LABORATORY FIVE The Skeletal Muscle System: Anatomy

Organization & Terminology Epimysium: Around entire muscle (bundles of fascicles) Perimysium: Around fascicles (bundles of muscle fibers) Endomysium: Around each muscle cell (fiber) P81, Fig. 5.1 – This is a whole muscle P82, P83, p84, Fig. 5.6, 5.7, 5.8 – These are each one muscle cell (fiber) – Notice the peripheral nuclei P82, Fig. 5.2 – Microscopic view of a skeletal muscle –Sarcomere: contractile subunits –Z lines: separate sarcomeres –A (Dark) bands - length of myosin –I (Light) bands - actin only 2

Motor Unit & Neuromuscular Junction Motor Unit (P82, Fig. 5.3): motor neuron + muscle fibers it innervates (stimulates) Neuromuscular junction (P83, Fig. 5.6): the point of communication between a motor nerve and a skeletal muscle fiber Motor end plate: the contact surface on sarcolemma 3

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 Skeletal muscles Contraction 4

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 lab manual 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 (indicated with an * in the tables) 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 model Right side superficial muscles Left side deep muscles 6

Head & Neck 7 P85, Table 5.1: Epicranius consists of frontalis, occipitalis, galea aponeurotica Scalenes: Remove the sternocleidomastoideus Posterior trunk Splenius & Erector Spinae: Remove Trapezius & Latissimus dorsi

(aponeurosis) Trunk Transversus abdominis can only be viewed internally

Quadriceps Group 9

Hamstring Group 10

Actions of Human Skeletal Muscles (Extra Credit) When a skeletal muscle contracts, the insertion moves toward the origin producing an action (a movement) The resulting action depends on the anatomy of the joint and the type of movement it can generate –Flexion/Extension: A movement that decreases/increases the angle between two bone –Abduction/Adduction: Movement of an appendage away from/toward the midline –Rotation: Movement of a bone around an axis –Circumduction: Movement of an appendage in a circle around a joint –Pronation/Supination: Turning the palm posterior/anterior –Inversion/Eversion: Turning the sole of the foot toward/away from the midline –Dorsiflexion/Plantarflexion: Moving the ankle joint to “stand on your heel”/“point your toe” –P104, Table 5.2: draw a stick figure in anatomical position & circle the appropriate joint in the 1st column. In column 2 & 3 you can just draw the joint using arrows pointing in opposite directions to indicate the movement 11

Prioritize studying for Lab 5 Name of muscles – most questions –ALL of the muscles included in the lab manual 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 the lab manual (extra credit)

Grades for First Practicum Answer key is posted on the window 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 –Make sure you turn in all your completed lab reports 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 13