes is the Hypothalmus.
Chemical Transmission at Autonomic Junctions
- Neurotransmitters transmit nerve impulses across synapses (junctions).
- A ligand is a molecule that binds to a specific receptor site on a protein molecule, the ligand could be an agonist, antagonist, or a neurotransmitter itself.
- More than 50 chemicals act as neurotransmitters.
Autonomic Function of the Hypothalamus
- The hypothalamus plays a crucial role in autonomic functions.
- It is considered the main regulatory center for the ANS (autonomic nervous system).
- The anterior hypothalamus is involved in parasympathetic functions, decreases heart rate, blood pressure, and produces cutaneous vasodilation.
- The posterior hypothalamus is involved in sympathetic functions, increases heart rate, blood pressure, and produces cutaneous vasoconstriction.
- Lateral and posterior regions in relation to the hypothalamus have function related to feeding, hunger, satiety, blood pressure, and temperature regulation
Chemical Transmitters
- Acetylcholine (ACh) is a neurotransmitter released by cholinergic fibers.
- These fibers are crucial in both the parasympathetic and sympathetic systems
- All preganglionic fibers are cholinergic.
- Some postganglionic fibers (e.g., those to sweat glands and blood vessels) are also cholinergic.
- Norepinephrine (NE) is released by adrenergic fibers.
- Most postganglionic sympathetic fibers are adrenergic.
- Adrenal medulla also releases NE and epinephrine into the bloodstream
Synthesis and Release of Acetylcholine:
- Acetylcholine (ACh) is synthesized from choline and acetyl-CoA in the terminal nerve endings of cholinergic fibers.
- Choline acetyltransferase is the enzyme that catalyzes this reaction.
- When a nerve impulse reaches the axon terminals, voltage-gated calcium channels open.
- This influx of calcium causes the release of ACh from synaptic vesicles into the synaptic cleft.
Removal of Acetylcholine:
- Acetylcholinesterase (AChE) is an enzyme present in the synaptic cleft, rapidly breaks down ACh into choline and acetate, terminating its signal.
- The breakdown products are taken back into the nerve terminal for reuse, completing the cycle.
Synthesis and Release of Norepinephrine
- Norepinephrine (NE) is synthesized from tyrosine in the terminal nerve endings of adrenergic fibers and the adrenal medulla.
- Tyrosine hydroxylase, DOPA decarboxylase, and dopamine β-hydroxylase are the enzymes involved in the synthetic pathway.
- When a nerve impulse reaches the terminal endings, NE is released by exocytosis into the synaptic cleft.
Removal of Norepinephrine
- Norepinephrine is removed from the synapse by reuptake into the presynaptic terminal, diffusion into the blood, and enzymatic degradation (by monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT)).
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