circulation pt1 Flashcards
what process do unicellular organisms and some small metazoans use to transport molecules?
they lack circulatory systems and rely on diffusion to transport molecules
diffusion can be rapid over small distances, but is very slow over large distances
how do large animals move fluid through their bodies?
bulk flow or convective transport
bulk flow: fluids move from high pressure area to low pressure area
major function of circulatory systems
(depends on the organism)
transport oxygen, carbon dioxide, nutrients, waste products, immune cells, signaling molecules
circulatory systems move fluids by…
increasing the pressure of the fluid in one part of the body, causing fluid to flow down pressure gradient
3 main components of a circulatory system
pump or propulsive structures (e.g. heart)
system of tubes, channels or spaces
fluid that circulates through the system (blood)
3 types of pumps
CHAMBERED HEARTS with contractile chambers
SKELETAL MUSCLE (squeeze on vessels to generate pressure)
PULSATING BLOOD VESSELS (peristalsis- rhythmic contractions of vessel wall pumps blood)
what to one-way valves do?
help ensure unidirectional flow
4 types of fluid that are circulated
BLOOD (in closed circulatory system)
HEMOLYMPH (in open circulatory system)
INTERSTITIAL FLUID (extracellular fluid, directly bathes tissues)
LYMPH (fluid that circulates in the lymphatic system, secondary circulatory system of vertebrates)
what does the lymphatic system do?
carries lymph that has filtered out of the vessels
in open circulatory systems, fluid comes in direct contact with tissues in spaces called…
circulating fluid and interstitial fluid are…
sinuses
(all hemocoels are sinuses)
not separated (mixed)
in closed circulatory systems, circulatory fluid remains within vessels and does NOT….
circulating fluid and interstitial fluid are…
come in direct w/ the tissues, molecules must diffuse across vessel wall
separated
order of vessels blood goes through in one circulatory cycle, starting from when it leaves the heart
aorta
arteries
arterioles
capillaries
venules
veins
vena cava
sponges, cnidarians and flatworms lack a circulatory system but have mechanisms for…
propelling fluids around their bodies
(ciliated cells in sponges and flatworms)
(muscular contractions of the body wall pump in cnidarians)
describe the circulatory system in polychaetes and oligochaetes (Annelids)
circulate interstitial fluid with cilia or muscular contractions of body wall
open in polychaetes
closed in oligochaetes
describe the circulatory system in molluscs
all have hearts and some blood vessels
most have open system
cephalopods have closed systems w/ 2 branchial hearts and 1 systemic heart
describe the circulatory system in crustaceans
all have one or more heart and some blood vessels
all have open systems
some control over distribution of blood flow in body
describe the circulatory system in insects
open circulatory system
multiple contractile hearts along dorsal vessel
hemolymph enters from ostia and leave from arteries and aorta
tracheal system for gas transport
describe the circulatory system in urochordates (tunicates)
open circulatory system
tubular heart at base of digestive tract
describe the circulatory system for cephalochordates (lancelets)
closed system with a few open sinuses
tubular heart at base of digestive tract and pulsatile blood vessels
describe the circulatory system in vertebrates
all have closed systems
what was the circulatory system first evolved for
to transport nutrients to body cells
closed systems evolved independently in jawed vertebrates, cephalopods and annelids
what are some of the advantages
increased blood pressure and flow
increased control of blood distribution
can allow for high metabolic rates
how does the circulatory system fit into O2 delivery?
pump blood to where & when it is needed (both loading and unloading)
what are 2 ways tissues can obtain more O2 with relation to the circulatory system?
heart pumps more blood per unit time
tissues extract more O2 from capillaries
what is the equation for O2 uptake?
O2 uptake = Q (CaO2 - CvO2)
CaO2= content of O2 in arterial blood (carrying capacity)
CvO2= content of O2 in venous blood
describe the circulatory plan/ blood flow of vertebrates
- muscular chambered heart contracts to increase the pressure of the blood and flow away from heart in arteries
- blood flows from arteries to arterioles within tissues then to capillaries
- capillaries merge to form venules which then merge into veins
- veins carry blood to heart
what is the site of diffusion of molecules between blood and interstitial fluid?
