2. Flashcards
How do seals optimize oxygen during a dive?
- seals can consciously program where their blood flows
- needs to hold breath for a long time during a dive, but make sure tissues get oxygen
- scientists monitored their blood flow, and notices that the change for optimal flow for diving occurred before diving, thus likely consciously
- human bodies do this passively
Components of Circulatory system
- circulatory system move fluids by increasing the pressure of the fluid in one part of the body
- fluid flows through body, “down” pressure gradient
THREE MAIN COMPONENTS ARE NEEDED:
1. Pump or propulsive structures
2. Fluid that circulates through the system
3. System of tubes, channels, or spaces (vessels)
Single Pump
- One way flow is controlled by valves present
- Has a contractile chamber
- The contractile chamber creates a pressure gradient that opens and closes valves, and blood flows unidirectionally through the vessel
Types of Pumps
There are three pumps that could be present in the circulatory system:
Contractile Chamber:
- the heart is composed of chambers which as individual pumps
(())
Skeletal Muscle:
- may contract to propel fluid
- plays important role in returning blood from lower extremities
- speed and pressure are lost as moves through the vessels, therefore, skeletal muscles are wrapped around vessels and when they contract (walking) it helps move blood upwards ((||))
Pulsating Blood Vessels:
- tube-like hearts in invertebrates and early vertebrate embryos (or heart embryos) (||)
**good photo pg 21
Heart/circulatory structure can vary in
- heart structure
- number of hearts, number of chambers
- snake hearts get bigger when needed
- zebrafish hearts can regenerate
of Chambers
- Bony dish - arranged in series
Amphibian - 3 chambers
Non-crocodilian reptiles - 5 chambers
Fish Heart (path)
Sinus venosus –> atrium –> ventricle –> bulbus arteriosus
Fish Heart (Info)
- chambers are in organized series
- serial contractile chambers
(Sinuous venosus, atrium, ventricle, bulbus arteriosus) - a simple one-way circuit
- there is no pulmonary circuit because fish do not breath through lungs
- valves are passive
- open and close according to pressure differences/gradient
(fluid into space, build up pressure, eventually opens valve, flows out) - ensure unidirectional blood flow
- blood flows into spongy myocardium in ventricle
Spongy Myocardium - patchy area in ventricle - receives oxygen from blood flowing through ventricle, to oxygen heart (spongy - not as compact as other hearts) - in teleosts, bulbus arteriosus is volume and pressure reservoir (called conus arteriosus in cartilaginous fish)
Amphibian Heart (pathway)
sinus venosus –> right atrium –> ventricle –> conus arteriosus –> pulmonary artery –> lungs–> pulmonary vein–> left atrium –> ventricle –> conus arteriosus –> systemic arteries
Amphibian Heart (Info)
*two atria, one ventricle
- ventricle is main contractile unit of the heart
- the atria can contract to a less extent, providing blood from an oxy or deoxy source
*Atria
Left: receives oxygenated blood from lungs/pulmonary veins
Right: receives deoxygenated blood from system circulation through sinus venosus; oxygenated slightly from skin
*Ventricle
- oxy- and deoxy- kept separate
–> TRABECULAE - lines of contractile tissue in ventricle that helps separate deoxy and oxy
–> there is risk of mixing, but this heart still fits the frogs needs the best
- sends blood to the conus arteriosus
*Conus arteriosus
- receives blood from ventricle
- moves blood to pulmocutaneous (pulmonary artery), or to systemic arteries (arteries that will supply blood to the rest of the body)
- SPINAL FOLD - keep blood separate in conus arteriosus
Why does the frog permit/withstand mixing of deoxygenated blood?
