BIOL10002 Lecture Notes - Ductus Arteriosus, Heart Valve, Systolic Geometry
Week 5
Lecture 13
The Endocrine System and Hormones, part 2
The posterior pituitary
- releases neurohormones
1. Hypothalamic neurons produce ADH and Oxytocin and transport them to the posterior pituitary
2. Neurohormones released into posterior pituitary travel into capillaries
Note: The Anterior and Posterior pituitary have different capillary networks
The anterior pituitary
- no nerve terminals
- regulated by the hypothalamus
- anterior pituitary hormones are not neurohormones as they are secreted by a cell
1. The terminals of hypothalamic neurons release neurohormones (known as releasing factors) into the
hypothalamic capillaries
2. Neurohormones travel to anterior pituitary capillaries, are released into the anterior
pituitary, then stimulate or inhibit release of hormones from anterior pituitary cells
3. Anterior pituitary hormones released by anterior pituitary cells make their way into the
bloodstream
Hyperthyroidism – Grave’s
disease
Hypothyroidism – Hashimoto’s disease
Cause An antibody binds to the TSH
receptor, which mimics binding
of TSH to the TSH receptor on
the thyroid gland. Leads to high
levels Thyroxine and low levels
TSH.
Low iodine - no Negative feedback of
TSH as follicle cells fail to make
thyroxine, so Thyroid gland continues
to make Thyroglobulin but poorly
iodinated. Leads to low thyroxine and
high TSH.
Problem very high levels of thyroxine very low levels of thyroxine
Symptom
s
Weakness, lethargy, weight
loss, blurry eyesight, moist skin,
insomnia, palpitations, bulging
eyes, nervousness.
Weakness, lethargy, weight gain, blurry
eyesight, dry skin, irritability, memory
loss.
Treatmen
t
Inhibit the enzyme
thyroperoxidase preventing
iodination of Thyroglobulin.
Levothyroxine: daily, pure synthetic
form of T4
Thyroxine and the thyroid gland
- regulates the metabolic rate of most cells by activating enzyme transcription
- Thyroxine is crucial for normal development and growth
1. A follicle cell takes up iodine from blood
2. Cell synthesizes thyroglobulin from tyrosine
3. Thyroglobulin and iodine are secreted into the follicle lumen, then Thyroglobulin is iodinated
4. Iodinated Thyroglobulin Is taken up by follicle cell by endocytosis
5. Enzymes digest Thyroglobulin into T3 (active hormone) and T4 (precursor)
6. T3 & T4 secreted into blood
Goiter = uncontrolled cell proliferation
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Document Summary
Releases neurohormones: hypothalamic neurons produce adh and oxytocin and transport them to the posterior pituitary, neurohormones released into posterior pituitary travel into capillaries. Note: the anterior and posterior pituitary have different capillary networks. An antibody binds to the tsh receptor, which mimics binding of tsh to the tsh receptor on the thyroid gland. Leads to high levels thyroxine and low levels. Tsh as follicle cells fail to make thyroxine, so thyroid gland continues to make thyroglobulin but poorly iodinated. Leads to low thyroxine and high tsh. very low levels of thyroxine. Weakness, lethargy, weight loss, blurry eyesight, moist skin, insomnia, palpitations, bulging eyes, nervousness. Inhibit the enzyme thyroperoxidase preventing iodination of thyroglobulin. Weakness, lethargy, weight gain, blurry eyesight, dry skin, irritability, memory loss. Regulates the metabolic rate of most cells by activating enzyme transcription. O2 and nutrients must be transported around the body to tissues and organs. Blood pumped over gills to become oxygenated but leaves under very low pressure.
