Feeling Hormonal

Autocrine communication

***transmission through extracellular fluid

***occurs when the messages affect the same cells that secrete them

• chemical mediators are called autocrines

paracrine communication

****transmission through extracellular fluid

**when cells within a single tissue communicate through the release and receipt of chemical messages

• chemical mediators are called paracrines

Pituitary gland

The master gland ——little big papa

the two lobes together secrete 9 different hormones

30

the number of hormones that regulate human activities

parathyroid hormone functions

• stimulation of calcitriol production at the kidneys

• stimulation of osteoclasts

• enhanced absorption of calcium ions and PO₄^3– in the digestive tract

leptin

released from adipose tissue

causes a sense of fullness and satiety

thyroid hormone effects on peripheral tissue

• stimulation of the formation of red blood cells

• increased heart rate and force of contraction

• elevated levels of oxygen consumption and energy consumption

addison and cushing diease

results from abnormal glucocorticoid production by the adrenal glands

intercellular communication

the process through which cells communicate with each other through hormones and neurotransmitters

synergistic effect

the net result is greater than the sum of the hormones’ individual effects

EX) glucose-sparing action of GH and glucocorticoids

permissive effect

when the first hormone is needed for the second to produce its effects

EX) epinephrine does not change energy consumption unless thyroid hormones are also present in normal concentrations

integrative effect

hormones may produce different, but complementary, results in specific tissues and organs——important in coordinating the activities of diverse physiological systems

EX) The differing effects of calcitriol and parathyroid hormone on tissues involved in calcium metabolism

opening of calcium channels and interaction with calmodulin

when a hormone stimulates this, it will trigger the activation of cytoplasmic enzymes

*****calcium ions are second messengers when in combination with calmodulin (intracellular protein)——> activates cytoplasmic enzymes

exocrine glands

secrete glands into ducts

includes: sudoriferous (sweat), sebaceous (oil), mucous, and digrestive

Natriuretic peptides

***released by specialized cardiac muscles when they are stretched by an abnormally large venous return

****Promotes fluid loss and reductions in blood pressure and in venous return

• Includes ANP and BNP

two major types of glands

include endocrine and exocrine

nervous and endocrine system

****two main systems involved in intercellular communication

***work together to regulate homeostasis

infundibulum

a slender, funnel-shaped structure that connects the hypothalamus to the pituitary gland

sellar diaphragm

holds the pituitary gland in place

sella turcica

bony depression that houses the pituitary but does not connect to the hypothalamus

response patterns in endocrine system

most effective in coordinating cell tissue and organ activities on a sustained long-term basis

how hormones affect target cells

****work by changing the types, quantities, or activities of important enzymes and structural proteins:

• can stimulate the synthesis of specific enzymes or structural proteins

• affecting rate of transcription or translation——increase or decrease the rate of synthesis of particular enzymes or proteins

• turning existing enzyme or membrane channel ‘on” or “off”

positive feedback

amplifies a change until an event ends the loop

Endocrine communication

***transmission via the bloodstream

**occurs when the endocrine system uses hormones to relay information and instructions between cells in distant portions of the body

• chemical mediators are hormones

eicosanoids

****lipid derivative

signaling molecules and include leukotrienes, prostaglandins, thromboxanes, and prostacyclins

two classes of lipid derivatives

• eicosnoids

• steroid hromones

hypothalamus

***Big Big Papa——the real “master gland”
*contains both brain and endocrine stuff

• hypothalamic neurons synthesize hormones and transport them along neurons to the posterior lobe of the pituitary gland

***inferior to the thalamus and superior to pituitary gland

two classes of peptide hormones

• glycoproteins

• short polypeptides and small proteins

chief cells

specialized cells in the parathyroid gland that secrete parathormone

hormones important for normal growth

• GH

• Thyroid hormones

• Insulin

• PTH

• reproductive hormones

as we age

there is a decline in the concentration of reproductive hormones

peptide hormones

includes all the hormones secreted by the:

• hypothalamus

• pituitary galnd

• heart

• kidneys

• adipose tissue

• digestive tract

• pancreas

pancreatic acini

secretes large quantities of an alkaline, enzyme-rich fluid used to digest materials in the duodenum

Ways the hypothalamus regulates the endocrine system

Regulates the functions of both lobes of pituitary gland

• secretes regulatory hormones that control the secretory activities of endocrine cells in the pituitary anterior lobe

• also has autonomic centers that exert direct neural control over endocrine cells of the adrenal medulla——-controls sympathetic output from the adrenal gland

hormones

chemical messengers used by the endocrine system to RELAY information

****must get to target cell receptor to change metabolic activities—→ homeostasis

simple reflex

DIRECT—-involves one hormone

the endocrine cell respond to changes int he composition of the extracellular fluid and regulated secretion of the hormone

hypothalamus secretions

regulatory hormones, oxytocin, and ADH in response to the changes in the composition of the circulating blood

pulses

when hypothalamic and pituitary hormones are released in sudden bursts——→ causes target cells to vary in their response depending on frequency of bursts

