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Physiology Test 2


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skeletal and cardiac
single or binucleate
single nucleate
cardiac and smooth
spontaneous activity
some spontaneous and some not
sarcoplasmic reticulum (SR)
axial system of tubules and vesicles surrounding the myofibrils and organized in regular repeating pattern
smallest organized unit of contractile mechanism
thin dark bands that define ends of sarcomere
I Band
light area on either side of Z line
A Band
midway between any two Z lines; dark area
M line
dark stripe through middle center of A band
H zones
lighter areas on both sides of the M line
carry blood from heart to tissues
carry blood from tissues to heart
pulmonary circulation
serves lungs
systemic circulation
serves all other organs
lymphatic system
transports fluid, proteins, WBCs, and micelles from tissues to vascular system
aorta and large arteries
conduits with elastic walls; assit in maintaining high pressures
Resistance is due to?
friction between flowing blood and vessel walls and bw molecules and blood cells
Arteries inflow during Systole
Sysole=contraction=ejection of blood from ventricle; arteries inflow is greater than outflow
Arteries outflow during diastole
Diastole=Relaxation=blood filling ventricle; Arteries outflow is greater than inflow
Smaller arteries and arterioles
conduits with add'l function of regulation which organs and tissues will receive more or less flow; more smooth muscle
resposible for exchange of nutrients; oxygen, and waste bw blood and tissues; no muscle, only basement membrane and endothelial cells
Venules, small veins, and large veins
thinner, less muscular walls; more compliant; return blood from capillaries and operate in maintaining optimal distribution of blood V bw venous and arterial systems
3 Types of vessels in vascular system
1. aorta and arteries:distribution 2. microcirculation: diffusion and filtration 3. Vains: collection
Order of hydrostatic pressure
Volume capacity of systemic arterial distributing system (High P)
most limited, least variable, and least dilatable
Low pressure system
greatest cpacity and most dilatable; serves as resorvoir function
Lymphatic system constituents
lymph, lymphoid tissue, and lymphoid organs
Lympoid organs are
spleen, thymus, bone marrow, and nodes
3 Functions of Lymphatic System
1. returning filtered plasma protein and excess interstitial fluid to blood 2. transporting lipids into interstitial lymphatic vessels to blood 3. helping defend the body against pathogens
Lymphatic Capillaries
tiny, closed-end channels with porous walls made of endothelial cells; allow proteins and fluids to enter the lumen wehn P is higher in interstitial space than capillary
collecting vessels
connective tissue and scattered smooth muscle cells and endothelium
right lymphatic duct
right half of head and neck, right half of upper thorax and right upper extermities into right subclavian vein
thoracic duct
drains rest of body into left subclavian vein
Length/Cross-Sectional Area
Factors determining changes in resistance
length of conduits, cross-sectional area, and series or parallel
peak arterial pressure; sysolic pressure
normal SBP
120 mm Hg
minimum arterial pressure; diastolic pressure
normal DBP
80 mm Hg
pulse pressure
difference between SBP and DBP
Magnitude of pulse pressure is determined by?
stroke volume and distensibility of arteries
mean arterial pressure=1/3 pulse pressure+DBP
mean arterial pressure/resistance
inversely proportional to radius raised to 4th power
total peripheral resistance
Plasma skimming
when a vessel gives off a smaller branch andthe flowing blood is of low hemocrit
turbulent flow depends on?
velocity, tube diameter, and fluid density and viscosity
For water, when does turbulence occur?
when Nr exceeds 2000
What values of Nr can be reached in aorta and pulmonary artery?
3600-5800 and higher
Murmurs during systole are due to?
turbulence when rate of flow is high in exercise or when viscosity is low in anemia
Anatomical constrictions that follow turbulence
dilations that follow turbulence
Poiseuille's equation
Resistance= 8Lpi/pi r cubed
neurogenic control
nerve-dependent contractile activity
myogenic control
nerve-independent contractile activity
myogenic contractile activity
spontaneous depolarization, pH, pO2, pCO2, and mechanical stimuli (stretch)
What substances are found released around arteries, precapillaries, and capillaries?
