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A&P-Muscular System-Ruben J. Mora - Coggle Diagram
A&P-Muscular System-Ruben J. Mora
Major function of muscular system
move the skeleton
maintain body posture
support soft tissues
maintain body temperature
Sarcomere:
A sarcomere is a contractile unit of muscle fibers, sarcomeres extend from
z-line
to z-line. As muscles contract, this results in the shorting of the sarcomere.
Each sarcomere is composed of the protein filaments
actin(thin filaments)
and
myosin(thick filaments)
.
I-bands(light bands)
are made up of actin filaments, which are anchored to the
z-lines
.
A-bands(dark bands)
are made up of overlapping this and thin filaments. The
M-line
in the center of the
H-zone
, which consists of proteins that hold the myosin filaments in place.
Skeletal Muscles;
Characteristics;
Each muscle fiber is a single, long, cylindrical muscle cell.
Fibers
respond to stimulation by contracting.
Cell membrane of a muscle fiber is the
sarcolemma
.
The cytoplasm of a muscle cell is the
sarcoplasm
, it contains many mitochondria and nuclei.
Sarcoplasm contains parallel
myofibrils
, which are active in muscle contraction,
they are made up of units called sarcomeres.
Myofibrils have thick filaments which are of the protein
myosin
. It also has thin filaments that are composed of the protein
actin
but contains
troponin and tropomyosin.
Skeletal muscles are named according to size,shape, location,action,number of attachments,direction of its fibers
Pectoralis major
: named for size and location; large size, located in chest
Deltoid
: named for shape; shaped like a triangle
Biceps brachii:
named for number of attachments and location; has 2 origins/heads, and is found in the arm
Extensor digitorum
: named for action; extends fingers/toes
External oblique
: named for location and direction of fibers; located near outside of the body, and fibers run at a slant
Facial Muscles
:
Temporalis
: Named for location as it is found at the side of the head, the temporal
Frontalis
: named for location as it is found in the forehead
Orbucularis Ocul
i: is named for the shape as it is circular and encompasses the eye
Sternocleidomastoid
: named for attachments; attaches to sternum, clavicle, and mastoid process
Zygomaticus
: named this as it is a thin paired facial muscle that extends diagonally from the zygomatic bone
Orbicular oris:
named because of shape & location as the muscle is in the lips and encircles the mouth
Massete
r:It is named this as it is connected to the mandible
Platysma:
Is named because there are 2 of them and because of the shape as it is thin and a flat.
Types of Muscles;
Smooth Muscle
(Lines the walls of hollow organs): This contains thick and thin filaments, but they are arranged randomly. It is involuntary and contracts and relaxes slowly; single unit type is self-exciting; rhythmic(rhythm). It has a single nucleus and no t-tubules
Skeletal Muscle
:Is voluntary and contracts and relaxes rapidly when stimulated by a motor neuron. It has many nuclei and a well developed t-tubule system.
Cardiac Muscle
(Only in hear): Is voluntary and is a network of cells contracting as a unit; self-exciting; rhythmic(rhythm). It resists fatigue as it always has to be pumping blood throughout the body. It has a single nucleus and a well-developed
transverse tubule
system
Neuromuscular Junction:
Skeletal muscle fibers contract only when stimulated by a motor neuron
Each skeletal muscle fiber is functionally connected to the axon of a motor neuron, creating a synapse
The neuron communicates with the muscle fiber by way of chemicals called
neurotransmitters
, which are released at the
synapse
(small pocket of space between two cells, where they can pass messages to communicate).
At the distal end of the motor neuron is the
motor end plate,
which contains specific receptors for the neurotransmitters.
When an electrical impulse reaches the end of the axon of a motor neuron, synaptic vesicles release neurotransmitter into the synaptic cleft. The neurotransmitters diffuse across the cleft, bind to the motor end plate, and stimulate the muscle fiber to contract
Neuromuscular junction Steps(7):
Step 4
:ACH diffuses across the synaptic cleft and binds to its receptors on the muscle which contain ligand-gated cation channels
Step 5
:ACH binding opens ion channels
Step 3
:Calcium causes the vesicles to release acetylcholine into the synaptic cleft
Step 6
:Sodium rushes into the muscle and the potassium leaves.
Step 2
:Electrical gated calcium channels open
and calcium enters the axon terminal
Step 7:
ACH is broken down by acetylcholinesterase
Step 1
:An action potential goes down a motor neuron to a axon terminal.
Action Potential in a Muscle fiber
:The muscle action potential triggers a sequence of actions that ultimately results in the contraction and relaxation of the muscle fiber.
Muscle Coverings:
Layers of dense connective tissue, called
fascia
, surround and separate each muscle, it extends beyond the ends of the muscle and gives rise to tendons. Fascia blends with the epimysium
Sometimes muscles are connected to each other by broad sheets of connective tissue called aponeuroses.
Each muscle cell (fiber) is covered by a connective tissue layer called endomysium
Sliding Filament Theory:
Step 2:
The impulse travels down the membrane and into the t-tubules where it causes calcium ions to be released from the SR(sarcoplasmic reticulum).
Step 1
: Muscle contraction starts in the brain, where signals are sent along the motor nueron, within the motor neuron are vesicles that contain the neruotransmitter and Ach. When Ach reaches the receptors the whcih cause an impulse
Step 3:
Calcium binds to a structure on the actin that causes it to change shape
Step 4:
The change in shape allows myosin heads to form cross-bridges between the actin and the myosin.
Step 5
: Energy from ATP is used to create a ¨power stroke¨ between the two filaments. The actin filaments slide inward and shorten, or contract the whole muscle.
The sliding filament theory describes the mechanism that allows muscles to contract. According to this theory, myosin (a motor protein) binds to actin. The myosin then alters its configuration, resulting in a "stroke" that pulls on the actin filament and causes it to slide across the myosin filament causing it to contract.