Cardio Vascular Flashcards
What cardio vascular system consist of
Heart – the pump
Blood vessels – the distribution/conduction network
Blood – the ‘cargo’; oxygen, nutrients, CO2, waste
Blood remains within the vessels thus, it is called a closed circulatory system; it does not come in direct contact with tissues
Blood vessel
Higher blood pressure. faster delivery of oxygen & nutrients
Responsive to change and directing blood to where it is needed by constriction & dilation of vessels
Double circulation
blood passes through the heart twice on each circuit / circulation around the body
Pulmonary - oxygenation / carbon dioxide removal
Systemic - distribution; gas exchange, nutrients, waste removal
Heart
Blood carried away from heart by arteries
Return by veins via capillaries.
Arterial circulation at higher than venous
Blood pressure decreases further from heart due to friction from blood vessel walls (peripheral resistance)
Arteries
Arteries have muscular walls to maintain / regulate blood flow
Capillary vessels
Capillary vessels also reduce pressure due to peripheral resistance
and due to loss of ‘tissue fluid’ (exchange of gases, nutrients etc)
Vein
carry blood at lowest pressure and have valves to prevent
backflow
Pulmonary circulation
Is at a lower pressure them systemic circulation
Ensure effective gas exchange and notdamage pulmonary capillaries
What can be linked to normal health system function
The structure of the component that comprise the system
What is the key of understanding card vascular system
Understanding the fundamental structure of specific cells
The specialized anatomy
Ability to respond to chemical and physical signal
Pericardium:
fibrous and serous layers
Epicardium
Myocardium
myocytes (plus other cells)
Endocardium
endothelium-like (blood vessel lining)
4 chambers
Atrium x2 (left & right)
Ventricle x2 (left & right); left thicker wall
Valves
Heart parts
Atrioventricular (separate atria/ventricles)
Tricuspid and mitral (bicuspid)
Semilunar (ventricles - blood vessels leaving heart)
Aortic and pulmonary
Aorta, pulmonary artery, vena cava, pulmonary vein
Right side: atrium - vena cava; ventricle - pulmonary artery
Left side: atrium - pulmonary vein; ventricle - aorta
Coronary arteries and veins
Heart muscles consist of wrest
Cardiomyocytes or myocardial fibers
What fibers made from
1 individual cells joined end to end by specialized junctions intercalated discs
These ensure tight interactions and mediate electrical coupling
Fibres often branch to extend the interconnections
Each cell has a single central nucleus and an abundance of mitochondria
Cells show repeating patterns of striation which are ——&——
Actin myosin filament plus several other proteins
How filament facilitates concentration
By along each other
Concentration depends on what
Calcium signaling
Contractions are synchronized via the intercalated discs and junections between them; this ensures that individual cardiomyocytes work together and the cardiac muscle functions as a syncytium
Sarcomere
is the unit of muscle that contracts; many sarcomeres per cell arranged in series
Filament
Thin Composed protein actin
Thick filament composed of protein myosin
Z-lines
demark each sarcomere (thin filaments connect to the Z-line)
M-Line
defines the middle of each sarcomere and also the middle of the thick filament
I band
is a zone around the Z-lines and includes part of two separate sarcomeres. The I band only has thin filaments.
H band
is a zone around the M-line.
A band
is a zone that demarks the length of thick filaments
There are several different regions/structures within the heart comprised of cells that are similar to cardiomyocytes
Sinoatrial and atrioventricular nodes
The bundle of His and Purkinje fibres
Intrinsic waves of excitation (depolarization) spread from the SA node to the AV node and then to myocytes via other parts of the conduction system; the bundle of His and Purkinje fibres
While capable of functioning independently, the SA is innervated (as are most parts of the heart and circulatory system) by autonomic nerves and SA activity can be controlled by autonomic nervous system signals
Nervous system
comprises the central and peripheral nervous systems (CNS and PNS)
PNS divided into
PNS divided into somatic and autonomic nervous systems
Somatic system controls conscious/subconscious actions
Autonomic system controls actions not normally under voluntary or conscious control (i.e. heart)
The autonomic system is anatomically and functionally divided into
sympathetic and parasympathetic components
Sympathetic system
stimulates the heart rate
Stress, exercise, excitement
Norepinephrine (adrenoceptors)
Parasympathetic system
relaxes/slows the heart
PNS dominates autonomic stimulation of heart
Acetylcholine (muscarinic receptors)
Hormones
local chemical mediators also contribute to control of myocyte activity
Cardiac cycle
refers to all events associated with blood flow through the heart
Systole –
contraction of heart muscle
Diastole
relaxation of heart muscle
Ventricular filling
mid-to-late diastole
Heart blood pressure is low as blood enters atria (passively) and flows into ventricles - atrioventricular valves are open, then atrial systole occurs
Ventricular systole (contraction)
Atria relax and rising ventricular pressure results in closing of atrioventricular valves
Ventricular contraction and ejection phase opens the semilunar valves
Heart sounds (‘lub-dup’)
Heart sounds (‘lub-dup’) closing of heart valves
First sound occurs as atrioventricular valves close and signifies beginning of systole (contraction)
Second sound occurs when semilunar valves close at the beginning of ventricular diastole (relaxation)
The action potentials generated by myocytes contracting can be detected and monitored by what
electrocardiogram (ECG)
Action potentials are the result of
movement of ions (Na+, K+, Ca2+) back and forth cross the myocyte cell membrane (sarcolemma)
Excitation-contraction coupling represents what
the process by which an electrical action potential leads to contraction of cardiac muscle cells. This is achieved by converting a chemical signal into mechanical energy via the action of contractile proteins
ECG trace can provide what
details on the function of the heart and thus evidence of heart damage/disease
P wave corresponds to depolarization of SA node
QRS complex corresponds to ventricular depolarization
T wave corresponds to ventricular repolarization
Stroke volume
is defined as the volume of blood discharged from the ventricle with each contraction. An average adult’s stroke volume is relatively constant, at about ~70 mL.
