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Cardiovascular System > Lecture 8.2: The Autonomic Nervous System and the CVS > Flashcards

Lecture 8.2: The Autonomic Nervous System and the CVS Flashcards

1
Q

What is the Role of the Sympathetic Nervous System?

A

The sympathetic system controls “fight-or-flight” responses

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2
Q

What is the Role of the Parasympathetic Nervous System?

A

The parasympathetic system controls “rest and digest” or “feed and breed” responses

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3
Q

ANS vs SNS

A
  • Autonomic is involuntary
  • Somatic is voluntary
  • SNS consists of motor neurones that
    stimulate skeletal muscles
  • ANS consists of motor neurones that
    control smooth muscles, cardiac
    muscles, and glands
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4
Q

What is a Ganglion?

A
  • A collection of neuronal bodies found in
    the voluntary and autonomic branches
    of the peripheral nervous system (PNS)
  • Ganglia can be thought of as synaptic
    relay stations between neurones
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5
Q

Where is the Preganglionic Neurone of the Parasympathetic found? Where is the Postganglionic Neurone of the ANS found? What Neurotransmitter is released at the postganglionic synapse?

A
  • Preganglionic Neurone soma is usually
    in the brain-stem or sacral spinal chord
  • Postganglionic Neurone soma is
    usually in a ganglion near target organ
  • Acetylcholine or NO
  • Rest and digest response is activated
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6
Q

Where is the Preganglionic Neurone of the Sympathic found? Where is the Postganglionic Neurone of the ANS found? What Neurotransmitter is released at the postganglionic synapse?

A
  • Preganglionic Neurone soma is usually
    in the spine
  • Postganglionic Neurone soma is in a
    sympathetic ganglion located next to
    the spinal chord
  • Norepinephrine
  • Fight or flight response is activated
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7
Q

Where does the Sympathetic Nervous System originate?

A
  • Thoracolumbar origin
  • Preganglionic neurones arise from
    segments T1 to L2 (or L3)
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8
Q

Sympathetic Nervous System: Where do most preganglionic neurones synapse?

A
  • Most synapse with postganglionic
    neurones in the paravertebral chain
    of ganglia
  • Some synapse in a number of
    prevertebral ganglia (coeliac, superior
    mesenteric, inferior mesenteric ganglia)
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9
Q

Where does the Parasympathetic Nervous System originate?

A
  • Craniosacral origin
  • Preganglionic fibres travel in cranial
    nerves (III, VII, IX & X) or sacral
    outflow from S2-S4
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10
Q

Neurotransmitters and Receptors in the Sympathetic Nervous System: Preganglionic & Postganglionic Synapse

A
  • The preganglionic neurotransmitter is
    Acetylcholine
  • The preganglionic receptor is the
    nicotinic ACh receptor
  • The postganglionic neurotransmitter is
    noradrenaline (norepinephirine)
  • The postganglionic receptor is the
    (nor)adrenerig receptor
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11
Q

Neurotransmitters and Receptors in the Parasympathetic Nervous System: Preganglionic & Postganglionic Synapse

A
  • The preganglionic neurotransmitter is
    Acetylcholine
  • The preganglionic receptor is the
    nicotinic ACh receptor
  • The postganglionic neurotransmitter is
    also ACh
  • The postganglionic receptor is the
    muscarinic ACh receptors
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12
Q

Sympathetic innervation of the sweat
glands: Preganglionic & Postganglionic Synapse

A
  • The preganglionic neurotransmitter is
    Acetylcholine
  • The preganglionic receptor is the
    cholinerig ACh receptor
  • The postganglionic neurones release
    ACh
  • The postganglionic receptor is a
    muscarinic ACh receptors
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13
Q

What are Vagus Nerves?

A
  • Aka the vagal nerves
  • They are the main nerves of your
    parasympathetic nervous system
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14
Q

Parasympathetic Input to the Heart: Where do Preganglionic Fibres Synapse?

A

Synapse with postganglionic cells on epicardial surface or within walls of heart at SA and AV node

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15
Q

Parasympathetic Input to the Heart: What neurotransmitter do Postganglionic Fibres release? What receptor does this act on? What is the effect?

A
  • Postganglionic cells release ACh
  • Acts on M2-receptors
  • Decrease heart rate (-ve chronotropic
    effect)
  • Decrease AV node conduction velocity
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16
Q

Sympathetic Input to the Heart: Where do Postganglionic Fibres originate? What do they innervate?

