Human Anatomy - Muscle Lecture

What are the 3 types of muscle tissue?

skeletal, cardiac, smooth

Smooth muscle

visceral muscle (nonstriated) involved in involuntary movement

Where can smooth muscle be found?

walls of hollow organs, blood vessels, intestines, and urinary bladder

cardiac muscle

myocardium that is striated and involved in involuntary movement

Where can cardiac muscle be found?

heart

skeletal muscle

striated and voluntary; the muscular system refers to skeletal muscle

Functions of skeletal muscle

1. Production of skeletal movement

2. Maintenance of posture/body position

3. Support for soft tissues

4. Guarding entrances and exits of the body

5. Maintaining body temperature (85%)

exercising; bed- or wheelchair-bound

individuals

What 3 layers of connective tissue surround skeletal muscle?

Epimysium ("epi" -- upon)

Perimysium ("peri" -- around)

Endomysium ("endo" -- inside)

Muscle fasicle diagram

Muscle fiber diagram

What do the collagen fibers of the skeletal muscle layers do?

they blend together forming the cord-like tendons and sheet-like aponeuroses. Here, there are no muscle fiber enclosed and they are used to attach muscles to other structures

sarcolemma

muscle sheath, analogous to the cell membrane and surrounds sarcoplasm (cytoplasm)

sarcoplasm

contain multiple myofibrils; sarcoplasmic reticulum, or internal membrane system, surrounds each myofibril

sarcomeres

contractile units of skeletal muscle (myofilaments made of actin and myosin)

myofibrils

bundles of myofilaments

myofilaments

proteins (actin and myosin) that are arranged in repeating units

Actin and Myosin are organized into repeating units called _________.

sarcomeres

How many of sarcomeres does each myofibril consist of ?

10,000

z-line

defines the end of the one sarcomere and the beginning of the next

M-line

middle of a sarcomere; supports myosin (thick) filaments

A band

entire length of thick filament (myosin) and overlap thin (actin) filaments

H zone

zone of thick filaments only, centered within the "A band"

I band

thin filaments only

sliding filament theory

muscle contraction, which is a shortening of sarcomeres

when does sliding occur? What does this movement require?

myosin heads bind to active sites on actin filaments and literally pull actin filaments inward. Requires calcium and ATP (acetycholine initiates contraction)

Actin

resemble a double strand of pearls twisted together (thin filaments)

Myosin

hockey stick or golf club (the heads are flexible); handles oriented toward the center, heads sticking out in all directions (THICK FILAMENTS)

Muscle fibers are arranged in bundles called..?

fascicles

What are the 4 patterns of muscle in the body?

1. parallel muscles

2. convergent muscles

3. pennate muscles

4. circular muscles

Motor unit

1 motor neuron and all the muscle fibers it controls

Each muscle fiber works on an "____-or-____" principle

all-or-none

recruitment

increasing number of motor units

What is the innervation ratio for most muscles?

1 motor neuron for each 100 to 150 muscle fibers (contains myofibrils)

What is the innervation ratio for precise, dexterous movements (eye muscle)?

1:10

What is the innervation ratio for massive muscles responsible for gross body movement (thigh)?

exceeding 1:500

What can increase the size of muscle fibers?

exercise; increasing exercise means more myofilaments (actin and myosin) are synthesized

hypertrophy

Increase in size of muscle fibers (myofilaments) by increasing exercise

muscular atrophy

a wasting away of muscles because of progressive loss of myofibrils due to disuse or denervation

3 types of skeletal muscle fibers

fast, slow, and intermediate fibers

fast skeletal muscle fibers

fact acting; high energy requirements; fatigue easily

slow skeletal muscle fibers

more myoglobin as a reservoir for oxygen; slow contraction, but can be sustained

Intermediate skeletal muscle fibers

combination of both fast and slow; can be trained to function more aerobically or anaerobically

Muscle soreness

Not just the result of lactic acid buildup but can result from damage to contractile proteins (actin and myosin) within muscle

lockjaw/tetanus

Bacterial infection enters through puncture wound; neurotoxin results in tetany (continous contraction of muscle). Mandible's muscle is affected first

Shinsplints

result of stress fracture or periosteum damage of tibia

Rigor Mortis

Lasts for 24 hrs, disappears as tissues begin to disintegrate. Caused by attachment of myosin heads to actin which freeze in place

Origin

point of attachment that is less moveable; fixed end

Insertion

the point of attachment of a muscle to the part that is more moveable; where the action is exerted

Action

the movement or effect; muscle fibers pull the insertion toward the origin

Belly

the area mid-way between the origin and insertion

Prime movers

muscles conducting the major motion

Synergists

assists, complements, stabilizes, or prevents unwanted motion

Antagonists

acts against the prime mover and will be prime movers in restoring body position

How are muscles named?

1. Origin/Insertion

2. muscle fiber direction

3. position of muscle

4. size of muscle

5. action of muscle

What is the musculotendinous cuff (rotator cuff) made of?

1. Supraspinatus m.

2. Infraspinatus m.

3. Teres minor m.

4. Subscapularis m.

What makes up the quadriceps femoris?

1. Rectus femoris m.

2. vastus lateralis m.

3. vastus medialis m.

4. vastus intermedius m.

What makes up hamstrings?

1. Biceps femoris m.

2. Semitendinosus m.

3. Semimembranosus m.

muscles of mastication (chewing)

1. Masseter m.

2. Temporalis m.

3. Pterygoids mm.

muscles of facial expression

1. Orbicularis oris m.

2. Buccinator m.

3. Occipitofrontalis m.

4. Platysma m.

Why are joints of your hand partially fixed even when the hand is relaxed?

Antebrachial muscles that flex these joints are larger and stronger than those that extend the joints