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