Skeletal Muscle and Nerve Tissue Flashcards
Function of skeletal muscle
voluntary movements and postural stability
Features of skeletal muscle
- nuclei
- strength, speed
- voluntary/involuntary
- fatiguable?
striated, peripheral nuclei (multinucleated)
- strong
- quick
- voluntary
- fatiguable
- large
Muscle cells are made of
myofibers/myocyte/muscle fiber
myofibrils
Myofibrils are made of
chains of sarcomeres linked together
Sarcomere
- function
- what’s it made of
contractile unit of muscle made of actin and myosin myofilaments
Fascicle (in the muscle)
- what is it
- what covers it
group of myofibers (muscle cells); surrounded by perimysium
Muscle
a group of fascicles surrounded by epimysium
5 steps smallest –> largest in muscle formation
sarcomere –> myofibrils –> myofiber –> fascicle –> muscle
Epimysium
fascial covering over muscle
Perimysium
fascial covering over fascicles
Endomysium
fascial covering over myofibers
Myosin
makes up thick filaments; consists of myosin head and myosin tail; has two heavy chains with globular heads and two light chains
how is myosin connected to the Z disk
titin proteins
Actin
makes up thin filaments; made up of G-actin monomers (globules)
What determines the length of an actin filament
Nebulin - the “ruler”
Role of tropomyosin and troponin in actin filaments
tropomyosin strands wrap between the actin strands and troponin sits on top of the tropomyosin strands to cover myosin binding sites on actin filmanets
M-line
attachment site for myosin
Z-disk
separates sarcomeres; attachment site for actin and titin
H Band
space on either side of M-line where there is no actin; shortens as muscle contract
A Band
distance from the end of one myosin head to the head of the opposite myosin
I Band
space on either side of the Z-disk where there is no myosin
What events must happen for contraction to occur
- Ca2+ is released from SR and binds to troponin causing conformational change, pulling tropomyosin away
- actin binding sites are now accessible for myosin to bind
Role of calcium in muscle contraction
binds to troponin which causes a conformational change ; troponin-Ca2+ complex pulls tropomyosin away making the actin binding sites accessible to myosin heads
What is the sliding filament mechanism and why does it occur
thin filaments slide past thick filaments (actin slides past myosin) which brings the Z disks closer causing the muscle to contract
Do actin and myosin change in length during muscle contraction
no; they simply overlap each other
Does the A band change length during muscle contraction
no
Do the H band and I band shorten during muscle contraction
yes
Characteristics of type I skeletal muscle fibers
- speed
- strength of contraction
- myoglobin levels
- fatiguability
- type of respiration
- slow
- less powerful contraction
- abundant myoglobin
- slow fatiguability
- aerobic respiration (lots of mitochondria)
Characteristics of Type IIA skeletal muscle fibers
- speed
- strength of contraction
- myoglobin levels
- fatiguability
- type of respiration
- fast
- intermediate power of contraction
- many myoglobin
- intermediate fatiguability
- aerobic respiration (lots of mitochondria)
Characteristics of Type IIB skeletal muscle fibers
- speed
- strength of contraction
- myoglobin levels
- fatiguability
- type of respiration
- fast
- powerful contraction
- few myoglobin
- rapid fatiguability
- anaerobic respiration (few mitochondria)
sarcolemma
membrane around each muscle cell
transverse (T) tubules
membrane system penetrating the muscle cell to convey electrical impulses from sarcolemma into cell
sarcoplasm
cytoplasm of a muscle cell
sarcoplasmic reticulum (SR)
tubular system acting like the smooth ER in the muscle cell; stores calcium
Terminal Cisternae
flattened sac of SR on either side of a transverse T tubule; deliver calcium
End feet
connects the T tubules with SR to allow calcium release
where do peripheral alpha motor neurons that innervate the skeletal muscle originate from
the anterior horn of the spinal cord
how many nerves innervate a single muscle fiber
one
how many muscles can one alpha-motor neuron innervate
multiple (<1)
Neuromuscular spindle apparatus
- action
- components
A: reflexive response to prevent over-stretching of a muscle
C: extrafusal and intrafusal muscle fibers
type Ia sensory nerve fibers
alpha and gamma motor nerve fibers
extrafusal muscle fibers in the neuromuscular spindle apparatus
voluntarily contract muscle
intrafusal muscle fibers in the neuromuscular spindle apparatus
sense length and rate of change of the muscle
type Ia sensory nerve fibers in the neuromuscular spindle apparatus
sense stretch and rate of change of intrafusal fibers; afferent innervation of intrafusal fibers
alpha-motor neurons in the neuromuscular spindle apparatus
receive signals from type Ia fibers and cause extrafusal muscle fibers to contract (shorten)
gamma-motor neurons in the neuromuscular spindle apparatus
receive signals from type Ia fibers and cause intrafusal muscle fibers to contract (shorten)
- continuously receiving signal from higher brain centers to stay taught and be able to detect changes
Soma/body
contains all the organelles of the neuron
nissle substance
abundant rough ER within the cytoplasm of the soma
dendrite
receives the signal from other neurons
axon hillock
connection between soma and axon; summates electrical signals received by all dendrites to transmit down axon
axon
conveys electrical impulse to synapse
synapse
transfers electrical impulse from the neuron to the target issue
fascicle (in neurons)
group of axons
a group of fascicles (in nervous tissue) is called a
nerve
what wraps around axons
endoneurium
what wraps around fascicles in a nerve
perineurium
what wraps around nerve
epineurium
mutipolar neuron
multiple dendrites and one axon
bipolar neuron
a single dendrite and a single axon branching off of one cell body
psuedounipolar neuron
one dendrite branch and one axon branch connected with a cell body branched off of the middle
schwann cell
surrounds axons and creates the myelin sheath in the PNS; wraps around one part of the axon
oligodendrocyte
surrounds axons and creates myelin sheaths in the CNS; wraps around a part of many axons
myelin sheath
circumferential layers of myelin allowing for faster signal conduction velocity
alpha-motor nerve fibers in the neuromuscular spindle apparatus provide ____
efferent innervation of extrafusal muscle fibers
gamma-motor nerve fibers in the neuromuscular spindle apparatus provide ____
efferent innervation of intrafusal muscle fibers
