أسئلة المحاضرة الحادية عشر فسيو (قبل التعديل)
52 Questions
0 Views

أسئلة المحاضرة الحادية عشر فسيو (قبل التعديل)

Created by
@inspireeAcademy

Podcast Beta

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What role do cholinesterases play in cholinergic transmission?

  • Increase the production of choline from acetylcholine.
  • Localize the action of acetylcholine at the site of liberation. (correct)
  • Enhance the diffusion of acetylcholine to the bloodstream.
  • Prolong the action of acetylcholine.

    • What is the role of the pre-synaptic neuron?

  • It transmits impulses away from the synapse.
  • It transmits impulses towards the synapse. (correct)
  • It releases neurotransmitters at the nerve endings.
  • It connects directly to the postsynaptic neuron.

    • Which of the following statements about neurotransmitter actions is correct?

  • Muscarinic action occurs quickly but lasts longer.
  • Nicotine action is rapid and short-lived. (correct)
  • Nicotine mimics the action of acetylcholine at smooth muscles.
  • Muscarine has a prolonged effect compared to nicotine.

    • What type of synapse is characterized by a gap junction?

    <p>Electrical synapse</p> Signup and view all the answers

    What is the primary effect of anticholinesterases like neostigmine?

    <p>Prolong the action of acetylcholine.</p> Signup and view all the answers

    Which of the following statements about electrical synapses is true?

    <p>They exhibit resistance to fatigue.</p> Signup and view all the answers

    What distinguishes muscarinic from nicotinic actions?

    <p>Nicotinic actions occur at the neuromuscular junction.</p> Signup and view all the answers

    Which neurotransmitter is associated with cholinergic transmission?

    <p>Acetylcholine</p> Signup and view all the answers

    Which of the following is true regarding the recycling of choline?

    <p>The reuptake of choline occurs back into nerve endings for new acetylcholine formation.</p> Signup and view all the answers

    How do chemical synapses conduct signals compared to electrical synapses?

    <p>They are chemically mediated.</p> Signup and view all the answers

    What characteristic is NOT typical of chemical synapses?

    <p>They are less common than electrical synapses.</p> Signup and view all the answers

    Which of the following best describes the synaptic cleft?

    <p>It is filled with interstitial fluid and separates nerve endings.</p> Signup and view all the answers

    In which scenario would you expect to see fatigue occurring?

    <p>In chemical synapses.</p> Signup and view all the answers

    Which type of receptor is a muscarinic receptor?

    <p>G-protein coupled receptor</p> Signup and view all the answers

    What is the primary effector organ for M2 receptors?

    <p>Heart</p> Signup and view all the answers

    Which agent can block muscarinic receptors?

    <p>Atropine</p> Signup and view all the answers

    What type of nicotinic receptor is found at the autonomic ganglia?

    <p>Neural nicotinic (Nn)</p> Signup and view all the answers

    In which area are M5 receptors currently being investigated?

    <p>Brain</p> Signup and view all the answers

    Which type of fibers release acetylcholine?

    <p>All pre-ganglionic fibers and some sympathetic post-ganglionic fibers</p> Signup and view all the answers

    What is the primary enzyme involved in the synthesis of acetylcholine?

    <p>Choline acetyl transferase (CAT)</p> Signup and view all the answers

    What initiates the release of acetylcholine at the axon terminal?

    <p>Depolarization leading to calcium influx</p> Signup and view all the answers

    What process is responsible for the termination of acetylcholine activity in the synaptic cleft?

    <p>Diffusion to surrounding tissues and enzymatic breakdown</p> Signup and view all the answers

    Which ions are involved in the depolarization of the postsynaptic membrane when acetylcholine binds to its receptors?

    <p>Sodium and calcium</p> Signup and view all the answers

    What is the role of cyclic AMP in cholinergic transmission?

    <p>It serves as a secondary messenger signaling molecule</p> Signup and view all the answers

    Where is acetylcholine stored prior to release?

    <p>In minute vesicles at the nerve terminals</p> Signup and view all the answers

    What occurs to acetylcholine after it binds to receptors on the postsynaptic membrane?

    <p>It undergoes hydrolysis to form acetic acid and choline</p> Signup and view all the answers

    What is the effect of cholinesterases on acetylcholine?

    <p>Maintain its localized action at the site of release</p> Signup and view all the answers

    Which of the following describes the onset and duration of muscarinic action compared to nicotinic action?

    <p>Slow onset and prolonged duration</p> Signup and view all the answers

    What is the primary clinical use of anticholinesterases such as neostigmine?

