The Muscular System FQ: What is the hierarchal structure of a muscle cell from the tiniest fiber to the largest muscle mass? ET: Grab a copy of the article from the front of the room? Read and highlight important information from the article

The Muscular System Focus Questions ET: What are the four major roles of muscle tissue in the body? Use book Focus Questions FQ: What are the following: endomysium, perimysium, epimysium, tendon, and aponeurosis? Coloring Sheet POGIL

The Function of Muscles Four important roles for the body: Produce movement Maintain posture Stabilize joints Generate Heat

Review of Muscle Tissue Types All muscle cells are elongated, thus we call them fibers All muscle cells can contract Myo/Mys (muscle) Sarco (flesh)

Skeletal Muscle Connects muscle to bone Appears striped (striated) Voluntary May contract rapidly, and forcefully but tires easily Structure Endomysium Perimysium epimysium

Smooth Muscle No striations Involuntary, slow and constant contractions Lines hollow visceral organs – stomach, bladder, intestines Propels substances along a definite track within the body – food Double layered Sheet of thin cells running circularly and longitudinally

Cardiac Muscle Heart only Striated Slow, constant contractions Figure-8 shaped bundles that pump blood

Microscopic Anatomy of Skeletal Muscle Sarcolemma – the plasma membrane Myofibrils – bundles of myosin (thick) and actin (thin) proteins Sarcoplasmic reticulum – Store and release calcium for muscle contraction

Lesson 2 Skeletal Muscle Activity Muscular System Lesson 2 Skeletal Muscle Activity

Stimulation and Contraction of Muscles ET: Review anatomy of a skeletal muscle cell using your coloring sheet. FQ: How do muscles contract/move?

Nerve Stimulus and Action Potential The neurotransmitter Acetylcholine (Ach) is released by Axon terminal. This rush of positively charged ions creates a concentrations gradient/electrical current called an Action Potential. This makes the membrane of the muscle fiber (sarcolemma) permeable to sodium ions.

Mechanism of Muscle Contraction 1 Mechanism of Muscle Contraction 1. Ca+ ions cause troponin and tropomyosin (regulatory proteins) on the actin filament to change shape and move out of the way so that myosin can bind to it forming a cross bridge 2. using ATP, the myosin head bends toward the center of the sarcomere pulling actin filament (power stroke) 3. Detachment – ATP binds to the myosin head and weakens the cross bridge bond 4. The energy released by ATP reactivates the myosin for another contraction to occur

Lesson 3 Providing Energy for Contraction Muscular System Lesson 3 Providing Energy for Contraction

How does muscle keep up with all the ATP that they need? 3 Pathways Direct phosphorylation of ADP by creatine phosphate Aerobic respiration Lactic acid fermentation

Direct phosphorylation of ADP by Creatine Phosphate Creatine phosphate gives its phosphate to ADP to make ATP CP stores only last about 20 seconds

Aerobic Respiration Requires Oxygen 36 ATP / Glucose Slow compared to CP Aerobic Respiration

Lactic Acid Fermentation Does not require oxygen Quicker than CR (2.5 x faster) Uses huge amounts of glucose for not a lot of ATP Good for 30 to 40 seconds of strenuous exercise Build up of lactic acid causes muscle fatigue and soreness

2 Types of Muscle Contraction Isometric – when the fibers attach but cannot slide, like when you try and lift something too heavy. The muscle cannot contract, even though you are engaging it to lift something Isotonic – Normal muscle contraction where the fibers are successful in their sliding motion

What is Muscle “TONE”?? Continuous partial contraction that cannot be consciously controlled The nervous system stimulates these fibers in a systematic way all the time so that you can move when you decide to move

How Does Exercise Effect Muscles? Aerobic exercise causes muscles to become flexible with a greater resistance to fatigue Blood supply to the cell increases Mitochondria increase in number Increases overall body cell metabolism Strengthens bone Strengthens and enlarges the heart Improves gas exchange in the lungs

How Does Exercise Effect Muscles? Resistance training (isometric) causes individual muscle cells to develop more fibers and connective tissue Increases strength and ability to lift If you exercise your core you’re a providing stability to your entire body