Endocrine - Lec

* Influences metabolic activity by hormones.
* Hormones travel through the blood and regulate the function of other cells.
* The lag period can be seconds or days.

Endocrine System

* This system regulates the activity of muscles and glands via electrochemical impulses.
* The response is \n within milliseconds.

Nervous System

* Reproduction
* Growth and development
* Maintenance of electrolytes, water, and \n nutrient balance of blood
* Regulation of cellular metabolism and energy balance
* Mobilization of body defense

Endocrine System - Processes

The scientific study of hormones and endocrine organs

Endocrinology

* Produce non-hormonal substances.
* They have ducts that secrete these substances \n on membrane surface

Exocrine glands

* Produce hormones and lack ducts.
* They release their hormones into the surrounding tissue fluid, which is then picked up by capillaries and enters the bloodstream.

Endocrine glands

Exocrine - Image

Endocrine - Image

Melatonin

Pineal gland (Epiphysis)

Pineal gland (Epiphysis) - Image

* Free T4
* Free T3
* Calcitonin

Thyroid gland

Thyroid gland - Image

* Cortisol
* Aldosterone
* DHEA-SO4

Adrenal glands

Adrenal glands - Image

* Estradiol
* Progesterone

Ovaries

Ovaries - Image

* Growth Hormone (GH)
* ACTH
* TSH
* FSH

Pituitary gland (Pt. 1)

* LH
* Prolactin
* Antidiuretic hormone (ADH)

Pituitary gland (Pt. 2)

Pituitary gland - Image

Parathyroid hormone (PTH)

Parathyroid glands

Parathyroid glands - Image

Thymus gland - Image

* Insulin
* Glucagon

Pancreas

Pancreas - Image

* Testosterone
* Testosterone Free

Testes

Testes - Image

The chemical structure of a hormone…..

Determines how it acts

* Amino acid based
* Steroid based

Hormone Chemical Structures

* Most hormones are based on amino acids
* Molecular size varies
* These hormones are water soluble and can not cross the plasma membrane of the cell (with the exception of thyroid hormone)

Amino acid based hormones

* Synthesized from cholesterol
* Only gonadal and adrenocortical hormones are steroids
* These hormones are all lipid soluble and can enter the plasma membrane

Steroid based hormones

* All major hormones circulate to \n virtually all tissues.
* But hormones influence the activity \n of cells tissues that have receptors \n for it.

Hormone communication with cells

Ligand - Image

Receptor - Image

* Are proteins that recognize and bind to a specific \n hormone.
* Can be on the plasma membrane (Extracellular) or inside (Intracellular) the cell

Hormone receptors

Some hormones can not enter…..

The Plasma Membrane

* Amino acid-based/water-soluble hormones cannot enter the plasma membrane (thyroid hormone is the \n exception)
* They require extracellular receptors
* The receptors are linked to a G-protein and other molecules that lead to a cascade of biochemical events

Some Hormone Can Not Enter The Plasma Membrane

Entering plasma membrane - Image


1. Nonsteroid hormone
2. Binding with receptor
3. Activated enzyme
4. Secondary messenger
5. Effect on cellular function

Most amino acid-based hormones exert their signaling effects through intracellular secondary messengers generated when a hormone binds to a \n receptor in the plasma membrane

Secondary Messenger Systems (Pt. 1)

* Cyclic AMP Signaling Mechanisms
* PIP2-Calcium Signaling Mechanisms

Secondary Messenger Systems (Pt. 2)

1. Hormone (first messenger) binds to receptor
2. Receptor activates G Protein
3. G Protein activates adenylate cyclase
4. Adenylate cyclase converts ATP to cyclic AMP
5. Cyclic AMP activates protein kinases & protein kinase causes change inside the cell

The Cyclic AMP Signaling Mechanism

The Cyclic AMP Signaling Mechanism -Step 1 - Image

The Cyclic AMP Signaling Mechanism -Step 2 - Image

The Cyclic AMP Signaling Mechanism -Step 3 - Image

The Cyclic AMP Signaling Mechanism -Step 4 - Image

The Cyclic AMP Signaling Mechanism -Step 5 - Image

1. Hormone binds to receptor
2. Receptor activates G-protein
3. G-protein activates phospholipase C
4. Phospholipase make PIP2
5. PIP2 activate DAG and IP3
6. DAG activates protein kinase \n And/or P3 Releases calcium
7. Calcium binds to calmodulin and activates

protein kinase

PIP2-Calcium Signaling Mechanisms

* Steroid-based/lipid-soluble hormones are able \n to diffuse through the plasma membrane
* There, they bind to and activate intracellular \n receptor
* The activated hormone-receptor complex then \n makes its way to chromatin and binds to a \n specific DNA region
* This binding will “turn on” a gene and allow \n transcription of DNA to produce mRNA
* mRNA is translated to produce specific proteins.

Intracellular Receptors and Direct Gene Activation

Intracellular Receptors and Direct Gene Activation - Step 1 - Image

Intracellular Receptors and Direct Gene Activation - Step 2 - Image

Intracellular Receptors and Direct Gene Activation - Step 3 - Image

Intracellular Receptors and Direct Gene Activation - Step 4 - Image

Intracellular Receptors and Direct Gene Activation - Step 5 - Image

* Three types of stimuli trigger endocrine glands \n to manufacture and release hormones.
* Some endocrine glands respond to more than \n one.

