Ch. 17 - Learning Objectives

Nervous System

• communicates →

• releases

• events

• speed

• Adapts (quickly or slowly)

communicates → electrical impulses, neurotransmitters,

releases neurotransmitters at target cells

local, specific events

Quick, localized

Adapts quickly

Endocrine System

• communicates →

• releases

• events

• responds more ______

• Adapts (quickly or slowly)

Communicates → hormones

Release hormones into bloodstream

General, widespread effects

Respond more slowly

Adapts slower

Paracine

most cells

targets nearby cells

examples of Paracrine

histamine, NO

Autocrine

A cell targets itself

examples of Autocrine

hepcidin inhibits intestinal iron absorption

“Direct Communication”

Gap Junction

Endocrine Organs

AT Paris The Adenal Plants Grow

Hypothalamus, Pituitary gland, Pineal gland

Thymus, Parathyroid gland, Thyroid gland

Adrenal glands, Pancreas, Gonads (ovaries and testes)

Neuroendocrine Organs (HPPA)

Hypothalamus, pineal gland, posterior pituitary, adrenal medulla

Secondary Endocrine Organs

skin, liver, kidney, heart, adipose tissue, GI tract(stomach, small intestine), osseous tissue, placenta

examples of steroids

testosterone, estradiol, cholesterol derivatives

Steroids traveling through blood

hydrophobic → need a special carrier protein

Monoamines examples

thyroxine, epinephrine, amino acid derivatives

Monoamines traveling through blood

hydrophilic → does not need carrier

examples of peptides & glycoproteins

Oxytocin, insulin, amino acid chains

Peptides & Glycoproteins traveling through blood

(hydrophilic or hydrophobic)

hydrophilic → does not need carrier

steroids derive from ______

• Can pass easily through ______

• Need a carrier for _____

cholesterol, membranes, blood

Monoamines

Cannot pass easily in _______

Not need a carrier in _____

membranes, blood

Monoamines derive from . . .

one amino acid (tyrosine or tryptophan)

Peptides

Cannot pass easily in _______

Not need a carrier in _____

membranes, blood

Peptides: DNA → _____ →

RNA, protein

Examples of hormonal stimulation of hormone secretion:

glucocorticoids (ex. Cortisol), Alpha islet cells secrete glucagon

Examples of neural stimulation of hormone secretion

catecholamines (dopamine, norepinephrine, and epinephrine)

Examples of humoral stimulation of hormone secretion

secretion of calcitonin, secretion of Parathyroid hormone (Ca2+ regulators)

capillary blood contains low conc. of Ca2+ which stimulates secretion of PTH

(type of stimulation)

Humoral stimulus

preganglionic sympathetic fibers stimulate adrenal medulla cells to secrete epinephrine and norepinephrine (catecholamines)

(type of stimulation)

Neural stimulation

hypothalamus secretes hormones → stimulates anterior pituitary glands to secrete hormones → stimulates other endocrine secretion

(type of stimulation)

Hormonal stimulation

Specificity

one type of receptor only binds one type of hormone

Saturation

a) the more receptors bound to hormone, the greater the response, b) once all receptors bound to hormone no additional hormone can bind & maximal response achieved

Catecholamines/peptide hormones are ________(hydrophobic or hydrophilic?)

hydrophilic

Steroid hormones are ________(hydrophobic or hydrophilic?)

hydrophobic

Thyroid hormone is ________(hydrophobic or hydrophilic?)

hydrophobic

Catecholamines/Peptide hormones

* (can or cannot) penetrate target cell

* Bind receptors at _______ _______ -

* Show effect in . . .

cannot, plasma membrane, minutes to hours

Catecholamines/Peptide hormones activate _______ processes via ______ _______

intracellular, second messengers

Steroid hormones - fat soluble

* Bind receptors in _______

* Increase _____ ______ in target cell

* Show effect in . . .

Nucleus, gene expression, Hours to Days

Sterioid hormones penetrate the _______ ______

plasma membrane

Thyroid hormone - hydrophobic

* Transported into _____

* Bind receptors in ________

* Increase _____ _______ in target cell

* Show effect in . . .

cells, Nucleus, gene expression, Hours to Days

steps involved in the transduction process that uses cAMP as a second messenger

1. Hormone-receptor binding activates G protein.

2. G protein activates adenylate cyclase .

3. Adenylate cyclase produces CAMP.

4. cAMP activates protein kinases

5. Protein kinases phosphorylate enzymes.

6. Activated enzymes promote metabolic reactions with a wide range of possible effects on the cell.

potential metabolic effects of second messenger systems

• Activation or deactivation of enzymes

• Increase or decrease in amount of protein synthesis in the cell

• Influence on glycogen metabolism (glycogenesis or glycogenolysis)

