lecture 5: circulatory system Flashcards
what is the circulatory system
cardiovascular and lymphatic system
what does cardiovascular system consist of
heart
blood vessels
blood
describe how heart is drawn (left and rights)
opposite as hands
so anatomical left and right
right - left
what is function of heart
pumps blood through blood vessels to all parts of body
deliver O2 and nutrients to cells and tissues
remove CO2 and other waste products from cells and tissues
where is heart located in body
more in center
skewed to left - apex (point of heart) toward left hip (heart beat strongest at apex)
between/behind lungs ish
what is the heart wall composed of
mostly muscle
what is the myocardium
layer of cardiac muscle forming the heart wall
why is myocardium of left ventricle so much thicker than other that of right ventricle
left ventricle pumps blood to whole body
needs lots of force to pump blood
right ventricle only pumps to lungs
is deoxygenated blood actually blue
heck no
typically darker red
Identify all structures on heart diagram (anterior, posterior and frontal)
see answers in handwritten notes
name main veins (greater vessels of heart)
superior vena cava
inferior vena cava
pulmonary veins (4)
what are the function of veins and arteries
veins = carry blood towards heart
arteries = carry blood away from heart
name main arteries (greater vessels of heart)
pulmonary trunk
aorta
describe superior vena cava
upper body —> right atrium
describe inferior vena cava
lower body —> right atrium
describe pulmonary veins (4)
lungs —> left atrium
describe pulmonary trunk
right ventricle —> lungs
branches into 2 pulmonary arteries
describe aorta
left ventricle —> body
name the all valves
right atrioventricular valve (tricuspid valve)
left atrioventricular valve (bicuspid (mitral) valve)
pulmonary semilunar valve
aortic semilunar valve
describe AV valves
separate atria and ventricles
prevents blood from flowing into atria from ventricles
unidirectional pumping of blood
when do AV valves close and open
close when ventricles contract
open when ventricles relax
describe semilunar valves
prevent blood flow from arteries to ventricles
when do semilunar valves close and open
close when ventricles relax
open when ventricles contract
what is the function of chordae tendineae
heart stringed
anchor AV valves
stop them from flapping around - helps them
work
what is sound of heart beat
lub dup - sound of valves shutting
lup = contract, AV valves snap shut
dup = semilunar valves closing
describe the two individual pumps the heart acts as
pulmonary circuit pump (with lungs)
systemic circuit pump (with body)
both pump at same time every heartbeat
describe congestive heart failure (generally)
accumulation of fluids - fluid component of blood (mostly water) - builds up
describe right heart failure
peripheral congestion
fluid accumulation in body tissues (more in feet, ankles and fingers)
build up in systemic circuit
describe left heart failure
pulmonary congestion
fluid accumulates in lungs
build up in pulmonary circuit
what is the cardiac cycle
1 complete heartbeat
systole - heart contraction
diastole - heart relaxation
~75beats/min
0.8s/cycle
what part of heat does contraction and relaxation refer to
contraction and relaxation of ventricles since they do most of the pumping work
name steps of cardiac cycle + seconds
1 - atrial diastole / ventricular diastole (0.4s)
2 - atrial systole / ventricular diastole (0.1s)
3 - ventricular systole / atrial diastole (0.3s)
describe step 1 of cardiac cycle
heart is relaxed
blood is flowing into atria and ventricles
describe step 2 of cardiac cycle
atria contract to empty remaining blood into ventricles
describe step 3 of cardiac cycle
ventricles contract
AV valves close and semilunar open
blood flows from ventricles into aorta and pulmonary trunk
what controls each heartbeat
specialized cardiac muscle cells - part of intrinsic conduction system
cells are self excitable - can contract without signals from nervous system
what is intrinsic cardiac conduction system
cells of cardiac conduction system have different intrinsic rates of contraction
which part of heart has highest rate of depolarization
sinoatrial (SA) node
sets pace for whole heart (pacemaker)
name the rates of contraction for parts of heart (4)
