Cardiac Physiology part 1

What is the overall function of the Cardiovascular System?

• organ system that serves as a transport system of body

• distributes blood which has O2, nutrients, and hormones

What are components of cardiovascular system?

• blood

• blood vessels

• heart(made of cardiac muscle tissue, involuntary contractions, located in thoracic cavity, dual pump)

Define Atria

• upper chambers of the heart; receive blood that is returning to heart

• pump blood into lower chambers

Define ventricles

• lower chambers

• pump blood away from heart

what are the chordae tendieae?

anchor to papillary muscle; support valves and prevent them from prolapsing

What’s the role of right atrium?

receive deoxygenated blood from rest of body

What’s the role of left atrium?

receive oxygenated blood from lungs

What’s the role of right ventricle?

Send blood to lungs to receive O2

What’s the role of left ventricle?

pump blood to rest of body

How to valves work?

open or close due to pressure

describe characteristics of cardiac muscle

• makes of heart

• responsible for hearts contractility(ability to pump)

• cells are branched ad interconnected which allow for communication; connected by intercalated discs and gap junctions and proteins allow for free passage of ions between cardiac cells

What is the role of myocardial cells?

• make up 99% of cardiac muscle

• contractile cells

• contain sarcomeres (allow for pulling actinon)

• generates contractile force for heart to pump blood

• activated by autorhythmic cells

what is the role of autorhythmic cells?

• 1% of cardiac muscle

• pacemaker cells

• generate action potentials automatically without stimulation and activates myocardial cells

The SA node stimulates contractions in which part of the heart?

generates action potentials to activate myocardial cells in atria

The AV node stimulates contractions in which part of the body?

• generates action potentials to stimulate myocardial cells of ventricles

• slight delay after SA

What is the importance of the slight delay between the sequence of activation between SA and AV nodes?

• allows for AV node to wait until bottom chambers are filled with blood from top chambers before the contract

• if top and bottom chambers contract at same time there isn’t enough time for blood to get to right places so delay allows foe efficiency for how blood gets delivered

What is the resting membrane potential in autorhythmic cell? What is the threshold potential value?

• unstable resting membrane potential

• resting value of about -60mV

• threshold: -40mV

What triggers change of membrane potential in autorhythmic cells?

Na+ channels that are open when cell is at rest allow for passive influx of Na+

what occurs once threshold potential is met in autorhythmic cells?

activates voltage gated channels specifically Ca2+ voltage gated channels which allows for rapid influx of Ca2+

what physiological events occur to cause repolarization in autorhythmic cells? What voltage gated channel reopens during repolarization to restart process?

• Ca2+ voltage gated channels close

• triggers K+ voltage gated channels to open which allows for efflux of K+ ions and causes repolarization

• Na+ voltage gated channels open to restart

What is the role of gap junctions in cardiac muscle?

• channels between cardiac cells

• allow for easy passage of ions from cell to cell

• allows passing of action potentials so neighboring cells can be stimulated by action potentials

• how autorhythmic cell activated myocardial cells

What is resting membrane potential in myocardial cells? threshold potential?

• resting: -90mV

• threshold: -70mV

What triggers change in resting membrane potential in myocardial cells?

action potential from autorhythmic cells pass via gap junctions which allows it to reach threshold potential

what occurs once threshold is met in myocardial cells?

• triggers Na+ voltage gated channels to open and results in very rapid influx of Na+

• around -40mV mark, it will trigger opening of Ca2+ voltage gated channel to allow slow influx of Ca2+

What physiological events causes plateau phase in myocardial cells?

• steady influx of Ca2+

• K+ voltage gated channels opening for K+ efflux

• results in stable membrane potential

What is the significance of plateau phase in myocardial cells

allows for myocardial cells to sustain a longer contraction which allows for more efficient pumping of the heart

how does repolarization work in myocardial cells?

• repolarization of gated channels resetting

• ion/pump and leaky channels allow for ions to be reset