Brainstorm a list of the three types of muscle and their characteristics

Types of Muscle Tissue (cont.) Muscle Group Major Location Major Function Mode of Control Skeletal Muscle Attached to bones and skin of the face Produces body movements and facial expressions Voluntary Smooth Muscle Walls of hollow organs, blood vessels, and iris Moves contents through organs; vasoconstriction Involuntary Cardiac Muscle Wall of the heartPumps blood through heart Involuntary

Types of Muscle Tissue Muscle cells – Myocytes called muscle fibers – Sarcolemma – cell membrane – Sarcoplasm – cytoplasm of cell – Myofibrils – long structures in sarcoplasm Arrangement of filaments in myofibrils produces striations

Skeletal Muscle Structure & Function

General Information prefixes myo- & mys- (meaning muscle) & sarco- (meaning flesh) refer to discussion of muscles Muscles attach to bones by tendons Origin – where the muscle attaches to the bone that remains relatively stationary during contraction Insertion – where the muscle attaches to the bone that moves when the muscles contract

2. Can categorize muscles by how they work Synergists – muscles that cause the same action at a joint (biceps & brachialis; quadriceps group)

2. Can categorize muscles by how they work Antagonists – muscles that produce opposing action (biceps vs/ tricepts; quads vs. hamstrings)

Functions produces movement maintaining posture stabilize joints b/c tendons go over the joints and help keep bones in place generating heat – skele muscle is ~40% of body mass and is most responsible for heat production

Skeletal Muscle Made of muscle fibers (myofibril) packed into sheets of muscle – Muscle fibers are cigar-shaped & have several nuclei – Individual muscle fibers are made of smaller pieces… we’ll get to that Some muscle fibers are about 1 ft in length Have visible stripes Voluntary can contract quickly & w/ large force but tires easily and must be rested after use individual cells are fragile but muscles are strong…why?

tendon bone fascicle muscle fiber myofibril Sarcoplasmic reticulum filaments

Structure: Connective Tissue Coverings Fascia – Covers entire skeletal muscles – Separates them from each other Tendon – A tough, cord-like structure made of fibrous connective tissue – Connects muscles to bones

How are tendons made? All muscles are covered in connective tissue  perimysium Collagen fiber density inc. near points of attachment  make a tendon Attach onto covering around the bones  periosteum

Structure: Connective Tissue Coverings Aponeurosis – A tough, sheet-like structure made of fibrous connective tissue – Attaches muscles to other muscles

tendon bone fascicle muscle fiber myofibril Sarcoplasmic reticulum filaments

Microscopic anatomy of muscle fibrils

1. An action potential reaches the skeletal muscle. The influx of ions causes an electrical impulse to be sent over the muscle. The impulse travels through the sarcolemms (cell membrane) and dives into the myofibrils via T-tubules. Making Muscles Contract

2. The electrical impulse (change in charge of the muscle’s cytoplasm aka sarcoplasm) opens voltage-gated calcium in the sarcoplasmic reticulum channels. Ca2+ flows out of the sarcoplasmic reticulum and bathing the proteins in the myofibrils in Ca2+ Making Muscles Contract

3. Ca2+ attaches to actin filaments and untwists the proteins exposing binding sites for the myosin heads. Myosin heads attach to the actin forming cross bridges. Making Muscles Contract

4. ATP supplies myosin with energy to change shape and pull the actin filaments toward the midline of the sarcomere. This shortens the sarcomeres and thus the entire muscle in a contraction. Another ATP molecule changes the shape of the myosin again. This allows the myosin to release the actin and the muscle relaxes.

How Skeletal Muscles Move Stimulated by nerve impulses Axon terminal and the sarcolemma (plasma membrane of muscle cells) are close together with a synaptic cleft in between Neuron releases ACh across the cleft  attaches to receptors on the sarcolemma  allows Na+ to enter making cell more + making an action potential  causes contraction of the sarcomeres and thus the muscle hill.com/sites/ /student_view0/chapter10/animation__action_potentials_and_muscle_cont raction.html

Question 1 What structure is used to connect actin and myosin during muscle contraction. Myosin heads AKA “paddles”

Question 2 Compare/contrast the insertion and origin? Answer – Insertion- usually more distal (limbs)insertion point moves toward the origin – Origin- where a muscle attaches to a bone that does not move during muscle movement

Question 3 Put the following parts of a muscle in order from largest to smallest and explain what each is – Myofibril – Fascicle – Myofibril – Sarcomere – Myosin head AKA “paddles” Answer – Fascicle  myofibril  sarcomere  myofibril  myosin heads

Question 4 After an action potential is sent to the muscle what two things (ions, molecules, etc) a required for muscle contraction? What does each one do? Answer – ATP- allows the myosin heads to pull the Z disc in towards the center of the cell for muscle contraction – Calcium- changes the shape of actin to expose binding sites for the myosin heads

Question 5 What structure gets pulled in towards the center of the sarcomere in muscle contraction? Answer: z-lines or z proteins

Whisper Down the Lane You are sitting and you want to stand. Collectively you must describe the progression of events that will occur in order to get the “move” message to your skeletal muscles (focus on just ONE muscle). Tell the person next to you what is going to happen first and they are going to share what you told them plus the next correct, logical step in this process.