Definitions
Sarcolemma, Sarcoplasm
Plasma membrane
cytoplasm
What is a motor unit?
A motor neuron and the muscle fibers it innervates
What does excitation-contraction coupling refer to?
Action potentials on the sarcolemma activate myofilaments
1. Action potential
2. Sliding of the myofilaments
3. Good length-tension relationship
What occurs during contraction of a muscle? (Hint: start w/ Ca2+)
Calcium ions bind to troponin, which moves the tropomyosin out of the way and uncovers the binding sites for myosin on the actin myofilaments
What is a T-tubule and what does it do?
It conveys electrical signals from the cell surface to it’s interior
What type of muscle exhibits alternating light and dark transverse bands or striations?
Skeletal muscle
voluntary striated muscle attached to bones
What is threshold regarding muscle twitches?
The minimum voltage necessary to produce an action potential
What are the five universal characteristics of muscle?
1. Responsiveness
2. Conductivity
3. Contractility
4. Extensibility
5. Elasticity
Which enzyme removes acetylcholine from receptors so stimulation of the muscle cell ceases?
Epimysium, Endomysium
Thin projections of connective tissue extending from the epimysium into the muscle to surround bundles of muscle fibers known as fascicles,
W/in each fascicle, loose connective tissue separates individual muscle fibers
What is the dense, fibrous connective tissue surrounding the entire muscle referred to as?
Epimysium
at the end of the muscle, it is continuous with the tendons and periosteum of the bone
What makes up a muscle fiber? ((2 bullets))
- A single, elongated cell surrounded by a plasma membrane, known as the sarcolemma
- It contains nuclei and threadlike structures called myofibrils, which extend the length of the fiber & dominate its interior
What are isometric contractions and how do they differ from isotonic contractions?
- isometric develops tension without changing length while isotonic develops tension while shortening (concentric) or lengthening (eccentric)
- act like a switch that starts and stops shortening of muscle cells
- the release of calcium into sarcoplasm and its binding to troponin, activates contraction
- troponin moves the tropomyosin off the actin active sites
What are myosin? Where are they located?
protein molecules on thick filaments
What is a sarcomere?
An orderly contractile unit composing actin (thin) and myosin (thick) myofilaments
What are the two types of muscle fibers?
- Type 1: slow oxidative, slow-twitch fibers
- Type 2: fast glycolytic, fast-twitch fibers
Are all muscle fibers metabolically alike?
No, but all fibers of a single motor unit are similar
What is multiple motor unit summation?
What is an end-plate potential?
Localized depolarization of the muscle fiber membrane at the neuromuscular junction
- caused by the binding of acetylcholine to receptors of the muscle cell
What are the symptoms of myasthenia gravis?
- drooping eyelids and double vision
- difficulty swallowing
- weakness of the limbs
- respiratory failure
Spastic paralysis caused by toxin of Clostridium bacteria
Lockjaw/tetanus
- blocks glycine release in the spinal cord and causes of overstimulation of the muscles
What is myasthenia gravis?
An autoimmune disease where antibodies attack NMJ and bind acetylcholine receptors together in clusters
What stops the production or maintenance of tension?
Loss of calcium from sarcoplasm, resulting in troponin-tropomyosin complex moving over the active sites