Msk Physiology

Front 1

6 components of Synovial joint

Back 1

1) Ligaments

2) Fibrous capsule

3) Synovial Membrane

4)articular/hyaline cartilage on articulating part of bones

5) articular disc (not present in all synovial joints, found in knee, acromioclavicular, sternoclavicular, TMH)

6) Synovial fluid

7) fatty pad/Bursa (between synovial membrane and fibrous capsule)

Front 2

sesamoid bone is

Back 2

short bone that forms in tendon eg. patella bone

Front 3

Spongy bone is

Back 3

zone of thin interconnecting narrow bone trabeculae

Front 4

Bone composition

Back 4

70% inorganic bone salts- hydroxyapatite(calcium and phosphate)

30% osteoid

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osteoid composition

Back 5

Type 1 collagen fibers, ground substance (proteoglycans, glycosaminoglycans, hyaluronic acid) and osteocalcin

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cells of bone

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1) osteoblast

2) osteoclast

3) osteoprogenitor cells

4) osteocyte

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function of osteoblast

Back 7

secrete type 1 collagen and proteoglycans and alkaline phosphatase

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function of osteocyte

Back 8

is a mature osteoblast that has stopped producing osteoid

plays role in controlling extracellular conc of Ca2+ and PO4 by providing signals for bone remodeling and modeling

sense bone load

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osteoclast

Back 9

lies in Howships lacunae

microvilli forms ruffled border

multinucleated giant cell derived from fusion of precursor monocytes

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Features of spongy bone

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1) no independent blood supply, nutrients diffuse from ECF

2) Has trabeculae/spicules - network of ine irregular plates separated by intercommunicating spaces filled with haemapoietic cells

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Features of cortical/compact bone

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1) Outer circumferential lamella

2) interstitial circumferential lamella

3)inner circumferential lamella

4) haversian canals

5) osteons (haversian sytem)

6) volkman's canals

7) canaliculi

8) Sharpey's fiber

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Outer circumferential lamella

Back 12

Bone layers containing osteoblast of periosteum

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interstitial circumferential lamella

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irregular remnants of lamellae due to newly formed osteon being disposed between partly resorbed osteons formed earlier

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inner circumferential lamella

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bone layer lining the inside of cortical bone

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haversian canal

Back 15

Neurovascular channels containing blood vessels, lymphatics and nerves

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osteon

Back 16

consist of haversian canal + concentric lamellae around it --> canal is formed by osteoclast tunneling through compact bone and blood vessel and nerves grow into it

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volkman's canal

Back 17

channels piercing haversian canal at right angles, connecting the various haversian canals

Front 18

canculi

Back 18

minute interconnecting canals betwen adjacent lacunae, containng cytoplasmic extensions of osteocyte --> allow circulation of extracellular fluid and diffusion of metabolites between lacunae (within the lamellae) and vessels of haversian canal

Front 19

osteoclast activity stimulated by? 3 factors

Back 19

PTH, vitamin D, cortisol

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Osteoclast inhibited by? 2 factors

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estrogen and calcitonin

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What enzyme does osteoblast secrete that is a good indicator of its activity

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Alkaline phosphatase

Front 22

Regulation of plasma Ca2+ by which 3 hormone/vitamin

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1) Vitamin D ( in the form 1,25 dihydrocholecalciferol)

2) parathyroid hormone

3) calcitonin

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formation of 1,25 DHCC (calcitriol)

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1) Formation of cholecalciferol in skin by irradiation of dehydrocholestrol

2) conversion of cholecalciferol in liver to 25-dehydroxycholecalciferol

3) conversion of 25-cholecalciferol to 1,25 cholecalciferol by 1 alpha hydroxylase in kidneys (mediated by PTH)

Front 24

Actions of 1,25 DHCC

Back 24

1) On kidneys: increases calcium and phosphate reabsorption

2) on intestine: increases calcium absorption in duodenum and jejunum by increasing calbindin-D (calcium-stimulated ATPase in intestinal cells) and also increases phosphate absorption

3) on bone: stimulate osteoclast action

Front 25

parathyroid hormone secreted by

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chief cells of parathyroid gland

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action of parathyroid hormone

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1) on kidneys: decreases Ca2+ excretion by distal tubules and increases phosphate exretion and increases 1-alpha-hydroxylase action

2) on intestine via Vit D

3) on bone: increases osteoclast activity

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Elaborate on PTH action on bone

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1) rapid phase - activate existing osteoclast

2) slow phase by formation of new osteoclast

PTH binds to osteoblasts, which causes formation of membrane-bound RANKL on osteoblast. RANKL binds to RANK on osteoclast progenitor cells, causing them to differentiate into mature multinucleated osteoclasts which then develop a ruffled border and release proteolytic enzyme and H+

osteoblasts also produce OPG which competes with RANK for RANKL, inhibiting the differentiation into osteoclasts; PTH inhibits OPG formation

Front 28

regulation of PTH

Back 28

parathyroid cell membrane contains Ca2+ sensing receptors. When Ca2+ binds to receptor, phospholipase C is activated which then causes inhibition of PTH secretion.

