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Human Physiology 2 > Ch. Sixteen: Peripheral Endocrine Glands > Flashcards

Ch. Sixteen: Peripheral Endocrine Glands Flashcards

1
Q

Thyroid Gland

A
  • Follicular cells: functional unit called follicle, lumen filled with colloid (serves as extracelleular storage for thyroid hormone)
  • Secretion of TH: produce two idodine-containing hormones derived from amino acid tyrosine
  • Tetraiodothyronine (T4) and Tri-iodothyronine (T3)
  • C cells: secrete peptide hormone calcitonin
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2
Q

Storage and Secretion

A
  • thyroid hormones remain in colloid until they are split off and secreted
  • usually enough thyroid hormone stored to supply body’s needs for several months
  • follicular cells phagocytize thyroglobuin-laden colloid
  • process frees T3 and T4 to diffuse plasma membrane and into blood
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3
Q

Thyroid Hormone: synthesis, storage, and secretion

A
  • tyrosine: synthesized in sufficient amounts by body
  • iodine: obtained from dietary intake
    synthesis:
  • all steps occur on thyroglobulin molecules within colloid
  • tyrosine-containing thyroglobulin is exported from follicular cells into colloid by exocytosis
  • captures iodine from blood and transfers it into colloid by iodine pump
  • iodine attaches to tyrosine
  • coupling process occurs between iodinated tyrosine molecules to form thyroid hormones
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4
Q

Thyroid Hormone

A
  • Amine hormone (2 tyrosines)
  • Lipophilic: carried on plasma protein and thyroxine binding globulin
  • contain iodine
  • T4 (90%) and T3 (10%): target cells cleave I from T4 (mainly liver and kidney)
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5
Q

Thyroid Gland

A
  • receptors for thyroid hormone in nuclei of most cells in body
  • gene transcription and protein synthesis
  • intracellular receptors and longer term actions
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6
Q

Effects of Thyroid Hormone

A
  • main determinant of basal metabolic rate
  • stimulates Na+/K+ ATPase
  • heat generated in glycolysis- glucose to ATP
  • Calorigenic action
  • increases target-cell responsiveness to catecholamines- sympathomimetic
  • increased B-adrenoceptors on heart
  • increases heart rate and force of contraction
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7
Q

Thyroid Hormone: normal development of nervous system

A
  • absence of T3 and T4 during fetal life
  • congenital hypothyroidism (cretinism)
  • poorly developed developed NS and severely compromised intellectual function
  • lack of iodine in pregnant mother
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8
Q

Thyroid Hormone: Carb, fat, and protein and growth

A
  • not to extent of insulin
  • increase carbohydrate absorption from Sl
  • increased fatty acid release from adipocytes
  • energy required for increased metabolic rate
  • stimulate GH release and IGF-1 production
  • enhances effects of GH and IGF-1 on target cells
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9
Q

Thyroid Hormone Major Action

A
  • metabolic rate and heat production
  • sympathomimetic
  • growth and CNA development
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10
Q

Regulation of Thyroid Hormone Secretion

A
  • TSH- tropic hormone
  • Absence: atrophy
  • excess: hypertrophy and hyperplasia- Goiter
  • TSH regulates many steps in thyroid hormone synthesis and release
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11
Q

Secretion

A
  • regulated by negative-feedback system
  • between hypothalamic TRH, anterior pituitary TSH and thyroid gland T3 and T4
  • feedback loop maintains thyroid hormones relatively constant
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12
Q

Abnormalities: Hypothyroidism

A

causes:
- primary failure of thyroid gland
- secondary to a deficiency of TRH, TSH, or both
- inadequate dietary supply of iodine
cretinism:
- results from hypothyroidism from birth- CNS effect

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13
Q

Hyperthyroidism

A
  • myxedema
  • mucopolysaccharides accumulate under skin
  • edema
  • most common cause is Graves’ disease
  • autoimmune disease
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14
Q

Hypothyroidism Symptoms and Treatment

A
  • increased sensitivity to cold- calorigenic
  • weight gain- calorigenic
  • easily fatigues
  • slow weak pulse- cardiac
  • impaired mental function
  • replacement therapy
  • dietary iodine
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15
Q

Goiters

A
  • overstimulated thyroid gland with TSH
  • may occur in hypothyroidism
    treat:
  • exogenous thyroid hormone
  • dietary iodine if cause
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16
Q

Grave’s Disease

A
  • body eroneously produces thyroid-stimulating immunoglobins (TSI)
  • acts like TSH, goiter present
  • characterized by exophthalmos
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17
Q

