Endocrine System: Key Concepts and Hormone Functions

endocrine and nervous

serves as a major control systems of your body

hormones

communicate with and control other body cells

bloodstream

Where are the endocrine cells secreted

nervous

What is faster? endocrine or nervous?

widespread and long lasting

what is the range of effect for the endocrine system?

interstitial fluid

Hormones are released from endocrine gland cells into _________ which then enter the blood

leave the capillaries and enter the interstitial fluid to bind to receptors of target cell

After hormones are transported within the blood, what happens?

Regulating development, growth, and metabolism

Maintaining homeostasis of blood composition and volume

Controlling digestive processes

Controlling reproductive activities

what are the four general functions of the endocrine system?

connective tissue framework of endrocrine glands

houses and supports epithelial tissue that produces and releases hormones from their secretory cells

endocrine organ

a single organ that is entirely endocrine in function

Endrocrine cells

housed in tissue clusters within specific organs or tissues - organs have other primary function as well

thyroid gland, pituitary gland, and adrenal gland

example of endocrine organs

hypothalamus, pancreas, thymus, kidneys

example of organs whose primary function is NOT endocrine

Reflex

a preprogrammed, involuntary response of a muscle or a gland to a stimulus

hormonal stimulation

release of a hormone in response to another hormone

humoral stimulation

release of a hormone in response to changes in level of nutrient or ion in the blood

nervous system stimulation

stimulation by the nervous system triggers release of the hormone

Circulating hormones

transported within the blood

Local hormones:

short-lived molecules that influence cells within the local tissue from which they are produced

Cholesterol

a type of lipid; modified in the synthesis of steroid hormones

Amino acids

building blocks for both biogenic amines and protein hormones

Steroids

includes both the hormones produced within the gonads - synthesized by the adrenal cortex

lipid

are steroid lipid or water soluble

biogenic amines (monoamines)

monoamines - modified amino acids

catecholamines

epinephrine and norepinephrine - released from the adrenal medulla

Thyroid Hormone

released from the thyroid gland

it is lipid soluble

how is the thyroid hormone different from other biogenic amine s

Melatonin

released from the pineal gland

proteins

water-soluble hormone that are small chains of amino acids

autocrine stimulation

synthesize and release molecules, which bind with either the same cell that produced them

paracrine stimulation

synthesize and release molecules, which bind to neighboring cells

local hormones

signaling molecules have properties similar to hormones because the released ligands (signaling molecules) initiate and regulate cellular changes

signaling across gap junctions

a cell targets a cell connected by gap junctions

Endorcine System function

cell targets a distant cell through the blood stream

carrier proteins

Lipid-soluble hormones do not dissolve within the aqueous environment of the blood so they require what?

selective or nonselective ; temporary

properties of carrier proteins

protecting them from getting destroyed early (longer half-life)

function of carrier proteins

bound hormone

Any hormone that is attached to a carrier protein

unbound (free) hormone

unattached hormone

Bound Hormone Function

serve as a readily available source within the blood (do not actually bind to receptors just yet)

unbound hormone function

can generally exit the blood and bind to cellular receptors of target organs

Hormone release

hormone is released from an endocrine gland and hormone concentration within the blood correspondingly increases (vice versa)

enzymatic degradation

hormone removal by hepatocytes

excretion from the kidneys

hormone removal by urine

uptake into target cells

hormone removal by uptake

negative feedback

maintain blood levels of hormone, a balance between the two is required

postitive feedback

when hormone is released progressively more ex: oxytocin

water soluble

what hormone has a short half life

protected by carrier proteins

why do lipid soluble hormones have a longer half life

lipid soluble hormones are small and non-polar making them easily diffuse

Why is the plasma membrane not an effective barrier to lipid-soluble hormones

water soluble hormones

Polar molecules that are unable to cross the plasma membrane

plasma membrane

stimulation is initiated when the hormone binds to a _____ receptor

signal transduction pathway

The binding of water-soluble hormones to plasma membrane receptor initiates a series of biochemical events

hormone

What's the first messenger of the water-soluble signal transduction pathway

second messenger

binding of the hormone to its receptor results in the formation of a different molecule

adenylate cyclase and phospholipase C activity

what are the two types of signal transduction pathway

adenylate cyclase

Activated by a G-protein. Converts ATP to cyclic AMP in response to an extracellular signal.

