Chapter 16: Endocrine System Flashcards

Diverse and decentralized

Inhibitory hormones

Systemic hormones

Melatonin

Leptin

Atrial natriuretic factor

Erythropoietin, IGF

Steroids, catcholamine

Estrogen, inhibin

Testosterone, inhibin

Secretin

Calcitriol, angiotensin II

Insulin, glucagon

Gastrin

- Thyroxine (T4)

- Triiodothyronine (T3)

- Calcitonin

Parathyroid hormone (PTH)

Neuroendocrine

- Thyroid stimulating hormone

- Adrenocorticotropic hormone

- Luteinizing hormone

- Follicle stimulating hormone

- Growth hormone

- Prolactin

- Antidiuretic hormone

- Oxytocin

- Mineralocorticoids (aldosterone)

- Glucocorticoids (cortisol)

- Gonadocorticoids

Epinephrine and norepinephrine (catecholamines)

- Thymosin

- Thymopoietin

Releases chemical messengers (hormones) into the bloodstream

- Only cells with receptors for that particular hormone will respond

Long-distance chemical messengers, traveling in the blood or lymph to bind to receptors on their target organs

Hormones which target organ is another endocrine gland, affecting its activity

Chemical messengers that exerts effects on the same cells that secrete them (not considered endocrine)

Chemical messengers that affect neighboring cells (not considered endocrine)

Amino acid derivatives, peptides, and proteins

Synthesized from cholesterol and gonadal and adrenocortical hormones

- Lipophilic

- Plasma, cytosolic, and nuclear receptors

- Endocrine

- Ex: estrogen

- Lipophilic

- Cytosolic and nuclear receptors

- Endocrine

- Ex: thyroxine

- Hydrophilic

- Plasma receptors

- Endocrine

- Ex: adrenocorticotropic hormone

- Hydrophilic

- Plasma receptors

- Endocrine

- Ex: growth hormone

- Hydrophilic

- Plasma receptors

- Paracrine

- Ex: ATP

- Lipophilic

- Plasma receptors

- Endocrine like

- Ex: prostaglandin f2a

- Lipophilic

- Cytosolic receptors

- Paracrine

- Ex: nitric oxide

- Hydrophilic

- Plasma receptors

- Paracrine

- Ex: acetylcholine

- Regulation of physiological processes

- Variety in chemical structure

- Released in low quantities

- Movement through diffusion or plasma

- Bind to receptors on target cells

- Released in response to changes in homeostasis

Receptor levels

Increasing receptor levels on target cells

Decreasing receptor levels on target cells

The process of hormones regulating the receptor levels of other hormones

Amplitude-modulated

- Release in "all or nothing"

- Vary in frequency

- Levels never approach zero

- Fluctuate between high and low

Inactive form

- Encoded by genes

- Multiple peptide hormones can be encoded by one gene

- Signal peptide: directs hormone to correct intracellular organelle for processing

- Biochemically synthesized from amino acids

- Store within vesicles

- Ex: epinephrine

- Changes in a critical physiological factor (ex: ions)

- Direct input from the nervous system through neurohormone release

- Actions of other hormones (ex: hypothalamic regulation of pituitary gland)

- Mechanical stresses or cellular metabolism

Transported

- >99% bound to transport protein, <1% free

- Some excreted in urine (if chemically modified to be more water-soluble)

- Otherwise excreted in GI tract

- 100% free

- Smaller than kidney filtration barrier

- Excreted in urine

Time required to reduce blood concentration of a hormone by 50%

- Increased synthesis

- Increased secretion

- Binding to transport proteins

- Modification of structure

- Decreased synthesis

- Decreased secretion

- Excretion by kidney or bile

- Enzymatic degradation, addition of a side chain, or reabsorption by the kidney

Metabolism

1. based on their chemical structure

2. based on their receptor location (integral protein on plasma membrane vs. intracellular receptor)

Act on integral protein receptors on plasma membrane or via second-messenger systems, since they are not able to enter the cell

Act on intracellular receptors that can directly activate enzymes or regulatory sequences on DNA, as they can enter the cell

1. Integral plasma membrane receptor

2. Second-messenger system

Receptor embedded on plasma membrane

- Receptors on plasma membrane exert effects of hormone binding by activating a 2nd intracellular messenger

- cAMP (cyclic adenosine monophosphate)

- PIP2- calcium (phosphatidyl inositol bisphosphate calcium)

- Integral membrane proteins

- Extracellular region binds hormone

- Intracellular region interacts with G-proteins

- Gas

- Gai

- Gaq

- Activates adenylate cyclase (AC)

- Converts ATP to cAMP

- Inhibits adenylate cyclase (AC)
- Blocks production of cAMP

Activates phospholipase C (PLC)

- Breaks down PIP2 into IP3 and DAG

- Activates protein kinase A (PKA)

- Degraded by phosphodiesterase (PDE)

- IP3 causes Ca2+ release from ER

- DAG activates protein kinase C (PKC)

- Integral membrane proteins

- Extracellular region binds hormone

- Intracellular region contains a kinase domain; directly activates enzymes without G-proteins

- Found inside the cell

- Act as transcription factors

- Generally cytoplasmic proteins complexed with heat shock proteins (HSPs)

- Hormone binding leads to dissociation of HSPs, dimerization to a second bound receptor, and translocation to the nucleus

