Class notes
BIO 226 Endocrine System Notes
- Course
- BIO 226
- Institution
- Marian University
This is a comprehensive and detailed note on the endocrine System for Bio 226. *An Essential Study Material!!
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THE ENDOCRINE SYSTEM1. Introduction: Endocrine Glands are ductless glands that secrete hormones into the blood; controlled by
the nervous system !
2. GLANDS!
1. PITUITARY=Hypophysis: hangs from the hypothalamus of the Diencephalon!
1. Controlled by the hypothalamus - sends tropic hormones to the pituitary !
2. Pituitary will not release its hormones unless the hypothalamus send signal !
3. 2 lobes: !
1. Anterior- endocrine cells in it !
2. Posterior!
2. ANTERIOR PITUITARY
A. GROWTH HORMONE (GH) Regulates mitosis and growth of body cells, almost ALL cells have
receptors for GH !
B. THYROID STIMULATING HORMONE (TSH) controls thyroid activity !
C. ADRENOCORTICOTROPIC HORMONE (ACTH) controls the activity of the adrenal cortex !
D. FOLLICLE-STIMULATING HORMONE (FSH) stimulates oogenesis and spermatogenesis !
E. LUTEINIZING HORMONE (LH) stimulates release of male and female sex hormones!
F. PROLATCIN (PRL) milk production !
G. MELANOCYTE STIMULATING HORMONE (MSH) stimulates production of melanin {not shown} !
3.POSTERIOR
PITUITARY= neurohypophysis !
A. Looks like nervous tissues, neural glial cells and parts of neurons !
B. In hypothalamus: neurosecretory cells: supraoptic nucleus (oxytocin) & paraventricular nucleus
(cells secrete ADH) from hypothalamus extend downward !
1. Axon terminals are enlarged in posterior pituitary, neurons make a chemical and store it in the
ends of the axons - released into the surrounding blood vessels!
1. This neurotransmitter is released into the bloodstream !
2. No cells in the posterior pituitary MAKE hormones, comes from neurons !
, 2. OXYTOCIN: causes uterine contractions during labor and milk release during suckling !
3. ANTIDIURETIC HORMONE (ADH) retains water in our blood, decreased urine output!
2. THYROID: bilobed structure around the trachea beneath the larynx, very vascular - releases its
hormones after receiving TSH from pituitary !
A. THYROID HORMONE (TH) it increases cellular activity in skeletal, reproductive and nervous
systems, circulates in whole body !
A. Low TH, reproductive system slows or unsynchronized, nervous system slows down !
B. CALCITONIN - is released in response to increased blood calcium levels. Decreases blood
calcium levels by inhibiting the removal of calcium from the bone, which increases the deposit of
calcium into the bone!
3. PARATHYROID: 4 masses on the back of the thyroid, release their parathyroid hormone (PTH) in
response to low blood calcium. Increases blood calcium levels by stimulating the removal of calcium
from the bone - osteoclast activity increases !
4. PANCREAS: (digestive gland) hormones secreted from the Islets of Langerhans
1. Yellow cells on the outer ring: acinar cells - make
digestive enzymes, released into the duodenum !
2. Islets of Langerhans: mass of green cells in the
center, has capillaries - hormones released into the
capillaries/blood supply !
1. Beta Cells: INSULIN, secreted in response to
high levels of glucose. Insulin decreases blood
sugar by stimulating the uptake of glucose by
the body cells !
2. Alpha Cells: GLUGAGON, secreted in respons
to low levels of glucose. Increases blood sugar
by stimulating the release of glucose from body
cells back into the blood stream !
5. ADRENAL GLANDS: atop the kidneys, 2 areas:!
1. CORTEX: secretes steroids - corticosteroids (fat-based) in response to ACTH, 3 types !
1. Zona Glomerulosa - creates MINERALCORTICOIDS: regulate sodium an potassium levels !
2. Zona Fasciulata- GLUCOCORTICODS - increases breakdown of fatas & proteins to generate
blood glucose !
3. Zona Reticulata - GONADOCORTICOIDS - sex hormones (estrogen, progesterone,
testosterone) may aûect the onset of puberty, pubic and axillary hair development, and sex
drive - released in vary small amounts !
2. MEDULLA - secretes EPINEPHRINE AND NOREPINEPHRINE - prepare body for Þght or ßight !
6. GONADS: !
1. Testes: testosterone!
2. Ovaries: estrogen and progesterone !
7. THYMUS: bilobed, at tracheal bifurcation. Secretes THYMOSIN, which causes the T-cells of the
immune system to mature !
1. T-cells made in red bone marrow, but are immature!
1. Circulate through bloodstream to reach thymus!
2. Exposed to thymosin, cells mature and can now function )
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