Studied by 1 personSkeletal 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
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