Midterm study guide

Endocrine system

* discrete ductless glands that secrete hormones directly into the bloodstream
* influence metabolism, menstrual cycle, pregnancy, parturition (childbirth)
* broad influence over the body due to being carried by circulatory system

nervous system + endocrine

* interconnected and monitor each other’s activities
* endocrine = more slower and subtle and longer lasting effects

hormone

* chemical messagers released by endocrine glands
* released into bloodstream

hypothalamus

* in brain close to optic chiasm
* in diencephalon
* secretes hormones to stimulate or suppress the release of hormones in the pituitary gland
* controlls water balance, sleep, temperature, appetite, and blood pressure
* GHRH, TRH, GnRH, CRH
* link between nervous and endocrine system
* control over ANS
* neurohormones to posterior pituitary (secreted by neurones)
* no neural connection between hypothalamus and anterior pituitary
* vascular only

pituitary

* in brain, about pea sized
* controls most functions of endocrine system
* antidiuretic hormone
* ACTH
* GH
* LH and FSH
* oxytocin
* prolactin
* TSH

oxytocin

* strong stimulant of uterine contraction released during childbirth
* positive feed back
* acts as neurotransmitter in brain
* uses PIP, calcium second messenger system

thyroid

* front of throat below voice box
* metabolism, growth
* its own hormone
* iodine is essential for T3 and T4 and is absorbed by the small intestine

T4

* thyroxine
* major form that consists of two tyrosine molecules with four bound iodine atoms
* iodine containing amine hormone

T3

* triiodothyronine
* form that has two tyrosines with three bound iodine atoms
* converted to t4 at tissue level
* iodine containing amine hormone

thyroid regulation

* TH released is regulated by negative feedback
* TSH help raise TH levels
* hypothalamic thyrotropin-releasing hormone can overcome negative feedback during pregnancy or exposure to cold

steps of thyroid synthesis

* synthesis of thyroglobulin
* iodide uptake
* iodination of thyroglobulin
* storage
* release

Thyroid hormone: heart

increased heart rate, stroke volume, cardiac output and contractility

thyroid hormones: lungs

* stimulate the respiratory centers and lead to increased oxygenation because of increased perfusion

thyroid hormone: skeletal muscles

increased development of type II muscle fibers

thyroid hormones: metabolism

increases basal metabolic rate and increase glucose reabsorption, glucose synthesis, glucose oxidation

thyroid hormone: growth during childhood

stimulate bone growth, brain maturation, axonal growth and formation of myelin sheath

hyperthyroidism

excess T3 and T4 production

primary hypothyroidism

decreased production of thyroid hormones by the thyroid gland → compensatory increase of TSH

secondary hypothyroidism

pituitary disorders

decrease TSH release and decreased T3/T4 levels

tertiary hypothyroidism

caused by hypothalamic disorders

decreased TRH levels, decreased TSH and t3/t4 levels

parathyroid

* front of neck below voice box
* its own hormone
* stimulate osteoclasts to digest bone matrix and release calcium
* enhance reabsoprtion of calcium and secretion of phosphate of kidneys
* activation of vitamin D → absorption of calcium

parathyroid: skeletal system

* indirectly stimulating osteoclasts to break down bone
* increase calcium resorption

renal system

* net effect of PTH is to decrease calcium excretion and increase phosphate excretion in the urine

gastrointestinal system

* calcium absopriton in the small intetines
* PTH has no direct effects on the small intestine

hyperparathyroidism

* dangerously elevated levels of calcium in the blood
* moans, stones, bones and psychic overtones

hypoparathyroidism

* decrease function of parathyroid glands lead to low serum calcium levels
* calcium necessary for muscle and nerve functions
* weakness, paresthesias, muscle cramps, seizures

adrenals

* on top of each kidney
* regulates metabolism and maintains blood pressure
* epinephrine
* norepinephrine

kidneys

* fluid control
* renin and angiotensin
* erythropoietin

pineal body

* located in middle brain
* regulates sleep/circadian cycle of sleep
* melatonin
* specialized ganglia take the impulses generated by the light to the hypothalamus

pancreas

* behind the stomach
* digestion and blood sugar regulation
* alpha - glucagon
* beta - insulin
* delta - somatostatin
* epsilon - ghrelin
* upsilon - pancreatic polypeptide

thymus

* production and maturation of immune cells

glucagon

* extremely potent hyperglycemic agent
* triggered by decreased blood glucose levels, rising amino acid levels or sympathetic nervous system
* raises blood glucose by targeting liver

insulin

* secreted when blood glucose levels increase
* enhances membrane transport of glucose into fat and muscle cells
* inhibits breakdown of glycogen to glucose
* inhibits conversion of amino acids or fats to glucose