capillaries
what are the three layers of blood vessel walls
TUNICA INTIMA (internal lining: smooth, epithelial cells)
TUNICA MEDIA (middle layer: smooth muscle + elastic connective tissue)
TUNICA EXTERNA (outermost layer: collagen)
why do arterial vessels have much more muscle/ layers/ are thicker
blood close to the heart is leaving with high pressure
the muscles help reinforce the vessel walls and dampen pressure oscillations
characteristic of capillaries
3 types
- lack tunica media and tunica externa
CONTINUOUS (cells held together by tight junctions, in skin + muscle)
FENESTRATED (cells contain pores, specialized for exchange, in kidneys + endocrine organs + intestine)
SINUSOIDAL (few tight junctions, most porous for large protein exchange, in liver + bone marrow)
describe the circulatory system in jawed vertebrates
all have a closed system
structure depend on respiratory strategy
water-breathing fish: SINGLE CIRCUIT, some have accessory hearts in tail
air-breathing tetrapods: PULMONARY CIRCUIT (right side of heart) + SYSTEMIC CIRCUIT (left side of heart)
the 2 in-series capillary networks in closed single-circuit systems
respiratory capillaries and systemic capillaries
describe resistance to blood flow in gills and tissues in a single-circuit, closed circulatory system
additive (Ohm’s law)
describe the fish heart
2 CONTRACTILE CHAMBERS: atrium + ventricle (contract in sequence + generate enough blood pressure to propel blood around entire body)
2 OTHER CARDIAC CHAMBERS:
SINUS VENOSUS- elastic chamber, collects venous blood, SINOATRIAL region contains CARDIAC PACEMAKER
BULBUS ARTERIOSUS- elastic chamber connected to aorta, dampens pressure oscillations
describe the double-circuit, closed circulatory system
right atrium + right ventricle pump deoxygenated blood to pulmonary circuit
left atrium + left ventricle pump oxygenated blood to systemic circuit
what is the benefit of a double-circuit, closed circulatory system?
the 2 pumps can create different blood pressures, but their flow output must be the same
why do we want high pressure in systemic system
because there are lots of organs to circulate through and therefore high resistance
why do we want low pressure in pulmonary system
there is shorter distance to travel through
lung is delicate, if pressure is too high, capillaries can be easily damaged or blood can enter the lung (in the lung, there is no tissue on the other side of capillary wall to prevent capillary from rupturing)
what is the equation for bulk flow?
what is Poiseuille’s equation?
Q= deltaP / R
Q= deltaP * pi * r^4 / 8Ln
L=length of tube
n= viscosity of fluid
what is the advantage of arranging organs/ tissues in parallel
resistance in series: Rt= R1 + R2…
resistance in parallel: (1/Rt)= (1/R1) + (1/R2)
less resistance will be experienced in a parallel system
what is the formula for flow?
Q= V/t
volume of fluid transferred per unit time
equation for blood velocity
v=Q/A
Q= flow
A= cross-sectional area of the channels
if total cross-sectional area of capillaries is very large-> velocity slow -> long time for diffusion
why do you want low velocity in capillaries?
need to give RBCs enough time for efficient O2 unloading
which vessels have the highest/lowest total cross-sectional area? velocity?
highest A: capillaries
lowest A: aorta and vena cava
highest v: aorta and vena cava
lowest v: capillaries
4 main parts of vertebrate hearts
PERICARDIUM: sac of connective tissue surrounding heart, space between parietal and visceral layers has lubricating fluid to prevent wear and tear
EPICARDIUM: outer layer of heart continuous w/ visceral pericardium, contain nerves that regulate heart and coronary arteries
MYOCARDIUM: layer of heart muscle cells (cardiomyocytes)
ENDOCARDIUM: innermost layer of connective tissue covered by epithelial cells, in contact w/ blood
what is the function of coronary artery
provides oxygenated blood to the heart
myocardium is oxidative; has high O2 demand
2 types of myocardium
where are they mostly found?
COMPACT: tightly packed
SPONGY: loosely connected
mammals have mostly compact myocardium
fish and amphibians have mostly spongy myocardium, but active fish (tuna) have more compact
what does spongy myocardium allow for?
much greater surface area for gas exchange.
blood going through the blood are deoxygenated (single circuit) but spongy myocardium can obtain the leftover O2
spongy myocardium are arranged as TRABECULAE that extend into chambers
4 chambers of fish heart, in order of venous to arterial
sinus venosus
atrium
ventricle
bulbus arteriosus
chambers in amphibian hearts
which atria does oxygenated and deoxygenated blood go into?
