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
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
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
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)
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
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
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
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
9
Q
Thyroid Hormone Major Action
A
- metabolic rate and heat production
- sympathomimetic
- growth and CNA development
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
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
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
13
Q
Hyperthyroidism
A
- myxedema
- mucopolysaccharides accumulate under skin
- edema
- most common cause is Graves’ disease
- autoimmune disease
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
15
Q
Goiters
A
- overstimulated thyroid gland with TSH
- may occur in hypothyroidism
treat: - exogenous thyroid hormone
- dietary iodine if cause
16
Q
Grave’s Disease
A
- body eroneously produces thyroid-stimulating immunoglobins (TSI)
- acts like TSH, goiter present
- characterized by exophthalmos
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
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
19
Q
Adrenal Medulla
A
- inner portion
- secretes catecholamines (E + NE)
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
