Cardiac System Flashcards
functions of cardiovascular system
move substances
- materials entering the body
- materials moved from cell to cell
- materials leaving the body
components of the cardiovascular system
- blood
- blood vessels
- heart
blood components
connective tissue with cellular components suspended in a fluid matrix called plasma
plasma = 55%
cellular components = 45%
total blood volume
5L = 2L(cells) + 3L(plasma)
What’s in the blood?
- water = 92%
- proteins = 7%
- rest = 1%
- ions present: na, cl, h, k, ca, hco3
(liver makes most plasma proteins+ secretes them to the blood)
cellular elements in the blood
- red blood cells (erythrocytes
- white blood cells (leukocytes)
- platelets (thrombocytes)
blood soldiers
white blood cells are the only fully functional cells in the circulation
phagocytes
neutrophils, monocytes, and macrophages
- engulf and ingest foreign particles aka bacteria
immunocytes
lymphocytes
- responsible for specific immune responses directed against invaders
granulocytes
basophils, eosinophils, neutrophils
- contain cytoplasmic inclusions that give them a granular appearance
hematopoietic stem cell
single precursor cell type for blood cells to descend from
hematopoiesis
the synthesis of blood cells, begins early in embryonic development and continues through life
leukocyte production
leukopoiesis (colony-stimulating factor CSF)
red blood cell production
erythropoiesis (erythropoietin (EPO))
platelet production
thrombopoiesis (thrombopoietin (TPO))
complete blood count (CBC)
provides information on several parameters of blood
mean corpuscular volume (MCV)
average volume of one red blood cell
mean corpuscular hemoglobin (MCH)
amount of hemoglobin per RBC
mean corpuscular hemoglobin concentration (MCHC)
amount of hemoglobin per volume of one RBC
hemoglobin
the oxygen-binding protein that gives RBC their color reversibly binds to oxygen
1 hemoglobin can bind to four oxygen molecules
oxyhemoglobin
hemoglobin bound to oxygen
% saturation of Hb
amount of oxygen bound to hemoglobin at any given
(amount of O2 bound / max that could be bound) X 100% =
oxyhemoglobin saturation curves
- relationship between and how much oxygen binds to hemoglobin in vitro
normal pressure=90% bound
Fetal vs. adult hemoglobin
- fetal hemoglobin has a higher oxygen affinity
- babies automatically switch from fetal to adult (takes 2 years)
- fetal levels drop 10% every 2 weeks
Bohr effect
Shift in hemoglobin saturation curve that results from a change in pH
(13% more O at ph 7.2 than 7.4)
Hemoglobin and Temperature
- increasing temperature decreases the affinity of hemoglobin for oxygen
- this allows for easier release of oxygen to tissues important in excercise
Hemoglobin and CO2
- CO2 increases hydrogen ion concentration and lowers tissue pH
- hemoglobin’s affinity for oxygen decreases
walls of blood vessels
- smooth muscle
- elastic connective tissue
- fibrous connective tissue
vasoconstriction
narrows the diameter of the blood vessel lumen
vasodilation
widens the diameter of the blood vessel lumen
microcirculation
arterioles, along with capillaries and small postcapillary vessels called venules
continuous capillaries
have a lining that contains pores that let only small molecules (hormones, glucose, and gases) pass through. Nervous system, skin, and lungs
Fenestrated Capillaries
have larger openings between the cells that allow quick exchange of substances (nutrients and blood) kidneys, small intestine, and endocrine glands
sinusoidal capillaries
discontinuous, have even larger gaps and pores. liver, spleen, lymph nodes, bone marrow, and endocrine glands
veins
- valves in the veins prevent backflow of the blood
- veins have to work against gravity
- when the skeletal muscles compress the vein, they force blood toward the heart
blood pressure
blood pressure is highest in the arteries and decreases continuously as blood flows through the circulatory system
systolic pressure
highest pressure in the circulatory system created by the contraction of ventricles of the heart
diastolic pressure
lowest pressure in the circulatory system associated with the relaxation of ventricles of the heart
arterial blood pressure (BP)
“blood pressure” reflects driving pressure created by the pumping action of the heart
normal blood pressure
120/80
hypotension
low blood pressure
- blood flow and oxygen supply to the brain are impaired and the person may become dizzy or faint
hypertension
high blood pressure
- high pressure on the walls of blood vessels may cause weakened areas to rupture and bleed into the tissues
cerebral hemorrhage
blood vessel ruptures in the brain
stroke
loss of neurological function
pulse
the rapid pressure increase that occurs when the left ventricle pushed blood into the aorta transmitted through fluid filled arteries
pulse pressure
measure of the strength of the pressure wave defined as PP= SP - DP
mean arterial pressure (MAP)
MAP = DP + 1/3 (SP - DP)
distribution of blood to tissues
varies according to metabolic needs and governed by a combination of local control mechanisms and homeostatic reflexes
blood flow through arteries
- depends on resistance
- higher the resistance the lower the blood flow through it
blood flow through blood vessels
determined by the vessel’s resistance to flow
Boyle’s law
provides the basis for circulation
- flow 0( ^P/R
- blood flow increases in response to a pressure gradient and blood flow decreases as the resistance increases
local control
of arteriolar resistance matches tissue blood flow to the metabolic needs of the tissue
sympathetic reflexes
mediated by the CNS maintain mean arterial pressure and determine blood distribution to various tissues to meet homeostatic need such as temp regulation
