lec 11 v1

What is the normal blood calcium range?

8.7–10.4 mg/dL.

What is hypocalcemia?

Blood calcium below 8.7 mg/dL; associated with nervous system hyperexcitability and tetany.

What is hypercalcemia?

Blood calcium above 10.4 mg/dL; associated with nervous system depression and possible cardiac arrest.

Why must blood calcium be carefully regulated?

Calcium is important in cardiac, nerve, enzyme, and blood physiology.

What is the body's major calcium reservoir?

Bone.

What are the three organs central to calcium homeostasis?

Bone, kidneys, and intestines.

What is the normal blood phosphorus range in the notes?

3.5–4.0 mg/dL.

Where is the thyroid gland located?

Just below the larynx, with right and left lobes connected by an isthmus.

What is the isthmus of the thyroid?

The tissue connecting its right and left lateral lobes.

What is unusual about the thyroid's hormone storage?

It stores large amounts of its products, about a 100-day supply.

What is one bone-related action of thyroxine?

Increases osteoblast activity.

What else do thyroid hormones such as thyroxine regulate?

The rate of metabolism.

Which thyroid cells make calcitonin?

Parafollicular cells, also called C or clear cells.

What condition stimulates calcitonin secretion?

High blood calcium.

What is calcitonin's overall effect on blood calcium?

Decreases blood calcium and phosphate levels.

How does calcitonin affect osteoclasts?

Inhibits their bone-resorbing activity.

How does calcitonin affect osteoblasts?

Increases their activity, increasing calcium uptake into bone matrix.

How does calcitonin affect the kidneys?

Increases calcium excretion in urine.

Why does increased osteoblast activity lower blood calcium?

More calcium is deposited into bone matrix rather than remaining in blood.

Is calcitonin essential for calcium homeostasis?

No; calcium can still be maintained without the thyroid if PTH levels are normal.

Where are the parathyroid glands located?

Embedded on the posterior surfaces of the thyroid's lateral lobes.

Which parathyroid cells secrete PTH?

Principal or chief cells.

What is another name for parathyroid hormone?

Parathormone.

What condition stimulates PTH secretion?

Low blood calcium, below 8.7 mg/dL.

What is the overall effect of PTH on blood calcium?

Increases blood calcium levels.

How does PTH affect osteoclasts?

Increases their number and activity, raising bone resorption.

How does PTH affect calcium handling by the kidneys?

increases the rate of removal of calcium from urine returning it to the blood

How does PTH affect calcitriol production?

Stimulates formation of calcitriol in the kidneys.

How does calcitriol affect the digestive tract?

Increases calcium absorption from the intestines into blood.

Why can PTH increase blood calcium in three ways?

It promotes bone resorption, renal calcium retention, and calcitriol production.

How do PTH and calcitonin compare?

PTH raises blood calcium; calcitonin lowers it.

What is the vitamin D sequence shown in the slides?

Skin → liver (calcidiol) → kidney (calcitriol, active form).

Which organ makes calcidiol in the vitamin D pathway?

The liver.

Which organ makes active calcitriol?

The kidney.

What is the active form of vitamin D called?

Calcitriol.

How does reduced PTH or calcitriol affect intestinal calcium absorption?

Intestinal calcium absorption decreases.

If calcium exceeds 10.4 mg/dL, what response is shown?

Calcitonin response: less osteoclast activity, more osteoblast activity, and more kidney calcium loss.

If calcium falls below 8.7 mg/dL, what response is shown?

PTH response: more bone resorption, kidney calcium retention, and calcitriol production.

What does negative feedback mean in calcium regulation?

A change in blood calcium triggers responses that return it toward normal.

During low-calcium negative feedback, what acts as a receptor?

Calcium-sensing cells of the parathyroid glands detect the decrease.

During low-calcium negative feedback, what is the hormone signal?

Increased synthesis and secretion of PTH.

During low-calcium negative feedback, which tissues are effectors?

Bone and kidneys; intestinal absorption also increases through calcitriol.

What ends the PTH-driven negative feedback response?

Blood calcium increases toward normal homeostasis.

What is osteitis fibrosa cystica associated with?

Hyperparathyroidism.

Why does hyperparathyroidism weaken bones?

Excess osteoclast activity increases bone resorption and demineralization.

What are the bone changes in osteitis fibrosa cystica?

Demineralized, weakened, deformed bones.

What does RMP stand for?

Resting membrane potential.

What resting membrane potential does the slide use as normal?

About −70 mV.

Why does hypocalcemia make sodium channels easier to open?

