Agr 282: Muscular System

contractile muscle

What type of tissue is muscle?

highly vascularized

How is muscle tissue supplied with blood?

muscle

What does "myo" mean?

muscle

What does "sarco" mean?

muscle layer of the uterus

What is myometrium?

plasma membrane of a muscle cell

What is sarcolemma?

Channels that respond to changes in electrical signals/voltage across the membrane

What are voltage-gated channels?

the channel opens or closes

What happens when a voltage-gated channel detects a change in membrane charge?

closed as the electrical charge opens them up

What is the rested state of the membrane channel in voltage gated?

facilitated diffusion

What type of diffusion is voltage-gated?

channels that respond to a chemical signal (ligand)

What are ligand-gated channels?

hormones or neurotransmitters

What can act as a ligand?

it causes a conformational change that opens or closes the channel

What happens when a ligand binds to a receptor on a channel?

the channel is closed

What happens when the ligand is not binding?

stabilizing joints, producing heat, producing movement, maintain posture

What are the four main functions of muscle?

muscle contractions help hold joints in place

How do muscles stabilize joints?

muscle contractions, such as shivering, produce heat

How do muscles produce heat?

movement

What does muscle contraction produce?

facial expressions, locomotion, and movement of fluids in the body

What are examples of movement produced by muscle?

continuous muscle contractions help keep the body in position

How do muscles help maintain posture?

excitability, contractility, extensibility, elasticity

What are the properties of muscles that give them their function?

excitability

What is the property described as: the ability to maintain a membrane potential and have electrical (charge) differences on the inside and outside of a cell

contractibility

What is the property described as: the stimulated potential can cause the muscle cell/muscle to contract

muscle cells can shorten in length

What can muscle cells do because of contractility?

extensibility

What is the property described as: the ability of muscles to stretch, can lengthen in response to stretch, some stretch while others relax

elasticity

What is the property described as: if stretched, muscles can return to their normal size/shape due to elasticity, returning back to normal length

striated and non-straited

What are the two types of muscle?

shortens

What does striated mean?

contracts in all dimensions

What does non-striated mean?

it has bands (on microscope)

How does striated muscle look?

voluntary control over contractions

What is skeletal muscle?

involuntary contractions over contractions

What is cardiac muscle?

involuntary control over contractions

What is non-striated muscle?

non-striated muscle, involuntary control over contraction

What is smooth muscle?

muscle layers in stomach, intestines

What are examples of smooth muscle?

biceps, gluteus maximus

What are examples of skeletal muscle?

heart

What are examples of cardiac muscles?

muscle, muscle fascicle, muscle fiber/cell, myofibrils

What is the organization of skeletal muscle from superficial to deep?

connective tissue (epimysium)

What covers the whole muscle?

a bundle of muscle fibers

What is a muscle fascicle?

connective tissue: perimysium

What covers the muscle fascicle?

a muscle cell (myofiber)

What is a muscle fiber?

connective tissue: endomysium

What covers a muscle fiber?

structures found inside muscle fibers

What are myofibrils?

they can run the length of a muscle

How long can muscle fibers be?

having many nuclei

What does multinucleated mean in relation to skeletal muscle?

around outside of the cell, beneath the sarcolemma

Where are the nuclei located in skeletal muscle fbers?

by the fusion of small muscle cells called myoblasts

How are muscle fibers formed?

they become satellite cells

What happens to unfused myoblasts?

no, muscle fibers cannot divide

Can muscle fibers divide?

divide and fuse with muscle fibers if they are damaged

What can satellite cells do?

a protein similar to hemoglobin that stores oxygen

What is myoglobin?

to produce energy

Why do muscle fibers have abundant mitochondria?

throughout the cell, including along the outer edge

Where are many mitochondria located in muscle fibers?

The charge caused by the unequal distribution of ions across a cell membrane

What is membrane potential?

it is needed for signal transduction and must transmit quickly and evenly for muscle contraction

Why is membrane potential important?

small tubes that run perpendicular to the sarcolemma and extend deep into the sarcolemma

What are transverse tubules?

they transmit charges in membrane potential into the muscle fiber

What is the function of T-tubules?

end sacs of the sarcoplasmic reticulum

What are terminal cisternae?

it actively pumps calcium into the SR, keep calcium low in the sarcoplasm and high in the SR

What does the SR do with calcium?

two terminal cisternae and one T-tubule

What makes up a triad?

the bulk of the muscle fiber consists of bundles of myofilaments

What are myofibrils?

The functional unit of skeletal muscle

What is a sacromere?

bundles of myofilaments

What are myofibrils made of?

the organized arrangement of myofilaments within sarcomeres

What gives skeletal muscle its striations?

sarcomeres

What is the functional unit of skeletal muscle?

contractile, structural, and regulatory proteins

What are the three types of proteins in a sarcomere?

Actin and Myosin

What are the two main contractile proteins?

thin filament; associated with the light band

What type of filament is actin?

thick filament; associated with the dark band

What type of filament is myosin?

thousands

How many sarcomeres does one myofibril have?

the portion of a sarcomere containing thick filaments (myosin)

What is an A band?

the portion of a sarcomere with no myosin; present when relaxed

What is an I band?

the portion of a sarcomere with no actin; present when relaxed

What is the H zone?

cross-linked actin proteins that anchor thin filaments

What are Z discs?

a spring-like protein connecting myosin to Z discs

What is titin?

elasticity

What does titin provide to muscle?

the distance from one Z disc to the next Z disc

What defines on sarcomere?

two strands of F actin (filamentous actin)

What is actin made of?

a double-stranded helix, like DNA

What shape do the two F-actin strands form?

G-actin (globular actin)

What makes up each F-actin strand?

a regulatory protein that wraps around F actin

What is tropomyosin?

blocks myosin-binding sites and prevents contraction

What does tropomyosin do at rest?

a globular regulatory protein with three subunits

What is troponin?

tropomyosin

what does troponin T (TnT) bind to?

F actin

What does Troponin I (TnI) bind to?

calcium

What does Troponin C (TnC) bind to?

the bulk of the thick filament

What do myosin tails form?

only myosin tails

What is found in the H zone?

globular proteins that project toward the actin filaments

What are myosin heads?

ATPase activity

What activity does myosin heads have?

hydrolyzes ATP to use its energy

What does ATPase do?

actin filaments

What do myosin heads bind to?

the hinge/neck

What connects to myosin head and tail?

the head to pivot

What does the myosin hinge/neck allow?

somatic nerves called motor neurons

What controls skeletal muscle?

extensions from motor neurons that send signals to muscle tissue

What are axons?

at neuromuscular junctions

Where do motor neurons signals each the muscle?

each muscle fiber is innervated by a neuron

What is true about muscle fiber innervation?

yes, a single neuron may innervate multiple fiber

Can one neuron control multiple muscle fibers?