GROUP 2 Flashcards
an organ system, involved majorly in the movement of the body.
muscular system
found in the heart, blood vessels, and digestive system.
muscle tissues
Every muscle is a different organ made of (4)
blood vessels
skeletal muscle tissue
nerves
tendons
Importance
fundamental for promoting physical health, preventing injuries, enhancing athletic performance, and facilitating rehabilitation.
types of muscles
- smooth (present only in the heart; spindle-shaped)
- cardiac (within organs such as the intestines, the blood vessels and the stomach; cylindrical, branched)
- skeletal (body parts that are connected to the bone; long, cylindrical)
Individual muscle cells that makes up the skeletal muscles
muscle fiber
Many oval nuclei can be seen just beneath the plasma membrane, which is called
sarcolemma
The nuclei are pushed aside by long ribbonlike organelles which nearly fill the cytoplasm
myofibrils
give the muscle cell as a whole its striped appearance.
light and dark bands
The myofibrils are actually chains of tiny contractile units called ________, which are aligned end to end like boxcars in a train along the length of the myofibrils.
sarcomeres
There are two types of threadlike protein _________ within each of our “boxcar” sarcomeres.
myofilaments
also called myosin filaments, are made mostly of bundled molecules of the protein myosin, but they also contain ATPase enzymes, which split ATP to generate the power for muscle contraction.
thick filaments
Notice that the midparts of the thick filaments are smooth, but their ends are studded with thick projections; these projections, or myosin beads, are called ___________ when they link the thick and thin filaments together during contraction.
cross bridges
composed of the contractile protein called actin, plus some regulatory proteins that play a role in allowing (or preventing) myosin-bead
thin filaments
- very important muscle fiber organelle
- a specialized smooth endoplasmic reticulum
- the interconnecting tubules and sacs of the SR surround each and every myofibril just as the sleeve of a loosely crocheted sweater surrounds your arm, and its major role is to store calcium and to release it on demand.
sarcoplasmic reticulum
made up of hundreds of thousands of muscle cells (also called muscle fibres). These muscle cells act together to perform the functions of the specific muscle they are part of.
skeletal muscle
macro structure
muscle
fascicles
muscle fibers
micro structure
muscle fibers (bundle of myofibrils)
myofibrils
sarcomeres
myofilaments (actin, myosin)
Parts of Muscle Fiber
1) Sarcolemma
2) Mitochondria
3) Transverse tubules
4) Terminal cisternae
5) Sarcoplasmic reticulum
- Forms Short or Thinner Filaments
- Have smooth surface
- Have a lighter striations
- Slide into the H-zone during contraction
- Free at one end
actin
- Forms Long or Thick Filaments
- Have rough surface
- Have a dark striations
- Do not slide during contraction
- Free at both ends
myosin
3 structures of actin
g-actin
tropomyosin
troponin
2 structures of myosin
head
rod
FOUR MAJOR FUNCTIONS of the muscular system
contractility
excitability
extensibility
elasticity
ability of muscle to shorten forcefully, when muscle contracts, it either causes the structures to which it is attached to move or increases pressure inside a hollow organ or vessel.
contractility
capacity of muscle to respond to a stimulus.
excitability
muscle can be stretched beyond its normal resting length and still be able to contract.
extensibility
ability of muscle to recoil to its original resting length after it has been stretched.
elasticity
In an unstimulated cell, the uneven distribution of charges is referred to as the
resting membrane
Enables the determination of cell potential under non-standard conditions
nernst equation
Movement of 3 Na ions out of the cell and 2 K ions move inside the cell.
sodium potassium pump
Muscle cells and nerve cells are excitable cells
Integral membrane proteins that contain a pore which allows the regulated flow of selected ions across the plasma membrane
gated-ion channels
the initial increase of the membrane potential to the value of the threshold potential
hypopolarization
the value of the membrane potential which, if reached, leads to the all-or-nothing initiation of an action potential
threshold
The movement of Na is called the local current, which causes the inside of the cell membrane to become positively charged.
depolarization
The depolarization result is called the local potential
the peak of the action potential where the membrane potential is positive
overshoot
The subsequent return to resting potential, repolarization, is mediated by the opening of potassium ion channels
Repolarization
The process of depolarization and repolarization is what is referred to as the
action potential
action potential propagate towards the synaptic terminal which stimulates the release of a neurotransmitters
Cause calcium channels to open up, which is essential for
muscle contraction
the end of the motor neuron that divides into a cluster of synaptic end bulbs
axon terminal
neural part of NMJ
Synaptic End Bulbs
suspended in the cytosol within each synaptic end bulb are hundreds of membrane-enclosed sacs.
Synaptic Vesicles
the neurotransmitter released at the NMJ
Acetylcholine (ACh)
the muscular part of the NMJ. The region of the sarcolemma opposite the synaptic end bulbs.
The region of the sarcolemma opposite the synaptic end bulbs.
Motor End Plate
integral transmembrane proteins to which ACh specifically binds.
Acetyl Choline Receptors
deep grooves in the motor end plate that provide a large surface area for ACh.
Junctional Folds
NEUROMUSCULAR JUNCTIONS
SKELETAL MUSCLE
NEUROCARDIAC JUNCTIONS
CARDIAC MUSCLE
NEUROEFFECTOR JUNCTIONS
SMOOTH MUSCLE
The neuromuscular junction is composed of three parts:
Presynaptic motor nerve terminal
Synaptic cleft or junctional cleft
Postsynaptic muscle fiber
- Terminal end branches to one to two hundred nerve terminals
- Each ending of these terminal lies close to the membrane of the muscle
Presynaptic motor nerve terminal
- thick ends of the nerve terminals that contains special proteins, voltage-gated calcium channels, and potassium channels.
- contains a variety of cell organelles including mitochondria and endoplasmic reticulum.
- Many mitochondria mean there is enough energy for acetylcholine synthesis.
Active Zone
The space between the nerve terminal and the plasma membrane of muscle
The neurotransmitter acetylcholine (ACh) released from vesicles in the active zone of the motor nerve terminal must cross this gap to cause an effect in the muscle
Synaptic cleft or junctional cleft
The synaptic cleft contains quantities of an enzyme called
helps to break down acetylcholine into acetic acid and choline much more quickly – it is a catalyst.
Function: end a nerve impulse once it has reached the target muscle.
The release of acetylcholine requires calcium ions.
acetylcholinesterase (AChE).
positioned on the receiving end of the synaptic cleft
The power that is caused by changes in membrane voltage by the acceptance of ACh in the motor endplate receptors can depolarize a muscle fiber and cause it to contract.
ACh receptors are ligand-gated ion channels.
Between +50 and +75 millivolts are required. This power surge is called the end plate potential (EPP).
Only higher-volume release from large numbers of vesicles can produce the voltage changes that forward a nerve impulse. When enough is released to produce at least +50 mV, muscle contraction can occur.
Postsynaptic muscle fiber
ccurs because myosin heads attach to and “walk” along the thin filaments at both ends of a sarcomere, progressively pulling the thin filaments toward the M line
Muscle contraction
A muscle rests if
the motor neuron stops releasing signals
