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Human Anatomy Chapter 10


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in all its forms muscle tissue makes up what % of a person's body weight?
Muscle is the only...
contractile tissue
How many skeletal muscles in the body?
> 600
WHat are the 4 functions of muscles?
Movement- attach to the bones and move them.

Maintenance of posture- allows the body to remain standing or sitting.

Joint stabilization

Heat generation
Special functional characteristics of muscles

Contractility- muscles contract forcefully

Excitability- are excitable by electral impulses (causing contraction)

Extensibility- muscle tissue can be stretched by the contraction of an opposing muscle.

Elasticity- after being stretcd, muscle can recoil and resume its resting length
What are the three types of muscle tissue
What is skeletal muscle
striated muscle that attaches to and move the skeleton (40% of body weight). Voluntary muscles.
What is cardiac muscle?
striated muscles that are only found on the walls of the heart and INVOULUNTARILY contract.
What is smooth muscle?
UNSTRIATED muscle tissue that lines the walls of the hollow internal organs (stomach, urinary bladder, blood vessels)
Muscle contracton depends on myofilaments named
Actin and myosin
which of three muscle classes' cells are NOT called fibers?
Cardiac (too short)
an "overcoat" of dense irregular connective tissue that surrounds the whole muscle?
Within each skelletal muscle exist a group of muscle fibers called _____________ each of which is surrounded by _______________________.
Fassicles; perimysium
within a fassicle there are many muscle fibers each one of which is surrounded by...
Each muscle fiber in a skeletal muscle is contacted by one nerve ending, which signals the fiber to contract. Such a contact occurs at...
the LESS movable attachment of a muscle is called its ________ while the more movable portion is called its ___________________.
Origin; insertion
another word for neuromuscular junction is...

a muscle and the nerve that innervates it..
this motor unit structure propogates a nervous signal
motor axon
this motor unit structure houses the signal.
motor terminals

(analogous to: synaptic terminal)
the space between the muscle and the nerve is called the
motor cleft
On the motor plate the structures that recieve the electrical impulse.
Motor receptors.
What does it mean to say that a motor unit operates on the "all or none principle"?
A certain electrical stimulation causes muscle contraction. less signal produces no contraction and more causes the same strength contraction.
How then do we adapt to carrying different lengths?
the body contracts a certain number of motor units. More are contracted for heavier items and less for less heavy items.
KEY POINT: The number of ________________ varies per motor unit.
Muscle fibers.

In other words, every motor unit has its own number of muscle fibers to enhance its specific functions.
Where would you want less muscle fibers per motor unit? Where would you want more?
You would want a low ratio in areas that require alot of control and not much strength (THE EYES).

You would want a lot of muscle fibers per unit in areas that will move heavy loads (biceps).
At what bone structures do muscles generally attach?
Trochanters, tendons, tubercles, tuberosities and Crests.
Muscle cells are structurally similar to normal cells but thier cytoplasm is actually called ______________ and their cell membrae is actuallly called ___________________.
Sarcoplasm; Sarcolemma
What key differnces are their in muscle cells?
Muscle cells are long and multinucleated.

as well as containing striations.
specialized contractile cellular organelles unique to muscle tissue.
What do myofibrils cause on the surface of muscle tissue?
the striations are long rows of myofibrils tied together in repeating sequences called
The sarcomere is the basic...
unit of contraction in skelltal muscle.
the boundaries of a sarcomere are called
Z discs (Z lines)
Extending internally from the Z lines, many fine filaments are found called?
thin (Actin) filaments
In the center of the sarcomere and overlapping the inner ends of the thin filaments is a cyllindrical bundle of ____________.
Thick (myosin) fillaments.
What key enzymes are found in the myosin thick filaments? what is its purpose
ATPase; to break apart ATP into its energy-yielding products in order to cause muscle contraction.
The dark bands on the sarcomere structure are called (the full length of dark filaments)
A bands
What myofibrils are found in the A band?
Both actin and myosin
the central part of each A band is called
the H zone
What myofibrils can be found in the H zone?
thick fillaments only (myosin)
The center of the H zone, which contains tiny rods that hold the adjacent thick myosin fillaments together.
M line
alternating with the A bands, these bands exist ehere only thin filaments occur.
I bands
which bands actually get smaller during contraction?
Z discs
During muscle contraction which zone DOES NOT change shape?
A zone
What occurs durring contraction of a muscle
the sarcomere shortens when the I bands narrow and the Z discs move closer together. Finally the H zone disappears.
During muscle extension what happens?
I zone and H zone widen, the Z discs move apart and the A discs again are unchanged.
an elaborate smooth endoplasmic reticulum whose interconnecting tubules surround each myofibril.
Sarcoplamic reticulum
What is the function of the sarcoplasmic reticulum?
Run longitudinally (parallel) to the myofibril.

