Endocrine System

What does the Endocrine System do?

It secretes hormones directly into the bloodstream to maintain homeostasis

Hormones

Chemical messengers that regulate many bodily functions. A specific hormone must bind to a specific receptor in order to create a response.

Endocrine cells are located in…

gland or gland like structure

Target cells in endocrine system are…

Specific cells that respond to hormones

The main endocrine organs are:

• Pituitary gland - brain

• Hypothalamus - brain

• Thyroid gland - neck

• Adrenal glands - on top of kidneys

• Pineal gland - brain

• Parathyroid glands - neck; posterior part of thyroid

• Pancreas - abdomen

Organs with secondary endocrine functions:

• heart

• thymus

• adipose tissue

• digestive tract

• kidneys

• gonads

  • testes

  • ovaries

Hypothalamus secretes which hormones

Antidiuretic hormone (ADH), oxytocin (OXT), and regulatory hormones

Pituitary Gland secretes …

from Anterior lobe (ACTH, TSH, GH, PRL, FSH, and MSH)

from Posterior lobe (Release of OXT and ADH)

Thyroid Gland secretes…

Thyroxine (T4)

Triiodothyronine (T3)

Calcitonin (CT)

Adrenal Glands secretes…

from Medulla

• Epinephrine (E)

• Norepinephrine (NE)

from Cortex

• Cortisol, corticosterone, aldosterone, androgens

Pancreatic Islets secretes…

Insulin, glucagon

Pineal Gland secretes…

Melatonin

Parathyroid Glands (on posterior surface of thyroid gland) secretes…

parathyroid hormone (PTH)

Hypothalamus is the key endocrine organ that serves as the …

link between the neural and endocrine systems

Hypothalamus integrates neural and endocrine activities via 3 mechanisms …

1. Acts as an endocrine organ

2. secretes regulatory hormones

3. contains automatic nervous system centers

Heart secretes…

atrial natriuretic peptide (ANP)

brain natriuretic peptide (BNP)

Thymus (undergoes atrophy during adulthood) secretes …

Thymosins

Adipose Tissue secretes…

Leptin, Resistin

Digestive tract secretes…

Numerous hormones

Kidneys secrete…

Erythropoietin (EPO)

Calcitriol

Gonads secrete…

Testes (males)

• Androgens (esp testosterone), inhibin

Ovaries (females)

• estrogens, progesterone, inhibit

Preganglionic neurons start in the

hypothalamus synapse on the adrenal medulla

Hypothalamus produces

oxytocin and antidiuretic hormone (ADH). These hormones travel thru hypothalamic neurons (their axons). Eventually, oxytocin and ADH are released by the posterior part of the pituitary gland.

Anterior Lobe of Pituitary Gland consists of 5 diff cell types:

• Thyrotropes — thyroid gland

• Corticotropes — adrenal cortex

• Gonadotropes — reproductive organs

• lactotropes — mammary glands

• Somatotropes — growth of the body

Posterior pituitary gland is also known as:

Neurohypophysis

Anterior pituitary gland is also known as

adenohypophysis

Main organs released by posterior pituitary gland are:

Oxytocin and ADH

ADH targets what organ and what does it do

Kidneys; it works to reabsorb water (water retention). By reabsorbing water, we can increase blood volume and blood pressure

Oxytocin targets what

mammary glands and uterus in females. This causes milk ejection in the mammary gland; it causes uterine wall contraction. In males, oxytocin acts on the prostate gland and ductus deferens. This leads to contractions of both of these structures

Where is the thyroid gland in the body

It sits in the inferior neck just in front of the trachea. It secretes T3 and T4 —- these hormones influence metabolism in the body.

Calcitonin is also releases by thyroid. It works on lower blood calcium levels.

Where are parathyroid glands in the body

They lie on the posterior surface of the thyroid gland. there are 4 nodules. Parathyroid glands release parathyroid hormone which works to increase blood calcium levels

Where are adrenal glands

They sit on top of the kidneys. They have a pyramidal shape and sit on the superior surface of ur kidneys

Adrenal gland has 2 main parts:

• adrenal cortex (outer portion)

• Adrenal medulla (inner portion)

Adrenal medulla secretes

norepinephrine (noradrenaline) and epinephrine (adrenaline)

Adrenal cortex secretes several major hormones including:

• cortisol (works to increase blood sugar so that we have E to respond to internal and external stress)

• Aldosterone (this hormone helps promote water retention to increase blood volume and blood pressure)

• The androgens (these are sex hormones; this includes estrogen and testosterone)

where are pancreas located

in the abdomen. It sits behind (posterior) to the stomach.

Function of pancreas

it functions as both exocrine and endocrine gland.

Endocrine portion relies on bloodstream to move the hormones made by pancreas. The exocrine portion relies on the ducts within the pancreas to move its produce, mainly digestive enzymes.

Appearance of pancreas

The head of pancreas is tucked into the “U” shaped curve of the duodenum of the small intestine

Main hormones made by the pancreas are

glucagon and insulin.

glucagon works to increase blood sugar levels

insulin works to decrease blood sugar levels

Kidneys also work as …

secondary endocrine organs.

The kidney can secrete renin. Renin stimulates a series of steps that ultimately lead to production/release of aldosterone by the adrenal cortex. In this instance, renin is working to increase sodium and water retention.

Kidneys play a role in

regulating blood calcium levels. Whenever we have low blood calcium levels in the body, we need an

active form of vitamin D to stimulate our digestive tract to absorb more dietary calcium. In order for this to happen vitamin D needs to be converted from an inactive form into an active form. Our kidney cells perform this activation step. However, we need to keep in mind that the inactive form of vitamin D must be created from something. Exposure to sunlight plays a vital role here. An initial hormone is converted into the inactive vitamin D by sunlight. Go through the steps listed in the lecture slides.

The ultimate goal for all these steps is to increase blood calcium

Our kidneys release a hormone called

Erythropoietin (EPO) whenever we need to increase blood oxygen levels. EPO stimulates creation of more red blood cells so that we can carry more O2 in the body.