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Physiology Flashcards

1
Q

Connective tissue

A 
1. Cells: 
  A. Fibroblasts (resident)
  B. Macrophage (immigrant)
  C. Mast cells
  D. Plasma cells
2. Fibers: 
  A. Collagen 
  B. Elastic
  C. Reticular
3. ECM components
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2
Q

Hydroxyapatite

A

More Ca2+ and PO4 than needed
1. Inhibitors prevent xs precipitation
A. Pyrophosphate

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3
Q

Cleidocranial dysplasia

A

Birth defect

  1. Affects bone and teeth
  2. RUNX2 = runt related transcription factor 2
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4
Q

Osteogenesis imperfecta

A

Group of genetic disorders

  1. Brittle bone
  2. Osx (osterix) = transcription factor Sp7
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5
Q

Pages disease

A

Inc. osteoclasts activity

  1. Inc serum PO4 , urinary hydroxyapatite, and osteocalcin
  2. Mosaic pattern of lamellar bone
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6
Q

Bone resorption

A
  1. Integrins bind vitronectins on matrix surface -> seal w/ osteoclast
  2. Osteoclasts -> H+ and acid pro teases into lacunae
  3. V-type H+ pump and ClC7 mediate acid secretion at ruffled border mem
  4. Carbonic anhydrase (CA): in cytosol supplies H+
  5. Cl-HCO3 exchangers in mem opp ruffled border
  6. Clathrin: mediates vesicle formation
  7. TRAP (tartrate resistant acid phosphatase) = metalloenzyme
    A. In osteoclasts and macrophages
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7
Q

Bone formation

A
  1. Intramembranous osteogenesis
    A. Mesenchyme -> woven bone -> lamellar bone
  2. Endochondral osteogenesis
    A. Cartilage -> bone formation
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8
Q

Osteoclast signaling

A
  1. Inhibition
    A. Calcitonin: dec plasma Ca2+
    B. Adenlyl cyclase (AC) -> cAMP
    C. Protein kinase A (PKA): P from ATP to ser or the on substrate
  2. Stimulation
    A. IL-6 -> RANKL expression on osteoblasts
    B. Osteoprotegrin (OPG) from osteoblasts and osteogenic stromatolites cells
    1. Bind RANKL -> prevent binding RANK
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9
Q

Signaling steps in resorption

A
  1. PTH binds osteoblast receptors
  2. Form RANKL and release M-CSF (macrophage-colony stimulating factor)
  3. RANKL binds RANK and M-CSF binds receptors on preosteoclasts
  4. PTH -> dec OPG inhibits preosteoclasts -> mature osteoclasts
    A. OPG binds RANKL
  5. Osteoclasts -> ruffled border and release lysozymes
  6. Osteocytes and blasts encased in bone matrix
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10
Q

WNT/Beta-catenin signaling pathway

A
  1. WNT from osteoprogenitors bind LRP5/LRP6 on osteoblasts -> Beta-catenin and inc OPG
    A. Inc bone, dec osteoclasts
  2. Sclerostin from osteocytes inhibits WNT/beta-catenin
  3. BMPs bind transmembrane ser/thr kinase receptors -> heterotopic bone formation
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11
Q

PTH

A
  1. Parathyroid chief cells
  2. Greater effect on [Ca2+] than calcitonin
  3. Inc [Ca2+] in blood by inc osteoclast activity
  4. Secretion regulated by [Ca2+] plasma
  5. Responses
    A. Bone: inc osteoclasts -> inc Ca2+ blood
    B. Intestine: calcitrol -> inc Ca2+ absorption -> inc Ca2+ blood
    C. Kidney: calcitrol -> inc Ca2+ reabsorption -> inc Ca2+ blood
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12
Q

Calcitonin

A
  1. Thyroid c-cells
  2. Dec Ca2+ plasma
  3. Responses
    A. Bones: dec osteoclast -> inc Ca2+ bone and dec Ca2+ blood
    B. Intestines: dec PTH and calcitiol -> dec Ca2+ absorption -> dec Ca2+ blood
    C. Kidney: dec calcitriol-> dec Ca2+ reabsorption -> dec Ca2+ blood
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13
Q

Phosphate homeostasis

A
  1. Regulators
    A. PTH -> dec Pi reabsorption kidneys
    B. Active vitamin D from renal tubule cells
    C. FGF23 from osteocytes
    1. [Pi]plasma feeds bask on osteocytes
  2. Distributed thru tissues
  3. Tissue damage -> hyperphosphatemia -> complex Ca2+ -> hypocalcemia
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14
Q