- the heart is built/structured to minimize mixing (trabeculae, spiral fold)
- the frog can exchange o2 and co2 in lungs and through skin
–> deoxygenated blood running through system can pick up oxygen
Turtle, Lizard and Snake Hearts (info)
** non-crocodilian
* 5 - chambered heart
- two atria + (3-chambered) ventricle
- Conus arteriosus has disappeared
*Ventricle split into three different chambers
Cavum Venosum: leads to systemic arteries
- receives from right atrium (deoxygenated), sends to cavum pulmonale
- receives from cavum arteriosum, sends to systemic arteries
Cavum Pulmonale - leads to pulmonary artery
Cavum Arteriosum - receives from pulmonary vein and left atrium, sends to cavum venosum
Turtle, Lizard, Snake (pathway)
- 5-chambered heart
sinus-venosus –> right atrium –> cavum venosum –> cavum pulmonale –> pulmonary artery –> lungs –> pulmonary vein –> left atrium –> cavum arteriosum –> cavum venosum –> systemic arteries (left or right aorta) –> systemic body
Shunting in Reptile Hearts
- reptiles tend to go underwater for long periods of time, thus need to maximize oxygen circulation to important places
- functions of the two shunts are debated
- mostly see shunts as adaptions
R-L SHUNT - associated with diving
- circulates low deoxy blood back into system
- blood flows right atrium to right aorta
L-R SHUNT - associated with oxygenating the heart
- sending oxy blood into pulmonary circuit because the pulmonary circuit returns oxygen quicker to the heart blood vessels
- blood flows left atrium to pulmonary artery
Birds & Mammals Circulatory Circuits
birds and mammal’s circuits are very similar
- 2 atria, 2 ventricles
- separated pulmonary and systemic circuit
- differences, ex. birds would be optimized for flight
4 systems have evolved to supply oxygen to hearts of animals
- mammalian heart - coronary vessels
- most teleost - spongy myocardium
- some fishes - vessels and spongy myocardium
- some octopuses - vessels, and mixing of blood from the ventricle to the coronary vessels
Mammal Heart Oxygen Supply
- the heart is an active muscle demanding large amounts of O2, and nutrients
- the mammalian heart is compact - really dense network of myocardium (myocardial cells packed closely together)
- blood from ventricles cannot perfuse cardiac muscles
- coronary arteries supply blood to heart (myocardium)
–> profuse the whole heart - has coronary vessels
- compact myocardium
- outside of the heart is covered in vessel
- blood pumped through heart does not oxygenate
Most Teleost Heart Oxygen Supply
- has spony myocardium
–> directly oxygenated from blood flowing through ventricle
–> blood flowing through ventricle, profusion through myocardiocytes/myocardium, has exchange - no coronary vessels
- ancestral heart
- blood not well oxygenated (deoxy through heart to gills, gills to system, system to heart)
- underwater, different ways to profuse, evolved on land to have more efficient ways (coronary vessels)
Some Fish Heart Oxygen Supply
- outer layer compact
–> require coronary arteries to supply blood - inner layer spongy myocardium
Some Octopuses Heart Oxygen Supply
- myocardium of mixed structure with blood flowing from lumen into coronary veins
- from lumen to coronary veins
- mixing of blood from the ventricle to the coronary vessels
- octopi can have more than one heart
Myocardial Cells
Main contractile unit of heart, able to function as one coheasive unit
Mammalian Cardiac Cycle
- movement from the atria to ventricles relies on pressure gradients
- contraction of the ventricles actively moves blood to the aorta or pulmonary artery
- works as a cohesive unit
- atrial contraction, ventricle contraction, valve opening and closing must all work cohesively in the right order
Two Phases of Mammalian Cardiac Cycle
SYSTOLE
- contraction
- blood is forced out into the circulation
DIASOTLE
- relaxation
- blood enters the heart
Definition:
vein and artery
Vein - blood vessel returning to heart
Artery - blood vessel leaving/leading away from heart
Human Heart (pathway)
vena cava –> right atria –> right atrioventricular valve –> right ventricle –> pulmonay valve –> pulmonary trunk (artery) –> lungs (pulmonary circuit)
–> pulmonary veins –> left atrium –> left atrioventricular valve –> left ventricle –> aortic valve –> systemic aorta –> systemic circuit
the human heart pathway descriptive
- after passing through the systemic circuit, the blood now partly deoxygenated flows into the vena cava then into the right atrium
- blood flows through the right atrioventricular valve to enter the right ventricle
- the right ventricle pumps the deoxygenated blood through the pulmonary valve into the pulmonary trunk (artery), from which it flows to the lungs in the pulmonary circuit
- blood that has been oxygenated in the lungs travels to the heart in the pulmonary veins and enters the left atrium
- blood flows through the left atriventricular valve to enter the left ventricle
the strongly muscular left ventricle pumps the oxygenated blood through the aortic valve into the systemic aorta from which it flows to the entire systemic circuit
control of heart contraction
Vertebrates hearts are MYOGENIC
- autonomous (governs itself, self-directed) contraction
- cardiomyocytes produce spontaneous rhythmic depolarizations
- do not require nerve signal
–> though nervous stimulate can affect rate of depolarization, cannot stop/turn of beath
