hormones and the endocrine system chapter 45

HORMONES AND THE ENDOCRINE SYSTEM

CHAPTER 45

Animal hormones are chemical signals that are secreted into the circulatory system and communicate regulatory messages within the body

Hormones reach all parts of the body, but only target cells have receptors for that hormone

OVERVIEW: THE BODY’S LONG-DISTANCE REGULATORS

The endocrine system secretes hormones that coordinate slower but longer-acting responses including reproduction, development, energy metabolism, growth, and behavior

The nervous system conveys high-speed electrical signals along specialized cells called neurons; these signals regulate other cells

COORDINATION BETWEEN ENDOCRINE AND NERVOUS SYSTEMS

Essential knowledge 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling.Essential knowledge 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling.

Intercellular CommunicationThe ways that signals are transmitted between animal cells are classified by two criteria

The type of secreting cell The route taken by the signal in reaching its

target

CONCEPT 45.1: HORMONES AND OTHER SIGNALING MOLECULES BIND TO TARGET RECEPTORS,

TRIGGERING SPECIFIC RESPONSE PATHWAYS

Endocrine cells that release specific signaling molecules, which can travel long distances through the blood to reach all parts of the body.

Maintains homeostasis, mediates responses to stimuli, regulates growth and development

ENDOCRINE SIGNALING

Essential knowledge 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. c. Signals released by one cell type can travel long distances to target cells of another cell type.Essential knowledge 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. c. Signals released by one cell type can travel long distances to target cells of another cell type.

Paracrine signaling—target cells lie near the secreting cells

Autocrine signaling—target cell is also the secreting cell

Both use local regulators that travel short distances, reaching target cells by diffusion

Both play roles in regulating blood pressure, nervous system function, and reproduction

PARACRINE AND AUTOCRINE SIGNALING

Essential knowledge 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. b. Cells communicate over short distances by using local regulators that target cells in the vicinity of the emitting cell.


Synaptic signaling--neurons form specialized junctions with target cells, called synapsesAt synapses, neurons secrete molecules called neurotransmitters that diffuse short distances and bind to receptors on target cells

SYNAPTIC AND NEUROENDOCRINE SIGNALING



Neuroendocrine signaling--specialized neurosecretory cells secrete molecules (neurohormones) that travel to target cells via the bloodstream (e.g. vasopressin—essential to kidney function and water balance)

SYNAPTIC AND NEUROENDOCRINE SIGNALING


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

SIGNALING BY PHEROMONES

Essential knowledge 3.E.1: Individuals can act on information and communicate it to others. a. Organisms exchange information with each other in response to internal changes and external cues, which can change behavior. LO 3.42 The student is able to describe how organisms exchange information in response to internal changes or environmental cues.

Essential knowledge 3.E.1: Individuals can act on information and communicate it to others. a. Organisms exchange information with each other in response to internal changes and external cues, which can change behavior. LO 3.42 The student is able to describe how organisms exchange information in response to internal changes or environmental cues.

Endocrine glands – endocrine cells grouped together in ductless organs Secrete hormones

directly into surrounding fluid

Exocrine glands – have ducts and secrete substances onto body surfaces or into cavities

ENDOCRINE TISSUES AND ORGANS

The same hormone may have different effects on target cells that have

Different receptors for the hormone

Different signal transduction pathways

MULTIPLE EFFECTS OF HORMONES

Negative feedback inhibits a response by reducing the initial stimulus, thus preventing excessive pathway activity

FEEDBACK REGULATION

Essential knowledge 2.C.1: Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes. a. Negative feedback mechanisms maintain dynamic homeostasis for a particular condition (variable) by regulating physiological processes, returning the changing condition back to its target set point.


Positive feedback reinforces a stimulus to produce an even greater response

FEEDBACK REGULATION

Essential knowledge 2.C.1: Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes. b. Positive feedback mechanisms amplify responses and processes in biological organisms. The variable initiating the response is moved farther away from the initial set-point. Amplification occurs when the stimulus is further activated which, in turn, initiates an additional response that produces system change.

