Pathophys Test 2

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Review blood flow through the heart and the mechanical events that take place. (p.2)
Preload
- End-diastolic volume
- Blood in each ventricle at end of diastole
- Normal = 110-120 mL
- Venous return to heart = major factor regulating end-diastolic volume
- Preload = degree of tension or distending force on ventricular muscle when it begins to contract
End-systolic volume
- Volume of blood in ventricle after contraction
- Usually 40-50 mL
Afterload
- Pressure or resistance against which ventricle has to pump
- Anything that increases pressure (aortic stenosis or peripheral vascular disease) increases afterload
Stroke Volume
- Amount of blood ejected from ventricles during contraction
- Usually 40-50 mL
Cardiac Output

(Stroke volume) x (Heart rate)
How is Frank-Starling mechanism related to cardiac output?

Greater stretch of muscle fibers = stronger contraction
How does the sympathetic nervous system influence heart rate and force of contraction? (p.6)
- Sympathetic nervous system – supplies both atria and ventricles
- Sympathetic stimulation –
- o Can increase cardiac output 2-3 fold
- o Increase rate and force of contractions
- o Norepinephrine – released from sympathetic nerve endings
- o Epinephrine – released from adrenal glands
- o Norepinephrine and epinephrine – enhance depolarization rate of SA node by increasing net flow of calcium ions into cells (slope of phase 4 depolarization)
How does the parasympathetic nervous system influence heart rate and force of contraction? (p.6)
- Parasympathetic nerves – primarily supply atria
- o Acetylcholine – released from vagus nerve endings of parasympathetic system
- o Slow HR and decrease force of contraction, especially atria
- o Acetylcholine – slows HR by increasing membrane permeability to K+ and increasing polarization
- - (hyperpolarized state)
Where would you find majority of alpha-adrenergic receptors? (p.6-7)

Located mainly in systemic blood vessels (arterioles) of skin, abdominal viscera, and skeletal muscle
Where would you find majority of beta-adrenergic receptors? (p.6-7)
- o Lungs (beta-2)
- o Heart (beta-1); (also beta-2 and alpha-1 in heart)
- o Skeletal muscles (beta-2)
- o Blood vessels (arterioles) of these organs (alpha-1, beta 2)
Know general effect of epinephrine on alpha-receptors and beta-receptors.
- o Excite alpha and beta receptors equally
- o Beta receptors tend to have lower threshold (increased sensitivity) for epinephrine than alpha receptors
- - especially on blood vessels in skeletal muscle
Know general effect of norepinephrine on alpha-receptors and beta-receptors.
- o Excites alpha receptors more than beta receptors
- o Alpha receptors less sensitive to epinephrine
- o Little effect on beta-2 receptors, but stimulate beta-1 receptors
If you gave a pharmacologic dose of norepinephrine, what would be the anticipated response of blood vessels?

Vasoconstriction

Author

cgordon05

12805

Card Set

Pathophys Test 2

Description

Cardiovascular Basic

Updated

2010-04-01T21:16:57Z

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