Physiology Exam 3

Skeletal muscle functions

produce movement, maintain homeostasis, and generate heat

Muscle fiber

single muscle cell

Myofibril

contractile unit that runs the length of the muscle fiber

Myofilaments

thin and thick proteins within the myofibrils

Sarcomere

functional unit and smallest component of muscle fiber that can contract

A band

thick and thin filaments overlap

M line

proteins anchor thick filaments together

Z disc/line

line between 2 sarcomeres

Titin

allows for elastic recoil

Tropomyosin

covers actin cross bridge binding sites

Troponin

regulates tropomyosin position which regulates muscle contraction

Transverse tubule (T-tubule)

membrane that aids in spreading of signal

Sarcoplasmic reticulum

membranous network that contains stored Ca2+ ions that when released allows myosin-actin binding

What are the 3 mechanisms that require ATP?

* Actin-myosin binding for power stroke
* Unbinding of actin and myosin after power stroke
* Transport of Ca2+ back to sarcoplasmic reticulum

Tendons

noncontractile tissues that attach to bone

Origin of a tendon

attachment that doesn’t move

Insertion of a tendon

attachment that does/can move

Isotonic

tension is constant while muscle length changes and tension on insertion is greater than opposing force

Concentric contraction

muscle shortens (bicep curl)

Eccentric contraction

muscle lengthens (lowering weight from biceps curl)

Isometric

tension develops at constant muscle length and tension on insertion is equal to the opposing force

Twitch

a single action potential in a muscle fiber which isn’t strong enough to produce movement on its own

What is muscle tension determined by?

* Number of contracting muscle fibers
* Resulting tension of each contracting fiber
* Frequency of stimulation
* Initial fiber at rest

Twitch summation

continued excitation of fibers

Tetanus

no muscle relaxation between stimuli (stronger contraction)

Smooth muscle

involuntary, lines hollow organs and tubes, stimulated by ca2+ concentration

What are the 2-types of smooth muscle?

multi-unit and single-unit

Multi-unit

contracts as smaller independent units stimulated by nerves

Single-unit

contract a single, coordinated unit (functional syncytium)

Cardiac muscle

line heart, branches interconnected cells (gap junctions)

What are the 3 parts of the circulatory system?

the heart, blood vessels, and blood

Transportation in systemic circuit

* Respiratory system - oxygen
* Digestive system - nutrients
* Excretion - products not needed by the body

Regulation in the systemic circuit

* Hormonal - from site of origin to target tissue
* Temperature - vasodilation (release) and vasoconstriction (retention)

Protection of systemic circuit

* clotting - protects against blood loss
* immune - protects against pathogens

What is the blood flow through the heart?

Vena cava - right atrium - right ventricle - pulmonary artery - lungs - pulmonary veins - left atrium - left ventricle - aorta - system circuit

Pressure in pulmonary side of heart

low pressure, low resistance

Pressure in systemic side of the heart

high pressure, high resistance

Atrioventricular valves (AV)

between the atria and ventricles which close when ventricles empty (lub sound)

Semilunar valves

Between ventricles and arteries which closes when ventricles fill (dub sound)

What is the direction in which blood moves?

veins - atria - ventricles - arteries

What are the 2 specialized cardiac muscle cell types?

autorhythmic and contractile cells

Autorhythmic cells

initiate and conduct action potentials (don’t contract)

Contractile cells

are stimulated by autorhythmic activity and do the mechanical work for pumping

Sinoatrial node (SA node)

acts as the pacemaker of the heart

What are the 3 waveforms of an EKG?

p wave, qrs complex, and t wave

Systole

contraction and emptying, spread of excitation

Diastole

relaxation and filling, repolarization time

Cardiac output

blood pumped by each ventricle per minute and regulation depends on stroke volume and cardiac rate

Stroke volume

volume of blood pumped by each ventricle per beat

How does the parasympathetic division regulate the cardiac rate?

mostly innervates atria and modifies the pace

How does the sympathetic division regulate the cardiac rate?

