Chapter 14
Body Water Distribution
2/3 intracellular; the rest = 80% exists in interstitial spaces and 20% is in the blood plasma
Sounds of Korotkoff
A blood pressure cuff produces turbulent flow of blood in the brachial artery, which can be heard using a stethoscope
myoglobin
A globular protein found in muscle tissue that has the ability to bind oxygen. Helps to store oxygen in the muscle for use in aerobic respiration (it does not move, just stays there)
Physical Law of Blood Flow
Blood flows from a region of higher pressure to a region of lower pressure.
Alpha-adrenergic sympathetic stimulation
Causes Arterioles to have high vascular resistance at rest
Venous pooling
Causes Cardiac output to drop when one goes from lying to a standing position Not enough muscle contraction to get blood back to heart.
Starling Forces
Combination of hydrostatic pressure and oncotic pressure that predicts movement of fluid across capillary membranes (pc + πi) - (pi + πp) fluid out fluid in
Thermoregulation
Control of body temperature by the skin 1. Increased blood flow to capillaries in the skin releases heat when body temperature increases. 2. Sweat is also produced to aid in heat loss. 3. Bradykinins in the sweat glands also stimulate vasodilation in the skin.
Metabolic Control Mechanism
Local vasodilation is controlled by changes in: 1.Decreased oxygen concentrations due to increased metabolism 2.Increased carbon dioxide concentrations 3.Decreased tissue pH (due to CO2, lactic oxide, etc.) 4.Release of K+ and paracrine signals 5.Reactive hyperemia - constriction causes build-up of metabolic wastes which will then cause vasodilation (reddish skin) 6.Active hyperemia - increased blood flow during increased metabolism (reddish skin)
Paracrine Regulation of Blood Flow
Molecules produced by one tissue control another tissue within the same organ. (inclds. Bradykinin, NO2, Endothelian 1)
Regulation of Coronary Blood Flow
Norepinephrine from sympathetic nerve fibers (alpha-adrenergic) stimulates vasoconstriction, raising vascular resistance at rest Adrenal epinephrine (beta-adrenergic) stimulates vasodilation and thus decreases vascular resistance during exercise
Antidiuretic Hormone
Produced by the hypothalamus and released from the posterior pituitary when osmoreceptors detect increased plasma osmolality (thirst occurs) stimulates water reabsorption
Left-sided congestive heart failure
Pulmonary edema, shortness of breath, and fatigue
Poiseuille's Law
Resistance is proportional to viscosity/Radius^4
Atrial Stretch Reflexes
Responds to increased venus return of the heart. Stimulates reflex tachycardia Inhibits ADH release (more urine) Stimulates secretion of atrial natriuretic peptide (more salts and water in urine)
Metabolic Regulation
The most active regions of the brain must receive increased blood flow due to arteriole sensitivity to metabolic changes
Total Peripheral Resistance (TPR)
The sum of all vascular resistance in systemic circulation; Blood flow to organs runs parallel to each other, so a change in resistance within one organ shunts blood to other organs
Cerebral Circulation
Unless mean arterial pressure becomes very high, there is little sympathetic control of blood flow to the brain; held constant at 750 mL/min
Intrinsic Regulation of Blood Flow
Used by some organs (brain and kidneys) to promote constant blood flow when there is fluctuation of blood pressure; also called autoregulation control of blood flow by metabolic products of the tissues
Myogenic control mechanisms
Vascular smooth muscle responds to changes in arterial blood pressure; how arteries and arterioles react to an increase or decrease of blood pressure to keep the blood flow within the blood vessel constant.
