Unit 6 Study Guide Flashcards
Epicardium
- outermost layer
- also called the visceral layer of serous pericardium
- composed of simple squamous epithelium and an underlying layer of areolar connective tissue
- as we age, the epicardium thickens as it becomes more invested with adipose connective tissue
- Heart receives nutrients from coronary vessels
Myocardium
- middle layer of the hart
- composed of cardiac muscle tissue
- thickest of the three layers
- contraction of this muscle generates the force necessary to pump blood
Endocardium
- covers the internal surface of the heart and external surface of the heart valves
- composed of simple squamous epithelium and an underlying layer of areolar connective tissue
- Epithelial layer of the endocardium is continuous with the epithelial layer of the endothelium - lines blood vessels
Atrioventricular Valves
Right:
- covers the right atrioventricular opening
- has three cusps (tricuspid)
Left:
- covers the left atrioventricular opening
- has two cusps (bicuspid)
When the cusps are open
allows blood to move from an atrium into the ventricle
when the ventricles contract
- blood is force superiorly as ventricular pressure rises, which causes AV valves to close.
AV valves
prevent blood flow back into the atrium
Semilunar valves
- pulmonary semilunar valve
- aortic semilunar valve
pulmonary semilunar valve
- located between the right ventricle and pulmonary trunk
aortic semilunar valve
- located between the left ventricle and the ascending aorta
The semilunar valves open when
- the ventricles contract and the force of blood pushes the semilunar valves open and blood enters the arterial trunks.
the semilunar valves close when
- the ventricles relax and the pressure in the ventricles becomes less than the pressure in an arterial trunk
- prevents back flow into the ventricle
function of the fibrous skeleton of the heart
- provides structural support at the boundary between the atria and the ventricles
- forms supportive fibrous rings to anchor the heart valves
- provides a rigid framework for the attachment of cardiac muscle tissue
- acts as an electrical insulator because it does not conduct action potentials and thus prevents the ventricle chambers from contracting at the same time as the atrial chambers.
sarcolemma
- invaginate to form T-tubules that extend to the SR.
T-tubules
- invaginate one per sarcomere and overlie Z discs.
sarcoplasmic reticulum
- surrounds bundles of myofilaments called myofibrils in cardiac muscle, but is less extensive than the SR in skeletal muscle and lacks both terminal cistern and a tight association with T-tubules.
myofilaments
- arranged in sarcomeres and appear striated.
Overlap of thick and thin filaments
- does not occur when cardiac muscles are at rest.
- occurs when cardiac muscle is stretched as blood is added to the chamber.
intercalated discs
link cardiac muscle cells mechanically and electrically.
desmosomes
- act as mechanical junctions to prevent cardiac muscle cells from pulling apart in times of stress/friction.
gap junctions
- provide a low-resistance pathway for the flow of ions between the cardiac cells. Allow an action potential to move continuously along the sarcolemma of cardiac muscle cells, resulting in synchronous contraction of that chamber - functional synctyium
conduction system
- electrical activity is initiated at the SA node, and an action potential is then transmitted through the conduction system
cardiac muscle cells
- the action potential spreads across the sarcolemma of the cardiac muscle cells, causing sarcomeres within cardiac muscle cells to contract.
- these events occur twice in cardiac muscle cells of the atria and then again in the ventricles
Nodal cells
- located in the SA node
- pacemaker cells
- initiate a heartbeat by spontaneously depolarizing to generate an AP
resting membrane potenital
-60 mV
autorhythmicity
- capable of depolarizing and firing an AP spontaneously without any external influence.
reaching threshold
- slow voltage-gated Na+ channels open (repolarization from previous cycle).
- Na+ flows into nodal cells, changing RMP from -60 mV to -40 mV which is threshold value
- without outside stimulation
depolarization
- changing of the membrane potential to threshold potential triggers opening of fast voltage-gated Ca2+ channels
- Ca2+ entry into nodal cells cause a change in the membrane potential from -40 mV to a slightly positive value (just above 0 mV)
repolarization
- calcium channels close and voltage-gated K+ channels open
- K+ flows out to change the membrane potential back to -60 mV.