SA node = 60-100 bpm
atria = 60-80bpm
AV node = 40-60bpm
ventricles = 20-40 bpm
do electrical impulses spread quickly through heart (explain)
yes they do
cardiac muscle cells are electrically coupled by intercalated disks between cells
what is cardiac cycle regulated by
electrical impulses that radiate through the heart
name the steps of the way the cardiac cycle is regulated (how impulses travel)
SA node
AV node
bundle branches
purkinje fibers
describe what SA node does (impulse that regulates cardiac cycle)
sends out electrical impulse to atria and AV node
atria contract in unison
describe what AV node does (impulse that regulates cardiac cycle)
delays signal (~0.1s) before relaying impulse to AV bundle, bundle branches and purkinje fibers
allows atria to fully empty before ventricles contract
describe what bundle branches do (impulse that regulates cardiac cycle)
conduct impulse to apex of heart
describe what purkinje fibers do (impulse that regulates cardiac cycle)
conduct impulse throughout the ventricular walls
ventricles contract beginning at heart apex (“wringing action”)
what are artificial pacemakers and why would someone need one
sends electrical impulse to heart muscle
used if intrinsic cardiac conduction system isn’t working properly
name factors that affect heart rates
two sets of nerves act on SA node
hormones
body temp
exercise
explain how two sets of nerves act on SA node affects heart rate
increase or decrease heart rate
sympathetic nerves - increase HR (fight or flight response)
parasympathetic nerves - decrease HR (rest and digest)
explain how hormones affect heart rate
epinephrine (released from adrenal glands) increase HR
thyroid hormone increases HR
explain how body temperature affects heart rate
increase in body temp = increase HR
decrease body temp = decrease HR
explain how exercise affects heart rate
HR increases in response to exercise (increased metabolic need of body)
what is an ECG (EKG)
electrical impulses generated during cardiac cycle produce electrical currents that are conducted through body fluids to skin
currents can be detected by electrodes - records as ECG
what must occur for contraction
depolarization of muscle cells cause contraction
cells must repolarize before they can be depolarized again
what are the 3 things to recognize on an ECG
p wave
qrs complex
t wave
what is p wave
depolarization of SA node and atria
what is qrs complex
ventricular depolarization
what is t wave
ventricular repolarization
where is atrial repolarization on ecg
masked by qrs complex
where does AV node fire on ECG
between p wave and qrs complex
what is fibrillation
lack of adequate blood supply causes my myocardial infarction - may cause fibrillation
uncontrolled shuddering of heart, makes it useless as pump
defibrillators - stop fibrillation by delivering electric shock that resets heart
name the 3 types of blood vessels
arteries
veins
capillaries
describe arteries (blood vessels)
carries blood away from heart (towards capillaries)
branch into arterioles
describe veins (blood vessels)
carry blood towards heart (away from capillaries m)
venules converge into veins
describe capillaries (blood vessels)
site of exchange (from blood to tissue, tissue to blood)
upstream end branches from arterioles
downstream ends converges into venules
what is difference between appearance of veins and arteries
artery = circular oval shaped, thick walled
vein = larger lumen, triangular, not circular, irregular
name 3 layers of blood vessel structures
tunica intima (inner)
tunica media (middle)
tunica externa (outer)
describe inner layer of blood vessel structure
endothelium - simple squamous tissue
subdendothelial layer
internal elastic membrane
minimizes resistance to blood flow
describe middle layer of blood vessel structure
smooth muscles and elastic fibers
for strength, movement and elasticity
external elastic membrane
describe outer layer of blood vessel structure
connective tissue made largely of collagen fibers
for support and protection
vasa vasorum
describe layers of capillaries
ONLY HAVE ONE
inner layer of blood vessel structure
arteries vs veins - lumen
larger in veins
low peripheral resistance
arteries vs veins - middle layer (media)
larger in arteries
to withstand high pressure
