Unit 4b -Circulation Basics Continued Flashcards
what is the relationship between heart size and body size and o2 consumption
heart rate - 0.6% of body mass in vertebrates
smaller body- smaller heart- higher 02 consumption
Blood volume characteristics
- humans have 5L
- vertebrates 5-15% of weight
- left/right heart have equivalent volume, not pressure
- entire ejected volume is accomodated in vascular stretching
Stroke volume
SV= end diastole volume (just before contraction) - end systole volume (volume of ventricle after contraction)
-blood ejected by the heart
what factors incfluence stroke volume through end diastole volume and end-systolic volume (4 and 2)
end-diastole
- venous filling pressure
- pressure generated during atrial contraction
- distensibility of the ventricular wall
- the time available for filling the ventricle
end systole
- pressure generated during venricular contraction
- the pressure in the outflow channels from the heart
Heart beat sequence
filling (ventricle filling by the atrial contraction is only 30% of the blood pumped into the aorta- most comes from venous filling pressure- blood directly through the atria into the ventricles- atrial contraction tops it off)
contractions
emptying and relaxing
Isomeric vs. Isotonic contraction
- isomeric= constant colume, increase muscle tension, ventricular presure
- isotonic = constant pressure, large change in volume
Q=
SV x Heart rate (f) (L/min)
two methods of increasing cardiac output
- increase frequency of beating- pigeon
- increase stroke volume- trout
Positive inotropic effect vs. negative inotropic effect
positive inotropic- increases muscle contraction
negative inotropic- slows contractions/ weakens their force
Positive inotropic effect on heart contractions
- decrease end-systolic volume or increase end-diastolic volume
- controls the duration of the action potential and intercellular ca2+ mechanisms
Frank-starling mechanism
- stretch produces more forecul contractions
- stroke volume is proportional to diastolic filling
Sympathetic innervation of catecholamines (beta receptors)
- increases the rate of ventricular emptying
- increases ventricular contractility though increasing intracellular ca2+
- stimulates pacemaker to go off more
- same stroke volume, shorter time
Laminar flow
- smooth flow, streamlined
- force (pressure) required to slide adjacent layers past each other
- viscosity - internal friction, resistance to sliding
- plasma skimming
plasma skimming
separation of blood and plasma in a vessel
turbulent flow
irregular, noisy,
- used for blood pressure measurments
- velocity is seldom high enough to cause turbulence
Change in pressure =
Q x R (cardiac output x resistance)
pressure is related to velocity - decreases from atrial to venous sides
-R compares resistance to flow
R is porportional to….
Ln/r^4
length x viscosity/ radius ^ 4
r is the main determinant of R
Q is porportional to….
r^4 and R
= pi/8 x change in pressure r^4/ Ln
Fahraeus- LIndquist Effect
flow is inversely porportional to viscosity
- plasma skimming, tendency for RBCs to accumulate in the center of bloodstream
- reduces resistance
- apparent increase in viscostily for small vessels bc Redblood cells fills the lumen of the blood vessel
Poiseulle’s equation
applies to steady flow in straight, rigid tubes
- blood vessels are not rigid tubes
- -elastic fibres in wall allow distension
- -increase in presure = increase in radius
- -flow rates higher at absolute pressure
Compliance
- change in volume/ change in presuure
- high distendibility = high compliance (think of a baloon that can expand more when you put in less or the same pressure
- venous system has high compliance - volume reservoir
Why do we need to control arterial blood pressure
- keep an adequate supply of blood to the heart
- supplying blood to other organs
- mainanance of tissue volume and composition fo interstitial fluid
mechanisms for controling circulation - time and location
timing - acute vs. chronic
locaiton - affect the central cardiovascular system or the peripheral (capillary system)
What controls blood pressure
p= QR Q=SV*f
heart rate and vasoconstriction/ vasodilation
Pressor sensor
- sympathetic pathway
- increased heart rate, contractility and vasoconstriction
- net increase in cardiac output
depressor sensor
parasympatheditc, net decrease in cardiac output
-decrease in heart rate and vasodilation
Arterial Baroreceptors
- baroreceptor reflex
- respond to pressure as the blood vessel walls stretch
- increased baroreceptor firing in response to increased BP of increased pressure pulsatiility
How does the arterial baroreceptor affect peripheral resistance
- increase BP= decrease Q = decrease in R
- decrease BP= increase in Q = increase in R
Arterial chemoreceptors
- primarily regulate breathing
- change according to CO2, O2 and pH
- cause decreased heart rate and vasoconstriction if the animal is not breathing
Cardiac receptors 2 types
atrial receptors and ventrical receptors
atrial cardiac receptor
- afferent fibers embeded in the atrial wall
- stretch sensitive secratory cells
- —secreate ANP- (antrial natriuretic peptide)
- —decrease BP and blood volume by increasing uring production and sodium excretion
ventricle receptors
mechanoreceptors and chemoreceptors
- responsible for pain during heart attacks
What is capillary flow in the body porportional to?