NE, ACh, CO2, lactic acid, and nuclear metabolism products
Local metabolic effects are stronger in?
metarterioles and precapillary sphincters
What primarily affects the arterioles
constrictor nerve fibers
What protects a tissue against ischemia?
locally induced vasodilation when arterial pressure is decreased or when constiction of arterioles reduces blood flow
Autoregulation of local blood flow is affected by?
myogenic response to stretch, vasomotor effects of local metabolites, and tissue pressure
Autoregulation (Bayless Mechanism)
Myogenic Response to stretch:constriction when P increases and dilation when pressure decreases
2 objections to Myogenic Response to Stretch
Bayless Mechanism: 1. Increased vasoconstrictor response to increased wall tension is positive feedback->cardiovascular instability; increased BP will elevate flow resistance further raising BP leading to add'l vasoconstriction 2. smooth muscle contractile response to vascular distension abolishes stretch stimulus
Autoregulation (Effects of Local Metabolies)
instability (caused by + feedback) can be limited by "metabolic vasodilators" and by max range of vasomotor response;due to structural complexity, unlikely that myogenic response to stretch would operate within rigid diameter limits
What functions together to produce autoregulation?
local metabolic factors and myogenic mechanism
Autoregulation (Tissue Pressure Effects)
increase in perfusion pressure leads to increase in tissue pressure by increasing capillary hydrostatic pressure and enhancing fluid movement into EC; this is followed by compression of capillaries, venules, and small veins and increases resistance in blood flow
Net movement out of capillary because?
Hydrostatic pressure is greater than osmotic pressure
Dynamic center
Net movement into capillary because?
osmotic pressure is greater than hydrostatic pressure
increased movement of fluid out of capillaries
recall of fluids
net movement of fluids into capillaries
Found in all types of blood vessels except capillaries
adrenergic nerve endings
What vessels have richest innervation of adrenergic nerve endings?
arterioles and arteries
vasoconstrictor nerve fibers
important in homeostasis of blood pressure and blood flow, including reflex adjustments that arise from baro and chemoreceptors
Vasoconstrictor neural input
controls blood flow and influences peripheral heat exchange
inhibition of vasoconstriction
pressor and depressor are located in?
vasomotor center in medulla
function of pressor
maintain arterial BP even with no afferent input
function of depressor
discharges in response to afferent input to inhibit tonic pressor activity in order to optimize BP
What modifies rate of pressor nerve discharge?
afferent input and upper CNS input to medulla pressor
Bainbridge Reflex
rise in HR in response to rapid infusion of blood or saline; not a response to stretch
autonomic neurohumoral control
secretion of epinephrine from adrenal medulla in response to stimulation
Simulation of what causes autonomic neurohumoral control
splanchnic nerve, lateral columns of spinal cord, vasomotor center in medulla, or lateral hypothalamus
function of renin-aldosterone system
neurohumoral regulating mechanism for body sodium and water content, arterial blood pressure, and potassium balance
secreted by kidney; converts angiotensinogen to angiotensin I
ACE I (angiotensin converting enzyme)
sound in lungs; coverts angiotensin I to angiotensin II
most potent vasoconstrictor
Angiotensin II
Angiotensin II
stimulates vasoconstrictor neurons centrally and can cause release of ADH; rapidly metabolized by angiotensinases in peripheral capillary bed
rate-limiting step in angiotensin production
renin release
Where is renin produced?
juxtaglomerular apparatus of renal artery
Renin is produced in response to?
decrease in renal artery pressure, decrease in EC fluid V, stimulation of sympathetic nerves to kidney, or alteration in distal tubule sodium load
What inhibits renin release?
elevated blood sodium, potassium, angiotensin II, or ADH
Where are chemoreeptors located?