Front 29

Familial hypocalciuric hypercalcemia is due to

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homozygous inactivation of CaSR gene

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calcitonin secreted by

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parafollicular cells in parathyroid gland

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Calcitonin action

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1) on bone: inhibits osteoclast and
decrease formation of osteoclast

2) kidney: increases renal excretion of ca and po4

3) on intestine: inhibits 1-alpha-hydroxylase hence decreasing intestinal reabsorption of ca

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endochondreal ossifictaion model

Back 32

1) formed from hyaline cartilage - cartilage undergoes appositional growth and forms primary ossification center and cartilage undergoes calcification

2) vascular ostegenic bud (blood capillaries and mesenchymal cells) invades poc

3) osteoblasts form spongy bone

4) epiphyseal growth plate continues to grow in between poc and soc (where osteoblast started to form spongy bone)

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sarcomere

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from one Z line to another Z line

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muscle contraction causes shortening of which bands

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I bands and H zone. No change in A band length.

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titin filament

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runs from Z discs and M line

Front 36

How is ATP involved in muscle contraction

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Binding of ATP to myosin allows myosin to detach from actin and ATP is hydrolysed to free myosin head for next binding

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A band is the length of

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1 entire myosin

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I bands are the length of

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Actin

Front 39

when contracted, which bands overlap

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I bands

Front 40

By what mechanisms is peak force of skeletal muscle increased?

Back 40

1) summation

2) recruitment

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summation refers to

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increasing the frequency of stimulation -> summation of twitches(up to a certain limit beyond which tetany sets in and maximum strength is reached regardless of further stimulation)

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recruitment refers to

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activating more motor units, which in turn engage
more muscle fibers,(causing greater force production) with greter stimulation

Front 43

golgi tendon organ and the reflex it facilitates

Back 43

has sensory nerve endings that detects tension in muscle and stimulates inhibitory interneuron in spinal cord inhibiting the activity of motor neuron innervating that muscle, relaxing it

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location of golgi tendon organ

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in tendons near myotendinous junction

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types of muscle fibre

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Type I: slow oxidative(red) - slow twitch and fatigue resistant - aerobic

Type IIa: fast oxidative (red) - fast twitch

Type IIb: fast glycolytic (pink/white) - fast twitch --anaerobic with glycogen stores

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type IIb fast glycolytic fibres - why is it able to generate the highest peak muscle tension?

Back 46

has the highest myosin ATPase velocity

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types of contraction

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1) isometric - constant length (force generated but no movement)

2) isotonic - constant tension ( concentric and eccentric) with change in mucle length

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concentric isotonic contraction

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muscle fibre shortens (carry load) eg. bicep curl

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eccentric isotonic contraction

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muscle fibre lengthens (resisting load) eg. recovery from bicep curl/putting down a load

Front 50

intercalated discs in cardiac muscle

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dense intercellular junctions at Z lines --> provide points of anchorage for myofibrils + allows rapid spread of contractile stimuli from one cell to another so that the heart contracts as one functional syncitium

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contraction mechanism in smooth muscles

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Ca2+ binds to calmodulin, which activates Myosin Light Chain Kinase, which goes on the phosphorylate myosin head and facilitate binding to actin filaments

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glycosaminoglycans

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polysaccharide consisting of repeating disaccharide units

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Main types of collagen (2)

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Type I - in bones, tendon, blood vessels

Type II - in articular cartilage

Type IX - in cartilage

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Process of nerve recovery

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1) wallerian degeneration

2) retrograde degeneration

3) transneural degenration

4) Nerve regeneration

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wallerian degeneration refers to

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degeneration of nerve fragment distal to site of lesion - involves fragmentation of ER, dissolution of neurofilaments and microtubules, swelling and lysis of axonal mitochondria

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retrograde degeneration extends up to

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first node of ranvier or first sustained collateral axon branch

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nerve regeneration involves

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1) Schwann cells multiplying and growing, forming a solid cord - Bands of Bungner within endoneural tube

2) Schwann cells also secrete growth-promoting factors

3) plasma membrane of Schwann cells separate from adjacent basal lamina, creating an annular compartment

4) axonal sprouts grow from all direction from proximal axon

5) Growth cone tips at the tips of axon grow into the distal annular compartment which contain multiple filopodia that adhere to the basal lamina, using it as a guide

6) all but one degenerates and fill the distal tube

7) lastly - reversal of chromatolysis (nucleus returns to the center of the cell, nucleoproteins reorganise into Nissl granules and golgi body reappear