A&P II Exam #2 (CH 18 and 19) - Questions

The Cardiovascular System (Heart) and The Lymphatic System

name the coverings of the heart and describe the functions of the fibrous pericardium

pericardium - double-walled and surrounds the heart

• fibrous pericardium 

  • superficial layer

  • protection

  • anchors heart to surrounding structures

  • prevents overfilling

• serous pericardium

  • deep, double-layered

  • parietal layer - lines internal surface of fibrous pericardium

  • visceral later (epicardium) - external surface

  • pericardial cavity - filled with serous fluid (allows for heart to work without friction

describe the three layers of the heart wall. What is the function of the myocardium

epicardium - visceral layer of serous pericardium

myocardium - layer that actually contracts

endocardium - sheet of squamous endothelium

describe the functions of the four heart chambers

2 atria - entryways

• receives blood

• small and thin-walled (only needs to push to ventricles, gravity also helps)

• sits above ventricles

• contains auricles - small, wrinkled, protruding appendages, increases atrial volume

2 ventricles - underside

• discharging chambers - actual pumps of heart

• thicker myocardium (pump to rest of body)

• trabeculae carneae - irregular ridges of muscles that mark the internal walls

• papillary muscles - plays a role in valve function, project into the ventricular cavity 

name each chamber and provide the name and general route of its associated great vessel(s)

RA

• posterior wall is smooth

• anterior wall contains pectinate muscles

• may contain fossa ovalis

• superior vena cava, inferior vena cava, coronary sinus

LA

• mostly smooth

• pectinate muscles found only in the auricles

• may contain fossa ovalis

• four pulmonary veins - blood from the lungs to heart

RV 

• chamber closest to the surface

• pumps blood to pulmonary trunk

LV

• majority of posteroinferior surface of heart

• pumps blood to aorta

name the three veins which return blood to the RA

superior vena cava, inferior vena cava, and coronary sinus

name the heart valves and describe their location, function, and mechanism of operation

atrioventricular (AV) valves - prevents backflow to atria when ventricles contract

• tricuspid - right AV, 3 cusps

• bicuspid (mitral) left AV, 2 cusps

  • BOTH contains chordae tendineae (heart strings)

semilunar (SL) valves - prevents backflow from major arteries back to ventricles 

• pulmonary SL valve - RV to pulmonary trunk, 3 cusps

• aortic SL valve - LV to aorta, 3 cusps

what is the function of the chordae tendineae

anchors cusps of AV valves to papillary muscles

• hold valve flaps in closed position

• prevents flaps from everting back to atria

• allows unidirectional blood flow

trace the pathway of blood through the heart

pulmonary circuit

• SVC and LVC and coronary sinus → RA → tricuspid valve → RV → pulmonary semilunar valve → pulmonary trunk → pulmonary arteries → lungs

systemic circuit 

• four pulmonary veins → LA → mitral/bicuspid valve → aortic semilunar valve → aorta → body 

true or false - veins always carry oxygen-poor blood, and arteries oxygen-rich blood

false

• pulmonary arteries does not contain oxygen rich blood (away from heart, towards lungs)

• pulmonary veins contain oxygen rich blood (away from heart, towards body)

name the major branches and describe the distribution of the coronary arteries

what is their function

coronary arteries

• left coronary arteries

  • anterior interventricular artery - supplies interventricular system and septum and anterior walls of both ventricles

  • circumflex artery - supplies LA and posterior wall of LV

• right coronary arteries

  • right marginal artery - supplies myocardium of lateral right of heart

  • posterior interventricular artery - runs to apex of heart and supplies posterior interventricular walls (merges with AIA at the apex of the heart) 

coronary veins

• cardiac veins collect blood from capillary beds

• coronary sinus - empties into RA 

  • great cardiac vein - anterior interventricular sulcus

  • middle cardiac vein - posterior interventricular sulcus

  • small cardiac vein - right interior margin 

what is the result of coronary artery blockade

myocardial infarction (heart attack)

• prolonged coronary blockage

• cells die - amitotic heart cells are replaced with noncontractile scar tissue 

*angina pectoris (choked chest) 

• thoracic pain due to fleeting deficiency in blood delivery to myocardium

• weakened cells, not dead

what is the coronary sinus

returns deoxygenated blood from coronary veins, drained into the RA

how does the structure and function of cardiac muscle cells differ from skeletal muscle fibers

not in-depth explanations

some cardiac muscle cells are self-excitable

heart contracts as a unit

uses both SR and EF calcium to contract

• skeletal only uses SR to contract

NO tetanic contractions (build up) in cardiac muscles

heart relies on O2 respirations 

• can use other pathways, but NEEDS O2

what structures can you find in the intercalated discs of cardiac cells

what is their function

gap junctions

• allows ions to pass cell to cell, electrically couple adjacent cells

• allows heart to be a functional syncytium (single coordinated unit)