• Stimulation of mitosis

• Stimulation of apoptosis (programmed cell death)

• Promote differentiation

• Activation or inhibition of membrane channels (via ligand or change in membrane potential)

• Smooth muscle contraction

• Secretion of product

Steps of the transduction process utilized by hydrophobic hormones

Steroid hormone → _______ → receptor _____ → hormone-receptor ______ → DNA → ______ → new _____-

Steroid hormone → cytoplasm → receptor protein → hormone-receptor complex → DNA → mRNA → new protein

Estrogen binds to nuclear receptors in cells of uterus

Thyroid hormone enters cell by ATP-dependent transporter

• these are examples of ____________

transduction

Upregulation increases receptor density + sensitivity, creating a ______ response

stronger

Downregulation decreases receptor density + sensitivity, creating a ______ response

diminished

Example of upregulation:

Oxytocin receptors during childbirth

Example of downregulation:

Opioid receptors + drug tolerance

Synergistic effects

Hormones work together to produce greater effect

• FSH and testosterone on sperm production

Permissive effects

First hormone allows action of second hormone

• Estrogen permits effects of progesterone

Antagonistic effects

First hormone causes opposite effect of another hormone

• Calcitonin and parathyroid hormone on blood calcium levels

Hormonal feedback loop:

Hypothalamus → Anterior pituitary → Peripheral endocrine gland → Target cells → Action

Neuroendocrine feedback loops:

Nervous system → Endocrine gland → Target cells → action

Humoral feedback loops:

Changing levels of substance in plasma → endocrine gland → target cells → action

Hypothalamus

regulates primitive functions - e.g., H2O balance, thermoregulation, sex drive, childbirth

Pituitary gland

*composed of two structures of independent origins and separate functions:

secretes hormones as dictated by the hypothalamus

*composed of two structures of independent origins and separate functions:

• Adenohypophysis, a.k.a. Anterior pituitary

• Neurohypophysis, a.k.a. Posterior Pit

8 hormones produced by the hypothalamus

• Twin Cats Go Grow Pet Snacks

Thyrotropin-releasing hormone (TRH):

Corticotropin-releasing hormone (CRH):

Gonadotropin-releasing hormone (GRH):

Growth hormone-releasing hormone (GHRH):

Prolactin-inhibiting hormone (PIH):

Somatostatin:

Thyrotropin-releasing hormone (TRH):

Promotes secretion of thyroid-stimulating hormone (TSH) and prolactin (PRL)

Corticotropin-releasing hormone (CRH):

Promotes secretion of adrenocorticotropic hormone (ACTH)

Gonadotropin-releasing hormone (GRH):

Promotes secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH)

Growth hormone-releasing hormone (GHRH):

Promotes secretion of growth hormone (GH)

Prolactin-inhibiting hormone (PIH):

Inhibits secretion of prolactin (PRL)

Somatostatin:

Inhibits secretion of growth hormone (GH) and thyroid-stimulating hormone (TSH)

2 other hypothalamic hormones:

Paraventricular nuclei produces Oxytocin, Supraoptic nuclei produces ADH

6 hormones synthesized by the pituitary gland

Follicle stimulating hormone (FSH)

Luteinizing hormone (LH)

Adrenocorticotropic hormone (ACTH)

Thyroid-stimulating hormone (TSH)

Prolactin (PRL)

Growth hormone (GH)

Posterior Pituitary Hormones

Antidiuretic hormone (ADH)

Oxytocin (OT)

Follicle Stimulating Hormone (FSH)

Female: Growth of ovarian follicles and secretion of estrogen

Male: Sperm production

Luteinizing hormone (LH)

Female: Ovulation, maintenance of corpus luteum

Male: Testosterone secretion

Thyroid-stimulating hormone (TSH)

Growth of thyroid, secretion of thyroid hormone

Adrenocorticotropic hormone (ACTH)

• growth of _______, secretion of ________

Growth of adrenal cortex, secretion of glucocorticoids

Prolactin (PRL)

Milk synthesis

Growth hormone (GH)

Widespread tissue growth, especially in the stated tissues

Antidiuretic hormone (ADH)

water retention

Oxytocin (OT)

