Muscular system Flashcards
Three basic muscle types are found in the body
Skeletal muscle
Cardiac muscle
Smooth muscle
Each muscle is a discrete organ, composed of:
Each muscle is a discrete organ, composed of: muscle fibers blood vessels nerve fibers connective tissue
Endomysium
Endomysium - encloses a single muscle fiber
Perimysium
wraps around a fascicle (bundle) of muscle fibers
Epimysium
Epimysium - surrounds entire muscle
Sites of muscle attachment
Bones (with or without tendons)
Cartilage
Aponeuroses - connective tissue sheet-like covering
Skeletal muscle functions
Produce skeletal movement
Maintain body posture and body position
Stabilize joints
Generate heat
Support soft tissue and surrounding visceral organs and internal tissues
Move blood and fluids through body, plus aiding with respiration
Guard entrances and exits – swallowing, digestive, urinary
Provide nutrient reserves - starvation
Muscle cell (myocyte) =
Muscle cell (myocyte) = muscle fiber
Cell membrane =
Cell membrane = sarcolemma
Cytoplasm =
Cytoplasm = sarcoplasm
Endoplasmic reticulum (ER) =
Endoplasmic reticulum (ER) = sarcoplasmic reticulum (SR)
Contain hundreds of nuclei
Filled with cylindrical structures called myofibrils
Contain actin and myosin
muscle fibers
complex organelle composed of bundles of myofilaments
Myofibril or Fibril
Specialized smooth endoplasmic reticulum
Stores and releases calcium
Surrounds the myofibril
Sarcoplasmic reticulum (SR)
How do actin and myosin act to contract the muscle and make it move?
Actin and myosin slide past each other causing the fibre to shorten
The fibre lengthens when the actin and myosin go back to their original places
Actin & myosin give the muscle it’s striated look under the microscope
When a nerve impulse reaches the axon terminal of the motor neuron,
1.Calcium channels open, and calcium ions enter the axon terminal
2.Calcium ion entry causes some synaptic vesicles to release acetylcholine (ACh)
3. ACh diffuses across the synaptic cleft and attaches to receptors on the sarcolemma of the muscle cell
I4.f enough ACh is released, the sarcolemma becomes temporarily more permeable to sodium (Na)
5.Depolarization opens more sodium channels that allow sodium ions to enter the cell
Once started, the action potential cannot be stopped, and contraction occurs
6. Enough depolarization allows for Ca2+ to be released from the sarcoplasmic reticulum (SR)
Surrounds the myofibrils and allows for actin and myosin to link
7. K+ efflux causes repolarization and reuptake of Ca2+ back into the SR
8. Acetylcholinesterase (AChE) breaks down acetylcholine into acetic acid and choline
AChE ends muscle contraction
If neuromuscular junction sites are altered
If neuromuscular junction sites are altered
can’t bind with ACh - muscle weakness will occur
Ex: Myasthenia Gravis
Muscle fibers contain a reddish brown pigment called ________
Fibers that are red have high amounts of _______, while those that are white have low amounts
_______ allows for high amounts of oxygen to be available to muscle fibers
Myoglobin
Properties of muscle fibers
Excitability (also called responsiveness or irritability) - ability to receive and respond to a stimulus
Contractility - ability to shorten when an adequate stimulus is received
Extensibility - ability of muscle cells to be stretched
Elasticity - ability to recoil and resume resting length after stretching
Skeletal muscles must be stimulated by a ________ _______ to contract
Skeletal muscles must be stimulated by a motor neuron (nerve cell) to contract
one motor neuron and all the skeletal muscle cells stimulated by that neuron
Motor unit
Single, brief contraction
Not a normal muscle function
Twitch
One contraction is immediately followed by another
Because stimulations are more frequent, the muscle does not completely return to a resting state
The effects are “summed” (added
Summing of contractions
Some relaxation occurs between contractions, but nerve stimuli arrive at an even faster rate than during summing of contractions
Unless the muscle contraction is smooth and sustained, it is said to be in ______ _______
Unfused (incomplete) tetanus
No evidence of relaxation before the following contractions
Frequency of stimulations does not allow for relaxation between contractions
The result is a smooth and sustained muscle contraction
Fused (complete) tetanus
If muscle activity is strenuous and prolonged, muscle fatigue occurs because:
If muscle activity is strenuous and prolonged, muscle fatigue occurs because:
Ionic imbalances occur
Lactic acid accumulates in the muscle
Energy (ATP) supply decreases
The common reason for muscle fatigue is
The common reason for muscle fatigue is O2 debt
Isotonic contractions
Isotonic contractions
Muscle shortens and the muscle contraction causes movement
Example is bending knee, rotating arms, smiling
Isometric contractions
