Chapter 5: Muscular system Flashcards
What are the two types of myofilaments are muscle contractions dependent on?
Actin and myosin
What is the muscle plasma membrane called?
sarcolemma
What is the cytoplasm of a muscle cell called?
sarcoplasm
What are the three prefixes that refer to muscle?
myo, mys, and sarco
What are the three types of muscle?
Skeletal
Cardiac
Smooth
What are the function characteristics of muscle? 4
-Excitability or irritability – the ability to receive and respond to stimuli
-Contractility – the ability to shorten forcibly
-Extensibility – the ability to be stretched or extended
-Elasticity – the ability to recoil and resume the original resting length
Which muscle makes up 40% of the body’s weight
Skeletal muscle tissue
Which muscle tissue has striations?
Skeletal, Cardiac
Which muscle tissue is uninucleated?
cardiac and smooth
What is the origin of the skeletal muscle?
Where the short connective tissue fibers attach to the less movable attachment
What is the insertion of the skeletal muscle?
Where the connective tissue of the muscle forms a tendon in the more movable attachment
What is the function of the skeletal muscle?
Force production for locomotion and breathing (diaphragm).
Force production for postural support.
Heat production during cold stress.
What is the endomysium? 3 points
fine sheath of connective tissue composed of reticular fibers surrounding each muscle fiber
What is the perimysium? 2 points
fibrous connective tissue that surrounds groups of muscle fibers called fascicles
What is the epimysium?
an overcoat of dense regular connective tissue that surrounds the entire muscle
How long and thick is one muscle fibril cell?
10-100 micrometer in diameter, and up to several cm long
Every muscle cell is a synctium. What does that mean?
produced by a fusion of ebryonic cells
What do sarcoplasm contain a lot of? 2
glycosomes and myoglobin
Glycosomes are membranes containing glycolytic enzymes.
They break down glucose into two halfs so that it could be converted to ATP
What does it mean to say that muscle fibers act in an all or nothing way?
They either all contract or all relax
What do fibers contain? 4
Organelles, myofibrils, sarcoplasmic reticulum and T-tubules
What are the dark and light parts of a myofibril called?
Dark A bands and light I bands
Which part of the muscles make up most of the muscle mass?
myofibrils
What is the smallest contractile unit of as muscle fiber?
Sarcomere
What are the two types of myofilaments?
Thick-myosin
Thin-actin
Which zone dissapears when a sarcomere contracts?
The zone where only myosin is present (H-Zone)
What is the function of the z disc?
coin-shaped sheet of proteins (connectins) that
anchors the thin filaments and connects myofibrils to
one another
What protein is present in the M zone?
desmin
What is myosin composed of?
a rodlike tail and two globular heads
What is the head and the tail of myosin made up of? 4
Head - two smaller, light polypeptide chains called bridges
Tail - two interwoven heavy polypeptide chains
What are singular spherical actin subunits called?
G actin
What are the regulatory subunits bound to actin called? 2
tropomyosin and troponin
Where do T-tubules penetrate the cells?
A-band and I-band junction
What is the function of terminal cisternae?
regulation of intracellular calcium levels
What are triads?
T tubules associations with the paired terminal cisternae
What is the function of T-Tubules?
conduct impulses to the deepest regions of the muscle
Which structures provide tightly linked signals for muscle contraction
T-Tubules and sarcoplasmic reticulum
What part of the muscles act as voltage sensors?
T-Tubules protiens
What is the function of sarcoplasmic reticulum foot protiens?
receptors that regulate Ca2+
release from the SR cisternae
Explain the sliding filament model. 4
- In the relaxed state, thin and thick filaments overlap
only slightly. - Upon stimulation, myosin heads bind to actin and sliding begins.
- Each myosin head binds and detaches several times during contraction, to generate tension and propel the thin filaments to the center of the sarcomere.
- As this event occurs throughout the sarcomeres, the muscle shortens.
