Autonomic Nervous System and the Heart Flashcards
Cardiac Output = ?
Cardiac Output = Stroke Volume x Heart Rate
What is the average intrinsic rate of the SA Node?
100 AP/min
What is the average heart rate for the average human?
Males - 70 beats/min
Females - 80 beats/min
True/False - The parasympathetic nervous system is the rest and digest stimulus pathway of the body
True
Parasympathetic - Rest and Digest
Sympathetic - Fight or Flight
PNS molecule and receptor
Molecule - Acetylcholine (ACh) from the postganglionic neuron
Receptor - Muscarinic receptors
SNS molecule and receptor
Molecule- Norepinephrine (from postganglionic neuron) and Epinephrine (from adrenal medulla respectively)
Receptor - Beta 1 (B1) Adrenergic receptors
Where are the SNS and PNS receptors located in the heart?
- the SA node, AV Node, and ventricular muscle
- notably large amount of B1 adrenergic receptors in ventricular muscle
What do the muscarinic receptors do?
- Increase K permeability
- Decrease Na and Ca permeability
- Result of this is that the stroke volume is lower due to weaker contractions
What do the Beta 1 adrenergic receptors do?
- Increase Na and Ca permeability
- Triggers pathway that opens SR Ca channels
- Stronger contractions so larger stroke volumes
End Diastolic Volume
Amount of blood in ventricle after atrial systole before ventricular systole
- point at which volume of blood in the ventricle is the highest
End Systolic Volume
Amount of blood in ventricle after ventricular systole
- point at which volume of blood in ventricle is the lowest
Stroke Volume = ?
EDV - ESV
Factors controlling stroke volume
1) Autonomic Nervous System
2) Preload on Heart
How does the ANS control stroke volume?
SNS - higher stroke volume due to stronger contractions
PNS - lower stroke volume due to weaker contractions
How does preload on heart affect stroke volume?
Increase in Preload = Increased Stroke volume
- Preload increase = EDV increase
- EDV increase due to increased venous return
