191 a Exam #3

functions of the CV system

functions of the CV system

transportation, regulation (pH, temperature, water), protection (platelets, WBCs, blood proteins)

scientific names for RBC and WBC

RBC = erythrocytes, WBC = leukocytes

Platelets

cell fragments (with no nucleus) that initiate clots and close blood vessel breaks

what makes up the majority of blood

plasma (mostly water)

heart COVERINGS from outer to inner

1. fibrous pericardium

2. serous pericardium (2a. parietal pericardium, 2b. visceral pericardium / epicardium)

fibrous pericardium

tough, fibrous connective tissue that is the protective outer sac of the pericardium

serous pericardium

double-walled inner sac of pericardium composed of the parietal and visceral pericardium

parietal pericardium

outer layer of the serous pericardium

visceral pericardium (epicardium)

inner layer of serous pericardium sac / outer layer of heart wall; rests ON ORGAN

pericardial/serous cavity

space between parietal and visceral layers of the serous pericardium containing pericardial/serous fluid; decreases friction as heart moves

myocardium

thick middle layer of heart wall composed of cardiac muscle; has many blood and lymph capillaries and nerve fibers

Cardiac muscle

= rhythmic, involuntary, striated fibers connected in branching 3D networks; contract in ALL-OR-NONE manner

Endocardium

smooth inner layer of the heart wall composed of endothelium and elastic connective tissue

pulmonary circuit

carries blood from the heart to lungs to heart again

(starts in RV)

systemic circuit

carries blood from the heart to whole body to heart

(starts in LV)

amount of oxygen and CO2 in blood are always ___ of each other?

opposite

atria

thin-walled upper heart chambers that RECEIVE RETURNING blood

ventricles

thick-walled lower heart chambers that receive blood from the atria and contract to FORCE BLOOD OUT of the heart into the arteries

(left ventricle is largest with thickest walls)

septum

solid, wall-like structure that divides the heart into left and right halves, preventing blood from mixing

interatrial septum

thinner, upper portion of the septum that separates atria

interventricular septum

lower, thicker portion of the septum that separates ventricles

atrioventricular valves

valves composed of leaf-like cusps that prevent backflow into the ATRIA; includes the tricuspid and bicuspid (mitral) valve

semilunar valves

valves composed of deep U-shaped cusps that prevent backflow into the VENTRICLES; includes the pulmonary and aortic valves

can AV valves be open while semilunar valves are open?

no

path of blood flow through the heart (starting with right side)

1. coronary sinus and vena cavae

2. RA

3. tricuspid valve

4. RV

5. pulmonary valve

6. pulmonary trunk

7. pulmonary arteries

8. arterioles

9. capillaries

10. venules

11. pulmonary veins

12. LA

13. bicuspid (mitral) valve

14. LV

15. aortic valve

16. aorta (ascending, arch, descending)

coronary sinus

smaller vein which returns blood from the heart wall into the RA

Chordae tendineae

strong, fibrous strings that attach to the cusps of AV valves on the ventricular side

Papillary muscles

muscles that pull on chordae tendineae to prevent AV valve cusps from swinging back into atria

are AV valves open or closed during ventricular contraction?

closed

why do heart valves open and close?

Valves close due to PRESSURE DIFFERENCES created by ventricular contractions and relaxations

what happens right before the AV valves close?

atrial contraction increases atrial pressure to empty remaining blood into ventricles

mitral valve prolapse (MVP)

one or both cusps of the mitral valve stretch and bulge into the LA during ventricular contraction, causing regurgitation of blood into the LA and heart murmur

rules regarding pressure

the fuller the chamber (more contents), the higher the pressure

the bigger the chamber (more space), the lower the pressure

coronary arteries

arteries branching from the aorta that supply oxygenated blood to the walls of the heart

Cardiac (coronary) veins

veins parallel to coronary arteries that drain blood that has passed through myocardial capillaries; join the coronary sinus to return blood to RA

Coronary artery disease (CAD) / heart disease

partial or complete blockage of coronary circulation, usually due to coronary atherosclerosis and reduction of blood flow to the myocardium

symptoms: angina pectoris, MI, stroke

risk factors: cholesterol, smoking, hypertension, family history, post-menopausal women, men >45