The cardiac output
is defined as the volume discharged from the ventricle per minute. It is calculated by multiplying the stroke volume by the heart rate, in beats per minute.
‘Preload’ and ‘afterload’ are also key determinants
The structure/histology of the arterial, capillary and venous systems reflects their ——-
specialized functions
Dependent on their diameter and histology of their walls
The structure/histology of the arterial, capillary and venous systems reflects their ——-
specialized functions
Dependent on their diameter and histology of their walls
Similarity and differences between veins and arteries Capillaries
1 All have an inner lumen lined with a single layer of endothelial cells
2 Arteries and veins have the same structural 3 layers, but vary in amount and organization, relating to function
3 Capillaries comprise of a single layer of endothelial cells; lack smooth muscle layer, but have pericytes located at intervals along the outer circumference
Endothelial cells
Regulates interactions with blood and movement of molecules into and out of the circulation
3 layer veins and arteries
Tunica intima (endothelium)
Tunica media (smooth muscle, plus elastin)
Tunica adventitia (connective tissue, small blood vessels, nerve fibres)
Internal (intima-media) and external (media- adventitia) elastic lamina
Arteries
Large arteries like the aorta have a thick tunica media comprised of numerous fenestrated layers of elastin interspersed with smooth muscle cells
Elastin helps these vessels to distend / recoil to deal with the high pressure as blood leaves the heart and dampen the pressure wave
Muscular arteries have several layers of smooth muscle arranged spirally, with some elastin within the tunica media
Arterioles have just a one or two layers of smooth muscle and smaller ones have a discontinuous smooth muscle cells
The smaller muscular arteries and arterioles are described as resistance vessels (have highest wall/lumen ratio) and contribute to vascular resistance or tone i.e. control of flow of blood to particular areas / tissues (degree of constriction of smooth muscle within the wall of the vessel)
Vein
Large veins have a thick intima, relatively thin media and a thick adventitia containing elastic fibres and some smooth muscle
Small-medium sized veins have a well-developed adventitia and thin media with 2-3 layers of muscle. Also have valves, particularly in the limbs to prevent backflow of blood due to lower blood pressure in these vessels
Venules have a thin wall with associated pericytes and smooth muscle cells in larger venules
The unidirectional flow in veins is assisted by the presence of valves, but also by being compressed by neighbouring tissues i.e. positioning of the veins adjacent to an artery or within /between skeletal muscle tissues
Veins are flexible and contain most of the total blood volume in the body and have some vascular tone i.e. can constrict – capacitance vessels
Capillaries
Found at the terminal end of arterioles connecting with venules to form a capillary bed that extends through tissues
Small arterioles and their smooth muscle can serve as sphincters to regulate flow into the capillary bed
Tubes of endothelium (single layer of endothelial cells) and often have pericytes (contractile muscle-like cells) distributed around them
Three different histological features relating to the interactions between the endothelial cells and particular tissues
Continuous – cells joined together by tight junctions/interactions (most common type)
Fenestrated – small gaps or pores interrupting the tight interactions between cells (glomerulus, parts of gut, endocrine
Sinusoidal – larger gaps between cells or discontinuities in the vessel (liver, spleen, bone marrow)
These histological features, together with slower blood flow and a large overall surface area helps facilitate movement and exchange of diffusible substances/molecules between the blood and the surrounding tissue environment
Permeability of the capillary wall is selective with respect of what
size and properties of the molecules to be exchanged
What can move across endothelial cell membrane
Gases and small molecules
How larger molecules and water transported
selectively transported via tight junctions, fenestrations or membrane vesicles
What can facilitate movement exchange
Differentials in hydrostatic and colloidal osmotic or oncotic pressures across the capillary bed
Net movement from blood to tissue near the arteriole end
Net movement from tissue to blood at the venule end
Lymphatic vessels/system also help return tissue fluid to the circulation
Arrhythmias
abnormalities in heart rate or rhythm, such as fibrillation of atria or ventricles
Often various causes, but linked to abnormal control of excitation/depolarization
Often linked to cardiac arrest i.e. the heart stops beating
Hypertension
consistently elevated resting blood pressure
Stresses the CVS and can damage blood vessels contributing to other conditions
Myocardial ischaemia/infarction
reduced flow of blood in coronary arteries
Blocking of arteries due to atherosclerosis
Angina and heart attacks – heart damage and potentially cardiac arrest
Heart failure
heart unable to produce/maintain an adequate output to perfuse the organs/tissues
Several mechanisms, which might include some of those mentioned above
Hypertension
Treatments
Lifestyle e.g. diet, smoking etc
Diuretics – thiazides
Reduce blood volume, increase sodium and decrease potassium excretion
Sympathetic nervous regulators – b1 antagonists, a-1 antagonists
Reduce heart rate, stroke volume
Reduce vasoconstriction
Calcium channel blockers
Reduce heart rate, stroke volume
Reduce vasoconstriction, stimulate vasodilation
Vasoactive factors – block vasoconstrictor activity or directly stimulate vasodilation
ACE inhibitors block conversion of angiotensin I to angiotensin II
Angiotenin II receptor antagonists
NO-releasing vasodilators
Treatments for angina and IHD
