BSCI201 Exam 3 Daisy

Function of muscle

movement, maintenance of posture, joint stabilization, heat generation

What % energy useful as work?

40%

What is 60% energy used for?

Heat

How are dangerous heat lvls prevented?

Radiation of heat from skin and sweating

How is body temp increased

Solar radiation, reflected radiation, muscle heat production, conduction

How is body temp decreased?

Body radiation, convection, evaporation/sweat

Skeletal muscle tissue location

Attached to bones and skin

Skeletal muscle tissue characteristics

Striated

Skeletal muscle tissue function

Voluntary movement

Cardiac muscle tissue location

Only in heart

Cardiac muscle tissue characteristics

Striated, intercalated disks

Cardiac muscle tissue function

Involuntary movement

Smooth muscle tissue location

Walls of hollow organs (stomach, urinary bladder, airways)

Smooth muscle tissue characteristics

Not striated

Smooth muscle tissue function

Involuntary movement

Characteristics of muscle cells

contractility, excitability, conductivity, extensibility, elasticity

Contractility

Can shorten

Excitability

Can transduce chemical signal to electrical signal

Extensibility

Can extend

Elasticity

Can return to its original shape

Muscle organ components

Muscle tissue, fibrous CT, vascularized, innervated

Muscle tissue components

Cells, areolar CT

Fibrous CT in muscle organs

Dense regular CT, dense irregular CT

Vascularization of muscle organs

One artery, one nerve, one or more veins

Adult skeletal muscle growth

Cells grow by cellular hypertrophy (little hyperplasia, only via satellite cells)

What does the shape and fascicle orientation of the muscle affect?

Force, direction, and precision of muscle

What happens when sphincters contract

Close orifice

How can muscle be attached to bone?

Directly or indirectly (tendon)

What do fasciae (fibrous CT) determine

Compartments

Compartments function

Group functionally related muscles

Myofiber

Multinuclear muscle cell (many cells fused), made up of many myofibrils

How do myofiber grow

Hypertrophy, hyperplasia via satellite cells

Myofilaments

Thin and thick (myosin)

Thin filament in skeletal muscle

Actin + tropomyosin + troponin

What does on myofiber contain?

Many myofibrils

What does one myofibril contain?

Many myofilaments

Titin function

Connects myosin to Z disc and M line ("tug-of-war")

What is sarcomere made of?

Proteins

How do sarcomere grow

Transcription and translation control (from nucleus) growth by hypertrophy

Structural proteins function

Maintain sarcomere's structure

Contractile proteins function

Perform activity of shrinking the sarcomere

Regulatory proteins function

Regulate sarcomere's activity

Myosin head function

Bind actin and ATP

What is a "band" of sarcomere

Myosin

Actin's binding sites (BS)

Myosin BS (masked by tropomyosin if relaxed), tropomyosin BS, troponin BS

Tropomyosin's binding sites (BS)

Actin BS, troponin BS

What does troponin bind

Ca2+, tropomyosin, actin

What happens when Ca2+ binds troponin

Troponin conformation change, tropomyosin conformation change, unmask myosin BS on actin, myosin binds actin

Sources of ATP to support skeletal muscle contraction

Stored ATP, creatine phosphate (CP), anaerobic glycolysis + lactate formation, aerobic respiration

Stored ATP

Used first (5-15 sec), very limited, unstable

Creatine Phosphate (CP)

ATP produced from direct phosphorylation of ADP by CP using the enzyme Creatine Kinase (10 sec)

CP + ADP

(CK)-> ATP + creatine

Anaerobic glycolysis + lactate formation

30-60 sec, pyruvic acid -> lactic acid +ATP

Aerobic respiration

Produces the most ATP, requires O2

ATP use in skeletal muscle contraction

Activate myosin heads, cross bridge detachment, sequestration of calcium ions back into the sarcoplasmic reticulum for storage

What does myosin head activation enable?

Crossbridge attachment

What happens when muscle fiber is excited by neuron?

Ca2+ release, contraction (excitation-contraction coupling)

What is each muscle fiber associate with?

Neuron

Neuromuscular synapse mechanism

Action potential flows down axon to axon terminal, neurotransmitter fuses w/ presynaptic membrane and released to postsynaptic membrane, ligand gated channels, wave of depolarization

What causes depolarization?

Na+ entering cell

What causes repolarization?

K+ exiting cell

Myofibril

Made up of many sarcomeres

Sarcolemma

Cell membrane of muscle cell

Endomysium

Made up of myofibers

Perimysium

Surrounds fascicle

Epimysium

Surround muscle

A band

Anywhere in sarcomere a ssociated with the entire length of myosin, wherever myosin is

I band

Anywhere in sarcomere without myosin

H zone

Central region of sarcomere w/ myosin but no thin filament

M line

Set of proteins central to sarcomore to maintain myosin centrally

Titin

Springy protein that attaches myosin to z line at lvl of I band

Contracted sarcomere

I band, H zone shrinks; Z line, M line stay the same

1. Ca2+ is present 2. ATP is present

1. Free myosin-binding sites on actin 2. Myosin heads bind ATP

3. ATP -> ADP + Pi

Breaking bond releases energy which is stored, activates & tilts myosin head

Activated myosin head

Unstable, change in conformation allows binding, head is ready to launch/release

Myosin head release ADP + Pi

Power stroke, sliding filament

Once ADP + Pi released from myosin head

Myosin head can bind ATP again, allows detachment of myosin from actin

What would happen if Ca2+ not present

Tropomyosin would mask all binding sites

What would happen if ATP not present

Myosin head can't activate

Rigor mortis

Just enough stored ATP to tilt myosin head and start contraction, but not enough to detach and relax again

Shortening of sarcomere

Shortening of myofiber cell and thus shortening of muscle organ

At what point is ATP required for muscle contraction

Tilt myosin head, release myosin from actin (detach cross bridge)

When skeletal muscle is at optimal resting length

Greatest capacity of cross bridging possible between actin and myosin, greatest amount of force

When H zone starts disappearing during contraction

Actins start physically hindering each other, harder to shorten sarcomere

What is minimum sarcomere size determined by

Once Z disk/titins are budding against myosin

When sarcomere extends

Less capacity to build myosin and actin cross bridge, harder to create force

Sarcoplasmic Reticulum

Specialized ER of muscle cell

Sarcoplasmic reticulum location

Surrounds each myofibril

Sarcoplasmic Reticulum function

Sac that contains large amt of Ca2+

T Tubule

Cell membrane invagination, part of sarcolemma, associated w/ cisternae

Ligand gated ion channel function

Allows for Na+ and K+ to flow

What is the ligand of the ligand gated ion channel

Neurotransmitter

Distribution of ion flow in ligand gated ion channel

Allows more Na+ to flow than k+

What direction does Na+ flow

In the cell

What direction does K+ flow

Out the cell

What is the result of increased Na+ ions in the cell

Membrane charge becomes less negative, depolarization, allows voltage gated Na+ channels to open

Voltage gated ion channel

Allows ions to flow based on the membrane voltage/ membrane potential

Result of voltage gated Na+ channel opening

Na+ flows in the cell, more depolarization

When does depolarization stop

Once past 0 membrane potential (mV)

How does depolarization stop

Na+ channels close