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13 Cards in this Set
- Front
- Back
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Synergistic
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The effect of two hormones is greater than one alone.
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Permissive
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The presence of one hormone is necessary for another to have an effect.
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Antagonistic
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Two hormones oppose each others effects
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Steroids
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1. Small molecules synthesised primarily from cholesterol.
2. Act on intracellular receptors which then bind to DNA. 3. Circulate in bound form. Also -Released immediately following synthesis -Have slow long lasting effects. |
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Peptide (protein) hormones
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1.between 3 and 332 amino acids.
2.Synthesised as preprohormones and stored prior to release. 3. Act on cell surface receptors then via 2nd messenger systems. Also -Degraded within cells. |
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Amino Acid Hormones
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1. NA, adrenaline, dopamine
2. Thyroid hormone. 3. All formed from tyrosine Also -stored for instant release -different modes of action depending on AA hormone |
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Release and Activation Mechanisms
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1. Continuous - eg TH under control of TSH - Pulsatile/Circadian
2. Exocytosis on stimulus - eg insulin. 3. Post release modification -steroids - oestrogens from androgens -vit D -angiotensin system |
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Control Mechanisms
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1. Negative Feedback - either hormone itself or regulated metabolite.
2.Degradation or excretion of hormone - oestrogen. 3. Receptor down regulation - adrenergic receptors. Also - Modification of hormone decreases its activity (vit D) - Termination of intracellular effects (eg phosphates) |
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Hormones: Hypothalamo-pituitary-ovarian axis
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1. GnRH - Pulsatile, controlled by higher brain centres.
2. FSH/LH - Glycoproteins - pulsatile - anterior pituitary > ovaries/testis. 3. Oestrogen/Progesterone - oestrogen +ve or -ve feedback on FSH - Progesterone slows pulses, oestrogen decreases amplitude |
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Oestrogen
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1. Many sexual roles - preparation for pregnancy - breast development - endometrium priming.
2.Some systemic roles- calcification and vascular permeability 3. Three types of oestrogen - E2 most potent. |
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Progesterone
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1. Prepares uterus, maintains during pregnancy.
2. Stimulates growth of mammary glands 3. effects on brain (PMT) |
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Sterodiogenesis
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1. Theca Cells - Respond to LH- secrete testosterone and androstenedione.
2. Granulosa Cell - stimulated by FSH - secretes aromatase. 3. Aromatase - cleaves Testosterone to estradiol. |
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Ovarian Cycle
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1. Growing Follice produces E2 - -ve feedback on FSH, followed large E2 surge - +ve feedback.
2. LH surge 36 hours later - follice ruptures, rump forms corpus luteum. LH leves fall as no +ve E2 feedback. 3. CL produces progesterone. P blocks +ve feedback from E2. Cycle ends and E2 and P levels fall and FSH level rise. |