#1 cause of death in the US

Electrocardiogram (ECG)

records electrical changes (depolarization and repolarization) in the myocardium during the cardiac cycle

P wave

• when does contraction occur?

depolarization of the atria (to push out the last bit of blood)

Contraction occurs during following flatline

QRS complex

• when does contraction occur?

depolarization of the ventricles (only really shows left because the myocardium is so thick)

Contraction occurs AFTER the peak of the R wave

T wave

Repolarization of the ventricles

(before relaxation)

Bradycardia

slow HR < 60 bpm

Tachycardia

fast HR > 100 bpm

Systole

contraction of a heart chamber; increases pressure

Diastole

relaxation of a heart chamber; decreases pressure

Cardiac cycle

one complete heartbeat; the coordinated contraction of the heart chambers

(Atrial/ventricular) Syncytium

mass of merging muscle fibers that act as a unit

*Note: atrial and ventricular syncytium are mostly separated to prevent simultaneous atrial and ventricular contraction

heart murmur

abnormal heart sound; may be the sound of blood moving back into the LA due to MVP

"lubb"

blood hits closed AV valves during ventricular CONTRACTION

"dupp"

blood hits closed pulmonary and aortic valves (snap shut) during ventricular RELAXATION

automaticity / autorhythmicity

cardiac muscle contracts without neural or hormonal stimulation

cardiac conduction system definition

system of specialized cardiac muscle that initiates and distributes nerve impulses for contraction; contains few myofibrils because its function isn't contraction

cardiac conduction system order

1. SA node

2. junctional fibers (internodal fibers)

3. AV node

4. AV bundle/Bundle of His

5. L/R bundle branches

6. Purkinje fibers

SA node

self-stimulating specialized cardiac muscle tissue that generates the heart's rhythmic contraction; depolarizes fastest

located near opening of superior vena cava beneath the epicardium and continuous with the atrial syncytium

Junctional (internodal) fibers

cardiac muscle fibers with small diameters that slow and conduct impulses from the SA node to the atrial syncytium, resulting in atrial contraction, AND conduct impulses from the atrial syncytium to the AV node

SA -> atrial syncytium -> AV

AV node

specialized cardiac muscle tissue that slows the spread of impulse to ventricles; depolarizes slower

*Functions as a secondary (but slower) pacemaker if SA node fails

located in inferior portion of interatrial septum just beneath the epicardium

AV bundle / Bundle of His

group of large fibers forming the only electrical connection between the atria and ventricles

L/R bundle branches

division of AV bundle fibers (beginning at the upper part of the interventricular septum) that deliver impulses to Purkinje fibers or directly to papillary muscles

lies between the endocardium

*left branch is larger because it supplies the larger left ventricle

Purkinje fibers

division of bundle branches that spread from the interventricular septum into papillary muscles and from the apex to the base of the heart

their branches are continuous with cardiac muscle fibers

Why does the heart contract in a twisting motion?

Ventricular fibers are arranged in irregular whirls

intercalated discs

points of connection between cardiac muscle fibers that allow impulses to travel from cell to cell

gap junctions

relay stations at intercalated discs that transmit depolarization to the next cardiac muscle fiber

Autonomic nervous system (ANS)

part of the peripheral nervous system with nerves that innervate the viscera; associated with involuntary activities; maintains homeostasis

Sympathetic nervous system

o readies the body to expend energy ("fight or flight"); secretes NE and E, which increase HR and cardiac muscle cell metabolism, strengthening contraction and increasing stroke volume

PARAsympathetic nervous system

(like the "brakes") most active at REST; secretes Ach, which decreases HR by hyper-polarization and inhibition of cells, weakening contraction and decreasing stroke volume

cardiac output

amount of blood pumped by each ventricle per minute (mL/min), indicating blood flow to peripheral tissues; CO = HR x SV

stroke volume

the amount of blood pushed out of the ventricles per contraction (mL/beat); SV = EDV - ESV