    <p>To prolong the action of acetylcholine at the neuromuscular junction</p> Signup and view all the answers

    Which of the following statements about muscarinic and nicotinic actions is correct?

    <p>Muscarinic receptors mediate a slow response, while nicotinic receptors mediate a rapid response</p> Signup and view all the answers

    What is the role of acetate in cholinergic transmission?

    <p>To diffuse into blood and be used in other metabolic processes</p> Signup and view all the answers

    Which receptor subtype is primarily associated with smooth muscles and secretory glands?

    <p>M3</p> Signup and view all the answers

    What type of receptors are nicotinic receptors classified as?

    <p>Ligand gated ion channels</p> Signup and view all the answers

    Which substance can block nicotinic receptors at high doses?

    <p>Nicotine</p> Signup and view all the answers

    Which subtype of muscarinic receptors is primarily located in the heart?

    <p>M2</p> Signup and view all the answers

    What effect does atropine have on muscarinic receptors?

    <p>Blocks them</p> Signup and view all the answers

    What is primarily responsible for transmitting impulses away from the synapse?

    <p>Postsynaptic neuron</p> Signup and view all the answers

    Which type of synapse allows for faster transmission of signals?

    <p>Electrical synapse</p> Signup and view all the answers

    What distinguishes chemical synapses in terms of fatigue compared to electrical synapses?

    <p>Chemical synapses do not show fatigue</p> Signup and view all the answers

    Which statement about conduction direction in electrical synapses is true?

    <p>Conduction can occur in both directions</p> Signup and view all the answers

    What factor characterizes the synaptic cleft in cholinergic transmission?

    <p>It separates the presynaptic and postsynaptic membranes</p> Signup and view all the answers

    Which type of synapse is more commonly found in the nervous system?

    <p>Chemical synapse</p> Signup and view all the answers

    What is the role of neurotransmitters in chemical synapses?

    <p>To facilitate the transfer of impulses across a gap</p> Signup and view all the answers

    How does the speed of conduction compare between electrical and chemical synapses?

    <p>Electrical synapses conduct faster than chemical synapses</p> Signup and view all the answers

    Which factors are involved in the synthesis of acetylcholine?

    <p>Acetyl co-A, choline, and choline-acetyl transferase</p> Signup and view all the answers

    What occurs during the release of acetylcholine at the axon terminal?

    <p>Ca influx causes vesicle fusion with the membrane</p> Signup and view all the answers

    Which process is responsible for the inhibition of neurotransmission in cholinergic transmission?

    <p>Hydrolysis of acetylcholine by acetylcholinesterase</p> Signup and view all the answers

    Where are acetylcholine molecules primarily stored before release?

    <p>In vesicles within nerve terminals</p> Signup and view all the answers

    What is the primary effect of acetylcholine binding to its receptors on the postsynaptic membrane?

    <p>Depolarization of the postsynaptic membrane</p> Signup and view all the answers

    Which statement accurately describes the role of calcium ions in cholinergic transmission?

    <p>Calcium ions trigger the release of neurotransmitters from vesicles</p> Signup and view all the answers

    What is one of the mechanisms that leads to hyperpolarization following acetylcholine receptor activation?

    <p>Increased efflux of potassium ions</p> Signup and view all the answers

    How does acetylcholine concentration decrease in the synaptic cleft after its release?

    <p>By hydrolysis into acetic acid and choline</p> Signup and view all the answers

    Study Notes

    Cholinergic Transmission

    • A functional connection between a neuron and a second cell such as neuron, muscle, or gland

    Synapse

    • Electrical Synapse

      • Gap junctions between pre and postsynaptic membranes
      • Allows direct transmission of electrical depolarization waves
      • Rare
      • Resistant to fatigue
      • Conduction in both directions
      • Faster speed

    • Chemical Synapse

      • Junction between pre and postsynaptic membranes mediated by chemicals
      • Very common
      • Chemical substances are released at nerve endings for transmission of nerve impulses
      • Shows fatigue
      • Conduction occurs in one direction
      • Slower speed

    Types of Transmission

    • Cholinergic Transmission:
      • Mediated by Acetylcholine
    • Adrenergic Transmission:
      • Mediated by Noradrenaline

    Sites of Acetylcholine Release

    • All pre-ganglionic fibers
    • Sympathetic pre-ganglionic fibers to adrenal medulla
    • All parasympathetic post-ganglionic fibers
    • Sympathetic post-ganglionic fibers to sweat glands and skeletal muscle blood vessels
    • Motor end plate (Neuromuscular junction)
    • Some synapses in the CNS

