Chapter 19: Heart Flashcards
myocardium is composed of __________________ tissue
cardiac muscle tissue
cardiac muscle cells are ________, _____________, and ____________
short, branched and striated
cardiac muscle cells house how many nuclei?
one or two
cardiac muscle cells are supported by _____________________ tissue called _______________
areolar connective tissue called endomysium
sarcolemma
- plasma membrane
- invaginates to form t-tubules extending into the sarcoplasmic reticulum
sarcoplasmic reticulum
- contains calcium
- surrounds bundles of myofilaments
the sarcolemma folded at connections between cells do what?
- increase structural stability
- facilitates communication between cells
cells are connected with __________________
intercalated discs
desmosomes
- join cells with protein filaments
- transfer of electrolytes b/w of the cells
- for structural integrity
gap junctions
electrically join cells and allow ion flow to make each heart chamber a functional unit
action potential is the rapid release of _____ and rapid absorption of _____
K+/Na+
ATP in cardiac muscle is used to/for:
- activate myosin
- calcium pumps require ATP
metabolism of cardiac muscle has a
high demand for energy
cardiac muscle has a high demand for energy because
- extensive blood supply
- numerous mitocondria
- myoglobin and creatine kinase
i know this doesn’t make sense but i hqd to fit it into a card somehow
cardiac muscle is able to use different types of which fuel molecules
- fatty acids
- glucose
- lactic acid
- amino acids
- ketone bodies
cardiac muscle mostly relies on ______________ metabolism
aerobic
because cardiac muscle relies mostly on aerobic metabolism,
it makes it susceptible to failure when ischemic
ischemic
oxygen is low
the heart rest between how many beats
2
how much of the PNS is made up of the vagus nerve
75%
perfusion
the delivery of blood per unit time of gram per tissue
venae cavae
drain deoxygenated blood into the right atrium
pulmonary trunk
receives deoxygenated blood pumped from the right ventricle
pulmonary veins
drain oxygenated blood into left atrium
right atrioventricular (AV) valve
between the right atrium and right ventricle, also known as the tricuspid valve
pulmonary semilunar valve
between right ventricle and pulmonary trunk
left atrioventricular (AV) valve
between the left atrium and left ventricle; also known as bicuspid valve or mitral valve
aortic semilunar valve
between left ventricle and aorta
pulmonary circulation
includes the movement of blood to and from the lungs for gas exchange
systematic circulation
includes the movement of blood to and from the systematic cells/the body
epicardium
outermost heart layer and is also called the visceral pericardium; composed of simple squamous epithelium
myocardium
middle layer of the heart wall and composed of cardiac muscle
endocardium
innermost layer of the heart wall; composed of simple squamous epithelium and underlying areolar connective tissue
conduction system
initiates and propagates an action potential
the conduction system contains specialized
cardiac muscle cells that have action potentials but do not contract
conduction systems activity is influenced by
the autonomic nervous system
sinoatrial (SA) node
located high in the posterior wall of the right atrium
the sinoatrial node is the ______________ of the heart
pacemaker
atrioventricular (AV) node
located on the floor of the right atrium
the atrioventricular node is the __________________ of the heart
backup pacemaker
atrioventricular (AV) bundle
- extends from AV node through interventricular septum
- divides into left and right bundles
- also known as bundle of His
Purkinje fibers
- extend from left and right bundles at heart’s apex
- course through walls of ventricles
white meat/muscles
fast twitch
red meat/muscles
slow twitch
the nerves of the heart are made of
modified muscle cells
the nerves of the heart are ___________________
self-polarizing
cardiac center of the medulla oblongata contains __________________ and ____________________ centers
cardioacceleratory and cardioinhibitory centers
the cardiac center receives signals from ________________ and _________________ in the cardiovascular system
baroreceptors and chemoreceptors
the cardiovascular system sends signals via the __________________ and ____________________ pathways
sympathetic and parasympathetic
parasympathetic innervation
decreases heart rate; “rest and digest”
the parasympathetic innervation starts
at medulla’s cardioinhibitory center; vagal tone
sympathetic innervation
increases heart rate and force of contraction; “fight or flight”
the sympathetic innervation starts
at the medulla’s cardioacceleratory center
cardiac muscle cells
initiate action potentials and contract
SA nodal cells
initiate heartbeat
RMP for the SA nodal cells
-60mV
pacemaker potential
ability to reach the threshold without stimulation
vagal tone
parasympathetic activity relayed by the vagus nerve
- keeps heart rate slower
the process of the conduction system of the heart
1- SA node conducts AP
2- AP is distributed through atria, reaches AV node, both atria contract
3- AP is delayed at the AV node, delay allows ventricles to fill
4- AP travels through AV bundle to bundle branches to purkinje fibers
5- AP spreads through ventricles, cells of two ventricles contract almost simultaneously
wave summation
twitches that overlap
tetany
sustained contraction
cardiac muscle cells have a RMP of
-90mV (very polarized)
cardiac muscle cells contain 3 specific voltage-gated channels
1- voltage-gated Na+ channels
2- voltage-gated Ca2+ channels
3- voltage-gated K+ channels
depolarization
the change from a relatively negative membrane potential to a relatively positive membrane potential
what happens during depolarization
- impulse opens voltage-gated Na+ channels
- Na+ enters the cell, changing membrane potential from -90mV to 30+ mV
- voltage-gated Na+ channels start to inactivate
plateau
leveling off
what happens during the plateau
- depolarization opens voltage-gated K+ and voltage-gated Ca2+ channels
- K+ leaves cardiac muscle cell as Ca2+ enters
- stimulates sarcoplasmic reticulum to release more Ca2+
- membrane remains depolarized
repolarization
allows a cardiac muscle to propagate a new action potential when the cardiac muscle is simulated again
what happens during repolarization
- voltage-gated Ca2+ channels close while K+ channels remain open
- membrane potential goes back to -90mV
Ca+ makes ATP ___________
last longer
cardiac ATP is longer because of
the plateau phase
can cardiac muscle exhibit tetany?