- depolarization triggers the reopening of slow voltage-gated Na+ channels
sinoatrial node
- located in posterior wall of the atrium
- adjacent to the entrance of the vena cava
- initiate heartbeat
- pacemaker of the heart
atrioventricular node
- located on floor of the right atrium
- between right AV valve and opening for coronary sinus
atrioventricular bundle
- extends from the AV node into and through the interventricular septum
- divides into let and right bundles
Purkinje fibers
- extend from the left and right bundles beginning at the apex of the heart and continue through walls of the ventricles
cardiac cycle
- inclusive changes within the heart from the initiation of one heartbeat to the start of the next
systole
- contraction of a heart chamber
diastole
- relaxation of a heart chamber
Atrial systole
- atrial contraction and ventricular flying
- atria contract
- ventricles relax
- ventricular pressure less than atrial pressure
- ventricular pressure less than arterial trunk pressure
- AV valves open
- semilunar valves closed
Early ventricular systole
- atria relax
- ventricles contract
- ventricular pressure is greater than atrial pressure
- ventricular pressure is less than arterial trunk pressure
- AV valves closed
- semilunar valves closed
late ventricular systole
- atria relax
- ventricles
- ventricular pressure is greater than atrial pressure
- ventricular pressure is greater than arterial trunk pressure
- AV valves closed
- semilunar valves open
Early ventricular diastole
- atria relax
- ventricles relax
- ventricular pressure is greater than atrial pressure
- ventricular pressure is less than arterial trunk pressure
- AV valves closed
- semilunar valves closed
Late ventricular diastole
- atria relax
- ventricles relax
- ventricular pressure is less than atrial pressure
- ventricular pressure is less than arterial trunk pressure
- AV valves open
- semilunar valves closed
AV valves open because
- pressure exerted by blood filling the atria is greater than the pressure exerted by blood remaining in resting ventricles
Semilunar valves closed because
- the pressure exerted by the blood remaining in the filling ventricles is less than the pressure exerted by the blood in arterial trunks
AV valves remain closed because
- pressure exerted by blood remaining in filling ventricles is lower than pressure exerted by blood in arterial trunks
cardiac output
- the amount of blood that is pumped by a single ventricle is 1 minute
- liters per minute
- measure of effectiveness of cardiovascular system
cardiac output formula
Heart Rate X stroke volume
heart rate
number of beats per minute
stroke volume
volume of blood ejected during one beat
chronotropic agents
factors that change heart rate
positive chronotopic agents
- cause an increase in heart rate
- include sympathetic nerve stimulation and certain types of hormonal stimulation
thyroid hormone
- increase number of beta 1 adrenergic receptors
- makes nodal cells more responsive to epinephrine and norepinephrine
caffeine
- increases cAMP and heart rate
nicotine
- stimulates norepinephrine
cocaine
- inhibits reuptake of norepinephrine
- increase heart rate
- can lead to fast and erratic heart beat, possibly fatal
negative chronotopic agents
- decrease heart rate
parasympathetic innervation
- most importnat
- axons releasing Ach binds ot M2 muscarinic receptor
- binds voltage-gated K+ channels
- causes hyper polarization as K+ exits
- longer times for cells to reach threshold
- heart rate slowed
beta blocker drugs
- interfere with NE and Epi binding to beta receptors
- used to treat high blood pressure
stroke volume
- the volume of blood ejected per heartbeat
- dependent upon the volume of blood that enters that heart and the end of heart contraction
end diastolic volume
the volume of blood that enters that heart and the end of heart contraction
end systolic volume
- the blood remaining in the ventricle at the end of ventricular contraction
SV =
EDV-ESV
venous return
- volume of blood returned to heart via great veins
- increased venous return occurs with greater pressure of slower heart rate
- increases stretch of heart wall (preload), which results in greater overlap of thick and thin filaments within the sarcomeres
- additional cross bridges formed, and ventricles contract with greater force
- stroke volume increases
inotropic agents
- substances that act on myocardium to alter contractility
- alter the force of contraction at any given stretch of the cardiac cells.
positive inotropic agents
- increases Ca2+ concentration in sarcoplasm
- greater binding of Ca2+ to troponin of thin filaments within sarcomeres of myocardium, results in formation of additional cross bridges and ventricles contract with greater force.
- stimulation by sympathetic nervous system
negative inotropic agents
- decreases contractility by decreasing available Ca2+ and fewer numbers of cross bridges are formed
afterload
- resistance in arteries to the ejection of blood by ventricles
- pressure that must be exceeded before blood is ejected from the chamber
Right atrium and left atrium separated by
interatrial septum
right ventricles and left ventricles separated by
inter ventricular septum
right atrium
- takes in deoxygenated blood from tissues through the vena cava
coronary sinus
drains deoxygenated blood from the heart wall
right ventricle
- pumps deoxygenated blood through pulmonary trunk to pulmonary artery to the lungs
left atrium
- receives oxygenated blood through pulmonary vein
left ventricle
- pumps oxygenated blood through aorta to the rest of the body
- aortic semilunar valve positioned at the boundary of left ventricle and ascending aorta
spread of action potential through heart’s conductive system
- distributed through both atria and relayed to AV node
- delayed at AV node so atria contract before ventricles do
- travels from AV node through AV bundle to purkinje fibers
- spreads through ventricles via gap junctions