2 atria, 1 ventricle, conus arteriosus
pulmonary vein-> left atrium
deoxygenated blood from body-> right atrium
what helps prevent mixing of oxygenated and deoxygenated blood in ventricle of amphibian heart?
trabeculae of spongy myocardia
what is the function of the spiral fold in conus arteriosus?
direct deoxygenated blood to pulmocutaneous circuit and oxygenated blood to systemic circuit
chambers in the reptile heart
2 atria, 3 interconnected ventricular compartments
blood from left atrium goes to cavum arteriosum first
what are the ventricular compartments in the reptile heart?
where do they lead to?
(connected to right atrium and cavum arteriosum) cavum venosum-> systemic aorta (left and right)
cavum pulmonale-> pulmonary artery
cavum arteriosum
describe the pathway of oxygenated blood from lungs through the reptile heart
oxygenated at lungs-> left atrium-> cavum arteriosum -> cavum venosum-> left or right aorta-> body
describe the pathway of deoxygenated blood from body through the reptile heart
deoxygenated blood at body-> right atrium-> cavum pulmonale-> pulmonary artery-> lungs
describe right-to-left shunt in reptile hearts
deoxygenated blood bypasses pulmonary circuit and re-enters systemic circuit
describe left-to-right shunt in reptile hearts
oxygenated blood reenters pulmonary circuit (sent back to lung)
aids oxygen delivery to myocardium in right heart
how is shunting in crocodile hearts facilitated?
pulmonary artery closes cog valve and prevents blood flow
describe the crocodile heart
2 atria + 2 ventricle
blood from lungs enter left atrium-> left ventricle-> right aorta-> foramen of Panizza connects right aorta to left aorta-> body-> right atrium + ventricle-> pulmonary artery or left aorta
pulmonary artery is in right ventricle
what does the anastomosis between the left aorta and right aorta do?
allows left aorta and right aorta to equilibrate blood
in birds and mammals, what are the ventricles separated by
intraventricular septum
what are the valves in the birds and mammal hearts?
AV valves: between atria and ventricles
semilunar valves: between ventricles and arteries (pulmonary or aortic)
2 phases of the cardiac cycle
systole (contraction)
diastole (relaxation)
describe the cardiac cycle in mammals
2 atria contract simultaneously
pause
2 ventricles contract simultaneously
atria and ventricles relax while the heart fills w/ blood
how and when are ventricles filled in birds and mammals
ventricles fill passively during ventricular diastole (atrial contraction adds a little blood to ventricles)
ventricular diastole-> negative pressure in ventricle-> pressure in atrium higher
how is the ventricle filled in fish and some amphibians
filled by contraction of atrium
bc they have lower blood pressure, atrium filling is reduced, need pressure to push blood to ventricle
why does the left ventricle contract more forcefully and develop higher pressure to pump blood?
bc it pumps to body (systemic system) longer distance + more resistance
why does right ventricle contract less forcefully?
bc less pressure is needed to pump blood through the lungs
why is resistance in pulmonary circuit low?
bc of high capillary density in parallel-> large cross-sectional area
(also bc of low pressure, to protect blood vessels of lung and prevent edema)
sequence of AV valve and semilunar valve open/close on left side of heart
AV valve close
semilunar valve open
semilunar valve close
AV valve open
what controls cardiac contractions (3)
neurogenic pacemakers (invertebrates)
myogenic pacemakers (rhythm generated in myocytes, vertebrates + some invertebrates)
artificial pacemakers (rhythm generated by device)
in vertebrates, what produces rhythmic depolarizations?
what is a feature they have to ensure coordinated contractions?
cardiomyocytes (do not require nerve signal)
cardiomyocytes are electrically coupled via gap junctions to ensure coordinated contractions (action potential passes directly from cell to cell)
where is the pacemaker in fish, amphibians, reptiles, birds + mammals
fish: sinus venosus
tetrapods: sino-atrial node (SA node)
characteristics of pacemaker cells
derived from cardiomyocytes
small w/ few myofibrils + organelles
do not contract
have unstable resting membrane potential that depolarizes until it reaches threshold and initiates an action potential
steps in terms of membrane potential changes to trigger an action potential
CELL DEPOLARIZES
(permeability of K+ down-> open Na+ channels-> mV up
permeability of Ca2+ up-> mV up)
threshold reached (-40 mV)
opens voltage-gated channels
initiates action potential
CELL REPOLARIZES
permeability of K+ up-> mV down
permeability of Ca2+ down-> mV down
channels open at diff. mVs
what are the major differences between action potentials and pacemaker potentials?