-metabolic activity
what is the sequence of priority for blood flow
brain- heart/lungs- gut, liver muscles
ischemia vs. hyperemia
ischemia= inadequate blood supply hyperemia= too much blood
what are the three neruonal and harmonal mechanisms for control
- sympathetic nerves
- ciculating catecholamines
- parasympathetic nerves
Sympathetic nerves and control
releases norepinepherine
- binds alpha adregenic receptos
- increases vasoconstriciton, increases areterial BP
- brains and lungs lack alpha adrenoreceptors
Circulating catecholamines and control
adrenal medulla releases epinepherine
- primarily binds beta adrenoreceptors
- produces vasodilation
- increases venous return to stimulate heart to increase cardiac output
parasympathetic nerves and control
- innervation of arterioles of brain and lungs
- release of acetocholine causing vasodilation
what physiological changes occur in active tissues
- decreased oxygen, increased co2, decrease in pH, increased adenosine, increased heat, increased potassium
- results in vasodilation
- ischemia and reactive hyperemia
what can cause vasodilation near active cells
- heat
- compounds produced by the endothelial cells
- inflammatory mediators (histamine, plama kinins)
Vasoconstriction influences near active cells
-compounds produced by endothelial cells (endothelin)
-inflamattory mediators (antihistidines)
-clotting factors (thromboxane A2)
agiotensin ii
what state are fetal lungs like
they are collapsed- they have a high resistance to blood flow
unique features of the fetus circulat
-ory system (4)
ductus arteriosis, forman ovulae, umbilical veins and arteries, ductous venosus
ductus arteriosis
-joins pulmonary artery and aortic arch
Formen ovulae
joins left and right atria
Ductous venosus
joins umbilical vein and inferior vena cava
what changes in the fetal circulation at birth
-lungs inflate, reducing resistance to flow
-placental circulation ceases, increasing systemic resistance to flow
pressure in left atrium exceeds right- closes the formen ovulae
-ductus arteriousis becomes occluded
what occurs in cells when you excercise
- decrease in o2 and pH,
- increase in heat, CO2
- increase in blood flow and redistribution of blood flow
what is the nervous system’s response to increased excercise
- increased sympathetic, decreased parasympathetic stimulation
- isomeric contractions- increase BP
- isotonic contractions- increase cardiac output (Q)
how does Q change during excercise
- increased heart rate (chronotropic) and contractility (inotropic) effect
- increased venous returen due to skeletal muscle pumping
- active hyperemia
what parts of your body experience vasodilation or vasoconstriction during excercise
active tissue- vasodilation
gut and kidney- vasodilation
how does the systemic blood pressure remain constant during excercise
- decrease in peripheral resistance, but increased cardiac output
How to mammals get oxygen while submersed/ nonmammmals
mammals- lungs, blood(hemoglobin), muscle (myoglobin), body water
non-mammals - cutaneous respiration and rectal respriation
bradychardia
-the diving reflex in mammals
==sitmulation of facial water receptros
stimulation of arterial chemoreceptos (o2, cos2, pH)
lack of stimulation of lug stretch receptors
parasympathetic activity
other circulatory changes during diving
- vasoconstricion and redistribution of blllod flow to brain and heart (muscles us anaerobic respiration
- mainenance of arterial BP: lower heart rate + fewer capillary beds open
- recovery- seals hyperventilate after they dive
Diving in other vertebrates (birds, amphibians and reptiles, fish)
- birds- bradychardia triggered by chemoreceptors not submerssion
- reptile and amphibians- cutanious and rectal respiration are importnat
- fish- “reverse” diving reflex when removed from water
