a&p 2 ch 18 - endocrine system

endocrine system

produces and releases hormones in blood

hormones

control & coordinate body processes

hormones change ___

enzymes & structural proteins in target cells

hormones alter ___

metabolic activites of tissues & organs at the same time

hormones affect ___

growth & development

classes of hormones:

1.amino acid derivatives

2.peptide hormones

3.lipid derivatives

amino acid derivatives

small molecules structurally related to amino acids

example of amino acid derivatives:

derivatives of tyrosine

• thyroid hormones, catecholamines

• (E, NE, dopamine)

peptide hormones

made from chains of amino acids

most peptide hormones are synthesized as ___

prohormones

prohormones

an inactive form of a hormone that the body changes into its active form when it’s needed

example of peptide hormone

insulin

lipid derivatives

are hormones derived from fatty acids or cholesterol, including steroid hormones and eicosanoids

steroid hormones

derived from cholesterol

examples of steroid hormones

androgens from testes in males

estrogen & progesterone from ovaries in females

corticosteroids from adrenal cortex

eicosanoids

derived from arachidonic acid

example of eicosanoids

prostaglandins

transport of hormones

hormones may circulate freely or travel bound to special carrier proteins

do free hormones need carrier proteins for transport in blood?

no

free hormones ____ need carrier proteins for transport in blood

do not

free hormones remain functional for ___

less than an hour

free hormones are inactivated when they ___

diffuse out of blood stream

when are free hormones inactivated?

when they diffuse out of blood stream

free hormones bind to receptors on ___

target cells, broken down by liver, kidneys, or enzymes in blood or interstitial fluids

bound hormones are attached to ___

specific transport proteins in plasma

bound hormones stay in circulation ___

longer than free hormones & are functional longer

what type of hormone stays in circulation longer?

bound hormones

what type of hormone is functional longer?

bound hormone

example of bound hormone:

steroid hormones

hormone receptor

a protein that hormones attach to so they can send signals to the cell

where are hormone receptors found?

on target cells

presence or absence of a specific receptor determines __

hormonal sensitivity of a cell

more hormone receptors implies ___

more sensitivity

down-regulation

presence of a hormone triggers a decrease in the number of hormone receptors

down-regulation occurs when ___

blood levels of a hormone are high

when blood levels of a hormone are high, __

cells become less sensitive to it

up-regulation

absence of a hormone triggers an increase in the number of hormone receptors

up-regulation occurs when ___

blood levels of a hormone are low

when blood levels of a hormone are low, __

cells become more sensitive to it

extracellular membrane receptors are used by __

not lipid soluble hormones (catecholamines, peptide hormones)

not lipid soluble hormones

hormones that don’t have a specific membrane channel

not lipid soluble hormones in extracellular membrane receptors are ___

unable to pentrate plasma membrane

extracellular membrane receptors bind to ___

extracellular proteins

intracellular membrane receptors are used by ___

lipid soluble hormones (steroid hormones, thyroid hormones)

lipid soluble hormones

hormones that have specific membrane channels

examples of not lipid soluble hormones:

catecholamines, peptide hormones

examples of lipid soluble hormones

steroid hormones and thyroid hormones

intracellular membrane receptors diffuse ___

across plasma membrane & bind to intracellular receptors

first messenger

the hormone that binds to its receptor on the cell surface to initiate a response

first messenger promotes release of ___

second messenger in cell

second messenger

intermediary molecule that appears due to hormone-receptor interaction

second messenger may act as ___

enzyme activator, inhibitor, or cofactor

second messenger results in ___

change in rates of metabolic reactions

examples of second messengers:

cAMP, cGMP, Ca2+

G-protein

a protein that helps pass a signal from a receptor on the cell surface to the inside of the cell

G-protein is involved in the link between ___

first and second messenger

G-protein → cAMP pathway (speeding up cell activity):

1. G-protein ON → turns on adenylate cyclase.

2. Adenylate cyclase → converts ATP to cAMP

3. cAMP = second messenger → carries the signal inside the cell.