*most important factor to cardiac output

End diastolic volume (EDV)

how full the ventricles are at the end of diastole

End systolic volume (ESV)

how much blood remains in the ventricles at the end of systole

3 purposes of CV regulation

ensure that changes in blood flow occur (1) at right time, (2) in right area, (3) without drastically changing BP or flow to vital organs

regulation of cardiac output

Extrinsic regulation: (HR, indirectly affects SV)

• ANS: cardiac center sends sympathetic or parasympathetic impulses

• hormones: mimic sympathetic impulses

Intrinsic regulation: (SV)

• Starling's law & EDV/ESV

What 3 things control stroke volume?

preload, contractility, afterload

preload

stretch prior to contraction; depends on fill time and venous return

contractility

strength of myocardial contraction

afterload

BP in the pulmonary trunk and aorta that must be EXCEEDED before blood can be ejected from ventricles

*more afterload = less SV because less blood leaves the heart

Blood vessel pathway from ventricles to atria

1. ventricles

2. arteries

3. arterioles

4. capillaries

5. venules

6. veins

7. atria

artieries

strong, elastic vessels that carry blood away from the ventricles under high pressure

arterioles

thinner, muscular branches of arteries with elastic-recoil capability; regulate blood flow from arteries into capillaries

Capillaries

thinnest blood vessels that connect the smallest arterioles and venules; where exchange occurs

Venules

non-elastic, microscopic vessels that continue from capillaries; initially lack muscular tunica media in smallest venules

Veins

non-elastic, larger vessels that collect blood and return it to the heart

walls of arteries and veins (small to big)

1. tunica interna/intima

2. tunica media

3. tunica externa/adventitia

tunica interna/intima

inner wall of blood vessels composed of smooth endothelium that prevents clots; has elastic basement membrane of collagen and outer internal elastic lamina layer with small pores to allow for diffusion between walls

Tunica media

middle wall of blood vessels composed of smooth muscle and a thick layer of elastic connective tissue; regulates diameter of the lumen

Tunica externa/adventitia

outer wall of blood vessels composed of a thin layer of irregularly organized elastic and collagen fibers; protects blood vessel and attaches it to surrounding tissue

Elastic arteries

largest arteries (e.g. aorta) that are most elastic to transport a lot of blood; their tunica media is lined with elastic lamellae

Muscular arteries

medium-sized arteries that are less elastic but more muscular to distribute blood; maintain pressure by maintaining vascular tone and do not have recoil capability

Continuous capillaries

endothelial cells form a continuous tube with intercellular gaps through which exchange occurs

Fenestrated capillaries

endothelial cells have many fenestrations (pores) through which exchange occurs

Sinusoids

larger capillaries with very large fenestrations and intercellular gaps through which exchange occurs

Autonomic regulation of blood vessel diameter

*ONLY SYMPATHETIC INNERVATION

vasomotor center controls vasoconstriction and dilation

Vasomotor fibers

sympathetic innervation of smooth muscle in arteries, arterioles, veins, and venules

• increased sympathetic stimulation (more NE/E) -> constriction

• decreased sympathetic stimulation (less NE/E) -> dilation

precapillary sphincters

smooth muscles encircling capillary entrances that regulate blood distribution, routing oxygenated blood to different parts of the body

diffusion

substances move across a semi-permeable membrane down the concentration gradient

filtration

greater hydrostatic pressure on one side of the membrane forces molecules through to the other side, often separating solids from liquids

osmosis

blood pressure is greater within the vessel than outside it, forcing water across a selectively-permeable membrane while larger molecules remain inside

veins vs. arteries

• Arteries: smaller lumen, thickest walls because contents are under highest pressure, so the vessels are more muscular and elastic

• Veins: larger lumen, thinner walls because contents are under lower pressure, so the vessels are less muscular and elastic. Contain semilunar valves

How is blood flow maintained in veins?

• valves support one-way flow and distribute weight of blood

-venoconstriction, skeletal contraction, and respiratory movements increase pressure

blood pressure

the force blood exerts against the inner walls of blood vessels (usually arteries)

why does BP decrease further away from the heart?

distance from pump + peripheral resistance

systolic pressure

maximum pressure in the arteries as a result of ventricular systole