arteries vs veins - outside layer (externa)
larger in veins
provides support
arteries vs veins - elastic lamina (internal/external)
only present in arteries
to withstand high pressure
arteries vs veins - valves
only present in veins
facilitates return of blood to heat (prevents backflow)
blood pressure decreases…
as blood travels away from heart ventricles
describe how skeletal muscle works for blood (what’s it do) and how it works with venous valves
contraction provides milking action to push blood back to heart - generates force
valves close to ensure blood only moves in one direction towards heart
where is blood flow the slowest
through capillaries
enhances exchange
velocity decreases but area of vascular bed increases
what is blood pressure
hydrostatic force that blood exerts on vessel walls
pressure gradient provides driving force - keeps blood moving
high pressure to low pressure
how to measure blood pressure
measuring arterial blood pressure
high/low
high = systolic pressure (ventricles contacted)
low = diastolic pressure (ventricles relaxed)
normal in young healthy person = 120/70mmHg
describe blood pressure (what is specific range…)
too high - could cause stroke (blood vessel damage)
too low - lose consciousness (inadequate tissue perfusion)
what is blood pressure measured by
sphygmomanometer
describe step 1 of measuring blood pressure
aortic pressure is measured indirectly in brachial artery
how many steps of measuring blood pressure
4
describe step 2 of measuring blood pressure
cuff wrapped around arm
inflated toll cuff exceeds systolic blood pressure
blood flow into arm stops (brachial pulse cannot be heard or felt)
describe step 3 of measuring blood pressure
pressure in cuff is gradually reduced
examiner listens for sounds in brachial artery with stethoscope
point at which blood spurts through constricted artery = systolic pressure
describe step 4 of measuring blood pressure
pressure more reduced
lower the sounds get
pressure at which sounds disappear = diastolic pressure
how can heart rate be measured
heart rate can be measured indirectly by measuring pulse
name factors affecting blood pressure
peripheral resistance
cardiac output
blood volume
vessel elasticity
describe peripheral resistance (factors affecting blood pressure)
determined mostly by arterioles
resistance to flow in systemic circulation (friction within vessel walls)
describe diameter of arterioles
determined by vasoconstriction/vasodilation of arterioles
controlled by action of nerve impulses, hormones and other chemicals on smooth muscle surrounding vessels
how does stress affect arterioles and blood pressure
vasoconstriction so blood pressure increases
describe cardiac output (factors affecting blood pressure)
stroke volume x HR
increased cardiac output = increases pressure
describe blood volume (factors affecting blood pressure)
increased blood volume = increased pressure
describe vessel elasticity (factors affecting blood pressure)
less elasticity = higher pressure
ex: arteriosclerosis
define cardiac output
amount of blood pumped by heart in a single minute
what does cardiac output depend on
stroke volume - volume of blood pumped out by ventricles during each contraction (~70mL)
heart rate - beats/min
describe regulating blood pressure during exercise
cardiac output - increases blood pressure
peripheral resistance - arterioles dilate, so blood pressure decreases
ensures muscles have enough blood flow and blood pressure is maintain
exercise without passing out or having stroke
cardiac output must =
venous return
if blood pressure in veins is low compared to arteries - resistance of arterioles and capillaries dissipates the pressure generated by pumping heart (to maintain this relationship)
name factors that increase venous return
skeletal muscle pump
respiratory pump
lumen of veins are wider than arteries
rhythmic contractions of smooth muscles in the walls of veins and venues account for some movement of blood
describe skeletal muscle pump (increase venous return)
skeletal muscles and valves provide milking action to keep blood moving towards heart
describe respiratory pump (increase venous return)
inhaling decreases pressure in right atrium
vena cava and other large veins near heart allow them to expand and fill with blood (caused by a drop in intra thoracic pressure)
