Title: Physiology 2130 / Module 8: Circulatory System I

4 Principal Functions of the Cardiovascular System:
1. Transports oxygen and nutrients to all cells of the body.
2. Transports CO2 and waste away from cells.
3. Helps regulate blood pressure and pH.
4. Transports and distribtues hormones and other substances within the body.

Q: The [...] atrium and ventricle pump blood to the lungs.
The [...] atrium and ventricle pump blood to the rest of the body.
A: right; left

Q: The left ventricle has a thicker [...] than the right ventricle because it must contract more forcefully.
A: wall

Q: Valves ensure that fluids (ie. blood) flow in [...] direction.
A: one

Header: Describe the function of the particular structure of the heart

Header: Describe the function of the particular structure of the heart:

Blood Cirulation Through the Heart:
1. Blood enters the heart at the right atrium.
2. Blood flows to the right atrium thru the right AV to right ventricle.
3. Right ventricle contracts which pushes blood through the pulmonary valve, to go through the pulmonary artery to the lungs.
4. Oxygenated blood from the lungs passes through the pulmonary vein to the left atrium.
5. Left atrium takes blood through the left AV valve to the left ventricle.
6. Left ventricle contracts and blood is ejected through the aortic valve into the aorta and out to the body.

Q: The circulation circuits are:
1. [...]; &
2. [...]
A: Pulmonary Circulation; Systemic Circulation

Q: [...] circuit takes blood high in CO2 and low in O2 to oxygenate it and return to the left side of the heart.
A: Pulmonary circulation

Q: The [...] circuit delivers oxygenated blood to all tissues and muscles, returning it to the right side of the heart.
A: systemic circulation

Q: The myocardial cells are:
1. [...]; &
2. [...]
A: Contractile Cells; Nodal (Conducting) Cells

Q: [...] are similar to skeletal muscle cells & form most walls of the atria and ventricles.
A: Contractile cells
Extra: They have a similar structure to the skeletal muscle cells but have more mitochondria and one nucleus

Q: Contractile cells are shorter and branched, and are joined together by [...].
A: intercalated discs

Q: Intercalated Discs contain:
1. [...] which bind cells together.
2. [...] which allow for the movement of ions and ion currents between myocardial cells.
A: Tight Junctions; Gap Junctions

Q: [...] of the heart can conduct action potentials from cell to cell without the need for nerves.
A: Myocardial cells

Q: Nodal cells contract very weakly because they do not contain many [...].
A: myofibrils

Q: Nodal cells display [...] and rapidly conduct action potentials to the [...] and [...] muscle.
A: self-excitability; atrial; ventricular

Q: [...] means the cells can spontaneously generate action potentials without the help of any nervous system input.
A: Self-excitatory

Q: The [...] is the pacemaker of the heart.
A: sinoatrial (SA) node
Extra: Called this because it is the first area to spontaneously depolarize to produce an action potential.

Header: Name the location of the heart (they are in order of how the self-excitability travels):

Q: The [...] are the last in the process of self-excitability and will lead to the AP to the ventricle.
A: Purkinje Fibers

Q: Myocardial cells generate action potentials using ions but they do NOT require [...].
A: stimuli
Extra: These Action Potentials = Pacemaker Potentials

Q: Almost all cardiac cells can generate a pacemaker potential, but the [...] does it the fastest, therefore considered the primary pacemaker of the heart.
A: SA node

The pacemaker potential occurs because of a combination of events:
1. Na+ does enter, the SA nodal cells are more permeable/leakier to Na+ than other cells = depolarization.
2. Less K+ leaves in the SA node cells because of special channels preventing the leaking.
3. Ca++ also leaks into the SA nodal cells (down its conc gradient).

Q: The threshold of SA nodal cells is [...]mV.
A: -40

Q: SA nodal cells do not have a stable 'resting' membrane potential, although cells are typically around [...]mV.
A: -60

Q: In cardiac cells, the depolarization for an SA node action potential is due to [...] entering the cell and repolarization is due to [...] leaving slowly.
A: Ca++; K+

Where SA Action Potentials Travel After Conduction:
1. Spreads from SA node throughout the atrial muscle via the special gap junctions between cells, causes it to contract.
2. Travels through the atrio-ventricular node (AV node).
3. Travels through the Bundle of His quickly which takes it down to the apex of the heart (bottom of ventricles).
4.Then transmitted across the Purkinje fibers which rapidly distributes the AP to the ventricles which causes them to contract (bottom up, pushes blood like squeezing toothpaste out).
Extra: 2. Travelling through the AV node is a necessary pause so ventricles do not contract before atria is still contracting bc then blood wouldn't know where to go.
3. One of the speediest pathways in the heart.

