Module 8: The Muscular System Flashcards
3 types of muscle
Skeletal
Smooth
Cardiac
Functions of muscles (4)
Produces movement
Maintains posture
Stabilizes joints
Generates heat
Produces movement
Skeletal muscles - walk, blink, turn around, chew, laugh etc
Smooth muscles line blood vessels and transport blood
Cardiac muscle operates as a pump for the blood
Maintains posture
Skeletal muscles defy gravity by making adjustments that allow us to sit or stand erect
Stabilizes joints
Skeletal muscles hold bones together and assist in stabilizing and strengthening joints
Generates heat
Muscle activity of ALL muscles general heat (skeletal muscles generate the most)
Coverings of skeletal muscle
- covered by fascia (layers of fibrous connective tissue)
- fascia extends beyond muscle and turns into the tendon
- Epimysium of fascia is the layer that attaches to the muscle
- Muscle fibers (cells) are grouped into fascicles (bundles)
- Perimysium surrounds each bundle
- Endomysium surrounds each muscle fiber
Structure of muscle fiber (cell)
- Elongated cells with hundreds of nucleoli
- Plasma membrane called sarcolemma
- Cytoplasm called sarcoplasm
- Each fiber is made of many myofibril which consist of myofilaments
- Sarcoplasmic reticulum surrounds each myofibril
- each myofilament is made of thin (actin) and thick (myosin) filaments
- Myfilaments arranged in sarcomeres (give muscle striated look)
- T tubules carry nerve stimulus into muscle fiber
Sliding filament mechanism
sliding of the thin filaments toward the center of the sarcomere causes the unit to shorten
Contracting muscles:
-nerve impulse stimulates sarcolemma
-t tubules allow stimulus to reach sarcolemma
-myosin heads make contact with actin to form temporary cross bridges
-myosin heads rotate, pulling actin inwards
Motor neuron
transmits nerve impulses from the brain and spinal cord to the skeletal muscles
Motor unit
a single motor neuron and the muscle fibers it stimulates
Neuromuscular Junction (NMJ)
The area where the motor neuron meets the muscle fibers
Structures include: plasma membrane @ end of neuron, Synaptic cleft (space between end of neuron and sarcolemma/plasma membrane of muscle fiber), sarcolemma/plasma membrane and its receptor sites
The neuron releases chemicals that diffuse across NMJ and stimulate the muscle fiber
Action potential
electrical impulse resulting from stimulation of the neuron to move along the neuron towards the axon terminal with vesicles (containing ACh, acetylcholine)
Acetylcholinesterase
NMJ enzyme that breaks down ACh
What happens to the electrical signal in the sarcolemma
- signal travels along sarcolemma
- travels through T tubules and then stimulates the sarcoplasmic reticulum to release Calcium
- Calcium floods the sarcomeres and allows interaction of actin, myosin and ATP to cause muscle contraction
- Calcium is pumped back into the sarcoplasmic reticulum, away from actin and myosin causing muscle relaxation
All or none principle
The muscle fibers are either ON (contracting completely) or OFF (relaxing)
Isotonic contraction
Muscles shorten and movement occurs
ex. lifting object, walking, swimming,
Isometric contraction
Muscles DO NOT shorten and NO movement occurs
ex. pushing against a wall with arms, holding a book in your palms, TRYING to lift a piano
Tone
in skeletal muscles, when there are always some muscle fibers contracted (not the whole muscle, just some fibers)
3 types of muscle metabolism
Muscles require lots of ATP to contract
Aerobic metabolism
Anaerobic metabolism
Metabolism of Creatine Phosphate
Aerobic metabolism
In presence of oxygen Fuels such as glucose and fatty acids are completely broken down by Aerobic Respiration Glucose + oxygen = CO + H2O + ATP (lots of ATP, 38 ATP per glucose) *Provides the most ATP
Anaerobic Metabolism
In absence of oxygen
Anaerobic Respiration partially breaks down glucose to produce lactic acid and a small amount of ATP
Glucose = lactic acid + ATP
*Takes the shortest amount of time
Metabolism of Creatine Phosphate
Creatine phosphate is a high energy compound stored in muscle
Creatine phosphate + ADP = creatine + ATP
Oxygen debt
additional oxygen that is required after a physical activity to restore resting conditions
O2 needed to convert lactic acid into glycogen
Labored breathing
continues after the activity has stopped until oxygen debt has been brought back to equilibrium
Skeletal muscle origin
the end of the muscle that is attached to the STATIONARY bone (not easily movable)
Skeletal muscle insertion
the end of the muscle that is attached to the other bone (easily movable)
Prime mover
the main muscle in a particular movement
ex. during bicep curls, biceps are the prime mover
Antagonist muscle
a muscle that opposes the action of another muscle
Synergist muscle
help the prime mover by stabilizing joints or preventing awkward movement
naming of muscles is based on:
location shape relative size direction of muscle fibers number of origins location of attachments action
Location of muscle
Adbominis (abdomen) Carpi (wrist) Femoris (femur) Oculo (eye) Oris (mouth) Pectoralis (chest) Temporalis (temporal bone)
Shape of muscle
Deltoid (triangle) Latissimus (wide) Orbicularis (circular) Serratus (serrated) Teres (long and round) Trapezius (trapezoid shape)
Relative size of the muscle
Brevis (short) Longus (long) Maximus (large) Minimus (small) Minor (small) Vastus (huge)
Direction of muscle fibers
Oblique (diagonal)
Orbicularis (circular)
Rectus (straight)
Transverse (cross)
Number of origins
May be named according to the number of sites the muscle is anchored to
Ex. Bicep (2)
Tricep (3)
Quadriceps (4)
Action
Abductor (moves away from the midline of the body)
Adductor (moves towards the midline of the body)
Superficial muscles for chewing
Masseter
- raises the mandible (lower jaw bone)
- responsible for mastication(chewing)
Superficial muscles for movement of head, pectoral girdle, upper arm
Sternocleidomastoid (sides of neck)
Trapezius (moves shoulder blade and the head)
Deltoid (abducts the arm to a horizontal position)
Pectoralis major (large anterior muscle in upper ches)
Latissimus dorsi (lateral and dorsal, extends and adducts the arm)
Superficial muscles of the abdominal wall
External Oblique Rectus Abdominis (holds contents of the abdominal cavity in place)
Superficial muscles in the arms and hands
Biceps brachii (anterior upper arm) Triceps brachii (posterior upper arm) Flexor carpi or extensor carpi (move wrist and hand)
Superficial muscles in the legs and feet
Gluteus maximus (straightens leg) Gluteus medius (raises leg sideways to horizontal position) Adductors (medial part of thigh, bring down leg from a horizontal position) Quadriceps Femoris (main extensor of the lower leg) Hamstring group (includes semitendinousus, biceps femoris, semimembranosus) Sartorius (strap like muscle from hip to inside of knee) Gastrocnemius (plantar flexor) Tibialis anterior (used for inversion of foot) Peroneus (connects fibula to foot bones; pointing your toes)