innervates atria and ventricles which modifies the pace and contraction strength

Intrinsic control of stroke volume

cardiac muscle rests at less than optimal length for greater muscle fiber stretching and venous return

Frank-Starling law of the heart

in systole the heart will eject the volume of blood returned during diastole

Extrinsic control of stroke volume

causes vasodilation which results in a greater venous return

Arteries and arterioles

transport blood from heart to organs

Arteries

act as pressure reservoir (builds extra pressure)

Arterioles

branches from arteries to organs

capillaries

branched capillary beds which are sites of exchange between blood and surrounding organ tissue

Veins and venules

return blood from organs to heart

Venules

branch from organs

Large veins

act as blood reservoir

Artery and arteriole vessel anatomy

relatively thick smooth muscle, arteries have elastin fibers

Capillary vessel anatomy

only endothelial lining so it’s easier to exchange molecules

Vein and venule vessel anatomy

relatively thin smooth muscle and contain venous valves

Flow rate

volume of blood pumped at a given time and is the same throughout the system

What does adequate flow depend on?

pressure gradient and vascular resistance

Pressure gradient

pressure difference from the beginning to end of vessel

Resistance

opposition to flow through a vessel or the friction of moving liquid against stationary vessel walls

Viscosity

friction of fluid molecules against each other (not usually a huge factor)

Vessel length

overall surface area of vessel (greater length = greater SA = greater resistance)

Vessel diamter

more surface area for fluid to contact = greater resistance

Mean arterial pressure (MAP)

average pressure driving blood forward during cardiac cycle

Vasoconstriction

narrowing of vessel diameter which increases resistance and decreases flow

Vasodilation

widening of vessel diameter which decreases resistance and increases flow

Total peripheral resistance (TPR)

total resistance by all systemic vessels

Afterload

opposing pressure on ventricles during ejection (leftover blood in ventricles) which can reduce stroke volume

Blood pressure

force exerted on blood by vessel walls

What is the average systolic pressure?

120 mm Hg

What is the average diastolic pressure?

80 mm Hg

What are the factors affecting blood pressure?

cardiac output, total peripheral resistance, and blood volume

What is venous return influenced by?

arterial pressure, skeletal muscle pumps, sympathetic activity, respiratory activity, and blood volume

What happens if MAP raises above normal?

sympathetic activity decreases, promotes vasodilation, and lowers blood pressure

What happens if MAP falls below normal?

less blood volume delivered to arterioles and arterioles dilate which increase flow to capillaries

Blood/plasma volume

volume of blood in circulatory system

Hydrostatic pressure

pressure of any fluid enclosed in a space

Capillary hydrostatic pressure

exerted by blood on capillary wall

Interstitial fluid hydrostatic pressure

exerted by interstitial fluid on capillaries

Osmotic colloid (oncotic) pressure

from proteins that displace water

Plasma colloid osmotic pressure

plasma proteins create concentration difference

What happens during ultrafication?

* higher capillary hydrostatic pressure
* lower interstitial fluid hydrostatic pressure
* lower plasma-colloid osmotic pressure

What happens during reabsorption?

* lower capillary hydrostatic pressure
* higher interstitial fluid hydrostatic pressure
* higher plasma colloid osmotic pressure

Hypertension

high blood pressure (above 140/90mm Hg)

Hypotension

low blood pressure (below 100/60mm Hg)

Secondary hypertension

high blood pressure caused by other factors (like loss of elastin fibers in the heart)

Primary hypertension

unknown cause but is often underlying genetic tendency which is exacerbated by diabetes, smoking, etc

Orthostatic hypertension

the inability to respond to affect of gravity on venous return (happens in bedridden people)

What is the first step of external respiration?

ventilation or gas exchange between the atmosphere and air sacs (alveoli) in the lungs

What is the second step of external respiration?

exchange of O2 and CO2 between air in the alveoli and the blood in the pulmonary capillaries

What is the third step of external respiration?

transport of O2 and CO2 by the blood between the lungs and the tissues

What is the fourth step of external respiration?

exchange of O2 and CO2 between the blood in the systemic capillaries and the tissue cells