describe how lumen of veins (wider than arteries) affect venous return
less resistance to flow
describe capillaries
only 5-10% of body’s capillaries have blood flowing through them
brain, heart, liver and kidney capillaries usually filled to capacity
what controls flow of blood through capillary beds
constriction of arterioles and precapillary sphincters (rings of smooth muscle)
what does blood flow look like right after meal
activates digestive tract so some increase but looks similar to blood flow at rest
how to molecules cross capillaries (3 steps)
1 - vesicles form by endocytosis on one side and release their contents by exocytosis on other side
2 - diffusion through membrane
3 - bulk flow through clefts between endothelial cells (due to fluid pressure)
*simple squamous - optimized for exchange
under normal circumstances what cannot cross capillary wall
blood cells and most proteins
so they stay within capillary wall
amount of direction of fluid flow across capillaries depends on
hydrostatic pressure - fluid pressing against wall (due to blood pressure), pushing out
osmotic pressure - non diffusible plasma proteins pull water into capillary, sucking in
describe fluid flow across capillaries
higher to lower concentration
pushing out and sucking in
how much fluid is reabsorbed during fluid flow across capillaries (where and why)
at venous end - 85% of fluid is reabsorbed
the other 15% is returned to blood via lymphatic system
describe lymphatic system
lymph flows through a network of lymphatic vessels and composition is similar to ISF
drains into cardiovascular system via subclavian veins
what is returned to blood via lymphatic system
fluids and some proteins that leak from capillaries into ISF
how does fluid enter lymphatic system
by diffusing info lymphatic capillaries that are intermingles among cardiovascular capillaries
vessels have valves - prevent backflow
movement of skeletal muscles - push fluid towards heart
what are lymph nodes
bean shaped organs located at intervals along the lymphatic system
what is blood composed of
plasma
formed elements (erythrocytes, leukocytes and platelets)
give percentages of blood composition
55% - plasma
~45% - erythrocytes
<1% - leucocytes and platelets
what is function of plasma
carries blood cells, cell fragments, nutrients, metabolic wastes, respiratory gases and hormones around body
describe composition of plasma
~90% water
ions (electrolytes)
plasma proteins
describe ions (electrolytes) functions in composition of plasma
osmotic balance
functioning of muscles and nervous system
pH buffering
describe plasma protein functions in composition of plasma
osmotic balance
pH buffering
viscosity of blood
transport of water insoluble lipids
immunity (antibodies)
blood clotting (ex fibrinogen)
what is plasma without clotting factors
serum
describe function of erythrocytes (rbcs)
5-6 million cells/mm^3
transports oxygen
describe structure (and function of that structure) of erythrocytes
biconcave disc (more surface area)
no nuclei (more room for hemoglobin)
no mitochondria (make ATP by anaerobic metabolism)
contains ~250 mil molecules of hemoglobin
describe hemoglobin (made of)
each hemoglobin protein is made of 4 polypeptides - can bind molecules O2
two alpha and two beta polypeptide chains
iron atoms form part of heme group that binds O2 (4 heme groups - 4 O2 molecules)
what does hemoglobin bind
nitric oxide (NO)
NO causes vasodilation which relaxes capillary walls to help delivery of O2 into cells
describe function of leukocytes (wbcs)
effectors of immune system - fight pathogens
spend most of time patrolling interstitial fluid and lymphatic system
name types of leukocytes
neutrophils
lymphocytes
monocytes
eosinophils
basophils
describe neutrophils and monocytes
phagocytes that engulf and digest bacteria and debris
describe lymphocytes
develop into specialized B and T cells
describe basophils and eosinophils
involved in allergic response
which types of wbcs are granulocytes
neutrophils
eosinophils
basophils
which types of wbcs are agranulocytes
lymphocytes and monocytes
describe platelets (cell fragments)
function = blood clotting
initiated when the endothelium of vessel is damaged and connective tissue in wall is exposed to blood
