bio 225 exam 3: endocrine

What is the endocrine system?

group of glands and other tissues that secrete hormones into the circulatory system/internal environment

Endocrine glands

travels to internal environment(usually to the blood stream) with no ducts and are highly vascularized(good blood supply that goes through the gland)

What is the exocrine system?

secrete chemicals into ducts that lead to the surface of the body/external environments and are poorly vascularized(not good blood supply)

Exocrine glands

Travels to external environment, have ducts, and are poorly vascularized

Examples of exocrine glands

eccrine, lacrimal, salivary, mammary, sebaceous, mucosal, prostate

Lacrimal glands

tears

Salivary glands

saliva

Sebaceous glands

sends oil to skin

Examples of endocrine glands

hypothalamus, pineal, pituitary, thyroid, adrenal, and testes/ovaries

Classical definition of hormones

Chemical substances produced by specialized organs called endocrine glands and transported through the bloodstream to other tissues where they act to elicit a specific physiological response

Classical endocrine glands

pineal, hypothalamus, pituitary, thyroid, parathyroid, thymus, adrenal, pancreas, ovaries, and testis

Pineal gland

in the brain and controls with the circadian system

hypothalamus

beginning of the endocrine system

pituitary gland

right next to the hypothalamus and is the master gland, it releases glands to control other glands

thyroid

in the neck and deals with metabolism

parathyroid

little dots in the thyroid that mainly controls calcium in the body

thymus

immune system

adrenal gland

on top of the kidneys and produces cortisol and adrenaline(epinephrine)

pancreas

endocrine gland: produces insulin and glucagon

exocrine gland: digestion

ovaries and testis

reproductive organs

Types of cell signaling

direct, autocrine/paracrine signaling, endocrine signaling, and neural signaling

Direct signaling can occur

through pores called gap junctions

Paracrine signaling occurs when

when chemical messengers diffuse from the signaling cell to nearby target cells, where they bind to receptors and initiate signal transduction pathways that cause a response

Autocrine signaling is

similar to paracrine except that the chemical messenger causes a response in the signaling cell

Endocrine signaling occurs when

chemical messengers called hormones travel long distances via the circulatory system and when it reaches the target cell, it binds to a receptor and initiates signal transduction pathways to cause a response

Neuronal signaling

electrical signals travel across long distances within a single cell through gap junctions or through the release of a neurotransmitter that binds to receptors and initiates signal transduction pathways to cause a response

Cell to cell communication and its problem

More cells means more complicated systems to communicate, plus increased mass equals increased about of cells

What do hormones do?

type of chemical messenger that is carried in the blood and can act across long distances around the body for different purposes

Cushing's syndrome

can be caused by a tumor of the adrenal gland that causes elevated secretion of cortisol OR by a tumor of the pituitary gland that releases large amounts of ACTH, which causes the adrenal glands to produce large amounts of cortisol

Symptoms of Cushing's syndrome

high blood pressure, round "moon" face, abdominal obesity, thin extremities, thin skin and stretch marks, fat pad between shoulder blades, hirsutism(increased hair growth) due to adrenal androgens, gonadal dysfunction, psychologic disorders, and muscle weakness

Addison's diseases

caused by reduced release of ACTH or CRF which results in low cortisol levels(hypocorticolism)

Symptoms of Addison's disease

Fatigue and muscle weakness, lower back pain, low blood pressure, hyperpigmentation around joints, and anxiety & depression

Graves Disease

an autoimmune disorder that causes hyperthyroidism

Graves disease symptoms

Opthalmopathy(eyes bulging out), insomnia, hand tremors, hyperactivity, hyperhidrosis, and weight loss

Autocrine/paracrine signaling secretory cell

various

Autocrine/paracrine signaling target cell

various

Autocrine/paracrine signaling maximum signaling distance

Short

Speed of autocrine/paracrine signaling

rapid

Duration of response of autocrine/paracrine signaling

Short

Nervous signaling secretory cell

neural(nerves in the nervous system)

Nervous signaling target cell

neuron, muscle, adipose, endocrine, exocrine

Signal type of nervous signaling

Electrical and chemical

Maximum signaling distance of nervous signaling

Can be long intracellular, but short across synapse

Transport between cells in nervous signaling

synapse

Transport between cells in autocrine/paracrine signaling

Interstitial fluid

Speed of nervous signaling

Rapid

Duration of response in nervous signaling

short

Endocrine signaling secretory cell

endocrine glands

Endocrine signaling target cells

various

Endocrine signaling signal type

chemical(hormone)

Maximum signaling distance of endocrine signaling

long

Transport between cells in endocrine signaling

Circulatory fluid(blood)

Speed of endocrine signaling

Slower

Duration of response of endocrine signaling

Longer

Inter-individual signaling secretory cell

Exocrine and various epithelial cells

Inter-individual signaling target cell

sensory and neural

Inter-individual signaling signal type

Chemical(pheromones)

Maximum signaling distance of inter-individual signaling

Very long

Transport between cells in inter-individual signaling

External environment

Speed of inter-individual signaling

various

Duration of response in inter-individual signaling

various

How are hormones classified by chemical class?