Grave's disease (hyperthyroidism)

Jansen's metaphyseal chondrodysplasia

Ovarian dysgenesis type I

Familial glucocorticoid definciency

Familial male precocious puberty

Familial hypocalciuric hypercalcemia

Hypogonadotropic hypogonadism

- Located inferior to the thalamus; part of the limbic system

- Contains many distinct nuclei that produce and release unique hormones

- Is sexually dimorphic (different between men and women)

- Hypophyseal portal system connects hypothalamus and anterior pituitary via two capillary beds in series

Pituitary gland

Effect at anterior pituitary: TSH and prolactin release

Effect at anterior pituitary: ACTH release

Effect at pituitary: GH release

Effect at pituitary: FSH and LH release

Effect at pituitary: inhibition of prolactin release

Effect at pituitary: inhibition of GH and TSH release

- Located inferior to the hypothalamus

- Composed of anterior, intermediate and posterior lobes

- Anterior lobe: subdivided into pars tuberalis and pars distalis

- Two pituitary areas do not regulate each other

- Oxytocin

- Antidiuretic hormone

- Movement of mammary milk into subaereolar sinuses (milk ejection/letdown)

- Stimulation of uterine contraction during pregnancy

- Social behavior: feelings of contentment, reduced anxiety, calmness

- Renal system: increased expression of aquaporin channels (increased water absorption); increased interstitial osmolarity (increased water, Na+ reabsorption)

- Cardiovascular system: vasoconstriction

- CNS: aggression, blood pressure, body temperature regulation

- Benign (65% of the time)

- Invasive (0.1%)

- Carcinoma (35%)

- Over-secretion of one or two hormones

- Eye disorders (compression of optic nerve)

- Severe headaches

- Under-secretion of some hormones

- Found lateral to the upper trachea

- Made up of two lobes connected by highly vascularized band of tissues called isthmus

- Contains follicles that store thyroglobulin, the substrate for thyroxine

- Parafollicular cells are scattered between follicles and secrete calcitonin

- Cold, nutrient status

- Increased lung ventilation

- Increased metabolic rate (liver)

- Increased lipolysis in adipose tissue

- Increased protein catabolism in muscle

- Increased heart rate, force contraction, cardiac output

1. Iodide ions transported into follicular cells

2. TSH stimulates TG synthesis and storage within follicles

3. Iodide is oxidized to iodine by thyroid peroxidase; diffuses to follicle lumen

4. Iodine atoms are covalently attached to tyrosine residues on thyroglobulin, forming MIT or DIT

5. Two DIT molecules join to form T4, or one MIT and one DIT join to form T3

6. Follicular cells take up iodinated thyroglobulin by endocytosis. Within endosomes, proteolytic enzymes release thyroxine from TG

7. Thyroxine is released into blood bound to proteins (ex: TBG or albumin)

- Four parathyroid glands (2 embedded in each thyroid gland)

- Densely-packed with chief and oxyphil cells

- Mainly secrete parathyroid hormone (PTH)

- Bone: increased resorption

- Kidney: increased calcitriol

- Intestine: increased calcium reabsorption

- Embedded in adipose tissue in the superior regions of the kidney

- Composed of endocrine and nervous tissue

- Organized into zones which are structurally and functionally distinct

- Mineralocorticoids (aldosterone)

- Glucocorticoids

- Androgen precursors

- Zone glomerulosa

- Increases Na+ resorption (urine, sweat glands, salivary glands, colon), increased renal K+ excretion

- Zone fasciculate

- Hyperglycemia, immunosuppression, increase lipolysis, decreased glucose uptake into skeletal muscle, increased gluconeogenesis, increased protein degradation

- Zona reticularis

- Converted to androgens; direct effects on testes and ovaries, bone-protective effects, increased neuron survival

- Found under skin, around organs, in bone marrow, within muscle and breast tissue

- Composed predominantly of adipocytes along with fibroblasts, macrophages and endothelial cells

- Releases hormones (leptin (hormone that makes you feel full), adiponectin (modulates insulin response), resistin

- Main hormone functions: regulating body metabolism, weight, reproductive function and inflammation

- Lies beneath the greater curvature of the stomach and small intestine

- Bulk of mass is exocrine tissue/ducts

- Produces pancreatic juice and secretes it into the small intestine for digestion

- Clusters of endocrine cells are scattered throughout; produce insulin and glucagon

- a cells (20%): secrete glucagon

- b cells (70%): secrete insulin and amylin

- delta cells (3-10%): secrete somatostatin

- PP cells (3-5%): secrete pancreatic polypeptide

- E cells (1%): secrete ghrelin

A and b chains held together by disulfide bonds

- Secreted in response to increased blood glucose concentrations

- Insulin facilitates glucose entry into muscle, adipose and other tissues, through GLUT4

- Increases glucose in liver through multiple mechanisms

- Synthesized as pro-glucagon in pancreatic a cells

- Proteolytically processed to yield glucagon

- Secreted in response to low blood glucose concentrations

- Mainly affects the liver to increase blood glucose levels

- Stimulates breakdown of liver glycogen and stimulates gluconeogenesis

Decrease in body mass

Loss of TSH regulated functions

Loss of bone mass

Decreased ability to regulate arterial blood pressure

Reduced production of sperm, menopause

Fewer mature, functional lymphocytes