Course Notes Essay

Anatomy & Physiology Notes: 1/25/13
Endocrine System:
- Several levels of regulation
- Local control: local groups of cells will be affected
- Neural control: nervous system, large change, precise target
- Hormonal control: longer term, less pin point, endocrine system.
Hormones may:
Stimulate the synthesis of new enzymes or other protein’s, by activating gene transcription
Increase or decrease rate of protein synthesis already taking place.
Alter function of an enzyme by turning it on/off
Endocrine glands: released hormones into bloodstream. 1/30/13
Structure
1) Amino acid derivative:
Structurally related to A.A.
Single a.a that are modified to be hormone. Ex. Epinephrine, norepinephrine, dopamine, thyroid hormones, melatonin.
2) Peptide hormones: short chain of A.A. ex. ADH, oxytocin, TSH, LH, FSH.
3) Lipid derivative:
Steroid hormone (ex. Testosterone, estrogens, etc.)
Eicosanoids (ex. Prostaglandin)
Cell Membrane receptors. Fig 16.2: Temporary and fast acting.
Non lipid derivative proteins bind to receptors at cell membrane.
This message is conveyed to a 2nd (G protein) messenger & is amplified,
Once message is sent something happens?
Fig 16.3 permanent, takes longer.
Lipid derivative hormones directly activate transcription in cell, & makes new protein.
3 types of gland stimuli:
1) Change in composition of extracellular fluid. Ex: decrease Calcium (Ca2+)
2) Arrival of another hormone
3) Arrival of neurotransmitter.
Most cases it’s based on a negative feedback loop.
Pituitary gland:
Lives below hypothalamus
In sella turcica
Releases a hormone
Hypophyseal portal system- a network of capillaries that brings blood from hypothalamus into anterior pituitary.
Hormones of anterior pituitary:
1) TSH- thyroid stimulating hormone called thyrotropin stimulates release of thyroid hormone.
Released in response to thyroid releasing hormone (TRH) from hypothalamus
2/1/13
Thyroid Gland:
Highly vascular
Follicle cells synthesis the thyroid hormones
TSH: stimulates the uptake of iodide into follicle cells & produce thyroid hormones
Steps in thyroid hormone synthesis:
1) Iodide ions in blood stream taken up into follicle cells.
2) Enzyme converts iodide (I-) into iodine (I+)
3) Iodine is attached to tyrosine
4) T3 & T4 (thyroid hormones) are formed
5) And released as necessary
Thyroid function:
Increase ATP production by binding to mitochondrial receptors
Changes gene transcription
All thyroid hormones can cross cell membrane
Calcitonin: brings down Ca2+ levels in blood by releasing Ca2+ into bone.
Stimulate Ca2+ excretion
Inhibit osteoclast activity
Parathyroid (PTH): increases Ca2+ blood levels by stimulating osteoclasts.
Increase Ca2+ absorption in kidney
Inhibits osteoblast
Adrenal Gland:
Sit atop kidneys
Highly vascular
2 parts: medulla & cortex
Cortex: 3 regions
Zona glamerulosa: produces aldosterone
Aldosterone: deals w/ Na+ & K+ levels to maintain fluid balance
Reabsorption of Na+ will also reabsorb water
Stimulated by Na+ levels decreased, decreased Blood volume/ Blood pressure
Zona fasciculata: produces glucocorticoids. “Long term stress”
Glucose synthesis: increase Bg levels
Suppresses immune system
Anti-inflammatory
Zona reticularis: produces small amounts of androgens- connected to sex drive
Adrenal Medulla: “short-term stress” fight or flight.
Releases epinephrine & norepinephrine. Mobilizes glycogen reserves
Accelerate fatty acids & releases to blood stream.
Increase H.R
Pineal Gland: synthesizes melatonin- sleep rhythms produced highest when dark, lowest during day.
Seasonal Affective Disorder (SAD ) increase levels of melatonin
Pancreas: some digestive functions (duties)
Alpha cells: glucagon
B cells: insulin- released
When blood glucose rises, binds to receptors on cell membrane & allows uptake of glucose.
Insulin allows glucose to be stored as glycogen in liver & skeletal muscles.
Stimulates triglyceride formation in adipose

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