أسئلة المحاضرة الـ 12 فسيولوجي (قبل التعديل)
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Questions and Answers

What physiological response is associated with increased lipolysis?

  • Intestinal relaxation
  • Stimulation of insulin secretion
  • Nor-adrenaline release (correct)
  • Contraction of bladder
  • Which of the following actions does adrenaline NOT inhibit?

  • Lipolysis
  • Glycogenolysis (correct)
  • Platelet aggregation
  • Insulin secretion
  • What effect does the contraction of the splenic capsule have?

  • Relaxation of intestinal tract
  • Stimulation of liver functions
  • Increased nor-adrenaline release (correct)
  • Vasoconstriction of all vessels
  • Which of the following is a consequence of adrenergic sweating on palms?

    <p>Inhibition of insulin release</p> Signup and view all the answers

    Which process is NOT stimulated by adrenaline?

    <p>Insulin secretion</p> Signup and view all the answers

    What is the primary role of β1 receptors in the body?

    <p>Stimulate cardiac properties</p> Signup and view all the answers

    Which receptor type is involved in the process of lipolysis?

    <p>β3</p> Signup and view all the answers

    What effect does the activation of α receptors generally have on blood vessels?

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

    How do β2 receptors primarily affect smooth muscle in the bronchial walls?

    <p>Promote relaxation</p> Signup and view all the answers

    What is the primary second messenger for α receptors?

    <p>Inositol triphosphate (IP3)</p> Signup and view all the answers

    What role do β3 receptors play in body physiology?

    <p>Assist in lipolysis</p> Signup and view all the answers

    Which receptor type mainly induces positive feedback inhibition in cardiovascular responses?

    <p>α2</p> Signup and view all the answers

    The activation of β receptors generally leads to what effect in the cardiovascular system?

    <p>Increased heart rate and contractility</p> Signup and view all the answers

    Which neurotransmitter is primarily associated with the sympathetic nervous system?

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

    What percentage of adrenaline is released from the adrenal medulla?

    <p>80%</p> Signup and view all the answers

    Which of the following is NOT a synapse where noradrenaline is released?

    <p>Sweat glands</p> Signup and view all the answers

    What is the first step in the synthesis of noradrenaline in adrenergic nerve fibers?

    <p>Hydroxylation of Phenyl-alanine</p> Signup and view all the answers

    Where does the synthesis of dopamine occur primarily?

    <p>In the cytoplasm of chromaffin cells</p> Signup and view all the answers

    In which part of the body is adrenaline and noradrenaline stored in granules?

    <p>Adrenal medulla</p> Signup and view all the answers

    What happens to dopamine after it is synthesized in adrenergic nerve fibers?

    <p>It is transported into vesicles for further processing</p> Signup and view all the answers

    Which of the following substances has a much higher concentration in certain parts of the brain than noradrenaline?

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

    What triggers the release of neurotransmitters at the axon terminal?

    <p>Calcium influx</p> Signup and view all the answers

    Which of the following describes the effect of catecholamines binding to their receptors on the postsynaptic membrane?

    <p>Increases permeability to K and Cl</p> Signup and view all the answers

    What is the primary mechanism for removing catecholamines from the synaptic cleft?

    <p>Neuronal uptake</p> Signup and view all the answers

    What is the role of adenyl-cyclase in adrenergic transmission?

    <p>To convert ATP into C-AMP</p> Signup and view all the answers

    Which condition leads to depolarization when catecholamines bind to their receptors?

    <p>Increased permeability to Ca</p> Signup and view all the answers

    What enzyme is primarily involved in the destruction of catecholamines during neuronal uptake?

    <p>Mono-amino-oxidase (M.A.O)</p> Signup and view all the answers

    Where is catecholamine O-methyltransferase (C.O.M.T) primarily found?

    <p>In mitochondria of adrenergic fibers</p> Signup and view all the answers

    What is the difference in action between Norepinephrine and Adrenaline in adrenergic transmission?

    <p>Norepinephrine primarily activates alpha receptors, while adrenaline activates beta receptors.</p> Signup and view all the answers

    Which physiological response is associated with the contraction of the bladder and gastrointestinal tract?

    <p>Vascular contraction</p> Signup and view all the answers

    What effect does increased norepinephrine release have on lipolysis?

    <p>It enhances lipolysis</p> Signup and view all the answers

    Which of the following effects is associated with adrenergic sweating?

    <p>Adrenergic sweating on palms</p> Signup and view all the answers

    What is the effect of adrenaline and noradrenaline on platelet aggregation?