A
  • Postganglionic fibres arise from T1-T4
    derived-parts of the sympathetic chain
  • Innervate SA node AV node and
    myocardium
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17
Q

Sympathetic Input to the Heart: What neurotransmitter do Postganglionic Fibres release? What receptor does this act on? What is the effect?

A
  • Release noradrenaline
  • Acts on β1 adrenoceptors
  • Increases heart rate (+ve chronotropic
    effect)
  • Increases force of contraction (+ve
    inotropic effect)
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18
Q

Effect of ANS on Pacemaker Potentials: Sympathetic
What is this effect mediated by?

A
  • Sympathetic activity increases slope
  • Sympathetic effect mediated by β1
    receptors, G-protein coupled receptors
    (Gs)
  • Increase cAMP → ligand to HCN
    channel speeds up pacemaker
    potential
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19
Q

Effect of ANS on Pacemaker Potentials: Parasympathetic
What is this effect mediated by?

A
  • Parasympathetic activity decreases
    slope of the pacemaker potential
  • Parasympathetic effect mediated
    by M2-receptors, G-protein coupled
    receptors (Gi)
  • Increase K+ conductance and
    decrease cAMP
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20
Q

How does noradrenaline increase the
force of contraction? (6)

A
  • NA acting on β1 receptors in
    myocardium causes an increase in
    cAMP → activates PKA
  • Phosphorylation of Ca2+ channels
    causes increased Ca 2+ entry during
    AP
  • Also increases Ca induced Ca release
    (CICR)
  • Increased uptake of Ca 2+ in
    sarcoplasmic reticulum
  • Increased sensitivity of contractile.
    machinery to Ca2+
  • Increased force of contraction
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21
Q

What type of innervation do most vessels receive? What is the exception?

A
  • Most vessels receive sympathetic
    innervation
  • Some specialised tissue eg erectile
    tissue have parasympathetic
    innervation
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22
Q

What type of receptors do most arteries and veins have?

A
  • α1-adrenoceptors
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23
Q

What type of receptors do coronary and skeletal muscle vasculature also have?

A
  • β2- receptors
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24
Q

What is Vasomotor Tone?

A

The end result of a complex set of interactions that control relaxation and contraction of blood vessels

25
Q

What is Basal Vasomotor Tone?

A
  • In quiescent skeletal muscle, the
    resistance arteries are partially
    constricted
  • The amount of VSM contraction
    necessary to maintain this partially
    constricted state is called basal
    vascular or vasomotor tone
26
Q

What is the Effect of decreased vasomotor tone?

A
  • Vasodilation
27
Q

What is the Effect of increased vasomotor tone?

A
  • Vasoconstriction
28
Q

What blood vessels have β2-adrenoceptors as well as α1-adrenoceptors?

A
  • Skeletal Muscle
  • Myocardium
  • Liver
29
Q

What type of adrenaline has a higher affinity for β2 adrenoceptors?

A

Circulating Adrenaline

30
Q

What are the effects of activating α1- adrenoceptors on vascular smooth muscle?

A
  • Activating α1-adrenoceptors causes
    vasoconstriction
  • Gq –> phospholipase C activation
    –>releases IP3
  • Increase in [Ca2+] in from stores and
    via influx of extracellular Ca2+
  • Lead to contraction of smooth muscle
31
Q

What are the effects of activating β2-adrenoceptors on vascular smooth muscle?

A
  • Activating β2 adrenoceptors causes
    vasodilation
  • Gs –> increases cAMP –> activates
    PKA
  • Opens a type of potassium channel
  • Phosphorylates and inactivates Myosin
    Light Chain Kinase (MLCK necessary
    for smooth muscle contraction)
  • Leads to relaxation of smooth muscle
32
Q

What are some examples of metabolites? (4)

A
  • Adenosine
  • K+
  • H+
  • Increased pCO2
33
Q

What effect do local increases in metabolites have?

A
  • Local increases in metabolites have a
    strong vasodilator effect
  • More important for ensuring adequate
    perfusion of skeletal and coronary
    muscle than activation of β2-receptors
34
Q

What type of tissue produces more metabolites?

A
  • Active tissue produces more
    metabolites
35
Q

Where are Baroreceptors found?

A
  • Carotid Sinus
  • Aortic Arch
  • Nerve endings in the carotid sinus and
    aortic arch are sensitive to stretch
  • Increased arterial pressure stretches
    these receptors
  • These afferent nerves link to the CVS
    control centre
36
Q

What does the ANS control in the CVS? What does it NOT control?