desmosomes

• holds cells together, prevents cells from separating from contraction 

what is a functional syncytium

which structures of the intercalated discs allow the myocardium to function as a functional syncytium

a single coordinated unit - gap junctions (passage of ions, electrically connected)

calcium is needed for muscle contraction, what is the source of calcium for skeletal and cardiac muscle fiber contraction

cardiac muscle cells use both SR and EF for contraction

• skeletal muscle does not use EF calcium for contraction 

what are the cardiac pacemaker cells and what is their function

specialized cells that have the ability to depolarize spontaneously

• unstable resting potential - continuously depolarize 

• pacemaker potential - the spontaneously changing membrane potential that initiate action potential trigger rhythmic contractions 

name the function of the SA node

name the components of the conduction system of the heart and their location trace the conduction pathway

sinoatrial node, pacemaker, sinus rhythm

• initiates action potential

why are the impulses delayed at the AV node

which modifications are responsible for this delay

due to lower number of gap junctions and small diameter of muscle fibers

• allows atria to complete their contraction before ventricles contract

draw the pacemaker and action potentials of cardiac pacemaker cells

indicate which ion channels are open/closed during:

• pacemaker potential

• depolarization

• repolarization

pacemaker potential

• slow sodium channels open, NA+ enters cell

• potassium channels are closed

• membrane potential becomes less negative

depolarization/action potential

• calcium channels open (Ca2+ enters cell) - voltage gated (sodium channels)

• membrane potential becomes less negative FASTER

repolarization

• calcium channels close

• potassium channels open, K+ leaves cell

• membrane potential becomes more negative 

define the pacemaker potential

which event causes the pacemaker potential

the spontaneously changing membrane potential that initiate action potential trigger rhythmic contractions

• opening of slow sodium channels 

draw the action potential of contractile cardiac muscle cells

indicate which ion channels are open/closed during:

• depolarization

• plateau phase

• repolarization

depolarization/action potential

• fast voltage gated sodium channels open

• Na+ enters the cell

• MP becomes less negative, more positive

• immediate depolarization

plateau

• potassium channels start opening (exits cell)

• slow calcium channels open (enters cell)

• MP SLOWLY becomes more negative 

  • allows for a longer refractory period 

  • prevents tetanic contractions 

repolarization

• inactivated Ca2+ channels

• potassium channels open up (K+ leaves the cell)

• MP becomes more negative 

describe and compare action potentials in cardiac pacemaker and contractile cell

the influx of Ca2+ that produces rising phase of action potential

• pacemaker cells → slow, Ca2+

• contractile cell → fast, Na+

compare the actions potential in cardiac and skeletal muscle fiber

skeletal - action potential is 1-2 milliseconds

cardiac - AP is >200 milliseconds 

• plateau - slow Cs2+ entering the cell 

• allows for an effective pump 

name one important consequence of the long plateau phase observed in contractile cell

cardiac muscle stays contracted longer due to Na+ channels staying in a longer inactive state

• allows for efficient ejection of blood 

• prevents tetanic contractions

• slow calcium channels also plays a role (Ca2+ flows in)

can the basic rhythm of the heart be modified

yes - changes in lifestyle (ex: exercise), medications, pacemakers, AED, caffeine, alcohol, body temperature

• autonomic nervous system - cardiac centers in medulla oblongata

  • cardioacceleratory center - sympathetic trunk to increase heart rate and force (innervates SA and AV nodes, heart muscles and coronary arteries 

  • cardioinhibitory center - parasympathetic signals via vagus nerve to decrease rate (innervate mostly the SA and AV nodes)

which parts of the conduction system are innervated by the autonomic nervous system

cardioacceleratory center

• medulla oblongata → thoracic spinal cord → sympathetic trunk → SA and AV nodes, heart muscles and coronary arteries 

• cardioinhibitory center

cardioinhibitory center

• medulla oblongata (dorsal motor nucleus of vagus) → SA and AV nodes

what is an electrocardiogram

draw a diagram of a normal electrocardiogram tracing

name the individual waves and intervals, and indicate what each represents

a graphic recording of electrical heart activity

• P wave: depolarization of SA node and atria

• QRS complex: ventricular depolarization and atrial repolarization

• T wave: ventricular repolarization

• P-R interval: beginning of atrial excitation to beginning of ventricular excitation

• S-T segment: entire ventricular myocardium depolarized

• Q-T interval: beginning of ventricular depolarization through ventricular repolarization

heart abnormalities can be detected on an ECG tracing, how would enlarged ventricles, a heart attack and an nonfunctional SA node show in an ECG tracing

enlarged ventricles - enlarges R waves

heart attack- electrical activity is disorganized

nonfunctional SA node - P waves are absent, AV node paces heart (slower bpm - 40 to 60 bpm)

true or false - the cardiac cycle includes all events associated with the blood flow through the heart during one complete heartbeat - atrial systole and diastole followed by ventricular systole and diastole

true