    <p>Inhibition of peripheral platelet aggregation</p> Signup and view all the answers

    Which physiological action is NOT stimulated by adrenaline based on its adrenergic activity?

    <p>Inhibition of liver activity</p> Signup and view all the answers

    What type of receptor primarily causes vasoconstriction of blood vessels?

    <p>α1 receptors</p> Signup and view all the answers

    Which of the following statements about β3 receptors is correct?

    <p>They are responsible for lipolysis in adipose tissue.</p> Signup and view all the answers

    Which mechanism of action is associated with α receptors?

    <p>Inhibition of adenyl cyclase</p> Signup and view all the answers

    What is the general effect of β2 receptor activation in effector organs?

    <p>Relaxation of smooth muscle</p> Signup and view all the answers

    In terms of adrenergic transmission, which of the following is a characteristic function of α2 receptors?

    <p>Induce negative feedback inhibition</p> Signup and view all the answers

    Which of the following is a primary physiological response of β1 receptor activation in the heart?

    <p>Increased cardiac output</p> Signup and view all the answers

    What secondary messenger is increased by activation of α receptors?

    <p>IP3</p> Signup and view all the answers

    Which type of adrenergic receptor is primarily located on pre-synaptic sympathetic nerve endings?

    <p>α2 receptors</p> Signup and view all the answers

    What effect does binding of catecholamines to postsynaptic receptors primarily have on cells?

    <p>Increased permeability to sodium and calcium ions</p> Signup and view all the answers

    What is the primary mechanism for the neuronal uptake of catecholamines?

    <p>Transport into adrenergic fibers</p> Signup and view all the answers

    What is the primary consequence of stimulation of adenyl-cyclase by catecholamines?

    <p>Conversion of ATP into cyclic AMP</p> Signup and view all the answers

    Which part of the body is responsible for the majority of catecholamine removal?

    <p>Nervous system</p> Signup and view all the answers

    Which mechanism accounts for the degradation of catecholamines primarily outside of neuronal tissues?

    <p>Oxidation by C.O.M.T.</p> Signup and view all the answers

    What ionic change generally leads to hyper-polarization when catecholamines bind to their receptors?

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

    Which enzyme primarily contributes to the breakdown of catecholamines that are taken back into the neuron?

    <p>Mono-amino-oxidase</p> Signup and view all the answers

    What is the typical distance across the synaptic cleft that catecholamines must cross to bind to their receptors?

    <p>10-30 nm</p> Signup and view all the answers

    Which of the following best describes the storage of noradrenaline in the adrenal medulla?

    <p>Stored in granules within chromaffin cells</p> Signup and view all the answers

    What is the composition of catecholamines in the adrenal medulla?

    <p>Noradrenaline (40%), Adrenaline (80%)</p> Signup and view all the answers

    Which step correctly follows the conversion of DOPA in the synthesis pathway of noradrenaline?

    <p>DOPA is decarboxylated to form Dopamine</p> Signup and view all the answers

    Which of the following statements about the location of noradrenaline release is FALSE?

    <p>Noradrenaline is released from skeletal muscle sites.</p> Signup and view all the answers

    Which enzyme is primarily important for the conversion of Tyrosine into DOPA?

    <p>Tyrosine hydroxylase</p> Signup and view all the answers

    What triggers the synthesis of dopamine in adrenergic nerve fibers?

    <p>Decarboxylation of DOPA</p> Signup and view all the answers

    Which neurotransmitter is produced in much higher concentrations in specific parts of the brain compared to noradrenaline?

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

    Which of the following chemicals does NOT represent a step in adrenergic neurotransmission synthesis?

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

    Study Notes

    Adrenergic Receptors

    • α receptors and β receptors are part of the sympathetic nervous system.
    • α receptors sub-types are α1 and α2.
    • β receptors sub-types are β1, β2, β3, β4, and β5.
    • β3 is linked to lipolysis in adipose tissue.
    • β4 and β5 are under research.

    Adrenergic Transmission

    • Noradrenaline is the chemical transmitter of the sympathetic nervous system.
    • Noradrenaline belongs to the catecholamine group, along with adrenaline and dopamine.
    • Sympathetic Post-ganglionic neurons release noradrenaline in all except sweat glands, skeletal muscle blood vessels, and sites of adrenaline release.
    • Adrenal Medulla is where adrenaline (80%) and noradrenaline (40%) are released.
    • Adrenaline and Noradrenaline are also released in some synapses of the CNS.

