Exam 2 - Cardiovascular System (pt. 2) Flashcards
What are the characteristics of neurons?
- lipid bilayer membrane is impermeable to ions
- ions must pass through ion channels
- ion channels are sensitive to environment and can change shape
What is the resting membrane potential?
approximately -70 mV
What are voltage-gated ion channels?
ion channels that change structure in response to voltage changes
What are leak channels?
- channels that are generally open but may open and close at random
- no actual event that opens the channel; intrinsic rate of switching between open and closed
How is the Na+ and K+ gradient maintained?
active transport via the Na+/K+ pump
What are the steps of an action potential/
- at rest
- stimulus applied
- voltage rises
- voltage falls
- end of action potential
- return to rest
Which nodes are responsible for maintaining heart beat?
- sinoatrial (SA) node
- atrioventricular (AV) node
What are pacemaker cells?
cells at the SA node that coordinate the heartbeat
Why does the SA node only control atrial excitation and contraction?
the fibrous skeleton prevents the electrical signal from entering the ventricles
What is the role of the AV node?
to serve as the “electrical gateway” into the ventricles and conduct the action potential
What is the role of purkinje fibers?
conduct the action potential to the muscle cells of the ventricle walls
What events occur during contraction?
- cells of SA node trigger action potential
- action potential moves through the two atria, causing atrial systole
- action potential depolarizes cells of the AV node, causing ventricular systole
- action potential is propagated down AV bundle cells and Purkinje cells
- action potential propagated throughout ventricles, causing contraction from the bottom up
What does an ECG measure?
small changes in voltage between the heart and the rest of the body
What are the waves of an ECG and what do they correspond to?
- P wave: atrial depolarization
- QRS complex: ventricular depolarization, atrial repolarization
- T wave: ventricular repolarization
What type of procedure can remedy a lack of SA node activity/
pacemaker insertion
What is systolic pressure?
the blood pressure during ventricular systole
What is diastolic pressure?
the blood pressure during ventricular diastole
Why are arteries thicker than veins?
there is greater pressure in the arteries than in the veins
How is blood flow regulated?
- vasoconstriction
- vasodilation
What is cardiac output?
amount of blood pumped by the left ventricle in one minute
What three variables affect blood pressure?
- cardiac output
- resistance of vessels
- blood volume
What are included in the cardiovascular control centers in the brain?
- cardioacceleratory neurons
- cardioinhibitory neurons
- vasomotor control
What is the sympathetic response?
- occurs when blood pressure is too low
- causes increased heart rate and vasoconstriction
What is the parasympathetic response?
- occurs when blood pressure is too high
- causes decreased heart rate and vasodilation
