Much of this chapter in your text deals with how muscles function at the cellular level . We will NOT discuss that in this class because the cellular activity of muscle is normally covered in the Human Physiology (Biol 2420) class.
Muscles convert chemical energy into physical energy to help bones to move, hollow tubes to contract, or to pump blood. Muscles are considered organs because they are composed many different types of tissue (muscle, epithelieal, nervous, connetective, etc.)
Skeletal muscles are those muscles attached to bones and are easily seen on the body’s exterior. However, other types of muscle (smooth muscle and cardiac muscle) are found deeper in the body.
Open heart surgery Lung Heart Smooth muscle is essential for propelling materials through our internal tubes Cardiac muscle , found only in the walls of the heart, pumps blood
All muscles are excitable, contractile, elastic and extensible . This means when nerves stimulate the biceps brachii, it contracts, and the opposing triceps brachii relaxes and extends.
A muscle cell on the anterior side of the arm may extend up to 35 centimeters and have a diameter of about 100 micrometers (about the same thickness of a fine human hair). Because of their potentially extraordinary length, skeletal muscle cells are often referred to as muscle fibers . Make this addition to your notes!
Skeletal muscle functions to pull on bones to use them as lever systems, maintain posture, generate heat for temperature control, promote storage and movement of materials in the body, and to support and stabilize body walls.
(Muscle cell) Contents of muscle cell In general, a skeletal muscle is composed of layers of skeletal muscle fibers (muscle cells), blood vessels, nerves, and connective tissue sheaths that surround the muscle fibers and connect muscle to bone. Bone Note the epimysium, which is dense irregular connective tissue that surrounds the whole muscle .
( Muscle cell) (Muscle cell) Contents of muscle cell The perimysium surrounds bundles of muscle cells (fasicles) The endomysium is the innermost connective tissue layer and surrounds each individual muscle cell (muscle fiber).
The origin is usually the more proximal stationary attachment while the insertion is typically distal and is the moveable attachment.
There is extensive blood and nerve supply to the skeletal muscles
Motor neurons are also called efferent neurons because they travel away from the center of activity, which is the central nervous system. They innervate muscle fibers within the muscle.
Muscle fibers will atrophy if they are not periodically stimulated to contract. We learned earlier, that if the muscles or nerves are damaged, pulling stress on the periosteum will diminish and bone density will also decrease .
Sensory neurons are also called afferent neurons because they travel towards the central nervous system. They send impulses to the brain and spinal cord about the activity of the muscles.
WHICH OF THE FOLLOWING IS A CORRECT STATEMENT? A AFFERENT NEURONS CONDUCT IMPULSES TO THE SPINAL CORD B MOTOR NEURONS ARE EFFERENT NEURONS C RHABDOMYOLYSIS IS TREATED WITH BAKING SODA D HYPNIC JERKS ARE ASSOCIATED WITH DECREASED BRAIN FUNCTION E ALL OF THE ABOVE
Circular muscles have their fibers concentrically arranged around an opening or recess.
Pectoralis major Convergent muscles have widespread muscle fibers that converge on a common attachment site.
Parallel muscles have fascicules (bundles of muscle fibers) that run parallel to its long axis. Examples are the rectus abdominis and the biceps brachii.
Pennate muscles are so named because their tendons and muscle fibers resemble a large feather.
A lever is an elongated, rigid object that rotates around a fixed point called the fulcrum Effort arm Resistance arm
Bones are the levers, the joint is the pivot or fulcrum (F), the muscle provides the effort (E), and the resistance (R) is what is being moved. Please note that the effort (E) is truly located where the tendon attaches to the bone (lever)! Effort (E)
<ul><li>F (fulcrum) is in the middle in #1 </li></ul><ul><li>R (resistance) is in the middle in #2 </li></ul><ul><li>E (effort) is in the middle in #3 </li></ul><ul><li>Remember “FRE#1 #2 #3 </li></ul>
Atlantooccipital joint is a first class lever system
Rising onto the ball of the foot (distal ends of metatarsals) by contacting the calf muscles is an example of a second-class lever system.
Flexion of the elbow is an example of a third-class lever system. Remember, the effort (E) is where the tendon attaches to the bone (lever)!
WHICH OF THE FOLLOWING IS CORRECT ABOUT THE PROCESS OF EXTENDING YOUR TIBIOFEMORAL JOINT? A IT IS A FIRST CLASS LEVER SYSTEM B IT INCORPORATES A MULTIAXIAL JOINT C IT IS A THIRD CLASS LEVER SYSTEM D IT UTILIZES A CONDYLOID JOINT E IT IS A SECOND CLASS LEVER SYSTEM
In this instance, the triceps brachi is the agonist (prime mover)
The muscle that opposes the prime mover (agonist) is called the antagonist
The quadriceps femoris muscles composed of four distinct muscles (only three shown here as the fourth is deep) are synergistic in extending the leg at the knee joint.
Skeletal muscles are named on the basis of shape, location, attachment, orientation of fibers, relative position, or function.