unit 4 endocrine secretion

what is a hormone

chemical made and/or released by endocrine cells

what do hormones usually travel through the body in

blood

neurosecretory/neuroendocrine cells

neurons that release hormones

hypothalamus makes and releases gonadotropin-releasing hormone (GnRH)

neurosecretory/neuroendocrine cell example

nonneural endocrine cells/epithelial endocrine cells

may be stimulated by another hormone; not excitable, but still releases hormones

pancreatic islet B cells make and release insulin, stimulation to release this insulin can come from gastric inhibitory peptide (GIP) hormone, the nervous system, and detection of blood sugar levels

nonneural endocrine cells/epithelial endocrine cells example

paracrine cells

influence functions of NEARBY cells

autocrine cells

influence functions of the SAME cell

paracrine and autocrine cells

release hormones that do not have to enter the blood to cause an effect

testosterone exerts widespread effects throughout body as a hormone AND functions as a paracrine signal within testes supporting spermatogenesis

paracrine/autocrine cells example

hydrophobic hormones usually bind to

intracellular receptors in the cytosol or nucleus

hydrophobic hormones influence

gene expression

hydrophilic hormones usually bind to

cell-surface receptors embedded in the plasma membrane

some steroid hormones (cortisol and some estrogens) can bind to

cell-surface membranes

hydrophilic hormones can exert ________ effects

rapid non-genomic

what are some rapid non-genomic effects

regulate ion-channel permeabilities, induce 2nd messenger cell signaling, etc

insulin is

hydrophilic, released from pancreas B cells

preparation for hibernation depends in part on insulin, what effects do they have on bears during this time

-stimulates body cells, uptake of glucose, amino acids, and fatty acids

-promotes synthesis of glycogen, triglycerides, and protein

insulin and glucagon are

peptide hormone examples

what do amine hormones come from

a single amino acid

what amino acid does melatonin (released by pineal glands in the brain) come from

tryptophan

what amino acid do catecholamines (dopamine, epinephrine, and norepinephrine) and iodothyronines (thyroxine/T4 and triiodothyronine/T3) come from

tyrosine

iodothyronines (T4 and T3) are released by the

thyroid gland

catecholamines (dopamine, epinephrine, and norepinephrine) are released by the

adrenal glands on top of kidneys

most amine hormones are

hydrophilic

T3 and T4 are

hydrophobic

steroid hormones in vertebrates are produced by

gonads and adrenal glands

steroid hormones are derived from

cholesterol

enzymes involved in the synthesis of steroid hormones are in the

mitochondria and smooth ER

steroid hormones are synthesized and secreted on demand

true

many endocrine gland secretions are controlled by hormones made in

the hypothalamus

the hypothalamus exerts

neural control and neurosecretory control

anterior vs posterior location based on this picture

anterior = left, posterior = right

neural control of neurosecretory cells are by the

hypothalamus and POSTERIOR pituitary glands

posterior pituitary gland is also called

neurohypophysis

structure of posterior pituitary gland

neural tissue made from bundles of neurons that originate in the hypothalamus

the posterior pituitary gland releases WHAT hypothalamic hormones into the capillaries

-vasopressin/antidiuretic hormone (ADH)

-oxytocin

vasopresin and oxytocin are in the same family of

9-peptide molecules

vasopressin (ADH) function

limits production of dilute urine by causing an increase in water retention from the kidneys, water returned back to blood, urine is more concentrated

oxytocin function

uterus contraction during birth, milk ejection by mammary glands during suckling

neurosecretory control of endocine cells is by

anterior pituitary gland

structure of anterior pituitary gland

made up of nonneural endocine-secreting cells

when does the anterior pituitary gland synthesize and secrete hormones

only when stimulated by specific hypothealamus’s releasing/inhibiting hormones

the anterior pituitary gland receives hypothalamus hormones through the

hypothalamo-hypophysial portal blood vessels

direct acting hormones are a type of

anterior pituitary gland hormone

direct acting hormones function

exert effects on non endocrine tissues; certain trophic hormones encourage growth/metabolism in target cells

growth hormone (GH) is produced when the hypothalamus makes/releases growth hormone releasing hormone (GHRH)

direct acting hormone example

tropic hormones come from

anterior pituitary gland

when stimulated from the hypothalamus, tropic hormones can be released that target

other endocrine tissues or tropins

thyroid-stimulating hormone (TSH) causes the thyroid to make/release T3 and T4 hormones

tropic hormone example

adrenicorticotropic hormone (ACTH) results in the adrenal glands making/releasing cortisol

tropic hormone example

stress response hormones include

glucocorticoids (cortisol, cortisone)

metabolism hormones

insulin, glucagon

metamorphosis hormones

ecdysone, juvenile hormone (JH)

process of releasing cortisol during a stress response

1. hypothalamus makes/secretes corticotropin-releasing hormone (CRH)

2. anterior pituitary gland makes/secretes adrenocorticotropic hormone (ACTH)

3. adrenal gland cortex makes/secretes the steroid cortisol

role of cortisol in metabolism

promotes an increase in blood glucose levels

two stress responses triggered by life threatening or challenging situations

sympathetic nervous system (fight or flight) or hypothalamus-pituitary-adrenal cortex (HPA) axis

early effects of the activation of sympathetic nervous system (and secretion of norepinephrine and epinephrine) do to stress

