1. Chemical Communication
The Endocrine System
Chemical Communication

2. The Endocrine System
Endocrine system: secretes hormones in the human body to maintain homeostasis
Major glands: pituitary, thyroid, parathyroid, adrenal, pancreas, pineal, thymus, testes, ovaries

4. Hormones
Hormone: a chemical messenger that carries a signal from an endocrine gland to regulate the function of a target cell
2 Types:
Steroid hormones: made from cholesterol (are lipids), water insoluble, diffuse easily into cell
Non-steroid hormones: made from amino acids (are proteins), bind to receptors on cell membrane
Hormone secretion is controlled by negative feedback mechanisms

5. Pituitary Gland Hormone release is controlled by the hypothalamus
2 Parts: anterior and posterior pituitary
Anterior Pituitary Hormones:
Growth Hormone (GH): regulates cell division
Prolactin (PRL): regulates milk production in females after childbirth
Follicle-stimulating hormone (FSH) and luteinizing hormone (LH): act on testes and ovaries

6. Pituitary Gland, Cont’d
Posterior Pituitary hormones:
Antidiuretic hormone (ADH): decreases urine production; too little water in the bloodstream triggers release and less urine, too much water stops release and more urine is produced
Oxytocin (OT): contracts smooth muscle in walls of uterus; stimulates uterine contractions in childbirth (Positive Feedback Loop!)

7. Thyroid Gland Action is controlled by hormones in pituitary gland
Important Hormones:
Thyroxine: regulates metabolism of carbohydrates, lipids, and proteins; Determines basal metabolic rate (BMR)- how many calories you burn at rest
Calcitonin: regulates concentration of blood calcium

8. Parathyroid Glands 4 located on thyroid gland
Secretes parathyroid hormone (PTH)
PTH regulates blood calcium and blood phosphate concentration

9. Adrenal Glands Action controlled by hormones in pituitary gland
Epinephrine (adrenalin) and norepinephrine: increase breathing rate, heart rate, blood pressure, blood glucose level
Aldosterone: regulates Na+ and K+ levels in body
Cortisol: affects glucose metabolism

10. Pancreas
Insulin: lowers blood glucose levels, stimulates products of glycogen (sugar storage)
Glucagon: stimulates breakdown of glycogen, elevates blood glucose levels
Diabetes: body loses ability to regulate blood glucose levels
Type 1: immune system destroys cells in pancreas, no more insulin produced
Type 2: pancreas produces insulin, body cells don’t recognize it.

11. Other Glands Pineal Gland Thymus Gland
Melatonin: sleep hormone, released in response to darkness, enables body to distinguish day and night
Thymus Gland
Thymosins: affect production of white blood cells

12. Connecting Electrical and chemical communication in your body
Feedback Systems
Connecting Electrical and chemical communication in your body

13. What is Feedback?
Feedback is the process in which part of the output of a system is returned to its input in order to regulate its further output.
Your body has POSITIVE and NEGATIVE feedback systems to maintain homeostasis.

14. Negative Feedback
Negative feedback occurs when the output of a system acts to oppose changes to the input of the system.
A thermostat is an example of a negative feedback system.

15. Heater turns off Heater turns on AC turns off AC turns on
Room temp increases
Set point
is reached
Heater turns on
Heater turns off
Room temp is below the setpoint
Room temp is above the setpoint
Goal: Maintain Stable Temperature!
Set point
is reached
Room temp decreases
AC turns off
AC turns on

16. Negative Feedback in Biology
Negative feedback also regulates many systems in organisms.
The endocrine system has many examples!
This diagram shows a negative feedback loop for stress hormones.
Areas of negative feedback are indicated with a minus sign, (-).

17. Endocrine System <3 Nervous System!
The brain continuously sends signals to the endocrine glands to secrete and release hormones and the glands, in turn, send feedback to the nervous system.
The hypothalamus in the brain is the master switch that sends signals to the pituitary gland which can release up to eight hormones into the bloodstream.
The hormone travels to its target organ and usually results in the release of another hormone into the bloodstream.

18. Endocrine System
The hypothalamus then detects the rising hormone levels from the target organ and decreases the release of hormones from the pituitary which results in a decrease in hormone release from the target organ.
The process of maintaining normal body function through negative feedback mechanisms is called homeostasis.

