A&PII MODULE 3

myocardium

heart muscle

heart & generating blood pressure

heart/myocardium squeezes → blood pushed into arteries (from the chambers) → pressure builds up and pushes against the artery walls = blood pressure

heart & routing blood

right ventricle = pushes blood into the pulmonary arteries (to lungs)

left ventricle = pushes blood into the aorta (to the whole body)

right = respiratory 

left = life

heart & ensuring one-way blood flow

valves prevent backflow during contractions

heart & regulating blood supply

heart adjusts cardiac output based on nerves/hormones

cardiac output

total volume of blood pumped by a ventricle per minute

all the squeezes in a minute

pericardium location

encloses the heart within the mediastinum

fibrous pericardium

tough outer layer that anchors the heart

fibrous = firm & fixed 

serous pericardium

inner layer, delicate and produces lubrication fluid (fluid for friction-free beating)

serous = slippery & smooth 

structure of serous pericardium

two layers:

parietal - lines fibrous pericardium

visceral - covers heart surface 

pericardial cavity between layers contains pericardial fluid 

location of the heart

in the mediastinum of the thoracic cavity

base of the heart

superior, flat, deep to sternum

where the great vessels attach

apex of the heart

inferior, pointy tip near diaphragm

what are the top chambers

atria

atria = Always on top (lightweight chambers)

what divides the top chambers

interatrial septum

what are the bottom chambers

ventricles

ventricles = Very strong bottom chambers 

what divides the bottom chambers

interventricular septum

what valve separates the top right from bottom right side

Tricuspid (right AV) valve

TRI before you BI (Tricuspid on right, Bicuspid/Mitral on left)

what valve separates the top left from bottom left side 

bicuspid/mitral (left AV) valve

TRI before you BI (Tricuspid on right, Bicuspid/Mitral on left)

what valve separates the right bottom chamber from the vessel leaving the heart

pulmonary valve / right semilunar valve (same thing)

RAP:  Right Atrium = Pulmonary

What valve separates the left bottom chamber from the vessel leaving the heart?

aortic valve / left semilunar valve

LAA: Left Atrium = Aorta

epicardium

epicardium = exterior

outermost / superficial layer covering the heart 

Myocardium

Myocardium = Muscle

thick, muscular layer

contracts to pump blood 

Myocardium & heart skeleton

Myocardium is anchored to the fibrous skeleton

→ structural support

→ electrical insulation between atria and ventricles 

endocardium

deepest layer of the heart

lines inner chambers 

simple squamous epithelium

pectinate muscles

atria muscle

internal ridges 

crista terminalis

atria muscle

ridge separating pectinate muscles from smooth atrial wall

trabeculae carneae

ventricle muscle 

internal ridges 

papillary muscles

ventricle muscles

anchors chordae tendineae to prevent AV valve backflow

cardiac muscle physical appearance

cardiac muscle tissue = striations and branching fibers

is cardiac muscle voluntary or involuntary

involuntary

controlled by autonomic nervous system and intrinsic properties 

auto-pilot 

what structures connect adjacent cardiac muscle cells

intercalated disks

→ thick end-to-end connections 

→ allow synchronized contraction

inside structures of intercalated disks

desmosomes: hold cells together so they don’t pull apart during contraction 

gap junctions: pass electrical signals and ions so cells contract together 

D = Durable anchor

G = Gateway for signals

What energy sources can cardiac muscle cells use to produce ATP?

Aerobic metabolism

use fatty acids, glucose, and lactate for ATP production

how does aerobic respiration benefit cardiac muscle function

ensures a continuous supply of energy for constant contraction

list in order the structures associated with the conduction system

Sally Always Buys Real Purple Mugs

SA node 

AV node 

Bundle of His 

Right & Left branches 

Purkinje fibers 

Myocardium

Explain how the action potential moves through the conduction system and stimulated surrounding muscle

Sally And Bob Bring Pizza

SA node → AV node → Bundle of His → Bundle branches → Purkinje fibers

Action potential starts in SA node and spreads through the atria to the AV node, down the AV bundle and bundle branches, then through Purkinje fibers, which stimulate ventricular muscle to contract

autorhythmic

can self-stimulate contraction without external signals

automatic rhythm 

where does a heartbeat originate

SA node = pacemaker of the heart 

SA node = spark plug of the heart 

Explain the channels and ions involved in the initiation of a heartbeat

Pacemaker potential: Na⁺ leaks into the SA node cells, depolarizing the membrane

Threshold reached: Voltage-gated Ca²⁺ channels open, causing rapid depolarization 

Repolarization: K⁺ channels open, letting K⁺ exit the cell, returning it to the resting state 

