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

Trade-off

Arrows indicate direction of shortening

1. Which has more force associated with it?

2. Which has more range of motion?

2

4

a b

Types of Motor Units

I. Slow contracting oxidative – “redder”• Soleus, postural muscles of neck

II. Fast contractinga. Oxidative (still red) – gracilis (not common)

• Reflects the muscle fibers• Lots of mits• Contract long periods w/o fatigue

b. Glycolytic or Non-oxydative (“whiter”) – gastrocnemius, arm muscles

• 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 Muscles1. 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 Functional Morphology of the Middle Ear of Middle Ear of Ctenomys Ctenomys

talarumtalarum (Rodentia: (Rodentia: Octodontidae)Octodontidae)

E.C., Schleich, C., Bush (2004) Functional Morphology E.C., Schleich, C., Bush (2004) Functional Morphology of the of the Middle Ear of Middle Ear of Ctenomys talarumCtenomys talarum (Rodentia: (Rodentia: Octodontidae. J of Mamm, 82: 290-295.Octodontidae. J of Mamm, 82: 290-295.

CtenomysCtenomys talarum talarum Solitary subterranean rodentSolitary subterranean rodent

Significant features: Significant features: -enlarged middle-ear cavity-enlarged middle-ear cavity-round and larger eardrum without -round and larger eardrum without

pars pars flaccidaflaccida-no connection between malleus and -no connection between malleus and tympanic bonetympanic bone-partial fusion of malleus with incus-partial fusion of malleus with incus-nearly flat stapedial footplate-nearly flat stapedial footplate-Absence of stapedial artery-Absence of stapedial artery

Continued…Continued…

--reduced tensor tympanireduced tensor tympani

-absence of stapedial muscle-absence of stapedial muscle

120 and 160 g in body mass for females 120 and 160 g in body mass for females and males respectivelyand males respectively

Vocalizations are moderate to low in Vocalizations are moderate to low in frequency which common when living in frequency which common when living in underground environments. underground environments.

ObservationsObservations The physical environment exerts strong The physical environment exerts strong

effects on design of animal displays, but the effects on design of animal displays, but the influence of receiver properties on their influence of receiver properties on their evolution distinguishes displays from other evolution distinguishes displays from other traits.traits.

In mammals, hearing properties of the In mammals, hearing properties of the auditory organ are related strongly to middle-auditory organ are related strongly to middle-ear morphology.ear morphology.

According to the optimality principle, physical According to the optimality principle, physical characteristics of vocalizations should reflect characteristics of vocalizations should reflect adaptation to the physical environment, body adaptation to the physical environment, body size, or hearing ability.size, or hearing ability.

The Middle EarThe 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

HypothesisHypothesis

C. talarumC. talarum and and other other subterranean subterranean speciesspecies should have should have anatomical features anatomical features that optimize low-that optimize low-frequency hearing. frequency hearing.

Materials and MethodsMaterials and Methods

Eight adult males and 14 adult females Eight adult males and 14 adult females captured in Mar de Cobo using plastic live captured in Mar de Cobo using plastic live traps set at fresh surface moundstraps set at fresh surface mounds

In lab animals were killed by cervical In lab animals were killed by cervical dislocationdislocation

Naso-occipital length and greatest zygomatic Naso-occipital length and greatest zygomatic width measured with digital calipers (0.01 width measured with digital calipers (0.01 mm)mm)

Bullar length, width, and depth measuredBullar length, width, and depth measured With ocular micrometer (0.06 mm) length and With ocular micrometer (0.06 mm) length and

diameter of auditory meatus, diameter of diameter of auditory meatus, diameter of eardrum, length of head of malleus, length of eardrum, length of head of malleus, length of lever arm of malleus, length of incus etc.lever arm of malleus, length of incus etc.

ResultsResults Enlarged middle-ear cavityEnlarged middle-ear cavity Round and large eardrum without pars Round and large eardrum without pars

flaccidaflaccida Lack of connection between malleus and Lack of connection between malleus and

tympanic bonetympanic bone Partial fusion of malleus with incusPartial fusion of malleus with incus Nearly flat stapedial footplateNearly flat stapedial footplate Reduced (tensor tympani) or absent Reduced (tensor tympani) or absent

(stapedial) middle-ear muscles(stapedial) middle-ear muscles Reduced Pinna which accounts for poor sound-Reduced Pinna which accounts for poor sound-

localization capacities of subterranean formslocalization capacities of subterranean forms

Comparison SpeciesComparison Species Geomys bursarius- Geomys bursarius- medium to small medium to small

sized, dark brown gophers sized, dark brown gophers

Spalax ehrenbergiSpalax ehrenbergi - blind mole rat - blind mole rat

Heterocephalus glaber- Heterocephalus glaber- naked mole-ratnaked mole-rat

ClyomysClyomys and and OctodonOctodon

Cryptomys hottentotus- Cryptomys hottentotus- common mole-common mole-ratrat

ComparisonComparison Reduced size of pinna shared with Reduced size of pinna shared with Spalax Spalax

ehrenbergiehrenbergi and and Heterocephalus glaberHeterocephalus glaber Round eardrum wit no evident pars flaccida Round eardrum wit no evident pars flaccida

occurs in occurs in C. talarumC. talarum, , S. ehrenbergi, G. S. ehrenbergi, G. bursarius, and Cryptomys hottentotusbursarius, and Cryptomys hottentotus

Middle ear cavity of Middle ear cavity of C. talarumC. talarum enlarged in enlarged in comparison with some surface dwellers of comparison with some surface dwellers of Caviomorpha, although approximating the Caviomorpha, although approximating the size of the middle ear of size of the middle ear of Geomys bursariusGeomys bursarius

Walls of middle-ear cavity of Walls of middle-ear cavity of C. talarumC. talarum, , ClyomysClyomys, and , and OctodonOctodon are cancellous bone are cancellous bone covered with compact bonecovered with compact bone

ConclusionConclusion

The middle ear of The middle ear of C. talarumC. talarum has anatomical has anatomical features that are probably adaptations to features that are probably adaptations to keep of enhance low-frequency sounds keep of enhance low-frequency sounds transductions.transductions.

These modifications agree with the These modifications agree with the dominant low-frequency vocalizations of dominant low-frequency vocalizations of C. C. talarumtalarum and with the best transmission and with the best transmission frequency in subterranean environments.frequency in subterranean environments.

Modifications also found in several Modifications also found in several species of unrelated subterranean species of unrelated subterranean rodents. rodents.