Muscle Physiology Flashcards
3 general functions of muscle physiology:
- movement
- heat production
- posture
3 technical functions of muscle physiology:
- excitability
- contractility
- extensibility
Ability to be stimulated
Excitability
Ability to contract or shorten
Contractility
Ability to extend or stretch and return to resting length after contraction
Extensibility
Muscle fiber (muscle cell)
Myocyte
Myocytes have more than one _______ due to each fiber being made up of multiple cells combined into one
Nucleus
Stem cells that can fuse with myocytes during strength training to make bigger muscle fibers
Satellite cells
____ can become active post injury to produce more muscle fibers.
satellite cells
muscle cell plasma membrane
sarcolemma
muscle cell cytoplasm
sarcoplasm
muscle cell smooth ER
sarcoplasmic reticulum
_______ is sandwiched between sacs of the sarcoplasmic reticulum
Triad T-tubule
The cytoskeleton of the muscle fiber
myofibrils
Bundles of very fine filaments packed closely together that extend lengthwise along mm fiber
myofibrils
contractile unit that extends between 2 z discs
sarcomere
extensions of sarcolemma (the electrical wiring)
T tubules
protein that binds O2 in sarcoplasm
Myoglobin
regions of dense protein that separate sarcomeres
z discs
The 3 kinds of protein that make up a myofibril:
- contractile
- regulatory
- structural
____ and _____ are contractile proteins.
Myosin and actin
____ and ____ are regulatory proteins.
- tropomyosin
- troponin
several kinds of proteins that assist to stabilize the position of thick and thin myofilaments are this kind of protein
structural
thin, twisted protein strands that have sites that attract myosin heads
actin
thick fibers that have “heads” that cross bridge to actin active sites
myosin
thin strands that block actin active sites
tropomyosin
globular proteins that hold tropomyosin in place
troponin
specialized nerve cells that release ACh
motor neuron
folded aspect of sarcolemma where motor neuron connects
motor endplate
____ binds to receptors on mm fiber
ACh
junction between motor neuron and motor endplate
neuromuscular junction
- Signal travels down motor neuron
- ACh released from end of motor neuron into synaptic cleft
- ACh binds to receptors on motor endplate
- Electrical impulse is transmitted to the sarcolemma
Excitation process of the sarcolemma
- impulse travels through T tubles to sacs of ER
- Ca++ released into sarcoplasm and binds to troponin
- Tropomyosin molecules shift and expose active actin sites
- Myosin bridges and binds to actin to pull actin filaments toward center of sarcomere
- Myosin heads release and bind to next active site and pull again which results in shortening
Contraction
muscle fibers contract to __% of their starting length.
80
- SR starts pumping back Ca++ into its sacs almost immediately after releasing them
- Ca++ removed from troponin molecules shutting down contraction
Relaxation
If no nerve pulse follows after contraction, the muscle ____.
relaxes
A small amount of ____ is present inside resting muscle fibers
ATP
If more ATP is needed the muscle has 3 ways to produce it:
- from creatine phosphate
- anaerobic glycolosis
- aerobic respiration
consists of a somatic motor neuron ans all the skeletal muscle fibers it stimulates
motor units
a single somatic motor neuron comes in contact with an average of ____ skeletal muscle fibers
150
containing only a few muscle fibers per neuron
fine motor
large scale and powerful movements have many fibers per neuron
gross motor
brief contraction of all muscle fibers in a motor unit in response to a single impulse
twitch contraction
gradual, steplike increase in strength f contraction when series of twitch contractions occur about a second apart
Treppe
A muscle contracts with more force after it has contracted a few times. This is called
Treppe
smooth, sustained contractions, also called multiple wave summation.
Muscle doesn’t have time to relax before the next contraction starts
Tetanic contractions (Tetanus)
Tension is not sustained at a constant level
incomplete tetanus
continual, partial contraction in a muscle organ. A small number of fibers in a muscle contract to produce tautness. Motor units fire in relays to achieve this tone.
Tonic contraction
small amount of tautness due to weak, involuntary contraction of motor units.
muscle tone
4 factors that contribute to graded strength principle:
- metabolic condition
- recruitment of motor units
- effect of muscle length on strength
- effect of load on strength
_____ activity is separate from muscle contraction but can positively and negatively effect contraction
Metabolic
maximal strength a muscle can develop bears a direct relationship to the initial length of its fibers
length-tension relationship
the heavier the load the stronger the contraction. This is…
effect of load on strength
muscle shortens, tension stays the same
concentric contraction
muscle lengthens, tension stays the same
eccentric contraction
muscle length does not change, tension changes
isometric contraction
type of muscle fiber that relies on oxygen to produce ATP, highly vascular and fatigue resistant, high concentration of myoglobin, myosin is slow acting and ATP production is able to keep up.
found in postural and endurance type muscles
slow oxidative fibers (red)/ slow twitch
rely on oxygen and glycogen o produce ATP, some myoglobin and vascularity, myosin is moderately fast but more fatigue resistant than fast twitch fibers, sprint muscles
fast oxidative-glycolytic fibers/intermediate fibers
relies on glycogen to produce ATP, low concentration of myoglobin and decreased vascularity, myosin is fast so rapid depletion of ATP, short duration contractions
found in muscles of fingers and eyes
Fast twitch (white fibers)