A
  • Heart Rate
  • Force of contraction of heart
  • Peripheral resistance of blood vessels
  • The ANS does not initiate electrical
    activity in heart
37
Q

Where is the Cardiovascular Centre in the Brain?

A
  • Medulla oblongata
  • Located in brain stem
38
Q

What does the Cardiovascular Centre in the Brain contain? (3)

A
  • Cardioaccelerator Centre
  • Cardioinhibitor Centre
  • Vasomotor Centre
39
Q

How are the changes in the state of the
CVS are communicated to the brain? What receptors?

A
  • Via afferent nerves
  • Baroreceptors (high pressure side of
    system)
  • Atrial receptors (low pressure side of
    system)
  • Alters activity of efferent nerve
40
Q

Drugs acting on the ANS: Sympathomimetics

A
  • α-adrenoceptor agonists
  • β-adrenoceptor agonists
  • Increases in heart rate, force of cardiac
    contraction, and blood pressure
41
Q

Drugs acting on the ANS: Adrenoceptor Antagonists

A
  • Reverse the natural cardiovascular
    effect
  • For example, if the natural activation of
    the α1-adrenergic receptor leads to
    vasoconstriction, an α1-adrenergic
    antagonist will result in vasodilation
42
Q

Drugs acting on the ANS: Cholinergics

A
  • Muscarinic agonists and antagonists
  • Reduction in heart rate, the contractile
    forces of the atria and the conduction
    velocity of both the sinoatrial and
    atrioventricular nodes
43
Q

What is Propranolol (1962)?

A
  • The first commercially successful beta-
    blocker
44
Q

What is Propranolol used to Treat? (7)

A
  • Tremors
  • Angina (chest pain)
  • Hypertension (high blood pressure) * Arrhythmias (heart rhythm disorders) * Other heart/circulatory conditions
  • Treat/Prevent Heart Attacks * Reduce the severity and frequency of
    migraine headaches
45
Q

Cells in the sinoatrial node (SA node) steadily depolarise toward threshold

A
  • Hyperpolarisation turns on a slow Na+
    conductance (If – funny current)
  • Hyperpolarisation-activated cyclic
    nucleotide gated (HCN) channels
  • Opening of Ca 2+ channels (T-type
    then L-type)
46
Q

Why do different tissues have
different receptor subtypes?

A
  • Allows for diversity of action
  • Selectivity of drug action
47
Q

What do G protein-coupled receptors NOT have?

A
  • No integral ion channel
48
Q

What G-protein subtype corresponds to the a1-adrenoceptor?

A

Gq

49
Q

What G-protein subtype corresponds to the a2-adrenoceptor?

A

Gi

50
Q

What G-protein subtype corresponds to the β1-adrenoceptor?

A

Gs

51
Q

What G-protein subtype corresponds to the β2-adrenoceptor?

A

Gs

52
Q

What G-protein subtype corresponds to the M1-adrenoceptor?

A

Gq

53
Q

What G-protein subtype corresponds to the M2-adrenoceptor?

A

Gi

54
Q

What G-protein subtype corresponds to the M3-adrenoceptor?

A

Gq

55
Q

Acronym for remembering G-protein subtype to corresponding adrenoreceptor (a-1,2 & β-1,2 & M-1,2,3)

A

KISS-KIK
qiss-qiq

56
Q

Adrenoceptors and muscarinic receptors are G-protein coupled receptors; how do they work? (5)

A
  • Agonist (ACh/NA) binds to specific.
    receptor
  • Bound receptor activates associated
    G-protein
  • Activated G-protein activates or
    inhibits an effector enzyme
  • Effector enzymes generate 2nd
    messenger molecules
  • 2nd messenger changes alter cellular
    biochemistry
57
Q

[Gs] G-Protein Subtype: Effector and Second Messenger

A
  • Adenylyl cyclase (+)
  • cAMP ↑
58
Q

[Gi] G-Protein Subtype: Effector and Second Messenger

A
  • Adenylyl cyclase (-) –> cAMP ↓
  • K+ channel (+) –> K+ ↓
  • VOCC Ca2+ channel (-) –> Ca2+ ↓
59
Q

[Gq] G-Protein Subtype: Effector and Second Messenger

A
  • Phospholipase C (+)
  • DAG & IP3 → Ca2+ ↑

Cardiovascular System (19 decks)

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