    Noradrenaline Synthesis

    • Synthesis begins in the cytoplasm and is completed in vesicles present in adrenergic nerve fibers.
    • The synthesis process starts with phenyl-alanine, which is converted to tyrosine via hydroxylation.
    • Tyrosine is converted to DOPA (Di-hydroxy phenyl-alanine) via hydroxylation.
    • DOPA is then converted to Dopamine via decarboxylation.
    • Dopamine is transported into vesicles of the nerve ending.
    • Dopamine is converted to Noradrenaline by adding an OH group.
    • In SRM and CNS neurons, Noradrenaline is further converted to adrenaline by adding a CH3 group.

    Noradrenaline Storage

    • Noradrenaline is mainly stored inside nerve terminals in vesicles.
    • Some noradrenaline exists free in the cytoplasm.
    • In adrenal medulla, adrenaline and noradrenaline are stored in the form of granules in chromaffin cells.

    Noradrenaline Release

    • When the action potential reaches the axon terminal, it opens voltage-gated Ca+2 channels.
    • Calcium influx increases intracellular Ca2+ levels.
    • Increased Ca2+ levels cause vesicles to move towards and fuse with the membrane.
    • Vesicles rupture and release their contents outside the nerve fiber.
    • Noradrenaline crosses the synaptic cleft (10-30 nm) and binds to its receptors on the effector organ.
    • Stimulation of sympathetic preganglionic nerve fibers on chromaffin cells in the adrenal medulla causes adrenaline and noradrenaline release.

    Noradrenaline Mechanism of Action

    • Catecholamines bind to receptors on the postsynaptic membrane and can increase permeability to Na and Ca, or increase permeability to K and Cl.
    • Increase in permeability to Na and Ca causes depolarization (stimulation).
    • Increase in permeability to K and Cl causes hyperpolarization (inhibition).
    • Catecholamines can also stimulate adenyl-cyclase, which converts ATP into C-AMP, initiating intracellular activities.

    Noradrenaline Removal

    • Noradrenaline is mainly removed by neuronal uptake (85%).
    • Extra-neuronal uptake accounts for 15% of removal.
    • Noradrenaline can be either stored or destroyed by the enzyme monoamine oxidase (MAO) in neuronal uptake.
    • Noradrenaline is destroyed by catechol-O-methyltransferase (COMT) in extra-neuronal uptake.
    • A very small amount of noradrenaline is excreted in the urine.

    Noradrenaline Receptor and Action

    • α receptors are mainly excitatory.

    • β receptors are mainly inhibitory.

    • α1 receptors:

      • vasoconstriction of blood vessels
      • contraction of piloerector muscles
      • contraction of splenic capsule
      • contraction of seminal vesicle and ejaculatory duct
      • contraction of bladder and GIT sphincters
      • adrenergic sweating on palm
      • inhibition of insulin secretion
    • α2 receptors:

      • presynaptic negative feedback inhibition of noradrenaline release
      • increased renin secretion
      • central nervous system inhibition
    • β1 receptors:

      • increased heart rate, contractility, and conduction velocity
      • stimulation of liver and muscle glycogenolysis
      • increased blood fibrinogen level
      • peripheral platelet aggregation
    • β2 receptors:

      • intestinal relaxation
      • bladder relaxation
      • bronchodilation
      • smooth muscle relaxation in skeletal muscle blood vessels.
      • smooth muscle relaxation in the bronchial wall
      • smooth muscle relaxation in the bladder wall
      • smooth muscle relaxation in the GIT wall
      • increased lipolysis
      • decreased platelet aggregation
    • β3 receptors:

      • lipolysis
    • β4 and β5 receptors are under research.

    • Adrenaline and Noradrenaline are equally effective agonists for both α and β receptors.

    • Adrenaline has higher sensitivity with β receptors.

    • Noradrenaline has higher sensitivity with α receptors.

    Adrenergic Receptors

    • Alpha receptors: divided into alpha 1 and alpha 2 subtypes
    • Beta receptors: divided into beta 1, beta 2, beta 3, beta 4, and beta 5 subtypes
    • Beta 3 receptors are found in adipose tissue and are responsible for lipolysis (breakdown of fat)
    • Beta 4 and beta 5 receptors are currently under research

    Adrenergic Transmission

    • Alpha receptors
      • Located on postsynaptic membranes of effector organs (stimulates effect)
      • Located on presynaptic sympathetic nerve endings and ganglion cells (inhibits effect)
      • Activation of protein G leads to increased intracellular IP3 and Ca
      • Primarily excitatory:
        • Vasoconstriction (narrowing of blood vessels)
        • Contraction of piloerector muscles
    • Beta receptors
      • Located on postsynaptic membranes of effector organs
      • Activation of protein G leads to stimulation of adenyl cyclase, which increases cAMP levels
      • Primarily excitatory:
        • Increased cardiac properties (heart rate, contractility, conduction)
        • Smooth muscle relaxation in blood vessels, bronchial walls, bladder, and gastrointestinal tract walls
      • Primarily inhibitory:
        • Smooth muscle relaxation