type 1 diabetes

* chronic autoimmune disease
* beta cells of islets of the pancreas are destroued (80%)
* genetic susceptibility, autoimmunity, environmental insult

type 2 diabetes

* progressive disease that develops
* decline in beta-cell function and/or due to a defect in insulin sensitivity that causes hyperglycemia

ovaries

* on either side of the uterus
* contains egg cells and produce estrogren and progesterone
* \

testes

* suspended outside of male body
* produces sperm and testosterone

amino acid based hormone

* water soluble
* stored in endocrine gland until needed
* act by binding to protein receptors
* binding alerts a secondary messenger molecule inside the cell that activates enzymes and other cellular proteins or influences gene expression

steroid based hormone

* produced from cholesterol - lipid soluble (can cross membrane)
* only gonadal and adrenocortical hormones
* steroids pass into a cell’s nucleus, bind to specific receptors and genes and trigger cell to make proteins

humoral stimuli

* hormone secreted in response to change in level of blood ions
* directly monitor body’s internal environment
* refers to body fluids

neural stimuli

* ANS stimulates hormone release
* directly from the nervous sytem
* typical example is adrenal stimulus from the sympathetic nervous systen

hormonal stimuli

* in response to hormones from other endocrine glands
* hierarchy
* negative feedback controls the flow of orders via hormones from one chain to the other
* hypothalamic hormones stimulate release of most anterior pituitary hormones
* anterior pituitary hormones stimulate targets to secrete still more hormones

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stimulus

something that disrupts homeostasis

sensor

detects change in homeostasis

control center

part of body that response to change and takes action

* typically the pituitary gland

effecotr

organ/cell that responds to stimulus

homeostasis maintenance

* control system works to maintain physiologic levels near ideal BP, O2 level,s HR, blood sugar

negative feedback

* way of brining disrupted values back to baseline
* causes a reverse of the current stimulus
* what the body does at rest

positive feedback

* rare
* clinical response
* works to amplify a change rather than reverse

nervous system modulation

* can make adjustments to hormone levels as needed
* can modify stimulation or inhibition of endocrine glands
* can override normal endocrine controls

target cell activation

depends on

* blood levels of hormone
* relativen umber of receptors on/in target cell
* affinity (strength) of binding between receptor and hormone

target cells must have specific receptors to which hormone binds to

amount of hormone can influence number of receptors for that hormone

up-regulation

target cells from more receptors in response to low hormone levels

down regulation

target cells lose receptors in response to high hormone levels

desensitizees the target cells to prevent them from overreacting to persistently high levels of hormone

onset, and duration

hormones circulate in blood free or bound

* steroids and thyroid hormone are attached to plasma proteins
* others circulate wthout carriers
* concentration of circulating hormone reflects rate of release and speed at which it is inactivated and removed from body

removed from body by:

* degrading enzymes or kidneys or liver

half life

time required for level of hormone in blood level to decrease by half

permissiveness

one hormone cannot exert its effects without another hormone being present

* reproductive hormones need thyroid hormone to have effect

synergism

more than one hormone produces same effects on target cell causing amplification

* glucagon and epinephrine both cause liver to release glucose

antagonism

one or more hormones oppose action of another hormone

* insulin and glucagon

adrenal gland

* cortex and medula
* deeper you go the sweeter you get
* salt, sugar, sex

cortex

produces steroid hormones including glucocorticoids, mineralocorticoids, and adrenal androgens

medulla

produces the catecholamines, epinephrine and norepinephrine

mineralocorticoids

* aldosterone is main actor
* act on kidney to increase sodium reabsorption and potassium exertion to increased blood pressure

glucocorticoids

* cortisol is the major glucocorticoid
* increases in response to stress
* essential for maintaining blood pressure
* increases sensitivity of vascular smooth muscle to vasoconstrictors and suppresses the release of vasodilators

androgens

DHEA - requires peripheral conversion to active sex steroid in the gonds

important in puberty for both males and females and are the main source of circulating testosterone in females

catecholamines

* epinephrine and norepinephring
* involved in fight or flight
* increase blood pressure
* increase serum glucose by activating glycogenolysis

cortisol

* body’s stress hormone
* suppresses the immune system
* increases gluconeogenesis and decreases peripheral glucose uptake
* oppse the actions of insulin
* net effect is an increase in serum glucose
* inhibits growth → muscle atrophy increase bon resoprtion and thinning of skin

cortisol excess

cushing syndrome

cortisol insufficiency

addison disease

cortisol: immune response

* apoptosis of proinflammatory T cells
* suppress B cell antibody production
* reduce neutrophil migration during inflammation

cortisol: stress reponse

* amygdala sends a stress signal to the hypothalamus and the adrenal glands release a surge of catecholamines such as epinephrine
* hypothalamus activates the HPA axis and cortisol is release from adrenal cortex

