Skeletal and Smooth Muscle Flashcards
Structure of Skeletal Muscle:
Muscle Group Fasciculi Muscle Fiber/Muscle Cell/Myofiber Myofibril Myofilaments (Actin/Myosin)
Sarcolemma
plasma membrane of a muscle fiber
Myofibril
composed of myofilaments: actin and myosin
Striations are formed by
overlapping of actin and myosin
Sarcomere
from one z-disc to another
T-Tubule
regular interval where the sarcolemma transfers the muscle cell in order to transmit action potentials
Terminal Cisterna
where Ca++ is stored in the sarcoplasmic reticulum next to the
Actin is made up of
G-actin molecules with myosin head binding sites which make F-actin strands, covered by tropomysoin
Troponin
Troponin I - attached to actin
Troponin T - attached to tropomyosin
Troponin C - attracted to Ca++
Each muscle cell is innervated by an efferent somatic motor neuron that uses Ca++ dependent exocytosis
Each muscle cell is innervated by an efferent somatic motor neuron that uses Ca++ dependent exocytosis
In skeletal muscle fibers most of the Ca++ comes from
sarcoplasmic reticulum so extracellular Ca++ levels have very little effect
In skeletal muscle fibers most of the Ca++ comes from
sarcoplasmic reticulum so extracellular Ca++ levels have very little effect
Ratio of Actin to Myosin in skeletal/smooth muscle
Skeletal: 2 Actin:1 Myosin
Smooth: 5-10 Actin:1 Myosin
Atrophy
decrease in muscle size d/t decrease in size of individual sarcomere from decrease amount of protein in myofilaments
Hypertrophy
increase in muscle size d/t increase in size of individual sarcomere from increase amount of protein in myofilaments
Hyperplasia
increase in number of muscle fibers, rare
Type Types of Smooth Muscle
Multiunit - many discrete smooth muscle fibers which contract independently (ex. ciliary muscle of eye)
Single-unit - thousands of smooth muscle fibers that form a unit and contract together (ex. GI tract)
Actin is attached to ____ in smooth muscles
dense bodies
_____ attaches one smooth muscle cell to another
dense bodies
Space between dense bodies
gap junction
Latch Mechanism
in smooth muscle the myosin head are dephosphorylated by Myosin Phosphatase, but the head may not immediately detach, can stay attached for hours and days
What dephosphorylates the myosin heads in skeletal vs. smooth muscle?
skeletal: ATPase
smooth: Myosin Phophatase