hormones
particularly those that regulate salt and water excretion by the kidneys influence blood pressure by acting directly on the arterioles and by altering autonomic reflex control
sympathetic neurons
part of the autonomic nervous system, controls involuntary body functions
parasympathetic nervous system
facilitates the normal day-to-day functions
paracrine signaling
type of cell communication where a cell releases a signal to change the behavior of nearby cells
exchange at capillaries
tissues have more capillaries per unit area, subcutaneous tissue and cartilage have the lowest capillary density, and muscles/glands have the highest
- lowest velocity, highest cross-sectional area
capillaries
- have the thinnest walls of all the blood vessels (single layer of flattened endothelial cells supported on a basal lamina
- RBCs single file
diffusion
oxygen and carbon dioxide diffuse freely across the thin endothelium
transcytosis
leaky cell junctions, most small, dissolved solutes can diffuse freely between the cells or through the fenestrations
bulk flow
mass movement of fluid as the result of hydrostatic or osmotic pressure gradients
absorption
when direction of bulk flow is into the capillary
filtration
when the direction of bulk flow is out of the capillary
starling forces
regulate bulk flow in the capillaries
hydrostatic pressure
lateral pressure component of blood flow that pushes fluid out through the capillary pores
osmotic pressure
determined by solute concentration of a compartment (due to proteins in plasma but not interstitial fluid)
- the osmotic pressure created by the presence of these proteins is known as colloid osmotic pressure (oncotic pressure)
net pressure
net pressure= hydrostatic pressure - colloid pressure
- (+) = filtration
- (-) = absorption
lymphatic system
- allows the one-way movement of interstitial fluid from the tissues into the circulation
- interact with cardiovascular, digestive, and immune systems
functions of lymphatic system
- returning fluid and proteins filtered out of the capillaries to the circulatory system
- picking up the fat absorbed at the small intestine and transferring it to the circulatory system
- serving as a filter to help capture and destroy foreign pathogens
lymph nodes
bean shaped nodules of tissue with a fibrous outer capsule and an internal collection of immunologically active cells
edema
accumulation of fluid in the interstitial space
causes of edema
- inadequate drainage of lymph
- blood capillary filtration that greatly exceeds capillary absorption
elephantiasis
chronic condition marked by gross enlargement of the legs and lower appendages when parasites block the lymph vessels
Three factors that disrupt the normal balance between capillary filtration and absorption are
- increase in capillary hydrostatic pressure
- decrease in plasma protein concentration
- increase in interstitial proteins
increase in capillary hydrostatic pressure
usually indicative of elevated venous pressure Ex: heart failure one ventricle loses pumping power
decrease in plasma protein concentration
severe malnutrition or liver failure
increase in interstitial proteins
excessive leakage of proteins out of the blood decreases the colloid osmotic pressure gradient and increases net capillary filtration
the heart (overview)
- workhorse of the body
- muscle contracts continually
- 1 min = work of a 5 pound weight up one foot
- needs constant nutrients and oxygen
location of heart
apex points toward left side of body, broader base is behind sternum
pericardium
tough, membranous sac where the heart is encased
pericardial fluid
inside pericardium lubricates external surface of heart as it beats within sac
pericarditis
inflammation of pericardium
aorta and pulmonary trunk (artery)
direct blood from the heart to tissues and lungs
venae cavae and pulmonary veins
return blood to the heart
pulmonary circuit
takes blood to the lungs and gills
systemic circuit
takes blood to the body
steps of both circuits
- (P) blood enters the right atrium
- (P) blood enters the right ventricle
- (P) blood is pumped to the lungs
- (S) blood returns to the left atrium
- (S) blood enters the left ventricle
- (S) blood is pumped to the body
atrioventricular (AV) valves
between the atria and ventricles
semilunar (SL) valves
crescent moon shape, between the ventricles and their arteries
AV flaps
slightly thickened at the edge and connect to the ventricular side to collagenous tendons, the chordae tendinea which are tethered to ventricular muscle known as the papillary muscle
tricuspid valve
valve that separates the right atrium and right ventricle (three flaps)
bicuspid/mitral valve
valve between the left atrium and left ventricle (two flaps)
autorhythmic cells/pacemakers
specialized myocardial cells that signal for myocardial contraction
myogenic
signal for contraction comes from within the heart muscle itself
intercalated disks
have two components
- desmosomes
- gap junctions
contraction of sarcomere
- the filaments slide past one another
- the sarcomere shortens with no change in lengths of the thin (actin) and thick (myosin) filaments themselves
thin filament proteins
troponin and tropomyosin
troponin and tropomyosin
- block myosin binding sites on actin
- muscle relaxes
- when calcium binds contractions begin again
cardiac muscle contraction can be graded
- force generated by cardiac muscle is proportional to the number of cross bridges that are active
- number of active bridges is determined by Ca bound to troponin
- low Ca = small contraction force
myocardial action potentialscontractile and autorythmic myocardium play a role
how is resting potential of a neuron maintained?
