Ch 7: Intro to the Endocrine Sytem Flashcards
Hormone
Chemical messenger released in response to a stimulus & secreted into the blood to be carried to its target cell
Major class of hormones
- Amines
- Peptides
- Steroids
Amines
Derivatives of tyrosine
- Thyroid hormones
- Catecholamines
Thyroid hormones
- Triiodothyronine (T3)
- Thyroxine [Tetraiodothyronine] (T4)
Catecholamines
- Epi
- NorEpi
- Dopamine
Peptides
AA chains/small peptides
ex: insulin, glucagon
Steroids
Derivatives of cholesterol
- Adrenal hormones
- Gonadal hormones
Adrenal hormones
- Mineralocorticoids
- Glucocorticoids
(corticoid steroids that come from adrenal cortex)
Mineralocorticoids
Affect mineral metabolism
- Aldosterone
Glucocorticoids
Affect glucose metabolism
- Cortisol
Gonadal hormones
- Testosterone
- Estradiol
- Progesterone
(testes/ovaries)
Cholesterol is what for our body?
Important and needed for our body
Steroids are lipids that need?
Smooth ER
Proteins are generally water what?
Water soluble
Medulla
Something inside something
Cortex
Outside layer of things
Minerals
Ions (Ca, K, etc.)
Hormonal transport: Peptide & Catecholamines
Water soluble
- transported easily in blood
- easily degraded by enzymes (short half-life)
Hormonal transport: Thyroid & Steroids
Lipid soluble
- small amnts free in plasma, mostly carried by transport proteins
- not readily degraded by enzymes (long half-life)
Hormonal action: Peptide & Catecholamines
Must act on extracellular receptor, activating a second messenger system
Hormonal action: Thyroid & Steroids
- diffuse directly thru membrane
- (usually) alters transcription of DNA
Control of Hormone Secretion
- Change in plasma ion concentration
- Change in plasma nutrient concentration
- Neural input
- (Neuro) Hormonal input
Change in plasma ion concentration example
Aldosterone secreted by adrenal cortex stimulates increased Na+ absoprtion
Change in plasma nutrient concentration example
Glucagon secreted by alpha-cells of Langerhans raises blood glucose
Neural input example
Neural input secretion from gland
Sympathetic stimulation on adrenal medulla initiates Epi release
(Neuro) Hormonal input example(s)
*(neuro) hormone stimulates the secretion of another hormone
ex: TSH controls secretion of T3 & T4
ex: CRH released from hypothalamus act on anterior pituitary gland to release ACTH
Tropic hormones
A hormone that stimulates the secretion of another hormone
Tropic hormone example
- Gonadotropic releasing hormone
- Adrenocorticotropic hormone
Major Hypophysiotropic Hormones
- Gonadotropin Releasing Hormone* (GnRH)
- Thyrotropin Releasing Hormone* (TRH)
- Corticotropin Releasing Hormone* (CRH)
- Somatostatin (SS)
- Growth Hormone Releasing Hormone* (GHRH)
- Dopamine (DA)
Dopamine (DA)
Prolactin-release Inhibiting Hormone (PIH)
Major Hormones of the Anterior Pituitary
- Follicle – stimulating hormone (FSH)
- Luteinizing Hormone (LH)
- Thyroid Stimulating (TSH)
- Adrenocorticotropic Hormone (ACTH)
- Growth Hormone (GH)
- Prolactin
Endocrine Disorders
- Hypersecretion
- Hyposecretion
- Hyporesponsivness
- Hyperresponsiveness
Hypersecretion
Too much hormone secreted for the prevailing conditions
ex: Grave’s disease, Cushing’s syndrome
- primary hypersecretion
- secondary hypersecretion
Primary hypersecretion
Secreting organ produces too much hormone (too much gland #3, downstream effect)
Secondary hypersecretion
Tropic hormones are produced at too high level
Hyposecretion
Too little hormone secreted for the prevailing conditions
ex: Hypothyroidism, Addison’s disease. Type I diabetes mellitus
- primary hyposecretion
- secondary hyposecretion
Primary hyposecretion
Secreting organ fails
ex: Thyroid can’t secrete T3/T4
Secondary hyposecretion
Tropic hormones are too low
ex: ???
Hyperresponsiveness
Glands over respond to appropriate levels of hormone
- thyroid increases synthesis of epinephrine receptors
Anterior pituitary
Adenohypophysis
- a true endocrine gland of epithelial origin
- closer to nose
Posterior pituitary
Neurohypophysis
- an extension of the neural tissue
- closer to spinal
- an extension of the brain that secretes neurohormones made in the hypothalamus
Adrenal and pituitary gland made up of?