Isometric contractions
Tension in the muscles increases – generate force without movement
The muscle does not shorten
Aerobic exercise – uses high amounts of O2
Aerobic exercise – uses high amounts of O2 Increases heart rate Increases blood supply to muscles Increases body metabolism increases digestion and elimination Improves coordination Increased bone density Improved blood flow to whole body Efficient gas exchange at lungs
atrophy
response when muscles are not used as much and they decrease in size
fixator
designed to stabilize a joint during movement. fixators groups in ankle prevent them from wobbling when standing
antagonist
muscles that oppose the action of another muscle
synergist
synergist also known as “helper muscles”, that assist the primer mover. can produce same movement or stabilize joints across where prime mover acts, preventing undesirable movements
_____ of the muscle attaches to the more movable bone
Insertion
_____ of the muscle attaches to the stationary (unmovable) bone
origin
muscle’s function to response to stimuli
irritability
gap junctions that promote rapid conduction of electrical signals throughout the heart
intercalated discs
nonstriated muscle
smooth muscle
moves the bones of the face
skeletal muscle
Cardiac and Smooth are involuntary while skeletal is _______
voluntary
Cardiac and ______ muscles are striated
Skeletal
Touching the thumb to other fingers
Opposition
Forearm rotation medially so that the palm faces posteriorly and the ulna and radius are crossed
Pronation
Forearm rotation laterally so that the palm is facing anteriorly and the radius and ulna are parallel
Supination
A combination of all the movements, commonly seen in ball and socket joints where the proximal end of the limb is stationary while the distal end moves in a circle
Circumduction
Opposite of abduction; movement of a limb toward the body midline
Adduction
moving a limb away in the frontal plane from the median plane of the body, spreading the fingers apart
Abduction
Movement of a bone around its longitudinal axis.
Rotation
]Opposite of flexion; movement in the saggital plane that increases the angle of the joint or distance between two bones or parts of the body.
Extension .
Movement in the saggital plane that decreases the angle of the joint and brings two bones closer together.
Flexion
A place where a muscle attaches on a bone that is moved by the muscle.
Insertion
Origin
Origin A place where a muscle attaches on a bone that is not moved by that muscle.
A metabolic process that doesn’t require oxygen. Glucose is broken down to pyruvic acid to produce some ATP. Pyruvic acid is then converted to lactic acid.
Anaerobic Glycolysis
A metabolic process requiring oxygen and taking place in the mitochondria. Glucose and fat are broken down to carbon dioxide and water in order to release energy.
Aerobic Respiration
The process in which creatine phosphate, a high energy molecule, has its energy released to ADP in order to regenerate it to ATP.
Direct Phosphorylation
A unit of stored energy which muscles use initially for contraction. Only 4-6 seconds of ATP energy is stored by muscles. The bonds within ATP are broken in order to release the energy.
ATP
The place at which the nervous system is connected to the muscular system through a synapse. It is here in which the muscle cells are simulated by a single neuron
Neuromuscular Junction
A structure within a unit of myofibril. It is a membrane which actin is embedded in.
Z Disc
The contractile unit of a myofibril consisting of Z-discs, A-bands, and I-bands.
Sarcomere
Microfilaments of actin and myosin in repeating subunits.
Myofibrils
The special type of smooth endoplasmic reticulum found in smooth and striated muscle fibers whose function is to store and release calcium ions.
Sarcoplasmic reticulum
The cell membrane of a striated muscle cell.
Sarcolemma
Cardiac Muscle
One of the three types of muscle tissues. These have striations, usually a single nucleus, are joined together by another muscle cell by an intercalated disc, function involuntarily, and are found only in the heart.
Smooth Muscle
One of the three different types of muscle tissue. This muscle has no striations and is formed from spindle shaped cells, they possess a single nucleus, move involuntarily, and are found mainly in the walls of hollow organs.
A type of connective tissue formed when epimysium blends into particular connective tissue attachments.
Collagen Fibers of the Skin
A sheet like structure whose primary function is to join muscles to the body parts (bone or muscle) the muscles act upon.Is formed by epimysium blending into connective tissue attachments.
Aponeurosis
Is a cord like structure which connects muscles to bones. It is formed by epimysium blending into connective tissue attachments.
Tendon
Epimysium
A connective tissue wrapping which covers the entire skeletal muscle.