cAMP

whats the second messenger of adenylate cyclase

phospholipase C activity

Activated G protein activates phospholipase C

Phospholipase C splits PIP2 into diacylglycerol (DAG) and inositol triphosphate (IP3)

DAG and IP3

whats the second messengers in phospholipase C activity

-Activation or inhibition of enzymatic pathways

-Stimulation of growth through cellular division

-Release of cellular secretions

-Changes in membrane ion permeability

-Muscle contraction or relaxation

What are the second messenger results

up-regulation

Target cell can increase the number of receptors

high number of receptors

A low concentration of hormones leads

Synergistic interaction

activity of one hormone reinforces the activity of another

Permissive interaction

One hormone "gives permission" to the first to function

Antagonistic interaction

activity of one hormone opposes the effects of another

infundibulum

A stalk that attaches the pituitary gland to the hypothalamus.

neurohypophysis

posterior lobe of the pituitary gland - neural section

adenohypophysis

anterior pituitary gland - endocrine portion

Antidiuretic hormone • Oxytocin

what are the hormones that are stored in posterior pituitary

hypothalamus

where are Antidiuretic hormone and Oxytocin synthesized

neurosecretory cells

neurons in the hypothalamus

Antidiuretic hormone (ADH)

released during dehydration that helps maintain fluid balance

kidneys, thirst center in hypothalamus, and blood vessels

What are the target cells for ADH

blood osmolarity decreases due to the increased water retention and the signal to release ADH is reduced or stopped

What would be the negative feed back response for ADH?

positive feedback

Oxytocin feedback

Oxytocin

improves our mood and alters our physiology from physical contact

Releasing hormones (RHs)

stimulate the production and secretion of specific anterior pituitary hormones

Inhibiting hormones (IHs)

decrease the production and secretion of specific anterior pituitary hormones

• Thyroid-stimulating hormone • Prolactin • Follicle-stimulating hormone & Luteinizing hormone • Adrenocorticotropic hormone • Growth hormone

What are the six major hormones

growth hormone

hormone secreted by anterior pituitary gland that stimulates growth of bones

thyroid gland

butterfly-shaped structure located inferior to the thyroid cartilage of the larynx

Follicular cells

produce and later release thyroid hormone

parafollicular cells

synthesize and release calcitonin

Adrenal medulla

the inner portion of each gland (nervous tissue)

Adrenal cortex

the outer portion (endocrine tissue)

adrenal medulla

Releases catecholamines (epiand norepinephrine) by activation of the sympathetic division

mineralocorticoids

(hormones that help regulate the composition and concentration of electrolytes in body fluids

zona glomerulosa - outermost layer of adrenal cortex

Cells synthesize mineralocorticoids ex: aldosterone

Zona fasciculata - middle and larger region of adrenal cortex

region synthesizes glucocorticoids (cortisol and corticosterone)

Zona reticularis - innermost region

secrets minor amounts of sex hormones, "gonadocorticoids"

Cortisol: Cushing Syndrome

excessive levels of glucocorticoid hormones (stress hormone)

Corticosteroids

powerful immunosuppressant drugs

pancreatic islets

endocrine cells of the pancreas

Alpha cells (primary)

secrete glucagon

Beta cells (primary)

secrete insulin

Type 1 diabetes

Autoimmune destruction of β (beta) cells in the pancreas and body can not produce insulin

Type 2 diabetes

Combination of insulin resistance and β-cell dysfunction over time - t cells don't respond properly to insulin

Ghrelin

released when the stomach is empty (or mostly empty), such as during fasting or overnight sleep

Leptin

satiety hormone, signals the brain to "feel full" -> less interest in food