Endocrine System - Epinephrine Pathway

Epinephrine

Adrenaline. Hormone produced by the adrenal glands that activates our fight or flight. Increases heart rate, blood pressure, etc. Hydrophilic so it has a membrane bound receptor and relay molecules in the cytoplasm. Cellular response to this includes turning enzymes on and off. Focusing on response pathway to blood glucose drop specifically.

Know how to label these

Hypothalamus

Links nervous system to endocrine system via anterior pituitary. Upon stressor, will either stimulate sympathetic nervous system pathway or release CRF.

Stressor

Stimulus that triggers a fight or flight stress response (adrenal hormone release). ex. tiger growl, blood glucose drop

Adrenal glands

Sit above kidneys, produce hormones including epinephrine

Adrenal medulla

Inner part of adrenal glands, secretes stress hormones like epinephrine upon signal from sympathetic nervous system

Sympathetic nervous system

Preps the body for fight or flight. Releases epinephrine from the adrenal medulla

SNS pathway from hypothalamus

Hypothalamus → sympathetic nervous system → adrenal medulla releases epinephrine into bloodstream → blood glucose drop response → enzyme led inhibition of glycogen synthesis and promotion of glycogen breakdown

Adrenal cortex

Outer part of adrenal glands, secretes stress hormones (ex. cortisol) upon signal from ACTH

Trophic hormone

Stimulates production of other hormones. Produced in the anterior pituitary. CRF and ACTH are these

Corticotrophin Release Factor (CRF)

Tropic hormone released by the hypothalamus. Stimulates the release of ACTH from the anterior pituitary gland

Adrenocorticotrophic hormone (ACTH)

Tropic hormone triggered by CRF and released by the anterior pituitary. Stimulates the adrenal cortex to release stress hormones

Production of ACTH and CRF in the anterior pituitary

CRF pathway from hypothalamus

Hypothalamus → CRF released → anterior pituitary secretes ACTH → adrenal medulla releases epinephrine → initiates stress response and increases blood glucose levels

Glycogen synthesis inhibition and glycogen breakdown promotion. Makes glucose molecules available for use

Endocrine response to epinephrine in event of blood glucose drop

Liver

Glycogen synthesis and breakdown occur in the

Reception in plasma membrane, transduction by relay molecules in cytoplasm, response (ex. turn enzymes on and off)

General signal transduction pathway

Enzymes

All chemical reactions in biological systems are catalyzed by

Liver

Pathway response to blood glucose drop occurs in the

Hormone (epinephrine), G protein coupled receptor, G protein, GDP and GTP, Adenylyl cyclase, ATP, cAMP, protein kinase A, phosphorylase kinase, glycogen synthase, glycogen synthesis inhibition, glycogen breakdown promotion

Parts included in epinephrine response

Use glucose to make glycogen

Goal is to turn off enzymes that

Hydrolyze (adding water to break down) glycogen for release into blood

Goal is to turn on enzymes that

Phosphorylation

Adding a phosphate group to a protein to result in a functional change. Requires ATP. An example of cellular work and a cellular response to a signal.

G protein coupled receptor

Activates upon receiving signaling molecule/first messenger (epinephrine) and binds to G protein

G protein

Upon receptor binding, changes shape and drops GDP. Can now bind GTP, which changes its shape again. Uncouples from membrane and can now bind adenylyl cyclase

Adenylyl cyclase

Upon binding to G protein/GTP, catalyzes phosphorylation of 4 ATP to 4 cAMP

cAMP

Second messenger in the signaling pathway. Converted from ATP through phosphorylation by adenylyl cyclase. Activates protein kinase A.

Protein kinase

Modifies other proteins by adding phosphate groups to them

Protein kinase A

Has 2 regulatory subunits and 2 catalytic. Activated when cAMP binds to its regulatory binding sites. Releases its 2 catalytic subunits.

PKA catalytic subunits

Influence glycogen synthesis and breakdown. One adds phosphates to glycogen synthase to inactivate it (this uses ATP). The other adds a phosphate to phosphorylase kinase and activates it.

Glycogen synthase

Inactivated/inhibited by PKA catalytic subunit phosphorylation. Stops synthesis of glucose into glycogen

Phosphorylase kinase

Activated by PKA catalytic subunit phosphorylation. Phosphorylizes glycogen phosphorylase to activate it

Glycogen phosphorylase

Activated by phosphorylation from phosphorylase kinase. Catalyzes breakdown of glycogen into glucose. Glucose released into bloodstream to raise blood glucose levels

Glycogen synthesis inhibition, glycogen breakdown promotion

Inhibition of glycogen synthase and activation of glycogen phosphorylase. PKA-mediated phosphorylation

Process as graphic

raise blood glucose level, vasodilation, vasoconstriction

Other functions of epinephrine depending on receptor type or intracellular protein type