Target cells

specific cells in other tissues that have receptors needed to bind and "read" the hormonal message when it arrives——any cells that contain membrane receptors for glands

G proteins and calcium ions

1) g protein first activates the enzyme PLC

2) enzyme triggers receptor cascade——produces DAG and IP3 from membrane phosophilipids

3) IP3 diffuses into the cytoplasm and triggers the release of CA2+

4) DAG + CA+ = PKC—→ this activation leads to opening of ion channels and extracellular CA+ to enter—→ setups positive feedback loop

5) CA+ serve as messengers——> calmodulin activation

stimuli that can trigger hormonal secretion

• humoral stimuli

• hormonal stimuli

• neural stimuli

activated g protein

can trigger the opening of CA+ channels or the release of CA+

humoral stimuli

changes in composition of the extracelluar fluid, including blood

***in control of hormone secretion of heart, pancreaes, parathyroid glands, and digestive tract

hormonal stimuli

arrival or removal of a specific hormone—-can trigger an endocrine reflex

neural stimuli

the arrival of neurotransmitters at neuroglandular junctions

EX) ANS nerves can signal adrenal gland to release the hormone norepinephrine into the blood

direct communication

***transmission via gap junctions

occurs between two cells of the SAME type——must be in extensive physical contact

*****function as a single entity (because of how close they communicate)

***distribution is limited to adjacent cells of the same type that are interconnected by connexons——chemical mediators include ions, small solutes, and lipid-soluble materials

Synaptic communication

***transmission across synapses

neurons release a neurotransmitter at a synapse very close to target cells that have the appropriate receptors

• chemical mediators are neurotransmitters

Endocrine system

the endocrine (ductless) glands and organs of the body

kidneys

produces hormones that regulate blood pressure

parathyroid principal cells

produce parathyroid hormone

parathyroid glands

***posterior surface of the thyroid glands

regulates calcium levels in the blood——-when Ca2+ concentration of the blood falls below normal, cells secrete PTH—→ increases Ca2+ in bodily fluids

Parathyroid Hormone (PTH)

**mobilizes calcium from bone by affecting osteoblast and osteoclast acitivty

**enhances teh resorption of Ca2+ by the kidneys, reducing urinary losses

**stimulates the formation and secretion of calcitriol by the kidneys

ductless glands

another name for the endocrine glands——called this because they secrete their hormones into the surrounding extracellular fluid instead of secreting into a duct

Endocrine cells

glandular secretory cells that release their secretions into the extracellular fluid

Exocrine cells

secrete their products onto epithelial surfaces, generally by way of ducts

Amino acid derivatives

aka biogenic amine

**** relatively small molecules that are structurally related to amino acids

Catecholamines

epinephrine, norepinephrine, dopamine, and related compounds

Hormone receptor

a protein molecule to which a particular molecule binds strongly

Down-regulation

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

****cells become LESS sensitive to high levels of a particular hormone

Up-regulation

a process in which the absence of a hormone triggers a increase in the number of hormone receptors

****cells become MORE sensitive to low levels of a particular hormone

extracellular receptors (hormones)

hormone receptors located on plasma membranes

intracellular receptors (hormones)

hormone receptors located within target cells

commands from the nervous system

very specific and short-lived

****there are only a small fraction of all the cell in the body that are inverted

commands from the endocrine system

effects are slow to appear but long-lasting (days)

****hormones produced by endocrine cells reach almost every cell in the body

First messenger

a hormone that binds to an extracellular receptor

major processes affected by hormones

• growth and development

• reproduction

• regulation of cell metabolism and energy balance

• regulation of body water content and levels of electrolytes and organic nutrients

• mobilization of body defenses

• sleep

• temperature

• stress management

Second messsenger

an intermediary molecule that appears due to a hormone-receptor interaction—-includes:

• derivative of ATP

• cAMP

• cGMP

• derivative of GTP

• 3 calcium ions

Amplification

magnifies the effect of a hormone on the target cell

Receptor cascade

arrival of a single hormone promoting the release of more than one type of second messenger, or the production of a linked sequence of enzymatic reactions

biogenic amino hormones

***adrenal medulla

Epinephrine, norepinephrine, dopamine, melatonin, and thyroid hormones

G protein

an enzyme complex coupled to a membrane receptor

***link to hormones to second messengers within the cell and amplify the hormone’s effect

gap junctions functions

****help coordinate ciliary movement along epithelial cells

****coordinate the contractions of cardiac muscle cells

****facilitate the propagation of action potentials from one neuron to the next at electrical synapses

Steps involved in increasing the cAMP level

1- the activated G protein activates the enzyme adenylate cyclase

2- adenylate cyclase converts ATP to the ring-shaped molecule cyclic AMP

3- cyclic AMP then functions as a second messenger, typically by activating a kinase