Essential knowledge 2.C.1: Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes. b. Positive feedback mechanisms amplify responses and processes in biological organisms. The variable initiating the response is moved farther away from the initial set-point. Amplification occurs when the stimulus is further activated which, in turn, initiates an additional response that produces system change.

Insulin produced by alpha cells of pancreatic islets Reduces blood glucose levels by Promoting the cellular

uptake of glucose Slowing glycogen

breakdown in the liver Promoting fat storage,

not breakdown

INSULIN AND GLUCAGON: CONTROL OF BLOOD GLUCOSE


Glucagon produced by beta cells of pancreatic islets increases blood glucose levels by Stimulating conversion

of glycogen to glucose in the liver

Stimulating breakdown of fat and protein into glucose

INSULIN AND GLUCAGON: CONTROL OF BLOOD GLUCOSE


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

DIABETES MELLITUS

Essential knowledge 2.C.1: Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes. c. Alteration in the mechanisms of feedback often results in deleterious consequences.


Endocrine pathways are subject to regulation by the nervous system, including the brain

CONCEPT 45.3: THE HYPOTHALAMUS AND PITUITARY ARE CENTRAL TO ENDOCRINE

REGULATION

The hypothalamus receives information from the nervous system and initiates responses through the endocrine system

Attached to the hypothalamus is the pituitary gland Posterior pituitary - stores

and secretes hormones that are made in the hypothalamus

Anterior pituitary - makes and releases hormones under regulation of the hypothalamus

COORDINATION OF ENDOCRINE AND NERVOUS SYSTEMS IN VERTEBRATES

The two hormones released from the posterior pituitary act directly on nonendocrine tissues

POSTERIOR PITUITARY HORMONES

• Oxytocin regulates milk secretion by the mammary glands

• Antidiuretic hormone (ADH) regulates water uptake by the kidneysEssential knowledge 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via

chemical signaling. c. Signals released by one cell type can travel long distances to target cells of another cell type.Essential knowledge 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. c. Signals released by one cell type can travel long distances to target cells of another cell type.

Eating a bag of salty pretzels decreases blood osmolarity

This triggers the release of ADH by posterior pituitary

ADH makes kidneys retain more water and excrete more concentrated urine

Blood osmolarity increases, osmoreceptors in hypothalamus reduce ADH production

What do you think happens if you drink a large volume of water?

ANTIDIURETIC HORMONE (ADH)



Ch. 44

Hormone production here is controlled by releasing and inhibiting hormones from the hypothalamus

For example, prolactin-releasing hormone from the hypothalamus stimulates the anterior pituitary to secrete prolactin (PRL), which has a role in milk production

ANTERIOR PITUITARY HORMONES


The release of thyroid hormone results from a hormone cascade pathway involving the hypothalamus, anterior pituitary, and thyroid gland

Hormone cascade pathways typically involve negative feedback

THYROID REGULATION: A HORMONE CASCADE PATHWAY

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Essential knowledge 2.C.1: Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes. a. Negative feedback mechanisms…Essential knowledge 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. c. Signals released by one cell type can travel long distances to target cells of another cell type.

Essential knowledge 2.C.1: Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes. a. Negative feedback mechanisms…Essential knowledge 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. c. Signals released by one cell type can travel long distances to target cells of another cell type.

Hypothyroidism, too little thyroid function, can produce symptoms such as

Weight gain, lethargy, cold intolerance Hyperthyroidism, excessive production of

thyroid hormone, can lead to High temperature, sweating, weight loss,

irritability, and high blood pressure Graves disease, a form of hyperthyroidism

caused by autoimmunity, is typified by protruding eyes

DISORDERS OF THYROID FUNCTION AND REGULATION



Thyroid hormone refers to a pair of hormones

Triiodothyronin (T3), with three iodine atoms

Thyroxine (T4), with four iodine atoms

Insufficient dietary iodine causes pituitary to secrete TSH

TSH levels lead to an enlarged thyroid gland, called a goiter

MALNUTRITION CAN ALTER THYROID FUNCTION



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Endocrine signaling regulates homeostasis, development, and behavior