    Noradrenaline

    • Chemical transmitter of the sympathetic nervous system, a member of the catecholamine family (which also includes adrenaline and dopamine)
    • Released from:
      • All sympathetic postganglionic fibers (except sweat glands, skeletal muscle blood vessels, sites of adrenaline release)
      • Adrenal medulla (80% adrenaline, 40% noradrenaline)
      • Some synapses in the central nervous system (CNS)
    • Synthesized in the liver through hydroxylation of phenylalanine to tyrosine
    • Synthesized in the axoplasm of adrenergic nerve fibers through hydroxylation of tyrosine to DOPA (dihydroxyphenylalanine)
    • Decarboxylation of DOPA produces dopamine
    • Dopamine is transported into vesicles in nerve endings: hydroxylation converts dopamine into noradrenaline
    • Adrenaline is formed from noradrenaline through methylation in the SRM and CNS neurons

    Storage and Release of Noradrenaline and Adrenaline

    • Primarily stored inside nerve terminals in vesicles
    • Some are free in the cytoplasm
    • In the adrenal medulla, adrenaline and noradrenaline are stored in the form of granules inside chromaffin cells
    • Action potential reaches the axon terminal → opens voltage-gated Ca+2 channels → Ca2+ influx → increases Ca2+ levels → moves vesicles toward the membrane and fuses with it → vesicles rupture and release their content outside the nerve fiber → noradrenaline crosses the synapse and binds to receptors on the effector organs
    • Stimulation of sympathetic preganglionic nerve fibers relaying onto chromaffin cells in the SRM causes adrenaline and noradrenaline release

    Mechanism of Action of Catecholamines

    • Catecholamines bind to receptors on the postsynaptic membrane, leading to:
      • Increased permeability to sodium (Na) and calcium (Ca) ions
      • Sodium and calcium influx → depolarization (stimulation)
      • Increased permeability to potassium (K) and chloride (Cl) ions
      • Potassium efflux and chloride influx → hyperpolarization (inhibition)
      • Stimulation of adenyl cyclase → conversion of ATP into cAMP (which initiates intracellular activities)

    Removal of Catecholamines

    • Neuronal uptake: responsible for removing 85% of catecholamines; either stored or destroyed by MAO
    • Extra-neuronal uptake: responsible for removing 15% of catecholamines; destroyed by COMT
    • Excretion in urine: very small amount

    Receptors

    • Respond to adrenaline and noradrenaline
    • Alpha 1 receptors
      • Increased renin secretion
      • Intestinal and bladder relaxation
      • Contraction of splenic capsule
      • Contraction of seminal vesicle and ejaculatory duct
      • Contraction of bladder and GIT sphincters
      • Adrenergic sweating on the palms
      • May be inhibitory
        • Inhibition of insulin secretion
    • Alpha 2 receptors
      • Presynaptic
        • Negative feedback inhibition of norepinephrine release
      • Postsynaptic
        • Central nervous system (CNS) inhibition
        • More sensitive to norepinephrine
    • Beta 1 receptors
      • Increased heart rate, contractility, and conduction
      • Increased lipolysis
      • Stimulation of liver and muscle glycogenolysis
      • Increased blood fibrinogen levels
    • Beta 2 receptors
      • Vasodilation (widening of blood vessels)
      • Bronchodilation (relaxation of airways)
      • Decreased platelet aggregation
      • Inhibition of insulin secretion
      • Intestinal relaxation
      • More sensitive to adrenaline
    • Beta 3 receptors
      • Located in adipose tissue
      • Increased lipolysis
      • Stimulation of insulin secretion
      • Decreased lipolysis
    • **Note: Beta 4 and Beta 5 receptors are under research ***

    Agonists

    • Adrenaline and Noradrenaline: equally effective on all receptors
    • Adrenaline: more sensitive to beta 2 receptors
    • Noradrenaline: more sensitive to alpha 2 receptors

    Monoamine Oxidase (MAO)

    • Located primarily in mitochondria of adrenergic fibers, liver, and kidneys
    • Responsible for oxidizing catecholamines

    Catechol O-Methyltransferase (COMT)

    • Located in all tissues, especially the kidney and brain
    • Responsible for methylating catecholamines

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