Understanding Synaptic Morphology
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What is the primary change in ionic channels during the depolarization phase of a neuron's action potential?

  • Ligand-gated sodium channels open, allowing an influx of sodium ions into the neuron
  • Voltage-gated sodium channels open, allowing an influx of sodium ions into the neuron (correct)
  • Voltage-gated calcium channels open, allowing an influx of calcium ions into the neuron
  • Voltage-gated potassium channels open, allowing an efflux of potassium ions out of the neuron

    • What is the state of voltage-gated sodium channels at rest in a neuron?

  • Closed (correct)
  • Fully open
  • Partially open
  • Inactivated

    • What maintains the negative charge inside a neuron at rest?

  • Some potassium channels are open (correct)
  • Sodium-potassium pumps actively transport ions
  • $H^+$ ions accumulate inside the neuron
  • Chloride channels are closed

    • What happens to the membrane potential when a neuron undergoes depolarization?

    <p>$V_m$ becomes less negative</p> Signup and view all the answers

    What triggers the rapid influx of sodium ions, creating the action potential in a neuron?

    <p>Depolarization of the membrane potential above a certain threshold</p> Signup and view all the answers

    What is the primary responsibility of smooth muscle in the body?

    <p>Involuntary contractions in internal organs and structures</p> Signup and view all the answers

    What protein structure acts as attachment points for thin actin filaments in a sarcomere?

    <p>Z-Disc (Z-Line)</p> Signup and view all the answers

    What is the region within the A-band where only myosin filaments are present, and there is no overlap with actin filaments?

    <p>H-Zone</p> Signup and view all the answers

    What giant protein spans from the Z-disc to the M-line in a sarcomere, providing structural support and elasticity?

    <p>\text{Titin}</p> Signup and view all the answers

    What causes depolarization and action potential propagation through T-tubules at the neuromuscular junction?

    <p>Release of acetylcholine</p> Signup and view all the answers

    Which neurotransmitter is primarily responsible for regulating mood, reward, and pleasure?

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

    What is the location of serotonin primarily found in?

    <p>Gastrointestinal tract and central nervous system</p> Signup and view all the answers

    Which neurotransmitter acts as a natural painkiller and produces feelings of euphoria?

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

    What is the process that begins with the arrival of an action potential at the neuromuscular junction?

    <p>Release of Acetylcholine (ACh)</p> Signup and view all the answers

    What happens when calcium ions bind to troponin in muscle contraction?

    <p>Conformational change exposing myosin-binding sites on actin filaments</p> Signup and view all the answers

    What is the function of GABA as a neurotransmitter?

    <p>Inhibition of nerve transmission in the brain and central nervous system</p> Signup and view all the answers

    What is the function of synaptic vesicles?

    <p>Storing and releasing neurotransmitters</p> Signup and view all the answers

    Where do neurotransmitters bind to initiate a response in the postsynaptic cell?

    <p>Receptors on the postsynaptic membrane</p> Signup and view all the answers

    What characterizes electrical synapses?

    <p>Gap junctions directly connect the cytoplasm of adjacent cells</p> Signup and view all the answers

    What is the role of acetylcholine (ACh) at the neuromuscular junction?

    <p>Causing a change in membrane permeability at the motor end plate</p> Signup and view all the answers

    What terminates the signal of acetylcholine (ACh) at the neuromuscular junction?

    <p>Acetylcholinesterase breaking down ACh in the synaptic cleft</p> Signup and view all the answers

    During aerobic exercise, where does aerobic metabolism occur?

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

    What is the primary energy source for sustained energy output during moderate-intensity, long-duration activities?

    <p>Carbohydrates and fats</p> Signup and view all the answers

    Which type of muscle is regulated by both the autonomic nervous system and hormones?

    <p>Smooth muscle</p> Signup and view all the answers

    What is the primary neurotransmitter involved in the neuromuscular junction of skeletal muscle?