4- generally, cyclic AMP activates kinases that phosphorylate proteins

hypogonadism

low production of gonadotropins

***children do not mature sexually = adults that cannot produce functional sperm or oocytes

Kinase

an enzyme that attaches a high-energy phosphate group to another molecule in a process called phosphorylation

hormone binding effects

• alter genetic activity

• alter the rate of protein synthesis

• change membrane permeability

hormones release location

near where capillaries are abundant so the hormones can quickly enter the bloodstream

***to transport nutrients and hormones thorughout the body

Pineal gland

***main part of the epithalamus

***contains pinealocytes

• secretes melatonin which influences the circadian rhythm

• inhibits reproductive functions

• protects against damage by free radicals

pinealocytes

special secretory cells of pineal gland

freely circulating hormone

***remains functional for LESS than an hour (sometimes less than 2 minutes)

when a freely circulating hormone becomes inactivated

• diffuses out of the blood stream and binds to receptors on target cells

• is absorbed and broken down by cells of the liver or kidneys

• broken down by enzymes in the blood or interstitial fluids

thyroid and steroid hormones

***remains functional for much longer than freely circulating hormones

***more than 99% of them become attached to special transport proteins

each hormone has an equilibrium state that exists between its free and bound forms

bound hormones

***hormones that are bound to special carrier proteins (like thyroid and steroid hormones)

are released to replace free hormones as they are removed and inactivated

****bloodstream contains a CONSTANT substantial reserve

follicle-stimulating hormone (FSH)

***type of gonadotropins

promotes ovarian follicle development——in combo with luteinizing hormone stimulates estrogen secretion

complex reflex

Negative Feedback

***primary control mechanism for hormone secretion

mechanism of response in which a stimulus initiates actions that reverse or reduce the stimulus

Complex endocrine reflex

INDIRECT—-”chain of command”

—-involves the hypothalamus, the pituitary gland, and two or more hormones

works in junction with the nervous system

Stimulus—→ Hypothalamus—→ adenohypophysis—→ peripheral gland—→ action and homeostasis

Pars distalis

Anterior Pituitary Gland

The largest and most anterior part where most hormones are produced

Pars intermedia

Anterior pituitary

narrow band bordering the posterior lobe of pituitary

****MSH is released from this region

Hypophyseal portal system

direct blood link to the hypothalamus

Tropic hormone

hormone that stimulates other endocrine glands to secrete hormones

Gonadotropic hormones

***hormone of anterior lobe of pituitary gland

hormones that regulate functions of gonads——> production is stimulated by GnRH

Two types include:

• Follicle-stimulating hormone

• Luteinzing hormone

Thyroid-Stimulating Hormone (TSH)

****hormone of anterior lobe of pituitary

Targets the thyroid gland and triggers the release of thyroid hormones

****released in response to TRH from the hypothalamus

Adrenocorticotropic hormone (ACTH)

***hormone of anterior lobe of pituitary

Targets the zona fasciculata of adrenal cortex—-stimulates the release of steroid hormones by the adrenal cortex——-specifically targets cells that produce glucocorticoid hormones for glucose metabolism

Luteinizing Hormone (LH)

****type of gonatropin

In females: Induces ovulation—→ promotes ovarian secretion of estrogens and progesterone

In males: stimulates the production of sex hormones (androgen and testosterone) by interstitial endocrine cells of testes

Prolactin (PRL)

**hormone of anterior pituitary gland

In female: stimulates mammary gland development (boobies hehe)

• in pregnancy and during the nursing period——stimulates milk production

In males: makes interstitial endocrine cells more sensitive to LH to help regulate androgen production (we think lol)

Growth Hormone (GH) / somatotropin

**hormone of anterior pituitary gland——>causes liver cells to release somatomedins that increase the rate of uptake of amino acids

accelerates the rate of protein synthesis = stimulates cell growth and division

***skeletal muscle and chondrocytes (cartilage) is especially sensitive but EVERY tissue responds in some way

****regulated by GHRH and GH-IH from the hypothalamus

Indirect action of GH

***primary mechanism in GH sitmulating growth

liver cells respond to GH by synthesizing and releasing somatomedins (IGFs)——> peptides stimulate tissue growth by binding to receptors——>increase the uptake of amino acids and their incorporation into new proteins

***develop almost immediately after release of GH***

direct action of GH

***WAY more selective and than indirect

• Epothelia and connective tissue: stimulates cell divsion and daughter cell differentiation

• Adipose uses glucose-sparing effect

• Liver uses diabetogenic effect

glucose-sparing effect

***direct action of GH in ADIPOSE tissue

GH stimulates the breakdown of stored triglycerides by fat cells (adipocytes)——> release fatty acids into bloods—→ tissues stop breaking down glucose to generate ATP and INSTEAD start breaking down the fatty acids

diabetogenic effect

***direct action of GH in LIVER

****extreme elevation of blood glucose level by GH

GH stimulates the breakdown of glycogen reserves by liver cells——> release glucose into bloodstream, causing glucose concentration to raise significantly