Exam 2: Movement and Muscle Physiology Flashcards
In vertebral skeletal muscle, how many neurons code for one motor unit?
one
In invertebrate skeletal muscle, how many neurons code for one motor unit?
multiple
What is the result of having multiple motor neurons controlling one motor unit?
Results in signal crossing
What are central pattern generators (CPG)?
A repeating pattern of rhythmic movement caused by a closed negative feed backlook
What is a cellular oscillator?
An individual neuron that generates a temporally patterned activated
What is a network oscillator?
When multiple neurons interact to generate a patterned activity
What is a closed-loop model?
When a negative feedback loop maintains a stable cyclic pattern of activity
How does network oscillation occur?
An activate neuron inhibits the following neuron; the next neuron is turned on when the previous neuron is inactivated
Is the CNS involved in central pattern generation?
No, but it modulates CPG output based on sensory information
How are muscle cells structure within a skeletal muscle fiber?
muscle cells are long and multinucleated
Why is excitation-contraction coupling considered “coupled?”
Because two membrane systems are involved in excitation
What are the two membrane systems involved in excitation?
Transverse tubule membrane and sarcoplasmic reticulum membrane
What is the function of transverse tubules (T-tubules)?
continuation of sarcolemma that extends into interior of muscle fiber
What is the sarcolemma?
The membrane of a skeletal muscle cell
What is the sarcoplasmic reticulum?
An organelle in skeletal muscle used to store Ca2+
What is sliding-filament theory?
Muscle contraction is caused by sliding myosin and actin filaments within sarcomeres
What are sarcomeres?
A segment of a muscle fiber extending between Z-discs
How are action potentials in skeletal muscle cells generated
Cholinergic neurotransmitters are expressed by the motor neuron and depolarize the sarcolemma
What happens once an action potential is generated in a skeletal muscle cell?
The action potential travels down the T-tubule and activates dihydropyridine receptors in the sarcolemma
What occurs once dihydropyridine receptors in the sarcolemma are activated by an action potential?
dihydropyridine open ryanodine receptors in the sarcolemma which release Ca2+ into the sarcoplasm?
Why do dihydropyridine receptors open ryanodine receptors?
Because they are attached
What is the function of troponin?
To bind pull on tropomyosin when Ca2+ is present and reveal action binding sites?
What is the function of tropomyosin?
To block actin binding sites when muscle cells are relaxes
What does Ca2+ do once release from the sarcoplasmic reticulum?
Binds to troponin to pull tropomyosin away from actin binding sites
What causes myosin heads to bind to actin?
Hydrolysis of ATP cocks the myosin head in position to form a cross bridge with a FREE actin binding site?
What are cross bridges in reference to sliding filament theory?
The connection between a myosin head and actin binding site
Which muscle filament is considered the thick filament?
Myosin
Which muscle filament is considered the thin filament?
actin
What causes filaments to physically slide?
Release of inorganic phosphate by the myosin head causes a power stroke that cocks the myosin head
How is ADP removed from a myosin head?
It is released when the myosin head is cocked by release of inorganic phosphate
How is the position of a myosin head reset?
ATP binds to the head and separates it from actin
What is polyneural intevation?
When multiple motor neurons are responsible for one muscle unit
Why can’t arthropods use action potentials for their nervous systems?
Polyneural intervation causes too much overlap for action potentials to be successful at propagating coherent signals
What triggers levels of muscle tension in arthropods?
Degree of depolarization increases muscle tension
What neurotransmitter is used to excite arthropod muscular tissue?
glutamate
What function does glutamate perform in arthropod neurons?
Opens Na+ channels and increase degree of depolarization
What neurotransmitter is used to inhibit depolarization of an invertebrate neuron?
GABA
How does GABA inibit depolarization?
Opens Cl- channels to hyperpolarize the membrane
What are octopamine and tyramine and what do they do?
Neurotransmitters that tell skeletal muscle to source energy from glycogen
How are octopamine and tyramine affected during migration?
Inhibited to increase sourcing energy from lipids
What is a benefit of having only one neuron control each motor unit and one neuron able to control multiple motor units?
Allows fine tuned control
How is muscle tension increased in a vertebrate?
Frequency of action potentials and number of motor units recruited
What is isometric contraction?
the ability of muscle tissue to replace tired units with unused ones to maintain endurance
How does muscle growth (hypertrophy) occur?
More blood flow and nutrients
Larger myosin and actin filaments
More nuclei
Do muscle cells increase in number to increase muscle size?
no
What kind of respiration does endurance exercise employ? Why?
Aerobic; has the highest metabolic output
What kind of muscle fibers does endurance exercise mostly use?
Type I/slow twitch muscle fibers
What neural pattern is commonly involved in endurance exercise?
Central pattern generators
What kind of respiration does resistance exercise employ? Why?
Anaerobic; faster
How do type II muscle fibers compare to type I in endurance?
They are sensitive to fatigue
What kind of muscle fibers does resistance exercise employ?
Type II/fast twitch
How are type IIa and IIx muscle fibers different in structure/properties?
IIx has fastest Ca2+ reuptake, cross bridge cycling, and fatigues the fastest
IIa is like an intermediate of I and II
How does endurance training affect muscle fiber composition?
Increase mitochondria concentration and turns IIx fibers in IIa
What is PGC-1α1?
A transcription factor that regulates genes that affect muscle fiber endurance
How does resistance training affect muscle fiber composition?
Changes IIx fibers to IIa and increases nuclei number and myosin/actin filament size
What is PGC-1α4?
a transcription factor that upregulates growth factors and protein syntheis
How did PGC-1α1 and PGC-1α4 relate?
They are different isoforms of the same gene
How does an exercise taper affect muscle composition?
Brings back some lost IIx fiber
Why is an exercise taper beneficial?
IIx fibers can be employed when bursts of energy are needed
