Chp 8: Muscular System

What is the prefix for 'muscle'?

myo-

What is the prefix for 'muscle cell'?

sarco-

4 Characteristics of muscle

1. Excitability​

2. Contractibility​

3. Extensibility​

4. Elasticity

3 primary functions​ of muscle

1. Provide motion​

2. Maintain posture​

3. Generate heat

Elasticity

return to their original shape & length after contraction or extension

Extensibility

stretch when pulled

Contractibility

shorten in length when stimulated

Excitability

respond to a stimulus such as a nerve impulse

Skeletal Muscle

voluntary, striated, multiple nuclei

Cardiac Muscle

involuntary, striated, intercalated discs, single nuclei

Smooth Muscle

involuntary, non-striated, single nuclei

epimysium

fibrous connective sheath that surrounds a group of muscle cells 

Tendon

-a band of fibrous connective tissue that binds muscle to bone

-it anchors to the periosteum of bones

Aponeuroses

Attach to bones or muscles by broad sheets of fibrous tissue

What is the most prominent aponeurosis

Linea Alba

Linea Alba

-an aponeurose that divides the abdomen, on the ventral midline, into left and right halves

-landmark for surgical incisions

Origin Site

-where a skeletal muscle begins

-has minimal movement and is most stable during muscle contraction

Insertion Site

-where skeletal muscle attaches to bone

-undergoes the most movement during muscle contraction

gastrocnemius muscle

muscle on the back of your calf

origin site of the gastrocnemius muscle

on the caudal femur

insertion site of the gastrocnemius muscle

Calcaneal tuberosity of the fibular tarsal bone (point of hock)

Agonist

a skeletal muscle or muscle group that is the prime mover and completes desired action

Antagonist

a skeletal muscle or muscle group that completes the opposite action of the agonist

Relationship between Biceps brachii and Triceps brachii

• Biceps brachii flexes elbow

• Triceps brachii extends the elbow

• each can act as an agonist or antagonist

Synergist

a skeletal muscle that contracts at the same time and assists agonist muscle's desired action

Relationship between deep digital and superficial digital flexors

•  deep digital flexor flexes digits of front limb

• superficial digital flexors acts as synergist to aid motion

Fixator

stabilizes joints to allow other movements

Fixator example

Clenched fist activating the digital flexor muscles and muscles over the top of your forearm contract to stabilize your wrist

how many nuclei do Skeletal muscle cells have

100 or more per cell

sarcoplasmic reticulum

storage organelle for calcium ions

What is one skeletal muscle fiber made up of

hundreds of thousands of myofibrils

Fascicles

groups of muscle fibers

Perimysium

• layer of connective tissue that binds fascicles in muscle

• composed of reticular & thick collagen fibers

What is another name for a muscle cell?

muscle fiber

Endomysium

• delicate connective tissue layer

• surrounds each individual skeletal muscle fiber

• composed of fine reticular fibers

Myofibrils

-contractile components of a muscle cell

- myofilaments (actin and myosin) are contained within a myofibril.

Sarcolemma

-cell membrane of an individual muscle cell

-very energy-demanding

Transverse tubules (T- tubules)

