L1: Hormones and Regulation

Flashcards covering the major concepts from the lecture notes on hormones, endocrine signaling, hypothalamic-pituitary regulation, and related metabolic pathways.

endocrine system

series of glands or isolated cells that produce hormones

How do hormones reach their target cells?

They travel through the bloodstream to reach target cells

what are the chemical messengers of the nervous system?

neurotransmitters

what is a characteristic of steroids?

derived from cholesterol

what is a characteristic of peptides?

composed of several amino acids

what is a characteristic of amines?

derived from single amino acids

what makes up endocrine glands?

ductless glandular epithelial cells

what are some examples of functions that endocrine hormones influence in the body?

1. metabolism

2. growth

3. reproduction

4. homeostasis

why can hormones attach to their target cells rather than every cell in the body?

target cells have specific receptor for that hormone

What distinguishes hormones from neurotransmitters?

Hormones are chemical messengers released into the bloodstream for long-distance signaling, while neurotransmitters are released across synapses for rapid, localized communication between nerve cells

What is autocrine signaling?

A cell secretes a hormone that binds to receptors on its own surface

What is paracrine signaling?

A cell releases signaling molecules that affect nearby cells

how do water-soluble hormones travel?

travel freely in blood

how do lipid-soluble hormones travel?

bind to carrier proteins in blood

what is an example of a water soluble hormone?

peptide

what is an example fo a lipid-soluble hormone?

steroids

when will hormones stop traveling in the bloodstream?

1. they are bound to their target cell

2. they have been broken down and deactivated

MCQ: how does the way a hormone is transported in the blood affect its half-life?

hormones bound to carrier proteins have a longer half-life because they are protected from degradation and filtration by the kidneys

Where do target cell receptors for water-soluble hormones reside and what type are they?

Cell-surface receptors on the plasma membrane

what is the cellular response for cell-surface receptors?

Activation of intracellular signaling pathways via secondary messengers

what is the cellular response for intracellular receptors?

regulation of gene expression

what are examples of secondary messengers for cell-surface receptors?

cAMP, calcium ions, IP3

target cells

cells that have specific protein receptors designed to bind with hormones

Where do target cell receptors for lipid-soluble hormones reside and what type are they?

Intracellular receptors in the cytoplasm or nucleus

metabolic changes

activation or inhibition of enzymes involved in a specific metabolic pathway

what is the timeframe for cellular responses to hormones?

minutes, hours, or days

Name the four basic classes of hormones according to biochemical structure.

1. Steroid hormones

2. peptide/protein hormones

3. amine hormones

4. eicosanoids

what are steroid hormones derived from?

cholesterol

how are steroid hormones transported?

carrier proteins

why do steroid proteins have a longer half-life?

protein binding protects against quick degradation in the liver

what type of receptors do steroid hormones interact with?

intracellular receptors

steroid hormones are _________ and can go through the ________ of the _________ of their target cells

1. lipo-soluble

2. bilipid bilayer

3. plasma membrane

what type of receptors do peptide hormones interact with?

cell-surface receptors on target cells

what type of receptors do amine hormones interact with?

cell-surface receptors on target cells

what is the exception for the type of amine hormone that interacts with intracellular receptors?

thyroid hormones

what are the most typical amine hormones?

tyrosine or tryptophan

eicosanoids

a group of bioactive lipid compounds derived from arachidonic acid and other fatty acids

how are eicosanoids produced?

enzymatic conversion of arachidonic acid by cyclooxygenases (COX) and lipoxygenase (LOX)

what do eicosanoids bind to?

specific receptors on the surface of the target cell

peptide hormones are _____ and easily _______ meaning they are _____

1. water-soluble

2. dissolved in plasma

3. unbound

How are peptide hormones synthesized and stored?

1. Stimulus triggers gene transcription to code for hormone gene

2. active hormone is stored in vesicles until secretion

why is the synthesis of peptide hormones less convienient?

peptide must be transcribed

why is having the lipid droplets convienient for synthesis of steroid hormones?

can be converted to hormone quickly

Where does the first step of steroid hormone synthesis occur and what is produced?

In the mitochondria, cholesterol is converted to pregnenolone

Why do steroid hormones rely on mitochondria during synthesis?

Mitochondria house the enzymes that convert cholesterol to pregnenolone

what is the mechanism of action for peptide hormones?

1. hormone binds to receptor on cell’s plasma membrane

2. enzyme in cell either activated or inhibited

3. if activated, a secondary messenger increases in cytosol

4. enzyme regulate key metabolic pathways

what is the mechanism of action of steroid hormones?

1. hormone diffuses freely across cell membrane

2. bind to intracellular receptors in cytoplasm or nucleus

3. bind to regions of nuclear DNA

4. gene transcription is initiated, leading to protein synthesis and cellular response.

List the hypothalamic hormones that regulate the anterior pituitary.

1. TRH

2. CRH

3. GHRH

4. GHIH

5. GnRH

6. PRH

7. Dopamine

what is the hypothalamic regulators for TSH?

TRH

what is the hypothalamic regulators for ACTH?

CRH

what is the hypothalamic regulators for FSH?

GnRH

what is the hypothalamic regulators for LH?

