Human Phys Midterm 2

Types of muscle

skeletal, cardiac, smooth

skeletal muscle appearance

striated & cylindrical

skeletal muscle action

voluntary

skeletal muscle location

attached to bone

why would muscle cells be multinucleate

makes repair easier and more efficient

skeletal muscle functions

produce body movements, stabilize body positions, generate heat

skeletal muscle properties

electrical excitability, contractility, extensibility

electrical excitability

ability to respond to stimuli by producing action potentials

skeletal muscles control

somatic nervous system

whole muscle

bundle of muscle fascicles

muscle fascicle

bundle of muscle fibers (muscle cells)

muscle fibers

a muscle cell, cytoplasmic space filled with myofibrils

myofibrils

contractile element composed of sarcomeres linked end-to-end

sarcomeres

contractile subunit with overlapping thick and thin filaments

myosin

thick filament, ATP driven molecular motor for muscle contraction

actin

thin filament, directly attached to Z line, produces the track that myosin moves along

each myosin filaments is surrounded by

6 actin filaments in hexagon shape

each actin filament is surrounded by

3 myosin filaments, hexagonal

organization of skeletal muscle is almost

crystalline

Tropomyosin

blocks myosin binding sites during relaxation, located on actin, moves during muscle contraction, 7 actin subunits per Tm molecule

Troponin

3 subunit complex on thin filament, locks tropomyosin in place when muscle is relaxed, calcium sensor that triggers muscle contraction

Titin

spring like protein linking myosin filaments to z-line

Alpha actinin

creates a mesh-like network that anchors titin filaments and actin thin filaments in I-band

Myomesin & M-protein

major protein components of M-line, creates network that links thick filaments of A band

T-tubules

passages through muscle cytoplasm that encircle myofibrils

Sarcoplasmic Reticulum

encircling myofibrils, specialized endoplasmic reticulum found in muscle that contains very high concentration of calcium

NMJ pre-synaptic terminal

neuronal axon terminal

NMJ post-synaptic target

Motor end plate: specialized region of skeletal muscle membrane

End plate potential

local depolarization of muscle due to acetylcholine, triggers action potential if EPP exceeds threshold

Dihydropyridine receptor DHPR

L-type voltage-gated calcium channel family, found in T tubule membrane, moves in response to action potentials

Ryanodine receptor (RyR)

calcium release channel, found in SR membrane, opens to release Ca2+ when DHP receptor moves

SR Calcium-ATPase

found in SR membrane, pumps Ca2+ from cytoplasm in SR against its concentration gradient

Function of Ca2+ in cross-bridge formation

when calcium concentration is high, tropomyosin moves and cross-bridging occurs

contraction of skeletal muscle fibers

myosin pulls on thin filaments, width of A band does not change, I band gets narrow, individual lengths of thick and thin filaments do not change, Z-discs get closer and sarcomere shortening

sarcomere shortening leads to

myofibril shortening and whole muscle shortening

relaxed muscle

in absence of calcium, myosin binds and hydrolyzes ATP, generates ADP and phosphate

Contraction cycle steps

ATP hydrolysis, Attachment of myosin to actin, Power stroke, detachment of myosin from actin

ATP hydrolysis

myosin is energized and perpendicular to thin filament, ADP and phosphate still attached

Attachment of myosin to actin

myosin head attached to binding site of actin, phosphate group is released, crossbridge

Power stroke

myosin head pivots and pulls thin filament toward center of sarcomere, ADP released

Detachment of myosin from actin

crossbridge remains attached to actin until it binds another ATP, then myosin heads detach

Calcium

pumped back into sarcoplasmic reticulum to cause relaxation

isometric contraction

not allowing muscle to shorten much, measures tension, shorter latent period, slower

lengthening contraction

muscle generates tension but lengthens as well

Isotonic contraction

shortening muscle, longer latent period, quicker

Creatine Kinase

one step reaction, transfer phosphate from Creatine-phosphate to ADP to make ATP, a

Glycolysis

multistep reaction, anaerobic, converts 1 glucose to 2 ATP, slow

Oxidative Phosphorylation

Multistep reaction, requires oxygen and mitochondria, converts 1 glucose to 36 ATP, converts fatty acids to ATP, converts amino acids to ATP, slower

Creatine phosphate provides reservoir of

high energy phosphate that is accumulated during rest in muscle cells

Creatine kinase provides ATP during

first few seconds of a contraction

ATP production is rapid but

limited by the amount of creatine phosphate stored in cell, very short periods of muscle activity

