Muscle Physiology: The Actions of the Sarcomere.
Cardiac Muscle Characteristics Intercalated disks Striated Involuntary Located in heart
Skeletal Muscle Characteristics Many nuclei per cell Striated Voluntary Located along bones
Nonstriated Involuntary Located in digestive tract Smooth Muscle
Functions of Muscles Movement : results from muscle contraction, enables you to respond quickly Maintains Posture and Joint Stability : allows you to sit upright; stabilize joints of the body Support Soft Tissue: abdominal muscles protect underlying digestive organs. Guard Entrances and Exits Generate Heat : heat is generated as they work…FRICTION Maintains body temperature Skeletal muscles create the most heat
Characteristics of Muscle Tissue Excitability: ability to receive and respond to stimuli… Contractibility: ability to shorten quickly and with force… Extensibility: ability to be stretched or extended beyond their resting state… Elasticity: ability of a muscle fiber to recoil and resume its resting length
Organization of Muscle Muscles are composed of groups of fibers called fasicles. Fibers are the muscle cells inside all muscle. Tendons are bands of collagen fiber that attach muscle to bone.
Sarcomere: the contracting unit
Skeletal Muscle Striations
Z line I band H band A band
Organization from the muscle fiber to the sarcomere.
Cross sectional view of Sarcomere. Differences are detected in the sizes of the myofilaments Myosin is the thicker fiber. Actin is the thinner fiber.
Striations are seen because of sarcomere bands..
Muscle fiber structure Muscle cell Sarcolemma Sarcoplasm Sarcoplasmic reticulum T tubule mitochondria
Structure of Muscle Tissue
Sliding Filament Theory
Sliding Filament Theory Actin slides over myosin shortening the sacromere between the Z lines
Chain of Events during Muscle Contraction! 1. Cross Bridge Attachment 2. Power Stroke 3. Cross Bridge Detachment 4. Cocking (Recoil) of Myosin Head
What happens at the sarcomere?
Players for the power stroke Cross bridge attachment Power strokes Cross bridge detachment “Cocking” of the myosin head
Power stroke
Motor Unit: A motor neuron and all the muscle fibers it stimulates.
Diagram of a Muscle Twitch
Increase in muscle tension due to continued stimulation.
Muscle that reaches peak tension during rapid cycles of contraction and relaxation.
Complete tetanus = relaxation state is eliminated.
Label the following!
Aerobic Muscle Metabolism Glycolysis Aerobic Respiration Krebs Cycle ETC
Anaerobic Muscle Metabolism Oxygen Debt Lactic Acid Fermentation Muscle Fatigue
Creatine Phosphate
Red (slow) twitch fibers Aerobic Slow-acting ATPases (enzymes that break down ATP) Large amounts of myoglobin Red color to cell Abundant supply of mitochondria Fatigue resistant-as long as O2 is available High endurance (jogging, swimming, soccer)
White (fast) twitch fibers Large pale cells with twice the diameter of red fibers Very little myoglobin Contain fast-acting ATPases and contract rapidly Contain few mitochondria, but large glycogen stores Depend on anaerobic resp. to make ATP, therefore fatigues easily Low endurance, much power….sprints
Pink (intermediate) twitch fibers Mixture of red and white fibers Aerobic mechanisms and fatigue resistant Contain fast-acting ATPases High myoglobin content