Endocrine Pathways

What do Paracrine Signals do?

• diffuse short distances and stimulate nearby cells

  • ex: histamine

What do Autocrine Signals do?

• stimulate the same cell that secreted them

  • ex: hepcidin

What are different types of Eicosanoids?

• leukotrienes

• prostacyclin

• thromboxanes

• prostaglandins

Leukotrienes

• mediate allergic and inflammatory reactions

Prostacyclin

• inhibits blood clotting and vasoconstriction

Thromboxanes

• override prostacyclin and stimulate vasoconstriction

• clotting

Prostagladins

• diverse group with diverse function

Inflammatory Prostagladins

• promote fever and pain

• two cardinal signals of inflamation

Endocrine Prostagladins

• minic effects of TSH,ACTH, and other hormones

• alter sensitivity to anterior pituitary and hypothalamic hormones

Nervous Prostagladins

• function as neuromodulators

• alter the release or effects of neurotransmitters in the brain

Reproductive Prostagladins

• promote ovulation and formation of corpus luteum

• induce labor contractions

Gastrointestinal Prostaglandins

• inhibit gastric secretion

Vascular Prostagladins

• act as vasodilators and vasoconstrictors

Respiratory Prostaglandins

• constrict or dilate bronchioles

Renal Prostagladins

• promote blood circulation through kidney

• increase water retention

• electrolyte secretion

What are different types of hormonal stimuli

• neural

• hormonal

• humoral

How do hormones travel?

• through the bloodstream

What is the role of transport proteins in hormone transport?

• attach to proteins and are known as bound

• only unbound hormones can leave capillary to reach target cell

What are protein receptors?

• can be proteins or glycoproteins

• could be in plasma membrane, cytoplasm or nucleus

• receptor - hormone interactions

  • specificity

  • saturation

What are examples of hydrophilic hormones

• peptides

• catecholamines

What are properties of hydrophilic hormones

• use surface receptors

• use second messenger system

• effect are very quick

What are examples of hydrophobic hormones

• steroids and thyroid hormones

what are properties of hydrophobic hormones

• use intracellular receptors

• take several hours or days to show effect

• have a significant impact on cell metabolism

What is the reaction order cascade in signal amplification? (top to bottom)

1. hormone

2. cAMP and protein kinase

3. activated enzyme

4. metabolic process

Properties of Signal Amplification

• one hormone molecule triggers synthesis of a large number of enzyme molecules

• very small stimuli can produce massive effect

• allows circulation hormone contractions to remain relatively low

Down Regulation Steps

1. starts with high receptor density and a strong response

2. then leads to reduced receptor density and reduced sensitivity

3. diminished response

Up Regulation Steps

1. starts with low receptor density and a weak repose

2. leads to an increased receptor density and increased sensitivity

3. causes a stronger response

What are the different hormone interactions?

• synergistic effects

• permissive effects

• antagonistic effects

Example of permissive effects

• estrogen prepares uterus for action of progesterone

Example of synergistic effects

• FSH and testosterone work together on sperm production

Example of Antagonistic Effects

• insulin lower blood glucose while glucagon raises it

Synergistic Effects

• multiple hormones act together for a greater effect

Permissive Effects

• one hormone enhances the target organs response to a second hormone

Antagonistic Effect

• one hormone opposes the action of another

What is the stress response

• general adaptation syndrome (GAS)

What are the three stages of stress response

1. alarm reaction

2. state or resistance

3. stage of exhaustion

What is elevated during stress and adaptation?

• epinephrine

• cortisol

What hormones are released during the alarm stage of stress?

• norephrine

• epinephrine

What happens during the alarm stage of stress

• prepares body of fight or flight

• stored glycogen is consumed’

• increased levels of aldosterone and angiotensin levels

What is the goal of the resistance stage of stress?

• provide alternative fuels for metabolism

What hormone is released from the hypothalamus during the resistance stage of stress?

• corticotropin- releasing hormone

What hormone is released from the pituitary during the resistance stage of stress?

• ACTH

What hormone is released from the adrenal cortex during the resistance stage of stress?

• cortisol and other glucocorticoids

What is occuring during the resistance stage of stress?

• promotes breakdown of fat and protein into glycerol, fatty acids and amino acids for gluconeogenesis

What is the main result of the exhaustion phase?

• fat reserves are gone and the body cannot maintain homeostasis

  • protein breakdown and muscle wasting

What occurs during the exhaustion phase

• loss of glucose homoeostasis

• adrenal gland stops secreting glucocorticoids

• aldosterone promotes water retention

  • leads to hypertension