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Define a hormone.
Chemical messengers released into the blood having an effect on “target” cell, tissue, or organ outside the tissue that made it.
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Why are "receptors" of utmost importance?
They bind with the particular hormone that the target is for.
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Name and describe 2 categories of hormones. Give a brief explanation on how they exert their influence on the target tissue. (mechanism of action, receptors (on the surface or inside the cell), make a NEW protein or modify an existing one, etc)
- nonpolar/lipophilic:
- ex. Steroids, thyroid hormone
- poor water solubility
- travel on protein in blood
- Polar/hydrophilic
- ex. LH, FSH
- dissolves in plasma
- can't pass through the membrane
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Antagonism
occurs when one hormone causes the loss of another hormone's receptors, reducing the effectiveness of the second hormone.
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Permissiveness
One hormone must be present in adequate ammounts for the full exertion of another hormone's effect. Ex. Thyroid hormone increases the number of receptors for epinephrine in epinephrine's target cells.
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Synergism
when actions of several hormones are complementary and their combined effect is greater than the sum of their separate effects. Ex. FSH and Testosterone
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What is "up regulation" and "down regulation"?
When target cells increase (up) or decrease (down) their number of particular hormone receptors.
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Hypthalamus releases ____ which hits the target cell __________ and controls the release of hormones _____ and ____
GnRH, Anterior pituitary, FSH, LH
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What is the major function for FSH in females and males.
- male - stimulates sperm production
- female - promotes follicular growht and development; stimulates estrogen secretion
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What is the target cell for FSH in females and males.
- Female - ovarian follicles
- Male - seminiferous tubules in testes
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What is the target cell for LH in females and males.
- Female - ovarian follicle and the Corpus Luteum
- Male - interstitial cells of Leydig in testes
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What is the major function for LH in females and males.
- female - stimulates ovulation, corpus luteum development, and estrogen and progesterone secretion
- male - stimulates testosterone secretion
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What is a tropic hormone? Give an example.
hormones that regulate secretion of other hormones. High concentrations cause target organs to hypertrophy, low levels cause targets to atrophy.
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Describe the relationship between the hypothalamus and the pituitary.
The hypothalamus is part of the brain and secretes several hormones, most of which affect the pituitary gland (which is a pea-sized gland that is connected to the hypothalamus by a thin strand of tissue called infundibulum.
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The posterior lobe of the pituitary does not produce its own hormones; however, it does release hormones. Explain what hormones it releases and what gland produces those hormones.
- posterior pituitary stores and releases hormones produced in the hypothalamus:
- ADH or vasopressin
- Oxytocin
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The anterior lobe of the pituitary produces and secretes its own hormones but is regulated by hormones secreted by the hypothalamus. Explain.
Hypothalamus releases tropic hormone that affects release of another tropic hormone from the anterior pituitary. That hormone effects release of a 3rd hormone from another endocrine gland and this 3rd hormone gets to a target cell
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Name the hormones secreted by the anterior pituitary.
- PRH - prolactin releasing hormone
- PIH - prolactin inhibiting hormone
- TRH - Thryotorpin releasing hormone
- CRH - Cortiocotropin releasing hormone
- GHRH - Growth Hormone Releasing hormone
- GHIH - growth hormone inhibiting hormone (somatostatin)
- Summary: TSH, ACTH, Growth Hormone, LH, FSH, Prolactin
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What does the pineal gland secrete?
converts seratonin to melatonin
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What does the thyroid gland secrete?
Secretes T4 and T3 (thyroid hormones)
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What do the parathyroid glands secrete?
located on posterior surface of thyroid. Secretes parathyroid hormone (PTH)
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What does the thymus secrete?
has a role in T Cell development and immune response.
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What do the adrenal glands secrete?
adrenocorticoids including aldosterone, cortisol, and androgens (sex hormones)
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What do the alpha cells of the pancreas secrete?
Glucagon (catabolic)
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What do the beta cells of the pancreas secrete?
Insulin (anabolic)
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Type I diabetes
- Insulin-dependant
- lack of insulin and excessive glucagon
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Type II diabetes
non-insulin dependant - target cells lack receptors for insulin. Aggravated by obesity and inactivity - can be managed through weight-loss and exercise and drug therapy
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acromegaly
caused by excessive GH in adults. No increase in height but soft tissue still grows causing elongation of jaw and deformities in extremeties
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gigantism
produced by excess GH secretion in children
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dwarfism
caused by inadequate secretion of GH during childhood
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goiter
Low T4 and T3 don't provide negative feedback which results in increased levels of TSH so the thyroid gland grows resulting in a goiter. Also produced by Grave's Disease (where antibodies act like TSH causing hyperthyroidism)
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hypothyroidism
- people with inadequate T4 and T3 levels
- low BMR, weight gain, lethargy, cold intolerance
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hyperthyroidism
Weight loss, heat intolerance, irritability, high BMR
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addison's disease
it's an adrenal disorder. hypoglycemia, electrolyte imbalances, loss of stress resistance, darkening skin
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Name some secondary endocrine glands.
