Chapter 6: The Muscular System Flashcards
What are the 3 types of muscles?
Skeletal Muscle
Cardiac Muscle
Smooth Muscle
What is the location of skeletal muscle?
Attached to bone or skin (for some facial muscles)
What is the location of cardiac muscle?
walls of the heart
What is the location of smooth muscle?
mostly in walls of visceral organs (other than the heart)
What do skeletal muscle cells look like ?
Single, very long, cylindrical, multinucleate cells with very obvious striations
What do cardiac muscle cells look like ?
branching chains of cells, uninucleate, striations, intercalated discs
What do smooth muscle cells look like ?
single, fusiform, uninucleate, no striations
What are the connective tissue components of skeletal muscle?
Endomysium, perimysium, and epimysium
What are the connective tissue components of cardiac muscle?
endomysium
What are the connective tissue components of smooth muscle?
endomysium
Endomysium
encloses a single muscle fiber
perimysium
wraps around a fascicle (bundle) of muscles fibers
Epimysium
covers the entire skeletal muscle
fascia
on the outside of the epimysium
What is the direct attachment from muscle to bone?
epimysium
What are 2 indirect attachments from muscle to bones?
tendon and aponeurosis
Name the descending order of size muscle structures.
Muscle Muscle fascicle Muscle fiber (AKA muscle cell) Myofibril myofilaments = actin & myosin
Tendon
cord-like structures
mostly collagen fibers
often cross a joint due to toughness and small size
aponeuroses
sheet-like structures
attach muscles indirectly to bones, cartilages, or connective tissue coverings
skeletal muscle attachement sites
bones
cartilages
connective tissue coverings
skeletal muscle functions (4)
produce movement, maintain posture, stabilize joints, generate heat
sacrolemma
specialized plasma membrane
myofibrils
long organelles inside muscle cell
sacroplasmic reticulum
specialized smooth endoplasmic reticulum
What are the bands of myofibrils?
I band - light band, contains only thin filaments
A band = dark band, contains the entire length of the thick filaments
sacromere
contractile unit of a muscle fiber
contains myofilaments
Myofilaments
thick filaments = myosin filaments
thin filaments = actin filaments
thick filaments
myosin filaments
composed of the protein myosin, has ATPase enzymes, myosin filaments have heads (extensions, or cross bridges), myosin and actin overlap somewhat
Thin filaments
actin filaments
Composed of the protein actin, anchored to the Z disc
What kind of filaments are in the A band.
It has myosin, and lacks actin filaments
sacroplasmic reticulum
stores and releases calcium
surrounds the myofibril
excitability
aka responsiveness or irritability
ability to receive and respond to a stimulus
contractility
ability to shorten when an adequate stimulus is received
extensibility
ability of muscles cells to be stretched
elasticity
ability to recoil and resume resting length after stretching
motor unit
one motor neuron and all the skeletal muscle cells stimulated by that neuron
neuromuscular junction
association site of axon terminal of the motor neuron and muscle
synaptic cleft
gap between nerve and muscle
nerve and muscle do not make contact
area between nerve and muscle is filled with interstitial fluid
Describe the nerve stimulus and action potential
The stimulus goes to the synaptic cleft and the action potential reaches the axon terminal of the motor neuron. The Calcium channels open and calcium ions enter the axon terminal.
Describe the transmission of nerve impulse to muscle
calcium ion entry causes some synaptic vesicles to release their contents (acetylcholine, a neurotransmitter) by exocytosis. ACh attaches to receptors on the sarcolemma of the muscle cell. The sarcolemma becomes permeable to Na+. Na+ rushes into the cell generating an action potential and potassium leaves the cell. Once started, muscle contraction cannot be stopped.
neurotransmitter
chemical released by nerve upon arrival of nerve impulse in the axon terminal.
What’s the neurotransmitter for skeletal muscle?
acetylcholine (ACh)
Describe the Sliding Filament Theory of Muscle Contraction
Activation by nerve causes myosin heads (cross bridges) to attach to binding sites on the thin filament. Myosin heads then bind to the next site of the thin filament. Myosin heads then bind to the next site of the thin filament and pull them toward the center of the sarcomere. This continued action causes a sliding of the myosin along the actin. THe result is that the muscle is shortened (contracted)
graded responses
different degrees of skeletal muscle shortening
Changes based on the frequency of muscle stimulation and the number of muscle cells being stimulated at one time.
Twitch
single, brief contraction
Not a normal muscle function
Summing of contractions
one contraction immediately followed by another.
The muscle does not completely return to a resting state due to more frequent stimulations
The effects are added.
