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Anatomy & Physiology 208 > Endocrine System Part II > Flashcards

Endocrine System Part II Flashcards

1
Q

the hypothalamus is connected to the pituitary gland (hypophysis) via the

A

infundibulum

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2
Q

pituitary gland

A
  • secretes at least 8 major hormones
  • has 2 major lobes
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3
Q

posterior pituitary lobe

A

composed of neural tissue that secretes neurohormones
- neurohypophysis: posterior lobe of the pituitary + infundibulum

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4
Q

anterior pituitary

A

composed of glandular tissue; called the adenohypophysis

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5
Q

the anterior lobe is vascularly connected to the hypothalamus via the

A

hypophyseal portal system

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6
Q

hypophyseal portal system

A
  • primary capillary plexus
  • hypophyseal portal veins
  • secondary capillary plexus
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7
Q

the hypothalamus regulates hormone secretion by

A

secreting, releasing, and inhibiting hormones to the anterior pituitary gland

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8
Q

the posterior pituitary gland is made of

A

neural tissue - derived from a downgrowth of the brain

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9
Q

hypothalamic hypophyseal tract

A
  • maintains neural connection to the hypothalamus
  • tract arises from neurons in the paraventricular and supraoptic nuclei and runs through infundibulum
  • secretes 2 neurohormones (oxytocin + ADH)
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10
Q

paraventricular neurons in the posterior pituitary

A

produce oxytocin

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11
Q

supraoptic neurons in the posterior pituitary

A

produce ADH

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12
Q

hormones are stored in _________ and released into the blood when _________

A
  • axon terminals
  • neurons fire
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13
Q

Oxytocin

A
  • released during childbirth; stimulant of uterine contractions
  • hormonal trigger for milk ejection
  • ^ both are positive feedback loops
  • acts as neurotransmitter in brain
  • uses pip2 calcium 2nd messenger system
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14
Q

Anti diuretic hormone (ADH)

A
  • hypothalamus contains osmoreceptors that monitor solute concentrations
  • when concentration is high, posterior pituitary secretes ADH
  • target is kidney tubules - triggered to reabsorb more water and inhibit urine formation
  • release of ADH is also triggered by pain, low blood pressure, and drugs; inhibited by alcohol and diuretics
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15
Q

anterior pituitary hormones

A
  • all 6 hormones of the AP are peptide hormones
  • all but growth hormone (GH) activate target cells via cAMP second-messenger system
  • all but 2 are tropic hormones (tropins) - they regulate the secretion of other hormones
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16
Q

6 hormones of the anterior pituitary

A
  • growth hormone - GH
  • thyroid-stimulating hormone - TSH
  • adrenocorticotropic hormone - ACTH
  • follicle-stimulating hormone - FSH
  • luteinizing hormone - LH
  • prolactin - PRL
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17
Q

growth hormone

A
  • also called somatotropin
  • produced by somatotrophic cells
  • has direct actions on metabolism and indirect growth-promoting actions
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18
Q

direction actions on metabolism

A
  • decreases rate of cellular glucose uptake and metabolism (glucose sparing, anti insulin effects)
  • triggers the liver to break glycogen down into glucose
  • increases blood levels of fatty acids to use as fuel; encourages cellular protein synthesis
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19
Q

indirect actions on growth

A
  • triggers liver, skeletal muscle, and bone to produce insulin-like growth factors (IGFs)
  • IGFs stimulate the cellular uptake of nutrients used to synthesize DNA and the proteins needed for cell division and formation of collagen and deposition of bone matrix
  • GH stimulates most cells to enlarge and divide, but its major targets are bone and skeletal muscle
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20
Q

regulation of secretion of gh

A

release or inhibition of gh is chiefly regulated by 3 hypothalamic hormones with antagonistic effects - ghrh and ghih

21
Q

growth hormone releasing hormone - GRHR

A

stimulates GH release
- secreted on daily cycle - highest amounts are secreted during sleep; total amount secreted daily peaks during adolescence
- ghrh is triggered by low blood gh or glucose levels

22
Q

growth hormone inhibiting hormone - ghih

A

inhibits gh release (also called somatostatin)
- triggered by increased levels of gh and igf
- produced in various locations within the gut
* release of GH is also stimulated by ghrelin - the hunger hormone

23
Q

thyroid stimulating hormone - TSH

A
  • tropic hormone; also called thyrotropin - produced by thyrotropic cells
  • stimulates normal development and secretory activity of thyroid gland
  • release triggered by secretion of of thyrotropin releasing hormone (TRH) from the hypothalamus
  • inhibited by rising blood levels of thyroid hormones acting on pituitary and hypothalamus; also inhibited by GHIH
24
Q

adrenocorticotropic hormone (ACTH)

A
  • also called corticotropin; secreted by corticotropic cells
  • stimulates the adrenal cortex to release corticosteroids
25
Q

regulation of acth release

A
  • triggered by hypothalamic corticotropin-releasing hormone (CRH) in daily rhythm - highest levels in morning
  • rising levels of corticosteroids feed back and block secretion of crh
  • internal and external factors that alter the release of crh include fever, hypoglycemia and stressors
  • cushing syndrome
26
Q

gonadotropins (FSH and LH)

A
  • secreted by gonadotropic cells of anterior pituitary
  • fsh and lh are both absent from blood in prepubescent adolescents
27
Q

regulation of gonadotropin release

A
  • during and after puberty, fsh and lh are triggered by gonadotropin releasing hormone (GnRH) from the hypothalamus
  • suppressed via feedback of the gonadal hormones
28
Q

