Lecture 5: Muscles Flashcards
Describe a skeletal muscle
Bundles of long, cylindrical multinucleated cells with cross-striations
Describe cardiac muscle
Elongated branched individual cells with cross-striations that are parallel to one another
Describe a smooth muscle
Collection of fusiform cells without cross-straiations
Skeletal muscles form from a fusion of what kind of cells?
Myoblasts
What are intrafusal fibers innervated by?
Sensory: Ia, II
Motor: (y)
What are extrafusal fibers innervated by?
Motor: alpha- motor neurons
What do intrafusal fibers do
They are the proprioceptive fibers of muscle spindles
What do extrafusal fibers do?
They produce tension
What are the three types of skeletal musclefibers?
- slow fibers, red (type I)
- fast glycolytic fibers, white (type II-b)
- fast oxidative fibers (type II-a)
What muscle fibers are specialized for long-term contraction w/ mitochondrial performance and oxidative?
Type I
What muscle fibers contract fast, produce tension, and fatigue the fastest (ATP use)?
Type II-b
What muscle fibers fatigue the fastest?
Type II-a
Compare the velocities of type I and II muscle fibers
I: slow
II: fast
What is the tension generated by muscle fibers proportional to?
the cross-sectional area
Golgi tendon organs are what kind of nerve fibers? Muscle Spindles?
Group 1b afferent
Group Ia afferent
Describe the tendon reflex
It inhibits the muscle from contracting too strongly so it doesnt tear a tendon or pull loose from muscle or bone
Name the breakdown from muscle to filaments.
Muscle Fasicle (made up of group of muscle fibers) Fiber (made up of myofibrils) Myofibrils (composed of sarcomeres) Sarcomeres (basic unit of contraction)
What is the ratio of troponin-tropomyosin complexes to actin molecules?
1:7
What are the components of thick filaments?
2 heavy chains, 4 light chains
What anchors thin filaments to Z-line?
alpha actin
What anchors thick filaments to Z line?
Titin
What is the molecular ruler for thin filaments?
Nebulin
What are two proteins that keep thick filaments in register?
myomesin and C-protein
What is the actin capping protein responsible for regulating the length of thin filaments
Tropomodulin
What keeps myofibrils in registter during contraction?
Desmin
Where does calcium bind to cause dissociation of Troponin I from actin?
Troponin C
Muscle contraction is a result of?
thin filaments sliding over thick filaments, pulling Z lines closer
What is rigor?
absence of ATP which causes the myosin heads to remain bound to actin
What part of the protein complex anchors thin filaments in a muscle fiber to the sarcolemme and basal lamina?
Dystrophin
What pathology results from no dystrophin being synthesized? What is a characteristic sign?
Duchenne Muscular Dystrophy – Gower’s sign (using arms to help stand)
What pathology results from partially functional or reduced amounts of dystrophin being synthesized?
Becker’s Muscular Dystrophy
What protein suppresses muscle growth and can be used as potential theraphy for DMD or BMD?
Myostatin
This hormone is produced and secreted by atrial myocytes. It inhibits renin and aldosterone secretion and relaxes vascular SM.
Atrial Natriuretic Factor (ANP)
What is released from ventricles in response to left ventricular defect?
Brain natriuretic factor
Corkscrew nuclei is characteristic of what tissue?
Smooth muscle
In smooth muscle, what does Ca+ bind to, to in itiate contraction?
calmodulin –> myosin light chain kinase
What are three characteristics of a cardiac muscle under a microscope?
- myonuclei
- fibroblasts
- intercalated disks (communition)