-stimulation of the immune system

-higher levels of glucocorticoids keeps immune system from overacting

-interactions between nervous, endocrine, and immunity/lymphatic systems

early physiological effects of the activation of sympathetic nervous system (and secretion of norepinephrine and epinephrine)

-increased heart rate

-increased ventilation

-increased vasoconstriction of specific regions

-decreased digestion

-increased glucagon

-increased fat catabolism

-decreased insulin

-glucose released from muscle and liver

steps for how the HPA axis can promote immunity

1. neutrophils and natural killer cells detect bacterial and viral pathogens

2. leukocytes release cytokines

3. cytokines travel to all areas in the body including the hypothalamus, and bind to CRH-secreting cells and promote glucocorticoid secretion

what are the results of the HPA axis helping a wounded animal that escaped a predator and promoted immunity

-mobilization of energy stores

-inhibit production of agents that would promote inflammation and make the animal sicker

delayed effects of glucocorticoids and the stress response

-glucocorticoids reinforce actions of the sympathetic nervous system

-inhibit growth hormone and thyroid-stimulating hormone production

-inhibit gonadotrophin hormones

delayed physiological effects of the glucocorticoids due to stress

-oppose actions of insulin

-increase muscle/bone protein catabolism

-increase amino acids

-increase liver gluconeogenesis and glucose

-inhibit TSH, gonadotropins, GH

-increase fat catabolism

-increase free fatty acids and glycerol

long term effects of stress can be deleterious

-hypertension

-muscle wasting and bone thinning due to reduced GH, T3, and T4 levels

-suppressed reproductive function due to reduced LH and FSH levels

synergism

one hormone amplifies the other

antagonism

one hormone opposes the action of another

permissiveness

presence of one hormone required for another hormone to exert its effects

what are the hormone modulations that control hormone levels

-synergism and antagonism (glucagon, insulin, epinephrine)

-permissiveness (cortisol, glucagon)

glucagon and epinephrine amplify each others effectiveness

synergism example

insulin stimulates cells to take up glucose and reduce glucose in the blood, what happens when insulin’s actions are opposed

glucose concentration in blood remains high

anatagonism is exhibited when insulin signaling is opposed by either

glucagon alone or epinephrine alone

how does insulin work to control absorbed blood glucose levels

insulin binding to insulin receptor molecules triggers signaling cascade to incorporate GLUT4 transporter molecules into cell membrane

GLUT membrane proteins in the small intestines function

aid in absorption of carbohydrates into blood

factors that will stimulate pancreas B cells to increase secretion of insulin

-increased blood glucose levels

-little to no cortisol

-parasympathetic nervous system activity

main function of glucagon

increase blood glucose levels

factors that stimulate pancreas a cells to synthesize and release glucagon

-lower blood glucose levels

-high levels of amino acids

-increased cortisol levels that act permissively to assist stimulation of glucose formation

pancreas a cells glucagon effect

-stimulate liver cells to breakdown glycogen

-promote lipid breakdown

-increase gluconeogenesis in liver cells

with high protein meals, insulin levels will also rise. insulin promotes incorporation of absorbed amino acids into body proteins. this suggests without insulin

glycogen, lipid, and protein breakdown would occur at heightened rates

insect metamorphosis involves molting to shed the exoskeleton, what are the two types

gradual metamorphosis and dramatic metamorphosis

gradual metamorphosis

hemimetabolous (incomplete) development → gradual

dramatic metamorphosis

homometabolous (complete) development → one to the next quickly

insect metamorphosis is driven by hormones

-prothoracicotropic hormone (PTTH): small peptide neurohormone made in brain

-juvenile hormone (JH): fatty acid derivative, terpene

-20-hydroxycdysone (20E): cholesterol derivative, steroid, active form of ecdysone

neurosecretory cells in the brain make and secrete _____ into the corpus allata blood supply

prothoracicotropic hormone (PTTH)

target of the prothoracicotropic hormone (PTTH)

prothoracic gland, which secretes and releases ecdysone hormone

neurosecretory cells in the brain make and secrete prothoracicotropic hormone (PTTH) into the corpus allata blood supply. in response, the corpus allatum cells make and secrete

-ecdysone

-juvenile hormone (JH)

function of ecdyson

promotes digestion of old cuticle and synthesis of a new one

corpus allatum cells perform neurosecretory release of _____ and is a _____ that secretes JH

PTTH; nonneural endocrine gland

inka cells of tracheae tubing function

secrete and release ecdysis triggering hormone (ETH) and pre-ecdysis triggering hormone (PETH)

function of ETH and PETH

coordinate muscle contractions for exiting old cuticle during every molt stage

hormonal process of metamorphosis

1. PTTH initiates molting process, ecdysone converteed to 20E promotes synthesis of new cuticle and digetion of old cuticle

2. ETH and PETH promote muscle contractions to exit old cuticle

3. JH exerts effects after 2nd instar stage and nymph stages

4. PTTH continued release allows for 20E production

5. ETH and PETH still being released

6. corpora allata cells become inactive during last larval/nymphal instar

7. 20E production with low JH, adult or pupal structures

8. JH and 20E important for successful reproduction as adult

JH secretion in adults results in

-act as a gonadotropin hormone to support production of fertile eggs and sperm

-stimulate production of pheromones

ovary secretion during insect metamorphosis

20E, stimulates production of yolk proteins to incorporate into eggs