CVS Flashcards
What are the two circuits of blood flow in body?
- Pulmonary circuit and systemic circuit
What is the pulmonary circuit?
- right ventricle (ejects blood into pulmonary artery)
- goes into lungs (gas exchange), ejects blood into left atrium
What is the syswtemic circuit?
- Starts with the LEFT VENTRICLE–> aorta—> arterioles–> capillaries–> exchange of nutrients and waste–> back to heart by main veins (vena cavae)
First, blood flows through the ____ circuit, then the __ circuit
Pulmonary circuit,m systemic circuit
In what 3 conditions will you have a fast death?
- NO excitation
- NO ventricular contraction
- NO pulse
What are desmosomes?
Structural component of intercollated disks(the glue)
What do gap junctions allow for?
- Spread of excitation of heart thus, NO contraction
Where is the excitation of the heart initiated?
- SA node (sino atrial node)
What is the pathway of excitation of heart?
- SA node–> internodal pathways–> Bundle of Hiss (in ventricular septum)–> apex–> purkinje fibres –> allows muscle to contract
What do the purkinje fibres do ?
- transmit electrical impulses to ALL ventricular muscle cells AT SAME TIME so contract at SAME TIME
Approx how long does it take for depolarisation/excitation of atria?
- approx 0.09 secs for depolarisation
Approx how long does it take for dwepolarisation/excitation of ventricles?
Approx 0.06 seconds
Where is there a significant slowing of rate of conduction?
- getting through the AV node (atrioventricular node)
Roughly how long does it take to pass through the AV node?
- 0.09 secs
How come it takes longer to pass through AV node?
- Fewer gap junctions between AV node cells (thus slower to pass)
Why do we want slow conduction through the AV node?
- So ventricles have ENOUGH time to FILL with blood before getting excited (and contracting) (i.e. ventricular filling needs to occur so pulse slows)
If an SA node (pacemaker cell) is isolated what happens?
- It will generate APs by itself
What are the 3 features of ventricular Aps?
- Have a plateu
- Much more negative (MDP-maximum diastolic potential -90mV)
- STABLE resting mempot
What are the 3 features of SA node APs?
- much more positive MDP -65mV
- No stable resting pacemaker potential
- (no plateu)
What does aan Ena (nerst) of +70mV
If the cell was only permeable to sodium (Na+), it would come to rest at a mempot of +70mV
What source of excitation do ventricular muscle cells require?
- External source (from K+, Ca2+, Na+)
What does TTX inhibit?
- Fast Na+ channels
- Selective inhibitor
What will TTX do to a ventricular Ap?
- NO AP occurs! Heart would stop= death
What will TTX do to pacemaker cells?
-NOTHING! Fast Na+ channels not involved in pacemaker AP