Muscle Tissue

• Objective: Students will be able to compare and contrast the three types of muscle tissue.

 Muscle Tissue

I. Allows mammals to move

II. Three Muscle Types

a. Skeletal Muscle

i. Attaches to the skeleton

ii. Allows for motion

iii. Under Voluntary Control

1. Never signals for the nervous system

2. Striated appearance under the microscope

SKELETAL MUSCLE

b. Smooth Muscle

i. Involuntary Muscle

ii. Locate in many of the hollow organs

1. Including gastrointestinal tract, urinary bladder and blood vessels.

SMOOTH MUSCLE

Smooth musclearound this artery allows theartery to regulate blood flowby shrinking and expanding.

c. Cardiac Muscle

i. Found in the heart

ii. Involuntary- muscle functions without the conscious thought of the animal.

1. Muscles continue to function at all times, including during sleep.

CARDIAC MUSCLE

III. Myofiber

a. Entire muscle cell

b. Have several nuclei and large number of Mitochondria (Power House of the Cell)

c. Organized in parallel rows

d. Separated by connective tissue that includes blood vessels and nerves

muscle fiber

musclesarcomere

myofibril

IV. Muscle Movement- very complicated system

a. Within the Fiber there is a highly organized system of myofilament exist.

i. Two proteins make-up Myofilaments

1. Actin

2. Myosin

ii. Organized along entire length of the cell

muscle fiber

musclesarcomere

myofibril

myosin

actin

Z line

b. During Contractioni. Actin and Myosin slide

along each other

ii. Small bridges bind and release as they slide

CONTRACTION

RELAXATION

M linemyosin

Z line

c. Contraction begins with stimulation from a nerve cell

i. Stimulates the release of calcium stored in the endoplasmic reticulum

ii. Flow of calcium ions cause the filaments to slide across each other

iii. Energy is required

1. A large number of Mitochondria are present to supply energy

iv. Relaxation

1. Cell actively transports calcium back to the endoplasmic reticulum

a. Also requires energy

V. Porcine Stress Syndrome (PSS)

a. Genetically transmitted disease

i. Calcium is not transported back into the endoplasmic reticulum

b. Muscles DON’T relax

c. Bouts of PSS occur when pigs are stressed

i. Heat

ii. Transportation

d. Extreme muscling and leanness

i. Predisposition for PSS

1. A susceptibility to a disease, arising from a hereditary or another factor

VI. Rigor Mortis (Muscle Stiffness)

a. Occurs after death

b. No energy supply to pump calcium back to endoplasmic reticulum

c. Animal cannot relax and remains stiff

VII. Hypocalcaemia – Milk Fever

a. Dairy Cows can develop a lack of calcium around calving time

b. Dramatically increases the use of calcium for milk production

i. Calcium levels in blood and muscles become too low

c. Cow becomes weak and unable to rise

d. Veterinarians treat milk fever with a calcium solution placed directly into the blood stream

i. Blood carries calcium to muscle

ii. Within a few minutes after treatment the affected cow often stands

VIII. Fine Control of Muscle Movement

a. A nerve cell stimulates more than one muscle fiber

i. Motor Unit is the collection of nerve cell and all the muscle fibers it stimulates.

b. Fine Control involves a small number of muscle fibers

i. Example- eye and larynx

IX. Gross movement- Example- upper leg

a. Large number of fibers for each nerve cell

b. The more motor units used, the more completely the muscle contracts conversely, the fewer motor units used, the less the muscle contracts.

c. Muscles do get larger in response to their usage.

i. Individual fibers add more myofilaments to become larger

d. When a muscle is not used it decreases in size.

i. Inactivity

ii. House pets that get little exercise

iii. Limb immobilized in a cast

iv. Nerve Damage- muscle Shrinks

v. Example – Draft horses

1. Nerve in front shoulder damaged

2. Muscle on top of the shoulder blade shrinks

3. Condition is called a Sweeny

X. Cardiac muscles cells have the unique ability to initiate their own contraction.

a. No nerve cell stimulation is necessary

b. Pacemaker cells are responsible for establishing the rate of contraction.

c. Autonomic nervous system increases or decreases the heart rate.