Muscle Contractions, Fatigue & Names 2/1/2019 SAP2b

Type of Muscle Contractions Isotonic contractions “same tone” Myofilaments are able to slide past each other during contractions The muscle shortens, tension rises Walking, running, lifting an object 2/1/2019 SAP2b

Types of Muscle Contractions Isometric contractions “same measurement” Tension in the muscle increases The muscle is unable to shorten and tension does not exceed resistance Pushing against a wall with bent elbows 2/1/2019 SAP2b http://www.biosolutions.info/2008/02/muscle-contraction.html

2/1/2019 SAP2b

Isometric vs. Isotonic 2/1/2019 SAP2b

Concentric-movement causes a muscle to shorten Eccentric- Muscle lengthens—elongation of muscle 2/1/2019 SAP2b

Muscle Fatigue Muscle fatigue – the muscles inability to contract even though it is being stimulated Occurs when: ATP production fails to keep pace with ATP used Relative deficit of ATP, causing contractures Lactic acid accumulates in the muscle Ionic imbalances are present Result of oxygen debt 2/1/2019 SAP2b

Muscle Classification Prime Mover agonist Causes a desired action Ex: elbow flexion (biceps brachii) Antagonist Relaxes when prime mover contracts Ex: elbow flexion (triceps brachii) Synergist Helps the prime mover by reducing unnecessary movements Fixators Stabilize the origin of the prime mover Can immobilize a bone 2/1/2019 SAP2b

Muscle Names Muscles are named based on: size shape location action number of attachments direction of its fibers 2/1/2019 SAP2b

Direction Rectus: parallel to the midline Transverse: perpendicular to the midline Oblique: diagonal to the midline 2/1/2019 SAP2b

Size Maximus: largest Magnus: large Minimus: smallest Major: larger Longus: longest Minor: smaller Latissimus: widest Vastus: great Longissimus: longest 2/1/2019 SAP2b

Shape Deltoid: triangular Piriformis: pear- shaped Trapezius: trapezoid Platys: flat Serratus: saw-tooth Quadratus: square Rhomboid: diamond-shaped Gracilis: slender Orbicularis: circular Pectinate: comblike 2/1/2019 SAP2b

Action Flexor: decreases joint angle Extensor: increases joint angle Abductor: moves bone away from midline Adductor: Moves bone closer to midline Levator: produces superior movement Depressor: produces interior movement Supinator: turns palms up Pronator: turns palms down Sphincter: decreases size of opening Tensor: makes body part rigid 2/1/2019 SAP2b

Number of Origins Biceps: two origins Triceps: three origins Quadriceps: four origins Location: Pectoralis: chest Gluteus: buttock Temporalis: temporal Brachii: arm Lateralis: lateral

Arrangement of Fascicles Circular-arranged in rings Convergent-muscle has broad origin & fascicle converge into 1 insertion

Arrangement of Fascicles Parallel- fascicle runs parallel to axis of muscle Fusiform-spindle shaped muscle with large muscle body

Arrangement of Fascicles Pennate: fascicles are short & at angle to a tendon -unipennate- fascicle insert in 1 side of tendon -bipennate-fascicles are on both sides of tendon -multipennate-from multiple directions in tendon

Basic Principles of skeletal muscles 1. skeletal muscles produce movement by pulling bones (muscle only pull, they never push) 2. Bones act as levers and joints act as fulcrums for muscles to bring about movement 3. They contract only when stimulated 4. They contract according o the graded strength principle 5. A muscle fiber will follow the all or none principle 6. Muscles that move parts usually do not lie over that part 7. Muscles act in groups rather than singly.

Lever Systems A partnership between muscle and bone Levers- bone/bar that moves on a fixed point Fulcrum-joint/fixed point Load-weight or resistance to be moved

1st class 2nd class 3rd class

Aging & Muscles Muscles begin to shrink and lose mass Size of muscle fiber decreases Tendons become stiffer due to decreased water content

40 Superficial muscles divided into 12 regions 2/1/2019 SAP2b

27 superficial muscles divided into 7 regions 2/1/2019 SAP2b

Based on what you know about naming skeletal muscles, what do you predict about the following muscles: Biceps femoris Rectus abdominis Flexor carpi ulnaris 2/1/2019 SAP2b

Sternocleidomastoideus Flexes and Rotates Head The first muscle we will learn is the sternocleidomastoideus. It is sometime called the sternocleitomastoid. It is the same neck muscle shown on the previous slide. * This muscle has two origins. The first origin is on the sternum manubrium. The second origin is on the clavicle. *The insertion is on the mastoid process of the skull. *Contraction of both sternocleidomastoideus muscles will flex the head. If just on of the muscles contracts, the head will rotate.

Masseter Elevates Mandible The masseter is one of major chewing muscles. *The origin of the masseter is on the zygomatic arch. *The insertion is on the mandible. *Contraction of the masseter will elevate the jaw.

Elevate & Retract Mandible Temporalis Elevate & Retract Mandible The temporalis is another chewing muscle. Note how it attaches on the side of skull. *It also elevates the mandible. Also note I did not give the origin and insertion of this muscle. You will only need to know the origin and insertion of a few of the muscles in this unit.

Extend Head, Adduct, Elevate or Depress Scapula Trapezius Extend Head, Adduct, Elevate or Depress Scapula The trapezius is a large muscle in the upper back. It attaches to the skull, shoulder and vertebrae of the back. *When this muscle contracts it will cause the head to extend. It will also move the scapula. The direction the scapula moves depends on which part of the trapezius contracts. The trapezius may adduct elevate or depress the scapula.