→ cycle repeats automatically, generating the rhythmic heartbeat 

Na sneaks in → Ca sparks → K exits → heartbeat restarts

pacemaker potential vs action potential in cardiac muscle

pacemaker potential: gradual depolarization to threshold, not a full action potential 

action potential: rapid depolarization → plateau → repolarization (longer duration)

major component of the ECG

P wave: atrial depolarization 

- atria depolarize → atria contract → push blood into ventricles

QRS complex: ventricular depolarization

- ventricles depolarize → ventricles contract → blood pumped out

T wave: ventricular repolarization

- ventricles repolarize → ventricles relax → heart resets for next cycle

P = Push Atria

QRS = Squeeze ventricles

T = Take a break

cardiac cycle

one full heartbeat (atria + ventricles contract and relax to move blood)

systole

contraction

South Carolina/Sweet Caroline

diastole

relaxation

Phases of the cardiac cycle

P.A.C.E.R

Passive 

Active

Contract

Eject 

Relax

Passive Ventricular Filling (1st phase)

atria: relaxed

ventricles: relaxed

blood flow: from atria to ventricles naturally

ECG: between T & next P wave

Active Ventricular filling (2nd phase)

atria: contract

ventricles: relaxed

blood flow: atria push remaining blood into ventricles

ECG: P wave (atrial depolarization)

Isovolumetric Contraction (3rd phase)

atria: relaxed

ventricles: contract

blood flow:  all valves closed; pressure rises but no blood leaves

ECG: start of QRS (ventricular depolarization)

Ejection (4th phase)

atria: relaxed

ventricles: contract

blood flow: semilunar valves open; ventricles push blood out to aorta/pulmonary trunk

ECG: QRS continues 

Isovolumetric Relaxation (5th phase)

atria: relaxed

ventricles: relaxed

blood flow: all valves closed; ventricles relax 

ECG: T wave (ventricular repolarization)

heart sounds

S1 = AV valves close (at start of ventricular contraction) (LUB)

S2 = Semilunar valves close (at end of ventricular contraction) (DUB)

intrinsic vs extrinsic control of heart rhythm

intrinsic: heart’s own properties / inside job (SA node)

extrinsic: external control (nerves/hormones)

preload & heart rhythm

preload: the amount of blood in ventricle before contraction

increases stroke volume: more preload → more stretch of heart muscle → stronger contraction → higher stroke volume 

more stretch = more squeeze 

stroke volume

the amount of blood pumped out of a ventricle with each beat

blood pumped per beat

single squeeze

sympathetic nervous activity & heart rhythm

increases heart rate

increases contractility

Sympathetic = Speeds up

contractility 

the strength of ventricular contraction 

how hard the heart squeezes

Parasympathetic nervous activity & heart rhythm

decreases heart rate (via vagus nerve)

Parasympathetic = Pumps down 

Epinephrine/Norepinephrine & heart rhythm

increases heart rate, contractility, stroke volume

pulmonary circulation

transports blood from the right ventricle to the lungs for gas exchange (blood gets oxygen) and then returns it to the left atrium

right → lungs → left

systemic circulation

transports blood from the left ventricle to the body tissues to supply oxygen and nutrients, then returns deoxygenated blood to the right atrium 

Left → Body → Right

coronary circulation

part of the systemic pathway

heart feeds itself from the aorta 

1) arteries bring oxygen-rich blood to the myocardium 

2) veins remove deoxygenated blood from the heart and drain it into the coronary sinus (which empties into the right atrium)

Pulmonary arteries + veins VS systemic arteries + veins

pulmonary:

arteries carry deoxygenated blood

veins carry oxygenated blood

systemic:

arteries carry oxygenated blood

veins carry deoxygenated blood

Pulmonary is flipped, systemic is standard

A blood cell is returning to the heart from the lungs. List in order the chambers, valves, and vessels the cell will pass through

1)     Oxygenated blood returning from lungs

2)     Pulmonary veins

3)     Left atrium

4)     Left ventricle

5)     Aorta

6)     Brain

7)     Systemic veins

8)     Right atrium

9)     Right ventricle

10)  Pulmonary trunk

11)  Lungs

if a heart murmur involves the aortic valve, how would this impact circulation

aorta leaks → weak systemic flow

backflow into the left ventricle will decrease systemic circulation

if a heart murmur involves the mitral valve, how would this impact circulation

left atrium backflow → poor ventricular filling

from sitting to standing, how is heart rate affected

standing up = HR increases to fight gravity & maintain blood flow

calcium channel blockers

calcium channel blockers = less Ca²⁺ in = slower, weaker beat = lower BP

AV (atrioventricular) valves

betwwen atria and ventricles

right : tricuspid

left : bicuspid/mitral

TRI before you BI (Tricuspid on right, Bicuspid/Mitral on left)

prevent blood from flowing back into atria when ventricles contract

Semilunar valves

between ventricles and arteries leaving the heart

right : pulmonary

left : aortic

prevent blood from flowing back into ventricles after its ejected