4 - Laws Flashcards
Blood supply to the LV is directly dependent on the difference between the aortic diastolic pressure and LV end-diastolic pressure (coronary perfusion pressure) and inversely related to the vascular resistance to flow, which varies to the fourth power of the vessel radius.
Poiseuille law
Resting coronary blood flow in the adult is?
250 mL/min (1mL/min/g; 5% of normal cardiac output)
Primary regulator of coronary blood flow is the?
Coronary vascular resistance
Coronary blood flow to perfusion pressure
Are the primary physiologic determinants of coronary vascular tone and myocardial perfusion.
Metabolic factors
The heart normally extracts between _ -_% of arterial oxygen content.
75% to 80%
Primary determinant of myocardial oxygen consumption.
Heart rate
True or false?
Cardiac oxygen extraction is near maximal under resting conditions and cannot substantially increase during exercise.
True
Most important determinant of coronary blood flow
Myocardial oxygen consumption
True or false?
Coronary vascular resistance is greater in the resting, perfumed heart than in the contracting heart.
True
Is the external membrane of the cardiac muscle cell which contains ions, ion channels, pumps and exchangers and transport enzymes.
Sarcolemma
Deep invaginations of the sarcolemma penetrate the internal structure of the myocyte at regular intervals. It assures rapid, simultaneous transmission of depolarizing impulses that initiate myocyte contraction.
Transverse (T) tubules
Is the fundamental contractile unit of the cardiac muscle.
Sarcomere
This area is the area of overlap of thick and thin fibers. This band lengthens as the sarcomere shortens.
A band
This area represents the region of the sarcomere that contains the thin filaments alone and this band is reduced in width as the cell contracts.
I band
Each I band is bisected by what line which delineates the border between 2 adjacent sarcomeres.
Z band
Is at the center of the A band which is composed of thick filaments.
M band
These structure is packed with ryanodine receptors that function as the primary Ca release channel for the SR.
Cisternae
Components of the major contractile apparatus of the muscle (6).
- Actin
- Myosin
- Tropomyosin
- 3 tropomins
Contains 2 interwoven chain helices with two globular heads that bind to actin and two additional pairs of light chains.
Myosin
Functions as the main structural support of the myosin.
Tail (light meromyosin)
The light chain of the myosin complex serve 2 roles.
- Regulatory
2. Essential
A long elastic protein that attaches myosin to the Z lines. It is thought to be a length sensor that establishes progressively greater passive restoring forces as sarcomere length approaches its maximum or minimum.
Titin
Two types of actin
- G
2. F
Is a major component of the thin filament. It functions as the activator of myosin ATPase through its reversible binding with myosin.
Actin
Is one of the two major inhibitors of actin-myosin interaction. It serves to stiffen the thin filament through its position within the longitudinal cleft between intertwined F-actin polymers. Its primary action is its Ca-dependent interaction with troponin complex proteins.
Tropomyosin
Different troponins (3)
Troponin C, I, T