Exam 2 Flashcards
effect of low plasma Ca on kidneys:
- increased parathyroid hormone secretion
- increase Ca reabsorption in kidneys (decrease phosphate reabsorption)
- increased calcitrol activation
- increased calcitrol in plasma
- kidneys and digestive tract absorb Ca
what else do you need to absorb Ca?
calcitrol (vitamin D)
does calcitonin play a bigger role in children or adults?
children
-keeps calcium in bone
most important function of bone:
calcium homeostasis
needed for cellular processes
if ingestion of Ca stops then:
bone is left to supply plasma levels (resorption)
effect of renal failure on calcium:
-renal failure doesn’t allow reabsoption so PTH stimulates more on bone to increase plasma Ca levels
effect of bone calcification from aging:
diminished:
- loading
- GH/IGF
- testosterone
effect of aging on bone resorption:
-resorption increased from diminished estradiol
effects of aging on calcium metabolism:
- diminished absorption from digestive tract
- diminished reabsorption from kidneys
- diminished calcification
- increased bone resorption
effect of growth hormone on bone length growth:
- increased deposition of protein by chondrocytic and osteogenic cells
- proliferation of chondrocytic and osteogenic cells
- conversion of chondrocytes into osteogenic cells
effect of androgens on bone length growth
- similar to GH
- increased deposition of calcium salts closes the growth plate
effect of T3 and T4 on bone length growth:
-promotes osteoblastic activity
and synthesis of bone matrix
where does bone length growth occur?
epiphyseal cartilage
process of growth of bone circumference:
- osteoblasts create new bone on outer surface by secreting osteoid, then calcium phosphate (strong heavy)
- osteoclasts break down bone on inner surface by secreting acid/enzyme
difference between girls/boys bone circumference:
- boys have greater periosteal diameter (outer)
- girls have narrowing of the endocortical surface
bone modeling:
- independent action of osteoclasts and osteoblasts
- effects size/shape bones during lengthening and mechanical load
Bone remodeling:
- coupled action of osteoclasts and osteoblasts
- osteoclasts first resorb pit, osteoblasts form and mineralize area
- in response to fatigue and damage
osteoblasts stimulated by:
GH/IGFs
compressive forces
osteoblasts inhibited by:
cytokines
osteoclasts stimulated by:
PTH
cortisol
cytokines
osteoclasts are inhibited by:
calcitonin
estrogen
chondrocytes are stimulated by:
GH/IGFs
chondrocyte inhibitors:
sex hormones
effect of glucocorticoids on bone:
- inhibits osteoblasts for calcification
- stimulates osteoclasts for bone resorption
- inhibits Ca absorption from digestive tract
- inhibits Ca reabsorption from kidneys
dietary factors that promote bone health:
exercise
low sodium diet
factors that diminish bone health
- inadequate calcium and vitamin D intake
- high caffeine intake
- high carbonated soda intake
- excessive alcohol use
- smoking
- high protein intake
- inadequate caloric intake
loading of bone causes what mechanical effect?
shear stresses in canaliculi
- osteocytes detect mechanical strain
- bone is more responsive to dynamic than static loading
- bone accomodates to prolonged mechanical stimuli
- bone tolerates compression better than tensile force
muscle secretes:
- growth factors
- extracellular matrix molecules
- inflammatory cytokines
myostatin
- only cytokine produced from skeletal muscle
- huge impact on muscle atrophy
neuromuscular effect of immobilization:
reduces muscle activation in old but not young adults
structural effect of immobilization:
- aging results in less loss of muscle mass with immobilization
- aged muscles have a diminished capacity to restore muscle size
satellite cells:
- muscle speciic stem cells
- can be induced to proliferate and differentiate in response to inury, exercise, stretch, and denervation
myonuclear domain
ratio of skeletal muscle nuclei to volume of cytoplasm
-each nucleus regulates protein synthesis within a given cell volume
satellite cell activation process:
- injury activation
- asymmetric division (outside sarcolemma)
- myoblast maturation
- myoblast fusion (donates nucleus)
effect of exercise on connective tissue from immobilization:
both low intensity and high intensity exercise decreased amount of CT drastically
effect of exercise on decreased capillarity from immobilization:
high intensity training increased capillarity number the most
effect of exercise on decreased fiber size from immobilization:
high intensity restored a little more than low intensity
will have a loss fo muscle mass within how long?
14 days
if immobilizaion after a strain/contusion is prolonged:
-the regenerated myofibers with remain atrophic and disoriented
systemic positive factors of muscle growth:
- IGF-1
- GH
- Testosterone
systemic negative factors of muscle growth:
-Myostatin (produced by skeletal muscle)
loss of muscle type with aging vs immobilization:
aging: more loss of Type II fiber
immobilization: more loss of Type I
effects of chronic disuse:
- increase collagen, adipose
- decrease myofibers
- poor Ca release during excitation
aged muscle has diminished capacity to:
restore muscle size
difference between multiple rep injury vs 1 time heavy injury:
- MR injury requires satellite cell function for recovery
- 1 time injury doesn’t require satellite cell for recovery
reasons older muscle injury results in generation of fewer myoblasts:
- satellite cells have more trouble responding to stimuli
- smaller inflammatory response
- decline in environmental stimulus
difference in recovery time for old vs young muscle:
with same amount of injury old muscle takes at least 2x longer to recover
