Lecture 2 Neurotransmitters and Heart Anatomy Flashcards
What neurotransmitter do all preganglionic neurons release, in both SNS and PSNS:
Acetylcholine - they are cholinergic
What do PSNS postganglionic neurons release:
Acetylcholine - they are cholinergic
What do SNS postganglionic neurons release:
Norepinephrine - they are adrenergic
What is acetylcholine neutralised by?
Acetylcholinesterase
What is norepinephrine neutralised by?
Re-uptake, diffusion, degradation by monoamine oxidase (seconds)
You can also have epinephrine in the blood that is degraded by liver (minutes)
Acetylcholine released from PSNS nerves excites two receptors which are:
Nicotinic and Muscarinic
Where are nicotinic receptors found?
In synapses between pre- and post- ganglionic neurons, and at the neuromuscular junction
What type of receptor are nicotinic receptors?
Ligand gated ion channels
Where are muscarinic receptors found?
On all effector cells stimulated by PSNS postganglionic neurons
What type of receptor are muscarinic receptors?
G protein coupled receptors
Norepinephrine stimulates:
Alpha and beta adrenergic receptors
Where are alpha receptors located and what’s their purpose?
Blood vessels, vasoconstriction
What is the function of beta 1 and 2 receptors?
Beta 1 - increase in heart rate and contractility
Beta 2 - bronchial dilation, blood vessel dilation, glycogenolysis
What is the stress response, AKA fight or flight?
Mass sympathetic discharge to prepare body for vigorous activity
Define an artery
Muscular walled tubes, carrying oxygenated blood away from the heart
Define a vein
Thinner walled tubes carrying oxygen poor blood back towards the heart
Is the circulatory system akin to a parallel or series circuit?
What are the issues with the other type of circuit?
Parallel system
Series has high resistance, interdependence, decreased oxygenation
Mean diastolic and systolic pressure?
15-30mmHg
100-140mmHg
Name the two A-V valves and the other type of valve present:
A-V is tricuspid and mitral valves, other is semilunar valves
Purpose of cardiac frame?
Anchor and stabilise valves to the heart’s interior walls, while keeping valves in the round shape.
Also provides electrical insulation and separates atria from ventricles.
What are systole and diastole?
Systole contracting, diastole relaxing
How to calculate length of cardiac cycle from bpm?
60/bpm
Five brief steps to cardiac cycle:
- ventricles passively fill, atria prime
- ventricles are full, aortic and pulmonary arteries open
- 60% of blood ejected in systole
- ventricles relax, backpressure from arteries close semilunar valves
- diastole begins as atria and ventricles fill again
Define the Frank-Starling mechanism
Within physiological limits, the heart pumps all the blood that returns to it
(More the heart is stretched, the more force of contraction, more blood pumped into aorta)
