BIO 3200: Chapter 8

What are hormones?

hormones are chemical messengers secreted into blood by specialized epithelial cells.

What are the 5 processes that fall under hormonal control?

metabolism, regulation of the internal environment, reproduction, growth, and development

How do hormones act on target cells?

1) control rates of enzymatic reactions

2) control the transport of ions/molecules across cell membrane

3) control gene expression and synthesis of proteins

Melatonin

Location: pineal gland

Primary target: brain, other tissues

Main effects: circadian rhythm, immune function, antioxidant

Trophic Hormones

Location: hypothalamus

Primary target: anterior pituitary

Main effects: phosphorlates proteins, alters channel opening

What hormones are found in the posterior pituitary?

Vasopressin and oxytocin

Oxytocin

location: posterior pituitary

Primary target: breast and uterus

Main effects: milk ejection, labor and delivery, behavior

Vasopressin (ADH)

location: posterior pituitary

Primary target: kidney

Main effects: acts on kidneys to regulate water balance in the body

What are the six hormones in the anterior pituitary?

prolactin, growth hormone (somatotropin), corticotropin, thyrotropin, follicle-stimulating hormone, lutienizing hormone

Prolactin

location: anterior pituitary

primary target: breast

main effect: milk production

Growth hormone (somatotropin)

location: anterior pituitary

primary target: liver, many tissues

main effects: growth factor secretion; growth and metabolism

Corticotropin (ACTH)

location: anterior pituitary

primary target: adrenal cortex

main effects: cortisol release

Thyrotropin (TSH)

location: anterior pituitary

primary target: thyroid gland

main effect: thyroid hormone synthesis

Follicle-Stimulating hormone (FSH)

location: anterior pituitary

primary target: gonads

main effect: egg or sperm production, sex hormone production (FSH)

Lutienizing hormone (LH)

location: anterior pituitary

primary target: gonads

main effect: sex hormone production, egg or sperm production

What hormones are found in the thyroid gland?

Thyroxine and calcitonin

Thyroxine

location: thyroid gland

primary target: many tissues

main effect: metabolism, growth, and development

Calcitonin

location: thyroid gland

primary target: bone

main effect: plasma calcium levels

Parathyroid hormone (PTH)

location: parathyroid gland

primary target: bone, kidney

main effect: regulates plasma calcium levels and phosphate levels

Which hormones are found in the pancreas?

liver, glucagon, somatostatin

Which hormones are found in the adrenal cortex?

aldosterone, cortisol, androgens

Cortisol

location: adrenal cortex

primary target: many tissues

main effect: stress respones

Androgens

location: adrenal cortex

primary target: many tissues

main effect: sex drive in females

Which hormones are found in the adrenal medulla?

epinephrine and norepinephrine

Epinephrine and Norepinephrine

location: adrenal medulla

primary target: many tissues

main effect: fight or flight response

Why isnt histamine considered a hormone?

although it travels long distances and acts on cells throughout the body, its concentrations exceed the accepted range to be considered a hormone.

Are cytokines hormones?

No, they meet the criteria, but they are synthesized and released on demand

The rate of a hormones breakdown is indicated by the hormones ______

Half-Life

What is a hormones half-life?

the amount of time required to reduce the concentration of a hormone by 1/2

A hormone has a half-life of 6 hours. Its initial plasma concentration is 160 ng/mL.

A patient is tested 18 hours later. However, at the 12-hour mark, the patient receives another dose that raises the hormone concentration by 40 ng/mL.

What is the concentration at 18 hours?

40 ng/mL

What is one indicator of how long a hormone is active in the body?

Half-life (2)

What are the three types of hormones?

peptide, steroid, and amino-acid derived

When are peptide hormones synthesized?

made in advance

How are peptide hormones stored?

in secretory vesiclese

What is the method of release from the parent cell for peptide hormones?

exocytosis

How do peptide hormones transport in the blood?

dissolved in plasma

What is the half-life of a peptide hormone?

relatively short half-lives

that makes them water-solublee

Where are peptide hormones receptors found?