Less outside calcium binds negative surface charges, reducing the charge difference.

What happens to sodium channel opening in hypocalcemia?

Channels open more easily and stay open longer.

What happens to sodium entry in hypocalcemia?

Sodium enters cells more readily.

What happens to neuronal excitability in hypocalcemia?

It increases: neurons become hyperexcitable.

What RMP example is shown for hypocalcemia?

About −60 mV, compared with −70 mV normal.

What muscle effects can hypocalcemia cause?

Tremors, spasms, and sustained contractions (tetany).

Why is severe hypocalcemia dangerous for breathing?

Sustained contraction of respiratory muscles can prevent normal breathing.

Why does hypercalcemia make sodium channels harder to open?

More outside calcium binds surface negative charges, increasing the charge difference.

What happens to sodium entry in hypercalcemia?

Sodium entry becomes more difficult.

What happens to neuronal excitability in hypercalcemia?

It decreases: neurons become hypoexcitable.

What RMP example is shown for hypercalcemia?

About −80 mV, compared with −70 mV normal.

What life-threatening cardiac consequence is associated with severe hypercalcemia?

Cardiac arrest.

Hypocalcemia vs. hypercalcemia: which causes hyperexcitability?

Hypocalcemia.

Hypocalcemia vs. hypercalcemia: which causes hypoexcitability?

Hypercalcemia.

If voltage-gated sodium channels open too easily, which calcium disorder fits?

Hypocalcemia.

If a higher voltage is needed to open sodium channels, which calcium disorder fits?

Hypercalcemia.

What are the four main stages of fracture repair?

Fracture hematoma/procallus → soft callus → hard callus → remodeling.

What forms first at the site of a fracture?

A blood clot called a fracture hematoma.

What happens to some bone cells near the initial fracture?

They die at the fracture site.

What is a procallus?

Granulation tissue formed as the fracture hematoma is organized.

What is granulation tissue in the fracture repair notes?

Actively growing connective tissue.

What is a callus?

A mass of repair tissue bridging broken ends of a bone.

What cell types help form the soft callus?

Fibroblasts and osteogenic cells.

What tissue makes up the soft callus?

Fibrocartilage.

How does a soft callus become a hard callus?

Osteoblasts convert it into spongy bone.

What type of bone is in the hard callus?

Spongy bone.

What happens during the final stage of fracture healing?

The callus is remodeled toward the bone's nearly original form.

Why is fracture remodeling necessary?

It restores the repaired area's structure toward its original form.

What is surgical bone grafting?

Putting bone tissue or fragments into a fracture to provide a model for repair.

Where can bone graft material come from according to the notes?

Another body site or a cadaver; living or dead bone fragments are described.

What do pulsating electromagnetic fields aim to stimulate?

Osteoblast activity and bone material production.

how does pulsating electromagnetic fields attract osteoblasts?

Stressed mineral crystals generate small electrical fields.

Which groups are mentioned for electromagnetic fracture treatment?

Athletes and elderly patients.

What kind of fields does the treatment use?

Pulsating low-frequency electromagnetic fields.

How are fields delivered in the described treatment?

Through coils in a computer-controlled therapy mattress.

What reported success rate appears in the notes for electromagnetic therapy?

More than 80% (a claim from the lecture notes).

How are fractures organized in the notes?

By site, nature of the break, and appearance.

What is a closed or simple fracture?

The broken bone does not protrude through the skin.

What is an open or compound fracture?

The bone breaks through the skin and contacts the environment.

Why are open fractures particularly dangerous?

Their contact with the environment increases infection risk, including osteomyelitis.

What is a comminuted fracture?

A bone broken into more than one fragment.

What is a greenstick fracture?

One side of the bone breaks while the other bends.

Why are greenstick fractures especially associated with children?

Children's bones are pliable and may bend rather than break completely.

What is a spiral fracture?

A fracture resulting from twisting or torque through bone.

What is a transverse fracture?

A break across the long axis of a bone shaft.

What is a stress fracture?

A fracture associated with repeated overuse or stress on bone.

Why may early stress fractures heal well?

They may remain nondisplaced with good anatomic alignment.

What is a displaced fracture?

Fragments have changed alignment relative to each other.

What does fracture displacement specifically refer to?

The change in anatomic axis of one fragment relative to another.

How can displacement be measured in the notes?

By shaft width or percentage, such as 50% or 100%.

What is a nondisplaced fracture?

Bone fragments retain normal alignment.

What is a Pott's fracture?

A distal fibular fracture with serious injury to the distal tibial articulation.