Exam 4: The Heart Flashcards
Cardiovascular system
–Essential for life
–If it fails, often fatal outcome
–Composed of heart and blood vessels
–Circulates blood continuously to maintain homeostasis
Trasportation of the blood through the body
–Allows exchange of substances between capillaries and cells
–Perfusion
–Adequate perfusion
–Requires continual pumping of the heart and open vessels
Perfusion
delivery of blood per time per gram of tissue
Adequate Perfusion
sufficient blood delivered to maintain health of body cells
The Heart characteristics
–Center of the cardiovascular system
–Hollow, four-chambered organ
–Composed of two pumps
What are the two pumps that the heart is composed of
Right sided pump
Left sided pump
Right sided pump
–receives deoxygenated blood from body
–pumps it to the lungs
Left Sided Pump
–receives oxygenated blood from lungs
–pumps it to the body
What characterizes the left and right artium
Superior chambers for recieving blood
What characterizes the left and right ventricles
- inferior chambers for pumping blood away
- receive blood from respective atria
Heart: The Great Vessels functions
- transport blood directly to and from chambers
- continuous with each chamber
The Heart: The great vessels
pulmonary trunk
aorta
superior and inferior vena cava
Heart: Pulmonary Trunk Functions
- splits into pulmonary arteries
- receives deoxygenated blood from right ventricle
Heart: Aorta Function
•receives oxygenated blood from left ventricle
Heart: Superior and Inferior Vena Cava Function
•drain deoxygenated blood into right atrium
Heart: Pulmonary Veins
•drain oxygenated blood into left atrium
What are the 2 types of valves found in the heart?
Atriventricular
Semilunar
Atrioventricular Valves
- between atrium and ventricle of each side
- right AV valve
- left AV valve
Right AV valve
Tricuspid
Located between the right atrium and right ventricle
Left AV Valve
bicuspid or mitral
Located between the left atrium and left ventricle
Semilunar Valves Functions
- boundary between ventricle and arterial trunk
- open to allow blood to flow through heart
- close to prevent backflow
What are the two Semilunar Valves?
Pulmonary
Aortic
Where is the pulmonary smilunar valve located?
Between right ventricle and pulmonary trunk
Where is the aortic semilunar valve located?
Between left ventricle and the aorta
Circulation Routes: Pulmonary Circulation
- carries deoxygenated blood from right side of heart
- goes through blood vessels to the lungs
- pick up of oxygen and release of carbon dioxide
- back through vessels to left side of heart
Circulation Routes: Systemic Circulation
- moves oxygenated blood from left side of heart
- moves through vessels to systemic cells
- exchange of nutrients, gases, and wastes
- returns blood in vessels to right side of heart
What is the basic pattern for blood flow?
•right heart ► lungs ►left heart ► systemic tissues ► right heart
Pericardium
–Membrane surrounding and protecting the heart
–Confines while still allowing free movement
–2 main parts
What are the two parts of the pericardium?
- Fibrous pericardium
- Serous pericardium
Fibrous Pericardium
tough
inelastic
dense irregular connective tissue – prevents overstretching
protection
anchorage
Serous Pericardium
thinner
more delicate membrane double layer:
– parietal layer fused to fibrous pericardium
– visceral layer also called epicardium
What does the pericardial fluid do? Where is it secreted?
Reduces friction
secreted into pericardial cavity
What are the three layers of the heart wall?
Epicardium
Myocardium
Endocardium
Epicardium
(visceral layer of serous pericardium)
- outermost heart layer
- serous membrane of simple squamous epithelium
- underlying areolar connective tissue
Myocardium
- middle heart layer
- composed of cardiac muscle tissue
- thickest of three layers
- contraction generates force to pump blood
- may change in thickness with age
Endocardium
- covers internal surface of heart and external surface of valves
- composed of simple squamous epithelium
- underlying layer of areolar connective tissue
- continuous with blood vessel inner lining
What are the superficial features of the heart?
–Small, muscular organ
–Two smaller atria and two larger ventricles
–Sulci, grooves, containing coronary vessels
–Coronary sulcus
–Interventricular sulcus
Coronary Sulcus
- deep groove separating atria from ventricles
- extends around circumference of heart
Interventricular Sulcus
- groove separating ventricles
- extends from coronary sulcus toward heart apex
- anterior interventricular sulcus on anterior side
- posterior interventricular sulcus on posterior side
What can be seen from the anterior view of the heart?
–Right atrium and right ventricle prominent
–Right auricle
wrinkled, flaplike extension of right atrium
–Aorta and pulmonary trunk seen
–Small portion of left auricle
–Anterior interventricular and coronary sulci
what are the characteristics of cardiac muscle?
–Shorter and less circular than skeletal muscle fibers
–Branching
–Usually one centrally located nucleus
–Fibers connected by intercalated discs
–Mitochondria are larger and more numerous than skeletal muscle
–Same arrangement of actin and myosin
Fibers connected by intercalated discs
Desmosomes (hold fibers together) and gap junctions (allow action potential conduction from one fiber to the next)
What does the Heart’s conduction system consist of?