- extracellular fluid: more na and cl
- interior of membrane: more k
How do voltage gated ion channels work?
action potential depends on voltage gated channels
- depolarized the channels open
action potential in muscle/neuron?
the rapid depolarization phase of the action potential is the result of entry Na and the steep repolarization phase is due to k leaving the cell
myocardial contractile cell
has longer action potential due to Ca entry
phase 4: resting membrane potential
myocardial contractile cells have a stable resting potential of about -90mV
phase 0: depolarization
voltage-gated Na channels open, allowing Na to enter the cell and rapidly depolarize it. the membrane potential reaches +20mV before the channels close
phase 1: initial repolarization
when the Na channels close, the cell begins to repolarize as K leaves through open K channels
phase 2: the plateau
the result of two events:
- decrease of K permeability
- increase in Ca permeability
phase 3: rapid repolarization
the plateau ends when ca channels close and K permeability increases again the slow K channels responsible for this phase are like those in the neuron
Length of action potential
- neuron/skeletal muscle: 1-5msec
- contractile myocardial cell: 200msec
Why can autorhythmic cells generate action potentials without the nervous system?
- result of unstable membrane potential
- called pacemaker potential
- when it gets to threshold an action potential fires
Why are is the membrane potential unstable?
- autorhythmic cells contain I channels
- I channels are permeable to Na+ and K+
- happens at rest
heart rate
determined by the speed with which pacemaker cells depolarize
why is it necessary to direct electrical signals through AV node?
- apex to base contraction
- Av node delay allows the atria to complete their contraction before ventricular contraction begins
diastole
the time during which cardiac muscle relaxes(dilation)
- relaxation decreases pressure
systole
the time during which the muscle contracts(contraction)
- contraction increases pressure
end-diastolic volume (EDV)
- maximum volume of blood that ventricle will hold during cardiac cycle
end-systolic volume (ESV)
the minimum volume of blood the ventricle contains during one cycle
stroke volume
the amount of blood pumped by one ventricle during a contraction mL/beat
SV=EDV-ESV
ejection fraction (EF)
volume of blood ejected from ventricle/contraction
EF=SV/EDV
cardiac output (CO)
the volume of blood pumped by one ventricle in a given period of time
CO=heart rateXstroke volume
Frank-Starling law of the heart
- stroke volume is proportional to end diastolic volume
- as additional blood enters the heart the heart contracts more forcefully and ejects more blood
electrocardiograms (ECG/EKG)
surface electrodes to record internal electrical activity because salt solutions, such as our NaCl based extracellular fluid
- sum of multiple action potentials
towards + electrode
ECG wave goes up from the baseline
towards - electrode
the wave points downward
p wave
atrial depolarization
p-r segment
conduction through AV node and AV bundle
QRS complex
ventricular depolarization
T wave
ventricular repolarization
what does ECG show?
information on heart rate and rhythm, conduction velocity, and even the condition of tissues in the heart
On ECG: Heart Rate
peak of one R wave to the peak of the next R wave
- normal heartrate is 60-100 beats per minute
tachycardia
faster-than-normal heart rate
bradycardia
slower-than-normal heart rate
arrhythmia
irregular heart rhythm, can result from a benign extra beat or from more serious conditions such as atrial fibrillation, in which the SA node has lost control of the pacemaking
