the heart Flashcards
general facts about the heart
- beats 100,000 time/day
- 70 bpm
- pumps 1.5 million gallons/year
- 2.9 gallons/minute
pulmonary circuit
RA receives blood from superior and inferior vena cava –> open tricuspid valve –> blood goes into RV –> pulmonary semilunar valve opens –> tricuspid closes –> RV contracts and pushes blood through pulmonary artery –> blood goes to the lungs –> gets oxygenated
systemic circuit
blood enters LA from the 2 pulmonary veins –> mitral valve opens –> LA contracts and blood enters the LV –> mitral closes –> LV contracts –> aortic semilunar valve opens –> blood leaves the aorta –> blood goes through ascending and descending aortic tracts
the branches of the aortic artery
- brachiocephalic
- left common carotid
- left subclavian
brachiocephalic branches
- right common carotid
- right subclavian
pericardium
contains the heart and is part of the 3 serous membranes (PPP)
visceral –> touches the heart
parietal –> outer pericardium
pericarditis
inflammation of the pericardial fluid
this creates resistance for the heart to beat and increases blood pressure
treat w/ aspiration
epicardium
external heart surface
myocardium
cardiac muscle cells
endocardium
internal lining of the heart
cardiac muscle characteristics
- branching fibers unlike SKM
- intercalated discs for communication
- aerobic respiration
- light striation
- centralized nuclei (mononucleic)
- contract involuntarily
intercalated discs
structures unique to the heart that allow for the spread of electrical signals between cardiac fibers
gap junctions
held together by desmosomes
the fibrous skeleton of the heart
the fibrous skeleton maintains the heart’s volume and prevents over expansion
these are fibrous sheets between each muscle layer
hypertension
if the fibrous skeleton is stretched, the heart can become enlarged and one can go into heart failure
fibrous skeleton functions
- stabilize cardiac cells and heart valves
- support myocardial blood vessels and nerves
- distribute forces of contraction
- prevent over expansion
- helps heart recoil
- isolate atrial cells from ventricular cells
heart’s position in the thoracic cavity
- lies in the mediastinum
- apex falls on the midclavicular line of the 5th intercostal space
- heart is twisted slightly to left
- you see more of the RA and RV from the front
3 sulci of the heart
- coronary sulcus
- anterior interventricular sulcus
- posterior interventrcular sulcus
coronary sulcus
separates the atria from the ventricles
the left coronary immediately branches
interarterial and interventricular septum
separates the LA and RA
separates the LV and RV
moderator band
sits between the RV’s myocardium and septum
prevents over expansion of the RV bc it’s thinner than the LV
signals to the papillary muscle to contract and close the tricuspid valve
chordae tendineae
tightens to close the tricuspid valve during ventricular systole
prevents back flow into the RA
coronary sinus
empties into the right atrium
receives blood from the greater and middle cardiac veins
pectinate muscle
part of the RA, helps with contraction
fossa ovalis
fetal remnant of the foramen ovale
meaty ridges of the heart
some blood is kept in the ventricle after systole
systole
contraction (120 mmHg)
semilunar valves open
AV valves close
diastole
relaxation (80 mmHg)
semilunar valves close
AV valves open
S1 and S2 sounds
closing of the valves (lub dub)
S1 –> close AV valves
S2 –> close semilunar valves
at no point do all the valves close at the same time
incompetence/regurgitation
if the AV valves don’t close and some blood goes back into the atria during ventricular systole
can be heard as an audible sound
blood vessels in the fat
prevents kinking of these vessels as the heart contracts
RCA (right coronary artery)
- right marginal branch
- posterior interventricular branch
- arterial branches
- conducting system branches
gives the posterior branch
middle cardiac vein runs with the posterior branch
LCA (left coronary artery)
- circumflex branch
- left marginal branch
- anterior interventricular branch
- posterior left ventricular branch
gives the anterior branch
greater cardiac vein runs with the anterior branch
2 types of conducting fibers of the heart
- nodal cells
- conducting fibers
nodal cells
- set the rate of contractions
- automatically depolarize
ex… SA node and AV node
conducting fibers
- distribute the contractile stimulus to the myocardium
SA node
- within the RA
- cardiac pacemaker
- 80-100 action potentials/min
AV node
- also within the RA floor
- 80 - 100 action potentials/min
ACh on HR
bradycardia
NorE on HR
tachycardia
SA node to AV node signal
atria contract
cardiac event summary
- SA node –> AV node = atrial contraction
- AV node –> AV bundle
- AV bundle –> right and left bundle branches
- bundle branches –> purkinje fibers = ventricles contract
p wave
atrial systole
qrs complex
ventricular systole
t wave
ventricular diastole
isometric contraction phase
slight contraction but not enough to open the semilunar valves
effective contraction phase
enough contraction to open the valves
isometric relaxation
all chambers are relaxed
ANS on heart pace
innervation from the ANS on the SA node, AV node, cardiac cells and smooth muscles of cardiac blood vessels can change the heart rate
NorE on heart contraction
increases the force of contraction
ACh on heart contraction
decreases force of contraction
CIC on HR
decrease HR
parasympathetic, CN X involved
CAC on HR
increase HR
sympathetic
afferent signaling from the heart
to the CNS
by CN IX and X
efferent signaling of the heart
from the CNS
by CN X –> decrease HR
by cardiac sympathetic nerve –> increase HR
example of CN X slowing down HR
if afferent signaling and baroreceptors tell the CNS the BP is too high
CN X will slow down the HR by acting on the SA and AV node
vagal escape phenomenon
happens only when CN X tries to slow down the HR due to increased BP
it DOES NOT touch the ventricles bc this can affect organs who need the ventricles to keep pumping blood
