Muscle ch.6

• Muscular Systems Functions

  1. mobility, all mobility at the macroscopic level
  2. resist forces: maintain station and posture
  3. provide shape to the body -40% of body weight
  4. ventilation and circulation (lymph)
  5. sense - eyes and ears
  6. metabolic heat
  7. electric fields
  8. blood circulation
  9. digestion
  10. excretion
• Muscle types

  1. histology: smooth, cardiac, skeletal
  2. Nervous control: involuntary vs voluntary (immediate control)
  3. location and action (Visceral- hypomere-organs, vessels and ducts) vs somatic (somites- skeletal)
  4. Embryology - cranial vs postcranial / somitomeres vs somites
  5. colour - red muscle (myoglobin) and white(fast twitch) muscle
• Smooth muscle

  • short, spindle shaped, uninucleate, no striated
  • typically in sheets that wrap around organs - gut, urinary bladdar, uterus, blood vessels
  • involuntary
  • individual cells
  • to do with visceral gut but they do migrate (cells)
  • Does not tire - in contracted state it exerts NO energy
  • smooth muscle in skin called erectorpillie
  • Cardiac skeletal muscle one r fused together - also have nuclue in the middle

  
• Mechanisms

  • two filament proteins slide past each other to create a muscle contraction, actin and myosin
  • Sarcomeres in skeletal and cardiac muscle cells orderly, striations, not orderly in smooth muscle cells
  • Titan proteins - biggest proteins in the vertebrates

  
• Cardiac Muscle

  • must've been derived from protochordates
  • synapomorphy of vertebrates
  • originates from visceral mesoderm
  • tube shaped, branched, uni or multinucleate, striated
  • cells connected to each other by intercalated discs (fit together)
  • only in the heart, only in vertebrates
  • involuntary, inturistic contraction

  
• Skeletal Muscle

  • long tube shaped, unbracnhed, multinuleate, strated
  • associated with skeleton (bone, cartilage, ligaments)
  • voluntary
  • almost entirely sarcomeres
  • all comes from somites, specifically myotome

  
• Skeletal Muscle

  • muscle organ
  • made of muscle fibers bundled into fascicles embedded in connective tissue

  
• Skeletal muscle

  • connective tissue extends beyond the fascicles as tendons that attach to the skeleton

  
• Terminology -

  • origin -> (close to midline) belly -> insertion (farther away, distally)

  
• Terms

  • Extensor - increases angle -triceps
  • Flexor - decreases angle - biceps
  • abductor - away from midline - deltoid (moves arm out)
  • adductor - towards the midline - pectoralis major - chest
• Terms

  • Levator - elevates a structure - Levator palatoquadrate
  • depressor - lowers a structure - pectoral depressor
  • Supinator - rotate upwards - fist up
  • Pronator - rotate downward - fist down
• Terms

  • protractor - extend from base - tongue
  • retractor - bring back to base - tongue
  • sphincter - make openings smaller - esophageal
  • Dilator - enlarge opening - iris

  
• Action

  • muscles work in only one manner - contraction
  • Muscles work in pairs: agonist/ antagonist (act as levers/ pullys)
  • extensor/ flexor = triceps/ biceps
• Action

  • lever: a rigid bar that may be pushed or pulled upon to rotate about a fixed point
  • may be used to multiply force or multiply speed
  • bones and joints act as levers, muscles only pull
• Levers (3, parts)

  1. Fulcrum - point of joint rotation
  2. Load - point of resistance to be moved
  3. Effort - point of effort, attachment of muscle to bone

  
• Action

  • Class 1 lever - scissors 9(fulcrum in the middle)
  • Class 2 lever - resistance in the middle (the door)
  • Class 3 lever - effort in the middle (Tennis racket)

  
• Action - Class 1

  • Fulcrum: atlas/ occipital articulation (RED)
  • resistance (load): skull (PURPLE)
  • Effort: Splenius Capitis (contract- look up) (PINK)

  
• Action - Class 2

  • Fulcrum - toes
  • Resistance (load) - body
  • Effort - gastrocnemius
  • originates in condyle of femur, inserts on calcaneus via achilles tendon

  
• Action - Class 3 (Tetrapods appendicular skeleton)

  • Fulcrum - elbow, trochlea of humerus
  • Resistance (load) - forearm, ulna
  • Effort - biceps brachii - originates in scapula inserts on radius

