lecture 2 muscles Flashcards
3 types of muscle
skeletal
smooth
cardiac
make up of muscles
contractile proteins
actin
myosin
proteins specialized in force delivery
ATP production
for muscle to work you need
communications: nerves
energy
structural support
contractile proteins
whole muscle is surrounded by ___
epimysium
Fasicle is surrounded by ___
perimysium
muscle fiber is surrounded by ___
endomysium
make up of a muscle from outside to inside
epimysium
-muscle (serveral fascicles)
perimysium
-fascicle (several muscle fibers)
endomysium
-muscle fiber
sarcolemma (plasma membrane of muscle fiber
myofibril- chain of sarcomeres
myofilaments
the plasma membrane of the muscle cell/fiber
sarcolemma
red blood cell are how big? Can you see them with a light microscope?
7 micrometers
yes
can you see myofibrils with a light microscope?
no
skeletal muscle has __ nucleus
many
nucleus of skeletal muscle are at the ___ of the cell
outside
what cells in skeletal muscle can divide and repair and regenerate?
satellite cells
live on the outside, moves inside when muscle is injured, fixes things then goes back out
satellite cells lie under the ___ but outside the ___
basal lamina (endomysium)
outside the sarcolemma (plasma membrane)
why can’t muscle cells fix themselves?
mature muscle cells are post mitotic, unable to divide
deep fascia (dense CT) that envelopes entire muscle and becomes less flexible with aging
epimysium
another name for endomysium
basal lamina
muscle cells form a ___ syncytium, sheathed by ___ layers of connective tissue. The CT serves as a pathway for ___ and ___ to reach individual muscle cells
multinucleated
three
vessels
nerves
single motor neuron and all the muscle fibers it innervates
motor unit
small motor units results in ___
fine control
large motor units occur in ___
large, powerful muscles that do not need fine control
1 neuron= many muscle fibers
each skeletal muscle contraction is initiated by an ___ from an alpha motor neuron
action potential
place where nerve interacts with muscle fiber
neuromuscular junction
there is ___ point/s of connection between a muscle fiber and its nerve
one
neuromuscular junction
motorneuron ends at the ___, where the signal is transferred from the nerve to the muscle across the ___
motor end plate
synaptic cleft
synaptic cleft
invagination on the surface of the muscle cell coated with basal lamina.
acetylcholine is released from the motor neuron into the synaptic cleft- binding to ACh receptors, which causes a depolarization in the sarcolemma of the muscle cell
there is a __ number of nuclei at the neuromuscular junction
high
highly active area of the muscle cell/fiber
Muscle Triad
T tubules
2 sarcoplasmic reticulum
action potential across a muscle travel across the sarcolemma and down into the ___. This releases ___
T tubules
Calcium (Ca2+)
Where calcium stores live in muscle fiber
sarcoplasmic reticulum
release calcium = muscle contracts
take back calcium= calcium ATPase Pumps= muscle relaxes
skeletal muscles have __:
__ T tubules and ___ SR
and cardiac muscles have ___:
__ T tubules and ___ SR
Triads
1 and 2
Diads
1 and 1
___ are sarcoplasmic reticulum proteins which are linked to the depolarization of T-tubules to release calcium
dihydropyride receptor
Ryanodine receptor
___ will bring calcium back into the sarcoplasmic reticulum
calcium ATPase pump
a muscle cell/fiber is composed of ___
myofibrils
a myofibril is composed of a repeating contractile unit known as a ___.
sarcomere
the ___ is the basic contractile unit of striated muscle
sarcomere
the sarcomere is composed of ___ and ___.
myofilaments
thin filaments: actin
thick filaments: myosin
what is z disk
border of sarcomere, where thin filament, actin align
what is I band
thin actin filaments only
-will reduce when muscle contracts
What is A band
thick myosin filaments
the whole length of thick myosin filaments, has zone of overlap with actin
What is H band
part of myosin, thick filament that does not bind with actin
center part of sarcomere
What is M line
center of sarcomere where myosin filaments line up
thin filaments
actin
=globular protein called G-actin
G actin form chains of F actin, two chains of F actin wrap together and create a double helix.