Follicle stimulating hormone - fsh

A

stimulates the production of gametes (egg/sperm)

29
Q

Luteinizing hormone (LH)

A

promotes production of gonadal hormones
- in females, lh helps to mature egg containing follicles, triggers ovulation, and creates + releases estrogen + progesterone
- in males lh stimulates production of testosterone

30
Q

prolactin - PRL

A
  • Secreted by prolactin cells in the anterior pituitary; structurally like GH
  • Simulates milk production in females; its role in males is not fully understood
  • Regulation is primarily controlled by prolactin-inhibiting hormone (PIH) AKA dopamine
  • PIH prevents release of PRL until it is needed; decreased levels of PIH leads to lactation
  • In females, PRL levels rise and fall in rhythm with estrogen - reason for breast swelling and tenderness during menstruation
  • Blood levels of PRL dramatically rise at the end of pregnancy
  • Nursing stimulates the release of prolactin-releasing factors and promotes continued milk production
31
Q

thyroid gland

A

butterfly shaped gland in anterior neck, located on trachea just inferior to the larynx
- largest pure endocrine gland in body

32
Q

parts of thyroid gland

A
  • Isthmus: median mass connecting 2 lateral lobes
  • Follicles: hollow spheres of epithelial follicular cells – produce glycoprotein thyroglobulin
  • Colloid: fluid in the follicle lumen, contain thyroglobulin + iodine – a precursor to thyroid hormone
  • Parafollicular Cells: produce the hormone calcitonin
33
Q

thyroid hormone - TH

A
  • body’s metabolic hormone, stored extracellularly in follicle lumen
  • affects virtually every cell in the body - enters target cells, binds to intracellular receptors within nucleus, triggers transcription
  • effects of thyroid hormone include increasing basal metabolic rate and hear production - calorigenic effect
34
Q

thyroid hormone is found in two forms:

A
  • Thyroxine (T4): major form; consists of 2 tyrosine molecules with 4 bound iodine atoms
  • Triiodothyronine (T3): form of TH that has 2 tyrosine molecules with 3 bound iodine atoms
  • T3 must be converted to T4 at the tissue level
  • both t3 and t4 are iodine containing amine hormones
35
Q

thyroid hormone pt 2

A
  • regulates tissue growth and development; essential for normal development of skeletal and nervous systems and reproductive capabilities
  • maintains blood pressure - increases adrenergic receptors in blood vessels
36
Q

regulation of thyroid hormone

A

release is triggered by thyroid stimulating hormone (TSH)
- tsh is regulated by negative feedback
- falling amounts of th stimulate release of tsh
- rising amounts of th inhibit tsh
- tsh can also be inhibited by ghih, dopamine, and increased levels of cortisol and/or iodine

37
Q

calcitonin

A
  • produced by the parafollicular cells in response to high ca2+ levls
  • antagonist to parathyroid hormone (pth)
  • does not have a known physiological role at normal levels
38
Q

elevated calcitonin levels

A
  • inhibits osteoclast activity
  • prevents release of ca2+ from bone matrix
  • stimulates the uptake of ca2+ by bone matrix
39
Q

parathyroid gland

A
  • 4 to 8 tiny yellow-brown glands embedded in posterior aspect of thyroid
  • contains oxyphil and parathyroid cells
  • parathyroid cells secrete parathyroid hormone
40
Q

parathyroid hormone - pth

A
  • most important hormone in ca2+ homeostasis - secreted in response to low blood levels of ca2+ and inhibited in response to rising blood levels of ca2+
  • target organs are skeleton, kidneys, and intestines
41
Q

functions of pth

A
  • stimulate osteoclasts to digest bone matrix and release ca2+ into blood
  • enhance reabsorption of ca2+ and secretion of phosphate (PO34-) by the kidneys
  • promote activation of vitamin D by the kidneys - leads to increased absorption of ca2+ by intestinal mucosa
42
Q

adrenal gland

A
  • paired, pyramid shaped organs sitting atop kidneys
  • sometimes called suprarenal glands
  • structurally and functionally, they are 2 glands in 1
42
Q

adrenal cortex

A

3 layers of glandular tissue - synthesize and secrete several different hormones
- produce over 24 different hormones known as corticosteroids

43
Q

adrenal medulla

A

nervous tissue - part of the sympathetic nervous system

44
Q

steroid hormones

A

not stored in cells - their rate of release is dependent on their rate of synthesis

45
Q

3 layers of cortical cells that produce different types of corticosteroids:

A
  • zona glomerulosa - mineralocorticoids
  • zona fasciculata - glucocorticoids
  • zona reticularis - gonadocorticoids
46
Q

mineralocorticoids

A

regulate electrolyte concentrations in the ECF - primarily Na+ and K+

47
Q

aldosterone

A

most potent mineralocorticoids
- stimulates reabsorption of Na+ by the kidneys; results in increased blood volume and pressure
- stimulates elimination of K+ by the kidneys

48
Q

factors that regulate the secretion of aldosterone

A
  • renin-angiotensin-aldosterone mechanism
  • plasma concentration of K+
  • adrenocorticotropic hormone (ACTH)
  • atrial natriuretic peptide (ANP)

Anatomy & Physiology 208 (39 decks)

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