Extend, Adduct & Rotate Arm Medially Latissimus Dorsi Extend, Adduct & Rotate Arm Medially The latissimus dorsi is a large muscle in the back. It is often referred to as a lat. *It has origins on the vertebrae, ilium ribs and scapula. *The insertion is on the humerus. When it contracts it moves the humerus. *It can extend, adduct and rotate the arm medially. This is the main muscle used in movement such as pounding a nail with a hammer.

Abduct, Flex & Extend Arm Deltoid Abduct, Flex & Extend Arm The deltoid covers the shoulder and has the shape of a delta. *It has origins on the scapula and clavicle. *The deltoid inserts on the deltoid tuberosity of the humerus. *Contraction of the deltoid will adduct the arm. If only the anterior fibers of the muscle contract it will flex the arm. Contraction of the posterior fibers will extend the arm.

Flexes, adducts & rotates arm medially Pectoralis Major Flexes, adducts & rotates arm medially The pectoralis major is a large muscle in the pectoral region of the body. *It has origins on the clavicle and sternum. *The insertion is on the greater tubercle of the humerus. *Contraction of the pectoralis major will flex the arm. It will also adduct and rotate the arm medially. The pectoralis major is used in movements such a climbing, throwing and doing pushups.

Biceps Brachii Flexes Elbow Joint The biceps brachii is located on the anterior side of the upper arm. It is often just called the biceps. There is a biceps femoris in the leg we will study shortly. *The biceps has two origins. One origin is on the corocoid process and the other on the Glenoid cavity of the scapula. The “bi” in biceps refers to the two origins. *It inserts on the radial tuberosity. *Contraction of the biceps will cause flexing at the elbow joint.

Triceps Brachii Extends Elbow Joint The triceps is on the back of the upper arm. *It has three origins. Two origins are on the back of the humerus and one on the scapula. *The triceps inserts on the olecranon. *Movement of the triceps will extend the elbow joint.  

Rectus Abdominus Flexes Abdomen Rectus abdominus is a long muscle in the abdomen. *The muscle originates on the pubis. *It inserts on the xiphoid process of the sternum and also on cartilage of the ribs. *When rectus abdominus contracts it will flex the abdomen.  

External Oblique Compress Abdomen Another muscle in the abdomen is the external oblique. It has muscle fibers that run in an oblique direction across the abdomen. *Contraction of the external oblique will compress the abdomen.

External Intercostals Elevates ribs There are two groups of muscles that run between the ribs. The first are the external intercostals. *They will elevate the ribs.

Internal Intercostals Depress ribs The internal intercostals are also located between the ribs. *They will depress the ribs.

Diaphragm Inspiration This is an inferior view of the diaphragm. This muscle separates the abdominal cavity from the thoracic cavity. *When it contracts it will cause inspiration.

Forearm Muscles Flexor carpi—Flexes wrist Extensor carpi—Extends wrist Flexor digitorum—Flexes fingers Extensor digitorum—Extends fingers Pronator—Pronates Supinator—Supinates There are several muscles in the forearm that have important movements. *The flexor carpi are used to flex the wrist. *Extensor carpi extend the wrist. *Flexor digitorum flexes the fingers. *Extensor digitorum extends the fingers. *The pronator pronates. *A supinator muscle will supinate.  

Extends & Rotates Thigh Laterally Gluteus Maximus Extends & Rotates Thigh Laterally The large muscle on the posterior side of the body at the top of each leg is the gluteus maximus. *The gluteus maximus originates on the ilium, sacrum and coccyx. *It inserts on the gluteal tuberosity of the femur. *This muscle will extend and rotate the thigh laterally.

Flexes Thigh, Extends Lower Leg Rectus Femoris Flexes Thigh, Extends Lower Leg Rectus femoris is located on the anterior side of the thigh. *It originates on the ilium. *The insertion is on the patella and the tibial tuberosity. *When rectus femoris contracts it will flex the thigh and extend the lower leg.

Adducts and Flexes Thigh Gracilis Adducts and Flexes Thigh The gracilis is on the medial side of the thigh. *It adducts and flexes the thigh.  

Flexes Thigh, & Rotates Thigh Laterally Sartorius Flexes Thigh, & Rotates Thigh Laterally Sartorius is a long, strap like muscle. *It originates on the anterior superior iliac spine of the ilium. *The insertion is on the medial side of the tibia. * Contraction of the sartorius flexes the thigh and rotates the thigh laterally. This is the muscle used when crossing the legs to sit on the floor.

Extends Thigh & Flexes Lower Leg Biceps Femoris Extends Thigh & Flexes Lower Leg Biceps femoris is one of the hamstring muscles. *The origin is on the ischial tuberosity. *Biceps femoris inserts on the tibia and fibula. This muscle extends the thigh and flexes the lower leg.

Plantar Flexes Foot & Flex Lower Leg Gastrocnemius Plantar Flexes Foot & Flex Lower Leg Gastrocnemius is commonly called the calf muscle. *It originates on the distal end of the femur. *The insertion is on the calcaneus bone of the foot. *It will cause plantar flexion of the foot and also flex the lower leg.

Dorsiflexes and Inverts Foot Tibialis Anterior Dorsiflexes and Inverts Foot Tibialis anterior is located on the anterior side of the tibia. *It will dorsiflex and invert the foot.