The Cardiovascular system Flashcards
Factors affecting resistance
- Blood viscosity (affected by vol. and no. of erythrocytes)
- Total blood vessel length
- Blood vessel diameter (vasoconstricted=more resistance, vasodilated = less resistance)
What type of blood vessel acts as a ‘pressure reservoir’ and are near the heart?
Elastic/conduit arteries- they contain lots of elastin that allow them to expand and recoil as blood is ejected by the heart
What type of artery delivers blood to specific organs?
Muscular arteries- play a huge role in regulation of blood pressure
Define systolic and diastolic blood pressure
Systolic blood pressure - maximal arterial pressure reached during ventricular ejection
Diastolic blood pressure - minimum arterial pressure reached just before ventricular ejection
Is blood pressure higher in the systemic or pulmonary circulation?
Systemic circulation (heart–>body–>heart)
What is the term describing the difference between systolic and diastolic pressure?
Pulse pressure
What is arteriole function controlled by?
neural, hormonal and local chemicals
What is the basal level of contraction of arterioles called?
intrinsic tone
What are the 3 types of capillaries?
- Continuous
- Fenestrated
- Sinusoidal
What are the 3 types of capillaries?
- Continuous (skin, muscle)
- Fenestrated (intestines, kidneys)
- Sinusoidal (liver)
In some tissues and organs, blood enters capillaries through ________.
Metarteriole
In some tissues and organs, blood enters capillaries through ________.
Metarterioles
Major functions of veins
- Act as a low pressure reservoir
- maintain peripheral venous pressure
Major functions of veins
- act as a low pressure conduits returning blood to the heart
- maintain peripheral venous pressure
define atrioventricular septum
the muscular wall separating the left and right ventricles
define pericardium
muscular sac enclosing the heart
define myocardium
muscular wall of the heart
define epicardium
fixes inner layer of pericardium to the heart
name all the valves of the heart
- aortic semi-lunar valve
- pulmonary semi-lunar valve
- atrioventricular valves –> bicuspid and tricuspid
function of the papillary muscles
do not open or close the AV valves but limit movement to prevent backflow
function of the chordae tendinae
fastens AV valves to the papillary muscles
function of the cardiovascular system is impacted by:
- nervous system
- endocrine system
- kidneys
blood is supplied to the heart itself by ______
coronary arteries
features of skeletal muscle
multi-nucleated striated elongated - fibre use the sliding filament mechanism to contract have gap junctions large mitochondria
features of cardiac muscle
single or double nucleated
striated
adjacent cells connected by intercalated disk
features of smooth muscle
single nucleus
spindle-shaped in sheet-like layers
single and multi-unit
node cells have the ability to stimulate their own action potentials, this is called ______
automaticity
1% of cardiac cells do not function in contraction, these cells are ____
the conducting system of the heart and are in electrical contact with the cardiac muscle cells via gap junctions
what the sympathetic nervous system innervate and what neurotransmitter does it release?
the entire heart and node cells
Norepinephrine
what does the parasympathetic nervous system innervate and what neurotransmitter does it release?
node cells
acetylcholine
what type of receptors are those for acetylcholine?
muscarinic type
what type of receptors are those for norepinephrine?
beta-adrenergic
how is contraction conducted in the heart?
sinoatrial node –> atrial muscle cells –> atrioventricular node –> Bundle of His –> left and right bundle branches –> left and right purkinje fibres –> ventricular muscle cells
how is an action potential transmitted?
through gap junctions between myocardial cells
through which pathway does the wave of depolarisation travel to get to the AV node
internodal pathway
why does the purkinje fibres also supply the papillary muscles?
it tell them to contract before the rest of the atria to help prevent backflow through the valves
what does an ECG reading show?
the electrical activity not a single action potential
P wave
result of the depolarization wave from the SA node to the AV node. Atria contract 0.1 seconds after the P wave starts
QRS complex
is a result of ventricular depolarization and precedes ventricular contraction
T wave
caused by ventricular repolarization
define cardiac output
the product of heart rate and stroke volume
CO= HR X SV
units L/min
define stroke volume
the difference between end diastolic volume and end systolic volume
SV = EDV - ESV
what do positive chronotropic factors do?
increase heart rate
what do negative chronotropic factors do?
decrease heart rate
which nervous system increases heart rate?
sympathetic nervous system
What is the Frank-Starling mechanism?
the relationship between stroke volume and end-diastolic volume
The ventricle contracts more
forcefully during systole when it has been filled to a greater degree during diastole (stroke volume increases as end-diastolic volume increases)
what accounts for the Frank-Starling mechanism?
a length-tension relationship because end-diastolic volume is a major determinant of how stretched the ventricular sarcomeres are just before contraction
increase end-diastolic volume, increase ventricular sarcomere stretching, increase contractile force generated, increases stroke volume
what is the significance of the Frank-Starling mechanism?
maintains the equality of left and right cardiac outputs
If venous return is increases, end-diastolic volume increases so stroke volume increases to match the cardiac output of the other ventricle
define ventricular contractility
the strength of a contraction at any given end-diastolic volume
how is ventricular contraction increased?