On the cell membrane

What is the receptor/ligand binding response in peptide hormones?

activates second messengeer systems, may activate genes

General target response of a peptide hormone

modify existing proteins and induce protein synthesis

Examples of peptide hormones

insulin, parathyroid hormone

When are steroid hormones synthesized?

on demand from precursors

How are steroid hormones stored?

They are not stored

How are steroid hormones released from their parent cell?

simple diffusion

this is because ____ are lipid-soluble and can easily cross through the lipid bilayer of the membrane

How do steroid hormones transport in the blood?

Carrier proteins

since blood is mostly water, and steroids are lipid-soluble, they need some carrier protein to get them to their destinations

How long is a steroid hormones half-life?

a long half-life

this is due to the carrier protein protecting the hormone from enzymatic degradation

Where are steroid hormones receptors located?

Intracellular receptors in the nucleus or cytoplasm

Steroid hormones receptor-ligand response

activates genes for transcription and translation

The general target response of a steroid hormone

induce new protein synthesis

Examples of steroid hormones

estrogen, androgens, and cortisol

Amino-acid hormones are derived from which amino acid?

Tyrosine

What are the two types of amino acid hormones?

Catecholamines and Thyroid hormones

Where are catecholamines synthesized?

They’re made in advance

How are catecholamines stored?

in secretory vesicles (2)

Which method are catecholamines relased from their parent cell?ee

exocytosis (2)

Examples of catecholamines

epinephrine, norepinephrine, and dopamine

What is the half life of catecholamines?

HL is short

How do thyroid hormones get transported in the blood?

they are bound to carrier proteins

How are thryoid hormones released from their parent cells?

transport proteine

If a hormone is not a steroid or amino hormone, it must be a _______.

peptide or protein

What are preprohormones?

They are the initial peptide that comes off the ribosome thats a large, inactive protein

They contain 1 or more copies of a peptide hormone, signal sequence that directs the protein into the lumen of the rough er

What is a prohormone?

the result of the signal sequence detaching from the preprohormone, creating a smaller inactive molecule

What is pro-insulin?

a prohormone thats cleaved into active insulin and inactive c-peptide

C-peptide

used by clinicians to monitor how much insulin a patients pancreas is producing

Peptide hormones are _________, they dissolve easily in the extracellular fluid for transport in the body.

water-soluble

Why cant peptide hormones enter their target cells?

due to their lipophobic nature, they cannot cross the lipid bilayer of the cell membrane so they need a receptor on the membrane to start signal pathways intracellularly

What are all steroid hormones derived from?

cholesterol

What are the 4 organs steroid hormones are made in?

adrenal cortex, gonads (sex hormones), skin (vitamin D), and placenta

Why are steroid hormones not stored in endocrine cells?

because they are lipophilic, they would not stay contained in secretory vesicles in endocrine cells

What is the organelle where steroids are synthesized from?

smooth endoplasmic reticulum

Steroid hormones act primarily on ________ receptors.

intracellular

Where is the ultimate destination of steroid receptor-hormone complexes?

the nucleus

Why dont steroid hormones mediate reflex pathways that require rapid responses?

Because steroid hormones act through intracellular receptors and often alter gene transcription, producing relatively slow responses that are not suitable for rapid reflexes.

What is the sensor/integrating center in simple endocrine reflexes?

the endocrine cell

What is the output signal in simple endocrine reflexes?

the efferent signal

The usual response for simple endocrine reflexes is __________.

negative feedback

Negative feedback

The body detects that it has enough of something, so it turns the signal down.

What does the parathyroid hormone control?

calcium homeostasis via simple endocrine reflex

What do parathyroid endocrine cells monitor?