Osmotic Forces
control the movement of water between the interstitial spaces and the capillaries, affecting blood volume
Cutaneous flow
controlled by extrinsic mechanisms and shows the most variation; can handle low rates of blood flow
Cerebral flow
controlled by intrinsic mechanisms and is relatively constant; the brain can not tolerate much variation in blood flow
Cardiac Control Center
controls heart rate, located in medulla oblongata
Vasomotor center
controls vasodilation and constriction
Bradykinins
a protein produced that acts to stimulate vasodilation and pain receptor activation in the sweat glands smooth muscle relaxor
Negative Chronotropic Effect
decrease cardiac rate
Negative chronotropic effect
decreases heart rate
Anaphylactic shock
due to a severe allergy in which histamine is released causing systemic vasodilation
Cardiogenic shock
due to cardiac failure
Arterial Blood Pressure
frictional resistance in the arteries, called afterload, proportional to cardiac output and total peripheral resistance
Arteriovenous anastomoses
functions as shunts allowing blood to be diverted directly from the arteriole to the venule and thus bypass superficial capillary loops and function in thermoregulation found mainly in dermis of skin
Cardiac Tissue
has lots of mitochondria and respiratory enzymes, thus is metabolically very active, has myoglobin to store oxygen during diastole to be released in systole
Treatments for Hypertension
limit salt intake; limit smoking and drinking; lose weight; exercise K+ (and possibly calcium) supplements Diuretics to increase urine formation
"Taking the Pulse"
measure of heart rate
Sphygmomanometer
measures blood pressure
Parasympathetic acetylcholine
opens K+ channels, slowing heart rate
Forces affecting Blood Volume
osmotic forces, urine formation, and water intake (drinking)
first Korotkoff sound
pressure is released, heard at systole and a reading can be taken
Vasoconstriction of Arterioles
provides the greatest resistance to blood flow and can redirect flow to/from particular organs
Sympathetic Stimulation in Cutaneous Blood Flow
reduces blood flow May result in lowered total peripheral resistance if not for increased cardiac output However, if a person exercises in very hot weather, he or she may experience extreme drops in blood pressure after reduced cardiac output. This condition can be very dangerous
Afterload
resistance against which ventricles pump, such as pressure in aorta
juxtaglomerular apparatus
secretes renin
Arteriovenous Anastomoses
shunt blood from arterioles directly to venules
Sympathoadrenal System
stimulates vasoconstriction of arterioles (raising total peripheral resistance) and increased cardiac output
Contractility
strength of ventricular contraction; contraction strength at any given fiber length
Baroreceptors
stretch receptors
Ejection Fraction
stroke volume/left ventricular end-diastolic volume; 80/120 = 0.66 about 60% of the EDV is ejected ratio of blood ejected from the ventricles to end-diastolic volume
Net filtration pressure
the hydrostatic pressure of the blood in the capillaries minus the hydrostatic pressure of the fluid outside the capillaries
Cardiac Output
the volume of blood pumped each minute by each ventricle
Dynamic equilibrium
the way fluid is circulating
Reactive Hyperemia
tissue vasodilation that occurs in response to accumulated products of tissue metabolism
Cutaneous Blood Flow
vascular resistance in the skin is high and blood flow is low
average ambient temperatures
vascular resistance in the skin is high, and blood flow is low
End diastolic volume
volume of blood in the ventricles at the end of diastole, sometimes called preload
last Korotkoff sound
when the pressure in the cuff reaches diastolic pressure and a second reading can be taken
Hypovolemic Shock
circulatory shock from low blood volume, as in hemorrhage
Sympathetic norepinephrine
keep HCN channels open, increasing heart rate.
Colloid osmotic pressure
keeps fluid in the intravascular compartment by pulling H2O from the interstitial space bank into the capillaries (vascular compartment); Due to proteins dissolved in fluid
Aldosterone
"salt-retaining hormone" which promotes the retention of Na+ by the kidneys. Regulated by renin-angiotensin-aldosterone Does not change blood osmolality Mineralocorticoid
Vasodilation
A widening of the diameter of a blood vessel.
Extrinsic Regulation of Blood Flow: Parasympathetic Nerves
Acetylcholine stimulates vasodilation. Limited to digestive tract, external genitalia, and salivary glands Less important in controlling total peripheral resistance due to limited influence
Baroreceptor Reflex
Activated by changes in blood pressure detected by baroreceptors (stretch receptors) in the aortic arch and carotid sinuses Increased blood pressure stretches these receptors, increasing action potentials to the vasomotor and cardiac control centers in the medulla. Most sensitive to drops in blood pressure
Blood Pressure
Affected by blood volume/stroke volume, total peripheral resistance, and cardiac rate
Inotropic
Agent that affects the force of cardiac muscular contractions
Renin
An enzyme secreted by the juxtaglomerular cells when blood pressure decreases. Converts angiotensinogen to angiotensin I.