Peptides, steroids, amines, lipids, purines, and gases

All hormones are

chemicals

The structure of the messenger effects

the signaling mechanism(ex. hydrophobicity)

Hormones relationship with water

hydrophilic or hydrophobic

Hydrophilic messenger storage

intracellular vesicles because they have fat on the outside(cannot escape)

Hydrophobic messenger storage

Synthesized on demand, so cannot be stored in the cell

Hydrophilic messenger secretion

Exocytosis

Hydrophobic messenger secretion

diffusion across membrane

Hydrophilic messenger transport

Dissolved in extracellular fluids(ex. blood)

Hydrophobic messenger transport

Short distances: dissolved in extracellular fluid

Long distances: bound to carrier proteins(ex. albumin)

Hydrophilic messenger receptor

Transmembrane

Hydrophobic messenger receptor

intracellular or transmembrane(mostly intracellular)

Hydrophilic messengers effect

Rapid

Hydrophobic messengers effect

Slower or rapid

Peptide/protein hormones

can be between 8-300/400 amino acids, hydrophilic messenger, soluble in aqueous solutions, travel to target cell dissolved in extracellular fluid(blood)

peptide/protein hormone process

chemical messenger(hormone) binds to the ligand-binding domain, which causes a conformational change, which causes signal transduction and rapid effects on the target cell

examples of peptide/protein hormones

oxytocin, vasopressin and human growth hormone

peptide hormone production and release

1. Peptide hormones are synthesized by ribosomes on the rough endoplasmic reticulum often as large preprohormones
2. The preprohormone enters the rough endoplasmic reticulum, where the signal sequence is cleaved off(pre part is cleaved off)
3. The resulting pro hormone is packaged into vesicles to move to the Golgi apparatus for further processing and sorting
4. In the Golgi apparatus, the pro hormone is packaged into secretory vesicles, where it is cleaved into active hormone and one or more peptide fragments(pro is cleaved off)
5. The secretory vesicle fuses with the plasma membrane, releasing its contents by exocytosis(active hormone + peptide fragments)

AVP

vasopressin and antidiuretic hormone(ADH) that acts on the kidney to regulate the reabsorption of water

AVP works to control blood pressure by

increasing H20 reabsorption and constricting arterioles which increases BP

Synthesis and secretion of AVP

1. Ribosomes on the exterior of the rough endoplasmic reticulum translate the preprovasopresssin mRNA into protein
2. The signal peptide directs the newly synthesized polypeptide to the interior of the rough endoplasmic reticulum
3. The signal peptide is then cleaved off, forming provasopressin, which is packaged into secretory vesicles
4. In the secretory vesicles, provasopressin is cleaved into three different peptides: vasopressin, neurophysin, and a glycoprotein

Amine messengers

hormones that possess an amine group(-NH2), mostly hydrophilic except for thyroid hormones, have diverse effects, can be "true"(endocrine) hormones, some neurotransmitters, some both, and sometimes called biogenic amines

Examples of amine hormones

acetylcholine, catecholamines(dopamine, norepinephrine, epinephrine), serotonin, melatonin, histamine, and thyroid hormones

Steroid hormones

derived from cholesterol, synthesized by smooth ER or mitochondria, and are divided into three classses

Three classes of steroid hormones

mineralocorticoids, glucocorticoids, and reproductive hormones

mineralcorticoids

electrolyte balance(water ion balance)

glucocorticoides

stress hormones

reproductive hormones

regulate sex-speicifc chaacteristics

example of mineralcorticoid

aldosterone, which impacts sodium reabsorption and secretion of potassium for water reuptake

example of glucocorticoid

cortisol

steroid hormones are hydrophobic which means

they can diffuse through the plasma membrane, cannot be stored in the cell, must be synthesized on demand, transported to target cell by carrier proteins(ex. albumin), and bind to intracellular or transmembrane receptors(usually intracellular)

steroid hormones also have

slow effects on target cell(gene transcription), even though stress hormone cortisol has rapid non-genomic effects

Transport of hydrophobic chemical messengers

1. The local concentration of messenger is high near the signaling cell
2. Most(but not all) of the chemical messenger binds to carrier proteins.
3. The circulatory system carries the free and bound messenger to the target cell
4. Free messenger enters the target cell and binds to its receptor, decreasing the concentration of free messenger
5. This causes the bound messenger to dissociate from the carrier protein, allowing it to enter the target cell

preprohormones

large, inactive polypeptides that contain one or more copies of a peptide hormone(s) and a signal sequence that targets the polypeptide for secretion

prohormone

when the signal sequence is cleaved from the preprohormone prior to being packaged into secretory vesicles and is usually inactive

active hormones

when the secretory vesicle cuts the pro hormone with proteolytic enzyme

Ligand-receptor interactions are

extremely specific because the ligand-binding site of a receptor has a particular shape, allowing only molecules sharing related structures to bind efficiently to the receptor

Natural ligand binding causes

a response

Agonist binding

can also cause a response