carotid and aortic bodies adjacent to carotid sinus and roor of aorta
fibers of aortic body run into?
fibers of carotid body arE?
branches of glossopharyngeal nerves
Where is largest blood flow?
carotid body
What stimulates chemoreceptors?
anoxia, hypercapnia, and acidosis.
primary effect of chemoreceptor stimulation on pulmonary and systemic
reflex vasoconstriciton
local hypnoxia does what to systemic vascular muscle?
local hypnoxia does what to pulmonary vascular muscle
Circulating Vasoconstrictors
ADH, Epi, NE, Ang II and Ang I
histamine, EDRF, EDHF, Kinins, Decreased pO2, decreased pH, Increased pCO2, increased temp, adenosine, ANP, Some PG's, Some LT'S, VIP, Substance P, ACh
Local Vasoconstrictors
serotonin, vold vasoconstriction, AA PG's, LT's, decreased pO2, and endothelin
atrioventricular valves
tricuspid (R) and bicuspid (L)
semilunar valves
pulmonary and aortic valves
RA is continuous with?
vena cavae
layer of endothelial cells
cardiac muscle cells
connective tissue, fat, and coronary arteries
distensibility of pericardium
resists large, rapid increase in cardiac size
due to automaticity; myogenic spontaneous polarization of cardiac myocytes because of decrease of K+ permeability and conductance
pacemaker cells
fastest rate of decrease in K+; more permeable to Na+which keeps resting potential closer to 0; hyperexcitable
due to intercalated discs allowing transmission of AP's b/w neighboring cells allowing heart to function as a synctitium
What is responsible for synchronized cardiac cycle
SA Node-AV node-Bundles of His-Pirkinje fibers-ventricular cells
Why does cardiac muscle only contract in twitch fashion?
long duration of AP and long duration of refractory period
recording of electrical activity of heart; converts minute surface currents to movements or to spot of light on a cathode ray tube
isoelectric line
line of no deflection; occurs when entire heart is either depolarized or resting
occurs when atrial muscle is depolarized
QRS complex
ventricular muscle is depolarized
Lead I
Leads II and III
b/w left leg and right and left arms; most sensitive to activity proceeding from base to apex of heart
ventricles relax and fill with blood
ventricles are contracting and ejecting blood from heart
What keeps SL valves shut?
reverse pressure gradient
isovolumetric contraction
both AV and SL valves are closed
stroke volume
volume of blood ejected in a single beat
diastole commences with?
isovolumetric relaxation phase
Formula for Stroke volume
1st heart sound
AV valves closing
2nd heart sound
SL valves closing
3rd heart sound
Venous flow into atria
4th heart sound
Venous flow into Ventricle
Heart murmur
valvular obstructions causing turbulent blood flow or weak valves causing regurgitation
Athletes murmur
large ventricular mass and strong ventricular contractions due to left ventricular hypertrophy
Cardiac output
amt of blood pumped out of LV and into aorta during one minute;
formula for cardiac output
heart rate x stroke volume
How is CO regulated?
changing both strength and rate of contraction
Frank-Starling's Law of the Heart
intrinsic ability to adjust output in response to changes in input; underlying mech is L-T relationship
Sympathetic activity results in?
increased rate and increased Ca concentration; more rapid and more forceful contractions of ventricles and increased stroke volume
How does norepinephrine increase the rate of relaxation?
increases Ca resequestration nto SR
Parasympathetic activity
decreases heart contractility; dominant under resting conditions
make thick filaments
thin filaments
composed of actin, tropomyosin, and troponin
wrap around each other to form double helix
lies on either side of each thin filament in groove formed by double strands of actin; extends length of 7 actin
3 subunit at end of each of each tropomyosin
Tropomysion associated
Ca binding
function of myosin crossbridges
slide thin filaments past thick filaments; shortening sarcomeres and overall muscle
resting potential of skeletal muscle
-90 mV
motor unit
collection of muscle fibers innervated by a single motor neuron
myoneural junction
specialized regions where axons of motor neurons end
motor end plate
area of muscle cell membrane in myoneural junction area
arrival of nerve AP results in?