Sinoatrial (SA) Node
Atrioventricular (AV) Node
Atrioventricular (AV) Bundle
Purkinje Fibers
Sinoatrial Node (SA Node)
- in posterior wall of right atrium
- initiates heartbeat
- referred to as “pacemaker” of heart
Atrioventricular Node (AV Node)
- in floor of right atrium
- between right AV valve and coronary sinus opening
Atrioventricular (AV) Bundle
- extends from AV node though interventricular septum
- divides into left and right bundles
Purkinje Fibers
- extend from left and right bundles
- from apex of heart through walls of ventricles
Where is electrical activity initiated?
Sinoatrial (SA) Node
What is trasmitted throught the conduction system?
Action Potential
What are the Mechanical and Electrical events of the cardiac muscle cells?
- Depolarization
- Plateau
- Repolarization
- Refractory period
Depolarization
- action potential transmitted through conduction system
- triggers opening of fast voltage-gated Na+ channels in sarcolemma
- entrance of sodium into cardiac muscle cells
- resting membrane potential from -90 mV to +30 mV
- voltage-gated Na+ channels close to inactivated state
Plateau
- opening of voltage-gated K+
- K+ leaves cardiac muscle cells
- opening of slow voltage-gated Ca2+ channels in sarcolemma
- entrance of Ca2+ into cells
- stimulates sarcoplasmic reticulum to release more Ca2+
- no electrical change in sarcolemma
- remains in depolarized state
Repolarization
- closure of voltage-gated Ca2+ channels
- K+ remain open
- reversal of membrane potential back to -90 mV
Refractory Period time interval during which second contraction cannot be triggered
–Lasts longer than contraction itself
–Tetanus (maintained contraction) cannot occur
–Blood flow would cease
Systole
Contraction
Diastole
Relaxation
What are the steps shown on an EKG?
- Cardiac action potential arises in SA node
- Atrial contraction/ atrial systole
- Action potential enters AV bundle and out over ventricles
- Contraction of ventricles/ ventricular systole
- Repolarization of ventricular fibers
- Ventricular relaxation/ diastole
What appears when cardiac ation potential arises in SA node?
P wave
What appears on the EKG when Action potential enters AV bundle and out over ventricles
QRS complex
Masks atrial repolarization
When does the T-Wave appear on the EKG?
Repolarization of ventricular fibers
What is Cardiac Output?
volume of blood ejected from left (or right) ventricle into aorta (or pulmonary trunk) each minute
What is the equation for Cardiac Output (CO)?
CO = stroke volume (SV) x heart rate (HR)
What is the cardiac reserve?
Difference between maximum CO and CO at rest
Entire blood volume flows through pulmonary and systemic circuits each
Minute
Stoke Volume
amount of blood ejected from a ventricle (left/right) in one beat of the heart
3 factors ensure left and right ventricles pump equal volumes of blood
- Preload
- Contractility
- Afterload
What happens with a greater preload?
increased force of contraction
Preload: Frank-Starling law of the heart
the more the heart fills with blood during diastole, the greater the force of contraction during systole
Preload proportional to EDV
What is EDV? What are the 2 factors that determine EDV?
End-Diastolic Volume
2 Factors:
- Duration of ventricular diastole
- Venous return – volume of blood returning to right ventricle
Preload
Degree of stretch on the heart before it contracts
Contractility
Strength of contraction at any given preload
What do Positive inotropic agents do to Contractility?
–increase contractility
- Often promote Ca2+ inflow during cardiac action potential
- Increases stroke volume
- Epinephrine, norepinephrine, digitalis
What do Negative Inotropic agents do to contractility?
decrease contractility
-Anoxia, acidosis, some anesthetics, and increased K+ in interstitial fluid
Afterload
Pressure that must be overcome before a semilunar valve can open
What can increase in afterload cause?
–causes stroke volume to decrease
•Blood remains in ventricle at the end of systole
What increases afterload?
Hypertension and atherosclerosis
Regulation of Heart Rate
–Cardiac output depends on heart rate and stroke volume
–Adjustments in heart rate important in short-term control of cardiac output and blood pressure
–Autonomic nervous system and epinephrine/ norepinephrine most important
Where does autonomic regulation of the heart rate originate?
Cardiovascular center of medulla oblongata
What does Autonomic Regulation do?
Increases or decreases frequency of nerve impulses in both sympathetic and parasympathetic branches of ANS
What are the 2 seperate effects that Norepinephrin have?
- In SA and AV node speeds rate of spontaneous depolarization
- In contractile fibers enhances Ca2+ entry increasing contractility
What do parasympathetic nerves do and what does this do to the heart rate?
nerves release acetylcholine which decreases heart rate by slowing rate of spontaneous depolarization
Depolarization
Plateau
Repolarization
P-Wave
QRS Complex
T- Wave
