skeletal system Flashcards
structural and physiological functions of skeletal tissue:
structural:
- support & protection for vital organs
- locomotion = levers propelled by muscular force
physiological:
- site of hematopoiesis = RBC formation
- immune function = WBC formation
- stores Ca2+ & phosphates = nerve conduction, muscular contraction, blood clotting
four different types of bone:
- Long: femur: strength & leverage
- Short: carpel: strength & flexibility
- Irregular: vertebrae: protection & attachment
- Flat: scapula: protection & attachment
Contrast the two different types of bone tissue:
Cortical: compact, dense, or lamellar bone
- 80 to 90% calcified
- composed of osteo functional units
- 80% of skeleton (appendicular)
- mostly the shaft (diaphysis) of bone
Trabecular: spongy, less dense, or cancellous
- 15-25% calcified
- composed of struts/trabeculae functional units
- axial skeleton (skulls, ribs, vertebrae, sternum)
- mostly head (epiphysis) of bone
- metabolically active & site for osteoporosis
Compare the phases of growth, modeling, and remodeling involved in bone development:
Growth:
- Longitudinal growth: epiphyseal plate for height (cartilage later replaced)
- Oppositional growth: increased thickness/mass
Modeling:
- Micro modeling: cellular level determined bone type
- Macro modeling: bone formation/restoration (BMD/BMC)
Remodeling:
- bone turnover (bone metabolism)
- coupled process of resorption & formation
Contrast the three different types of bone cells:
- Osteoclasts: bone resorption; secrete digestive enzymes that phagocytize bone matrix (HCL)
- Osteoblasts: bone formation (secrete collagen I & II)
- Osteocytes: mature osteoblasts important in cellular communication & strain detection; may initiate calcification
Discuss the hormonal control of bone growth and remodeling:
Low blood calcium = need to increase Ca2+ in blood
- released PTH from parathyroid gland to stimulate osteoclasts for bone resorption
High blood calcium: need to decrease Ca2+ in blood
- release calcitonin from thyroid gland to stimulate osteoblasts for bone formation
- vitamin D aids in absorption if Ca2+ from intestines = increased Ca2+ in blood
Bone Growth: estrogen, testosterone, growth hormone, IGF-1
- estrogen:
1. promotes Ca2+ retention & inhibits PTH
2. promotes bone formation during exercise
3. decreased estrogen = increased resorption
What is the difference between osteopenia and osteoporosis?
Osteopenia: low BMD without increased fracture risk
- usually 1 to -2.4 standard deviations below average BMD for young women
Osteoporosis: low BMD with increased fracture risk
- usually less than -2.5 standard deviations below BMD average for young women
What are the important considerations that are needed to be followed concerning the best exercise response for bone health? (5)
- genetics
- gravity
- nutrition (Ca2+ & protein)
- physical activity
- hormones (regular cycle & estrogen)
Compare the two different types of osteoporosis:
Type I: post menopausal or estrogen deficient osteoporosis
- osteoclast-mediated = greater reabsorption, normal formation
Type II: age related/senile osteoporosis
- osteoblast-related = decreased formation, normal resorption
What are the controllable and non-controllable risk factors for osteoporosis?
Uncontrollable:
1. Age = old > young
2. Race = caucasian > African American
3. Sex = women > men
4. Family history = on mother’s side
5. Frame size = smaller frame > larger frame
Controllable:
1. physical activity
2. hormone levels- endocrine status
3. nutrition- Ca2+ intake
4. excessive alcohol intake
5. smoking
6. excessive caffeine intake
What are the four characteristics of skeletal muscle tissue?
- Contractility = ability to shorten & develop tension
- Extensibility = ability to be stretched
- Elasticity = ability to return to original length
- Irritability = ability to conduct an action potential
Contrast the three different layers of connective tissue associated with skeletal muscle:
- Epimysium = surrounds entire muscle
- Perimysium = surrounds bundles of muscle fibers (fascicle)
- Endomysium = surrounds individual muscle fibers
Describe and contrast the three different thin filaments:
Thin filament: contractile proteins
1. Actin: 2 strands appearing as a coiled double helix
G-Actin: globular actin
F-Actin: G-Actin strands together; filamentous actin
2. Tropomyosin: 1 TM regulates 7 G-Actins
- in groove of alpha helix
- long block binding sites
3. Troponin: 1 Tn regulates 1 TM
- TN-T: troponin tropomyosin
- TN-C: troponin calcium; allows binding of Ca2+
- TN-1: troponin inhibitory; keeps TM in place
Describe thick filament proteins associated with skeletal muscle:
Thick filaments:
1. Myosin: 2 globular heads & 1 long tail
- S1: heads from heavy meromyosin
- S2: neck allows for ratchet motion
- S1 & S2: ATP & ATPase
- tail is considered light meromyosin
Describe the sliding filament theory of contraction:
- Action potential depolarizes sarcolemma and travels down T-tubule
- Activates dihydropyradine receptors signaling
- ryanodine receptors on SR to release calcium from SR
- Calcium binds to Tn-C on thin filament & changes shape & moves tropomyosin
- exposes active binding sites on actin
- mutual attraction between actin & myosin
- they bind & form charged acts-myosin cross-bridge
- ATPase on neck region of myosin activated & breaks down ATP to produce a power stroke
- ADP is phosphorylated back to ATP causing myosin release from actin looking for new bind sites on actin
- relaxation:
- Ca2+ back to SR (Ca2+ ATPase Pump)
- Calequestrin: passive return
