The Skeletal Muscle System: Anatomy LABORATORY FIVE The Skeletal Muscle System: Anatomy Next week, cadavers will be available for those who are interested. It’s optional.11/11/2018

Organization & Terminology Endomysium: Around each muscle cell (fiber) Muscle fiber – Notice the peripheral nuclei Microscopic view of a skeletal muscle Striations (dark and light bands) Sarcoplasm and sarcolemma Myofibril (contractile organelle A (Dark) bands: correspond to length of myosin (thick) filaments I (Light) bands: actin (thin) only Z line: anchor for actin; separates sarcomeres H zone: center of A band; no actin M line: Narrow region at center of H zone; anchor for myosin Epimysium: A thicker coat of dense CT Perimysium: collagenous fiber membrane Endomysium: areolar CT

Motor Unit & Neuromuscular Junction Motor Unit: motor neuron + muscle fibers it innervates (stimulates) Neuromuscular junction: the point of communication between a motor nerve and a skeletal muscle fiber Motor end plate: the contact surface on sarcolemma Motor Neuron: Myelinated axon Axon terminal Schwann cells If you pick up a piece of paper, you don’t need to activate a lot of motor units, but for picking up a heavy object, you plan ahead to employ all of these motor units and use more muscles; therefore, more strength. Some muscles are controlled by a few neurons and some muscles by only one neuron.

Skeletal muscles Contraction In order for contraction of a muscle to cause movement, there are attachment sites on two different bones: Origin: Less movable attachment Insertion: More movable attachment Action: Moves insertion toward origin

Muscle Action and Origin/Insertion You need to learn the action of muscles listed on the provided handout – use flash cards or highlight them in your textbook For muscles with more than one listed action, learn the action that pertains to the joint within parenthesis Origin & insertion are extra credit learning material. Learn all muscles Origin and Insertion, not just the muscles listed on the provided sheet Both origin/insertion and action questions will be just a written question not on the model

Identification of Human Skeletal Muscles Mostly superficial muscles and only a few deep muscles ID some attachments by name ID muscles that work the head, neck, shoulder, anterior & posterior trunk, elbow, wrist, hip, knee, and ankle View superficial muscles on leg and arm models (do not take them apart) Flexors: anterior view Extensors: posterior view View deep muscles on the torso model and on the head, neck, and shoulder models Right side superficial muscles Left side deep muscles Many students are confused about flexors versus extensors of the forearm because the figure in their book shows an arm that is missing some fingers.

Head & Trunk Muscles Not Shown in your Textbook Epicranius: frontalis, occipitalis, galea aponeurotica Anterior Trunk External and internal intercoastals Posterior trunk Splenius, rhomboid & erector spinae: Look on the left side of the model where trapezius & latissimus dorsi are removed Ligamentum Nuchae (medial posterior neck) Dorsal lumbar Fascia Supra & infraspinatus Teres Major: inferior to infraspinatus Splenius & Erector Spinae: Look on the left side of the models where Trapezius & Latissimus dorsi are removed

Trunk Transversus abdominis can only be viewed internally (aponeurosis) Transverse abdominis is the first muscle to be used during starvation and it is not replaceable, not mitotic cells… Transversus abdominis can only be viewed internally

Quadriceps Group

Hamstring Group

Prioritize studying for Lab 5 Name of muscles – most questions ALL of the muscles included in the handout are assigned for identification purposes Gross and microscopic view of skeletal muscle Assigned muscle actions (provided handout) e.g.: Name the muscle that extends elbow: triceps brachii Origin & insertion of all muscles in your handout (extra credit)

Grades for First Practicum Answer key is posted on the cabinet Grades “A”, “B”, “C”: Congratulations! Continue doing what you’re doing Help your classmates get better Tell them your learning strategy Make sure you get a grade “C” or better on the lecture portion of the course Grade “D” in lab, and “C” or better in lecture Read ahead, get yourself familiarized with the upcoming lab Visit the last hour of other labs with instructors’ permission Attend open lab regularly Do all your lab quizzes Make sure you turn in all your completed lab assignments on time Do all the extra credit assignments Make sure you do well on the lecture portion of the course Grade “F” This should be a wake up call for you What you have been doing is not working for you Change your learning strategy Talk to your classmates who have been successful on the first practicum Form study groups