Costameres

A

Facilitate lateral transmission of force of contraction
1. Stabilize sarcolemma
2. Protein complexes
A. Dystrophin-glycoprotein complex (DGC)
B. Integrin-vinculin-talin complex

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15
Q

Isotonic contraction

A
  1. Shortens muscle

2. Enough force to move load

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16
Q

Isometric contraction

A

Muscles don’t shorten

1. Can’t move load

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17
Q

Isotonic eccentric contraction

A

Muscle lengthens

18
Q

Transition from fast to slow twitch muscles

A
  1. Action potential
  2. Ca2+ -> CaN
  3. NFAT dephosphorylated -> into nucleus
  4. Slow-fiber gene expression
  5. Action potential
  6. Ca2+ into nucleus -> CaMK -> HDAC phosphorylated -> inhibits HDAC
  7. If not inhibited HDAC -> MEF2 -> slow fiber expression
19
Q

Types of muscle fatigue

A
  1. Central -> CNS changes
  2. Peripheral
  3. High-frequency
  4. Low-frequency
  5. From ATP depletion, lactic acid accumulation, and glycogen depletion
20
Q

Neuron action potential

A 
1. Depolarization: Na+ -> inside cell
  A. [Na+] never higher inside than outside -gradient doesn’t change
2. Repolarization: K+ open
  A. K+ most permeable => resting membrane potential approaches Nearnst potential
3. Hyperpolarization: action potential approaches K+ potential
4. Two Na+ gates
  A. Activation
  B. Inactivation
  *open fast
5. K+ gate (only 1)
  A. Activated at same time as Na+
  B. Slower
6. Hyperkalemia 
  A. Inactivation gates close
  B. Can’t start new action potential
  C. Skeletal and cardiac muscl
21
Q

Neuromuscular transmission at skeletal muscles

A
  1. Action potential
  2. Ca2+ voltage-gated channel open -> Ca2+ into presynaptic neuron
  3. ACh released from vesicles in presynaptic neuron
  4. ACh binds ligand-gated cholinergic receptor (nicotinic in skeletal muscle)
  5. Na+ into cell
    A. Minimal K+ out of cell
    B. Xs ACh broken down by AChesterase
  6. Depolarization of motor end plate
22
Q

Motor units

A

Nerve + fibers it innervates

  1. Only in skeletal muscles
  2. Precision depends on #fibers/neuron
23
Q

Spinal cord fxns

A
  1. Major reflex center and conduction pathway between body and brain
  2. Basic steps
    A. Receives sensory info
    B. Transmits info -> higher centers in brain or remains local (ascending tracts)
    C. Receives signal (descending tracts) from higher centers
    D. Transmits signal -> targets
  3. Several reflexes mediated by spinal cord
24
Q

Gray matter organization

A

Laminae I-X

25
Q

Laminae I

A 
1. Dorsal root fibers mediate
  A. Pain
  B. Temp
  C. Touch
2. Cells synapse posteromarginal nucleus
3. Cutaneous sensation
26
Q

Laminae II

A
  1. Substantia gelatinosa neurons (dec myelination)
  2. Modulate afferent fiber activity
    A. Pain
    B. Temp
  3. Cutaneous sensation
27
Q

Laminae III and IV

A 
1. Contain proper sensory nucleus
  A. Receives input from substantia gelatinosa
  B. Contributes to spinothalmic tracts
    1. Pain
    2. Temp
    3. Crude touch
2. Cutaneous sensation
28
Q

Laminae V

A
  1. Neck of dorsal horn
  2. Receive descending fibers from
    A. Corticospinal tracts
    B. Rubrospinal tracts
  3. Give rise to axons -> spinothalmic tract
  4. Proprioception- reg of movement
29
Q

Laminae VI

A
  1. Only in cervical and lumbar (limbs)
  2. Lateral segment receives descending
    A. Corticospinal
    B. Rubrospinal
  3. Medial segment receives afferent from
    A. Muscle spindles
    B. Joints
  4. Proprioception - reg of movements
30
Q

Lamina VII

A 
Intermediate zone
1. Nucleus dorsal is of Clarke
  A. C8-L2
  B. Receives muscle and tendon afferent
  C. Origin dorsal spinocerebellar tract
2. Intermediolateral cell column (IML)
  A. T1-L2
  B. Symp neurons
  C. Form lat horn
  D. Cell bodies symp preganglion neurons
3. Parasympathetic neurons
  A. S2-S4
  B. Sacral autonomic nucleus
  C. Preganglionic parasympathetic neurons
4. Renshaw cells (interneurons)
5. Allows dorsal and ventral horns to communicate
31
Q