Plasma Ca²⁺ concentrations w/ the aid of G-protein coupled Ca²⁺ receptors on their cell membranes

After a certain amount of receptors are bound to calcium, PTH secretion is _______.

inhibited

If plasma calcium levels fall below a certain number, _______ secrete _______.

parathryoid cells ; PTH

What are the sensors that monitor blood glucose concentrations?

pancreatic endocrine cells

If blood glucose is raised above normal levels, ______ ______ cells secrete _______.

1) pancreatic beta

2) insulin

Insulin travels through the blood to its target tissues, what does this method of travel do for glucose and metabolism?

It increases their glucose uptake and metabolism

What happens when blood glucose is elevated?

Simple Endocrine Reflex:

1) the pancreatic beta cells detect an increase (sensor- endocrine cell)

2) The pancreatic beta cells release insulin

3) insulin binds to an insulin receptor on the cell membrane (peptide hormone)

4) the receptor activates an intracellular signaling pathway

5) GLUT4 containing vesicles move towards the cell membrane and insert

6) Glucose enters the cell via GLUT4 facilitated diffusion (high→ low)

7) blood glucose levels decrease

8) negative feedback detects lower BG levels and shuts off insulin secretion

What type of pathway is the glucose-insulin pathway?

Simple Endocrine Reflex pathway

What are the steps of the simple endocrine reflex for the parathyroid hormone detecting low calcium in the plasma?

1) Low plasma calcium is detected by the parathyroid cell (sensor)

2) the parathyroid cell itself secretes parathyroid hormone (PTH) (integrating center)

3) PTH travels through the blood stream

4) reaches the bone & kidney (target tissue)

5) bone resorption, kidney reabsorption of Ca 2+, and increase in calcitriol leads to increase intestinal absorption of calcium (response)

6) plasma calcium levels increase

7) negative feedback shuts off the loop

What are the two endocrine structures found in the brain?

the pineal gland and the pituitary gland

What are neurohormones?

hormones that are secreted by neurons

What are the three major groups of neurohormones?

catecholamines (adrenal medulla), hypothalamic neurohormones from posterior pituitary, and from the anterior pituitary

What connects the pituitary gland to the brain?

the infundibulum

What is the true endocrine gland of the epithelial origin?

the anterior pituitary gland

The posterior pituitary is the storage and release sites for which two neurohormones?

oxytocin and vasopressin(ADH)

Why do peptide hormones require secretory vesicles to get across the cell membrane?

Peptide hormones are water-soluble, and the cell membrane hates water, so in order to cross, they are packed in secretory vesicles that then fuse with the membrane and release the hormone to the other side via exocytosis

why are neurohormones packed in secretory vesicles transported to the posterior pituitary through axons?

Because the hypothalamus makes the neurohormone, but the posterior pituitary is where it gets released into the blood.

the hypothalamus is the cell body (where neurohormones are created)

travel down the axon

reaches the posterior pituitary axon terminal where they are stored and released

How are the neurohormones in the posterior pituitary triggered for release?

an action potential triggers the opening of voltage-gated ca²⁺ channels, calcium enters the neuron, and triggers the secretory vesicles to fuse with the membrane, ADH or oxytocin (depending on the stimulus) gets released via exocytosis

The hormones of the anterior pituitary’s secretions are controlled by __________.

The hypothalmic releasing and inhibiting neurohormones

Examples of hypothalamic hormones

dopamine, TRH, CRH, somatostatin, GHRH, GnRH

Name all of the hypothalamic hormones and their functions.

1) Dopamine- inhibiting hormone for Prolactin

2) Thyroid-releasing hormone for Thryoid stimulating hormone (TSH)

3) Corticotropin-releasing hormone (CRH) for adrenocorticotropin (ACTH)

4) Growth hormone releasing hormone (GHRH) for growth hormone/somatotropin

5) Somatostatin (SS) (GIHI) inhibiting hormone for GH

6)Gonadotropin-releasing hormone (GnRH)- for gonadotropins FSH and LH

What is the only anterior pituitary hormone that acts directly on a nonendocrine target?

Prolactin