Biology 225 - Exam 4

Sponge circulation

• body is full of pores that lead to the inner cavity

• Flagella move water in and out

Cnidaria circulation

use muscular contractions to propel water into mouth and out through cavity

Platyhelminthes & nematode circulation

use contractions of a muscular pharnyx to propel fluid though cavity

Many animals (have/ do not have) a circulatory system

do not have

Diffusion

• very slow over long distances

• exponential

ostia

tiny openings that let hemolymph (insect’s blood) enter the heart

• when heart relaxes, ostia open and hemolymph flows in

• when heart contracts ostia close and hemolymph is pushed forward through body

Closed circulatory systems

support high pressures

3 general characteristics of circulatory systems

1. one or more pumps/structures that apply force to drive fluid flow

2. system of tubes through which the fluid can flow

3. a fluid that circulates through the system

Simple vertebrate circulatory system

heart —> arterioles—> capillaries —> venules —> veins —> back to heart

large vein/vein structure

1. tunica externa

2. tunica media

3. tunica initima

4. endothelium

venule structure

1. tunica externa

2. tunica intima

capillary structure

1. tunica intima

elastic/muscular artery

1. tunica externa

2. tunica media

3. tunica intima

4. ednothelium

arteriole structure

1. tunica media

2. endothelium

continuous capillary

• In: brain, muscle, skin

• Made of: tight junctions, endothelial cells, intercellular clefts

Fenestrated capillary

Allows more rapid exchange

in: kidney, endocrine organs, intestines

made of: tight junctions, endothelial cells, intercellular clefts, and fenestrations (pores)

Sinusoidal Capillary

allows passage of large molecules and even cells (proteins, RBC)

In: liver, bone marrow

made of: tight junctions, endotheial cells, intercellular clefts

Bulk blood flow controlled by

tubes, pumps, and valves

Law of bulk flow

• fluids flow doen pressure gradients

• resistance opposes this movement

• quantifies the relationship between flow, pressure, and resistance

• Q = change in P/R

resistence of a tube is…

inversely related to its radius (to the 4th power)

R = 8nL/r^4

Poiseulle’s equation assumes

unbranched and rigid tubes, a uniform and simple fluid, and steady flow

Blood is used to circulate…

• respiratory gases

• nutrients

• waste products

• hormones

• antibodies

• salts/ions

Ohm’s law and bulk flow

• both reflect newtons second law

• substances move bc they are acted upon by force

• such movement is impeded by reisitance

in a closed circuit, flow will be…

uniforms at all points within circuit

velocity of fluid is….

inversely proportional to the cross-sectional area of the vessel

At circulatory system’s capillary beds blood velocity is ______ and cross sectional area is _____

lowest; highest

Diastole

relaxation

negative pressure

blood flows in

systole

contraction

positive pressure

blood flows out

Ventricular Diastole

pressure in the atria exceeds ventricular pressure, the AV valves open, and the ventricles fill passively

Atrial systole

atrial contraction forces additional blood flow into ventricles

ventricular systole

during early ventricular systole, ventricular contraction causes the AV valves to close, while pressure within the ventricles rises without a change in volume

Ventricular systole

as ventricular pressure continues to increase and exceeds arterial pressure, the semilunar valves open, allowing blood to be ejected into the arteries

Ventricular diastole

as the ventricles relax, arterial pressure exceeds ventricular pressure, causing the semilunar valves to close. ventricular pressure falls without a change in volume

AV valves

atrial —> ventricular

• right = tricuspid

• left = bicuspid

• weak enough to open with pressure but strong enough to not open backwards (prolapse). chordae tendinae & papillart muscles prevent prolapse

Semilunar valves

ventricular —> out

• pulmonary valve

• aortic valve

• weak enough to open from ventricular contraction which allows blood to flow out of the heart but strong enough to withstand return pressure

Mammalian heart is myogenic

• pacemaker cells have unstable resting membrane potential

• funny channels open which increases the permeability of membrane to Na+, which increases the membrane potential gradually

• when reaching threshold, L-type Ca2+ channels open, triggering an action potential

• Then channels close and K+ channels open, repolarizing the cell, and the cycle begins again

Cardiac action potential

0. cell reaches threshold and voltage-gated Na+ channels open, increasing Na+ permeability and depolarizing cell

1. voltage gated Na+ channels inactivate and K+ channels open, causing tansient outward K+ current, resulting in a slight repolarization