19. Negative Feedback Example: Glucose and Insulin
Pancreas
Glucose intake occurs during digestion of food that is needed for energy expenditure to perform routine physical activities.
The pancreas is the key organ that regulates the glucose levels in body by secreting two hormones, insulin and glucagon.
The liver also helps to store the excess glucose in form of glycogen to be utilized later.
Liver

20. Glucose and Insulin Negative Feedback Loop
Eating cake
Increases Glucose Levels
(-)
CYCLE 1
Stimulates β cells of pancreas to secrete insulin
Lowers Blood Glucose levels
Insulin stimulates the cells to take up glucose from the blood.

21. CYCLE 2 Low Blood Glucose Levels Glucagon is released
(-)
Stimulated Alpha Cells in Pancreas
High blood glucose levels and Cycle 1 continues
Glucagon is released
Glucagon stimulates liver cells to release glucose into the blood

22. Glucose and Insulin Negative Feedback Loop
Two primary Hormones
The opposite actions of these two hormones, insulin and glucagon, helps to maintain normal blood sugar levels in the body hence maintain homeostasis of the body.
Insulin
Glucagon
Lowers Blood Glucose Levels
Raises Blood Glucose
Levels

23. Feedback Check-up....
What is a feedback and an example of a negative AND positive system?
What is the endocrine system and why is it important?
Define homeostasis and how normal body function is maintained with feedback mechanisms.

24. Kidneys and Water Regulation
The kidneys play a key role in maintaining water regulation.
Renal Cortex
Renal Medulla

25. Kidney and Water Regulation
The nephron is the most important functional part of the kidney.
It filters nutrients like salts and amino acids in the Bowman’s capsule into ascending loop and filters the urine.

26. Kidney and Water Regulation
Anti-Diuretic Hormone, ADH (also called vasopressin), is secreted by the pituitary gland and acts on the nephron to conserve water and regulate the tonicity of body fluids.
Anti-
Diuretic
Hormone
ADH acts on Nephron to reabsorb water and decrease blood osmolality (saltiness)

27. Your Turn! ADH Nephron Distal Collecting Tubules Osmoreceptors
Hypothalamus
Pituitary Gland
Concentrated Urine
Dilute Urine
Permeability
Draw a Negative Feedback loop that demonstrates how your kidneys, blood, and brain work together to regulate the amount of water in your body. Include these terms:

28. ADH regulated water conservation in kidneys
Excess water in the blood
Less water in the blood
Stimulates osmoreceptors in hypothalamus to send signals to the pituitary gland
Stimulates osmoreceptors in hypothalamus to send signals to the pituitary gland
Pituitary glands secretes high levels of ADH
Pituitary glands secretes low levels of ADH
Less ADH makes the tubules less permeable and less water is reabsorbed back into the bloodstream (urine is dilute).
ADH makes the tubules more permeable and more water is reabsorbed back into the bloodstream (urine is concentrated).

29. ADH regulated water conservation in kidneys
Osmoregulators send negative feedback to the hypothalamus about the concentration of water in the bloodstream.
The hypothalamus then stimulates the pituitary glands to secrete high or low concentrations of anti- diuretic hormone.
ADH then makes the tubules more or less permeable and hence, maintains water and electrolyte homeostasis.

30. Positive Feedback Loops
A positive feedback loop occurs when the output of a system acts to enhance the changes to the input of the system.
One example of a biological positive feedback loop is the onset of contractions in childbirth.
When a contraction occurs, the hormone oxytocin is released into the body, which stimulates further contractions.
This results in contractions increasing in amplitude and frequency.

31. Positive Feedback Another example is blood clotting.
The loop is initiated when injured tissue releases signal chemicals that activate platelets in the blood.
An activated platelet releases chemicals to activate more platelets, causing a rapid cascade and the formation of a blood clot.
Lactation involves positive feedback so that the more the baby suckles, the more milk is produced.

32. Positive Feedback
In most cases, once the purpose of the feedback loop is completed, counter-signals are released that suppress or break the loop.
Childbirth contractions stop when the baby is out of the mother's body.
Chemicals break down the blood clot.
Lactation stops when the baby no longer nurses.