RAT 1

drugs that block the function of a neurotransmitter

antagonists

Why would this chapter begin with a comparison of the endocrine and nervous systems?

They work together to communicate with other cells

Operates through a series of neurons that directly affect their target cells through the release of neurotransmitters

Nervous system

Does not come into contact with their target cells

Endocrine system

Affects are often immediate but long lasting

Nervous system

Can take hours to days but are long-lasting

Endocrine system

1.) Hormones are first secreted into the interstitial fluid, after which they enter the blood

2.) They do this by diffusing through or between the cells of tiny blood vessels called blood capillaries, which are located in capillary beds. When blood exits the capillaries, it transports the hormones to the heart through larger blood vessels called veins

3.) After leaving the heart, the blood transports the hormones to the rest of the body through arteries. Eventually the arteries branch out repeatedly into smaller vessels and finally capillary beds.

4.) Once in the capillaries, the hormones will diffuse out of the blood and into the interstitial fluid to reach receptors on their target cells

Overview of hormone secretion and distribution by the blood

3 types of chemical signals

endocrine, paracrine, autocrine

endocrine pathway secreting cell

endocrine cell

endocrine pathway substance secreted

hormones

endocrine pathway transport medium

blood

endocrine pathway target cell location

distant cell

paracrine pathway secreting cell

tissue cell

paracrine pathway substance secreted

paracrine chemical

paracrine pathway transport medium

extracellular fluid

paracrine pathway target cell location

near cell

autocrine pathway secreting cell

specialized cell

autocrine pathway substance secreted

autocrine chemical

autocrine pathway transport medium

ECF

autocrine pathway target cell location

same cell

chemicals that regulate some functions of other cells

hormones

how do hormones travel

through the blood either freely or bound to proteins in the plasma

3 categories of amino-acid based hormones

amine hormone

peptide hormone

protein hormone

amine hormone

single amino acid hormone

peptide hormone

several amino acid hormone

protein hormone

complete protein hormone

2 classes of hormones

amino acid based and steroids

most amino-acid based hormones are \____________ and freely interact with water

hydrophilic

steroid hormones are derived from which chemical

cholesterol

steroid hormones are \___________ or lipid soluble

hydrophobic

small, amino-acid based hormones that are hydrophilic and able to freely associate with water

free hormones

form complexes with binding proteins in the plasma, are usually hydrophobic and do not associate with the water molecules in plasma

bound hormones

which hormones typically require protein carriers

growth hormones

what is the purpose of protein carriers

allows hydrophobic hormones to be transported safely through the blood

gives the body a reservoir of hormones that can be replaced when the need arises, which helps prevent the concentration of free hormone in the plasma from experiencing large fluctuations

extends the lifespan of a hormone in the blood

cell that has a receptor for a particular hormone

target cell

where hormone binds

have 3D shape that are highly specific for their hormones, and can bind to hormones present at extremely low concertation

receptor

how can a hormone produce opposite effects in the same cell type?

by binding to a different receptor

Where are receptors located?

can be embedded into the plasma membrane or reside within the cytosol or nucleus of the target cell

what determines the location of a receptor

depends on if the hormone is hydrophobic or hydrophilic

where the cells sensitivity to a hormone increases

up-regulation

When does up-regulation occur?

when the level of a particular hormone in the blood declines, target cells will make more receptors for the hormones which will increase the cells sensitivity to the hormone

target cells decrease the number of receptors specific for that hormone

down-regulation

when does down-regulation occur

It occurs in response to chronic exposure to an agonist. The number of receptors decreases

1.) the hydrophilic hormone (first messenger) binds to its plasma membrane, causing the G-protein to split into two subunits

2.) The G-protein subunit activates adenylate cyclase

3.) Adenylate cyclase catalyzes the formation of cAMP, the second messenger

4.) cAMP activates protein kinase A

5.) protein kinase A phosphorylates specific proteins

Mechanism of hydrophilic hormones

1.) hydrophobic hormone diffuses into the target cell

2.) hormone binds to an intracellular receptor and enters the nucleus of the cell

3.) Hormone receptor complex interacts with the DNA to initiate a cellular change

mechanism of hydrophobic hormones

what class of hormone can enter into a cell

hydrophobic hormones

which class of hormones requires a "second messenger" inside the cell

hydrophilic hormones

have more pronounced effects when working together than when acting alone

synergists

how are hormones removed from the blood

taken up by a target cell or broken down and deactivated

the amount of time it takes for the plasma concentration to decrease by half

half-life

which class of hormones tend to have a longer half-life

hydrophobic hormones

which class of hormones tend to have a shorter half-life

hydrophilic hormones

3 types of stimuli that lead to the release of hormones

hormonal stimuli

humoral stimuli

neural stimuli

growth hormone-releasing hormone (GHRH) stimulates the secretion of growth hormone (GH) from an anterior pituitary cell

hormonal stimuli

somatostatin inhibits secretion of growth hormone from an anterior pituitary cell

hormonal inhibition

glucose uptake by a pancreatic cell triggers insulin secretion

humoral stimulus

sympathetic neurons stimulate secretion of epinephrine and norepinephrine from an adrenal medulla cell

neural stimulus

hormone that stimulates the secretion of another hormone

tropic hormone

a hormone that controls the secretion of another hormone

trophic hormone

small anteroinferior portion of diencephalon of the brain

hypothalamus

What connects the pituitary gland to the hypothalamus?

infundibulum

a small organ, about the size of a bean, that sits in the sella turcica of the sphenoid bone

pituitary gland

2 components of the pituitary gland

anterior (adenohypophysis) and posterior (neurohypophysis)

true gland composed of hormone-secreting glandular epithelium

anterior pituitary gland

made up of nervous tissue

posterior pituitary gland

where capillaries are drained by veins that lead to another set of capillaries

portal system

1.) hypothalamic neurons secrete releasing and inhibiting hormones into the hypothalamic capillary bed

2.) hormones travel through portal veins in the infundibulum

3.) hypothalamic hormones exit the anterior pituitary capillary bed to bind to receptors on the anterior pituitary cells

4.) hypothalamic hormones stimulate or inhibit secretion of hormones from the anterior pituitary cells

hypothalamic-hypophyseal portal system

Where is ADH produced?

hypothalamic neurons

where does ADH travel

through the hypothalamic-hypophyseal tract in the infundibulum

where is ADH stored

axon terminals in the posterior pituitary

what organ secretes ADH

pituitary gland

what is the primary function of ADH

to increase the amount of water retained by the kidneys