Muscular System

Question 0

Cardiac Muscle

Answer 0

• composes bulk of heart
• cylindrical, branch frequently, and recombine
  
  • form continuous tissue mass
• intercalated disks
  
  • dark bands where plasma membranes come in contract with each other
• contract as a unit
• involuntary

Question 1

Skeletal Muscle

Answer 1

• attach to skeleton or skin
• long, cylindrical, multinucleate cells (muscle fibers)
• striated
• voluntary
• ex. any muscles that moves bones

Question 2

Smooth (visceral) muscle

Answer 2

• fibers tapered at each end, one nucleus
• nonstriated
• involuntary
• contraction highly regulated
• found in walls of hollow organs (stomach, bladder, respiratory)

Question 3

Microscopic Skeletal Muscle

Answer 3

• fibers bundled into parallel groups
  
  • bound by connect tissue
  • allows to pull together in same direction
• internal fiber framework
  
  • many long cylinders
  • thick myofilaments from protein myosin
  • thin myofilaments from protein actin
  • connect to form cross bridges
• sarcomere
  
  • basic functional contractile unit, shortens/pulls
  • composed of thick and thin myofilaments

Question 4

Motor Unit

Answer 4

• muscle must be stim. by nerve impulse b/c it contracts
• motor neuron stimulate muscle fiber
• neuromuscular junction
  
  • point of contact b/w nerve ending and muscle fiber
• neurotransmitters
  
  • released by motor neuron in response to nerve impulse
• motor unit
  
  • single motor neuron and muscle fiber it innervates

Question 5

Muscle Stimulus

Answer 5

• doesn’t contract until reaches certain level of intensity
• threshold stimulus
  
  • min. level of stim. req. for contraction
• contracts completely once threshold reached (all or none)
• occurs with each muscle fiber, not muscle as a whole

Question 6

Types of Contraction

Answer 6

Twitch

• quick, jerky response
• minimal role in normal muscle activity

Tetanic

• more sustained and steady
• contractions melt together for sustained (tetanus)
• not necessarily max. contraction where all fibers react

Isotonic

• produce movement at joint (insertion relative to origin)
• concentric-muscle shortens
• eccentric-muscle lengthens

Isometric

• muscle contracts, but no movement
• muscle length stays the same
• tension increases within

Question 7

Muscle Terms

Answer 7

Origin
-attachment to more stationary bone

Insertion
-attachment to more movable bone

Question 8

Muscles of Head and Neck

Answer 8

frontal-raises eyebrows
orbicularis oculi-closes eye
orbicularis oris-lips together
zygomaticus-elevates mouth corners
masseter-closes jaw
temporal-closes jaw
sternocleidomastoid-rotates/flexes head
trapezius-extends head/neck

Question 9

Muscles of Upper Extremities

Answer 9

Pectoralis major-flexes/adducts upper arm
latissimus dorsi- extends/abducts upper arm
deltoid-abducts upper arm
biceps brachii-flexes elbow
triceps brachii-extends elbow

Question 10

Muscles of Trunk

Answer 10

external oblique-compresses abdomen
internal oblique-compresses abdomen
transversus abdominus-compresses abdomen
rectus abdominus-flexes trunk

Question 11

Muscles of Lower Extremities

Answer 11

illiopsoas-flexes thigh or trunk
sartorius-flexes thigh, rotates leg
gluteus maximus-extends thigh
Adductor Group
     -adductor longus-adducts thigh
     -gracilus-adducts thigh
     pectineus-adducts thigh
Hamstring Group
     -semimembranosus-flexes knee
     -semitendinosus-flexes knee
     -biceps femoris-flexes knee
rectus femoris-extends knee
Quadriceps Group-extends knee
     -vastus lateralis
     -intermedius
     -medialis
Fibularis Group
     -fibularis longus-evert and plantar flex ankle
     -fibularis brevis-ever and plantar flex ankle
     -tibialis anterior-dorsiflexes ankle
     -gastrocnemius-plantar flexes ankle
     -soleus-plantar flexes ankle

Question 12

Movement

Answer 12

Flexion-bending
Extension-straightening
Abduction-away from midline
Adduction-towards midline
Rotation-movement around longitudinal axis
Circumduction-distal end in circle
Supination-hand towards anterior (holding soup)
Pronation-palm towards posterior
Dorsiflexion-toes point upward
Plantar Flextion-point toes
Inversion-bottom of foot towards midline
Eversion-bottom of foot towards side of body

Question 13

Functions of Skeletal Muscle

Answer 13

1) Movement
- move bones by pulling on them
- origin of bone stays put, insertion bone moves toward origin

2) Posture
- tonic contraction (aka muscle tone)
- continuous, low-strength muscle contractions
- few of a muscle’s fibers contract
- muscle tone maintains posture despite gravity

3) Heat Production
- contraction of fibers produce heat required to maintain temp.
- obtained from ATP
- much of energy lost as heat in transfer to ATP

Question 14

Effects of Exercise

Answer 14

• disuse atrophy
  
  • muscles shrink in mass
  • due to prolonged inactivity
• hypertrophy
  
  • increase in muscle size
  • due to exercise
• strength training
  
  • contracting muscles against heavy resistance
  • hypertrophy enhanced
• endurance/aerobic training
  
  • no hypertrophy
  • increased ability to sustain moderate exercise
  • increased number of blood vessels in muscle
  • more efficient oxygen use