2. these inward rectifier K+ channels close and L-type voltage-gated Ca2+ channels open, causing the plateau phase of the action potential of the action potential

3. L-type voltage gated Ca2+ channels close and K+ channels open causing repolarization

4. the cell returns to the resting membrane potential

depolarization of the SA node pacemaker spreads to the rest of the heart with characteristic time-course

1. SA node depolarizes which spreads rapidly via the internodal path

2. AV node delays the signal. The depolarization spreads through atria via gap junctions, and causes the atria to contract

3. depol spreads rapidly through the bundles of His and purkinje fibers

4. depol spreads upward through ventricle, causing it to contract

EKGs detect

integrated electrical activity of the whole heart

p-wave

depolarization of atria, small wave before QRS complex

QRS complex

depolarization of the ventricles and repolarization of the atria

t-wave

repolarization of ventricles, small wave after QRS complex

Supraventricular tachycardia (SVT)

a rapid heart rhythm originating above the ventricles (atria or AV node)

• usually caused by reentry circuit or enhanced automaticity

Electrical path:

• normal conduction: SA —> AV —> His —>Bundle branches —> purkinje

• SVT conduction: reentrant loop in atria or AV node —> repeated rapid impulses

ECG appearance:

• narrow QRD complex

• rapid, regular HR

SVT consequences

• palpitations & dizziness

• chest pains & shortness of breath

• hypotension

Left bundle branch block (LBBB)

• conduction abnormality where electrical impulses are delayed or blocked in the left bundle branch

• leads to asynchronous ventricular activation

LBBB consequences

• ventricular dyssynchrony

• reduced cardiac efficiency

• may worsen heart failure

Funny current

caused by non-selective cation channels that open at hyperpolarized voltages and close upon depolarization. Na+ is the major cation underlying the current.

SA node ionic conductance creates…

a self-sustaining pacemaker

parasympathetic effect on heart

slows down & restored balance

sympathetic effect on heart

accelerates and activates

The parasymp and symp branches of the autonomic nervous system by

reciprocally controlling HR by controlling the pacemaker potential in the SA node

symp nervous system mechanism for accelerating the SA node pacemaker

via B-adrenergic recpetors

• sympathetic neurons either trigger norepi or trigger epi via adrenal medulla

• those then trigger B receptors of autorhythmic cells

• increase Na+ and Ca2+ influx

• increase rate of depolarization

• increase HR

parasymp nervous system mechanism for slowing SA node pacemaker

via muscarinic Ach receptors

• parasymp neurons trigger Ach

• Ach binds muscarininic receptors of autorhythmic cells

• increase in K+ efflux, decrease of Ca2+ influx

• hyperpolarizes cell

• increases time for depolarization

• decrease HR

cardiac output is the product of

HR and stroke volume

sympathetic nervous system modulates force of heart contractions

increasing force of contraction increases stroke volume which increases cardiac output

• norepi and epi increase contractility by binding to B receptors on the cardiomyocyte & activating an adenylate cyclase mediated signal transduction path that activates protein kinases which phosphorylate various proteins & cause an increase in the rate and strength of contraction

ventricular contraction

blood flows rapidly into the aorta during the ejection phase of ventricular contraction, pushing out on the walls of the aorta and causing it to expand

ventricular relaxation

as the heart relaxes, blood flow into the aorta ceases, but flow out into the arterioles continues, reducing the aortic pressure. elastic recoil of the arterial walls helps to push blood through the vasculature, maintaining pressure and flow

skeletal muscle pump contracted

puts pressure on the vein, pushing blood in both directions. The resulting pressure opens the proximal one-way valve and closes the distal one-way valve, squeezing blood toward the heart and preventing backflow

skeletal muscle pump relaxed

relaxation reduces pressure on the distal valve, which opens and allows blood to flow in. Back pressure from the blood in the proximal segment of the vein closes the proximal valve, preventing backflow