  
• Action

  • lever advantage trade off
  • Distal insertion = strength
  • Proximal insertion = speed

  
• Cat vs armadillo

  Cat - 1-9

  armadillo - 1.5

  
• Nomenclature -

  • Action - flexor, extensor, abductor, adductor (ex: levator palati quaradi, rasies the palatoquadrate)
  • Direction of the fibers - rectus= straight- oblique=diagnoal-transverse=across
  • Location - femoris
  • Divisons - biceps and triceps
• Nomenclature

  • Shape- deltoid (back usually) rhomboideus, trapezius
  • attachment - ex sternocleidomastoid - origin = sternum+clavical, insertion: mastoid process of temporal
  • Size - ex gluteus maximus

  
• Embryology

  • myotome from the somites form the epaxial and hypaxial muscles and limb musculature

  
• Embryology -

  • myotome from the somites form the expaial and hypaxcial muscle and limb musculature
  • parietal mesenchyme gives rise to limb skeleton smooth muscle
  • Splanchnic mesoderm forms the smooth msucle of the viscera and acardiac muscles

  
• Embryology

  • anterior somites remain connected somitomeres
  • anterior somites and somitomeres contribute to the pharyngeal musculature and extrinsic eye muscles

  
• Regions

  • axial (cranial) - embryology: somitomeres/ somites (epibranchial GR/hypobranchial-LB)
  • Postcranial - embryology: somites (epaxial-DB/hypaxial-PP)
  • Splanchnocranium - embryology - somitomeres NOT hypomere. (branchnimeric- RED)

  
• Regions -

  • Appendicualr - embryology: somites (pectoral- PINK (raise and lower fins) and pelvic)
  • Visceral - Embryology: hypomere, smooth muscle of organs and blood vessels (eretors (erectopillie), of hair and feathers in cardiac muscle)

  
• Epibranchial (preotic myotomes become extrisic eye muscles)
• Epibranchial (preotic myotomes become extrisic eye muscles)

  1. Cranial nerve III (tract of the brain) dorsal, ventral, medial rectus and ventral oblique
  2. Cranial nevre IV dorsal oblique
  3. Cranial nerve VI lateral rectus
  4. SLIDE 32

  
• Hypobranchial

  • originate from post cranial somites
  • evideced by spinal cord innervation
  • opening lower jaw in fishes
  • throat, hyoid, larynx & tongue in tetrapods, ex (genioglossus - protraction, styloglossus- retraction - from spinal cord under brain)

  
• Branchiomeric

  • from somitomeres and somites, NOT splanchnic mesoderm
  • primitively for buccal pump
  • cranial and spinal innervation
  • XI is entrapped in the cranium of amniotes

  
• Branchiomeric

  • Mandibular arch
  • cranial Nevre V - #5
  • adductor mandibulae & levator palatoquadrate(tetrapods loose this) in fish
  • Masseter(bc we are chewers), temporalis (closer) and pterygoideus(side to side chewing) in mammals

  
• Branchiomeric

  • Hyoid arch #7
  • Levator hyomandibula in fishes
  • stapedius in mammals
  • small interhyoidus in fishes, extensive facial muscles in mammals
  • in tetrapods irs now for hearing- stabilizes stapes

  
• Branchiomeric

  • posterior arches
  • buccal pump in fishes (gill puches) (9+10) 11 for the poserirmore - not cranial nerve)
  • larynx + throat in tetrapods
  • some fuse to cucullaris
  • trapezius and mastoids in mammals (neck and shoulder girdle )

  
• Epaxial/ Hypaxial

  • largest muscles in fish, locomotion (postcranial)
  • no horizontal septum in lampreys
  • relatively short fibres, deep zig- zagging to increase length (anterior -> posterior) more range of motion

  
• Epaxial / Hypaxial

  • trend to reduce myosepta in tetrapods, form sheets
  • hypaxial musculature extensively modified, forming layers with fibers in alternate orientations ventaltion and trunk mobility (side to side/ up and down)
• Electrogenic Organs

  • modified muscles in aquatic vertebrates
  • disc shaped cells, electroplaques
  • generates a 0.15V potential from action potential
  • may be combined in series for voltage or in parallel for current

  
• Electrogenic Organs

  • independently evolved (convergent evolution) from axial, branchiomeric and even musculature
  • strongly electric fish stun prey and or repel predators
  • weakly electric fish sense environment live in murky waters
  • communication as well - use electric currents to conduct currents and sense objects