Exam 2- Chapter 14 Flashcards
What does cardiac output mean?
Volume of blood pumped each minute by each ventricle
What is the equation for cardiac output?
cardiac output = stroke volume X heart rate
(ml/minute) (ml/beat) (beats/min)
What is the average heart rate?
70 bpm
What is the average stroke volume?
70−80 ml/beat
What is the average cardiac output?
5,500 ml/minute
Regulation of Cardiac Rate: When does spontaneous depolarization occur at SA node?
when HCN channels open, allowing Na+ in
Regulation of Cardiac Rate: What keeps HCN channels open? What does this do?
- Sympathetic norepinephrine (vagus nerve) and adrenal epinephrine
- Increase heart rate
Regulation of Cardiac Rate: what opens K+ channels? What does this do?
- Ach
2. Slows heart rate
Regulation of Cardiac Rate: What is the regulation of cardiac rate controlled by?
Cardiac center od the medulla oblongata
What are the 3 variables that are responsible for regulation of stroke volume?
- End diastolic volume (EDV)
- Total peripheral resistance
- Contractility
What is the End diastolic volume (EDV)? What is it sometimes called? How are stroke volume and EDV related?
- Volume of blood in the ventricles at the end of diastole
- Preload
- Stroke volume increases with increased EDV
What is the Total peripheral resistance? How are stoke volume and Total peripheral resistance related?
- Frictional resistance in the arteries
2. Inversely related to stroke volume
What is Contractility? How are stoke volume and contractility related?
- strength of ventricular contraction
2. Stroke volume increases with contractility.
State the Frank-Starling law.
Increased EDV results in increased contractility and thus increased stroke volume
Intrinsic control of contraction strength:
- What is this due to? Explain.
- What is that (^^) due to?
- Myocardial stretch
- Increased EDV stretches the myocardium, which increases contraction strength.
- Due to increased myosin and actin overlap and increased sensitivity to Ca2+ in cardiac muscle cells
Sympathetic norepinephrine and adrenal epinephrine can increase contractility by doing what?
by making more Ca2+ available to sarcomeres.
What is EDV controlled by?
Factors that affect venous return
1. Total blood volume 2. Venous pressure
What factors affect venous return?
- Total blood volume
2. Venous pressure
Veins are compliant. What does that mean?
stretch at a given pressure
Veins or Arteries:
- What holds more blood?
- What maintains a higher pressure?
- What maintains a lower pressure
- Veins
- Arteries
- Veins
How much of our body water is found within the cells?
2/3
Of the remaining 1/3 of our bodies water found outside the cells, how much exist in interstitial spaces? and how much is in blood plasma?
- 80%
2. 20%
What controls the movement of water between the interstitial spaces and the capillaries, affecting blood volume?
Osmotic forces
Besides osmotic forces, what also plays a role in blood volume?
- Urine formation
2. Water intake (drinking)
Tissue/Capillary Fluid Exchange: What is net filtration pressure?
Hydrostatic pressure of the blood in the capillaries - Hydrostatic pressure of the fluid outside the capillaries
Tissue/Capillary Fluid Exchange: What is the net filtration pressure at the arteriole end? venule end?
- 36 mmHg @ arteriole end
2. 16 mmHg @ venule end
Tissue/Capillary Fluid Exchange: what is colloid osmotic pressure due to?
due to proteins dissolved in fluid
Which has a higher colloid osmotic pressure: blood plasma or interstitial fluid? What is difference called? Give the number value. Where does the favor movement into?
- Blood plasma
- Oncotic pressure
- 25 mmHg
- Capillaries
Tissue/Capillary Fluid Exchange: what are starling forces?
combination of hydrostatic pressure and oncotic pressure that predicts movement of fluid across capillary membranes
Tissue/Capillary Fluid Exchange- Starling Forces: what is the equation of fluid movement?
(pc + πi) - (pi + πp)
fluid out fluid in
(pc + πi) - (pi + πp)
fluid out fluid in
- What does pc mean?
- What does πi mean?
- What does pi mean?
- What does πp mean?
- Hydrostatic pressure in capillary
- Colloid osmotic pressure of interstitial fluid
- Hydrostatic pressure of interstitial fluid
- Colloid osmotic pressure of blood plasma
What specific part of the capillary membranes do starling forces predict?
predict the movement of fluid into the capillaries at the arteriole end and out of the capillaries at the venule end
What is an edema?
