Muscle Structure & Function - Tissue Mechanics

what is the functional unit of a muscle?

sarcomere

what is the correct order for muscle organization from outermost to innermost?

epimysium → muscle → perimysium → fascicles → endomysium → muscle fibers → myofibrils → thick & think filaments

muscle fibers are the _____ in muscle

cells

muscle fibers (cells) are ___________

multinucleated

in mature muscle fibers, nuclei are located at the _____

end

in new muscle fibers, nuclei are located at the ______

middle

what are the connective tissue layers of muscle?

epimysium, perimysium, endomysium

epimysium surrounds the ____________

entire muscle

what do the connective tissues of muscle do?

give muscle most of its mechanical properties

Epimysium contains ______________ making it resistant to stretch

abundance of collagen

perimysium surrounds the ___________

muscle fascicles

_______ and _______ lie within the perimysium

blood vessels and nerves

endomysium surround the ___________

individual muscle fibers

endomysium lies just outside the _________

sarcolemma

what is the sarcolemma?

the plasma membrane of the muscle cell

exchange between ________ and _______ happens in the endomysium

capillaries and muscle fibers

what is the basal lamina?

scaffolding that surrounds the muscle cell (the most inner part of muscle cell)

Where are satellite cells located?

the outside of the basal lamina

when satellite cells are called upon, they _______

divide into daughter cells

what happens to the daughter satellite cells after they divide?

one enters the muscle, one remains on outside

where do muscles get their source of energy?

mitochondria

what kind of metabolism do mitochondria use?

aerobic metabolism

what do mitochondria generate?

ATP

what else generates ATP besides mitochondria?

cytoplasm

how does cytoplasm generate ATP?

anaerobic glycolysis

energy (ATP) created through Kreb’s cycle, ETC is used for _____

muscle contraction

______ and ______ give muscle its striated appearance

actin and myosin

midline region of the sarcomere, only contains myosin

H zone

mid part of myosin

M line

M-line is contained in the______

H zone

Located between sarcomeres & changes shape during muscle contraction, only contain actin

I band

_______ is included in the I band

Z line

where there is overlap between actin and myosin, stays the same shape during muscle contraction

A band

defines the boundary between sarcomeres

z line

the sarcomere extends from ______ to _______

z-line to z-line

what are the contractile proteins of muscle

actin & myosin

actin is the ______ filament

thin

myosin is the _____ filament

thick

_____ binds with myosin to generate force and shorten the sarcomere

actin

what stabilizes the actin filament

tropomyosin

what influences the position of tropomyosin

troponin

what does the troponin/tropomyosin complex cover up at rest? (no calcium)

the binding site of myosin

myosin consists of a ______ chain & ______ chain

heavy & light

______ chain is the molecular motor for muscle contraction

heavy chain

_______ chain influences the contraction velocity of the sarcomere

light chain

what are the limiting factors of a muscle contraction?

ATP and Calcium

what are some structural proteins of muscle?

Titin, Nebulin, Dystrophin

Protein that is large in size & stabilizes muscle cell, giving shape and form

Dystrophin

Protein that gives integrity to a muscle

Nebulin

Protein that is important in creating passive tension in a muscle

Titin

Protein that stabilizes the alignment of adjacent sarcomeres

Desmin

Titin & Desmin are both ______________ proteins and help keep muscle fibers relatively the same length

non-contractile

3 general characteristics of non-contractile proteins

1. generate passive tension when stretched

2. provide internal and external support and alignment of muscle fibers

3. help transfer the active force of the muscle

Titin bears most of the _________ load in muscle

passive

Titin serves as a _______ for chronic changes in muscle length or force changes

sensor

Titin is a _______ molecule filament

single

the ___________ is what gets depolarized in an AP

sarcoplasmic reticulum

the _________ are extensions of the sarcoplasmic reticulum

T tubules

what ‘lives’ in the T tubules?

Calcium

what is the function of T tubules?

they allow AP to be dispersed quickly

muscle is a _______ tissue

excitable

________ ligand channels only open when a particular chemical neurotransmitter fits into a very specific receptor (ex. sodium)

chemical dependent

_____ ligand channels open only when the charge different across the membrane becomes -50 mV

voltage dependent

_______ channels open when specific chemical neurotransmitter fits into a receptor on the outside of the membrane OR when the inside voltage reaches +30 mV

potassium

what is the resting potential of muscle?

-70 mV

what occurs in depolarization of muscle

AP comes in contact with SR

what is the value of the action potential

+30 mV

what does repolarization mean?

when muscle returns back to its resting potential

what does hyperpolarization mean?

the AP overshoots its target, then comes back