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Chapter 45

Chapter 45. Hormones and the Endocrine System. Tissue Communication. Extracellular animals have multiple levels of tissue organization. Communication is essential to maintain homeostasis. Endotherms vs ectotherms Bioregulators are used.

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Chapter 45

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  1. Chapter 45 Hormones and the Endocrine System

  2. Tissue Communication • Extracellular animals have multiple levels of tissue organization. • Communication is essential to maintain homeostasis. • Endotherms vs ectotherms • Bioregulators are used.

  3. The thermostat function of the hypothalamus and feedback mechanisms in human thermoregulation

  4. Chemical Signals • Used for tissue communication • Secreted chemical signals include • Local regulators (travel short distances via diffusion) • Neurotransmitters (nervous or endocrine communication) • Hormones (secreted into bloodstream, travel long distances) • Neurohormones (nerves that secrete hormones)

  5. Types of Cellular Action • __________ – impacting yourself. • __________– impacting your neighbors. • __________– impacting the next nerve in sequence. Short distance, quick communication. • __________– chemical secreted into blood stream. Impacts distant targets, longer lasting communication. • __________– neurons secrete hormones into bloodstream.

  6. Fig. 45-2 Blood vessel Response (a) Endocrine signaling Response (b) Paracrine signaling Response (c) Autocrine signaling Synapse Neuron Response (d) Synaptic signaling Neurosecretory cell Blood vessel Response (e) Neuroendocrine signaling

  7. Integration of Systems • Hormones impact the body through interrelationships of the __________ system and the __________ system. • The endocrine system secretes hormones that coordinate __________ , but longer-acting responses including reproduction, development, energy metabolism, growth, and behavior. • The nervous system conveys __________ electrical signals along specialized cells called neurons; these signals regulate other cells. • NOTE: Some neurons can secrete hormones…

  8. Neurotransmitters • Neurons (nerve cells) contact target cells at __________ . • At synapses, neurons secrete chemical signals called __________ that diffuse a short distance to bind to receptors on the target cell. • Neurotransmitters play a role in sensation, memory, cognition, and movement. • Many neurotransmitters can also serve as __________ . • Example: Epinephrine (__________ ) during ‘fight or flight’ response Synapse Neuron Response

  9. The Body’s Long-Distance Regulators • Animal __________ are chemical signals that are secreted into the circulatory system and communicate regulatory messages within the body. • Hormones mediate responses to environmental stimuli and regulate growth, development, and reproduction. • Stimuli can include: • Change in __________ • Another __________ • __________ impulses • __________ cues

  10. Neurohormones • Nerves that secrete hormones into the __________ . • Have long-lasting effects at distant targets. • Can store hormones (weird) • Examples: hypothalamic hormones, oxytocin, anti-diuretic hormone Neurosecretory cell Blood vessel Response

  11. How Hormones Work… • Three part system: • 1. Hormone is secreted • 2. Travels to distant targets via bloodstream • 3. Bind at specific target cells and cause a specific response • Endocrine glands are: • Ductless glands, secretory cells • Well vascularized • Range in size from individual cells to entire organs • Secretion can be turned off or amplified via feedback loops

  12. Feedback Mechanisms: Negative • The goal is to get back to the ‘norm’. • Something in the body needs to be amended hormone secreted from endocrine tissue travels to target tissue target response deals with situation, levels rise, etc. and shuts down further hormone secretion from endocrine tissue.

  13. Fig. 45-12-2 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. STIMULUS: Blood glucose level rises. Blood glucose level declines. Homeostasis: Blood glucose level (about 90 mg/100 mL)

  14. Feedback Mechanisms: Positive • The goal is to bring about ‘change’ • Endocrine tissue secretes hormone  hormone impacts target tissue, elicits response causes greater production of original endocrine tissue

  15. Fig. 45-16 Pathway Example Stimulus Suckling + Sensoryneuron Hypothalamus/posterior pituitary Neurosecretorycell Posterior pituitarysecretes oxytocin ( ) Positive feedback Bloodvessel Smooth muscle inbreasts Targetcells Response Milk release

  16. Fig. 45-10 Major endocrine glands: Hypothalamus Pineal gland Pituitary gland Organs containing endocrine cells: Thyroid gland Thymus Parathyroid glands Heart Liver Adrenal glands Stomach Pancreas Kidney Testes Small intestine Kidney Ovaries