State and explain the four sequential events of contraction
- Cross bridge formation – myosin cross bridge attaches to actin filament
- Working (power) stroke – myosin head pivots and pulls actin filament toward M line
- Cross bridge detachment – ATP attaches to myosin head and the cross bridge detaches
- “Cocking” of the myosin head - energy from hydrolysis of ATP cocks the myosin head into the high-energy state
What is the excitation contraction coupling?
It is the communication between the electrical events and the mechanical events that happen as a response
What happens when calcium ions binds troponin?
The blocking action of tropomyosin ceases and Actin active binding sites is exposed
What is the function of excitation contraction coupling?
to transform the electrical stimulation of the sarcolemma into muscle contraction
What is the one crucial event that starts muscle contraction?
The stimulus by nerve terminal
What is the neuromuscular junction?
junction between the motor nerve and skeletal muscle fiber
What is the axonal terminals
the terminal end of the
axon
What happens when when a nerve impulse reaches
the end of an axon at the neuromuscular junction?
- Voltage-regulated calcium channels open and allow Ca2+ to enter the axon.
- Ca2+ inside the axon terminal causes axonal vesicles to fuse with the axonal membrane.
What happens after the fusion of axonal vesicles in the membrane?
-Releases ACh into the synaptic cleft via
exocytosis.
-ACh diffuses across the synaptic cleft to ACh
receptors on the sarcolemma.
-Binding of ACh to its receptors initiates an action
potential in the muscle.
What is the role of acetylcholine at the nerve terminal? 3
-ACh binds its receptors at the motor end plate (on
sarcolemma)
-Binding opens chemically (ligand) gated channels
-Na+ diffuses inwards and the interior of the sarcolemma becomes less negative
What causes depolarization in the skeletal muscle?
The opening of sodium channels, when the sodium enters the cell and potassium leaves it
How does depolarization spread? And what are the names given to each stage?
-Initially, this is a local electrical event called end plate
potential
-Later, it starts an action potential that spreads in all
directions across the sarcolemma
Where does generation of active potential happen?
In muscle fiber
How can you describe a twitch movement?
A single contraction that goes into rest afterwards
How can you describe a summing of contractions?
A second nerve impulse that is sent before the first is recovered
How do you describe an unfused tetanus movement?
Severeal impulses sent before first comes to rest
How do you describe an fused tetanus movement?
when there is no relaxation of the muscle fibers between stimuli
When muscles cross a joint anteriorly what movement does it produce?
Felxion
When muscles cross a joint posteriorly what movement does it produce?
Extension
When muscles cross a joint medially what movement does it produce?
Adduction
When muscles cross a joint laterally what movement does it produce?
Abduction
Muscles located within the same group of muscles share the same what?
Action, innervation and blood supply
Muscles dorsal to upper limb bones produce which movement?
Extension
Muscles dorsal to lower limb bones produce which movement?
Flexion
What are skeletal muscle names based on? (6)
- Direction of fascicles and muscle fibers
- Location of attachments
- Number of origins
- Action
- Location
- Shape
- Relative size
What are the functional classification of muscles?
- Prime move
- Antagonist
- Synergist (adds extra force or reduces undesirable movements)
- Fixator
What are the types of fascicle arrangements?
- Convergent
- Parallel:
Straplike
Fusiform
What is in an example of parallel strap like muscle?
Sartorius
What is an example of fusiform parallel muscle?
Biceps brachii
What is an example of a convergent muscle?
Pectoralis major
What is a type of unipennate muscle?
Extensor digitorum longus
What is an example of bipennate muscle?
Rectus femoris
What is an example of multipennate muscle?
Deltoid
What is another name for circular muscles ?
Sphincter
What is an example of a circular muscle?
Orbicularis Oris/oculi
Describe first class lever
Effort. Load
|. Fulcrum. |
Describe class 2 levers
|. Load
Effort. |. Fulcrum
Describe third class lever
|. Load
Fulcrum. Effort |
What is an example of first class lever?
Scissors
What is an example of second class lever?
Wheelbarrow
What is an example of third class lever?
Tweezers
What is the most used lever in body?
Third class
What is the law of levers?
When the effort is farther from the fulcrum than the load, the lever operates at a mechanical advantage
