Download Lecture 14

Chapter 14
Cardiac Output, Blood Flow, and
Blood Pressure
Cardiac Output (CO)

Volume of blood pumped/min. by each ventricle.
 Pumping
ability of the heart is a function of the beats/
min. and the volume of blood ejected per beat.


Total blood volume averages about ________.
Each ventricle pumps the equivalent of the total
blood volume each min. (resting conditions).
Regulation of Cardiac Rate


Without neuronal influences, the heart beats according
to the rhythm set by ___________________.
Autonomic control:



Sympathetic and parasympathetic nerve fibers to the heart
modify the rate of spontaneous depolarization.
Innervate the SA node.
 NE and Epi stimulate opening of __________ channel.
 _________ promotes opening of K+ channel.
 Major means by which cardiac rate is regulated.
Cardiac control center (medulla):

Coordinates activity of ___________ innervation.
TPR

Total Peripheral Resistance:
 Impedance
ventricle.
to the ejection of blood from
Venous Return



Return of blood to the heart via _______
Venous pressure is driving force for return of
blood to the heart.
Veins have thinner walls, thus higher
compliance.
 Capacitance
vessels.
 2/3 blood volume is in _________.
Exchange of Fluid between
Capillaries and Tissues



Distribution of ECF between plasma and interstitial
compartments is in state of dynamic equilibrium.
 Balance between tissue fluid and blood plasma.
__________________pressure:
 Exerted against the inner capillary wall.
 Promotes formation of tissue fluid.
 Net filtration pressure.
________________osmotic pressure:
 Exerted by plasma proteins.
 Promotes __________ reabsorption into circulatory
system.
Fluid Movement
(continued)
Causes of Edema


Excessive accumulation of tissue fluid.
Edema may result from:
 _____________arterial
blood pressure.
 Venous _____________
 Leakage of plasma __________ into interstitial fluid.
 Myexedema.
 Decreased plasma [protein].
 Obstruction of ___________ drainage.
Regulation of Blood Volume by the
Kidney
Formation of urine begins by filtration of
plasma through capillary pores.
 Volume of urine excreted can be varied
by changes in reabsorption of filtrate.

 Adjusted
according to needs of body by
action of hormones.
Regulation by ADH


Released by ______
pituitary when
osmoreceptors
detect an increase in
plasma osmolality.
Dehydration or
excess salt intake:

Produces sensation
of _________.
 Stimulates water
reabsorption from
filtrate.
Regulation by Aldosterone


___________ hormone secreted by adrenal
cortex.
Mechanism to maintain blood volume and
pressure through absorption and retention of
__________ and Cl-.
 Stimulates
reabsorption of NaCl.
 Indirectly increases H20 reabsorption.
 Does not dilute osmolality.

Release stimulated:
 During
salt deprivation.
 Reduced blood _________ and pressure.
Renin-Angiotension-Aldosterone System




When blood pressure and flow are reduced in
renal artery, juxtaglomerular apparatus
secretes renin.
Renin converts angiotensinogen to
angiotensin I.
Angiotensin I is converted to angiotensin II
Angiotensin II:
 Raises
blood ________________
 Powerful vasoconstrictor.
 Stimulates production of aldosterone (more salt
and water retention in kid).
 Stimulates ____________________
Renin-Angiotension-Aldosterone System
Atrial Natriuretic Peptide (ANP)
Produced by the _______of the heart.
 Stretch of atria stimulates production of
ANP.

 Antagonistic
to aldosterone and angiotensin
II.
 Promotes Na+ and H20 excretion in the urine
by the kidney.
 Promotes _________________.
Extrinsic Regulation of Blood Flow
(continued)

Parasympathetic nervous system:
 Parasympathetic

_________ limited.
Promotes vasodilation to the digestive tract,
external genitalia, and salivary glands.
 Less
important than sympathetic nervous
system in control of TPR.

Parasympathetic endings in arterioles promote
vasodilation.
Paracrine Regulation of Blood Flow

Endothelium produces several paracrine
regulators:

Nitric Oxide, Bradykinin, prostacyclin

Cause vaso-relaxation
Intrinsic Regulation of Blood Flow
(Autoregulation)
(continued)

Metabolic control mechanism:
 Intrinsic
receptors sense chemical changes
in environment.
 Vasodilation:

Decreased 02:


Increased C02:


Decreased ventilation.
Decreased pH:


Increased _________________.
________________.
Increased adenosine or increased K+:

From tissue cells.
Regulation of Coronary Blood Flow
Sympathetic nervous system:
 a receptors:

 ____________________

at rest.
b receptors:
 ______________________.
Regulation of Blood Flow Through
Skeletal Muscles
Decreased blood flow when muscles
contract and constrict arterioles.
 Sympathetic:


a-adrenergic receptors:


Vasoconstrict at rest.
Cholinergic and b-adrenergic
receptors:
 Vasodilate.
Cutaneous Blood Flow

Thermoregulation:
 Blood
flow through the skin is adjusted to
maintain deep-body temperatures at about 37o
C.
 Occurs due to:


Vasoconstriction/vasodilation arteries.
Bradykinin:
 Sweat
glands secrete bradykinin which
increases blood flow to skin and sweat glands.

Changes in ___________ blood flow,
occur as a result to changes in
sympathetic nerve activity; which is
controlled by the brain.
Blood Pressure (BP)

Pressure of arterial blood is regulated by blood volume,
TPR, and cardiac rate.


Arteriole resistance is greatest because they have the
smallest diameter.


Capillary BP is reduced because of the total cross-sectional area.
3 most important variables are HR, stroke volume, and
TPR.


________________________.
Increase in each of these will result in an increase in _____.
BP can be regulated by:

Kidney and sympathoadrenal system.
Baroreceptor Reflex




Stretch receptors located in the aortic arch and
carotid sinuses.
An increase in pressure causes the walls of these
regions to stretch, increasing frequency of APs.
Baroreceptor reflex activated with changes in BP.
More sensitive to decrease in pressure and
sudden changes in pressure.
Atrial Stretch Reflexes
Located in the ________ of the heart.
 Receptors activated by increased venous
return.

Stimulate reflex tachycardia.
 Inhibit ____________ release.
 Promote secretion of _________________.
