chapter 14: cardiovascular physiology

Taken right from Dr. Cornell's study guide :)

What is a pressure gradient and how does it affect flow?

Pressure gradient is the difference in pressure and it is directly related to flow 

How does distance affect pressure of a fluid in motion?

Inversely proportional

How does resistance affect flow?

Inversely proportional  

How does viscosity affect resistance and flow?

Viscosity is directly related to resistance.

How does the vessel radius affect resistance and flow?

Vasoconstriction is a decrease flow and increase resistance. Vasodilation is increase flow and decrease resistance

What is the difference between flow rate and velocity

The flow rate is the volume of blood that passes a certain point in time. The velocity is the speed the fluid flows past a point in time. 

What is the relationship between flow rate and velocity?

Directly related 

What is the relationship between velocity and the cross-sectional area of the tube?

Inversely proportional 

What is Poiseuille’s Law? Know the big picture concep

The big picture is that resistance is directly related to length and viscosity. That means that length and viscosity are inversely proportional to flow. It also states that the radius is inversely proportional to resistance, which means it is also directly related to flow. The radius has the biggest, easiest impact on resistance and flow. 

What is the difference between the autorhythmic and contractile cells?

Contractile cells shorten to create pressure while autorhythmic cells create their own electrical signal  

How does the contractile cardiac cell contract? 

1. Potential travels down sarcolemma into t-tubule 

2. In T-Tubule: L Type Calcium voltage gate, calcium influx 

3. Binds to RYR, RYR opens: calcium enters sarcoplasm 

4. Calcium induced calcium spark 

5. Calcium binds to troponin  

6. NCX: sodium calcium exchange, sodium is exchanged for calcium, 1 calcium efflux, 3 sodium influx. The NCX is in the sarcolemma. Also, there is a calcium pump in the sarcoplasmic reticulum. 

Know the membrane potential, threshold, when the gates are opened and closed, etc.  

• RMP: -90 mV 

• No threshold  

• No hyperpolarization 

• During depolarization: sodium gates: open, potassium gates closed 

• Max depolarization: 20 mv, sodium gates closed, potassium gates open, repolarization begins 

• Plateau: potassium gates close, calcium voltage gates open 

• After plateau: potassium gates open, calcium closes, and repolarization continues  

What is the plateau and why is there one?

The purpose is to extend the refractory period for the entire muscle twitch to prevent tetanus (sustained contraction) 

Cardiac muscle

Long refractory period to prevent tetany and ensure proper rhythmic contraction and relaxation of the heart. 

 Skeletal Muscle

Short refractory period to allow rapid, sustained, and forceful contractions during voluntary movements. 

Compare the refractory periods

For the Heart: The long refractory period ensures that each heartbeat is distinct, maintaining the pumping rhythm and preventing dangerous arrhythmias.  

For Skeletal Muscles: The short refractory period allows skeletal muscles to perform tasks requiring rapid and forceful contractions 

Know the steps of an action potential in a cardiac autorhythmic cell 

• 1. No RMP (pacemaker potential between -40 mv and -60 mv) 

• 2. I F channel opens (Na influx, Potassium efflux) The I_F channels close right before reach threshold. 

• 3. Threshold (-40 mV), some calcium channels open to bring the -40 mv  

• 4. Depolarization: calcium voltage opens, potassium voltage closes 

• 5. No maximum depolarization 

• 6. During repolarization: potassium gates open, calcium voltage gates close 

• 7. Returns to pacemaker potential  

The conducting system of the heart:

SA Node: main pacemaker: upper right atrium, Internodal fibers: in arterial walls, atrial contract (systole), AV node, bottom right atrium, AV bundle + bundle branches: interventricular septum, Purkinje fibers: in trabeculae carnae and papillary muscles, ventricular contractions (systole) 

P wave:

atrial depolarization, atrial systole

QRS Complex

ventricular depolarization, ventricular systole 

T wave:

ventricular repolarization, leads to ventricular diastole (filling) 

When do the valves open and close?

In late ventricular diastole, the heart is at rest. The AV valves have opened, and blood is filling the ventricles. This is passive filling due to gravity, and it is 80% filling. The last 20% of filling is from atrial systole. In the beginning of ventricular systole, the AV valves close (this is due to ventricular pressure being higher than atrial). This is the first heart sound of the heartbeat. The beginning of ventricular systole is also isovolumic ventricular systole. This is when all heart valves are closed until the ventricles have generated enough pressure to overcome pulmonary and system pressures. The semilunar valves will open during ventricular systole when ventricular pressure is higher than the pressure inside the pulmonary trunk and aorta. After the ventricles have ejected the blood, the semilunar valves will close because now ventricular pressure is lower than pulmonary and systemic blood pressure. This will be the second heart sound during the heartbeat. In early ventricular diastole, all 4 valves are closed. This is isovolumic ventricular relaxation. It is over when the AV valves open. They will open when atrial pressure is higher than ventricular during ventricular diastole. The amount of blood in the ventricle at the end of diastole is called the EDV. The amount of blood left in the ventricle after it fully contracts is called the ESV. 

What is stroke volume?

The volume of blood ejected from 1 heartbeat 

How is stroke volume calculated?

SV=EDV-ESV 

What is cardiac output?

The volume of blood ejected out of a ventricle every minute 

How is cardiac output calculated?

C0=SV times HR 

Parasympathetic:

hyperpolarizes the SA node 

Opens potassium channel and closes calcium channel 

Sympathetic

easier to depolarize 

Opens calcium channels 

Opens sodium channels 

Length-tension relationship?

Directly related 

Frank-Starling Law of the Heart

The EDV is directly related to the stroke volume 

What are inotropic effects?

18. Negative: decreases calcium 

Positive: increases calcium by increasing calcium storage 

how do inotropic effects influence stroke volume

they are directly related. As calcium levels increase, stroke volume increases due to increased muscle tension 

What are the factors that affect venous return to the heart?  

• Breathing mechanism: diaphragm decreases thoracic pressure 

• Vein valves: prevent blood from flowing backward 

• Skeletal muscle contraction 

• sympathetic innervation