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Cardiovascular System > Session 4 - CNS and ANS > Flashcards

Session 4 - CNS and ANS Flashcards

1
Q

What are ganglia?

A

-Collections of cell bodies within the PNS

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2
Q

What is a neuro-effector junction?

A

-A synapse between a post-ganglionic neurone and an effector cell

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3
Q

Where do the sympathetic and parasympathetic nervous systems leave the spinal cord?

A
  • Sympathetic from Thoracic and Lumbar regions

- Parasympathetic from Cranial and Sacral regions

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4
Q

Which division of the ANS has long pre-panglionic fibres and short postganglionic fibres?

A

-Parasympathetic

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5
Q

Which division of the ANS has short pre-ganglionic fibres and long post-ganglionic fibres?

A

-Sympathetic

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6
Q

Where are most of the ganglia of the sympathetic nervous system located?

A

-Paravertebral chain

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7
Q

Where are most of the ganglia of the parasympathetic nervous system located?

A

-Close to or within their effector structures

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8
Q

Which fibres and of which divisions have Ach as its neurotransmitter?

A

-Preganglionic fibres of both divisions and post ganglionic of parasympathetic

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9
Q

What is the neurotransmitter of the post-ganglionic fibres of the sympathetic nervous system?

A

-Noradrenaline

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10
Q

What receptors are on post-ganglionic cell bodies?

A

-Nicotinic Ach receptors

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11
Q

What receptors are found on effector cells of the parasympathetic system?

A

-Muscarinic 1,2,3 Ach R

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12
Q

What receptors are found on the effector cells of the sympathetic nervous system?

A

-a and b adrenergic receptors

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13
Q

Which functions are an exception to the sympathetic nervous system?

A

-Perspiration and Ejaculation which use Ach and muscarinic receptors

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14
Q

What type of receptor are muscarinic receptors?

A

-GPCR

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15
Q

What type of receptors are nicotinic receptors?

A

-Fast-acting ion channels

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16
Q

What type of receptors are adrenoreceptors?

A

-GPCR

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17
Q

How does the sympathetic innervation of the adrenal medulla differ from the rest?

A

-Has specialised post-ganglionic neurones called chromaffin cells which secrete adrenaline when stimulated

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18
Q

Whyat effect does the ANS have on the CVS?

A

-Controls HR, force of contraction and vasomotor tone

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19
Q

Through what nerve does parasympathetic input to the heart occur?

A

-Vagus

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20
Q

What neurotransmitter and receptors does the parasympathetic NS use to innervate the heart?

A
  • Ach

- M2 receptors

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21
Q

What effect does the parasympatheric nervous system have on the heart?

A
  • Decrease rate

- Decrease AV node conduction velocity

22
Q

What structures does the sympathetic NS innervate in the heart?

A
  • SA node
  • AV node
  • Myocardium
23
Q

What receptors does the sympathetic nervous system act on in the heart?

A

-B1-adrenoreceptors

24
Q

What effect does the sympathetic nervous system have on contraction?

