BIO* - Biology BIO* M121 Lecture Notes - Lecture 15: Soleus Muscle, Skeletal Muscle, Cardiac Muscle
9 Jun 2020
School
Department
Course
Professor
Charlie Kent
Bio M121
Summer 2017
General Bio
● Classes of Muscle in Vertebrates
● Smooth Muscle
○ Smooth muscle cells are essential to the functioning of blood vessels,
reproductive system, bladder…
○ Smooth muscle cells lack sarcomeres
■ Actin filaments are arranged obliquely in the cytoplasm, and are
anchored in the plasma membrane or cytosol
■ Myosin filaments crosslink the actin
● Activation of myosin pulls the filaments, contracting the
plasma membrane inward
○ Parasympathetic
■ ACh stimulates contraction of smooth muscle in the stomach and
intestine
○ Sympathetic
■ Epinephrine and norepinephrine inhibit contraction of smooth
muscle in the stomach and intestine
● Cardiac Muscle
○ These highly branched cells are directly connected end to end via
intercalated discs
○ Parasympathetic
■ Neurons release ACh onto the heart
■ This slows down the rate of depolarization of cardiac cells (and
thus slows heart rate)
○ Sympathetic
■ Epinephrine is released onto the heart, increasing heart rate and the
force of cardiac muscle contractions
■ Overall, more blood is pumped from the heart
● Skeletal Muscle
○ Skeletal muscle is voluntary and must be stimulated by somatic neurons
■ Not all skeletal muscle fibers have the same contractile properties
■ Relative proportion of different fiber types, organization of fibers
within the muscle, and how the muscle is used
● Skeletal Muscle Fiber Types
○ Different fiber types are present in all skeletal muscles, but their relative
abundances differ from muscle to muscle
○ Slow fibers
■ Specialized for endurance, fatigue slowly
■ Examples: soleus muscle in the back of the calf (helps you stand
upright), “dark meat” of chicken legs
Document Summary
Smooth muscle cells are essential to the functioning of blood vessels, reproductive system, bladder . Actin filaments are arranged obliquely in the cytoplasm, and are anchored in the plasma membrane or cytosol. Activation of myosin pulls the filaments, contracting the. Ach stimulates contraction of smooth muscle in the stomach and intestine. Epinephrine and norepinephrine inhibit contraction of smooth muscle in the stomach and intestine. These highly branched cells are directly connected end to end via intercalated discs. This slows down the rate of depolarization of cardiac cells (and thus slows heart rate) Epinephrine is released onto the heart, increasing heart rate and the force of cardiac muscle contractions. Overall, more blood is pumped from the heart. Skeletal muscle is voluntary and must be stimulated by somatic neurons. Not all skeletal muscle fibers have the same contractile properties. Relative proportion of different fiber types, organization of fibers within the muscle, and how the muscle is used.