Depolarization vs. hyperpolarization
Depolarization - the cell becomes less negative
Hyper-polarization - the cell becomes more negative
Neuron Depolarization vs. Cardiac Muscle Cell Depolarization
- relies on electrical signals to go through depolarization
Neuron - fire action potential, becomes less negative, as falls repolarizes and returns to baseline quick
Cardiac Muscle Cell - same thing, different speeds
- action potential fires, depolarization, followed by a SLOW repolarization
- extended repolarization phase is to control heartbeat, maintain steady heartbeat
Cardiomyocytes - control of contraction
Cardiomyocytes
- the cells responsible for generating contractile force in the heart
- beat in unison, coordinated contraction
- all cardiomyocytes have rhythmic depolarization
- rates varies among cells
- the heart is made up of many different cardiomyocytes
- action potential passes directly from cell to cell through gap junction
MC: Gap Junctions Mediate
a) active transport
b) facilitated diffusion
c) diffusion
d) intracellular receptors
B) facilitated diffusion - diffusion happening through the protein channel
Cardiomyocyte Characteristics
Cardiomyocytes are electrically coupled via GAP JUNCTIONS
- action potential passes directly from cell to cell
- ensures coordinated contractions
Gap Junction - proteins organized into channels, set of 6 proteins formed into a channel
- electrical signals in form of ions can move into the enxt cell through hole in barrier/gap
Cardiomyocytes connected at INTERCALATED DISKS
- mechanical adhesions
- keeps cell in close contact
Pacemaker Cells
Cardiomyocyte cells with the fastest intrinsic rhythm
- in the sinus venosus in fish
- in the right atrium of other vertebrates - at a specific spot called the SINOATRIAL (SA) NODE
- its purpose is not to contract but to depolarize and send signals to true contractile cardiomycoytes who have the right contractile machinery (protein, striated)
The Conduction System
- each area spreads/signals action potential/electrical impulses to next area, results in contractions and repolarization
SA NODE (atrium)–> wait –? atria contract –>AV Node –> Av bundle –> Bundle branches –> ventricles contact
SA Node
- contains pacemaker cells, original depolarization/action potential
Av Node
Delays spread before sending signal to AV bundle
- the atria and ventricles do not contract at the same time
–> if they did there would be times where there is no blood in the heart
–> blood is always filling or exiting the ventricles
The AV node allows atria to contract and eject their blood into ventricle before the ventricles contract
AV Bundle and Bundle Branches
AV Bundle - in septum between ventricles
Bundle Branches - feed out and make contact with right and left ventricles
The Spread of Electrical Impulse Through Heart
- the initiation and spread of depolarization during a heartbeat
- Depolarization begins in the SA node and spreads outward through the atrial muscle
- Although depolarization spreads rapidly throughout the atrial muscle, its spread into the AV node is delayed. The depolarized atria start to contract
- Once the AV node becomes depolarized, the depolarization spreads very rapidly into the ventricles along the conduction system. Atrial muscles start to repolarizes
- The nearly simultaneous depolarization of cells through the ventricular myocardium leads to forceful ventricular contraction
SA Node –> atrial muscle –> wait, atria contracts –> AV Node –> AV Bundle –> Bundle branches –> ventricles contract
Heart Function: electrical, valve, flow, and volume relation
1. Atrioventricular valve open
2. Atrioventricular valve closed
- Atrio-ventricular valve open, volume in ventricle is high, ventricular outflow is low, aortic valve is closed
- depolarization of ventricle
- atria contraction
- P-wave, atrial systole - Atrioventricular valve closed, volume in ventricle is low, ventricular outflow is high, aortic valve is open
- contraction of ventricle
- S-T, ventricle ejections
Electrocardiogram
-monitors electrical currents
- represents all (sum of ) action potentials in the heart
Waves of Electrocardiogram
P Wave - atrial depolarization
QRS Complex - ventricular depolarization and atrial repolarization
T Wave - ventricular repolarization
Species Differing Wave Forms
- not all wave forms are the same
human vs. octopus
- ventricular depolarization is similar - rapid change
- other differences not overly explained, could be due to octopus’ multiple hearts
How we detect electrical currents of the heart via electrodes on the skin
- body tissues and extracellular fluids conduct electricity, thus carrying the signal of the heart
- amplifiers can be used (ex. alcohol)
- humans require 10-12 electrodes on chest, arm, and hips (clinic standard)
What EKG Tells You
Heart Rate:
- Tachycardia - higher than normal heart rate
- Bradycardia - lower than normal heart rate
Cardiac Rhythm:
- Arrhythmias - abnormal heart rhythm
Atrial Fibrillation
Conduction through the atrium is disturbed
- p wave association
- don’t see P, may not see T
- less severe than ventricle, still have QRS
Ventricular Fibrillation
Conduction through the ventricle is disturbed
- QRS complex associated
- No QRS
- Deadly
AV Block
Communication between atria and ventricles impaired
- P and QRS complex dissociated
- Can lead to V-fib.
