HOMEOSTASIS, ENDOCRINE SYSTEM, THE PANCREAS & THE

NEPHRONAP Biology—Unit 9

Homeostasis

Definition: maintaining a stable internal environment. Fluctuates within the bounds of “normal.”

Feedback mechanisms to control homeostasis

Homeostasis

Positive Feedback—an increase in a variable triggers a mechanism that amplifies the variable

Negative Feedback—an increase in a variable triggers a response that counteracts the initial change

Homeostasis

Thermoregulation—regulation of body temperature

By what feedback loop do animals regulate body temperature, positive or negative?

What are some adaptations that help organisms regulate their temperature?

Homeostasis

Cell Communication Review! Define the following types of

INTERCELLULAR COMMUNICATION: Endocrine Signaling

Paracrine

Synaptic

Cell Communication Review!

Cell Communication Review!!!

Endocrine System

Endocrine System—sum of all the cells and tissues that secrete hormones

Endocrine Glands—secrete hormones directly into body fluids. They do not have ducts.

Hormones—chemical signals that cause a response in a target cell. Water-Soluble (Hydrophilic)—cannot go through

plasma membrane, so bind to receptor proteins Lipid-Soluble (Hydrophobic)—diffuse through

plasma membrane and bind to intracellular receptor

Endocrine SystemS

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Endocrine System One hormone can have different effects

on different target cells.

Endocrine System—Pancreas

Gutsman

Endocrine System—PANCREAS

Both an Endocrine and Exocrine gland Endocrine—_________________________________

(i.e. pituitary, thyroid, etc.)

Exocrine—secretes “stuff” that goes into a duct

(i.e. liver, salivary gland)

Pancreas

Exocrine—Secretes Pancreatic Juice through the Pancreatic Duct to the Small Intestines

Pancreatic Juice Contains— Bicarbonate—buffers stomach acid Digestive Enzymes

Endocrine System—Pancreas Endocrine—regulate blood glucose by

negative feedback

Beta cells—make Insulin Insulin tells cells to take in sugar Increased insulin causes decrease in blood sugar

Alpha Cells—make Glucagon Glucagon tells cells to convert glycogen to glucose Increased glucagon causes increase in blood sugar

Endocrine System—Pancreas

Endocrine System—Pancreas

Steps: Eat—Blood sugar increases Insulin increases—cells take in glucose which

decreases blood sugar Liver converts excess glucose to glycogen Blood sugar decreases, and so insulin decreases As blood sugar begins to dip, glucagon increases

and tells liver to convert glycogen to glucose Blood glucose increases

Endocrine System—Pancreas Homeostasis: Regulating Blood Sugar Mo

vie

Draw a diagram of the feedback system that controls blood sugar levels!

Endocrine System—Childbirth Prostagladins (local regulators) and

Estradiol and Oxytocin (hormones) regulate the contractions of the uterus

Oxytocin forms a positive feedback loop—uterine contractions stimulate the secretion of more oxytocin

Endocrine System—Childbirth

Endocrine—Osmoregulation & Kidneys

Kidneys—filter blood; maintain water balance Parts of Nephron—functional unit of kidney

Glomerulus / Bowman’s Capsule Proximal & Distal Convoluted Tubules Loop of Henle Collecting Duct

Processes Filtration Reabsorption Secretion Excretion

Endocrine—Osmoregulation & Kidneys

Antidiuretic Hormone (ADH) Produced by hypothalamus Receptor cells in hypothalamus sense osmolarity

in the blood (more solutes/salts = higher osmolarity)

If osmolarity increases, ADH is released ADH binds to receptor proteins on the cells in the

collecting duct of nephron This increases permeability of these cells for

water—causing water to be reabsorbed into the blood

Result = more water in blood = decrease in osmolarity

ADH—Positive or Negative?

Endocrine—Osmoregulation, Blood Pressure, and Kidneys

Aldosterone Produced in Adrenal Glands Stimulated by cascade of events between

renin and angiotensin when blood pressure and / or blood volume decreases in artioles that supply blood to glomerulus

Aldosterone acts on distal tubule and collecting duct

Increases reabsorption of Na+ and water = increase in blood volume = increase in blood pressure

Aldosterone—Positive or Negative?