Labor contractions, milk release, possibly involved in ejaculation, sperm transport, sexual affection, and mother-infant bonding

steps involved in the hypothalamic-hypophysial portal system

1. Hypothalamic neurons secrete releasing and inhibiting hormones into the hypothalamic capillary bed.

2. Hormones travel through portal veins in the infundibulum.

3. Hypothalamic hormones exit the anterior - pituitary capillary bed to bind to receptors on anterior pituitary cells.

4. Hypothalamic hormones stimulate or inhibit secretion of hormones from the anterior pituitary cells.

Starting with cells in the hypothalamus and ending with the release of each of two hormones from the posterior pituitary gland, order the steps involved

1. Hypothalamic neurons make either ADH or Oxytocin

2. The hormones travel through the hypothalamic axons in the infundibulum.

3. ADH and oxytocin are stored in the axon terminals in the posterior pituitary.

4. The hormones are secreted into the blood when the hypothalamic neurons fire action potentials.

Oxytocin: stimulus

(activation of stretch receptors or myoepithelial cells)

Oxytocin: receptors

mechanoreceptors in cervix or breast tissue

Oxytocin: response

OT release from posterior pituitary into blood

Oxytocin: target tissues

smooth muscle of uterus or myoepithelial cells in breast tissue

Oxytocin: effects on target tissues

contraction of smooth muscle in uterine wall; “let down” of milk

Oxytocin: feedback

positive feedback to increase OT until stimulus stops (birth or infant stops suckling)

ADH: stimulus

(high solute concentration, low water concentration in plasma)

ADH: receptors

osmoreceptors in hypothalamus

ADH: response

ADH release from posterior pituitary into blood

ADH: target tissues

kidney tubules, smooth muscle, sweat glands

ADH: effects on target tissues

increased reabsorption of water from kidney tubules, vasoconstriction of blood vessels (at high concentrations of ADH), decreased sweat produced

ADH: feedback

Negative feedback to decrease release of ADH

Corticotropin-releasing hormone

Hypothalamic Hormone, Pituitary Hormone, Target structure/organ

Corticotropin-releasing hormone, + Adrenocorticotropic hormone, Adrenal cortex

Gonadotropin-releasing hormone

Hypothalamic Hormone, Pituitary Hormone, Target structure/organ

Gonadotropin-releasing hormone, + Follicle-stimulating hormone + Luteinizing hormone, Ovaries and testes

Growth-hormone-releasing hormone

Hypothalamic Hormone, Pituitary Hormone, Target structure/organ

Growth-hormone-releasing hormone, + Growth hormone, Liver, bone, cartilage, muscle, fat

Prolactin-inhibiting hormone

Hypothalamic Hormone, Pituitary Hormone, Target structure/organ

Prolactin-inhibiting hormone, Prolactin, Mammary glands

Somatostatin

Hypothalamic Hormone, Pituitary Hormone, Target structure/organ

Somatostatin, Growth hormone and thyroid stimulating hormone, Liver, bone, cartilage, muscle, fat

Thyrotropin-releasing hormone

Hypothalamic Hormone, Pituitary Hormone, Target structure/organ

Thyrotropin-releasing hormone, Thyroid-stimulating hormone, Thyroid gland

Long term effects of GH/somatomedins: widespread effects on body tissues

induces ______ to produce _____

Especially cartilage, bone, muscle and fat

induces liver to produce growth stimulants: Insulin-like growth factors [ IGF-I ] & [ IGF-II ] or Somatomedins

GH/somatomedins

First few minutes (make sure the brain gets its glucose)

• ________ and _________ allow for both protein sparing and glucose sparing

Lipolysis and gluconeogenesis allow for both protein sparing and glucose sparing

GH/somatomedins

Next (growth of most tissues)

• Protein synthesis

• Cell division in especially bone and muscle

• More lipolysis

• Glucose enters cells

• Necessary ions for growth are absorbed and retained so that electrolytes are available to growing

Hyposecretion of GH can result in ________

dwarfism

Hypersecretion of GH can result in ________

Gigantism

in childhood or adolescence, before growth plates CLOSE hypersecretion of GH can cause

Gigantism

Hypersecretion of GH

in adults: ________ thickening of bones and soft tissues

Especially hands, feet, and face

Acromegaly

Graves’ Disease

Bulging eyes, enlarged thyroid

Immune system produces proteins that mimic action of TSH

Disruptions in heart rhythm and BP due to synergism of TH with SNS

TRH and TSH are low

Hashimoto’s disease

______ deficiency

_________: No Thyroid Hormone ➔ no negative feedback → TRH and TSH

Iodine deficiency

Hypothyroidism: No Thyroid Hormone ➔ no negative feedback → TRH and TSH

the TSH → excessive

stimulation of thyroid → thyroid inflammation → development of a Goiter