Transcript CVA12
Muscle (continued) Recall the functions… • Muscular System – 1. Create tension along the axis of their fibers 2. Move bone or constrict a space 3. Homeostasis, protection Few notes on shortening and force production • Sarcomere – Relaxed – 2.5 um wide – Contracted – 2.0 um wide • Hence, each shortens by 0.5 um • Shortening determined by number of sarcs in a series Force - Histological • “Z-line” forces – Actin & myosin filaments connected to “z-line” proteins – Equal and opposite forces – Muscular force due to cross-bridges between actin and myosin differential protein conformations • Problem 1 – Optimum size of sarcomere – Solution: • double output of a single myofibril by adding another fibril • increase # of units in parallel to increase force Force - Gross • Problem 2 – Body size – Solution: change fiber orientation or gross muscular morphology – Trade-off between shortening and force production a Trade-off b Arrows indicate direction of shortening 1. Which has more force associated with it? 2. Which has more range of motion? 4 2 Types of Motor Units Slow contracting oxidative – “redder” I. • II. Soleus, postural muscles of neck Fast contracting Oxidative (still red) – gracilis (not common) a. • • • Reflects the muscle fibers Lots of mits Contract long periods w/o fatigue Glycolytic or Non-oxydative (“whiter”) – gastrocnemius, arm muscles b. • • Relies on glycolysis for ATP production Fatigues rapidly Definitions More terminology related to the system • Tendon – join muscles to bone • Ligament – bone to bone • Aponeurosis – tough, flat sheet of CT distributing tension of muscle • Fascia – loose CT binding muscle to muscle, skin to muscle • Insertion – muscle attachment point, relatively free to move • Origin – the relatively fixed attachment – Relative terms unless dictated by embryology Muscle action • Flexor – reduce angle between adjacent bone • Extensor – increase that angle • Adductor – move parts towards sagittal plane • Abductor – move parts away from that plane • Levators – raise parts. • Depressors – lower parts. • Protractors – push part away from its base. • Retractors – draw it back. • Sphincters--constrict openings. • Constrictors--compress spaces. • Dilators--oppose both of above. • Supinators--rotators that turn soles of hands or feet upward. • Pronators--turn them downward. • Antagonists--opposing muscles. • Synergists--muscles that supplement each other – groups (gluteals) Naming of Muscles 1. Orientation of fibers (oblique, rectus). 2. Actions (levator scapulae, flexor digitorum, adductor mandibulae). 3. Shapes (deltoid, rhomboideus, serratus, trapezius). 4. Positions (pectoralis, gluteus, temporalis, thoracis, supraspinatus). 5. Attachments (geniohyoid, cleidobranchialis, xiphihumeralis). 6. Number of subdivisions (quadriceps, biceps, digastric). Functional Morphology of the Middle Ear of Ctenomys talarum (Rodentia: Octodontidae) E.C., Schleich, C., Bush (2004) Functional Morphology of the Middle Ear of Ctenomys talarum (Rodentia: Octodontidae. J of Mamm, 82: 290-295. Ctenomys talarum Solitary subterranean rodent Significant features: -enlarged middle-ear cavity -round and larger eardrum without pars flaccida -no connection between malleus and tympanic bone -partial fusion of malleus with incus -nearly flat stapedial footplate -Absence of stapedial artery Continued… -reduced tensor tympani -absence of stapedial muscle 120 and 160 g in body mass for females and males respectively Vocalizations are moderate to low in frequency which common when living in underground environments. Observations The physical environment exerts strong effects on design of animal displays, but the influence of receiver properties on their evolution distinguishes displays from other traits. In mammals, hearing properties of the auditory organ are related strongly to middle-ear morphology. According to the optimality principle, physical characteristics of vocalizations should reflect adaptation to the physical environment, body size, or hearing ability. The Middle Ear - (1) Malleus ; (2) Malleus ligament ; (3) Incus ; (4) Incus ligament; (5) Stapes muscle (stapedius); (6) Stapes footplate; (7) Eardrum; (8) Eustachian tube; (9) Malleus muscle (tensor tympani); (10) Nerve (chorda tympani) sectioned Hypothesis C. talarum and other subterranean species should have anatomical features that optimize low-frequency hearing. Materials and Methods Eight adult males and 14 adult females captured in Mar de Cobo using plastic live traps set at fresh surface mounds In lab animals were killed by cervical dislocation Naso-occipital length and greatest zygomatic width measured with digital calipers (0.01 mm) Bullar length, width, and depth measured With ocular micrometer (0.06 mm) length and diameter of auditory meatus, diameter of eardrum, length of head of malleus, length of lever arm of malleus, length of incus etc. Results Enlarged middle-ear cavity Round and large eardrum without pars flaccida Lack of connection between malleus and tympanic bone Partial fusion of malleus with incus Nearly flat stapedial footplate Reduced (tensor tympani) or absent (stapedial) middle-ear muscles Reduced Pinna which accounts for poor soundlocalization capacities of subterranean forms Comparison Species Geomys bursarius- medium to small sized, Spalax ehrenbergi - blind mole rat Heterocephalus glaber- naked mole-rat Clyomys and Octodon Cryptomys hottentotus- common mole-rat dark brown gophers Comparison Reduced size of pinna shared with Spalax ehrenbergi and Heterocephalus glaber Round eardrum wit no evident pars flaccida occurs in C. talarum, S. ehrenbergi, G. bursarius, and Cryptomys hottentotus Middle ear cavity of C. talarum enlarged in comparison with some surface dwellers of Caviomorpha, although approximating the size of the middle ear of Geomys bursarius Walls of middle-ear cavity of C. talarum, Clyomys, and Octodon are cancellous bone covered with compact bone Conclusion The middle ear of C. talarum has anatomical features that are probably adaptations to keep of enhance low-frequency sounds transductions. These modifications agree with the dominant low-frequency vocalizations of C. talarum and with the best transmission frequency in subterranean environments. Modifications also found in several species of unrelated subterranean rodents.