Muscles & Movement

Question 0

Components of skeletal muscle

Answer 0

Muscle -> fascicles (cell bundles) -> muscle fibres (cells) -> myofibrils -> myofilaments

Question 1

3 types of muscles?

Answer 1

• Skeletal
• Cardiac
• Smooth

Question 2

Properties of muscles (4)

Answer 2

1. Excitability (equated w/ excitability)
2. Contract ability (stimulation causes muscles to contract)
3. Elasticity (ability to return to original length when tension released)
4. Extensibility: capable of extending in length in response to contraction of opposing muscle

Question 4

Composition of myofibrils

Answer 4

• myofibrils formed from chain of repeating units called sarcomeres
  
  • are the functional contractile unit of a skeletal muscle fibre
  • defined as distance from one Z disc to another
• each sarcomere shortens as muscle fibres contract
• thick (myosin) and thin (actin) filaments interact
  
  • regulartory proteins in thin = tropomyosin & troponin
• energy (ATP) causes myosin heads to move along actin filaments, shortening myofibrils and contracting muscle

Question 5

Muscle attachments - origin & Insertion

Answer 5

Origin: less mobile attachment of muscle (aka proximal/fixed/broad)
Insertion: more mobile attachment or muscle (aka distal/mobile/narrow)

*muscle has both an insertion and origin

Question 6

Muscle terminology;-

Intrinsic vs extrinsic

Isotonic vs isometric

Answer 6

Intrinsic: on inside relative to other body parts
Extrinsic: on outside “ “ “ “

Isotonic: movers (I.e biceps)
Isometric: stabilisers (I.e infraspinatus- stabilises shoulder)

Question 7

Groups of skeletal muscles based on primary actions;-

Agonist

Antagonist

Synergist

Answer 7

Agonist: (aka prime mover) - muscle that contracts to produce a particular movement (I.e. Extending forearm)

Antagonist: muscle whose actions oppose that of agonist - used to stabilise

Synergist: muscle that assists the agonist in performing action

Question 8

Skeletal Muscle Characteristics and 5 functions

Answer 8

-Striated (marked by stripes or bands)
-single muscle may contain 100s of 1000s of fibres
Functions:
-body movement
-maintenance of posture
-temp. regulation (heat produced during contraction)
-Storage & Movement of materials
-Support (i.e. pelvic floor)

Question 9

Cardiac Muscle characteristics

Answer 9

• individ. muscles arranged in thick bundles w/in heart wall
• striated, but shorter & thicker than skeletal
• 1 or 2 nuclei
• form Y shaped branches to join to adjacent muscle cells at junctions called intercalated discs
• are AUTORHYTHMIC = individ. cells can generate muscle impulse w/out nervous stimulation
• dependent on calcium for contractions
• large no. of mitochondria to generate large amount of ATP needed for constant work

Question 10

Smooth Muscle Characteristics

Answer 10

• composed of short muscle cells w/ fusiform shape
• single, centrally located nucleus
• do have thick & thin filaments - not precisely aligned (sacromeres not easily visible)
• slow contraction, resistant to fatigue (sustained over long period of time)
• is involuntary

Question 11

Atropy vs. Hypertrophy

Answer 11

Atropy: Wasting of tissue that results in reduction of muscle size, tone & power

• from decreased stimulation
• when extreme atrophy occurs, loss of gross muscle function permanent

Hypertrophy: An increase in muscle ire size

• Increase in number of myofibrils per fibre in fast fibres
• may be increased by exercising
• results in more mitochondria, larger glycogen reserves and increases ability to produce ATP

Question 12

Levers & Joint Biomechanics;-

First, second and third class lever (plus examples)

Answer 12

Lever: elongated, rigid object that rotates around fixed point called a fulcrum (e.g. seesaw)

• First Class Levers: Fulcrum in middle b/w effort & resistance (e.g. pair of scissors, atlantoccipital joint of neck
• Second Class levers: Resistence b/w fulcium & applied effort - small force can balance large weight (i.e. foot is depressed *rare in body)
• Third class lever: Effort applied b/w resistance and fulcrum most common
  e. g. elbow

Question 13

Naming skeletal muscles

Answer 13

-Names usually provide clue to their identification
Examples;-

• Muscle action
• Specific body region
• muscle attachments
• orientation of muscle fibres (i.e rectus)
• muscle shape & size
• muscle heads/tendons of origin