Smooth muscle Flashcards
Muscle contracts two ways. What are those ways?
Isotonically: same strength
-Force generated is sufficient to move load
Isometrically: same length
-Force generated is insufficient to move weight placed on muscle
What is preload and afterload?
Preload is stretch
Aferload is how much you have to lift
Length tension relationship?
As you increase muscle length you get more force generated. Actin myosin have better connection.
How is skeletal muscle preload set?
Skeletal muscle is already set close to the optimal preload length.
What is the force-velocity relationship.
Preload is set afterload is changed
- Velocity of shortening is measured at variety of afterloads
- Load increases, speed decreases
- Slower contraction gives more cross bridges more time to form
Innervation of smooth muscle can happen in 2 ways: what are they?
Single unit: GI, bladder, uterus -Cells linked together by gap junctions -little innervation Multi-unit: Iris, vas deferens -each cell has its own innervation -function as distinct muscle cels
This is smaller than skeletal muscle and spindle shaped.
Smooth muscle
3 different ways calcium gets into cell.
Gq mediated system: doesn’t change membrane polarity, goes to SR and dumps Calcium there.
Depolarization: spread through gap junctions
Ligand gated channels: hormones or neurotransmitters open channels and let calcium in
All calcium for smooth muscle contraction comes from the __.
SR
How is calcium release unique in smooth muscle?
Calcium induced calcium release.
What is difference between tonic and phasic contraction?
Phasic contractions have single spike like skeletal muscle
Tonic contracitons single spike but maintain force because of “latch state” of smooth muscle myosin
For myosin to let go it has to bind ______.
ATP
Unphosphorylated myosin has ____ affinity for ATP.
low
Some differences between smooth and striated muscle?
Non-striated, no sarcomere Cycling of cross bridges is much slower in smooth muscle Longer contractions Can latch Much lower metabolic demand CICR Can have gap-junction Activated by circulating hormones
Very hard to over stretch smooth muscle. Why is this important?
Generates same maximal force. It will generate maximal force at any length.
What is the force-velocity relationship?
Velocity of contraction increases with % of myosin phosphorylated. Increased load increases Ca2+ flux, increases MLCK activation.
Calcium has very little affect on resting membrane potential. But has big affect on what?
Has big impact on action potentials.
This increases threshold but is less excitable?
Hypercalcemia
stronger contractions
This threshold is less negative.
Hypocalcemia
weaker contractions
What are big chunky Y shaped cells?
Cardiac muscle
There are a lot of gap junctions at _____________.
intercalated disk
What cardiac refractory period. No conducted potential can generate an AP (AP will fire but nor go anywhere)
Effective Refractory Period
What cardiac refractory period. AP can fire if a greater than normal stimulus is provided
Will have a shortened plateau
Relative Refractory Period (RRP)
What cardiac refractory period. Cell is MORE excitable than normal. Has not yet reached full RMP.
Supranormal Period (SNP)
