The Muscular System

tendon

strip of strong connective tissue that connects a muscle to bone.

define voluntary muscles

voluntary muscles are the muscles under your control.

3 types of muscles

The three types of muscles are skeletal muscle, smooth muscle, and cardiac muscle.

Why are skeletal muscles called striated muscles?

Skeletal muscles appear to be striped, or striated, under a microscope.

Explain how the bicep and tricep work together to allow you to bend your arm.

The bicep contracts and the tricep relaxes when you bend your arm toward your head. When your arm returns to the position parallel to the floor, the bicep relaxes while the tricep contracts. These muscles work together to allow you to move your arm.

What determines the strength or weakness of a muscle contraction? Explain how this is related to the ability to lift heavy or light objects.

The number of muscled fibers involved determines the strength or weakness of a muscle contraction. To lift a heavy object, the nervous system signals more muscle fibers to contract that a when lifting a lighter object.

How do muscles produce force?

Muscles produce force by contracting.

What two proteins does ATP interact with to produce muscle contraction?

ATP interacts with myosin and actin to produce muscle contractions.

Why does every movements require two muscles?

Muscle contraction can only produce a pulling motion, not a pushing motion. Therefore, muscles must work in pairs to produce movement.

What is myofibril?

A myofibril is a bundle of thick and thin filaments that make up muscle fibers.

What gives skeletal muscle is striated appearance?

The alternating thick and thin filaments in myofibrils give skeletal muscles their striped appearance.

What is a sarcomere? Use the term Z line in your answer?

A sarcomere is a unit of thick and thin filaments bound on Z lines

What is the neuromuscular junction? What occurs at a neuromuscular junction?

A neuromuscular junction is a specialized area in which a nerve fiber lies close to the end of a muscle fiber. When a nerve impulse reaches the end of a motor neuron, it triggers the release of acetylcholine. Acetylcholine diffuses across the neuromuscular junction and produces and impulse in the muscle fiber, causing the release of calcium ions within the fiber and producing a muscle contraction.

What causes a muscle to relax?

A muscle relaxes when acetylcholine is not longer produced and the calcium ions have been pumped back into storage.

Do filaments change length when a muscle contracts? Explain what happens to the filaments during a muscle contraction.

No. According to the sliding-filament model, the filaments do not change in the length. Instead, muscles shorten when the thin filaments slider over the think ones. During a muscle contraction, a cross-bridge physically links the myosin and actin filaments. With the help of ATP, the cross-bridge changes shape so that the filaments slide past each other, producing a shortening, or contraction, of the muscle fibers.

define involuntary muscles

muscles you cannot/do not need to control, like digestive and cardiac muscle

where is skeletal muscle found + voluntary or involuntary?

voluntary muscles attach to bones that allow us to move, voluntary

location of cardiac muscle + voluntary?

found ONLY in heart, involuntary

smooth muscle location + voluntary or involuntary

involuntary, found inside most body organs

what do muscles need to relax

ATP

what do your cells do when they don't have enough oxygen to produce ATP through aerobic cellular respiration?

fermentation

what does fermentation create

lactic acid, 2 glucose

function of muscles

tone and posture, movement, protection of organs, control openings, maintain body temperature,

parts of a muscle

muscle itself, muscle belly, fascicle, fibers, tapers off into tendon

define fascicle

bundle of fibers, makes up muscles

muscle fiber defined

single muscle cell (longest cell in your body!), where nerves and blood vessels are found

muscle belly defined

middle of the muscle where fascicles bunch up

actin

thin, light filaments found in muscle

how do muscles move?

nerve cells, which receive signals from the brain and move as they're told to.

epimysium

outermost layer that covers muscles, specifically the fascicles.

perimysium

the sheath of connective tissue that covers a bundle of muscle fibers

endomysium

innermost layer that covers muscle cells

soreness

microtears in the muscle after exercise, that grow back stronger and bigger

delayed onsent muscle soreness

DOM, explains why muscles need several hours to be sore and repair themselves

tendon

a cord or band of inelastic tissue connecting a muscle with its bony attachment, also a bundle of collagen fibers

shivering

contraction of muscles to create body heat, using energy

aponeurosis

any of the deeper and thicker fascia that attach muscles to bones; resemble flattened tendons

ruptured tendon

detaches a muscle completely from one of its bones, making the muscle unusable

longest muscle fiber + length

sartorius muscle, 60cm

each fiber is ______, meaning...

multinucleate, multiple nuclei per cell

rectus muscles

arranged in a straight order

what ways are muscles named?

direction of fibers, size, shape, location, attachment sites, origin, function

oblique muscles

diagonally arranged

larger muscles may be called

maximus, longus

smaller muscles may be called

minimus, brevis

medial muscles are found where

middle of the body, median

lateral muscles are found where

towards the sides of the body

attachment site/muscle head prefixes

bi/two, tri/three

the origin is a muscle attachment to what type of bone

immovable

insertion is a muscle attachment to what type of bone

movable

flex meaning

bend a joint

extend

straighten a joint

involuntary muscles are connected to what

nervous system, heart, brain

first step of muscle contraction

a signal is passed through a motor neuron to a muscle.

what happens to bones when muscles contract?

they pull closer together

contracted muscles create definition, which is called

muscle belly

what do the amount and force of muscle tension depend on:

frequency of stimulation (from central nervous system), number of skeleton muscle fibers involved, size of muscle fibers (larger fibers contain more myofibrils)

summation

process of recruiting more muscle fibers to generate a greater force, begins with a single muscle twitch and results in a single stimulus-contraction-relaxation sequence in the muscle

three parts of a twitch

latent period, contraction phase, relaxation phase

latent period of a muscle twitch

stimulus spreads through the muscle, first part

contraction phase of a muscle twitch

actin and myosin create tension, second part of the twitch

relaxation phase

last part of a muscle twitch, defined by actin and myosin uncoupling and the muscle relaxing (uses ATP)

tetanus

continuous simulation in your muscles, when twitches overlap. defined by a PROLONGED CONTRACTION.

creatine phosphate

can be broken down to release high-energy phosphates, quickly recharging ATP (8-10 seconds worth of contraction)

glycolysis

breaking down of glucose, releases 2 molecules of pyruvate and 2 molecules of ATP, takes place in cytoplasm. next step changes based on amount of oxygen

cellular respiration (aerobic)

breaks down 34 molecules of ATP for every molecule of glucose, takes place in mitochondria, oxygen-needing

post-glycolysis, anaerobic

usage of fermentation reactions, recycles unused products of glycolysis into 2 ATP, happens in cytoplasm without oxygen, produces LACTIC ACID which causes fatigue and soreness

causes of muscle fatigue

running out of glucose ("hitting the wall"), insufficient oxygen levels (forces muscles to rely on fermentation)

why are smooth muscles called smooth muscles

smooth muscles do not have these stripes and appear smooth.

second step of muscle contraction

the signal is sent through every fiber in the muscle through t-tubes

third step of muscle contraction

the sarcoplasmic reticulum releases calcium ions that initiate muscle contraction.

fourth step of muscle contraction

the calcium influx stimulates the myosin filaments to form connections to actin filaments

fifth step of muscle contraction, final step

the myosin filaments pull the actin filaments inward which causes the muscle to contract.