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Questions and Answers
What is the primary role of neurotransmitters in the nervous system?
What is the primary role of neurotransmitters in the nervous system?
Which of the following correctly lists a characteristic of steroid hormones?
Which of the following correctly lists a characteristic of steroid hormones?
Which neurotransmitter is primarily associated with pain signaling?
Which neurotransmitter is primarily associated with pain signaling?
What distinguishes catecholamines from other biogenic amines?
What distinguishes catecholamines from other biogenic amines?
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Which of the following hormones is an amino acid-derived hormone?
Which of the following hormones is an amino acid-derived hormone?
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In terms of signal transduction, what is the role of agonists and antagonists in drug design?
In terms of signal transduction, what is the role of agonists and antagonists in drug design?
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What type of neurotransmitter is primarily responsible for muscle contraction at the neuromuscular junction?
What type of neurotransmitter is primarily responsible for muscle contraction at the neuromuscular junction?
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Which of the following best describes peptide hormones?
Which of the following best describes peptide hormones?
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What is the primary role of voltage-gated calcium channels in muscle contraction?
What is the primary role of voltage-gated calcium channels in muscle contraction?
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How do muscarinic receptors differ from ion channel receptors?
How do muscarinic receptors differ from ion channel receptors?
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What is a characteristic of the G-protein-coupled receptors that affects cell function?
What is a characteristic of the G-protein-coupled receptors that affects cell function?
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What happens at the axon hillock when dendritic depolarizations reach the threshold?
What happens at the axon hillock when dendritic depolarizations reach the threshold?
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Why are ion channel-mediated signaling pathways considered faster than others?
Why are ion channel-mediated signaling pathways considered faster than others?
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What is a common difference between nicotine and muscarine in pharmacology?
What is a common difference between nicotine and muscarine in pharmacology?
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What role does GTP play in the function of G-proteins?
What role does GTP play in the function of G-proteins?
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Which characteristic distinguishes the muscarinic receptor's response to acetylcholine?
Which characteristic distinguishes the muscarinic receptor's response to acetylcholine?
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What initiates the release of acetylcholine at the motor end plate?
What initiates the release of acetylcholine at the motor end plate?
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Which of the following best describes the role of acetylcholinesterase at the synaptic cleft?
Which of the following best describes the role of acetylcholinesterase at the synaptic cleft?
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How does binding of acetylcholine to its receptor influence the muscle cell?
How does binding of acetylcholine to its receptor influence the muscle cell?
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What is the effect of neurotoxins that inhibit acetylcholinesterase?
What is the effect of neurotoxins that inhibit acetylcholinesterase?
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Which structure is primarily responsible for synthesizing and storing acetylcholine?
Which structure is primarily responsible for synthesizing and storing acetylcholine?
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What type of receptor is the nicotinic acetylcholine receptor classified as?
What type of receptor is the nicotinic acetylcholine receptor classified as?
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In what way does the synaptic cleft contribute to neuronal signaling?
In what way does the synaptic cleft contribute to neuronal signaling?
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Which component of the neuromuscular junction is primarily responsible for forming the synaptic cleft?
Which component of the neuromuscular junction is primarily responsible for forming the synaptic cleft?
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Study Notes
Chemical Signals
- Defects in secretion and signalling can lead to disease.
- Drugs often work by mimicking chemical signals, acting as agonists or antagonists.
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Neurotransmitters:
- Amino acids: GABA, glutamine, glycine
- Acetylcholine
- Small molecules: serotonin, histamine, dopamine (biogenic amines)
- Catecholamines: noradrenaline and adrenaline (derived from tyrosine)
- Purinergic neurotransmitters: ATP and adenosine
- Neuropeptides: endorphin, enkephalins, substance P (pain), neuropeptide Y (eating)
- Many neurotransmitters have other functions in the body.
Hormones
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Lipid-soluble hormones: derived from cholesterol (steroid hormones)
- Can diffuse across cell membranes.
- Examples: oestradiol, testosterone, aldosterone, cortisol
- Bound to proteins for blood transport, long half-life (60-90 minutes).
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Amino-acid derived hormones:
- Adrenaline and noradrenaline: derived from tyrosine in the adrenal gland, short half-life (about 1 minute).
- Thyroxine: produced in the thyroid gland from tyrosine and iodine.
- Melatonin: produced in the pineal gland from tryptophan.
Peptide hormones
- Short peptides: ADH (antidiuretic hormone) and oxytocin, produced in the brain and released by the posterior pituitary gland (9 amino acids).
- Small proteins: growth hormone (191 amino acids).
- Glycoproteins: FSH (follicle-stimulating hormone) (96 amino acids).
- Insulin: composed of α-chain (21 amino acids) and β-chain (30 amino acids) bridged by disulfide bonds.
Faster Signalling: Action Potentials
- Calcium ion influx through voltage-gated channels activates contraction in muscle cells.
- In nerve cells, dendritic depolarizations summate at the axon hillock, triggering an action potential if a threshold is reached.
- Action potentials are the fastest type of signal transduction.
Slower Signalling: Muscarinic Acetylcholine Receptors
- Muscarinic acetylcholine receptors are G-protein-coupled receptors that mediate acetylcholine responses from parasympathetic nerves.
- They do not have an ion channel, so they trigger different responses (and have different pharmacology) than nicotinic acetylcholine receptors.
- Acetylcholine binds to the receptor's extracellular side, causing a structural change on the inner side and affecting the interaction with the G-protein complex.
- G-proteins are GTP-coupled protein complexes and are essential for many cell functions.
The Motor End Plate
- The motor end plate is the synapse between a motor neuron and a muscle cell.
- When a nerve impulse reaches the motor end plate, acetylcholine-filled vesicles fuse with the presynaptic membrane, releasing acetylcholine into the synaptic cleft.
- Acetylcholine binds to acetylcholine receptors (AChR) on the muscle cell membrane.
Post-Synaptic Events
- Acetylcholinesterase rapidly breaks down acetylcholine in the synaptic cleft.
- Some acetylcholine is also taken back up by the presynaptic membrane.
- Neurotoxins and insecticides can inhibit acetylcholinesterase, leading to paralysis.
- Presynaptic vesicles can release multiple bioactive substances.
- The nicotinic acetylcholine receptor (AChR) is a pentameric protein spanning the muscle cell membrane. It has binding site(s) for acetylcholine on its extracellular face.
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Description
Explore the intricate world of chemical signals and hormones in this quiz. Learn about neurotransmitters, neuropeptides, and the various types of hormones, including lipid-soluble and amino-acid derived hormones. Understand their roles in disease and drug action.