Glycolysis anaerobic

can produce ATP from glucose in absence of oxygen, kicks in during high intensity exercise

Glycolysis produces

2 ATP, 2 pyruvic acid, 2 lactic acid (due to insufficient O2 levels)

Oxidative phosphorylation powers

extended muscle activity

Muscle fiber types are classified according to

maximal velocity of shortening (how quickly myosin can hydrolyze ATP), major pathway they use to form ATP

Slow-oxidative fibers cell types

red muscle/small diameter cells, Type 1

Slow-oxidative fibers tension

slow myosin so tension development is slow, less tension

Slow-oxidative fibers metabolism

anaerobic, mostly oxidative phosphorylation requiring O2, many mitochondria and capillaries provide oxygen, large amounts of myoglobin aid in oxygen diffusion and store oxygen, resistant to fatigue

Fast-oxidative glycolytic fiber muscles

red muscle/intermediate diameter cells, fast myosin, aerobic and anaerobic metabolism, Type 2a, use oxidative phosphorylation and glycolysis

Fast-oxidative glycolytic fiber tension

larger diameter = more tension, fast myosin ATPase to tension development is faster, mostly oxidative phosphorylation but also glycolysis, less myoglobin than slow-oxidative, somewhat resistant to fatigue, less capillaries

Fast-glycolytic fiber cells

white muscle

Fast-glycolytic fiber tension

larger diameter = more tension, fast myosin ATPase

Fast-glycolytic fiber metabolism

mostly glycolytic that doesn’t depend on oxygen, large amounts of glycogen for fuel, fewer capillaries and mitochondria, prone to fatique, no myoglobin

recruitment

adding motor units to match force required

what happens during fatigue

not an absence of ATP, high EC K+ concentration, lactic acid build up, build up of ADP, calcium regulation disruption

what factors affect how much tension a whole muscle produces

number of active motor units, number of muscle fibers per unit, fiber types of activated units

tension development depends on

overlap of thick and thin filaments

if isometric contraction is initiated

only myosin crossbridges in region of thick filament that overlap thin filament can participate in tension development

isometric force depends on

sarcomere length

highest level of motor control

planning, memory, emotions, motivations

middle level motor control

cross-talk between sensory inputs regulates modes of movement including fine motor, includes brainstem, thalamus, cerebellum

muscle spindles

embedded in muscle groups of body, stretch and contract as groups change length, central non-contractile region flanked by contractile end regions

isotonic contraction of muscles slows

rate of action potentials

reflex arc stimulus

muscle stretch

reflex arc receptor/sensor

muscle spindle

reflex arc afferent

spindle afferent

reflex arc integration center

spinal cord

reflex arc efferent

motor neuron

reflex arc effector

muscle

reflex arc response

muscle contraction

golgi tendon organs

sensory afferents embedded in connective tissue where muscle tendons attach to bones,

pain withdrawal reflex

causes flexion of a limb, contraction of more than one muscle group, motor unit communication facilitated by spinal interneurons

smooth muscle cytosolic Ca2+

tension determined by Ca2+ amount, graded, can come from ECF or ICF, SR here does not have much calcium

cardiovascular system role in homeostasis

temperature regulation, main transport system for nutrients/wastes

heart

electrical event (action potential) followed by mechanical event (contraction)

total volume of blood is

5.5 L

plasma averages

55-58% of blood volume and is apart of ECF

buffy coat

leukocytes and platelets

erythrocytes

hematocrit, mainly gas transport, 42-45% of blood volume

Ischemia

low of oxygen/blood flow

pressure in systemic (body circuit)

is much higher than pulmonary (lung) circuit

pulmonary circuit is arranged

in series

systemic circuit is arranged

in parallel, less resistance

Parallel vs Series arrangement

same quality of blood to all tissues, allows for better regulation of blood flow, takes less pressure than arranged in series

Cholinergic receptors

Muscarinic Acetylcholine Receptor (mAChR)

Adrenergic receptors

alpha and beta

greater resistance

less flow, impacted by vessel length, blood viscosity, and radius of vessel^4

atrioventricular valves

right AV (tricuspid) and left AV (bicuspid)

semilunar valves

pulmonary semilunar valve and aortic semilunar valve

endocardium

inner most layer of heart, separates chambers from heart muscle