(8) Lecture #20 - Adrenal hormones (mineralocorticoids/corticosteroids) and Hunger

Your body cannot distinguish…

physical stress from emotional stress.

 Stress hormones

physical stress from emotional stress-

Both increase:

• Epinephrine - Short-term stress hormone.

• Cortisol - Main long-term stress hormone.

Epinephrine

Effects:

• ↑ heart rate

• ↑ blood pressure

• ↑ blood sugar

• ↑ free fatty acids

• prepares body for fight-or-flight

Cortisol

• ↑ blood glucose

• ↑ gluconeogenesis

• ↑ protein breakdown (muscle breakdown)

• anti-inflammatory

• suppresses immune system

• Acute cortisol =

• Chronic cortisol =

• Acute cortisol = helpful

• Chronic cortisol = disease

Endocrine system =

Nervous system =

Endocrine system = slow chemical communication

Nervous system = fast communication

 Endocrine system basics

Purpose:

maintain homeostasis

Endocrine system basics

Hormones act only on…

cells with the correct receptor.

Control of endocrine system

Hypothalamus

• monitors internal environment

• main control center

Pituitary gland

• “middle manager”

Pituitary lobes

• Posterior pituitary → nerves

• Anterior pituitary → hormones

 

Neurohormone:

• acts as neurotransmitter

• also acts as hormone in bloodstream

Neurohormone

example

ADH = vasopressin

what pathway we talk about

Growth hormone pathway

Thyroid pathway

Adrenal pathway

Gonadal pathway

Growth hormone pathway

Hypothalamus → GHRH

Pituitary → GH

Liver → IGF-1

Thyroid pathway

Hypothalamus → TRH

Pituitary → TSH

Thyroid → T3 and T4

Important:

• T3 = more active

• T4 = reserve

T3/T4 control basal metabolic rate.

Adrenal pathway

Hypothalamus → CRH

Pituitary → ACTH

Adrenal cortex → Cortisol

Gonadal pathway

Hypothalamus → GnRH

Pituitary → LH + FSH

Target → sex hormones

Male:

• LH → testosterone

• FSH → sperm production

Female:

• LH + FSH → estrogen

Adrenal gland has two parts:

• Cortex (outer)

• Medulla (inner)

Aldosterone

Major mineralocorticoid hormone.

 Aldosterone

Functions:

• ↑ sodium retention

• water follows sodium

• ↑ water reabsorption

• ↑ potassium excretion

Aldosterone

Rule:

Where sodium goes, water follows.

Aldosterone

Triggers:

• low sodium

• low blood volume

• high potassium

 RAAS system

Renin-Angiotensin-Aldosterone System

RAAS system

Trigger

• low blood pressure

• low blood volume

• dehydration

• bleeding

RAAS system

Steps

1. Kidney releases renin

2. Renin forms angiotensin I

1. ACE converts angiotensin I → angiotensin II

1. Angiotensin II → adrenal cortex

2. Adrenal cortex releases aldosterone

RAAS system

Effects:

• ↑ sodium reabsorption

• ↑ water reabsorption

• ↑ blood pressure

• Angiotensin II causes vasoconstriction.

ADH / Vasopressin

Functions:

• kidneys reabsorb water

• maintain blood pressure

Hunger hormones

1. Ghrelin

2. Leptin

Ghrelin

Source:

Released when…

Function:

Memory trick:

Source: stomach

Released when stomach empty.

Function: stimulates hunger

Memory trick: Ghrelin = hungry

Leptin

Source:

Function:

Memory trick:

Source: fat tissue

Function:

• signals fullness

• reduces appetite

Memory trick: Leptin = full

Hunger hormones

Relationship

Ghrelin and leptin work in opposite directions.

• Ghrelin → hunger

• Leptin → fullness

Too much hormone exposure causes:

• Downregulation

• Meaning:

  • fewer receptors

  • body becomes less sensitive

Hormone tolerance

Example:

• leptin resistance

• caffeine tolerance