Unfused (incomplete) tetanus
Some relaxation occurs between contractions but nerve stimuli arrive at an even faster rate than during summing of contractions. Unless the mucles contraction is smooth and sustained, it is said to be unfused tennis,.
Fused (complete) tetanus
No evidence of relaxation before the following. Frequency of stimulations does not allow for relaxation between contractions.
The result is a smooth and sustained muscle contraction.
What is the first source of energy for muscle contraction?
ATP. It is stored in the muslces.
only provides 4-6 seconds worth of energy stored by muscles.
What is the second source of energy for muscle contraction?
Direct phosphorylation of ADP by creatine phosphate (CP). Muscle cells store CP. CP supplies are exhausted in less than 15 seconds. About 1 ATP is created per CP molecule.
CP transfers a phosphate group to ADP to regenerate ATP.
Aerobic respiration
Glucose is broken down to carbon dioxide and water, releasing energy (about 32 ATP).
A series of metabolic pathways occur in the mitochondria.
This is a slower reaction that requires continuous oxygen.
Carbon dioxide and water are produced.
Anaerobic glycolysis and lactic acid formation
reaction that breaks down glucose without oxygen.
GLucose is broken down to pyretic acid to produce about 2 ATP.
Pyruvic acid is converted to lactic acid.
This is fast, but inefficient.
Lactiv acid produces muscle fatigue.
oxygen deficit
A common cause of muscle fatigue. Must be “repaid” to cure muscle fatigue. Oxygen is required to rid of accumated lactic acid.
Isotonic contractions
The muscle shortens and movement occurs . Myofilaments are able to slide past each other during contractions.
Isometric contractions
Tension in the muscles increases. The muscle is unable to shorten or produce movement.
Muscle Tone
some fibers are contracted even in a relaxed muscles. Different fibers contract at different times to provide muscle tone and to be constantly ready.
Five Golden Rules of Skeletal Muscle Activity
- With a few exceptions, all skeletal m muscles cross at least one joint.
- Typically, the bulk of a skeletal muscle lies proximal to the joint crossed.
- All skeletal muscles have at least tow attachments; the origin and the insertion.
- Skeletal muscles can only pull; they never push
- During contraction, a skeletal muscle insertion moves toward the origin.
The origin is attachment to a __________ bone
movable
The insertion is the attachment to an __________ immovable bone.
immovable
Inversion
turn sole of foot medially
Eversion
turn sole of foot laterally
Frontalis
raises eyebrows
orbicularis oculi
closes eyes, squints, blinks, winks
buccinator
flattens the cheek, chews
zygomaticus
raises corners of the mouth
messeter
closes the jaw and elevates the mandible
Temporalis
synergist of the masseter, closes jaw
platysma
pulls the corners of the mouth inferiorly
sternocleidomastoid
flexes the neck, rotates the head
pectoralis major
adducts and flexes the humerus
intercostal muscles:
External intercostals
Internal intercostals
external: raise rib cage during inhalation
Internal: depress the rib cage to move air out of the lungs when you exhale forcibly
rectus abdominis
flexes the vertebral column and compresses abdominal contents (defecation, childbirth, forced breathing)
external oblique
flex vertebral column, rotate trunk and bed it laterally
internal oblique
flex vertebral column, rotate trunk and bend it laterally
transversus abdominis
compresses abdominal contents
Trapezius
elevates, depresses, adducts, and stabilizes the scapula
latissimus dorsi
extends and adducts the humerus
erector spinae
beck extension
quadratus lumborum
flexes the spine laterally
deltoid
arm abduction
Erector Spinae
I LOVE SPINES (3)
Iliocostalis
Logissimus
Spinalis
biceps brachii
supinates forearm, flexes elbow
brachialis
elbow flextion
brachiradialis
weak muscle; elbow flexion
Triceps brachii
elbow extension (antagonist to biceps brachii)
gluteus maximus
hip extension
gluteus medius
hip abduction, steadies pelvis when walking
iliopsoas
hip flexion, keeps the upper body from falling backward when standing erect
adductor muscles
adduct the thighs
Hamstring group (3) = thigh extension and knee flexion
biceps femoris
semimembranosus
semitendinosus
sartorius
flexes the thigh
quadriceps group (2) = extends the knee
rectus femoris vastus muscles (3)
Tibialis anterior
dorsiflextion, floot inversion
extensor digitorum longus
toe extension and dorsiflextion of the foot
fibularis muscles
plantar flexion, foot eversion
soleus
plantar flexion
gastrocnemius
plantar flexion
