Circulation Flashcards
Functions of the cardiovascular system
allows the bulk flow of materials:
- gases
- nutrients
- hormones
- waste
Temp regulation
homeostasis
host defence
reproduction
how is the CVS regulated
Autonomic nerves and Hormones
what is the function of the parallel arrangement of vessels
– Allows independent regulation of blood flow to different organs
- adapts to metabolic demands of the tissues
aspects of the microcirculation
– Arterioles, precapillary sphincters, capillaries, venules
how much blood passes through your circulation every minute
5 litres
normal passage of blood
VC RA RV Pulmonary Trunk Pulmonary Arteries Lung capillaires Pulmonary veins LA LV Aorta Arteries Arterioles Capillaries Venules Veins
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
% of blood flow to brain
13%
% of blood flow to heart
4%
% of blood flow to skeletal muscle
20%
% of blood Flow to skin
9%
% of blood flow to kidneys
20%
% of blood flow to abdominal organs
24%
Atrioventricular (cuspid) valves
– Fairly ‘flimsy’
– Attached to chordae
tendineae and papillary muscles which stop eversion of the valves during systole
Semiluminar valves
tricuspid
– More ‘heavy duty’
– Smaller openings, higher pressure more stress and physical abrasion
cardiac muscle cells
branch, and are connected together by desmosomes at the junction between cells (intercalated disks)
intercalated disks
contain gap junctions that directly connect the cytoplasm and permit the easy transfer of ions between cells
cardiac muscle features
Striated
– Similar to skeletal muscle
– Thick and thin filaments of myosin and actin
– Smaller fibers with individual nucleus
Connected via intercalated discs
– “Branching” of individual cells connected into a network
Electrical connection through gap junctions
– Allow passage of ions permitting action potentials to spread
– Functional syncitium
Desmosomes
– Strong, cell-to-cell adhesion molecules – Junctional complexes
Conduction in cardiac muscle
Functional syncitium
– Cells of atrial myocardium are all electrically connected – Depolarise and contract synchronously
– Ventricles are similar but are a separate functional unit
“Pacemaker” activity
– Sinoatrial node (SAN) is the intrinsic pacemaker – Other areas have pacemaker ability
Autonomic innervation
– Sympathetic nerves increase the rate of SAN depolarisation
– Parasympathetic nerves decrease the rate of SAN depolarisation
