Muscles

Types of Mucles

Striated Muscle- Skeletal Muscle1. Multinucleated2. Voluntary3. Striated

Cardiac Muscle1. Branched2. Intercalated disc3. Myogenic – does not

needa nerve impulse to

contract

Smooth Muscle1. Spindle shaped2. Involuntary

Vertebrate Skeletal MuscleSkeletal Muscle is also

called striated muscleSarcomere: repeating

unit of muscle tissue or functional unit of muscle contraction

Z lines ~ sarcomere border

I band~only actin proteinA band~actin & myosin

protein overlapH zone~central

sarcomere; only myosin

Sliding-filament modelTheory of muscle contractionSarcomere length reducedZ line length becomes shorterActin and myosin slide past each other (overlap

increases)

Steps of Muscle Contraction1. A motor neuron will release acetylcholine

at the synapse of the neuromuscular junction.2. Acetylcholine binds to receptors on the

muscle fiber and causes depolarization of the muscle fiber.

3. This creates an action potential along the T-Tubules (transverse tubules) to the sarcoplasmic reticulum (E.R.)

4. Calcium ions are released from the sarcoplasmic reticulum.

5. Calcium ions bind to troponin and cause it to move off of the actin, exposing the myosin binding sites.

6. Myosin cross-bridges form with the actin and pull the actin towards the center of the sarcomere. This requires ATP.

7. Ca++ is removed by active transport back into the SR after the action potential ends.

8. Tropomyosin blockage of the myosin binding sites is restored and the contraction ends and the muscle fiber lengthens (relaxes)

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter10/animation__action_potentials_and_muscle_contraction.html

Types of SkeletonsHydrostatic – consists of fluid held under

pressure in a closed body compartmentHydraNematodesAnnelids

Exoskeleton – hard encasements on the outer surface of the animal such as insects and lobsters.

Endoskeleton – hard supporting elements buried inside the soft tissues of the animal – bony skeleton