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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
What is Basal Vasomotor Tone?
* 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
What is the Effect of decreased vasomotor tone?
* Vasodilation
27
What is the Effect of increased vasomotor tone?
* Vasoconstriction
28
What blood vessels have β2-adrenoceptors as well as α1-adrenoceptors?
* Skeletal Muscle * Myocardium * Liver
29
What type of adrenaline has a higher affinity for β2 adrenoceptors?
Circulating Adrenaline
30
What are the effects of activating α1- adrenoceptors on vascular smooth muscle?
* 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
What are the effects of activating β2-adrenoceptors on vascular smooth muscle?
* 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
What are some examples of metabolites? (4)
* Adenosine * K+ * H+ * Increased pCO2
33
What effect do local increases in metabolites have?
* 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
What type of tissue produces more metabolites?
* Active tissue produces more metabolites
35
Where are Baroreceptors found?
* 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
What does the ANS control in the CVS? What does it NOT control?
* Heart Rate * Force of contraction of heart * Peripheral resistance of blood vessels * The ANS does not initiate electrical activity in heart
37
Where is the Cardiovascular Centre in the Brain?
* Medulla oblongata * Located in brain stem
38
What does the Cardiovascular Centre in the Brain contain? (3)
* Cardioaccelerator Centre * Cardioinhibitor Centre * Vasomotor Centre
39
How are the changes in the state of the CVS are communicated to the brain? What receptors?
* Via afferent nerves * Baroreceptors (high pressure side of system) * Atrial receptors (low pressure side of system) * Alters activity of efferent nerve
40
Drugs acting on the ANS: Sympathomimetics
* α-adrenoceptor agonists * β-adrenoceptor agonists * Increases in heart rate, force of cardiac contraction, and blood pressure
41
Drugs acting on the ANS: Adrenoceptor Antagonists
* 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
Drugs acting on the ANS: Cholinergics
* 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
What is Propranolol (1962)?
* The first commercially successful beta- blocker
44
What is Propranolol used to Treat? (7)
* 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
Cells in the sinoatrial node (SA node) steadily depolarise toward threshold
* 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
Why do different tissues have different receptor subtypes?
* Allows for diversity of action * Selectivity of drug action
47
What do G protein-coupled receptors NOT have?
* No integral ion channel
48
What G-protein subtype corresponds to the a1-adrenoceptor?
Gq
49
What G-protein subtype corresponds to the a2-adrenoceptor?
Gi
50
What G-protein subtype corresponds to the β1-adrenoceptor?
Gs
51
What G-protein subtype corresponds to the β2-adrenoceptor?
Gs
52
What G-protein subtype corresponds to the M1-adrenoceptor?
Gq
53
What G-protein subtype corresponds to the M2-adrenoceptor?
Gi
54
What G-protein subtype corresponds to the M3-adrenoceptor?
Gq
55
Acronym for remembering G-protein subtype to corresponding adrenoreceptor (a-1,2 & β-1,2 & M-1,2,3)
KISS-KIK qiss-qiq
56
Adrenoceptors and muscarinic receptors are G-protein coupled receptors; how do they work? (5)
* 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
[Gs] G-Protein Subtype: Effector and Second Messenger
* Adenylyl cyclase (+) * cAMP ↑
58
[Gi] G-Protein Subtype: Effector and Second Messenger
* Adenylyl cyclase (-) --> cAMP ↓ * K+ channel (+) --> K+ ↓ * VOCC Ca2+ channel (-) --> Ca2+ ↓
59
[Gq] G-Protein Subtype: Effector and Second Messenger
* Phospholipase C (+) * DAG & IP3 → Ca2+ ↑

Cardiovascular System (19 decks)

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