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

    Which type of muscle has branched cells with intercalated discs?

    <p>Cardiac muscle</p> Signup and view all the answers

    What is the byproduct of glycolysis that occurs without oxygen during anaerobic exercise?

    <p>Lactic acid</p> Signup and view all the answers

    What is the structural unit of muscle fibers, composed of actin and myosin filaments, Z-discs, I-band, A-band, and H-zone?

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

    What is the protein structure that bisects the sarcomere, acts as attachment points for thin actin filaments, and helps define the boundaries of the sarcomere?

    <p>Z-Disc (Z-Line)</p> Signup and view all the answers

    What is the region within the A-band where only myosin filaments are present, and there is no overlap with actin filaments?

    <p>H-Zone</p> Signup and view all the answers

    What is the giant protein spanning from the Z-disc to the M-line in a sarcomere, providing structural support and elasticity?

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

    What type of muscle is found in internal organs and structures, responsible for involuntary contractions, and mostly under autonomic nervous system control?

    <p>Smooth Muscle</p> Signup and view all the answers

    What is the primary neurotransmitter responsible for stimulating muscle contraction at the neuromuscular junction?

    <p>Acetylcholine (ACh)</p> Signup and view all the answers

    What is the primary change in ionic channels during the depolarization phase of a neuron's action potential?

    <p>Voltage-gated sodium channels open, allowing an influx of sodium ions into the neuron</p> Signup and view all the answers

    What triggers the rapid influx of sodium ions, creating the action potential in a neuron?

    <p>Receiving a stimulus</p> Signup and view all the answers

    What maintains the negative charge inside a neuron at rest?

    <p>Open ligand-gated potassium channels</p> Signup and view all the answers

    What characterizes electrical synapses?

    <p>Direct flow of ions through gap junctions between neurons</p> Signup and view all the answers

    What is the function of GABA as a neurotransmitter?

    <p>Inhibitory neurotransmission by hyperpolarizing postsynaptic neurons</p> Signup and view all the answers

    What happens to the membrane potential when a neuron undergoes depolarization?

    <p>The membrane potential becomes less negative (depolarized)</p> Signup and view all the answers

    What is the primary function of the synaptic cleft?

    <p>To allow neurotransmitters to diffuse and bind to receptors</p> Signup and view all the answers

    What is the role of acetylcholinesterase at the neuromuscular junction?

    <p>To break down acetylcholine in the synaptic cleft</p> Signup and view all the answers

    What characterizes electrical synapses?

    <p>Presence of gap junctions connecting adjacent cells</p> Signup and view all the answers

    Where are synaptic vesicles found?

    <p>Within the presynaptic terminal</p> Signup and view all the answers

    What is the primary responsibility of smooth muscle in the body?

    <p>To control involuntary movements of internal organs</p> Signup and view all the answers

    What are major neurotransmitters released into the synaptic cleft from synaptic vesicles?

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

    What is the primary neurotransmitter involved in the neuromuscular junction of skeletal muscle?

    <p>Acetylcholine (ACh)</p> Signup and view all the answers

    What is the byproduct of glycolysis that occurs without oxygen during anaerobic exercise?

    <p>Lactic acid</p> Signup and view all the answers

    What is the region within the A-band where only myosin filaments are present, and there is no overlap with actin filaments?

    <p>H-zone</p> Signup and view all the answers

    What happens to the membrane potential when a neuron undergoes depolarization?

    <p>It becomes less negative</p> Signup and view all the answers

    What causes depolarization and action potential propagation through T-tubules at the neuromuscular junction?

    <p>$Na^+$ influx into muscle fiber</p> Signup and view all the answers

    What characterizes electrical synapses?

    <p>Bidirectional flow of ions between cells</p> Signup and view all the answers

    During which type of exercise does glycolysis occur without oxygen, producing lactate as a byproduct?

    <p>Anaerobic exercise</p> Signup and view all the answers

    Which muscle type is regulated by both the autonomic nervous system and hormones?