Q: The heart sits in the middle of electrolytic body fluids, so APs can have electric currents spread to the surface of the body. If electrodes are placed on the skin around the heart, electric potentials generated by the heart can be recorded as an [...].
A: electrocardiogram (ECG)

Q: Electric activity in the brain can be recorded as a [...].
A: electroencephalogram (EEG)

Q: Electric activity (or action potentials) in the muscles can also be recorded as [...].
A: electromyograms (EMG)

Q: The timing of contractions (gotten from an ECG) can be used to [...].
A: diagnose various diseases or problems

Q: The waves shown on an ECG are:
1. [...] represents the depolarization of the atrial muscle, leading to their contraction.
2. [...] is produced by the depolarization of the ventriclar muscles prior to its contraction; largest waveform because largest muscle in the heart.
3. [...] is a result of the repolarization of the ventricular muscle as it relaxes.
A: P-Wave; QRS Complex; T-Wave
Extra: Depolarization is just prior to the contraction of that very same muscle.

Q: The repolarization of the [...] is a small event, and would occur at roughly the same time as the QRS complex therefore getting obscured.
A: atria

Q: The cardiac cycle consists of all the [...], [...] and [...] events that occur in the heart.
A: mechanical; valvular; electrical
Extra: Mechanical = pressure and volume changes;
Electrical = ECG activity;
Valvular = valve activity from the beginning of one contraction to the beginning of another.

Q: 2 Primary Phases of the Cardiac Cycle:
1. [...]
2. [...]
A: Systole; Diastole
Extra: Systole = Contraction
Diastole = Relaxation

Q: Blood has a pressure gradient that flows from [...] concentration.
A: high to low

Q: For blood to flow, you must have a [...] and [...].
A: pressure gradient; open valves

Steps of the Cardiac Cycle:
1. Atrial Systole
2. Isovolumetric Ventricular Contraction
3. Ventricular Systole 
4. Early Ventricular Diastole 
5. Late Ventricular Diastole

Q: Most of the blood enters the ventricles when they are in [...], accounts for about 70% of the blood in the cardiac cycle.
A: late ventricular diastole
Extra: This is because the pressure in the atria > ventricle so blood flows passively following the pressure gradient

Q: [...] is the total amount of blood that a single ventricle can pump out in 1 minute.
A: Cardiac output

Q: [...] is the volume of blood pumped by a single ventricle in one contraction.
A: Stroke volume

Q: To alter cardiac output, either [...] or [...] are changed.
A: stroke volume; heart rate

Q: Heart Sounds
1. [...] - semilunar valves closing.
2. [...] - atrioventricular valves closing.
A: DUP; LUB

Q: [...] is the number of time the heart beats in 1 minute.
A: Heart rate

Q: Ways to Change HR:
1. [...];
2. [...].
A: Parasympathetic Nervous System; Sympathetic Nervous System

How Does the PSYN Change HR:
1. Releases ACh onto SA and AV nodes = K+ channels open (and some Ca++ ones close);
2. Membrane will hyperpolarize;
3. Slope of pacemaker potential will decrease = longer to reach threshold therefore heart rate slows.
Extra: The PSYN is continually activated at rest.

Q: PNS also affects the AV node because it must slow APs down the AV node to ensure the [...] have finished contracting before the [...] contract.
A: atria; ventricles

Q: The PSYN is continously activated at rest to maintain a bpm of 70, this is called [...].
A: vagal tone
Extra: Because vagus nerve transmits signals for PSYN to the heart.

Q: The intrinsic speed of  the heart is [...]bpm.
A: 100

How Does the SYN Increase HR?
1. Releases norepinephrine (and adrenaline aka epinephrine) on SA node = opening of more Ca++ and Na+ channels.
2. Causes more rapid depolarization.
3. Pacemaker potential will reach threshold quicker = faster HR.

Q: More Ca++ = stronger contraction = high [...] (and vice versa); the SYN is more active.
A: stroke volume
Extra: Less Ca++ = weaker contraction = lower stroke volume and PSYN more active.

Q: [...] = amount of blood in the ventricle at the end of diastole
A: End Diastolic Volume
Extra: Blood in ventricle just before it contracts; usually 120ml when at rest.

Q: [...] = amount of blood in ventricle at end of systole
A: End Systolic Volume
Extra: The blood left in ventricle right after it contracts is usually 50mL

Q: Stroke Volume = EDV - ESV. This is the amount of blood [...].
A: ejected

Q: 3 Things Can Alter SV:
1. Input from the [...]
2. [...] and Preload
3. [...]
A: autonomic nervous system; EDV; ESV

Q: [...] is the "load" on the heart just before it contracts.
A: Preload
Extra: The higher the EDV the larger the load.

Q: [...] load = [...] of ventricles = opening of more special [...] channels = stronger contraction and more blood pumped out.
A: Greater; stretching; Ca++
Extra: Frank-Starling Law of the heart, the greater the load = greater EDV = more blood pumped out = greater ESV.

Q: The [...] of the heart states that and increase in EDV will increase ESV, and vice versa.
A: Frank Starling Law

How to Change EDV (get more blood back to the heart):
1. Activate SYN which increases venous return since it innervates the smooth muscle located in the walls of veins.
2. Increase contraction and relaxation of skeletal muscles = muscle pump to pump blood back to the heart.
3. Taking deep breaths - lowers pressure in chest cavity and increases venous return to the heart = respiratory pump.
Extra: Essentially, the veins must constrict to "squeeze" blood back to the heart.