release of ACh->binding of nictinic adrenergic receptors->end plate potential->propogated AP
Depolarization due to ACh receptor actication in result of?
highly localized increase in conductance of membrane to Na and K
one impulse in nerve gives rise to one impulse in muscle
What maintains refractory period after AP?
active Na pump
tranverse-tubule system
responsible for rapid inward conductance of electrical impulse; network of fine tubes
As t-tubules penetrate the fiber, they make contact with?
termination of SR longitudinal tubules
lateral sacs or terminal cisternae
t-tubules in contact with 2 terminal cisternae at level of Z line
final site where electrically controlled event in E-C coupling occurs
resting state of Tropomyosin
myosin heads cannot make contact with actin binding sites
During activation of tropomyosin
Calcium is made available from SR and binds TN C; this causes conformation change that TN I releases inhibition and allows tropomyosin to roll out of grooves in actin and expose actin binding sites to myosin
Reaction sequence
myosin+ATP=charged myosin intermediate; then interaction with actin; actin-myosin forms an ATPase system that splits ATP into ADP and Pi (energy liberating step); new ATP binds myosin forcing detachment
mechanical summation
when muscle is restimulated before it is completely relaxed and 2nd twitch adds to mechanical effect producing longer, stronger contraction
repeated stimulation producing fusion of individual twitches; state of continued contraction
What causes fatigue?
reversible depletion of ATP
continued rapid sequence of stimuli resulting in gradual decrease in max contractile force and progressively less relaxation in which muscle fails to react maximally before next stimulus becomes effective; result of muscle fatigue
motor unit summation
as strength of a stimulus is increased, more individual fibers are stimulated due to motor unit recruitment and strength of contraction of whole muscle is increased
constant force; e.g. object lifted upwards
same length; only force is generated; e.g. object is too heavy to be moved; no external shortening takes place
force continuously increases while motion continuously occurs e.g. pouring water out of a pitcher
negative work
force is constant while muscle is lengtrhening; e.g. descending stairs
Length-Tension Relationship (optimum length)
length at which max force can be produced
Force-Velocity Relationship
greater the load, lower the velocity; load so great that it can't be lifted then velocity is 0; no load, velocity is max
force x velocity
When is power maximal?
when force is about 1/3 power
cardiac muscle cells
shorter and smaller in diameter; arranged in branching network
Why do cardiac cells have same striated pattern as skeletal muscle?
same sarcomere and contractile apparatus structure
Automaticity is limited to specialized cells in
SA node, internodal pathways, other atrial sites, around AV node, and in Purkinje system
5 Phases of cardiac AP
0. initial rapid de or spike overshooting 0 potential by 20-30 1. inital rapid de returning TMP to 0 2. slow re 3. final re returning TMP to restin potential 4. rest TMP with gradual de towards threshold
Phases of ion conductance
Na Cl K in; K out; decrease in K conductance in pacemaker cells
Purposes of intercalated discs
1. structural attachment via desmosomes 2. relaying of impulses from one cell to the next via gap junctions
how individual cardiac cells transmit impulses across cell boundaries
max tension of cardiac muscle
1/3 to 1/2 of skeletal muscle
fight or flight
increased sympathetic outflow from ventral hypothalamus to cardioaccelatory center in medulla; increased NE; increased HR and contraction force
Cardiac muscle does not...?
tetanize or exhibit summation
Smooth muscle has
no organized sarcomere structure; but has thick and thin and intermediate filaments
Dense plaques
found in smooth muscle; located on sarcolemna
dense bodies
smooth muscle; scattered through cytoplasm
Multiunit smooth muscle
every single cell must have neuroreceptors for each cell to control
Single unit smooth muscle
gap junctions allow it to function as 1 cell

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