- secondary glands - organs that serve other functions but also serve as endocrine glands
- heart
- liver
- adipose tissue
- kidneys
- skin
- stomach
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Define Gonad. What is it's primary sex organ?
- Gonad - primary sex organ that produces gametes and sex hormones
- Female gonads are ovaries
- Male gonads are testes
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Define Gamete. What is it's primary sex organ?
- Gametes are reproductive cells.
- Gametes have 1/2 the usual number of DNA molecules (chromosomes) - a copy of half of his or her genetic material
- Female Gamete - ovum
- Male Gamete - sperm
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Discuss the role of GnRH in the male reproductive system? What is its function and its target and what gland releases it?
Hypothalamus matures during puberty and starts producing GnRH—gonadotropin-releasing hormone which stimulates anterior pituitary to secrete gonadotropins (LH and FSH)
- Puberty is initiated by increase in GnRH activity.
- GnRH à travels to anterior lobe of pituitary à stimulates luteinizing hormone (LH) and follicle stimulating hormone (FSH)
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Discuss the role of FSH in the male reproductive system? What is its function and its target and what gland releases it?
FSH --> acts on Sertoli cells of testes to promote spermatogenesis (production of sperm cells) (FSH makes cells receptive to testosterone’s stimulatory effects)
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Discuss the role of LH in the male reproductive system? What is its function and its target and what gland releases it?
LH -->stimulates the Leydid cells (intestitial cells) of the testes to secrete androgens (sex steroid hormones) mainly testosterone.
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Discuss the role of Testosterone in the male reproductive system? What is its function and its target and what gland releases it?
- Testosterone is essential for:
- Spermatogenesis
- Development and growth of reproductive organs during puberty
- Responsible for secondary sex characteristics:
- facial hair
- vocal chords
- Stimulates manufacture of new protein filaments in muscles
- promotes bone growht at puberty
- Testosterone limits its own secretion by acting on the hypothalamus to suppress GnRH and acts on the anterior pituitary directly to inhibit gonadotropin release
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Discuss the role of Inhibin in the male reproductive system? What is its function and its target and what gland releases it?
- Inhibin - a hormone secreted by the Sertoli cells that inhibits FSH secretion by the anterior pituitary
- proportional to sperm count
- When sperm count falls below 20million/ml, inhibin secretion declines steeply
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Know the details of the uterine and ovarian cycle including how hormone levels change during the cycle and how those changes affect the ovarian/uterine physiology.
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Discuss the role of GnRH in the female reproductive system? What is its function and its target and what gland releases it?
it stimulates the release of FSH and LH. It's target is the anterior pituitary and it is secreted from the hypothalamus.
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Discuss the role of FSH in the female reproductive system? What is its function and its target and what gland releases it?
- function - to promote follicular growth and development and stimulate estrogen secretion.
- target - ovarian follicles
- released by - anterior pituitary
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Discuss the role of LH in the female reproductive system? What is its function and its target and what gland releases it?
- Function: stimulate ovulation, corpus luteum development, and estrogen and progesterone secretions
- Target: Ovarian follicle and corpus luteum
- Gland - Anterior Pituitary
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Discuss the role of estrogen in the female reproductive system? What is its function and its target and what gland releases it?
- secreted by mature follicles
- maintain female sex characteristics and causes endometrium to thicken
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Discuss the role of progesterone in the female reproductive system? What is its function and its target and what gland releases it?
- secreted by corpus luteum
- promotes endometrial vascularization and glandularization (glands secrete nourishment until placenta is established)
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Be able to describe the follicular phase, ovulation phase, and the luteal phase of the ovarian cycle and the accompanying phases of the uterine cycle. (what is happening in the ovary and what is happening to the endometrium?)
- follicular phase begins with day one of menstruation phases
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Discuss changes that occur during pregnancy and also if pregnancy does not occur.
No pregnancy - the ovum is released unfertilized and does not implant. degenerating corpus luteum causes decrease in estrogen and progesterone --> loss of endometrial support --> rise in LH/FSH secretion --> menstruation
- Pregnancy
- corpus luteum remains active for 3 months until placenta takes over its hormone-producing duties
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Describe the role of the placenta. What hormones does it secrete?
- Placenta performs functions of digestive system, respiratory system, and kidneys
- secretes:
- hCG (Human Chorionic Gonadotropin)
- Estrogen
- Progesterone
- lactogen
- relaxin
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Be familiar with any age-related changes that occur in the reproductive systems.
- menopause between 46 and 54
- less estrogen and progesterone secreted causing:
- Hot flashes
- Thinning of skin
- Cholesterol levels rise
- changes in hormonal profile (mood)
- loss of bone mass
- HRT - hormone replacement therapy
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What is the pathway of a hormone?
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Why can you take some hormones orally, like birth control pills, but you cannot take some like insulin in pill form?
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