BIOL-106 Lecture Notes - Lecture 2: Phosphocreatine, Lipolysis, Autonomic Nervous System
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Muscles are organized into three basic types:
1. Striated: Skeletal muscle facilitates movement by applying forces to
bones and joints through its contraction. They are generally under voluntary
control. Muscles have an origin; a thick portion of the muscle between the
insertion and origin is called the muscle belly or gaster and a tendon.
2. Cardiac: Cardiac muscle is an involuntary striated muscle found
exclusively in the heart. Cardiac muscle has unique properties; it stimulates its
own contraction without the required electrical impulse from the central
nervous system via special pacemaker cells in the sinoatrial node.
3. Smooth: Smooth muscle is an involuntary non-striated muscle found in
the walls of hollow organs such as the bladder, and in blood vessels. Smooth
muscle can be directly stimulated by the CNS or can react to hormones
secreted locally, such as vasodilators and vasoconstrictors.
Skeletal muscle fiber
•Anatomy: Skeletal Muscle Fibers are made up of many myofibrils
surrounded by sarcoplasmic reticulum. The sarcolemma is on the outside of
the muscle fiber and contains many nuclei.
•Sarcomere: The dark striations of skeletal muscle are made up of a lattice
of thick and thin filaments, which are formed into a functional unit of contraction
known as the sarcomere. Sarcomeres are the basic unit of muscle, made up of
actin and myosin.