GnRH

what is the hypothalamic regulators for GH?

GHRH and GHIH

what is the hypothalamic regulators for Prolactin?

PRH and Dopamine

what does dopamine do to prolactin?

inhibits production of hormone

TRH

Thyrotropin-releasing hormone

CRH

Corticotropin-releasing hormone

GHRH

Growth hormone-releasing hormone

GHIH

Growth hormone-inhibiting hormone

GnRH

Gonadotropin-releasing hormone

PRH

Prolactin-releasing hormone

What hormones are released by the posterior pituitary and where are they produced?

Antidiuretic hormone (ADH) and oxytocin; produced by the hypothalamus and stored/released by the posterior pituitary.

What is the correct pair of hypothalamic factor and the anterior pituitary hormone it stimulates?

1. GnRH stimulates FSH (and LH)

2. TRH stimulates TSH

3. CRH stimulates ACTH

4. PRH stimulates PRL

5. Dopamine inhibits PRL

6. GHRH stimulates GH.

What are the main roles of the hypothalamus in endocrine regulation?

Integrates nervous and endocrine systems, coordinates endocrine and autonomic activity, and controls the pituitary via releasing/inhibiting hormones.

what are the two basic configurations of negative feedback within the endocrine system?

1. hypothalamic-pituatary-endocrine axis feedback

2. physiological response-driven configuration

hypothalamic-pituatary-endocrine axis feedback

system is hiearchic

1. hypothalamus

2. pituatary

3. endocrine gland

physiological response-driven configuration

secretion of a hormone is stimulated or inhibited by a change in the level of a specific extracellular parameter

what is the peripheral endocrine gland responsible for producing?

endocrine hormones

where do tropic hormones travel in an endocrine axis response?

1. systemic circulation

2. pituitary hormone

what feedback mechanism in hormone regulation is not driven by the hypothalamus?

physiological response-driven configuration

What are the two major targets of hypothalamic hormones reaching the anterior pituitary?

Tropic hormones that regulate peripheral endocrine glands (e.g., thyroid, adrenal cortex, gonads).

What are the hormones released by the posterior pituitary and their origin?

ADH and oxytocin; produced in the hypothalamus and stored/released from the posterior pituitary.

catabolism

energy is released and heat is produced; this is when an animal needs an energy source

anabolism

storage of energy

what metabolic process requires ATP?

anabolism

what is the preferred fuel for all tissues?

glucose

what molecules can be converted to ATP?

1. proteins

2. fats

3. carbohydrates

what are the glucose-dependent tissues?

1. CNS

2. RBC

3. retina

4. renal medullla

5. fetus

6. lactation

describe the pathway for converting carbohydrates to ATP

1. Carbohydrates

2. Glucose

3. Pyruvate

4. Acetyl-CoA

5. Krebs Cycle

6. Respiratory chain-oxidative phosphorylation

7. ATP

what molecules can be converted back into glucose?

1. proteins

2. fatty acids

how are adequate concentrations of blood glucose achieved?

1. absorbing glucose in GI

2. storing glucose

3. releasing glucose

4. synthesis of new glucose

what are the gluconeogenic precursors?

1. amino acids

2. glycerol (fats)

3. lactate

4. propionate (with ruminants)

What is glycogenesis and where does it occur?

Synthesis of glycogen from glucose in the liver and muscle, stimulated by high glucose and insulin.

What is glycogenolysis?

Breakdown of glycogen

where is glucose-6-phosphate located?

Liver cells NOT IN MUSCLE CELLS

what will fasting stimulate?

since there are low levels of glucose, glucagon secretion will be stimulated

what enzyme is required to produce free glucose from glucose-6-phosphate in the liver?

glucose-6-phosphatase in the liver (not in muscle) converts glucose-6-phosphate to free glucose.

What stimulates lipolysis?

1. Glucagon

2. epinephrine

3. cortisol

lipolysis

conversion of excess glucose and amino acids into free fatty acids

where will lipolysis occur?

1. adipocytes

2. mammary gland

3. liver

what is important to understand about lipogenesis with the liver

it does not store fat, it repackages the FFA in the form of tricglycerides to then become very low density lipoproteins

which enzyme is key in adipocytes?

hormone-sensitive lipase (HSL)

what stimulates HSL?

1. glucagon

2. epinephrine

3. cortisol

lipolysis

stored triglycerides in adipocytes are broken down by HSL into FFA and glycerol which will enter circulation

what can glycerol be converted into?

glucose

What happens during beta-oxidation of fatty acids in the liver?

Excess fatty acids undergo beta-oxidation producing acetyl-CoA, which can form ketone bodies when in excess

What are the ketone bodies and when are they formed?

Acetoacetate, acetone, and beta-hydroxybutyrate produced during excess acetyl-CoA from fat metabolism.

What is deamination and what does it produce?

Removal of an amino group from an amino acid, forming a keto-acid and ammonia.

What is transamination and which enzymes catalyze it?

Transfer of amino groups catalyzed by aminotransferases (ALT and AST).

Why is ammonia converted to urea in the liver?

Ammonia is highly toxic; the liver converts it to urea for safe excretion via the kidneys