The sympathetic nervous system is stimulated to increase norepinephrine secretion, which acts on beta-adrenergic receptors to increases ventricular contraction
plasma epinephrine acting on these receptors also increases contractility
what is the effect of increased contractility?
results in greater stroke volume due to a more complete ejection of the end-diastolic volume
what is heart rate dependent on?
- choronotropic factors
- sympathetic nervous system
- parasympathetic nervous system
what is stroke vol. dependent on?
end diastolic volume and end systolic volume
dependent on frank starling mechanism and contractility
what is cardiac output dependent on?
stroke volume and heart rate
what is total peripheral resistance and what is it dependent on?
total resistance to flow in systemic blood vessels from beginning of aorta to ends of venae cavae
vasculature
arterial baroreceptors, eg aortic arch baroreceptor, respond to changes in?
arterial pressure
they are sensory neurons highly sensitive to stretch or distortion
degree of stretch directly proportional to blood pressure
in term of baroreceptors, what happens if arterial pressure increases?
baroreceptor firing increases, this decreases sympathetic outflow to the heart, arterioles and veins and increases parasympathetic outflow to heart
what happens if arterial pressure decreases?
decrease in baroreceptor firing, increase in sympathetic outflow, decreases parasympathetic outflow to the heart
plasma concentration of angiotensin II and vasopressin increases which increases arterial pressure by constricting arterioles
what is the medullary cardiovascular center
a network of connected neurons in the medulla oblongata that act as the primary integrating center for the baroreceptor reflexes
how to adjust arterial pressure long term?
change blood volume
how to calculate mean arterial pressure
diastolic pressure + 1/3 (systolic pressure - diastolic pressure)
how does increased arterial pressure decrease blood vol.?
increases urinary loss of sodium and water, therefore decreases plasma vol.
define hypertension
chronically increased systemic arterial pressure
methods of treating hypertension?
- diuretics
- beta-adrenergic receptor blockers
- calcium channel blockers
- angiotensin-converting enzyme inhibitors
function of diuretics
increase excretion of sodium and
water, decreasing cardiac output with no
change in peripheral resistance
function of beta-adrenergic receptor blockers
reduce cardiac output
function of calcium channel blockers
Reduce entry of
calcium in vascular smooth muscle cells =
weaker contractions (vasodilation) = lowers peripheral
resistance
function of angiotensin-converting enzyme inhibitors
: Final step in formation of
Angiotensin II (a vasoconstrictor) is mediated
by an ACE. Blocking this enzyme causes
vasodilation lowering peripheral resistance
function of aldosterone
slow-acting steroid hormone that stimulates sodium reabsorption by kidney tubules
what controls aldosterone secretion?
angiotensin II
how does the renin-angiotensin system work to respond to changes in NaCl conc
intra-renal baroreceptors detect changes in stretching due to lower blood volume. This stimulates the production of renin which works to split angiotensin I from angiotensinogen. Angiotensin I is converted to angiotensin II which stimulates aldosterone secretion, which stimulates sodium reabsorption by kidney tubules. Therefore increasing plasma volume and blood volume.
where are angiotensin-converting enzymes found?
on endothelial cells
what is the vasopressin?
rapid acting peptide produced by the pituitary gland
which stimulates water reabsorption
what is atrial natriuretic peptide (ANP) and what does it do?
produced by cardiac cells to inhibit sodium reabsorption by kidney tubular cells
acts on renal blood vessels to increases filtration rate causing sodium excretion
inhibits the action of aldosterone
what happens within hours of blood loss?
Compensatory movement of
interstitial fluid into the capillaries
to increase plasma volume
REDISTRIBUTION NOT REPLACEMENT
Other slower effects include:
- an increase in thirst
- a decrease in salt and water excretion
Mediated by hormones and kidney function:
- renin, angiotensin and aldosterone
what happens within days of blood loss?
cells are replaced by erythropoiesis and haematopoiesis