Systolic pressure

• highest arterial BP

• associated with ventricular contraction

Diastolic pressure

• lowest arterial BP

• associated with ventricular relaxation

diffusion for gas exchange is sufficient for…

single cells or very small/thin organisms

Bulk flow of water or air

can deliver O2 directly to internal cells and tissues

Gas exchange between respiratory medium and blood and then the blood and the interstitial fluid relies on…

diffusion

Fick equation

quantifies the rate of diffusion through a tissue sheet

boyle’s law

governs bulk flow

P1V1=P2V2

In order to diffuse into a cell, gas molecule must…

first dissolve in liquid, this is why respiratory surfaces must be kept moist

Henry’s Law

concentration of a gas in aqueous solution depends on its solubility. Gasses show different solubilities in different media

partial pressure gradients

dive gases to dissolve in liquids

Total pressure =

sum of partial pressures

Diffusion of a gas in liquid depends on

solubility and molecular weight (graham’s law)

ration of SA to volume changes

drastically as the radius of a cell or tissue increases

mode of respiratoy perfusion affects

efficiency of gas exchange

In tidally ventilated respiratory organs, the PO2 of the blood can approach…

the PO2 of the exhalant bc animals can’t completely empty and refill respiratory cavities with each breath

unidirectional ventilation…

makes greater exchange efficiency possible

countercurrent exchange

increases gas extraction

combination of unidirectional ventilation and countercurrent flow…

makes it possible for the PO2 of blood to approach the Po2 of the inhaled medium. With countercurrent flow can result in the blood’s Po2 exceeding the Po2 of the exhaled medium

buccal-opercular pump

how fish ventilate their gills

1. water enters buccal cavity

2. opercular cavity expands & pressure drops

3. water enters opercular cavity

4. water flows out of opercular cavity back to environment

fish combine…

unidirectional flow and countercurrent exchange

What kind of lungs do birds have?

stiff, hexagonal lungs

What kind of respiration do birds use

unidirectional

bird unidirectional respiration

1. expansion of chest during the first inhalation causes fresh air to flow through the bronchi to the posterior air sacs

2. compression of the chest during first exhalation pushes the fresh air fron the posterior sacs to the lungs

3. expansion of the chest during the second inhalation causes stale air to flow from the lungs into the anterior air sacs

4. compression of the chest during the second exhalation pushes stale sir fron the anterior air sacs out via the trachea

ventilation of the mammalian lung is controlled by

contraction and relaxation of the diaphragm

mammalian respiratory system

trachea —> bronchi —> bronchiole —> terminal bronchiole —> respiratory bronchiole —> alveoli

purpose of all those branches in lungs

increasing surface area

Alveoli

lungs terminate in alveoli which are the gas exchange site in mammals between the blood and atmosphere

Type I cell

are super thin for proper diffusion

Type II cell

secretes surfactants (mucus)

Hemoglobin structure

2 alpha subunits, 2 beta subunits, and have heme group containign iron

Hemoglobin purpose

bind O2 to increase the O2 carrying capacity of blood. Dissolved O2 is bound by the hemoglobin within RBCs.

Bohr effect

pH affects the oxygen equilibrium of hemoglobin low pH & Po2 get higher and increase in CO2 makes blood more acidic

Haldane effect

oxygenated hemoglobin carries less CO2

deoxygenated hemoglobin can carry more CO2

Physiological importance of haldane effect

in tissues (low O2)

• hemoglobin releases O2 —> deoxygenated —> promoted CO2 uptake

In the lung (high O2)

• hemoglobin binds O2 —> oxygenated —> promotes CO2 unloading

CO2 transported in 3 forms

1. dissolved CO2 - 7%

2. carbaminohemoglobin - 23%

3. bicarbonate - 70%

carbonic anhydrase catalyzes the formation of …

bicarbonate

At the tissues, conditions favor release of ___ and conversion of _____ to ___

O2; CO2; bicarbonate

• binding of H+ to Hb reduces its affinity for O2 and favors the formation of carbaminohemoglobin

• carbonic anhydrase in the RBC drived the conversion of CO2 to bicarbinate. A Cl-/bicarbonate exchanger moves bicarbonate out of the RBC (cloride shift)

At the lungs, conditions favor the formation and release of ___ from ___

CO2; bicarbonate

• binding O2 to Hb causes H+ release, which favors the formation and release of CO2

• an increase in H+ (decrease in pH) in the RBC drives the conversion of bicarbonate to CO2. The Cl-/bicarbonate exchanger moves bicarbonate to the RBC (a reversed chloride shift)

Asexual reproduction

• progeny are genetically identical (or very similar) to their parent

• budding, fragmentation, cloning: single individual produces at least one offspring that is genetically identical to the parent

• pathenogensis: egg develops w/o fertilization (can be haploid or diploid)