Chapter 20 - Hormonal Regulation and Metabolism

endocrine systems

collects of glands of an organism that secrete hormones directly into the circulatory system

• in neuronal signaling, nerve cells release neurotransmitters that act on nearby cells

• in hormonal signaling, hormones are carried by the bloodstream to nearby cells OR other organs

neuronal vs hormonal signaling

neurotransmitters

substances in the body that send signals from nerve cells to other cells, like those in muscles and glands

within synaptic vesicles located in the axon terminal of the presynaptic neuron

where are neurotransmitters contained

an action potential moves through the neurons which causes the vesicles holing the neurotransmitters to merge with the cell membrane, releasing them

what causes neurotransmitters to be released into the synaptic cleft

myocyte

a muscle cell or muscle fiber

pancreatic β cells

what type of cells is insulin produced in

hormones are secreted into the bloodstream, which carried them throughout the body to target tissues that ay be further away from the secreting cell

how does endocrine signaling work

• different types of cells have different sets of receptors

• different cells with same receptor can have different downstream effects

• structurally similar hormones can bind different receptors

what does the hormone-receptor interactions being specific mean

interactions are high affinity so that only low amounts of hormones are needed

what does the hormone-receptor interaction having high-affinity mean

1. a 2nd messenger is released inside the cell (allosterically regulates enzymes)

2. a receptor Tyr kinase is activated

3. a hormone-gated ion channel is opened or closed (causing change in membrane potential)

4. an adhesion receptor sends info to cytoskeleton

5. a steroid bound to receptor protein in nucleus alters gene expression

5 types of “downstream” events following hormone binding

peptide hormone

what type of hormone is insulin

amine hormone

what type of hormone is epinephrine

they bind to receptors that span the membrane and induce conformational change that produced a second messenger (results in signal amplification)

what do peptide and amine hormones bind to and what change do they cause

• epinephrine binding to receptor activates adenylyl cyclase which produced cAMP

• cAMP activated cAMP-dependent protein kinase (PKA)

• PKA activates glycogen phosphorylase b kinase which activates glycogen phosphorylase b

• this breaks down glycogen to glucose-1-phosphate for energy

steps of how epinephrine binding to its receptor leads to increased energy

nuclear receptor hormones

what type of hormones are steroids, retinoids, vitamin D, and thyroid hormones

they bind to receptor in nucleus and the receptor-hormone complex binds to DNA and acts as a transcription factor → increases/decreases expression of target genes

where do nuclear receptor hormones bind and what change do they cause

water-soluble hormones are faster acting than nonpolar hormones because they work extracellularly

difference in water-soluble hormone action vs nonpolar hormone action

paracrine, endocrine, and autocrine

3 classes of mammalian hormones

path from release to target

what is classification of mammalian hormones based on

released intro extracellular space and diffused to neighboring target

paracrine hormone path of release to target

paracrine hormone

what type of hormone are eicosanoids

released to blood and carried to target cells

endocrine hormone path from release to target

endocrine and peptide hormones

what type of hormone are insulin and glucagon

affect the cell where they’re produced (but bind to surface receptors)

autocrine hormone path from release to target

synthesized as preproinsulin and processed into active form

what form is insulin originally synthesized in

secretory vesicles in β-cells

where is insulin stored

in response to increased blood glucose levels

what is insulin secreted in response to

facilitates glucose uptake

in muscle, what does insulin binding do

promoted glycogen synthesis

in liver, what does insulin binding do

promotes glycerol synthesis and inhibits breakdown of fats

in adipocytes (lipocytes and fat cells) what does binding of insulin do

3

how many disulfide bonds produces proinsulin

amino end is cleaved off of preproinsulin to get proinsulin and C-peptide is cleaved off of proinsulin to get mature insulin

conversion of preproinsulin to proinsulin to mature insulin

catecholamine hormones

epinephrine and norepinephrine are what type of hormones

hormones and neurotransmitters

norepinephrine and epinephrine both function as what 2 molecules

• concentrated in storage vesicles

• bind to extracellular receptors to generate second messengers

where are epinephrine and norepinephrine concentrated/released from and what do they bind to/generate

cholesterol

what are steroid hormones made from

by binding to carrier proteins

how do steroid hormones travel through bloodstream

food or from photolysis of 7-dehydrocholesterol in sun-exposed skin

where is vitamin D hormone obtained from

calcitriol

active form of vitamin D hormone

genes that regulate Ca²⁺, balance between Ca²⁺ deposition and removal from bone

what types of genes does vitamin D affect transcription of

arginine and O₂ by nitric oxide synthase

what is nitric oxide made from

intracellular receptor

what type of receptor does NO interact with

• activates guanylyl cyclase to increase cGMP

• cGMP activates c-GMP dependent protein kinase

• this leads to relaxation of contractile proteins in smooth muscle of blood vessels (lowers blood pressure)

what does NO activate and lead to

hypothalamus

an area of the brain responsible for linking the nervous and endocrine systems by way of the pituitary gland. It manages eating habits, sleep patterns, and temperature regulation

Pituitary gland

this small, pea-sized organ positioned at the base of the brain, is often referred to as the “master gland” due to its role in controlling other endocrine glands

thyroid gland

positioned in the neck, it released hormones that oversee metabolism and energy regulation

adrenal glands

found just above each kidney, these glands create hormones such as cortisol and adrenaline, playing key roles in managing metabolism, controlling blood pressure, and handling stress

pancreas

situated behind the stomach, this organ generates the hormones insulin and glucagon, both of which play a vital role in maintaining stable blood sugar levels

hypoglycemia

low glucose in blood

pain, fear, infection, hemorrhage, and hypoglycemia

what can cause release of cortisol

stimulus activates CNS which activates the hypothalamus which produces CRH which activates the anterior pituitary gland which produces ACHT which activates the adrenal glands which produces cortisol into the muscle, liver, and adipose tissue

explain cortisol release cascade

triacylglycerols into fatty acids which is accelerated by epinephrine

what do lipases hydrolyze and what is the reactions accelerated by

epinephrine causes cAMP-dependent cascade which leads to phosphorylation of perilipin → this gives hormone-sensitive lipase (HSL) access to lipid droplet

how is hydrolysis of TAGs accelerated by epinephrine

decrease

does insulin increase or decrease activity of hormone-sensitive lipase (HSL)

glucose (glucose → glucose 6-phosphate)

in muscles and fat what does insulin stimulate uptake of

stimulates glycogen synthase which inactivates glycogen phosphorylase (glucose 6-phosphate → glycogen)

in the liver what does insulin stimulate