no
unlike skeletal muscle, cardiac cells have a long _______________
refractory period
cardiac muscle cells plateau phase leads to a refractory period of about ________
250 ms
cell cannot fire a new impulse during
the refractory period
electrocardiogram (ECG/EKG)
skin electrodes detect electrical signals of cardiac muscle cells
P wave
reflects electrical charges associated with atrial depolarization originating in SA node; atria are starting their AP
QRS complex
- electrical changes associated with ventricular depolarization
- atria also simultaneously repolarizing
T wave
electrical change associated with ventricular repolarization; end of activity in ventricles
P-Q segment
associated with atrial cells’ plateau
- ATRIA ARE CONTRACTING
S-T segment
associated with ventricular plateau
- VENTRICLES ARE CONTRACTING
plateau phases
P-Q segment and S-T segment
atrial depolarization
- recorded as the P wave
- muscle cells of atria stimulated to contract
atrial plateau
- recorded as PQ segment
- muscle cells of atria contract and relax
atrial repolarization
not visible on ECG
ventricular depolarization
- recorded as the QRS wave
- muscle cells of ventricles stimulated to contract
ventricular plateau
- recorded as ST segment
- muscle cells of ventricles contract and relax
ventricular repolarization
recorded as T wave
arrhythmia
any abnormality in the heart’s electrical activity
heart blocks
impaired conduction
AP conduction
problem in the conducting system
cardiac cycle
all events in heart from the start of one heart beat to the start of the next
systole
contraction
diastole
relaxation
blood moves ________ its pressure gradient
down (high to low)
EDV (end-diastolic volume)
- volume of blood left in the ventricle at the end of diastole
- blood volume to be “squeezed”
SV (stroke volume)
the amount of blood pushed out during ventricular contraction
ESV (end-systolic volume)
volume of blood in ventricle at the end of systole
atrial contraction and active ventricular filling
1 - SA node starts atrial contraction
2 - atria contract, pushing remaining blood into ventricles
3 - semilunar valves are closed
4 - ventricles filled to EDV
isovolumetric ventricular contraction
1- early systole
2- ventricles contract
3- pressure rises
4- AV valves are pushed closed
5- semilunar valves still closed
ventricular ejection
1- late systole
2- semilunar valves forced open as blood moves from ventricles to arterial trunks
how to find stroke volume
SV(mL)=EDV-ESV
isovolumetric ventricular relaxation
1- early diastole
2- ventricles relax and start to expand, lowering pressure
3- blood closes semilunar valves
4- AV valves remain closed
the diastolic pressure in a BP reading is the pressure the
left ventricle has to overcome to open semilunar valves
atrial relaxation and passive ventricular filling
1- late diastole
2- all heart chambers are relaxed
3- AV valves open and blood flows into ventricles passively
4- semilunar valves remain closed
ventricular balance
1- equal amounts of blood are pumped by left and right sides of the heart
edema
swelling of fluid around the heart
cardiac output (CO)
amount of blood pumped by a single ventricle in one minute
cardiac output is measured in
liters per minute
cardiac output is determined by ________________ and _______________
heart rate and stroke volume
equation for CO
HR x SV= CO
CO must
meet tissue needs
cardiac reserve
the potential of what your heart can do
chronotropic agents
change heart rate by altering the activity of nodal cells
positive chronotropic agents
increase heart rate
sympathetic innervation of SA nodal cells (positive chronotropic agents)
- causes adrenal to release NE and epinephrine
- NE and EPI bind to nodal cells and increase their firing rate
- G-protein is activated and forms a second messenger
- activates kinase and Ca2+ channels to open
what factors can increase heart rate at different steps within the sympathetic innervation of SA nodal cells
- TH
- nicotine
- cocaine
- caffeine
negative chronotropic agents
decrease heart rate
parasympathetic innervation of SA nodal cells (negative chronotropic agents)
- PS axons release acetylcholine
- ACh opens K+ channels and K+ exits the cell making it more negative
beta-blocker drugs
used to treat high BP
autonomic reflexes
- baroreceptors and chemoreceptors send signals to the cardiac center
- cardiac center influences SNS and PNS to alter output as needed
atrial reflex
protects the heart from overfilling
venous return
volume of blood returned to the heart
inotropic agents
change stroke volume and alter contractility
positive inotropic agents
increases contractility by increasing available Ca2+
negative inotropic agents
decreases contractility by decreasing available Ca2+
afterload
resistance in arteries to ejection of blood by ventricles
atherosclerosis
plaque in vessel linings
heart rate depends on
chronotropic agents
stroke volume generally depends on
state of myocardium
increased afterload _____________ stroke volume
decreases
does the size of the heart affect SV?
yes
bradycardia
slow heart rate
tachycardia
fast heart rate
ectopic pacemaker
group of cardiac muscle cells that have the ability to spontaneously depolarize and act as the pacemaker
atrial fibrillation
chaotic timing of atrial action potentials
ventricular fibrillation
chaotic electrical activity in ventricles
