Chp.45: Hormones & the Endocrine System (review: Chp.11 Cell Communication) AP Bio 3/14/13

Remember: Why cells need to communicate: ◦ Coordinate activities in multicellular organisms ◦ Hormone actions ◦ Cell recognition ◦ To find mates (yeast cells) ◦ Turn pathways on/off ◦ apoptosis 2

Evolutionary ties of cell communication Cell-to-cell communication is everywhere in biological systems from Archaea and bacteria to multicellular organisms. The basic chemical processes of communication are shared across evolutionary lines of descent. Signal transduction is an excellent example 3

Signal Transduction Animation Click on this link to access the animation: /animations/signal_transduction/signal_ transduction.htm 4

Chemical Communication Outside the body Ex. Pheromones Ex. Quorum sensing Inside the body Short Distance Long Distance 5

Pheromones 6 Members of the same animal species sometimes communicate with pheromones, chemicals that are released into the environment. Pheromones serve many functions, including marking trails leading to food, defining territories, warning of predators, and attracting potential mates.

Quorum sensing Quorum sensing in bacteria – single celled bacteria monitor their environment by producing, releasing and detecting hormone- like molecules called autoinducers. 7

Chemical Communication Inside the body Short Distance Paracrine Example Prostaglandin Autocrine Example Interleukin Long Distance Hormones Example Insulin 8

Direct Contact Communication Ex. Plant cells communicate directly through openings called plasmodesmata. 9

Short Distance Communication Paracrine signals diffuse to and affect nearby cells ◦ Ex. Neurotransmitters ◦ Ex. Prostaglandins 10

Synapse Response Neuron Synaptic signaling Neurosecretory cell Blood vessel Neuroendocrine signaling

Autocrine signals These chemicals affect the same cells that release them. ◦ Ex. Interleukin-1 produced by monocytes and can bind to receptors on the same monocyte. ◦ Tumor cells reproduce uncontrollably because they self-stimulate cell division by making their own division signals. 12

Long Distance Communication Endocrine hormones via signal transduction pathway: 13

Hormones Endocrine glands produce hormones which are ◦ Chemical signals ◦ Transported in tissue fluids ◦ Detected only by target cells 14

Summary: 15

Communication Features Secreting cell - releases the signal Signal = chemical = ligand Receptor - accepts and temporarily joins with the ligand forming receptor/ligand complex Target cell – contains the receptor 16

Apply the features Insulin is secreted by beta cells of the pancreas. Once secreted, insulin travels around the body. When insulin docks with an integral protein on the membrane of a muscle cell, glucose can enter the cell. What is the secreting cell, the target cell, ligand, and the receptor? 17

Endocrine System The human endocrine system is composed of a collection of glands that secrete a variety of hormones. These chemicals use long distance communication to control the daily functioning of the cells of the body, maintain homeostasis, respond to environmental stimuli, and growth & development. 18

Endocrine System The endocrine system produces more than 30 different chemicals used by your body to and promote normal body function. This system contains 9 primary glands as well as endocrine cells found within major organs. The endocrine system is a ductless system that employs the circulatory system when delivering chemical signals over long distances. 19

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The Endocrine System works with the Nervous System Two systems coordinate communication throughout the body: the endocrine system and the nervous system. The endocrine system secretes hormones that communicate regulatory info throughout body. The nervous system uses neurons to transmit signals; these signals can regulate the release of hormones.

