Lectures 71 and 72 muscle excitation Flashcards
Skeletal muscle fibers are the result of fusion of several
mononucleated undifferentiated myoblast cells
Each skeletal muscle fiber contains one or many nuclei?
many
Motor neurons that innervate skeletal muscle originate in what horn?
ventricular/anterior
What is the sarcolemma?
the skeletal muscle cell membrane
Which filaments are “thick”?
myosin
I-bands, or light bands, contain only
actin
Overlapping ends of actin filaments are called
A-bands
What gives skeletal muscle its striated appearance?
actin and myosin bands
What are the sites of interaction between thick and thin filaments that generate force and contraction?
cross bridges - projections from the sides of myosin filaments
The Z line/disc is composed of
filamentous proteins - the non-overlapping ends of actin filaments are attached to these
What is titin?
a large protein that acts as a framework holding filaments in place
The tail of a myosin molecule is composed of 2 “heavy” chains that
spiral to form a double helix like DNA
The myosin molecule tails bundle together to form
the body of the myosin filament
What two things are essential for myosin heads to contract?
ATP and calcium
What is the initiator of contraction?
troponin
Troponin I has an affinity for
actin
Troponin T has an affinity for
tropomyosin
Troponin C has an affinity for
calcium
What are the two types of NMJ blocking agents?
nAChR antagonists (non-depolarizing) and agonists not removed efficiently
What are the two main classes of smooth muscle?
multi-unit and unitary
Multi-unit smooth muscle works in what way?
the fibers it is composed of work separately with single specific nerve innervation
T or F: unitary smooth muscle contracts as a whole
true
Does smooth muscle contain tropomyosin or troponin?
no
In smooth muscle, calcium binds to
calmadoulin
