10.3 The Human Heart Flashcards
describe the human heart (location, strcuture)
cone shaped, muscular organ about the size of a fist
- located between the lungs directly behind sternum and tilted to apex is orienteted to body’s left
- major portion (myocardium) consists largely of cardiac muscle tissue
- heart lies within pericardium (thick serous membrane that secretes small quantity of lubricating liquid)
- inner surface lined w endocardium (a membrane composed of endothelial tissue and connective tissue)
septum
separates heart into right side and left side
atria
upper thin walled chamber
ventricles
lower thick walled ventricles, pump blood to lungs and body
atrioventricular valves
two valves that prevent the backflow of blood that lie between atria and ventrivles
- right side: tricuspid
- left side: bicuspid (mitral)
chordae tendineae
strong fibrous strings that support AV valves
semilunar valves
flaps resemble half moons
- right side: pulmonary semilunar valve between right ventricle and pulmonary trunk
- left side: aortic semilunar valve between left ventricle and aorta
what is the path of blood to the lungs from the heart
- superior (anterior) vena cava and inferior (posterier) vena cava carry O2 poor/CO2 high blood from body enter right atrium
- right atrium sends blood through tricuspid AV valve to right ventricle
- right ventricle sends blood through pulmonary semilunar valve into pulmonary trunk through the pulmonary arteries to the lungs
what is the path of blood to the body from the heart
- four pulmonary veins carry O2 rich blood to left atrium
- left atrium sends blood through bicuspid mitral AV valve to left ventricle
- left ventricle sends blood through aortic semilunar valve into aorta to the rest of the body
why is the heart a double pump
-right ventricle sends blood to lungs and left ventrice sends blood to rest of body
why are the walls of the left ventricle thicker than the walls of the right ventricle
-left ventricle has the harder job to pump blood to the entire body
what is cardiac output
volume of blood the left ventricle pumps per minute
describe the pressure of the vessels
- strongest pressure in aorta because left side is stronger pump
- BP decreases as cross sectional area of arteries and then arterioles increases
what is a pulse
wave effect that passes down the walls of arteries when the aorta expands and recoils with each ventricular contraction
-arterial pulse determine heart rate
describe the cardiac cycle
- each heartbeat
- first two atria contract at the same time then two ventricles contract at the same time then all chambers relax
define systole and diastole
systole: contraction of heart muscle
diastole: relaxation of heart muscle
describe the “lub-whoosh-dub” sound of the heart
“lub”: longer and lower pitched, caused by vibrations occuring when the AV valves close due to ventricular contractions
heart murmur/whoosh : caused by blood flowing back through an ineffective bicuspid mitral AV valve
“dub”: sharper and shorter dub when semilunar valves close due to back pressure of blood in arteries
describe the intrinsic control of heartbeat (nodal activity)
- rhythmic contraction of atria and ventricles due to internal conduction system of heart
- sinoatrial node initiates heartbeat and sends out an excitation impulse every 0.85secs, causing atria to contract
- impulse reaches the atrioventricular node, a slight delay allows atria to finish contraction before ventricles begin to contract
- signal for ventricles to contract travels from AV node through atrioventricular bundles before reaching smaller Purkinje fibres
where is the sinoatrial and atrioventricular nodes located
sinoatrial: upper dorsal wall of right atrium
atrioventricular: base of right atrium near septum
why is the sinoatrial node called the pacemaker
keeps heartbeat regular
-if SA node fails to work properly, heart still beats due to impulses generated by the AV nose but beat is slower
what can be used to correct a condition in which the SA node fails to work
an artificial pacemaker may be implanted that gives an electrical stimules to the heart every 0.85 seconds
describe the extrinstic control of the heartbeat
a cardiac control in the medulla oblongata can alter autonomic nervous system
- parasympathetic: promotes functions of a resting state, decreases SA and AV nodal activity when inactive
- sympathetic: responses to increased activty or stress, increases SA and AV nodal activity when active or excited
name hormones that stimulate the heart and where they are realeased from
- epinephrine and norepinephrine are realeased by the adrenal medulla
- when frightened heart pumps faster and stronger due to sympathetic stimulation and realease of epinephrine and norepinephrine
what is an electrocardigram
a recording of the electrical changes that occur in the myocardium during cardiac cycle
-ions in body fluids conduct electrical currents and change the elctrical changes can be detected on skins surface, electrodes placed on chest connected to wires to instrument that can detect electrical changes
describe a normal ECG
P wave: before atrial contraction
QRS complex: just before ventricular contraction
T: ventricles recovering from contractions
what is atrial fibrillation and what are the symptoms
- instead of heart generating single, regular impulses from AV node, mulitple, chaotic impulses generated resulting in irregular fast heartbeat
- symptoms: palpitations (fluttering sensation in heart along with dizziness, weakness, chest pain)
what is ventricular fibrillation
- uncoordinated contraction of ventricles
- most commonly follows a heart attack, or overdose
- a heart in VF not pumping blood, must by defibrillated by applying a strong electrical current for a short period of time
- then SA node may be able to reestablish a coordinated beat
what is an automatic external defibrillator
small devices that can be used to determine whether a person is sufering from ventricular filbrillation, and administer an appropriate electrical shock to chest