4. cAMP → activates kinases → add phosphate to proteins → cell does more work.

5. Signal is temporary → PDE breaks cAMP → AMP → stops the signal.

G-protein → calcium pathway:

1. G protein turns on phospholipase C (PLC).

2. PLC splits membrane phospholipids into diacylglycerol (DAG) and inositol triphosphate (IP3).

3. IP3 releases Ca²⁺ from inside the cell.

4. DAG opens channels for Ca²⁺ to come in from outside.

5. Ca²⁺ levels rise in the cell.

6. Ca²⁺ binds calmodulin, which activates enzymes.

steroid hormones alter __

rate of DNA transcription in nucleus, which causes synthesis of enzymes

steroid hormones directly affect __

activity and structure of target cells

thyroid hormones bind to ___

receptors within nucleus and on mitochondria

thyroid hormones increase ___

rates of ATP production

blood hormone levels are controlled by ___

negative feedback mechanisms to maintain homeostasis

hormone secretion can be triggered by __

3 types of stimuli: humoral, hormonal, & neural stimuli

humoral stimuli

hormone release triggered by changes in blood or body fluid levels of things like ions or nutrients

hormonal stimuli

hormone release triggered by another hormone

neural stimuli

hormone release caused by neural input

hypothalamus regulates __

functions of the pituitary gland

the hypothalamus synthesizes ___

ADH & oxytocin & transports them to the neurohypophysis for release

the hypothalamus secretes __

regulatory hormones that control the anterior pituitary gland

regulatory hormones

control secretory activity of anterior pituitary gland

releasing hormones

stimulate synthesis & secretion of hormones at anterior pituitary gland

inhibiting hormones

prevent synthesis & secretion of hormones at anterior pituitary gland

regulatory hormones are controlled by ___

negative feedback

the pituitary gland hangs __ to the hypothalamus

inferior

the anterior and posterior lobes of the pituitary gland are connected by the ___

infundibulum

the pituitary gland releases __

9 important peptide hormones

hypophyseal portal system

transports regulatory hormones from hypothalamus to anterior pituitary gland

hypophyseal-hypothalamic tract

transports ADH & oxytocin to the neurohypophysis for storage

target cells/organs

the specific cells or organs that a hormone affects

messages carried by hormones are only read by target cells ___

after binding

Follicle-Stimulating Hormone (FSH) in women:

helps eggs grow in the ovaries

Follicle-Stimulating Hormone (FSH) in men:

Helps sperm develop in the testes

Luteinizing Hormone (LH) in women

Triggers ovulation and helps make progesterone

Luteinizing Hormone (LH) in men

Stimulates testosterone production

Follicle-Stimulating Hormone (FSH) vs Luteinizing Hormone (LH)

FSH is mostly about growth and development, while LH is about triggering/inducing release and hormone production.

production of FSH & LH is stimulated by __

gonadotropin-releasing hormone

adrenocorticotropic hormone (ACTH)

released when the hypothalamus sends out corticotropin-releasing hormone (CRH)

when is the adrenocorticotropic hormone released?

when the hypothalamus sends out corticotropin-releasing hormone

what does the hypothalamus have to send out in order for the adrenocorticotropic hormone to be released?

corticotropin-releasing hormone

what does the adrenocorticotropic hormone do?

stimulates the adrenal cortex to produce cortisol and other glucocorticoids

prolactin release is inhibited by:

dopamine (prolactin-inhibiting hormone)

prolactin release is stimulated by:

prolactin-releasing hormone

the regulation of prolactin release is controlled by ___

prolactin-inhibiting hormone (dopamine)

what stimulaes prolactin release?

suckling

suckling promotes ___

continued milk production

prolactin stimulates ___

breast tissue to release breast milk

regulation of growth hormone is regulated by the ___

hypothalamic hormones

growth hormone-releasing hormone (GH-RH)

increases blood growth hormone levels

growth hormone-inhibiting hormone (GH-IH)

decreases blood growth hormone levels