Tropomyosin sit in the groove of the two actin strands- extends the length of 7 actin monomers and binds the troponin complex
- *Troponin** - 3 subunits
- site of anchoring for myosin, thick filaments
anchored to the Z-disk
__ consist of 2 long proteins that sit in the groove between two actin strands
tropomyosin
consists of two nearly identical alpha helicl polypeptides twisted around each other, tropomyosin runs in the groove formed by F-actin strands, Each molecule of tropomyosin extends for the length of 7 actin monomers and binds the troponin complex
Troponin
Troponin T: bind troponin to tropmyosin
Troponin I: binds to actin, inhibits myosin from binding to actin by covering the binding site
Troponin C: binds Ca2+
how does Calcium work on actin
calcium binds to TN-C (troponin-C), it triggers a conformation change in troponin allowing for the myosin cross bridges to interact with actin
Thick filaments
myosin
thick filament is composed of 200-300 myosin molecules
anchored to the M line
paired head( cross bridging) and tail (self assembly region) coiled around each other
Head has an actin binding site as well as an ATP binding site
Head of myosin has a ___ binding site and a ___ binding site
actin
ATP
light area of sarcomere in electron microscope is the ___
I band where thin filaments are
Z line connects two sarcomeres together
_ bands and __ zone shrink during contaction
I band (thin only)
H zone (myosin only)
Z line/disk/band
end of sarcomere where actin attaches
A band
A stands for
A stands for “anisotropic”
I in I band stands for
isotropic
creatine kinase which helps for ATP is found in the __ band of the sarcomere
H
__ keeps thick filaments in line
titin
titin
extends from the Z disk to the M line- keep myosin in line, ends are coiled/stretchy will stretch and contract
___ will keep actin in line
nebulin
nebulin
extends from the Z band along the length of actin filament, keep actin inline
___extends from the sarcolemma between the myofibrils helping maintain the conformation of the fibers during contractions
desmin
desmin
extends from plasma membrane of muscle fiber (sarcolemma)
keep myofibrils in line
Force Delivery
proteins that deliver force from sarcomere to tendon
Cardiac muscle
striated
intercalated discs
central nucleus
diads instead of triads
purkinje fibers
bundle of his
intercalated dics
allow contraction to go from cell to cell quickly, found in cardiac muscle in between cells
allow transmission of the electrical signal to the next cardiac cell to stimulate contraction.
specialized cardiac cells that aid in the terminal conduction of the action potential to depolarize cardiac muscle
purkinje fibers
smooth muscle
sheets -covered by epithelium or endothelium based on where it is
bundles in eyes
two directions- inner circular layer, outer longitudinal layer
spindle shape (long stretched out)
not striated- thin and thick lined up randomly throughout cell to allow force contraction when empty or stetched
central nucleus
connected to each other by gap junctions
gap junctions in smooth muscles allows ___
synchronized overall muscle contraction
smooth muscles lack ___ and ___
sarcomeres and troponin
Most of the calcium ions initiate the contraction of smooth muscles from ___
outside the cell, not within
contractile proteins
generate tremendous forces that can not be transmitted through a normal cell’s plasma membrane or basement membrane.
To enable this force transmission, there is a system of proteins which deliver the force from the myofibrils through the sarcolemma and on to the endomysium.
what is the largest contractile protein
dystrophin
part of the dystrophin complex of proteins (also known as the costamere).
Dystrophin is an intracellular protein which connects to the myofibrils and extends to the sarcolemma, where it is attached to about 5 other smaller proteins which span the sarcolemma and pass the force on to the endomysium and then on to the tendons/bone.
another name for dystrophin complex of proteins
costamere
mutation in dystrophin protein
Duchene’s muscular dystrophy
makes the dystrophin protein unable to transmit force effectively and ultimately leads to the muscle degeneration seen in muscular dystrophy.
mild form of muscular dystrophy
becker’s dystrophy
when there is a defect in one of the protein in the dystrophin complex of proteins other than Dystrophin
how heart pumps
The atrial contractions, which occur first, push the blood through the bicuspid or tricuspid valves.
second: push the blood from the base of the ventricles upwards towards and through the valves to the aorta or pulmonary artery.
why does the heart have more mitochondria?
heart muscle must be very resistant to fatigue, so having a ready supply of energy is really imperative to its health.
why is smooth muscle disorganized, not have sarcomeres like cardiac and skeletal?
smooth muscle must undergo huge length changes and still generate force
smooth muscle lack ___ and ___
smooth muscle lacks the troponin tropomyosin system to control contraction.
