heart and circulation

heart main function

to distribute oxygen and nutrients to the cells of the body, and to take away carbon dioxide and other wastes

arteries demonstrate a _____

pattern of divergence

veins demonstrate_____

convergence

chordae tendineae

cord-like structures connecting AV valves cusps to papillary muscles

pacemaker cells

essential for establishing heart rate

arteries and veins branch_____

into arterioles and venules

3 layers of blood vessels

• tunica intima

• tunica media

• tunica externa

tunica intima

****endothelium—-squamous epithelial tissues and in arteries with internal elastic membrane

INNER LAYER——next to lumen

artery characteristics

****elastic——allows them to absorb pressure created by ventricles of heart as they pump blood

• smooth muscle in tunica media so they can increase/decrease their diameter

*****tunica media is the thickest layer

tunica media

****smooth muscle and connective tissue

MIDDLE LAYER——smooth muscle and external elastic membrane

tunica externa

****connective tissue

OUTERMOST LAYER——next to surrounding tissue

***this is a veins THICKEST layer

capillaries connect____

arterioles and venules

arteriolesand venules branch_____

into capillaries

hydrostatic pressure

pressure exerted by fluid on a wall

capillary hydrostatic pressure (CHP)

pressure inside capillaries

circulatory pressure

pressure difference across systemic circuit

net hydrostatic pressure

internal pressure - external pressure

pressure gradient

pressure difference across a vessel

vascular resistance

resistance due to vessel length and diameter

pulse p

rhythmic pressure fluctuation each heartbeat

thoroughfare channel

continuation of metarteriole without smooth muscle, connecting to postcapillary venul

precapillary sphincters

smooth muscle rings that controls the flow of blood in the capillary beds

pulse pressure

difference between systolic and diastolic pressures

osmosis

diffusion of water across membrane

blood colloid osmotic pressure (BCOP)

osmotic pressure from plasma proteins

osmotic pressure

pressure needed to prevent osmosis

filtration

movement of fluid through a membrane by pressure

ligamentum arteriosum

fibrous remnant of a fetal vessel linking pulmonary and systemic circuits

capillary exchange

transfer between blood and interstitial fluid

frank-starling principle

increased EDV (end-diastolic volume) ——> increased stroke volume

pulmonary veins

vessels returning oxygen-rich blood from lungs to left atrium

number of heart beats per day

100,000

pulmonary circuit

carries oxygen-poor blood that becomes oxygen rich

***blood vessels between the pulmonary semilunar valve of the right ventricle——> blood flow through the lungs

(oxygen poor blood)—→ right ventricle——> pulmonary arteries—→ lungs——> (oxygen rich blood) —→ pulmonary veins——> left atrium

septa

muscular partitions separating heart chambers

systemic circuit

carries oxygen-rich blood that becomes oxygen poor

*****vessels between the aortic valve and the entrance to the right atrium

(oxygen rich blood)—→ left ventricle——> systemic arteries—→ (oxygen poor blood) —→ systemic veins——> right atrium

bulk flow

movement of fluid and dissolved solutes from capillaries to tissues and back——-results from the interplay of filtration and reabsorption

left side of the heart

supplies blood to the systemic circuit

right side of the heart

supplies blood to the pulmonary circuit

arteries

carry blood AWAY from the heart

dynamic center of a capillary

point where osmotic is equal hydrostatic pressure

aortic sinuses

space between the superior portion of each aortic valve cusp and the dilated portion of the ascending aorta

veins

RETURN blood to the heart

****act as blood reservoirs and can accommodate large changes in blood volume

great vessels

largest veins and arteries in the body—-connected to the heart

capillaries

microscopic thin-walled vessels that interconnect the smallest arteries and the smallest veins

***exchange vessels***

• because their thin walls permit the exchange of nutrients, dissolved gases, and wastes

suited for this function because they lack a smooth muscle layer

right atrium of heart

receives blood from the systemic circuit through the superior vena cava and inferior vena cava—→ passes it to the right ventricle

right ventricle

receives blood from the right atrium and pumps blood into the pulmonary circuit

left atrium

collects blood from the pulmonary circuit and empties it into the left ventricle

left ventricle

receives blood from the left atrium and pumps blood into the systemic circuit

contraction during a heart beat

atria is the first to contract and then the ventricles contract

endocardium

walls of the heart, from deep to superficial ——-inner layer with simple squamous epithelium continuous with the endothelial lining of blood vessels

myocardium

spiral bundles of cardiac muscle cells

pericardium

fibrous sac that surrounds the heart0protect, anchor, and prevent overfilling—-includes:

• fibrous pericardium

• serous pericardium

serous pericardium

• two layered

made up of a parietal layer and a visceral layer (epicardium)