These carry large amounts of Ca 2+ which is released when the muscle is stimulated. the calcium diffuse to the THIN FILAMENTS (ACTIN) and cause the sliding of actin fillaments over myosin fillaments.
What are the function of T tubules?
T- tubules are deep invaginations of the sarcolemma.

T tubules conduct the electrical impulses of the muscle to the deepest regions of the muscle cell.
Muscle have other action other than contracting such as isometric which is when...
muscles are active but not moving
(f.e: stretchiing or pushing on a wall)
Muscle have other action other than contracting such as concentric which is when...
muscles shorten (bicep curls)

*how is this different than flexion?
Muscle have other action other than contracting such as eccentric which is when...
muscles lengthen but still active

(f.e: putting down a heavy weight)
In which of the three are we strongest isometric, eccentrically, or concentrically?
Eccentrically we are 40% stronger. (we can put down more weight than we can lift)
Skeletal muscles are categorized into classes according to what 2 characteristics?
How they manufacture energy and the speed of contraction.
What are the two classes of how skelletal muscles manufacture their ATP?
Oxidative (aerobic)- those cells that produce ATP by aerobic respiration utilizing O2.

Glycolytic cells- those muscle cells that do not use O2 instead, they use the glycolytic cycle for ATP.
Slow oxidative fibers

- why are they red?
- have a large number of..
- speed/endurance/power
- found where
Red slow twitch

because of the oxygen binding molecule myoglobin

mitochondria (required for oxidative respiration)

High endurance

lower back / postural muscles
fast glycolytic fibers

- why are they pale?
- have a large number of..
- speed/endurance/power
- found where
White fast-twitch

Alot less myoglobin

myofillaments and twice the diameter of slow-twitch muscles.

Low endurance

Arms (biceps)
FAST oxidative fibers

- can be changed to what other skeletal muscle type?
- speed/endurance/power
- found where
Intermediate fast twitch

fast-twitch muscle fibers

High endurance

plenty of these fibers in marathon runners
(Lance Armstrong)
the anatomical term for growing larger muscles
the anatomical term for losing muscle mass
What was the oringinal intention of steroids?
To help cancer and anorexic patients suffering from atrophy to gain weight.
Does research show that steroids work? Side effects? Conclusion?
Yes, steroids do help the body produce more muscle but there are over 70 side effects and the conclusion is that the side effects far outweigh any potential benefit.
Supplements are a huge industry raking in how much money per year?
between 1.5 and 10 billion dollars.
Androstenedione (Mark McGuire)

-is a precursor to...
- which hormone does it become..
-clinical results
both sex hormones (estrogen and testosterone)

tendency to convert to the hormone that is least abundant in the body (estrogen in males and testosterone in females)

increased estrogen in males by 134% of levels before use.

-what class of macromolecule?
-Clinical proof?
- Practical significance
- Side effects

Yes, its the only supplement that has had the expected favorable outcomes.

Creatin only aids the athlete in the first 30 seconds of a high power excercise.

water retention, cramping, kidney failure (rare if water intake increases (WHICH IT DOES b/c it makes the individual thirsty)

-what class of macromolecule?
- Where else is this supplement found?
- clinical proof?
Growth hormone and Protein

Found in the breast milk of nursing mothers.

no clinical proof.

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