Hyperthyroidism Symptoms and Treatment

A
  • heat intolerance
  • weight loss including skeletal muscle (weakness)
  • increased appetite
  • increased SNS activity; anxiety, termours, increased heart rate
  • exopthalmos in Graves’ Disease (not thyroid hormones)
  • surgical removal of a portion of the over-secreting thyroid
  • administration of radioactive iodine
  • use of antithyroid drugs
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18
Q

Adrenal Cortex

A
  • outer portion
  • secretes steroid hormones
  • consists of 3 layers:
  • zona glomerulosa (outermost layer): aldosterone
  • zona fasciculata (middle and largest): coritsol, DHEA
  • zona reticularis (innermost zone): DHEA and cortisol
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19
Q

Adrenal Medulla

A
  • inner portion

- secretes catecholamines (E + NE)

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20
Q

Adrenal Steriods

A
  • Mineralocorticoids: mainly aldosterone and influence mineral balance, Na+ and K+ balance
  • Glucocorticoids: cortisol and major role in glucose metabolism as well as in protein and lipid metabolism
  • Sex hormones: identical or similar to those produced by gonads and most abundant and physiologically important is DHEA (male sex hormone)
21
Q

Adrenal Glands- Cortex

A
  • all cholesterol-based hormones: Hydrophonbic and carried by plasma proteins in blood
  • cortisol bound to corticosteroid-binding globulin (transcortin)
  • aldosterone and DHEA bound to albumin
22
Q

Mineralocorticoids Major effects on Na+ and K+ Balance

A
  • aldosterone is essential for life
  • a person dies within two days without it from circulatory shock
  • principal action site is on distal and collecting tubules of the kidney
23
Q

Aldosterone

A
  • principal action site is on distal and collecting tubules of the kidney
  • secretion is increased by RAAS, reduction in Na+ and fall in BP
  • direct stimulation by rise in plasma K+ concentration
  • independent of anterior pituitary control
24
Q

Aldosterone Hypersecretion

A
  • may be caused by hyposecreting adrenal tumour made up of aldosterone-secreting cells
  • primary hyperaldosteronism or Conn’s syndrome
  • inappropriately high activity of the RAAS; secondary hyperaldosteronism
25
Q

Aldosterone Hypersecretion Symptoms

A
  • excessive Na+ retention and K+ depletion

- high blood pressure

26
Q

Adrenal Glands

A
  • steroid hormones involved in glucose metabolism (also protein and fats)
  • glucocorticoids
  • cortisol is most abundant
27
Q

Cotisol

A
  • stimulates hepatic gluconeogenesis
  • glucose from non-carbohydrate sources (amino acids)
  • inhibits glucose uptake and use by many tissues = increased plasma glucose (but not in brain)
  • stimulates protein degradation in many tissues (muscle)
  • facilitates lipolysis
  • plays a key role in adaptation to stress
  • anti-inflammatory and immunosuppressive effects
  • admin. of large amounts (pharmacological effect)
  • treatment of many inflammatory conditions and prevention of organ transplant rejection
28
Q

Cortisol Secretion

A
  • displays a characteristic diurnal rhythm

- secretion: regulated by negative-feedback loop involving hypothalamic CRH and pituitary ACTH

29
Q

Permissive Actions of Glucocorticoids

A
  • cortisol must be present in adequate amount to permit the catecholamines to induce vasoconstriction
  • cortisol induces vasoconstriction to prevent circulatory shock in stressful situations
30
Q

Cortisol Hypersecretion

A
  • Cushing’s syndrome
  • causes:
  • overstimulation of adrenal cortex by excessive amounts of CRH and ACTH
  • Adrenal tumors that uncontrollably secrete cortisol independent of ACTH
  • ACTH-secreting tumors located in places other than the pituitary
31
Q

Cushing’s Syndrome

A
  • hyperglycemia (to diabetes mellitus levels)
  • redistribution of fat (buffalo hump and moon face)
  • muscle weakness
  • Osteoporosis
  • Immunosuppression
  • Hypertension (minus aldosterone effects)
  • hypercortisolism: stratia caused by protein breakdown in skin
  • thin legs and arms, fat on truck, face
  • red cheeck
32
Q

Treatment of Crushing’s Syndrome

A
  • surgical removal of the pituitary tumor

- Adrenalectomy

33
Q

Sex Hormones

A
  • secretes both male and female sec hormones in both sexes
  • DHEA
  • only adrenal sex hormone that has any biological importance
  • driven by ACTH, not gonadotrophins
  • overpowered by testicular testosterone in males
  • physiologically significant in females where it governs:
  • growth of pubic hair and axillary hair
  • enhancement of pubertal growth spurt
  • development and maintenance of female sex drive
34
Q