Laminae VIII and IX

A
  1. Receive inputs from descending motor tracts
  2. Alpha and gamma motor neurons (VIII)
    A. Lower motor neurons
    B. Signal -> muscle
  3. Interneurons (IX)
  4. Neurons somatotopically arranged
    A. Post = flexor
    B. Ant = extensor
    C. Medial = axial and limb girdle
    D. Lateral = distal extremities
32
Q

Laminae X

A
  1. Surrounds central canal

2. Somatic and visceral afferent converge

33
Q

Motor neurons in ventral horn

A 
1. Alpha-motor neurons
  A. Large type A  alpha-motor n. Fibers
  B. Synapse on extrafusal fibers
2. Gamma-motor neurons (fusimotor)
  A. Small type A gamma-motor n. Fibers
  B. Synapse on intrafusal fibers (muscle spindles)
34
Q

Lateral inhibition

A

Alpha-motor neuron regulatory mech controlled by Renshaw cells
1. Renshaw cells - interneurons
A. Inhibitory (glycenergic) synapses on alpha-motor neurons
B. Can be supplied by multiple alpha motor neurons
C. Can synapse several alpha motor neurons
D. Sharpen intended signal
2. Basic steps
A. Alpha motor neuron excited
B. Activates Renshaw cells via excitatory (cholinergic) axon collaterals
C. Renshaw cells inhibit adjacent alpha motor neuron via GABA synapses

35
Q

Muscle spindles

A

In muscle belly
1. Senses length and velocity
2. Around intrafusal fibers
3. Sensory endings
A. Primary afferent fibers (Group Ia): innervate central part of spindle
1. Responds to slow change in length
2. Responds to rapid change in length
B. Secondary afferent fibers (Group II): innervate ends of nuclear chain fibers
1. Responds to slow change in length

36
Q

Golgi tendon organs

A

In tendons

  1. Monitor force/tensile load
  2. Resist imposed loads
  3. Fxn: red extensor activity inhibit injury
37
Q

Spinal reflexes

A

Modulated by supraspinal mech but reflex intact w/o it

  1. Ascending
  2. Interneuron
  3. Descending
38
Q

Stretch reflex

A
  1. Commonly tested
  2. Steps
    A. Muscle stretched (muscle spindle)
    B. Intrafusal fibers deform -> primary afferent fibers
    C. Primary synaptic w/ alpha motor neuron -> muscle contraction
    D. Primary can also synapse inhibitory interneuron -> lateral inhibition
  3. Dynamic
    A. Elicited by rapid length change transmitted by primary afferent
    B. Reflex opposes sudden change
    C. Over in fraction of a second
  4. Static (tonic)
    A. Prolonged after dynamic reflex
    B. Continuous signals from primary and secondary afferents
    C. Causes degree of contraction to remain constant
  5. Prevents oscillation/jerkiness of movements
  6. Hyperactive
    A. Damage descending pathways
    B. Inc neuronal excitability -> tremors/clonus
39
Q

Inverse stretch reflex

A
  1. Polysynaptic
  2. Dec contraction time inhibits overstretching
  3. Golgi tendon organs
  4. Steps
    A. Activate golgi tendon -> Ib afferents -> interneuron
    B. Interneuron inhibits alpha motor neuron that innervates same muscle
    C. Stops contracting/stretching
40
Q

Flexion (withdrawl) Reflex

A
  1. Mediated by nociceptors
    A. Free nerve endings - not in muscle
  2. Polysynaptic
  3. Steps
    A. Noxious stim -> free nerve endings -> spinal cord
    B. Fibers synapse 3-4 excitatory interneurons -> several alpha motor neurons
    C. Contraction isolate real flexors and relax ipsolateral extensors
  4. W/draw limb
  5. Often w/ crossed-extension reflex
41
Q

Crossed-extension reflex

A
  1. Nociceptors -> flexion reflex and crossed extension
  2. Steps
    A. Afferents -> interneurons -> axon collaterals thru anterior commissure
    B. Multisynaptic connections w/ alpha motor neurons that innervate contralateral flexors/extensors
    C. Alpha motor neuron -> contralateral flexor relax and extensor contract

MSK (13 decks)

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