Exam 1 Review Flashcards
What is autorhythmicity?
- Does not require conscious intervention to elicit cardiac muscle to contract
- Sets its own rhythm without need for input from the nervous system
Where is the SA node located?
- In upper atrium
- Slightly inferior and lateral to superior vena cava
Depolarization rate of SA node under normal conditions
- 60+ times per minute
- Fastest intrinsic rate of depolarization
Where is the AV node located
Posterior and medial to tricuspid valve
Depolarization rate of AV node under normal conditions
- ~40 times per minute
- Slower then SA node
Which node is the pacemaker of the heart?
SA node
Parts of an ECG
- P wave
- QRS complex
- T wave
P wave
Depolarization of all cells in atria except SA node
QRS complex
- Ventricular depolarization
- Masks atrial repolarization
Parts of QRS complex
- Q wave
- R wave
- S wave
Q wave
First downward deflection
R wave
Large upward deflection
S wave
Following downward deflection
T wave
- Occurs after S wave of QRS complex
- Ventricular repolarization
R-R Interval
- Duration of generation and spread of action potential through heart
- Can be measured to determine heart rate
P-R Interval
- Time it takes for depolarization generated by SA node to spread through atria to ventricles
- Includes AV node delay
Q-T Interval
Action potentials spread through ventricular cells
S-T Segment
Flat because it is recorded during plateau phase of ventricles
Bradycardia
Heart rate under 60 BPM
Tachycardia
Heart rate over 100 BPM
Sinus tachycardia
Regular, fast rhythm
Phases of cardiac cycle
- Ventricular filling phase
- Isovolumetric contraction phase
- Ventricular ejection phase
- Isovolumetric relaxation phase
Which valves are closed during the ventricular filling phase?
Pulmonary and aortic valves
Which valves are closed during the isovolumetric contraction phase?
All 4 valves
Which valves are closed during the ventricular ejection phase?
AV valves
Which valves are closed during the isovolumetric relaxation phase
All 4 vavles
What produces the heart sounds
When the AV valves close and when the aortic and pulmonary valves close
Heart rate
Number of beats per minute
Stroke volume
Volume of blood pumped in one heartbeat
Cardiac output
Heart rate x stroke volume
End-systolic volume
- ESV
- Amount of blood in ventricle at the end of contraction
- Afterload
End-diastolic volume
- EDV
- Amount of blood in ventricle after is has filled during diastole
- Preload
Resting stroke volume
EDV - ESV
Ejection fraction
- Percentage of blood ejected with each ventricular systole
- SV/EDV
- Normally 50-65%
Factors that influence stroke volume
- Preload
- Heart contractility
- Afterload
Preload
- Length of sarcomeres in ventricular cells before they contract
- Largely determined by EDV
Factors that influence EDV
- Length of diastole
- Venous return
EDV increases when
- Diastole is longer
- Venous return increases
What is blood pressure?
Outward force that blood exerts on walls of blood vessels
Peripheral resistance
Any factor that hinders blood flow through vasculature contributes to overall resistance
Where is resistance greatest?
- Further away from the heart
- Vessels near heart contribute little to overall resistance
What happens to blood pressure as peripheral resistance increases?
BP increases
What happens to resistance when blood vessel radius changes?
- Radius increases –> Resistance decreases
- Radius decreases –> Resistance increases
How does viscosity impact resistance?
More viscosity has more resistance
How does blood vessel length impact resistance?
Longer –> greater resistance
What kind of nervous system stimulation causes vasoconstriction?
Sympathetic nervous system narrows blood vessels
Components of blood
- Plasma
- Buffy coat
- Erythrocytes
Which component forms the majority of blood?
Plasma
Hematocrit
Percentage of blood by volume composed of erythrocytes
What is plasma mostly made of?
90% water
Shape of RBC
Biconcave disc
Function of RBC
Transport of oxygen and carbon dioxide through blood
Where do RBC’s form?
Hematopoietic stem cells (HSC) in red bone marrow
What is the lifespan of erythrocytes?
100-120 days
How long does erythropoiesis take?
5-7 days
What do HSCs differentiate into?
Progenitor cells called erythrocyte colony-forming units (CFUs)
What do erythrocyte CFUs differentiate into?
Proerythroblasts
What causes CFUs to differentiate into proerythroblasts?
When the kidneys secrete the hormone erythropoietin
What do proerythroblasts become?
Erythroblasts
What happens to erythroblasts?
They reject the shrinking nucleus and becomes a reticulocyte
What happens to reticulocyte?
Becomes an erythrocyte
Where do erythrocytes go to be destroyed?
Erythrocytes become trapped in sinusoids of spleen
What happens to erythrocytes in the spleen?
Spleen macrophages digest erythrocytes
Categories of leukocytes
- Granulocytes
- Agranulocytes
Which leukocytes are most common?
Neutrophils
Which leukocyte is least common?
Basophils
Where do platelets come from?
Megakaryocytes
What vitamin is needed for coagulation?
Vitamin K
How do anticoagulants work?
They inhibit coagulation
Anticoagulants
- Antithrombin III
- Heparin sulfate
- Protein C
Antithrombin III
- Protein that binds and inhibits activity of both factor Xa and thrombin
- Prevents activation of new thrombin
Heparin sulfate
Polysaccharide that enhances antithrombin acitivity
Protein C
- Activated by protein S
- Catalyzes reactions that degrade clotting factors Va and VIIIa
What is the vascular spasm?
Begins immediately when a blood vessel is injured and blood leaks into the extracellular fluid
Why does vasoconstriction occur in the vascular spasm
Decreases local blood pressure and blood flow
Steps of hemostasis
Vascular Spasm –> Platelet Plug Formation –> Coagulation –> Clot Retraction –> Thrombolysis
