Circulation of Blood Flashcards
Identify the main functions of the cardiovascular system.
1) Bulk flow of materials (e.g. gases, nutrients, hormones, waste)
2) Temperature regulation (e.g. pushing blood flow to skin to cool off)
3) Homeostasis
4) Host defense
5) Reproduction
Identify the main ways to regulate the CVS.
The CNS controls both autonomic nerves (fine control over individual organs/tissues) and hormone secretion (widespread effects on CNS) which in turn affect the heart itself, blood vessels, and the volume of blood. Variations in the latter three yield changes in blood pressure.
What other systems is the CVS integrated with ? By whom/what ?
The CNS integrates overall activity of CVS with the activity and functions of the respiratory and renal systems.
Is the heart equally muscular everywhere ?
No, wall of left ventricle more muscular than right
Identify and define the main components of micro-circulation.
Arterioles
– Smallest diameter muscular walled arteries
Precapillary sphincters
-Rings of smooth muscle which control entry of blood from arteriole into each capillary
Capillaries
– Smallest diameter blood vessel: simple tube, one cell thick, of flattened endothelial cells
– Allows for diffusion of nutrients, waste etc in/out tissues
Venules
Smallest diameter vessels which drain blood back to the larger true veins
Describe what is meant by the parallel arrangement of blood.
“Blood vessels branch extensively to form parallel circuits”.
This allows to avoid some organs, hence allowing independent regulation of blood flow by individual tissues (so can adapt to the metabolic demands of the tissues)
Is the majority of the blood in the body present in the pulmonary or systemic circulation ?
The majority of the blood is present in the systemic circulation.
Describe the full normal path of blood flow, starting at the aorta.
Aorta –> Arteries –> Arterioles –> Capillaries –> Venules –> Veins –> Vena Cavae –> Right Atrium –> Right ventricle –> Pulmonary Trunk –> Pulmonary Arteries –> Lung Capillaries –> Pulmonary veins –> Left Atrium –> Left Ventricle –> Aorta
At rest, what is the volume of blood at any on point in the CVS system ?
~5L/min
Explain why blood flows at different speeds a the aorta versus at the capillaries.
At capillaries, slows blood down compared to speed at aorta (allows exchange to occur)
List the main features in which different blood vessels differ, and the main features in which different vessels are similar.
Blood vessels vary – In number – In diameter – In wall thickness – In smooth muscle – In elastic tissue – In fibrous tissue
Blood vessels are all lined by endothelial cells
Which part of the CVS do we alter to control BP ? Which property of this element allows it to control BP ?
Small arteries and arterioles.
Contain a lot of smooth muscles, which allows the body to constrict them to restrict where blood flow goes and BP.
Distinguish the aorta from the vena cavae in terms of compliance.
Vena cava more likely to be compliant (increase in volume with little change in pressiure within in)
Aorta has low compliance, stiffer (will not in increase much in volume with little change
in pressure within it)
What is the ultimate function of the cardiovascular system ?
To ensure adequate blood flow through the capillaries of various organs
How many capillaries are there in the body ? What is the volume they can hold ?
10 billion capillaries
5 liters
True or false: Almost all cells are within a few cell diameters of a capillary.
True
Identify the normal resting distribution of total cardiac output.
Brain: 650 mL (13%) Heart: 215 mL (4%) Skeletal Muscle: 1030 mL (20%) Skin: 430 mL (9%) Kidneys: 950 mL (20%) Abdominal organs: 1200 mL (24%) Other: 525 mL (10%) Total: 5000 mL
What is the opening mechanism of valves ?
Passive process, pressure on one side exceeds that of the other side.
What is it that prevents valves from inverting ?
Papillary muscles
Distinguish the passive process of valve opening from active competence.
Active competence prevents the valves inverting (thanks to papillary muscles) whereas when they normally open it is through a passive process.
Identify the main atrioventricular (cuspid) valves and state their location.
- Tricuspid valve between right atrium and right ventricle
- Bicuspid (mitral) valve between left atrium and left ventricle
What is the role of the chordae tendinae ?
Since the valves are flimsy, they help “hold the atrioventricular valves in place”
Identify the main semiluminar valves and state their location.
- Aortic valve between left ventricle and aorta
- Pulmonary valve between right ventricle and pulmonary trunk
How many cusps does each semiluminar valve have ?
Three (both are tricuspid)
Which of semiluminar or atrioventricular valves are more “heavy duty” ? Why/how ?
Semiluminar valves.
Smaller openings, higher pressure hence more stress and physical abrasion
Describe the main special features of cardiac muscle (and state whether each is similar or different to its equivalent in skeletal muscle).
-Cardiac muscle cells branch, and are connected together by desmosomes (strong, cell-to-cell adhesion molecules forming junctional complexes ) at the junction between cells (intercalated disks). DIFFERENT FROM SKELETAL
-Intercalated disks also contain gap junctions that directly connect the cytoplasm and permit the easy transfer of ions between cells allowing APs to spread. (= Functional syncytium, works as a network)
DIFFERENT FROM SKELETAL
-Striated (Similar to skeletal muscle, thick and thin filaments of myosin and actin but they are smaller fibers with individual nucleus rather than the long tubes in skeletal muscle)
SOMEHOW SIMILAR TO SKELETAL
-“Pacemaker” activity (SAN is the intrinsic pacemaker but other areas have pacemaking ability)
Describe what is meant by functional syncytium.
– Cells of atrial myocardium are all electrically connected
– Ventricles are similar but are a separate functional unit
– Depolarize and contract synchronously
Do all cardiac muscle cells contract ? If so, explain. If not, explain.
No, ~ 1% of cardiac fibers don’t contract, but form the excitatory and conductive muscle fibers.
Describe how the autonomic NS can innervate SAN depolarization.
– Sympathetic nerves increase the rate of SAN depolarization
– Parasympathetic nerves decrease the rate of SAN depolarization