(3) Types of stimuli cause hormone release

* Humoral
* Neural
* Hormonal stimuli

Three types of stimuli trigger endocrine glands \n to manufacture and release hormones.

* Some endocrine glands secrete their hormones \n in direct response to changing blood levels of \n certain critical ions and nutrients.
* Humoral stimuli are the simplest endocrine \n controls.

Humoral Stimuli

* Insulin released in response to high blood glucose
* Parathyroid hormone released in response to low \n calcium in blood

Humoral Stimuli - Examples

Humoral Stimuli - Image

In a few cases nerve fibers stimulate hormone release

Neural Stimuli

During situations of stress the sympathetic nervous \n system stimulates adrenal medulla to release \n norepinephrine and epinephrine

Neural Stimuli - Example

Neural Stimuli - Image

Many endocrine glands release their hormones \n in response to hormones produced by other endocrine organs

Hormonal Stimuli

* Hormones produced by the hypothalamus regulates the secretion of most anterior pituitary hormones; and anterior pituitary hormones stimulate other glands to secrete their hormones.
* Secretion of hormones is regulated by negative feedback

Hormonal Stimuli - Example

Hormonal Stimuli - Image

* Multiple hormones may act on the same target \n cells at the same time.
* These are three types of hormonal interactions.

Interactions of Hormones on Target Cells

* Permissiveness
* Synergism
* Antagonism

Types (3) of hormonal interactions

This is a situation in which one hormone can not \n exert its full effects without another hormone

Permissiveness

* Reproductive hormones regulate regulate the development of the reproductive system.
* However, thyroid hormone is also necessary for normal timely development of reproductive structures.
* Lack of thyroid hormone delays reproductive development

Permissiveness - Example

In this situation more than one hormone \n produce the same effects at the target cells and \n their combined effects are amplified

Synergism

* Both glucagon and epinephrine cause the \n liver to release glucose to the blood.
* When both hormones are secreted at the same time, the amount of glucose released is about 150% of what is released if each hormone acts independently.

Synergism - Example

This is when one hormone opposes the action of another

Antagonism

Insulin, which lowers blood glucose levels, is antagonized by glucagon, which raises blood glucose levels.

Antagonism - Example

Antagonism - Image

The Pituitary gland is also known as……

Hypophysis

• Secretes at least 8 hormones

• Shape of a pea

• In humans, the pituitary gland has two lobes

Pituitary Gland (Pt. 1)

• Anterior Pituitary(Adenohypophysis)

• Posterior Pituitary(Neurohypophysis)

Pituitary Gland (Pt. 2)

Anterior Pituitary(Adenohypophysis) tissue is….

Glandular tissue

Posterior Pituitary(Neurohypophysis) tissue is…..

Mostly neural tissue

• This lobe is a hormone storage area and not a true endocrine gland

• Neurohormones released
  -Oxytocin
  -Antidiuretic Hormone (ADH)

Posterior Pituitary

Pars nervosa (neurohypophysis) - Image

Pars intermedia - Image

Pars distalis (adenohypophysis) - Image

Image

1. A

2. B

Pars nervosa - Image

Pars intermedia - Image

Posterior Pituitary - Image

1. Hypothalamic neurons synthesize oxytocin
   and ADH

2. Oxytocin and ADH are transported along the
   hypothalamic-hypophyseal tract to the posterior pituitary

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

4. Oxytocin and ADH are released into the blood when hypothalamic neurons fire

Relationship between the posterior pituitary and the hypothalamus

Image

1. Hypothalamus

2. Inferior hypophyseal artery

3. Oxytocin & ADH

4. Posterior lobe of pituitary

5. Axon terminals

Image

6. Hypothalamic-hypophyseal tract

7. Infundibulum (connecting stalk)

8. Optic chiasma

9. Supraoptic nucleus

10. Paraventricular nucleus

• Amino acid based

• Stimulates uterine contractions

• Significantly high amounts are released
  during childbirth

Oxytocin (Pt. 1)

• Acts as a hormonal trigger for milk
  ejection

• Oxytocin also acts as a neurotransmitter
  in the brain. This hormone is involved with
  sexual and affection behavior.

Oxytocin (Pt. 2)

• Oxytocin deficiency

• Oxytocin excess

Endocrine Disorders - Oxytocin

• Non-progressive labor

• Inability to breast-feed

• Distrust

• Lack of bonding with offspring

Oxytocin deficiency

• Too trusting?

• Intense sexual desire?

Oxytocin excess

• Amino acid based

• A hormone that inhibits or prevents urine
  formation

ADH (Pt. 1)

• It helps the body avoid dehydration

• It helps maintain water balance in the body

• Target the kidneys

ADH (Pt. 2)

• If the solute concentration is low

  • ADH has not released

  • Urine Volume is increased, allowing water loss

• Alcohol inhibits ADH release and causes elevated urine output

Antidiuretic Hormone (ADH)

• Diabetes Insipidus

• Syndrome of Inappropriate ADH Secretion (SIADH)

Endocrine Disorders - ADH

• ADH deficiency—huge output of
  urine (5 to 10 gallons per day)

• Intense thirst; dehydration

Diabetes Insipidus

• ADH hypersecretion (after
  neurosurgery, trauma, or secreted
  by cancer cells)—decreased urine
  production

• Over-hydration

Syndrome of Inappropriate ADH Secretion (SIADH)