A
  • Increase rate

- Increased force

25
How does the sympathetic NS increase HR?
- Increases depolarising slope of funny current by stimulating b1-adrenoreceptors - b1-adrenoreceptors -> Gas dissociates and activates adenyl cyclase -> this increases cAMP production in the cell which is a cyclic nucleotide - cAMP activates more HCN channels increasing the speed of depolarisation, with a resulting increase in hyperpolarisation both increasing the HR
26
How does the parasympathetic NS decrease HR?
- Ach stimulates M2 receptors which have an associated Gai subunit - Gai inhibits adenyl cyclase which decreases cAMP -> decreased activation of HCN
27
How are the divisions of the ANS arranged?
-Two neurones arranged in series with the pre-gangionic neurone having its cell body in the CNA and the post-ganglionic cell neurone having its body in the PNS
28
The parasympathetic NS increases the conductance of K+ in cels, so why is there an overall decrease in HR?
-The decrease in cAMP has a greater effect than the increased hyperpolarisation caused by increased K conduction
29
How does NA (from SNS) increase the force of contraction of the heart?
-NA binds to b1-adrenoreceptors -This activates the GPCR and Gas dissociates from the G protein and activates AC. This increases the production of cAMP with a resultant activation of PKA -PKA results in the phosphorylation, and thus opening of Ca channels, causing increased entry of Ca during the AP -NA increases the uptake of Ca into the SR -> more to be released -NA causes increased sensitivity of contractile machinery to Ca These cause an increased force of contraction
30
Which type of innervation do most blood vessels get? What is the exception to this?
- Sympathetic | - Erectile tissue which gets parasympathetic
31
What type of adrenoreceptor do most arteries and veins have?
-a1-adrenoreceptors
32
Which blood vessels have a1 and b2 adrenoreceptors?
- Coronary vessels | - Skeletal muscle vasculature
33
What is the result of a decreased sympathetic output to blood vessels?
-Vasodilatation
34
For those vessels which have B2 and a1-adrenoreceptors, which neurotransmitter does each of them respond to?
- a1-> circulating noradrenaline | - b2->circulating adenaline
35
Why can adrenaline cause vasodilation of some vessels?
- Adrenaline acts on b2-adrenoreceptors in coronary or skeletal musche vessels - B2 adrenoreceptor has Gas-type gprotein - Gas dissociates and activates adenyl cyclase - Increased cAMP production - Increased activation of PKA which Increases conduction of K+ - Inhibits MLCK and causes reduced contraction of smooth muscle as myosin head not phosphorylated
36
How does noradrenaline cause vasoconstriction of vessels?
- NA acts on a1-adrenoreceptor - a1 has Gaq gprotein, gaq dissociates and activates PLC - PLC cleaves PIP2 into IP3 and DAG - IP3 acts on IP3 receptors on SR causing increased calcium release -> contraction can then occur - DAG stimulates PKC which inhibits MLCP further influencing contraction as inhibition of MLCP causes increased phosphorylation of MLC
37
What role do local metabolites have in vasodilation?
- Metabolising tissues produce metabolites such as adenosine, H+, K+,increased pCO2 - This local accumulation has a strong vasodilator effect
38
Why is metabolites causing vasodilation so important?
-Allows supply to meet demand ensuring adequate perfusion as highly active tissues will produce lots of metabolites -> high vasodilatation -> increasd bloodflow
39
Where are baroreceptors?
-Aorta and coronary sinus
40
What are baroreceptors?
- Nerve endings which are sensitive to stretch detect increases in arterial pressure and relay the information through afferent fibres to the medulla - The medulla can then cause bradycardia and vasodilation through efferent pathways to decrease bp
41
What are sympathomimetics?
-Drugs which are a and b adrenoreceptor agonists, and thus mimic the effect of the sympathetic nervous system
42
How does the administration of adrenaline restore function in cardiac arrest?
-Pharmalogical levels of adrenaline act on a1-adrenoreceptors on vessels causing vasoconstriction and increasing cardiac output
43
-What is dobutamine?
-A b1-agonist which is used in cardiogenic shock to increase the force and rate of contraction
44
How does adrenaline treat anaphylactic shock?
- During anaphylaxis there is widespread vasodilation | - Adrenaline acts on a1-adrenoreceptors and causes vasoconstriction through Gaq-> PLC-> IP3-> increased Ca-> contraction
45
Why is salbutamol used to treat asthma?
- Activates b2-adrenoreceptors - Gas dissociates and activates adenyl cyclase - Increased cAMP-> increased PKA - PKA phosphorylates MLCK leading to its inhibition - Myosin not phosphorylated - Contraction cannot occur - Bronchi relax
46
How can a-adrenoreceptor antagonists be used in the treatment of hypertension?
- Antagonist binds to a1-adrenoreceptor and prevents NA binding - Prevents vasoconstriction so vasodilatation occurs - Lowers pressure
47
Name an anti-hypertensive agent which works as an a-adrenoreceptor antagonist
-Prazosin
48
What is propranolol?
-Non-selective Breceptor antagonist which slows HR and reduces force of contraction by blocking b1 receptors, but also causes bronchoconstriction by blocking B2 receptors in the bronchi
49
What is atenolol?
-Selective b1 receptor antagonist
50
What is pilocarpine?
-Muscarinic agonist used in the treatment of glaucoma as it activates constrictor pupillae muscle
51
What is atropine?
-Muscurinic antagonist used to increase HR by blocking the parasympathetic innervation of the heart through M2 receptors

Cardiovascular System (19 decks)

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