CV V Flashcards
How does increasing sarcomere length increase force of contraction (SV)
- Increases Ca sensitivity (decreased diameter reduces distance Ca must diffuse)
- Additional tension on Ca channels, increases Ca entry from ECF and Ca induced Ca release
What is Frank-starling law of heart
Amount of force developed by cardiac muscle of ventricle (indicated by SV) depends on initial stretch of ventricle walls (cause by ventricle filling)
SV increases with increasing EDV
Preload
Degree of myocardial stretch prior to contraction
EDV
What is EDV determined by
Venous return
What does increased venous return increase
Increases venous pressure resulting in increased atrial filling leading to increased ventricle filling
What are 3 factories affecting venous return
- Skeletal muscle pump
- Respiratory pump
- Sympathetic constriction of veins
Skeletal muscle pump
Skeletal muscle activity compresses veins in extremities pushing blood back
Increases venous return
Repiratory pump
During inspiration chest expands, diaphragm moves down creating sub atmospheric pressure in thoracic cavity
Creates sumbatmospheric pressure in vena cava and draws blood
Veins are compressed during inspiration
Sympathetic constriction of veins
Decreases their volume squeezing blood back to heart
After load
End load against which the heart contracts to eject blood
- blood in ventricle must eject enough pressure to push blood in outflow artery farther down circuit
What is afterload determined by
EDV and pressure in outflow artery prior to contraciton
How can afterload be increased
In pathological situations
Increased arterial BP, decreased aortic compliance
How does blood pressure affect afterload
If heart working harder, heart muscle hypertrophies
Loses elasticity, compresses coronary arteries
Reduces volume
What is pressure reservoir of systemic circuit
Aorta and large arteries
How do arterials alter their diameter
Adjustable screws allow variable resistance
Where does the exchange between blood and cells take place
Capillaries
What do arterioles do
Divergence
What do venues do
Converge until reach single vessel
What serves as an expandable volume reservoir
Systemic veins
What is the progressive branching of vessels
Aorta - arteries - arterioles - capillaries - venules - veins - vena cava
What do all vessels contain
Inner layer of thin endothelial cells
What is order of layers of vessels
Lumen - endothelium - elastic tissue - smooth muscle - fibrous tissue
What are endothelial cells important for
Secreting paracrine, regulation of BP, blood vessel growth, absorption of materials
Paracrines
Substances that signal changes in near by cells
What are capillaries composed of
Single thin endothelium
Basal lamina coats outside (extracellular matrix)
What is artery composed of
All 4
More elastic tissue and smooth muscle than vein
What is arterioles composed of
Endothelium, Smooth muscle
What is venule composed of
Endothelium, fibrous tissue
What is vein composed of
All 4
Larger volume
Less elastic tissue and smooth muscle than arteries
Have valves
More expandable
What is vascular smooth muscle topically controlled by
Sympathetic input
Always state of partial contraction
What is vascular smooth muscle influenced by
Neurotransmitters hormones, paracrines
Cause increased Ca so contraction
Arteries
Walls that are both stiff and springy
Micro circulation
Arterioles, capillaries, venules
What is across microcirculation
Met arterioles
What are metarterioles
Precapillary sphincters
Act as capillary bypass vessels
For blood and WBC’s
What are the smallest vessels in the CV system where majority of exchange between blood and interstitial space occur
Capillaries
How are gasses moved in across endothelial cells of capillaries
Passively diffuse
How are small solutes and water transported around endothelial cells of capillaries
They are linked by interendothelial junctions
What are fenestrations
Membrane lined conduits running though endothelial cells to allow transport
What are capillaries surrounded by
Pericytes, prevent substance readily from moving in
Ex) BBB
Continuous capillary
Most common
- thick endothelial cells, basal lamina
- no fenestrations
- only passage of water and small ions through intercellular junctions
Fenestrated capillary
Thin endothelial cells with fenestrations
Where high transport needed
Small molecule passage
Discontinuous (sinusoidal) capillary
No basal membrane
Large open fenestrations
Gaps between endothelial cells
Transport large molecules
Ex) liver, spleen, bone marrow
Transcellular transport
Diffusion or osmosis across endothelial cell membrane
- gases, small lipid molecules, water, glucose
Paracellular
Diffusion through interendothelial junctions, pores or fenestrations
- water, small water soluble and small polar molecules
Transcytosis
Combination of receptor mediated endocytosis, vesicular transport, exocytosis
- macromolecules across endothelial cells