*****pericardial cavity is inbetween layers

pericardial cavity

fluid-filled space between the two serous lays

fibrous pericardium

contains a dense network of collagen fibers that stabilize the position of the heart and associated with vessels within the mediastinum

fibrous pericardium

contains a dense network of collagen fibers that stabilize the position of the heart and associated vessels within the mediastinum

auricle

expandable extension of an atrium

pericardial fluid

inside pericardial cavity—— secreted by the pericardial membranes

***acts as a lubricant, reducing friction between the opposing visceral and parietal surfaces as the heart beats

cardiac tamponade

a compression of the heart due to fluid accumulation in the pericardial cavity

coronary sulcus

a deep groove, marks the border between the atria and the ventricles

aorta

***large, elastic artery

major blood vessel that carries oxygenated blood away from the left ventricle and into the systemic circuit

calcium ions

serve a crucial role in cardiac contraction

Sinoatrial node (SA)

initiates the heartbeat—-a part of the conducting system

****pacemaker of the heart

atrial systole

The phase of the cardiac cycle when the atria contract to push blood into the ventricles

ventricular diastole

phase of the cardiac cycle when the ventricles relax and fill with blood

cardiac output

The amount of blood the heart pumps through the circulatory system in a minute

***influences by heart rate and stroke volume

2000 gallons

the amount of blood the heart pumps daily

cardiac skeleton (fibrous)

consists of four dense bands of tough elastic tissue that encircle the heart valves and the bases of the pulmonary trunk and aorta

****anchors the heart valves and supports the great vessels

atrioventricular valves

one of the valves that prevents backflow into the atria during ventricular systole (contraction)

atrial diastole

continues until the start of the next cardiac cycle—-phase when the atria are relaxed and begins right after atrial systole

atrioventricular node

located in the floor of right atrium near the opening of coronary sinus

*****connected to SA node by conducting fibers in atrial wall

nodal tissue

produces action potentials that spread through the heart for contraction

autorhythmic

the heart can contract on its own without stimulation from nerves

nodal cells

heart cells responsible for setting the rate of cardiac contraction (heart rhythym)

****membranes depolarize automatically and produce action potentials

intercalated discs

connect cardiac muscle fibers mechanically and electrically

***when fiber contracts, the electrical stimulus passes through disc and excites the adjoinnig cardiac fiber

internodal pathways

link SA and AV node for conduction of the stimulus

conducting fibers

distribute stimulus from AV node to myocardium of the ventricles

Atrioventricular bundle (bundle of HIS)

located in interventricular septum——divides into bundle branches that spread across inferior of each ventricle

***carries electrical stimulus from AV node down into ventricles

purkinje fibers

the tiny divisions that carry Action Potentials to cells of ventricles

conduction system events

1. SA node generates action potential

2. impulse spreads throughout the atria causing them to both to contract while internodal pathway carries impulse to AV node

3. AV node receives impulse from SA node

4. AV node generates an action potential that travels down the AV bundle and bundle branches to Purkinje fibers

5. ventricles contract in a wave from the inferior apex upward to the base to force blood out of the heart

6. bundle branches deliver action potential to the papillary msucles causing these muscles to contract just prior to the ventricles

P wave

****on an ECG—→ corresponds to atrial depolarization——> first small, smooth upward deflection seen before the QRS complex in a normal ECG tracing

QRS complex

part of ECG tracing that represents ventricular depolarization

****begins at the Q waves (a small downward deflection)———> peaks at the R wave——> ends at the S wave

T wave

****ECG

ventricular repolarization——follows QRS

Electrocardiogram (ECG/EKG)

recording of electrical changes that occur during cardiac cycle

***useful in diagnosing cardiac arrhythmias

arrhythmias

abnormal heart patterns

sinus rhythms

normal heart rate

action potential

responsible for heart contraction

muscles and nerve membranes at rest

membranes must have a negative electrical charge on the inside

depolarization

when a muscle or nerve is stimulated——> becomes less negative

****causes contraction

repolarization

when slow voltage-regulated calcium channels begin to close, slow voltage-regulated potassium channels open——→ returns to resting potential——> RELAXATION

action potential in cardiac muscle

1. rapid depolarization

2. the plateau

3. repolarization

rapid depolarization

purkinje fibers electrically stimulate voltage-regulated sodium channels to open and extracellular sodium flows into contractile cell

fast channels

voltage sodium channels

the plateau

at +30 mV, the fast sodium channels close and slow voltage-regulated calcium channel opens———> extracellular calcium enters heart cell and maintains the transmembrane potential above 0mV——> prolongs the action potentials int he heart cell———> extracellular calcium triggers intracellular calcium release from the sacroplasmic reticulum——→the voltage regulated sodium channels stay closed until -60mV

Coronary artery disease (CAD)

it is a form of heart disease in which plaques build up in the walls of the coronary arteries, the vessels that supply blood to the heart muscle———>buildup narrows the arterial lumen and reduces blood flow to cardiac muscle

coronary ischemia

a reduction in blood flow to the heart muscle——> inadequate perfusion (oxygen and nutrient supply) of cardiac tissue

angina pectoris

chest pain caused by inadequate blood supply to the heart msucle

ischemia

inadqeuate blood supply

angiography

an imagining technique used to visualize blood vessels and blood flow, especially in organs like heart brain, lungs, and kidneys

MI (myocardial infarction)

heart attack——caused by a sudden reduction of blood flow—→ not enough oxygen to the heart