Physiology

Question 1

What does PTH do to Ca and phosphate levels and how?

Answer 1

Increases serum Ca by:
- release from bone
- decreased excretion by kidney
- increase calcitriol to increase Ca absorption
Increases excretion of phosphate by kidney to stop crystals precipitating out, but increases phosphate out of bone into plasma.

Question 2

What does calcitonin do?

Answer 2

Decreases serum ca2+ by:

• Increasing Ca2+ dep into bones
• Inhibiting osteoclasts reabsorbing bone
• Decreasing kidney uptake of calcium

Question 3

What is the diff between osteoporosis and osteopenia?

Answer 3

Osteoporosis; decrease in bone density >2.5 SD from healthy 30 yr old woman. Lose cells and matrix, loss of trabeculae so load is greater
Osteopenia; decrease in bone density by 1-2.5 SD from healthy 30 yr old woman

Question 4

What is the definition of sarcopenia?

What is the criteria?

Answer 4

Age related loss of skeletal muscle mass and function

Low mass + strength or low physical performance

Question 5

Is the force of slow or fast muscles more affected with age?

What is a possible neural mechanism for this?

Answer 5

Fast
Type 2 motor units and denervated, stay that way or are reinnervated with type 1 motor unit so overall slowing of muscle
Overall a big drop in number of motor units and fibres at 50

Question 6

When and What does Duchenne muscular dystrophy present with?

What causes it? How is ca and inflamm involved?

Answer 6

around 2-6 it presents
progressive wasting of skeletal muscles (also cardiac); trunk and limbs esp of proximal lower limb. Have calf pseudo hypertrophy

Caused by mutation in the dystrophin gene which stabilises the actin cytoskeleton with the membrane during contraction (esp stretch) and act as a shock absorber (costameres). without it get muscle damage even at low stretch and struggles to repair leading to wasting.
Increase in intracellular calcium after damage thought to he related. Get excess inflamm and fibrosis replacing contractile material

Question 7

How does BMB differ from DMD?

What is the gold standard treatment for DMD

Answer 7

Same muscles effected but its later onset (around adolescence) and its less severe
DMD also has no almost no dystrophin where as in BMD there is lots of smaller, abnormal molecules

Use corticosteroids which help preserve existing fibres and delay weakness
Upregulating HSP72 on trial could also help

Question 8

How and in response to what is calcitriol stimulated? What does it do?

Answer 8

In response to low serum Ca2+, PTH stimulates its synthesis in the kidney to increase Ca2+ reabsorption from the GIT
It also facilitates renal reabsorption of Ca2+ and helps mobilise Ca2+ out of bone (with PTH)