    Synthesis of Acetylcholine

    • Acetyl coenzyme A + choline → acetylcholine + coenzyme A in presence of choline acetyltransferase (CAT)
    • ATP and glucose are required to form acetyl coenzyme A

    Storage of Acetylcholine

    • Stored in nerve terminals inside minute vesicles
    • Each vesicle contains thousands of acetylcholine molecules
    • Some acetylcholine molecules are found free in the cytoplasm

    Release of Acetylcholine

    • Action potential reaches axon terminal
    • Depolarization occurs
    • Increased permeability to calcium ions
    • Calcium ions influx
    • Calcium binds to the vesicles and moves them to the membrane
    • Vesicles rupture, releasing acetylcholine into the synaptic cleft through exocytosis
    • Acetylcholine then binds to its receptors on the postsynaptic membrane

    Mechanisms of Action

    • Acetylcholine binds to receptors on the postsynaptic membrane
    • Ligand-gated Ion Channels:
      • Sodium and calcium influx leads to depolarization (stimulation)
      • Potassium efflux and chloride influx leads to hyperpolarization (inhibition)
    • G-protein Coupled Receptors
      • Acetylcholine activates membrane enzymes such as adenyl cyclase
      • Formation of second messenger called cyclic AMP from ATP
      • Intracellular signaling

    Removal of Acetylcholine

    • Diffusion:
      • Diffusion to the surrounding area
      • Decreases acetylcholine concentration
    • Hydrolysis:
      • Choline esterase enzyme breaks down acetylcholine into acetic acid and choline
      • Choline has a similar but weaker action as acetylcholine
      • Choline is reuptaken into the nerve ending and recycled to form new acetylcholine
      • Acetate diffuses into the blood
    • Reuptake:
      • Not yet completely defined

    Anticholinesterases

    • Neostigmine blocks the action of cholinesterase
    • Prolongs the action of acetylcholine
    • Used to treat certain diseases such as myasthenia gravis

    Action of Acetylcholine

    • Muscarinic Action: - Similar to the action of muscarine - Muscarine is an alkaloid from poisonous mushrooms - Affects smooth muscles and glands supplied by parasympathetic and sympathetic cholinergic nerve fibers - Slow onset - Prolonged duration - Antagonist is atropine
    • Nicotinic Action: - Similar to the action of nicotine - Nicotine is derived from tobacco - Affects autonomic ganglia, neuromuscular junction, and adrenal medulla (secretion of adrenaline and noradrenaline) - Rapid onset - Short duration
      - Antagonists: ganglion and neuromuscular blockers

    Acetylcholine Receptors (Cholinergic Receptors)

    • Muscarinic Receptors:
      • Ligand-gated ion channels
      • Located at effector organs of all postganglionic cholinergic nerve terminals
      • Subtypes:
        • M1: Brain and autonomic ganglia
        • M2: Heart
        • M3: Smooth muscles and secretory glands
        • M4: Pancreas
        • M5: Under investigation
      • Stimulated by muscarine
      • Blocked by atropine
    • Nicotinic Receptors:
      • G-protein coupled receptors
      • Located at autonomic ganglia, adrenal medulla, motor endplates
      • Subtypes:
        • Neural nicotinic (Nn): Autonomic ganglia and adrenal medulla
        • Muscle nicotinic (Nm): Motor endplate
      • Stimulated by nicotine (small dose)
      • Blocked by nicotine (large dose)

    Cholinergic Transmission

    • Definition: A functional connection between a neuron and another cell, including neurons, muscle, or glands.
    • Synapse Structure:
      • Pre-synaptic Neuron: Transmits impulses towards the synapse.
      • Synaptic Cleft: A 10-30 nm space filled with interstitial fluid that separates the nerve ending from the next neuron or effector organ.
      • Post-synaptic Neuron: Transmits impulses away from the synapse.

    Types of Synapses

    • Electrical Synapse:
      • A gap junction connects the pre and postsynaptic membranes.
      • Rare occurrence.
      • Allows direct transmission of electrical depolarization waves from the presynaptic to the postsynaptic neuron.
    • Chemical Synapse:
      • A junction mediated by chemicals between the pre and postsynaptic membranes.
      • Very common.
      • Chemicals are released at nerve endings, transmitting nerve impulses from one neuron to another.

    Electrical Synapse vs. Chemical Synapse

    • Presence: Rare vs. Very common.
    • Mechanism: Direct transmission vs. Chemically mediated.
    • Fatigue: Resist fatigue vs. Show fatigue.
    • Conduction: Both directions vs. One direction.
    • Speed: Faster vs. Slower.

    Types of Synaptic Transmission

    • Cholinergic Transmission: Involving acetylcholine as the neurotransmitter.
    • Adrenergic Transmission: Involving noradrenaline as the neurotransmitter.

