Anatomy and Physiology Flashcards
Layers of Heart Tissue:
Pericardium
Epicardium
Myocardium
Endocardium
Pericardium = fibrous protective sac
Epicardium = inner layer of pericardium
Mydocardium = heart muscle
Endocardium = smooth lining of inner surface and cavities of the heart
Heart Chambers:
Right Atrium
Right Ventricle
Left Atrium
Left Ventricle
RA: de-oxy blood from system via sup/inf vena cava
RV: pumps blood through pulmonary artery (low pressure)
LA: receives oxy blood via 4 pulmonary veins
LV: pumps blood via the aorta throughout entire systemic circulation; high pressure system
Atrioventricular Valves
Prevent backflow of blood into atria during ventricular systole; anchored by chordae tendinae to papillary ms *valves close when ventricle contracts
- Tricuspid = R heart valve
- Bicuspid (mitral) = L heart valve
Semilunar Valves
prevent backflow of blood from AORTA and PULMONARY arteries into ventricles during DIASTOLE
- Pulmonary = prevents R backflow
- Aortic = prevents L backflow
Cardiac Cycle, Define:
Systole:
Diastole:
Atrial Kick
Systole: period of ventricular contraction. End-systolic volume is # of blood in ventricles after systole; about 50 mL
Diastole: period of ventricular relaxation. End-diastolic volume is # of blood in ventricles after diastole; about 120mL
Atrial Kick: last 1/3 of diastole and completes ventricular filling = last 20-30% of EDV
Sinoatrial Node
Main pacemaker, 60-100 bpm
located @ jxn b/t superior vena cava and RA
sympathetic & parasympathetic input affecting rate and strength of contraction
Atrioventricular Node
Intrinsic firing rate 40-60 bpm
located @ jxn b/t RA and RV
merges w/ bundle of His
sympathetic and parasympathetic innervation
Hemodynamics - Stroke Volume (SV)
of blood ejected with each myocardial contraction; normal = 55-100mL/beat. Influenced by:
- Left Ventricular End Diastolic Volume (LVEDV) or pre-load (5-12 mmHg)
- Contractility
- After-load (force to overcome aortic pressure)
Hemodynamics:
Cardiac Output (CO) & Cardiac Index
of blood discharged from L or R ventricle/minute
- Avg adult @ rest = 4-5L/min
- CO = HR x SV
- Cardiac Index = CO divided by body surface = 2.5-3.5 L/min
Hemodynamics: Ejection Fraction (EF)
% blood emptied from ventricle during systole - clinically useful measure of LV function
- EF = SV/LVEDV
- Normal = >55%
Hemodynamics: Atrial Filling Pressure
Difference between venous and atrial pressures
- RA pressure decreased during strong vent. contraction (atrial filing enhanced)
- R atrial filling pressure is affected by intrathoracic pressure; decreases during inspiration, increases during cough or forced exhalation
- Venous return increases when blood volume expands and decreases during hypovolemic shock
Hemodynamics: Myocardial Oxygen Demand (MVO2)
Represents energy cost to the myocardium
- increases with activity, HR, or BP
- MVO2 = HR x SBP (RPP)
Parasympathetic Stimulation of Heart
(CHOLINERGIC)
- controlled by cardioinhibitory center - medulla oblongata
- via VAGUS nerve, cardiac plexus via acetylcholine
- slows rate/force of myocardial contraction; decreases metabolism
- causes coronary artery vasoconstriction
Sympathetic Stimulation (adrenergic)
- control located in medulla oblongata, cardioacceleratory center
- via cord segments T1-T4, upper thoracic cervical chain ganglia, innervates all but ventricular myocardium;
- Releases EPINEPHRINE and NOREPINEPHRINE
- causes ^ HR / Force contraction
Additional Control Mechanisms Cardiac Tissue
Ion Concentrations
-
Ions:
- hyperkalemia= dec F & wide PR/QRS, tall T
- hypkalemia= arrhythmias flat T, prolong PR/QT
- hypercalcemia= ^ heart actions
- hypocalcemia= decreased heart action
- hypermagnesemia=calcium blocker, arrhythmias/event
- hypomagnesemia=ventric arrhythmia, CA vasospasm, death
