Lecture 17-18- Muscle Physiology Flashcards
The outer layer of the sarcolemma attaches to the…
Tendon
Is actin or myosin the Thin Filament?
Actin
A-band
gray area with actin and myosin
M line
inside the H zone, middle of the myosin/sarcomere
What structure intertwines with actin?
Tropomyosin, with troponin bound
What does troponin bind?
calcium
What does SR stand for?
Sarcoplasmic reticulum
What does the SR surround?
myofibrils
What does the SR store until muscle contraction
Calcium
What are invaginations of the SR that aid in depolarization?
T tubules
Order of events leading to muscle contraction after Ach is released at NMJ
Ach activates nicotinic receptors on sarcolemma
Na channels open causing depolarization
Ca released from SR
COntraction
If there is less Ca available (milk fever) then what happens at the NMJ
less Ach is released –> less depolarization –> less contraction
What is parturient paresis in dogs called?
Puerperal tetany
Why is milk fever different between dogs and cows?
Dog cell membranes become more permiable to Na during hypocalcemia, aiding in depolarization
what happens when troponin binds to Ca
allows myosin and actin to bind
What happens to ATP when actin and myosin bind?
ATP is hydrolyzed and actin is pulled
How are ADP and P released from myosin?
ATPase
Why does rigor mortis occur?
There is no ATP to release contraction
What are Type I muscle fibers?
Slow twitch
What are the qualities of slow twitch fibers?
Darker color
Myoglobin
more mitochondria
More aerobic
What are Type II muscle fibers?
Fast twitch
What are qualities of Type II muscle fibers?
Larger
Extensive SR
fatigue quickly
More powerful
What is the energy source of slow twitch fibers?
Oxidative phosphorylation
What are the two classes of Type II fibers?
A: intermediate between slow and fast
B: traditional fast twitch
Endurance canine athletes use what for fuel?
Fatty acids
Sprinters have more of what type of muscle fiber?
Type II
What is a motor unit?
LMN and all of the innervated muscle fibers
Movement begins with small or large motor units?
small
Is the sarcoplasmic reticulum more developed in cardia muscle or skeletal muscle
Skeletal muscle
What type of muscle cell does not have T tubules?
Smooth muscle
What type of muscle cell can be innervated by more than one neuron?
Smooth muscle
Characteristics of Multiunit Smooth Muscle
Autonomic neuron intwines around each muscle cell
Delicate movement
Each fiber can contract independently
Characteristics of Single unit smooth muscle
Contraction of many cells at once (peristalsis)
cell membranes joined by gap junctions, allowing action potentials to travel between
What are calveoli
invaginations in smooth muscle SR similar to T tubules
Can smooth muscle receive inhibitory signals?
No
What do smooth muscle cells have instead of NMJ?
Varicosities allowing large areas of smooth muscle to be affected at the same time
What does smooth muscle have instead of troponin/tropomyosin?
Calmodulin
What happens to smooth muscle once calcium binds calmodulin?
Activation of the myosin light-chain kinase
What does smooth muscle use instead of ATP to cock myosin heads?
Myosin light-chain kinase
What dephosphorylates the myosin light-chain kinase?
myosin phosphatase