  17. A few hormones…

  18. and a few more…

  19. Let’s simplify a bit…Chemical Classes of Hormones • Three major classes of molecules function as hormones in vertebrates: • __________(proteins and peptides) • Amines derived from __________ • __________ hormones

  20. Protein (or peptide) Hormones • Made from proteins (hydrophilic) • 2 categories: • Monoamines-made from one amino acid (lots of neurotransmitters, such as epinephrine) • Polypeptides-made from multiple amino acids. Examples: Growth Hormone, Insulin • Bind to membrane-bound receptors, use intracellular second messengers for response • Can bring about a quick response • Secreted from: • Pituitary • Pancreas • Parathyroid

  21. Made from lipids All are derived from cholesterol Made within: a. Gonads (testosterone, estrogen) b. Adrenals (cortisol, aldosterone) c. Brain (???) Bind to intracellular receptors Influence gene formation Impacts: Metabolism Gamete formation Stress response Growth Sex characteristics Behavior Steroid Hormones

  22. Coordination of Endocrine and Nervous Systems in Vertebrates • The hypothalamus receives information from the nervous system and initiates responses through the endocrine system. • It turns neural input into hormonal output through neurohormone secretions. • Examples: • Gonadotropin releasing hormone (GnRH) • Thyrotropin releasing hormone (TRH) • Attached to the hypothalamus is the pituitary gland composed of the anterior pituitary and posterior pituitary. • Together, these structures regulate lots of hormonal processes.

  23. Fig. 45-14 Cerebrum Thalamus Pineal gland Hypothalamus Cerebellum Pituitary gland Spinal cord Hypothalamus Posterior pituitary Anterior pituitary

  24. Anterior Pituitary • The anterior pituitary makes and releases peptide hormones into the bloodstream under regulation of the hypothalamus. • The anterior pituitary releases a new hormone in response to having received one by the hypothalamus. • These hormones impact a variety of targets. • Examples: • Follicle stimulating hormone (FSH) • Luteinizing hormone (LH) • Adrenocorticotropic hormone (ACTH)

  25. Posterior Pituitary Hormones • The posterior pituitary stores and secretes hormones that are made in the hypothalamus. These are neurohormones. • Two hormones released from the posterior pituitary act directly on nonendocrine tissues. • Oxytocin (OT) induces uterine contractions and the release of milk • Antidiuretic hormone (ADH) enhances water reabsorption in the kidneys

  26. Fig. 45-15 Hypothalamus Neurosecretorycells of thehypothalamus Axon Posterior pituitary Anterior pituitary HORMONE Oxytocin ADH TARGET Kidney tubules Mammary glands,uterine muscles

  27. Some examples: Endocrine GlandWhat it does… Pineal gland Serves as biological clock Thyroid Regulates metabolism Parathyroid Calcium regulation Adrenals Stress coping, ion regulation Pancreas (certain cells) Glucose regulation Gonads Gamete formation, behavior Plus many, many, many more…..

  28. A practical application:Diabetes mellitus • Diabetes mellitus is perhaps the best-known endocrine disorder. • It is caused by a deficiency of insulin (Type I) or a decreased response to insulin in target tissues (Type II). • Type I = usually genetic • Type II = lifestyle induced, some genetic influence • It is marked by elevated blood glucose levels. • Used to be assessed through urine tasting (yuck!)

  29. Insulin and Glucagon: Control of Blood Glucose • Diabetes results in the inability to effectively regulate glucose levels. • Insulin and glucagon are antagonistic hormones that help maintain glucose homeostasis. • The pancreas has clusters of endocrine cells called islets of Langerhans with alpha cells that produce glucagon and beta cells that produce insulin.

  30. Target Tissues for Insulin and Glucagon • Insulin reduces blood glucose levels by: • Promoting the cellular uptake of glucose • Slowing glycogen breakdown in the liver • Promoting fat storage • Glucagon increases blood glucose levels by: • Stimulating conversion of glycogen to glucose in the liver • Stimulating breakdown of fat and protein into glucose

  31. Fig. 45-12-5 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. STIMULUS: Blood glucose level rises. Blood glucose level declines. Homeostasis: Blood glucose level (about 90 mg/100 mL) STIMULUS: Blood glucose level falls. Blood glucose level rises. Alpha cells of pancreas release glucagon. Liverbreaks downglycogen andreleases glucose. Glucagon

  32. Other Applications: Gamete Production Birth Control Secondary Sex Characteristics Aggression

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