    <p>Smooth muscle</p> Signup and view all the answers

    What is the primary energy source for sustained energy output during moderate-intensity, long-duration activities?

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

    Where does aerobic metabolism occur?

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

    What characterizes cardiac muscle?

    <p>Forms heart walls</p> Signup and view all the answers

    What happens to lactic acid during the post-exercise period?

    <p>Converted to pyruvate</p> Signup and view all the answers

    Study Notes

    • Aerobic exercise: relies on oxygen for energy production, increases oxygen consumption, primary energy sources are carbohydrates and fats, aerobic metabolism occurs in mitochondria
    • Increased heart rate and stroke volume: enhances cardiac output, oxygen-rich blood delivery
    • Respiratory rate and oxygen delivery: facilitates oxygen exchange and carbon dioxide removal
    • Sustained energy output: moderate-intensity, long-duration activities, glycogen and fatty acids utilized
    • Recovery period: gradual return to baseline, EPOC (excess post-exercise oxygen consumption) repays oxygen debt, energy stores are replenished
    • Anaerobic exercise: high-intensity, short-duration efforts, limited oxygen availability, glycolysis occurs without oxygen, producing lactate as a byproduct
    • Increased heart rate and breathing rate: to meet oxygen demands
    • ATP from phosphocreatine: rapid energy source for short bursts of activity
    • Lactic acid production: disruption of the energy balance and muscle fatigue
    • Lactate clearance: post-exercise period, lactate is cleared, converted to pyruvate, or used for energy
    • Replenishment of ATP and phosphocreatine: occurs during recovery, utilizing oxygen-dependent processes
    • Restoration of pH balance: disrupted by lactic acid during anaerobic activity, the body works to restore the balance
    • EPOC: less pronounced but still occurs, metabolic rate remains elevated during recovery

    Comparison of skeletal, cardiac, and smooth muscle:

    • Skeletal muscle: attached to bones, striated appearance, voluntary control, located in the somatic nervous system

    • Cardiac muscle: forms heart walls, striated appearance, intercalated discs, involuntary control, located in the autonomic nervous system

    • Smooth muscle: found in internal organs, non-striated appearance, spindle-shaped cells, involuntary control, regulated by the autonomic nervous system and hormones

    • Muscle fiber structure: skeletal muscle: long, multinucleated fibers with sarcomeres; cardiac muscle: branched cells with a single nucleus and intercalated discs; smooth muscle: spindle-shaped cells without sarcomeres

    • Neuromuscular junction: skeletal muscle: acetylcholine is the neurotransmitter with conscious control; cardiac muscle: less defined, acetylcholine and norepinephrine are neurotransmitters with autonomic control; smooth muscle: less defined, neurotransmitters are varied with autonomic control and hormonal regulation

    • Production of action potentials: skeletal muscle: voluntary control, action potentials generated by somatic motor neurons; cardiac muscle: involuntary control, action potentials generated by pacemaker cells; smooth muscle: involuntary control, action potentials generated by autonomic nerves and hormones.

    • Threshold and Action Potential: If membrane potential reaches a certain threshold, more voltage-gated sodium channels open, triggering a rapid influx of sodium ions and creating a spike called the action potential. Repolarization follows, restoring membrane potential with the help of voltage-gated potassium channels and the sodium-potassium pump.

    • Muscle Cell Excitation-Contraction Coupling: At the neuromuscular junction, acetylcholine release causes depolarization and action potential propagation through T-tubules, stimulating the sarcoplasmic reticulum to release calcium. Calcium binds to troponin, causing a conformational change and actin-myosin binding, leading to contraction. Calcium is then pumped back into the sarcoplasmic reticulum, removing calcium and preventing further contraction.

    • Skeletal Muscle: Attached to bones, responsible for voluntary body movements, and under conscious control.

    • Smooth Muscle: Found in internal organs and structures, responsible for involuntary contractions, and mostly under autonomic nervous system control.