Perimysium
Perimysium A connective tissue wrapping which wraps itself around a fascicle (bundle) of cells/fibers.
Endomysium
A connective tissue wrapping which wraps itself around a single muscle cell/fiber.
One of the three types of muscles. Muscles move voluntarily and are attached by tendons to bones. They are long, multinucleate (have multiple nucleus), appear striated (due to arrangement of actin and myacin), and are surrounded and bundled by connective tissue. (which supplies nutrients)
Skeletal Muscle
A type of tissue which is responsible for movement in body. This movement produces heat as a byproduct.
Muscles
Skeletal muscles named based on:
Skeletal muscles named based on: Region of body (femoris = thigh) Position (posterior = back) Nature of origin or insertion (biceps = two heads) Shape (deltoid = triangle) Size (maximus = largest) Action (flexor = bending movement)
Support and position axial skeleton
Aid in breathing
Axial Muscles
Support, move, and brace limbs
Apendicular Muscle
Facial muscles
Frontalis - raises eyebrows
Orbicularis oculi - closes eyes, squints, blinks, winks
Orbicularis oris - closes mouth and protrudes the lips
Buccinator - flattens the cheek, chews
Zygomaticus - raises corners of the mouth
Chewing muscles
Chewing muscles
Masseter - closes the jaw and elevates mandible
Temporalis - synergist of the masseter, closes jaw
Neck muscles
Platysma – pulls the corners of the mouth inferiorly
Sternocleidomastoid – flexes the neck, rotates the head
Anterior muscles
Pectoralis major - adducts and flexes the humerus
Intercostal muscles – movement of rib cage for breathing
Muscles of the abdominal girdle
Rectus abdominis - flexes vertebral column and compresses abdominal contents (defecation, childbirth, forced breathing)
External and internal obliques - flex vertebral column; rotate trunk and bend it laterally
Transversus abdominis - compresses abdominal contents
Posterior muscles
Trapezius - elevates, depresses, adducts, and stabilizes the scapula
Latissimus dorsi - extends and adducts the humerus
Erector spinae - back extension
Quadratus lumborum - flexes the spine laterally
Deltoid - arm abduction
because of the size of the deltoid, it is a favorite site for injections of small amounts (less than 5 mL)
Muscles of the upper limb
Biceps brachii - flexes elbow
Brachialis - elbow flexion
Brachioradialis - weak muscle for elbow flexion
Triceps brachii - elbow extension (antagonist to biceps brachii)
Biceps brachii, brachialis, and brachioradialis are all anterior muscles, while triceps brachii is the only posterior muscle
Muscles causing movement at the hip joint and thigh
Gluteus maximus - hip extension Gluteus medius - hip abduction Iliopsoas - hip flexion Adductor muscles - adduct the thighs Sartorius - flexes the thigh
Hamstring group - thigh extension and knee flexion
Biceps femoris
Semimembranosus
Semitendinosus
Quadriceps group - extends the knee
Rectus femoris (also flexes hip) Vastus muscles (three) Vastus lateralis Vastus intermedius Vastus medialis
Muscles causing movement at ankle and foot
Tibialis anterior - dorsiflexion
Gastrocnemeus – plantar flexion (and weak knee flexor)
Soleus - plantar flexion
If muscle activity is strenuous and prolonged, muscle fatigue occurs because:
If muscle activity is strenuous and prolonged, muscle fatigue occurs because:
Ionic imbalances occur
Lactic acid accumulates in the muscle
Energy (ATP) supply decreases
Aerobic respiration
Aerobic respiration
Glucose is broken down to CO2 and H2O, releasing ATP
Slower reaction that requires O2
Series of metabolic steps occurring in the mitochondria
Lasts for a very long time
Anaerobic glycolysis and lactic acid formation
Breakdown of glucose without O2
Glucose pyruvic acid lactic acid
This reaction is not efficient, but is fast
Only lasts for 30 – 60 seconds
Direct phosphorylation of ADP by creatine phosphate (CP)
Direct phosphorylation of ADP by creatine phosphate (CP)
Muscle cells store CP
CP = high-energy molecule
After ATP is depleted, ADP is left
CP transfers energy to ADP, to regenerate ATP
CP supplies are exhausted in less than 15 seconds
Aerobic exercise
uses high amounts of O2 Increases heart rate Increases blood supply to muscles Increases body metabolism increases digestion and elimination Improves coordination Increased bone density Improved blood flow to whole body Efficient gas exchange at lungs