Adrenal Androgen Hypersecretion

A
  • adrenogenital syndrome
  • symptoms:
  • Newborn females- have male-type external genitalia
  • Prepubertal males- precocious pseudopuberty
  • Adult males- has no apparent affect
35
Q

Hormonal Interrelationship in Adrenogenital Syndrome

A
  • glucocorticoid therapy relieves masculinization
36
Q

Adrenal Medulla

A
  • modified part of SNS
  • primary stimulus is stress
  • releases E (80%) and NE (20%)
  • vary in their affinities for the type different adrenergic receptor types
37
Q

Epinephrine (adrenaline)

A
  • reinforces SNS
  • general systemic “fight-or-flight” responses
  • maintenance of arterial blood pressure (heart)
  • increases blood glucose and blood fatty acids
  • increases blood glucose and blood fatty acids
  • gluconeogenesis (liver) and glycogenolysis (liver and skeletal muscle)
  • inhibit insulin secretion
  • increases glucagon secretion
38
Q

Stress Response

A
  • pattern of reactions to a situation that threatens homeostasis
  • stress: generalized nonspecific response of body to any factor that overwhelms or threatens to overwhelm the body’s ability to maintain homeostasis
  • stressor: any noxious stimulus that brings about the stress response
  • all actions are coordinated by the hypothalamus
  • activation of SNS (flight or fight)
  • activation of CRH-ACTH-cortisol system (helps body cope by mobilizing metabolic response)
39
Q

Stressors

A

physical: hot/cold, trauma
chemical: reduced O2
physiological: exercise, pain
infections: bacterial
emotional: anxiety, sorrow
social: lifestyle changes

40
Q

Generalized Stress Response

A
  • elevation of blood glucose and fatty acids
  • decreased insulin and increased glucagon secretion
  • maintenance of blood volume and blood pressure
  • increased activity of RAAS and increased vasopressin secretion
41
Q

Endocrine Control of Fuel Metabolism

A
  • metabolism: all chemical reactions that occur within the cells o the body
  • intermediary metabolism or fuel metabolism:
  • includes reactions involving the degradation, synthesis, and transformation of proteins, carbohydrates, and fats
  • nutrient molecules are broken down through the process of digestion into smaller absorbable molecules:
  • proteins, carbohydrates, dietary fats
42
Q

Anabolism

A
  • buildup or synthesis of larger organic macromolecules from a small organic subunits
  • reactions usually require ATP energy
  • reactions result in: manufacture of materials needed by the cell, storage of excess ingested nutrients not immediately needed for energy production or needed as cellular building blocks
43
Q

Catabolism

A
  • breakdown or degradation of large, energy-rich organic molecules within cells
  • 2 levels of breakdown:
    1. hydrolysis of large cellular molecules into smaller subunits
    2. oxidation of smaller subunits to yield energy for ATP production
44
Q

Most important hormones in regulating fuel metabolism…

A

insulin and glucagon

45
Q

Islets of Langerhans

A
  • beta cells: site of insulin synthesis and secretion
  • alpha cells: produce glucagon
  • delta cells: pancreatic site of somatostatin synthesis
  • PP cells: least common cell, secrete pancreatic polypeptide
46
Q

Insulin

A
  • anabolic hormone
  • promotes cellular uptake of glucose, fatty acids, amino acids
  • lowers blood concentration of these small organic molecules
  • secretion is increased during absorptive state
  • blood glucose concentration is major stimulus
47
Q

Factors Affecting Blood Glucose Concentration

A

increase:
- glucose absorption from digestive tract
- hepatic glucose production: through glycogenolysis of stored glycogen and through gluconeogenesis
decrease:
- transport of glucose into cells: for utilization for energy and for storage as triglycerides and glycogen

48
Q

Diabetes Mellitus

A
  • most common of all endocrine disorders
  • prominent feature is elevated blood glucose levels (glucose in urine)
  • 2 major types:
    type 1 (10%): lack of insulin secretion
    type 2 (90%): normal or even increased insulin secretion but reduced sensitivity of insulin’s target cells
49
Q

Signs of Diabetes Mellitus

A
  • Polyuria: large volume of urine
  • extra glucose exceeds capacity of nephron to absorb it
  • with glucose, stays water= osmotic diuresis
  • sweet urine

Human Physiology 2 (10 decks)

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