HYPOTHALAMUS AND PITUITARY

Hypothalamus and PituitaryHypothalamus: Part of the brain, below the thalamusProduces neurohormones, which travel along length of neurons, then through blood to the pituitary

Pituitary:Located below brainControls other glandsTwo lobes (anterior and posterior)

THYROID HORMONES

Thyroid Gland

• Located in front of the throat

• Shaped like a bow tie, or butterfly

• Secretes thyroxine (T4) and triiodothyronine (T3)

Thyroid Hormones

Thyroxine (T4) Triiodothyronine (T3)

Where do you get your iodine?

Can you spot the difference?

TRH

TSH

T4

Thyroid hormone feedback loop1. TRH released by hypothalamus, stimules release

of TSH in pituitary2. TSH stimulates thyroid, inhibits release of TRH3. Thyroxine (T4) from thyroid inhibits release of TSH

What happens if you don’t get enough iodine?

TRH

TSH

T4

Iodine deficient goiter1. TRH released by hypothalamus, stimules release

of TSH in pituitary2. TSH stimulates thyroid, inhibits release of TRH3. Thyroxine (T4) from thyroid inhibits release of TSH

4. Lack of iodine prevents T4 formation, loss of negative feedback on TSH

5. TSH continues to stimulate thyroid

Iodine Deficient Goiter

Calcitonin

• Thyroid gland also produces calcitonin, which is involved in calcium balance

• Calcitonin is released in response to rising blood Ca2+ levels

PARATHYROID HORMONES

Parathyroid Glands

• 4 small glands on posterior side of thyroid gland

• Produce parathyroid hormone (PTH)

• Involved in calcium balance

• Released in response to low blood Ca2+ levels

PINEAL GLAND

Pineal Gland

• Regulates several biological rhythms

• Secretes melatonin• When eyes see light,

melatonin secretion is inhibited

LED Screens and Melatonin

• What affect do you think LED screens on phones and tablets have on melatonin levels in the brain?