depolarization is mainly done by Ca2+ instead of Na+ in pacemaker potential
action potentials have hyperpolarization
K+ repolarizes in both cases
stimulation of what nervous system INCREASES rate of pacemaker potentials
sympathetic nervous system
stimulation of what nervous system DECREASES rate of pacemaker potentials
parasympathetic nervous system
how can norepinephrine and epinephrine alter heart rate
norepinephrine (noradrenaline) from sympathetic neurons
epinephrine (adrenaline) from adrenal medulla (triggered by sympathetic neuron)
increase heart rate by opening more Na+ and Ca2+ channels
more depolarization-> more AP
how can acetylcholine alter heart rate?
acetylcholine from parasympathetic neurons
more K+ channels open-> hyperpolarize pace maker cells-> more difficult to reach threshold-> less AP-> heart rate slowed
2 ways depolarization travels through the
heart
specialized conducting pathways
directly between cardiomyocytes
how do depolarizations travel by specialized conducting pathways
with modified cardiomyocytes
lack contractile proteins
spread action potential rapidly throughout myocardium
can undergo rhythmic depolarizations
how do depolarizations travel directly between cardiomyocytes
cardiomyocytes are electrically connected via gap junctions
electrical signals can pass directly from cell to cell
how does AP cause cardiomyocyte contraction
action potential from adjacent cell
voltage gated Ca2+ channel open and Ca2+ enter cell
Ca2+ triggers release of Ca2+ from sarcoplasmic reticulum
(most Ca2+ come from the SR)
Ca2+ binds to troponin to initiate contraction
how does relaxation of cardiomyocyte happen
when Ca2+ unbinds from troponin
Ca2+ is pumped back into the sarcoplasmic reticulum for storage
Ca2+ exchanged w/ Na+ and Ca2+ exits cell
Na+ gradient maintained by Na/K ATPase
what is the conducting pathway in the mammalian heart for atria contraction
SA node depolarizes, depolarization spreads via internodal pathway
AV node delays signal, depolarization spreads through atria via gap junction
atria contract
why does the AV node need to delay the signal
so atria can contract before the ventricle does
what is the conducting pathway in the mammalian heart for ventricle contraction
depolarization spreads through bundles of His and Purkinje fibers
depolarization spreads upwards through ventricle
ventricle contract
how do action potentials in cardiomyocytes differ from those in skeletal muscle or pacemakers
there is a plateau phase in cardiomyocyte action potentials
plateau phase: extended depolarization that lasts as long as the ventricular contraction
what is the plateau phase caused by?
what is the function of the plateau phase?
caused by Ca2+ entry via L-type channel
prevents tetanus (prevents muscle contraction from occurring again before it recovers)
what is the difference between skeletal muscle and cardiac muscle in terms of relation between action potential and conttraction
skeletal muscle: does not have time to recover/relax when action potentials are fired very rapidly
cardiac muscle: plateau phase of action potential ensures that heart muscle relaxes before next contraction
(plateau phase extends until peak of muscle contraction)
what is an electrocardiogram?
describe the kinds of waves you would see
composite recording of action potentials in cardiac muscle
shows net change, not directional
P wave: atrial depolarization
QRS complex: ventricular depolarization
T wave: ventricular repolarization
how are electrical and mechanical events correlate in the heart
electrical events initiate contractile events
what mechanical event do each of the waves found on a ECG initiate
P wave initiates atrial contraction and atrial blood pressure peak
QRS complex initiates ventricular contraction and ventricular blood pressure peak
T wave initiates ventricular relaxation (it is a repolarization)
energy in aorta is slowly released
what is end-systolic volume and end-diastolic volume
how do we find the cardiac stroke volume
ESV: volume of blood in ventricle after contraction
EDV: volume of blood in ventricle before contraction
cardiac stroke volume = EDV - ESV
does a heart beat fully empty the human ventricle?
no
but there is also no need to bc increasing BPM is more effective to get more cardiac output
why does blood aortic blood pressure decrease during diastole?
to have negative pressure to bring blood into the chamber
equation for cardiac output
what does it tell us
cardiac output = HR * SV
volume of blood pumped per unit time
HR= rate of contraction (beats per minute)
SV= volume of blood pumped with each beat (= EDV-ESV)
how can cardiac output be modified
by regulating heart rate and/or stroke volume
heart rate: modulated by autonomic nerves and adrenal medulla
stroke volume: modulated by various nervous, hormonal, and physical factors
