PLTW HBS - Muscle (1.2.1 -> 1.2.3)

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Describe what striated means in terms of muscle.

Muscle marked with long, thin parallel streaks

Describe what it means if a muscle is under voluntary control. Add an example. What muscle tissue(s) have voluntary control?

A muscle contracts with you consciously controlling it; ex. biceps; skeletal muscle

Describe what it means if a muscle is under involuntary control. Add an example. What muscle tissue(s) have involuntary control?

A muscle contracts without you consciously controlling it; ex. heart; smooth muscle and cardiac muscle

Describe Skeletal Muscle under a microscope

Very straight; no overlapping; nuclei are on sides of fibers; lots of striations

Describe Cardiac Muscle under a microscope

Fibers can connect; looks like branching trees

Describe Smooth Muscle under a microscope

Looks wavy; less defined; no striations

Skeletal Muscle: Is it striated? Voluntary? Location in body? Function in body?

Yes. Yes. Attached to bones. To produce movement; maintain posture and body position; generate heat

Smooth Muscle: Is it striated? Voluntary? Location in body? Function in body?

No. No. Inside walls of organs. Moves substances through the body; contracting; regulate size of passageways

Cardiac Muscle: Is it striated? Voluntary? Location in body? Function in body?

Yes; no; heart; to beat

Sliding Filament Theory (Simple definition)

The explanation of how muscles contract; myosin heads pull on actin filaments, causing them to slide toward the center of the sarcomere and shorten (contract) the muscle

Actin

A thin protein filament in muscle fibers; the track that myosin pulls on during contraction

Myosin

A thick protein filament with “heads” that bind to actin and pull to create movement

Tendon

A tough, fibrous connective tissue that attaches muscle to bone

Ligament

A connective tissue that attaches bone to bone at joints

Myofibril

Thread-like structures inside a muscle cell made of repeating sarcomeres. Contains actin and myosin

Muscle Cell

A long, cylindrical cell filled with myofibrils; contracts when stimulated

Fascicle

A bundle of muscle fibers grouped together

Epimysium

The outermost connective tissue layer surrounding the entire muscle

Perimysium

The connective tissue surrounding each fascicle

Endomysium

The connective tissue surrounding each individual muscle fiber

Sarcomere

The functional contractile unit of a muscle made of actin and myosin arranged in a repeated pattern

Neuron

A nerve cell that sends and receives electrical signals

Neurotransmitter

A chemical messenger released by neurons to send signals across synapses

Acetylcholine (ACh)

The neurotransmitter released at the neuromuscular junction to start a muscle contraction

Action Potential

An electrical impulse that travels along the neuron or muscle membrane, triggering contraction

T-tubule (Transverse Tubule)

Tiny tubes in muscle fibers that carry the action potential deep into the cell

Synapsis (Synapse)

The tiny gap between a neuron and the cell it communicates with

Troponin

A regulatory protein on actin that moves when calcium binds to it, allowing myosin to attach

Tropomyosin

A protein that blocks the myosin-binding site on actin until troponin shifts it

Neuromuscular Junction (NMJ)

The connection between a motor neuron and a muscle fiber where acetylcholine is released

Sarcolemma

The cell membrane of a muscle fiber

ATP

The energy molecule used in three key steps of contraction: Energizing myosin heads; Releasing myosin from actin; Pumping calcium back into the sarcoplasmic reticulum to end contraction

Describe the events that take place from the time you decide to move a muscle to your muscle contracting.

When your brain wants to move a muscle it sends an Action Potential signal down the spinal cord via neurons and goes to neurotransmitters called Acetylcholine (ACH), through a gap called the synapse to the sarcolemma t-tubule. Calcium gets called by the myosin to distract the tropomyosin and troponin, which are wrapped around actin to protect it from myosin. After they get distracted, myosin pulls actin together to contract the muscle.

Summary of Sliding Filament Theory

Myosin wants to grab actin, but it is usually protected by tropomyosin and troponin. They are easily distracted by calcium. When they get distracted by calcium, myosin can grab actin and pull it in (contracting). In order for myosin to release actin, and to “reset”, ATP is needed.

Origin

End of muscle that is attached to a bone that stays still during movement

Insertion

End of muscle that is attached to the bone that moves when the muscle contracts

Flexors; Think of an example

Muscles that decrease the angle between two bones; They bend a joint; Example: Biceps bending the elbow

Extensors; Think of an example

Muscles that increase the angle between two bones; They straighten a joint; Example: Triceps straightening the elbow

Prime Mover

The main muscle responsible for producing a specific movement; Does most of the work

Synergist

A muscle that assists the prime mover; Helps make the movement more stable or efficient

Antagonist; Think of an example

A muscle that opposes or reverses the action of the prime mover; Relaxes while the prime mover contracts; Example: Triceps is the antagonist when the biceps flex the arm

Contracting Muscle vs. Relaxing Muscle

A muscle is contracting when it is actively shortening or tightening to produce movement or maintain posture; A muscle is relaxing when it stops contracting and lengthens, allowing the opposite movement to occur.

What are the 7 ways that muscles are named?

Location, shape, size, direction of muscle fibers, # of origins, location of attachments, and action

6 rules of building muscles

1: Muscles have at least two points of attachment; Muscles cross at least one join. 2: Muscles shorten as they contract; Muscles can only pull. 3: Muscles have an origin and an insertion. 4: Flexion at a joint. 5: There must be prime movers, antagonists, and synergists. 6: Muscle fibers go in the direction of the pull of the muscle; do not put striations on tendons

Fill out this chart on a piece of paper and check answers. (Works best for flashcards)

Answers

Study the diagrams you buffoon

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