    • Cardiac Muscle: Part of the heart, contracts rhythmically, and involuntarily, with some unique properties that allow it to generate its own rhythmic contractions.

    • Sarcomere: Structural unit of muscle fibers, composed of actin and myosin filaments, Z-discs, I-band, A-band, and H-zone.

    • Actin Filaments: Thin filament of globular actin monomers, anchored to Z-discs, and extends towards the center of the sarcomere.

    • Myosin Filaments: Thick filament of myosin molecules, located in the center of the sarcomere, and overlaps with actin filaments.

    • Z-Disc (Z-Line): Protein structure that bisects the sarcomere, acts as attachment points for thin actin filaments, and helps define the boundaries of the sarcomere.

    • I-Band (Isotropic Band): Region of the sarcomere containing only thin actin filaments and extending from the Z-disc towards the center of the sarcomere.

    • A-Band (Anisotropic Band): Central region of the sarcomere that contains thick myosin filaments and both overlapping actin and myosin filaments.

    • H-Zone: Region within the A-band where only myosin filaments are present, and there is no overlap with actin filaments.

    • M-Line: Protein structure at the center of the H-zone that helps stabilize and align myosin filaments.

    • Titin: Giant protein spanning the Z-disc to the M-line, providing structural support and elasticity to the sarcomere.

    • Aerobic exercise: relies on oxygen for energy production, increases oxygen consumption, primary energy sources are carbohydrates and fats, aerobic metabolism occurs in mitochondria

    • Increased heart rate and stroke volume: enhances cardiac output, oxygen-rich blood delivery

    • Respiratory rate and oxygen delivery: facilitates oxygen exchange and carbon dioxide removal

    • Sustained energy output: moderate-intensity, long-duration activities, glycogen and fatty acids utilized

    • Recovery period: gradual return to baseline, EPOC (excess post-exercise oxygen consumption) repays oxygen debt, energy stores are replenished

    • Anaerobic exercise: high-intensity, short-duration efforts, limited oxygen availability, glycolysis occurs without oxygen, producing lactate as a byproduct

    • Increased heart rate and breathing rate: to meet oxygen demands

    • ATP from phosphocreatine: rapid energy source for short bursts of activity

    • Lactic acid production: disruption of the energy balance and muscle fatigue

    • Lactate clearance: post-exercise period, lactate is cleared, converted to pyruvate, or used for energy

    • Replenishment of ATP and phosphocreatine: occurs during recovery, utilizing oxygen-dependent processes

    • Restoration of pH balance: disrupted by lactic acid during anaerobic activity, the body works to restore the balance

    • EPOC: less pronounced but still occurs, metabolic rate remains elevated during recovery

    Comparison of skeletal, cardiac, and smooth muscle:

    • Skeletal muscle: attached to bones, striated appearance, voluntary control, located in the somatic nervous system
    • Cardiac muscle: forms heart walls, striated appearance, intercalated discs, involuntary control, located in the autonomic nervous system
    • Smooth muscle: found in internal organs, non-striated appearance, spindle-shaped cells, involuntary control, regulated by the autonomic nervous system and hormones
    • Muscle fiber structure: skeletal muscle: long, multinucleated fibers with sarcomeres; cardiac muscle: branched cells with a single nucleus and intercalated discs; smooth muscle: spindle-shaped cells without sarcomeres
    • Neuromuscular junction: skeletal muscle: acetylcholine is the neurotransmitter with conscious control; cardiac muscle: less defined, acetylcholine and norepinephrine are neurotransmitters with autonomic control; smooth muscle: less defined, neurotransmitters are varied with autonomic control and hormonal regulation
    • Production of action potentials: skeletal muscle: voluntary control, action potentials generated by somatic motor neurons; cardiac muscle: involuntary control, action potentials generated by pacemaker cells; smooth muscle: involuntary control, action potentials generated by autonomic nerves and hormones.

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