Table 45.1a

Table 45.1b

Figure Pathway Example Stimulus Cold Sensory neuron   Hypothalamus Neurosecretory cell Releasing hormone Blood vessel Anterior pituitary Tropic hormone Endocrine cell Hormone Target cells Response Negative feedback Hypothalamus secretes thyrotropin-releasing hormone (TRH). Anterior pituitary secretes thyroid-stimulating hormone (TSH, also known as thyrotropin). Thyroid gland secretes thyroid hormone (T 3 and T 4 ). Body tissues Increased cellular metabolism

The Process of Communication: Signal-Transduction Pathway Three stages of the Signal- Transduction Pathway 1. reception 2. transduction 3. response

Typical Signal Transduction Pathway

Ligand = Chemical Messenger Three major classes of molecules function as hormones in vertebrates (ligands) ◦ Polypeptides (proteins and peptides) ◦ Amines derived from amino acids ◦ Steroid hormones 27

Cellular Response Pathways Water- and lipid-soluble hormones differ in their paths through a body Water-soluble hormones are secreted by exocytosis, travel freely in the bloodstream, and bind to cell-surface receptors Lipid-soluble hormones diffuse across cell membranes, travel in the bloodstream bound to transport proteins, and diffuse through the membrane of target cells

Type of Receptor: Ex- G-protein linked ( Water soluble = polypeptides & amines, can’t pass cell membrane)

Type of Receptor: Intracellular Receptor (Lipid Soluble = Steroid Hormones, can pass cell membrane)

Lipid- soluble hormone SECRETORY CELL Water- soluble hormone VIA BLOOD Signal receptor TARGET CELL OR Cytoplasmic response Gene regulation (a) (b) Cytoplasmic response Gene regulation Signal receptor Transport protein NUCLEUS

Plasma membrane EXTRACELLULAR FLUID CYTOPLASM ReceptionTransduction Response Receptor Signaling molecule Activation of cellular response Relay molecules in a signal transduction pathway 3 2 1Recap

Multiple Effects of Hormones The same hormone may have different effects on target cells that have ◦ Different receptors for the hormone ◦ Different signal transduction pathways

The hormone epinephrine has multiple effects in mediating the body’s response to short-term stress Epinephrine binds to receptors on the plasma membrane of liver cells This triggers the release of messenger molecules that activate enzymes and result in the release of glucose into the bloodstream Multiple Effects of Hormones

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Different receptors Same receptors but different intracellular proteins (not shown) Different cellular responses Epinephrine  receptor  receptor  receptor Glycogen deposits Vessel dilates. Vessel constricts. Glycogen breaks down and glucose is released from cell. (a) Liver cell (b) Skeletal muscle blood vessel Intestinal blood vessel (c)

Insulin and Glucagon: Control of Blood Glucose Hormones work in pairs to maintain homeostasis. Insulin (decreases blood glucose) and glucagon (increases blood glucose) are antagonistic hormones that help maintain glucose homeostasis. The pancreas has clusters of endocrine cells called pancreatic islets with alpha cells that produce glucagon and beta cells that produce insulin.

Body cells take up more glucose. Insulin Beta cells of pancreas release insulin into the blood. Liver takes up glucose and stores it as glycogen. Blood glucose level declines. Blood glucose level rises. Homeostasis: Blood glucose level (70–110 mg/100mL) STIMULUS: Blood glucose level rises (for instance, after eating a carbohydrate-rich meal). Liver breaks down glycogen and releases glucose into the blood. Alpha cells of pancreas release glucagon into the blood. Glucagon STIMULUS: Blood glucose level falls (for instance, after skipping a meal). Figure 45.13

Out of Balance: Diabetes Mellitus Diabetes mellitus is perhaps the best-known endocrine disorder. It is caused by a deficiency of insulin or a decreased response to insulin in target tissues. It is marked by elevated blood glucose levels.

Type 1 diabetes mellitus (insulin-dependent) is an autoimmune disorder in which the immune system destroys pancreatic beta cells. Type 2 diabetes mellitus (non-insulin-dependent) involves insulin deficiency or reduced response of target cells due to change in insulin receptors. Out of Balance: Diabetes Mellitus

Insulin & Glucose Regulation

Endocrine System Summary Assignment Copy the general Endocrine System Negative Feedback Summary (Fig.13.10) pg.479 Then, create your own feedback summary for any other Hormone of the Endocrine System ***Bring Books MONDAY***