Muscle Flashcards
What are the 3 types of Muscle tissue found in the body?
Skeletal
Cardiac
Smooth
Skeletal Muscle has all of the following characteristics except:
- Striated
- Conscious control
- Excitated by Self-depolarization
- Functions in locomotion and heat generation
- Excitated by Self-Depolarization is false
- Actually excited by somatic, alpha motor neurons
Cardiac Muscle has all of the following characteristics except…
- Unstriated Muscle
- Found in the heart
- Involuntary Control
- Function is to pump blood through the circulatory system
- Unstriated muscle is false!
- Cardiac muscole is striated like skeletal muscle
Smooth muscle has all of the following characteristics except…
- Nonstriated
- Involuntary control
- Excited by several different mechanisms - stretching, neuronal activity etc…
- Found only in the GI tract
- Found only in GI tract would be FALSE
- It is found throughout the body
Skeletal muscle is innervated by neurons from the [] [] of the spinal cord
Ventral Horn
What is the name of 1 skeletal muscle cell?
Myofiber
What is the organziation of a muscle fiber, from largest “cell to smallest unit”…
Myofiber > Myofibril > sarcomere > microfilament (actin/myosin)
What is the contractile unit of a myofiber?
Sarcomere
The sarcolemma is another name for the [] [] of the muscle cell…
Plasma Membrane
Transverse Tubules
- [] of the sarcolemma
- Connect the myofiber to the []
- Allow for the quick delivery system for the spread of [] [] to the skeletal muscle cell
- Closely associated with the [] [] which spreads throughout the entire cell
- Invaginations
- extracellular
- action potentials
- sarcoplastic reticulum
What is the thick filament in a myofibril and what is the thin filament?
- thick = myosin
- Thin - actin
[] [] is the intracellular storage site of Ca2+ for T-tubule usage?
Sarcoplastic Reticulum (SR)
Myosin is formed by…
2 [] [] of myosin that form the head, neck, and tail
Heavy Chains
How many heads does Myosin have?
What binding sites are on the myosin head?
- 2 heads
- Each head has an actin binding site
- Both have ATPase sites which hydrolyze ATP
- Both have 2 Light chains
What are the 2 light chains on each of the myosin heads?
- Alkali Light chain - serves a structural role
- Regulatory myosin light chain
- regulates the ATPase capability of the myosin head
What molecules make up the double helical actin structure in muscle cells?
- G-actin molecules come to gether to make F-Actin molecules
- F-actin chains make the double helix structure
What 2 regulatory proteins are on actin that inhibit/prohibit muscle contractions?
- Tropomyosin
- Troponin
What are the binding sites of Troponin and what does each site bind?
- TnC - binds to calcium
- TnT - binds to tropomyosin
- TnI - binds to actin and inhibits actin/myosin interaction
Which actin regulatory protein physically blocks the binding of acting to myosin?
Which actin regulatory protein removes the barrier stopping acting/myosin binding?
- Tropomyosin
- Troponin
What is the sequence of events that removes tropomyosin from the myosin binding sites on the actin molecule?
- Ca2+ binds to the TnC subunit of troponin
- Conformational change in troponin
- This conformational change moves tropomyosin out of the way
- Myosin can bind to Actin
This portion of the the sarcomere stretches in between adjacent A-Bands…
The I band
The I-band consists of only [] filament, or [], and stretches between two adjacent []
- thin filament
- Actin
- sarcomeres
[] - [] anchor points for the thin filaments and the boundaries for the sarcomeres…
Z-Discs
The []-zone contains only thick filaments and does not overlap with [] filaments
- H-Zone
- Thin Filaments
The [] - band consists of the full thick filament and does slightly overlap with the thin filament…
A-band
The sarcomere’s thick/thin filaments are set up in a [] array - [] thick filaments surrounded by [] thin filaments
- Hexagonal Array
- 1 Thick
- 6 Thin
Proteins like dystrophin, titin, nebulin play a key role in maintaining the structure of the []
sarcomere
The sarcomere stretches from [] to []
Z-disc to Z-disc
During contraction, myosin pulls actin towards the…?
M-line
During contraction, do actin and myosin units get smaller or larger?
- Neither!
- Actin and myosin filaments do not change size during the contraction
During skeletal muscle contraction in which the sarcomere shortens, will the length of each of the following componenets increase, decrease, or stay the same?
- A-Band
- I-Band
- H Zone
- Z Disc to Zdisc
- Length of Myosin
- Length of Actin
- A-Band - Same
- I-Band - decrease
- H Zone - decrease
- Z Disc - decrease
- Length of Myosin - same
- Length of Actin - same
What is the smallest function motor unit?
- 1 alpha motor neuron and all of the myofibers that it innervates
What would require a more fine motor control - or which of the following would require a greater ratio of motor neurons/myofibers?
Muscles in the eye or Muscles that control posture
- Muscles in the eye receive basically, a 1-to-3 ratio of neuron to myofiber. So their ratio would be larger
- Posture muscles require more motor units becuase it requires more force
What is the difference between ligand gated cation channels and nicotinic cholinergic receptors in the Somatic Nervous system?
- Psyche
- There is no difference. They are the same thing on the motor end plate.
Are there any fast acting Na+ channels on the motor end plate?
No.
There are cation channels for Na+ influx and K+ eflux
At the motor end plate, what is larger at the cation channels, Na+ influx or K+ eflux?
What does this lead to?
- Na+ influx is greater
-
depolarization of the area
- (Not an action potential though)
What enzyme digests acetylcholine in the synaptic cleft?
Acetylcholinesterase
T/F
The alpha motor neuron can recycle unused acetcholine from the synaptic cleft?
False!
- The alpha motor neuron has specific channels for the reuptake of choline
- Choline is left in the synaptic cleft after acetylcholine aceylates its receptor protein
Another name for the depolarization of the motor end plate is the [] ?
EPP - End Plate Potential
What are the 3 elecrical events that must occur for a muscle cell to be succesfully stimulated?
- Motor Neuron action potential
- EPP, end plate potential at the motor end plate
- Muscle Action Potential
What causes the after-hyperpolarization in muscle cell action potentials?
- False
- There is no after-hyperpolarization
What causes the difference in the rapid depolarization slope of action potentials and muscle action potentials versus EPPs?
- The steep upwards slope of AP and Muscle AP is caused by the rapid depolarization of membrane causing voltage-gated fast Na+ channels to open.
- The EPP does not have access to fast Na+ channels at the motor end plate.
- It is still caused by Na+ though, just not as rapid
What causes the MEPPs (miniature end-plate potentials) on the EPP curve?
- 1 vesiclein the alpha motor neuron randomly releases some Ach into the synaptic cleft.
- This Ach binds to their receptors and triggers a “test” run to make sure everything is working
- at least that is the hypothesis.