Hyperemia
An excess of blood in a part of the body
ACE enzyme
Angiotensin I is converted to angiotensin II in capillaries of the lungs; increases blood pressure by causing blood vessels to constrict
Regulation of Stroke Volume
End diastolic volume, arterial blood pressure, contractility
Edema
Excessive accumulations of interstitial fluids
What Causes an Edema
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
Essential Hypertension
Hypertension caused by an unknown reason
Extrinsic Regulation of Blood Flow: Sympathetic Nerves
Increase in cardiac output and increase total peripheral resistance through release of norepinephrine onto smooth muscles of arterioles in the viscera and skin to stimulate vasoconstriction (alpha-adrenergic). Adrenal epinephrine stimulates beta-adrenergic receptors for vasodilation During "flight or fight", blood is diverted to skeletal muscles
Frank-Starling Law of the Heart
Increased EDV results in increased contractility and thus increased stroke volume
Role of Sympathetic Nervous System in Blood Volume
Increased blood volume in the atria stimulates stretch receptors that leads to increased sympathetic stimulation to the heart and decreased stimulation to the kidneys
How does blood volume increase?
Increased water intake and decreased urine formation
Glomeruli
Special filtering capillaries in the kidneys
Regulation of Cardiac Rate
Spontaneous depolarization occurs at SA node when HCN channels open, allowing Na+ in
Extrinsic Control of Contractility
Sympathetic norepinephrine and adrenal epinephrine (positive inotropic effect) can increase contractility by making more Ca2+ available to sarcomeres. Also increases heart rate. Parasympathetic acetylcholine (negative chronotropic effect) will decrease heart rate which will increase EDV increases contraction strength increases stroke volume, but not enough to compensate for slower rate, so cardiac output decreases
When is Blood Flow Restricted in the Heart?
Systole
Venous Return
The amount of blood returned to the heart by the veins
Mean Arterial Pressure
The average pressure in the arteries in one cardiac cycle
Angiotensin II
Very powerful vasoconstrictor; A hormone that stimulates constriction of precapillary arterioles and increases reabsorption of salt and water by the proximal tubules of the kidney, increasing blood pressure and volume.
Myogenic Regulation
When blood pressure falls, cerebral vessels automatically dilate. When blood pressure rises, cerebral vessels automatically constrict
Renin-angiotensin-aldosterone system
When blood pressure is low, cells in the kidneys (juxtaglomerular apparatus) secrete the enzyme renin
Intrinsic Control of Contraction Strength
ability of local tissue to vasodilate or constrict arterioles that serve them
Extracellular
blood plasma
Compliance
blood vessels being greater in veins than in arteries the ability of a vessel to distend and increase volume with increasing transmural pressure
Preload
can also be considered end-diastolic volume; volume of blood in the ventricles at the end of diastole
Septic Shock
caused by an endotoxin produced by bacteria that decreases blood pressure and affects of ability of the heart to pump
Histamine
causes vasodilation; like a bug bite, can also cause dangerous drop in blood pressure if allergic
Hypertension
high blood pressure, causes increased afterload; greater than 140mm/Hg in systole
Pressure Difference in Venous System
highest pressure in venules vs. lowest pressure in venae cavae into right atrium
Positive Chronotropic Effect
increase cardiac rate
reflex tachycardia
increased heart rate in response to some stimulus conveyed through the cardiac nerves
Atrial Natriuretic Peptide
increases excretion of salt and water from kidneys to reduce blood volume Inhibits ADH secretion Antagonist of aldosterone secreted by the heart
Positive chronotropic effect
increases heart rate
How to raise blood pressure
increasing blood volume/stroke volume, total peripheral resistance, and cardiac rate vasoconstriction of arterioles
Intracellular
inside cells; 2/3 of body's water
Oncotic pressure
inward pulling force caused by blood proteins that helps move fluid from interstitial area back into capillaries