CONCEPT 45.4: ENDOCRINE GLANDS RESPOND TO DIVERSE STIMULI IN REGULATING HOMEOSTASIS,

DEVELOPMENT, AND BEHAVIOR

Two antagonistic hormones regulate the homeostasis of calcium (Ca2+) in the blood of mammals

PARATHYROID HORMONE AND VITAMIN D: CONTROL OF BLOOD CALCIUM

• Parathyroid hormone (PTH) is released by the parathyroid glands

• Calcitonin is released by the thyroid gland

Essential knowledge 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. c. Signals released by one cell type can travel long distances to target cells of another cell type.

Essential knowledge 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. c. Signals released by one cell type can travel long distances to target cells of another cell type.

PTH releases Ca2+ from bone and stimulates reabsorption of Ca2+ in the kidneys

It also has an indirect effect, stimulating the kidneys to activate vitamin D, which promotes intestinal uptake of Ca2+ from food

Calcitonin decreases the level of blood Ca2+

It stimulates Ca2+ deposition in bones and secretion by kidneys

PTH INCREASES THE LEVEL OF BLOOD Ca2+

Essential knowledge 2.C.1: Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes. Essential knowledge 2.C.1: Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes.

The adrenal glands are adjacent to the kidneys

Each adrenal gland actually consists of two glands: the adrenal medulla (inner portion) and adrenal cortex (outer portion)

ADRENAL HORMONES: RESPONSE TO STRESS

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The adrenal medulla secretes epinephrine (adrenaline) and norepinephrine (noradrenaline)

They are secreted in response to stress-activated impulses from the nervous system

They mediate various fight-or-flight responses

HORMONES FROM THE ADRENAL MEDULLA

Epinephrine and norepinephrine Trigger the release of

glucose and fatty acids into the blood

Increase oxygen delivery to body cells

Direct blood toward heart, brain, and skeletal muscles and away from skin, digestive system, and kidneys

The release of epinephrine and norepinephrine occurs in response to involuntary nerve signals

SHORT TERM STRESS

Essential knowledge 3.E.1: Individuals can act on information and communicate it to others. a. Organisms exchange information with each other in response to internal changes and external cues, which can change behavior.

Essential knowledge 3.E.1: Individuals can act on information and communicate it to others. a. Organisms exchange information with each other in response to internal changes and external cues, which can change behavior.

The adrenal cortex releases a family of steroids called corticosteroids in response to stress

These hormones are triggered by a hormone cascade pathway via the hypothalamus and anterior pituitary (ACTH)

Humans produce two types of corticosteroids: glucocorticoids and mineralocorticoids

HORMONES FROM THE ADRENAL CORTEX

Glucocorticoids, such as cortisol, influence glucose metabolism and the immune system

Mineralocorticoids, such as aldosterone, affect salt and water balance

The adrenal cortex also produces small amounts of steroid hormones that function as sex hormones


The gonads, testes and ovaries, produce most of the sex hormones: androgens, estrogens, and progestins

All three sex hormones are found in both genders, but in significantly different proportions

Synthesis of the sex hormones is controlled by FSH and LH from the anterior pituitary

GONADAL SEX HORMONES

The testes primarily synthesize androgens, mainly testosterone, which stimulate development and maintenance of the male reproductive system (sperm production)

Testosterone causes an increase in muscle and bone mass and is often taken as a supplement to cause muscle growth, which carries health risks

TESTOSTERONE


Estrogens, most importantly estradiol, are responsible for maintenance of the female reproductive system and the development of female secondary sex characteristics

In mammals, progestins, which include progesterone, are primarily involved in preparing and maintaining the uterus

ESTROGENS AND PROGESTINS


hormones and the endocrine system chapter 45

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specialized cells

animal cells

target receptors

cell type

chemical signals

short distances

target cellssynaptic

long distances