describe steps of clotting
1 - platelets adhere to collagen fibers and release a substance to make platelets sticky
2 - sticky platelets form a plug
3 - fibrin forms a mesh (clot) that traps rbcs and platelets to form clot
*enzymatic cascade
name 2 clotting disorders
hemophilia
spontaneous clotting
describe hemophilia
inherited defect in any step of clotting process
causes excessive bleeding from minor cuts or bruises
describe spontaneous clotting
usually prevented by anticlotting factors in blood
platelets clump with fibrin within a blood vessel forming a thrombus (blood clot)
traveling blood clot is called embolus
thrombus or embolus can block flow of blood and cause heart attack or stroke
where are blood cells produced
in bone marrow
how often do blood cells need to be replaced
constantly - they wear out
ex: erythrocytes usually circulate for only 3-4 months then destroyed by phagocytic cells in liver and spleen
all cells develop from what
a single population of pluripotent stem cells in red marrow of bones (ribs, vertebrae, breastbone, pelvis)
define pluripotent
have potential to become any type of blood cell
what is leukemia
type of blood cancer involving elevated production of abnormal wbcs
uncontrolled cell division at expense of surrounding cells
treatment of leukemia
destroy patients bone marrow and replace with healthy bone marrow
replaced cancerous pluripotent cells with non cancerous ones
what is arteriosclerosis
thickening and hardening of an artery wall
describe atherosclerosis
type of arteriosclerosis
name 2 risk factors for atherosclerosis
hypertsion
ldl/hdl ratio
describe hypertension (risk factors for atherosclerosis)
high blood pressure
causes chronic damage to endothelium that lines arteries (damages plaque formation)
describe ldl/hdl ratio (risk factors for atherosclerosis)
low density lipoprotein - associated with depositing cholesterol in arterial plaques
high density lipoprotein - associated with removing cholesterol from blood
what is a heart attack
myocardial infarction
death of cardiac muscle tissue causes by prolonged blockage of one or more coronary arteries
what is a stroke
death of nervous tissue in brain caused by blockage of an artery of leaking/burst blood vessel in brain
what happens in both heart attack and stroke
tissue dies due to lack of oxygen
any tissue downstream blockage may die
what is angina pectoris
coronary artery is partially blocked - person may feel occasional chest pains
sign that part of heart isn’t getting enough blood (ex narrowing of arteries due to atherosclerosis)
what are intercalated disks
contain gap junctions (connect cytoplasm of 2 cells) (electrically connect myocytes)
also have desmosomes (keeps myocytes from pulling apart)
what is pulse
rhythmic stretching of arteries caused by contraction of ventricles
what does peripheral resistance in arterioles do
impedes blood form editing the arteries
causes arteries to stretch (systolic pressure)
what does peripheral resistance depend on
blood viscosity
total blood vessel length
blood vessel diameter
what causes vasodilation
nitric oxide
what causes vasoconstriction
endothelin
where is blood diverted to during exercise
diverted from digestive tract to skeletal muscles
describe fluid flow across capillaries (specifics)
arterial end - fluid is lost, filtration, pushing greater than sucking
mid capillary - no net movement, pushing=sucking
venous end - reabsorption, pushing less than sucking
what is stage 1 of atherosclerosis
plaques develop in inner wall of artery (contain fat, cholesterol and calcium deposits)
what is stage 2 of atherosclerosis
formation is due to inflammatory response that is initiated by the deposition of lipoproteins (LDL) in vessel wall
what is stage 3 of atherosclerosis
process takes several years and causes narrowing of vessel and hardening of walls
what is stage 4 of atherosclerosis
plaques can rupture and promote formation of thrombus (or an embolus)
how many stages/statements of atherosclerosis
4
what causes hypertension
genetics, smoking, lack of exercise, diet rich in saturated fat and high cholesterol levels
TRUE OR FALSE
symptoms of a cardiovascular disease are always experienced before a heart attack or stoke
FALSE
many people don’t experience any symptoms of cardiovascular disease