Excessive accumulations of interstitial fluids
What can an edema be a result of? (7 possibilities)
- High arterial blood pressure
- Venous obstruction
- Leakage of plasma proteins into interstitial space
- Myxedema (excessive production of mucin in extracellular spaces caused by hypothyroidism)
- Decreased plasma protein concentration
- Obstruction of lymphatic drainage – by parasites
- Removal of lymphatic tissue
The formation of urine begins with what?
filtration of fluid through capillaries in the kidneys called glomeruli
How much filtrate in L, is moved across the glomeruli per day? How much is actually removed through urine? Where does the rest go?
- 180 L of filtrate is moved across the glomeruli per day
- 1.5 L is actually removed as urine
- The rest is reabsorbed into the blood
What is the amount of filtrate reabsorbed into the blood controlled by and in response to what?
several hormones in response to the body’s needs
Antidiuretic hormone (ADH):
- What is it produced by?
- When is it released?
- What does it stimulate?
- Hypothalamus
- When osmoreceptors in the hypothalamus detect increased plasma osmolarity
- ADH stimulates water reabsorption
Plasma osmolarity can increase due to what?
excessive salt intake or dehydration
Increased plasma osmolarity also increases what?
Thirst
Aldosterone:
- What is it secreted by?
- When is it secreted?
- What does stimulate?
- What system is it regulated by?
- Adrenal cortex indirectly
- When blood volume and pressure are reduced
- Stimulates reabsorption of salt in kidneys
- Regulated by renin-angiotensin-aldosterone system
Renin-angiotensin-aldosterone system:
What happens when blood pressure is low?
When blood pressure is low, cells in the kidneys (juxtaglomerular apparatus) secrete the enzyme renin
Renin-angiotensin-aldosterone system:
After the secretion of the enzyme renin what two things happen?
- Angiotensinogen is converted to angiotensin I
2. Angiotensin I is converted to angiotensin II by ACE enzyme.
Angiotensin II has many effects that result in what?
a raise in blood pressure
What are the 3 effects angiotensin II has that result in a raise in blood pressure?
- Vasoconstriction of small arteries and arterioles
- Stimulates thirst center in hypothalamus
- Stimulates production of aldosterone in adrenal cortex
What is atrial natriuretic peptide produced by? when is it produced?
- Atria of the heart
2. When stretch is detected
What does atrial natriuretic peptide promote? What does it inhibit?
- Promotes salt and water excretion in urine in response to increased blood volume
- Inhibits ADH secretion
Is cardiac output distributed equally or unequally to organs? Why?
Cardiac output is distributed unequally to different organs due to unequal resistance to blood flow through the organs
Physical laws regulating blood flow:
- How does blood flow?
- What is the rate of blood flow proportional to?
- What is the rate of blood flow inversely proportional to?
- Blood flows from a region of higher pressure to a region of lower pressure.
- The rate of blood flow is proportional to the differences in pressure
- The rate of blood flow is also inversely proportional to the frictional resistance to blood flow within the vessels
The rate of blood flow is inversely proportional to the frictional resistance to blood flow within the vessels. What is an equation for this?
blood flow = ΔP/resistance
In the equation: blood flow = ΔP/resistance,
How is resistance measured?
resistance = Lη/ r4
In the equation: blood flow = ΔP/resistance, what is ΔP?
ΔP= pressure difference between the two ends of the tube
In the resistant equation: resistance = Lη/ r4:
- What is L?
- What is η?
- What is r?
- Length of the vessel
- Viscosity of the blood
- Radius of the blood vessel
Regarding the physical laws regulating blood flow: what does poiseuille’s law add?
Poiseuille’s Law adds in physical constraints
What is Poiseuille’s Law?
blood flow = ΔPr4(π)/ ηL(8)
How does Vessel length (L) and blood viscosity (η) vary?
Not normally
What are the most important factors in blood flow? Why?
- Mean arterial pressure and vessel radius (r)
2. Because Vessel length (L) and blood viscosity (η) do not vary normally
What provides the greatest resistance to blood flow and can redirect flow to/from particular organs?
Vasoconstriction of arterioles
What is Total Peripheral Resistance?
The sum of all vascular resistance in systemic circulation
Total Peripheral Resistance:
- Blood flow to organs runs parallel to each other, so a change in resistance within one organ _________.
- Vasodilation in a large organ may _____ total peripheral resistance and mean arterial pressure.
- ________ and _______ elsewhere make up for this.
- Blood flow to organs runs parallel to each other, so a change in resistance within one organ does not affect another.
- Vasodilation in a large organ may decrease total peripheral resistance and mean arterial pressure.
- Increased cardiac output and vasoconstriction elsewhere make up for this.