Cortisol + glucose

* cortisol increases availability of blood glucose to the brain
* acts on liver, muscle, adipose tissue, and pancrease

cortisol + liver

increase gluconeogenesis and decrease glycogen syntehsis

cortisol + muscle

decreased glucose uptake and consumption and increase protein degradation

cortisol + adipose tissue

cortisol increases lipolysis that releases glycerol and free fatty acids that can be used in B oxidation and as an energy source for other cells as they continue to produce glucose

cortisol + pancreas

decrease insulin and increase glucagon

addison’s disease

* autoimmune destruction of all 3 layers of the adrenal cortex
* decrease in production of mineralocorticoids, glucocorticoids and steroirds
* symptoms = fatigue, weakness, weight loss, nausea, and vomiting
* signs = ACTH will be increased (lack of feedback), hyperpigmentation, hypotension

hypercortisolism

* many different etiologies
* symptoms = insulin resistance, dyslipidemia, acne, change in fat distribution (moon facies) and (buffalo hump)

acute stress response

* cortisol secretion serves to mobalize glucose reserves for energy, inhibit pain and non vital organ systems and promote an adaptive fight or flight response

chronic stress response

* fails to function
* unmodulated inflammatory response to physical pathogens
* attenuate cortisol awakening → morning fatigue, pain, and inflammation
* osteoporosis, chornic fatigue, pevlin pain
* signs = depression, pain, memory impairments

catecholamines

stimulation of the pituitary-adrenal axis is associated with release of catecholamines

* increased cariac output, skeletal muscle blood flow, increased glucose

vasopressin

acute stress leads to rapid release of vasopressin

* stimulate secretion of ACTH from the pituitary

gonadotropins

* suppression of circulating gonadotropins and gonadal steroid hormones leading to disruption of normal menstrual cycle
* prolonged exposure to stress can lead to complete impairment of reproductive functions

thyroid hormones

function is usually down regulated during stressful conditions

growth hormones

increased during acute physical stress

insulin

decrease during stress

\-stress induced hyperglycemia

hyperthyroidism

relationship between stressful events and the onset of grave’s disease

diabetes mellitus

severe stress may be a risk factor for diabetes

gonadal dysfunction

* can lead to anovulation, amenorrhea and other menstrual irregularities
* in males can be decreased sperm count

psychosocial dwarfism

* form of failure to thrive and may be associated with dramatic behavioral abnormalies
* reversal of FH insufficency within three weeks

obesity

* mental stress leads to chronic activation of the neuroendocrine systems
* cortisol favors central fat deposition

anterior pituitary

* secretes 6 hormones
* regulates stress, growth, reproduction and lactation
* pars distalis - hormone production
* par tuberalis
* pars intermedia
* adenohypophysis
* consists of glandular tissue from outpocketing oral mucosa
* vascularly connected to hypothalamus via hypophyseal portal system
* primary capillary plexus
* hypophyseal portal veins
* secondary capillary plexus
* hypothalamus secretes releasing and inhibiting hormones to this A

hypothalamus + pituitary relationship

* connected via stalk called infundibulum
* pituitary = hypophysis
* connection = hypothalamic-hypophyseal tract
* tract arises from neurons in periventricular and supraoptic nuclei in hypothalamus
* secretes two neurohormones (oxytocin and ADH)

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posterior pituitary

* composed of neural tissue that secretes neurohormones
* posterior lobe, along with infundibulum make up the neurohypophysis
* posterior lobe is neural tissue derived from a downgrowth of brain
* technically not separate
* secretes oxytocin and antiduretic hormone

anterior pituitary hormones

ACTH, TSH, FSH, LH, GH, prolactin

adrenocorticotropic hormone (ACTH)

* target = adrenal gland
* upon secretion of glucocorticoid, mineralocorticoids, and sex corticoids
* also called corticotropin and secreted by corticotropic cells
* triggered by hypothalamic corticotropin releasing hormone

thyroid stimulating hormone

* affects the thyroid gland and the secretion of thyroid hormones
* tropic hormone called thyrotropin is produced by thryotropic cells
* triggered by thrytropin releasing hormone from hypothalamus

follicle-stimulating hormone

* targets the gonads and secretion of thyroid hormones

luteinizing hormone

targets the gonads to effect sex hormone production

growth hormone

* targets the liver and adipose tissue and promotes growth through lipid and carbohydrate metabolism
* produced by somatropic cells
* direct actions on metabolism
* indirect actions on growth
* release or inhibition chiefly regulated by hypothalamic hormones on somatotropic cells

prolactin

* target is the ovaries and mammary glands
* influences the secretion of estrogen/progesterone and milk production
* secreted by prolactin cells of anterior pituitary
* regulation primarily controlled by prolactin inhibiting hormone which is a dopamine