Pharmacology

Question 1

describe the mechanism by which beta 1 adrenoceptors become activated: the sympathetic system

Answer 1

noradrenaline and adrenaline activate the b1 receptors in nodal cells and myocardial cells.
coupling through G proteins activate adenylyl cyclase to increase cAMP which causes an increase in the L type calcium channels which results in an increases the calcium coming in, triggering the Sarcoplasmic reticulum calcium injection

Question 2

Name effects of sympathetic system on HR, contractility, conduction and automaticity

Answer 2

HR increase
Contract increase
Conduction INCREASE
Automaticity increase

Question 3

What is an increase in HR mediated by and what is it due to?

Answer 3

mediated by SA node and due to increase in slope of the pacemaker potential

Question 4

What is an increase in contractility due to?

Answer 4

an increase in phase 2 of cardiac potential in atrial and ventricular myocytes and enhanced Ca2+ influx

Question 5

Describe the process by which the parasympathetic system monitors the heart

Answer 5

acetylcholine (post ganglionic transmitter) activates M2 muscarinic cholinoceptors, largely in nodal cells which triggers the recruitment of Potassium channels decreasing the slope resulting in slower HR but no effect on the contraction of the heart

Question 6

Describe the effect of the parasympathetic system on HR, contractility, AV node conductance

Answer 6

Decrease HR
decrease Contractility
Decrease AV node conductance

Question 7

Parasympathetic/sympathetic stimulation may cause arrhythmias to occur in the atria?

Answer 7

parasympathetic

Question 8

What may be used in atrial flutter or AF to suppress impulse conduction through the AV node?

Answer 8

vagal manoeuvres

Question 9

name some vagal manoeuvres

Answer 9

aortic baroreceptors, massage carotid bifurcation

Question 10

what is the function of the Ivabradine drug?

Answer 10

anti anginal drug

Question 11

p: Ivabradine

Answer 11

• Selective blocker of HCN leading to greater channel slows HR by decreasing the slope of the pacemaker potential
  By decreasing the amount of effective potassium channels slowing everything down

Question 12

Describe excitation contraction in cardiac muscle: contraction

Answer 12

• Opening of Ca++ L type channels during phase 2 of action potential
  Ca++ influx into cytoplasm
  Calcium release from Sarcoplasmic reticulum (CICR calcium induced calcium release)
  Ca++ binds to troponin C and shifts tropomyosin out of the actin cleft > so cross bridge formation resulting in contraction.

Question 13

Describe excitation contraction in cardiac muscle: relaxation

Answer 13

• Repolarisation in phase 3 to 4, so L type channels close
• Ca++ influx ceases, NCX1 causes Ca++ efflux
• Sarcoplasmic Reticulum ceases to release Ca++
• Ca++ dissociates from troponin C = broken cross bridges between actin and myosin so relaxation

Question 14

describe the mechanism by which B1-adrenoceptors activation increases the force of contraction on the heart

Answer 14

• B1 activation activates adenylyl cyclase which converts ATP to cAMP
  leads to phosphorylation by PKA which initiates L type channels, that enhance contractility.

Question 15

Name some things B1-adrenoceptor agonists generally do to the heart and body?

Answer 15

increase:
HR
Force
Rate
CO2 AND O2 consumption

Decreases:
cardiac efficacy
Arrhythmias

Question 16

What is dobutamine used for?

Answer 16

acute Heart Failure

Question 17

is dobutamine A/B selective?

Answer 17

Beta

Question 18

What way is dobutamine administered and half life?

Answer 18

IV and 2 min

Question 19

What is adrenaline used for?

Answer 19

anaphylaxis

cardiac arrest

Question 20

Is adrenaline A/B ant/agonist?

Answer 20

a or beta agonist

Question 21

How is adrenaline administered and half life?

Answer 21

IM, SC, IVE

2 min

Question 22

Name one other B1-adrenoceptor agonist used on the heart and its use?

Answer 22

noradrenaline

the rate and force of contraction of the heart.

Question 23

What is the general effect of B1 RECEPTOR ANATGONISTS?

Answer 23

Blocks B adrenoceptors

non-selectively or selectively

Question 24

name non selective B antagonists

Answer 24

B 1+2 propanolol

Question 25

name the selective B1 antagonists

Answer 25

atenolol, bisoprolol, metoprolol

Question 26

how do B1 antagonists help arrhythmias?

Answer 26

decrease excessive sympathetic drive (in stress or emotion), delay conduction through AV node restore sinus rhythm (AF and SVT)

Question 27

how do B1 antagonists help angina?

Answer 27

can be alternate 1st line to CCB

Question 28

how do B1 antagonists help HF?

Answer 28

paradoxical but low doses reduce excessive sympathetic drive not in short term, wait a couple of days

Question 29

how do B1 antagonists help hypertension?

Answer 29

only if comorbidities (angina) present

Question 30

name some adverse effects of b adrenoceptor antagonists

Answer 30

Bronchospasm (asthma)
can aggravate cardiac failure
bradycardia, hypoglycaemia (release of glucose in liver controlled by B2), fatigue
cold extremities

Question 31

Name the Muscarinic receptor agonist

Answer 31

Atropine

Question 32

what is atropine used for?

Answer 32

Used 1st line in severe or symptomatic bradycardia (following MI).

Question 33

How does atropine work?

Answer 33

Increase in HR (blocks parasympathetic stimulation), No effect on BP (resistance vessels lack parasympathetic innervation).

Question 34

p: Inotropic agents eg Digoxin in therapy of heart failure

Answer 34

Digoxin inhibits Na+/K+ ATPase,
less Na+ and Ca++ is exchanged (increasing Intracellular Ca++),
greater storage of Ca++ in SR,

Question 35

How is Digoxin used?

Answer 35

IV in acute HF, orally in chronic HF, especially HF with AF

Question 36

name the adverse effects of Digoxin

Answer 36

Depression of AV node (heart block), Arrhythmias
nausea/ vomiting
diarrhoea
disturbs colour vision yellow vision.