Glandular (outside) and neural tissue (inside)
Adrenal medulla releases
Catecholamines (Epi + NorEpi)
Adrenal cortex releases
Glucocorticoids, testosterone, and aldosterone
Adrenal gland
- sits on top of kidney
- unique structure
Calcium regulation
*high outside cell, low inside cell
1. Low plasma of Ca2+
2. Parathyroid gland
3. Parathyroid hormone
4. Into blood and targets bone and kidney
5. Increase bone resorption, kidney resorption, and production of calcitriol indirectly leads to increased intestinal absorption of Ca2+
6. Negative feedback loop if successful
- parathyroid hormone will degrade naturally by it’s half life
Infundibulum
The stalk that connects the pituitary gland & hypothalamus (brain)
- axon potentials (neural hormones) leave hypothalamus thru infundibulum into posterior pituitary
Posterior pituitary pathway
- Neurohormone is made and packaged in cell body of neuron
- Vesicles are transported down the cell
- Vesicles containing neurohormone are stored in posterior pituitary
- Neurohormones are released into blood
The Hypothalamic-Hypophyseal Portal System consists of
- Neurons
- Portal vessels
- Endocrine cells
- Pituitary gland
- Hypothalamus
- 2 Capillary beds (unique!!!!!)
Vasopressin
Constricts blood vessel…increases blood pressure
- ADH (anti-diarrhetic)
- affects kidney tubules
Oxytocin
- Not well understood in males, but involved in feelings (love)
- In women, affects mammary gland and smooth muscle of uterus wall
— causes line of uterus to become inflamed to get ready for implantation & causes breast to increase lipids it stores (enlargement) triggering milk glands to constrict & release milk when a baby sucks on the nipple
Anti-diarrhetic
decreases urination…build up of water in body
The Hypothalamic-Hypophyseal Portal System
- Cell bodies of secretory neurons in hypothalamus synthesize ADH or oxytocin
- These hormones move down axons of the secretory neurons & accumulate in axon endings
- Action potentials trigger the release of these hormones, which enter blood capillaries in the posterior lobe of the pituitary
- Small blood vessels deliver the hormones to the general circulation
Osmoreceptors in hypothalamus trigger release of?
ADH (vasopressin)
- Pituitary gland releases ADH and increases permeability
Oxytocin pathway
- Suckling stimulates nerve endings in nipple and areola of breasts
- Neural pathways carry stimuli to hypothalamus
- Hypothalamus produces oxytocin that is released by posterior pituitary
- Oxytocin causes mammary lobules to contract
- Milk letdown occurs (after birth)
Tropic Hormone Pathway
- Stimulus
- Hypothalamus (aways will be gland #1)
- Tropic hormone #1
- Anterior pituitary gland (always will be gland #2)
- Tropic hormone #2 (SHORT-LOOP NEG FEEDBACK)
- Endocrine gland (can vary: gonads, thyroid, adrenal cortex)
- Hormone #3 (LONG-LOOP NEG FEEDBACK)
- Target tissue
- Response (another NEG FEEDBACK)
*3 Neg feedbacks in total
Neurons
Synthesizing tropic hormones release them into capillaries of the portal system
Endocrine cells
Release their hormones into the second set of capillaries for distribution to the rest of the body
Portal vessels
Carry the tropic hormones directly to the anterior pituitary
Portal System
- Neurons synthesizing tropic neurohormones release them into capillaries of the portal system
- Portal veins carry the tropic neurohormones directly to the anterior pituitary, where they act on the endocrine cells
- Endocrine cells release their peptide hormones into the second set of capillaries for distribution to the rest of the body
*Neurohormones from the hypothalamus control release oof the anterior pituitary hormones
Control of Testicular Function: Gonadotropin Releasing Hormone Pathway (GnRH)
- Hypothalamus
- GnRH
- Anterior pituitary (FHS & LH secreting cells)
- FSH & LH
- Ovaries/testes (spermatogenesis/oogenesis)
- Testosterone/estrogen
*initial stimulus
Regulation of Thyroid Hormone Secretion: Thyrotropin Releasing Hormone (TRH)
- Initial stimulus (Stress, cold in infants)
- Hypothalamus
- TRH
- Anterior pituitary
- Thyroid-stimulating hormone (TSH)
- Thyroid gland
- Thyroid hormone (T3 & T4)
*Increase in metabolic rate and heat production, enhancement of growth and CNS development, enhancement of sympathetic activity
If one takes steroids at high amounts…
Reduced fertility and sperm motility
ex: androgen is an “umbrella” of testosterone
Follicle
In ovaries, an egg that protrudes out of ovaries w/ granulosa cells
Corticotropin Releasing Hormone (CRH)
- Stimulus (blood level of glucose falls too low, body is stressed
- Hypothalamus
- CRH
- Anterior pituitary
- Adrenocorticotropic hormone (ACTH)
- Adrenal cortex
- Cortisol
*Cortisol is a glucocorticoid steroid
*Glucose, AAs, fatty acids available to help resist stress…blood glucose level rises; absence of stimulus leads to inhibition of cortisol secretion