    Acetylcholine Release Sites

    • All pre-ganglionic fibers.
    • Sympathetic pre-ganglionic fibers to the adrenal medulla.
    • All parasympathetic post-ganglionic fibers.
    • Sympathetic post-ganglionic fibers to sweat glands and skeletal muscle blood vessels.
    • Motor end plate (neuro-muscular junction).
    • Some synapses in the central nervous system (CNS).

    Acetylcholine Synthesis

    • Acetyl co-A reacts with choline in the presence of choline acetyltransferase (CAT) enzyme.
    • Acetyl co-A + Choline → Acetylcholine + co-A.
    • ATP and glucose are required to form acetyl co-A.

    Acetylcholine Storage

    • Stored in nerve terminals within minute vesicles.
    • Each vesicle contains more than one thousand acetylcholine (Ach) molecules (5000-10,000).
    • Some molecules are found free in the cytoplasm.

    Acetylcholine Release

    • When an action potential reaches the axon terminal:
      • Depolarization occurs.
      • Permeability to Ca ions increases.
      • Ca influx occurs.
    • Calcium binds to the vesicles and moves them toward the membrane.
    • Vesicles rupture and release acetylcholine into the synaptic cleft via exocytosis.
    • Acetylcholine passes through the cleft and binds to its receptors on the postsynaptic membrane.

    Acetylcholine Mechanism of Action

    • Acetylcholine binds to receptors on the postsynaptic membrane.
    • Ligand-gated ion channels:
      • Sodium (Na) and calcium (Ca) influx leads to depolarization (stimulation).
      • Potassium (K) efflux and chloride (Cl) influx leads to hyperpolarization (inhibition).
    • G-protein coupled receptors:
      • Activates membrane enzymes, such as adenyl cyclase.
      • Formation of the second messenger, cyclic AMP (cAMP), from ATP.
      • cAMP triggers intracellular signal transduction pathways.

    Acetylcholine Removal

    • Diffusion: Acetylcholine diffuses into the surrounding area, decreasing its concentration.
    • Hydrolysis:
      • Acetylcholinesterase enzyme breaks down acetylcholine into acetic acid and choline.
      • Choline has an action similar to acetylcholine, but weaker. Choline is reuptaken back into the nerve ending to be recycled to form new acetylcholine.
      • Acetate ions diffuse into the blood.
    • Reuptake: The mechanism is not fully understood.

    Clinical Considerations

    • Cholinesterases: Keep the action of acetylcholine localized to the site of liberation.
    • Anticholinesterases:
      • Block the action of cholinesterase.
      • Prolong the action of acetylcholine.
      • Used to treat diseases like myasthenia gravis.

    Actions of Acetylcholine

    • Muscarinic Action:
      • Similar to the action of muscarine, an alkaloid derived from poisonous mushrooms.
      • Affects smooth muscles and glands supplied by parasympathetic and sympathetic cholinergic nerve fibers.
    • Nicotinic Action:
      • Similar to the action of nicotine, derived from tobacco.
      • Affects autonomic ganglia, the neuromuscular junction, and the adrenal medulla (secretion of adrenaline and noradrenaline).

    Muscarinic Action vs. Nicotinic Action

    • Onset: Slow vs. Rapid.
    • Duration: Prolonged vs. Short.
    • Antagonist: Atropine vs. Ganglion and neuromuscular blockers.

    Acetylcholine Receptors (Cholinergic Receptors)

    • Muscarinic Receptors:
      • Ligand-gated ion channels.
      • Found at effector organs for all post-ganglionic cholinergic nerve terminals.
    • Nicotinic Receptors:
      • G-protein coupled receptors.
      • Found at autonomic ganglia, the adrenal medulla, and the motor end plate.

    Muscarinic Receptor Subtypes

    • M1: Brain and autonomic ganglia.
    • M2: Heart.
    • M3: Smooth muscles and secretory glands.
    • M4: Pancreas.
    • M5: Under investigation.

    Nicotinic Receptor Subtypes

    • Neural nicotinic (Nn):
      • Autonomic ganglia
      • Adrenal medulla.
    • Muscle nicotinic (Nm):
      • Motor end plate.

    Acetylcholine Receptor Stimulation and Blockade

    • Muscarinic Receptor Stimulation: Muscarine.
    • Muscarinic Receptor Blockade: Atropine.
    • Nicotinic Receptor Stimulation: Nicotine (small dose).
    • Nicotinic Receptor Blockade: Nicotine (large dose).

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Physiology Lecture l11 PDF

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser