work on

bio lec 10:

difference of effects of loading vs reduced mechanical


dangers of hyocalcemia:

• tetany; sustained respiratory-muscle contraction may cause asphyxiation. → this is because the nervous system becomes more hyperexctiable ( hyper → out of control)

What cells secrete PTH?

Principal (chief) cells.

p = prinicpal / low blood calcium (negative feedback)

Low Ca²⁺ → ↑ PTH → ↑ osteoclast resorption, kidney Ca²⁺ retention, calcitriol → normal Ca²⁺. ( calcitriol is an active hormonal form of vitamin d that increases blood calcium and phosphorus levels)

vs calcition (peptide!!! — thus cant cross the membrane)

high blood calcium

parafollicular — but follicular cells produce thyroxine( thyroid hormone)!!

What does calcitonin do in kidneys? → kidneys = urine. calcitonion increases calcium excretion ( becuase high blood calcium, we want it to go down, so excretion!!)

hypocalcemia → sodium channels open easily and remain open longer, Sodium enters nerve cells more freely.

• Excess sodium entry makes neurons hyperexcitable, leading to sustained contraction.

Why do neurons become hypoexcitable in hypercalcemia? — Higher excitation is needed to open voltage-gated sodium channels.

• Neurons become difficult to activate