conduct impulses to lead to contraction in individual muscle fibers

Sarcomere

series of protein filaments that make up contractile units of muscle cells

Z line or disc

disc on each end of sacromeres

Actin

thin, dark protein filament

What is actin fibers made up of

• 2 strands of protein

• forms helical structure

Where does actin attach to 

• attach to Z lines

• extend toward center of sarcomere but don’t meet

Myosin

thick, dark protein filament

What is myosin molecules made up of

twisted tail attached to 2 globular heads

what are cross bridges

• two globular heads on myosin form bridges to actin 

• interacts w/ actin to shorten sarcomere during a muscle contraction

What does Myosin appear to be doing

• float in the middle of sarcomere between parallel actin fibers

• don’t connect to Z lines

Atrophy

loss of skeletal muscle mass and ability to function

Neuromuscular junctions

sites where ends of motor nerve fibers connect to muscle fibers

synaptic space

very small space between end of nerve fiber and sarcolemma

synaptic vesicles

tiny sacs at the end of a nerve fiber

what chemical neurotransmitter does synaptic vesicles contain

acetylcholine

Motor Unit

one nerve fiber and all the muscle fibers it innervates (controls)​

Only a Few muscle fibers per motor unit​ creates

Small, delicate movement of muscles​

Huge numbers of muscle fibers per motor unit​

Large, powerful movement of muscles​

Motor Neuron

skeletal muscle neuron

Endomysium, perimysium, and epimysium are continuous with the ___ that connect muscle to bones or other muscles

tendons or aponeuroses

What 3 things do the connective tissue layers of muscles also contain

1. blood vessels

2. nerve fibers

3. adipose tissue

marbling

fat deposits often grossly visible in meat

How is glucose stored in skeletal muscle cells?

glycogen

How is oxygen stored in skeletal muscle cells?

myoglobin

What compound converts ADP to ATP?

Creatine phosphate

Nerve Impulse reaches sarcoplasmic reticulum via what structure​

T-Tubules

what type of ions are released into sarcoplasm ​

Ca++ ions

Ca++ ions diffuses into ___ and starts contraction​

myofibrils

Muscle contraction stops with the removal of ___

removal of Ca++​ ions

Muscle ___ & ___ both require energy

contraction & relaxtion

Twitch contraction

A single muscle fiber contraction

What is the all or nothing principle?

When stimulated, individual muscle fiber contracts completely—or not at all​

During what type of metabolism is lactic acid formed?

anaerobic metabolism

anaerobic metabolism

• Need for oxygen exceeds available supply​

• “out of oxygen”

• not as efficient

What 2 “nutrients” do we get the energy required to produce creatine phosphate & ATP from

1. glucose

2. oxygen

What causes the “burn” in our legs

Lactic acid build up in muscle tissue during anaerobic exercise

When activity is done, the lactic acid diffuses into the ___​

bloodstream

After the lactic acid diffuses into the bloodstream, it makes its way to the ___

liver

In the liver, lactic acid is converted back to ___ by a process that requires oxygen

glucose

Why are people still breathing hard even though you are done running?

Our bodies are repaying the liver for its “oxygen debt” to turn that lactic acid back into glucose

rigor mortis

stiffness of skeletal muscles that occurs shortly after an animal dies

When an animal dies, skeletal muscle cells dump all of their ___ out of their sarcoplasmic reticulum

calcium

When an animal dies, calcium stimulates ___, which utilizes all of the ATP (energy) ​

muscle fiber contraction

When an animal dies, muscle cells get stuck in ___

stuck in contraction

what mechanisms in the body eliminates excess heat​

panting or sweating

Why do people shiver when we’re cold

Spasmodic muscle contractions increase heat production​

Muscle named based on Action

Superficial digital flexor​

Superficial digital flexor​

flexes digits when it contracts

Muscle named based on shape

Deltoid (“triangle”)​

Deltoid (“triangle”)​

• triangular muscle

• located in shoulder region

Muscle named based on location

Biceps brachii​

Biceps brachii​

located in brachial (upper arm) region

Muscle named based on direction of fibers

Rectus (“straight”) abdominis​

Rectus (“straight”) abdominis​

• 2 strap like muscles

• on either side of linea alba

• on ventral abdomen

Muscles named based on number of heads or divisions

Biceps brachii, triceps brachii, quadriceps brachii​

Muscles named based on attachment sites

Sternocephalicus (sternum and head!)

Sternocephalicus

• origin site: sternum

• insertion site: back of head

The action of this superficial muscle is to twitch the skin

Cutaneous Trunci

Cutaneous Muscles​

Thin, broad superficial muscles​

where are Cutaneous Muscles​ found

Found in connective tissue (fascia) just beneath skin​

Cutaneous Muscles​ have ___ attachment to bones

little or no attachment

what body parts does the Cutaneous Trunci cover

dorsal, lateral, ventral walls of thorax & abdomen