- things occurring at random (p, qrs, t)
- electrical signals from the atria are not connecting the right way
Neurogenic Heart
What controls the cardiac cycle?
- cardiac ganglion (large yellow network) consisting of 9 neurons - controls contractions throughout the heart
- heart requires neural input to beat
–> neurons must send signals to myocardiocytes - controlled in an on/off way
Myogenic Heart
What controls the cardiac cycle?
- the heart has an internal rhythm from pacemaker cells
- external factors cannot turn beat on/pff, but can change the speed of the heartbeat
Intrinsic Control
Nervous Control
Hormonal Control
Myogenic Heart - intrinsic control
- internal pacemaker
- frank-sterling mechanism
–> stretching or filling heart impact
Myogenic Heart - nervous control
Synapse on part of heart, increase of decrease rate
- Sympathetic - increased rate
- Parasympathetic - decreased rate
- SA node is highly inverted (supplied with nerves)
–> signal can change rate of depolarizing from pacemaker - ventricle innervated, allows force of contraction to vary
–> changes force contraction
Myogenic Heart - hormonal control
- epinephrin from adrenals - heart racing
- circulating factors in blood that make way up to heart
Cardiac Output (CO) (eqn)
CO = heart rate * stroke volume
CO (ml/min) = HR (bearts/min) * SV (ml/beat)
CO = how fast * how much
Volume of blood pumped per unit time
Cardiac Output (CO) can be modified by either term:
Heart Rate (HR):
- modulated by nervouse and endocrine system
- bradychardia - greek bradus - slow
- tachycardia - greej takhus - swift
Stroke Volume:
- modulated by various nervous, hormonal, and physical factors
Stroke Volume
??
Frank-Starling Mechanism
- stretching of the cardiac muscle tends to increase the force of contraction by an effect exerted at the level of the individual muscle
OR
- the more the heart fills, the stronger the force of contraction
Frank-Starling Mechanism or…
-the more the heart fills, the stronger the force of contraction
- Artificial stretch (in lab)
- Physiological stretch - increased HR, ventricles fills faster –> contraction is stronger
–> CO is increased, faster beat, more volume - internal control mechanism
- related to the way the contractile proteins and cardiomyocytes are set up
- contractile proteins - myosn and actin (make striations)
Pygmy Shrew
- Have hearts at the mass 2x suppose to be
- thus should have high HR, but slow relative to mass
(as hearts get smaller HR gets bigger) - HR is limited to by how fast action potentials can be fired, Shrew likely maxed its rate, though predictions thought it to be higher, therefore evolved a larger heart to make up for it
–> increased SA when maxed HR to increase CO
Secratariot
- faster horse in one circuit
- study of heart found to be almost triple size of regular horse heart
- increase SA, increase CO, increase aerobic activity
- fast pumping of to and from lungs, high stamina
ex. bigger heart correlate to better stamina
Pacemaker Cells
- non-contractile, muscle-like cell
- in SA
- set rhythm of contraction for the entire heart
- job to depolarize, and action potential
Electrical Chemical Gradietns of the Cardiomyocite
K+ –> leak out
- keep in to depolarize
Ca2+ –> leak in
- come in to depolarize
Na+ –> leak in
- come in to depolarize
Difference of Action Potentials in Different cells
Pacemaker - slow response depolarization, faster repolarization
Cardiomycoytes - fast response depolarization, slower repolarization
due to differing ion channels in cell, and its needs
