The Endocrine System Chapter 17 Lecture Notes

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The Endocrine SystemChapter 17 Lecture Notes

• to accompany
• Anatomy and Physiology From Science to Life
• textbook by
• Gail Jenkins, Christopher Kemnitz, Gerard Tortora

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Chapter Overview

• 17.1 Endocrine System Overview
• 17.2 Hormone Secretion
• 17.3 Hypothalamus and Anterior Pituitary
• 17.4 Posterior Pituitary
• 17.5 Thyroid Gland
• 17.6 Parathyroid Glands
• 17.7 Adrenal Cortex
• 17.8 Pancreas
• 17.9 Gonads
• 17.10 Pineal Gland

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Essential Terms

• hormone
• chemical mediator that helps maintain homeostasis
• target cell
• cell with a receptor that responds to the
  presence of a hormone

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Introduction

• Endocrine secretion activity is less dramatic
  than activity of neurotransmitters
• Nervous system responses generally more immediate
• Endocrine system responses less immediate but
  more prolonged
• Two systems are integrated as a neuroendocrine
  system.
• Together, the two systems regulate and coordinate
  all of the activities of the body and maintain
  homeostatic balance.

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Concept 17.1Endocrine System Overview
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Endocrine System

• Nervous stimulation can trigger endocrine
  secretions
• Endocrine system controls activities by releasing
  hormones
• Most hormones enter interstitial fluid then are
  carried to target tissues by circulatory system
• Endocrine system and nervous system function
  together as a supersystem
• Endocrine system helps regulate virtually all
  types of body cells

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Endocrine Glands

• exocrine glands secrete products onto a surface
• endocrine glands secrete products into the body
  fluids by way of ducts
• hormones are carried to target tissues where
  activity is carried out
• The major endocrine glands are the hypothalamus,
  the pituitary, and the thyroid, parathyroid,
  adrenal, and pineal glands
• Other hormone secreting structures
• thymus, pancreas, ovaries, testes, kidneys,
  stomach, liver, small intestine, skin, heart,
  adipose tissue, placenta

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Table 17.1
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Figure 17.1
Glands and diffuse endocrine tissue
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Concept 17.2 Hormone Secretion
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Receptors

• hormones only affect target cells
• water soluble hormones have receptors on outside
  surface of cells and trigger responses inside
  the cell
• lipid soluble hormones receptors have receptors
  inside of the cell and trigger response inside
  cell
• target cells generally have between 2,000 and
  100,000 receptors for a given hormone

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Chemical Classes of Hormones

• water soluble
• amino acid based
• lipid soluble
• steroids
• thyroid hormones
• nitric oxide
• transported in blood by transport proteins
• slow rate of loss in kidneys
• ready reserve of hormone in blood stream

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Table 17.2 pt 1
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Table 17.2 pt 2
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Hormone Action

• variable depending on hormone and target cell
• various targets respond differently to same
  hormone
• some hormones activate synthetic or stimulatory
  processes
• others activate degradation or inhibitory
  processes

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Figure 17.2

• LIPID SOLUBLE HORMONES
• Require a transport protein to be moved by the
  blood
• Hormone action
• Hormone enters cell
• Travels to a receptor in the nucleus
• Triggers the transcription of a particular gene
• Which leads to the production of a particular
  protein that alters the activity of the cell

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• Water Soluble Hormones
• Do not require a transport protein to travel
  through the blood
• Hormone Action
• Hormone receptor is on SURFACE of cell
• Hormone DOES NOT ENTER cell
• Hormone acts as a FIRST MESSENGER
• Binding to the receptor helps generate cAMP,
  which acts as a SECOND MESSENGER
• cAMP activates protein kinases, enzymes that add
  phosphate groups to proteins
• Phosphorylated proteins cause reactions within
  the cell

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Hormone Interactions

• permissive effects
• one hormone allows the other to function
• synergistic effects
• one hormone intensifies the effects of the other
• antagonistic effects
• one hormone inhibits or reduces the effects of
  the other

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Control of Hormone Secretion

• hormones secreted in bursts
• as stimulation increases bursts increase in
  frequency
• in absence of stimulation, bursts are minimal or
  inhibited
• regulated by
• neural signals
• chemical changes in blood
• other hormones

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Concept 17.3 Hypothalamus Pituitary Gland
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Hypothalamus Master gland of the endocrine system

• controls the activity of the pituitary gland
• major integrating link between the nervous and
  endocrine systems
• hormones that stimulate anterior pituitary are
  all either releasing hormones or inhibiting
  hormones

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Figure 17.4
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Pituitary Gland

• two lobes
• anterior lobe
• stimulated by tropic hormones from hypothalamus
• hypophyseal portal system
• posterior lobe
• neural tissue that releases hormones produced in
  the hypothalamus
• neurosecretory cells

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Table 17.3
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Control and secretion of Cortisol
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Figure 17.6
Control and secretion of Human Growth Hormone
(hGH)
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Figure 17.11
Control and secretion of thyroid hormones
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FSH LH(Follicle stimulating hormone,
Luteinizing Hormone)

• released by the anterior pituitary
• triggered by GnRH from the hypothalamus
• target tissue gonads
• FSH
• in females initiates development of ovarian
  follicles
• in males stimulates sperm production
• LH
• in females triggers ovulation
• in males triggers testosterone secretion

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PRL (Prolactin)

• released by the anterior pituitary
• trigger is PRH and PIH from hypothalamus
• initiates and maintains milk secretion and
  production by mammary glands in females
• in males can cause erectile dysfunction

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ACTH (adenocorticotropic hormone)

• secreted by anterior pituitary
• triggered by CRH from hypothalamus
• also triggered by stress
• controls production and secretion of hormones
  called glucocorticoids
• cortisol from adrenal cortex
• cause negative feedback regulation of CRH and
  ACTH release

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MSH (Melanocyte stimulating hormone)

• secreted by anterior pituitary
• function unknown in humans
• presence of MSH receptors in brain suggests it
  may influence brain activity
• excessive CRH stimulates MSH release
• PIH inhibits MSH release

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Table 17.4 pt 1
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Table 17.4 pt 2
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Concept 17.4 Posterior Pituitary
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Posterior Pituitary

• AKA neurohypophysis
• Produces no hormones itself
• stores and releases two hormones produced by
  hypothalamus
• ADH (anitdiurectic hormone)
• OT (oxytocin)

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Figure 17.4
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OT

• oxytocin
• targets uterus and mammary glands during and
  after delivery
• uterus contracts
• milk ejection (let down)
• function in non-reproducing women and in men is
  unknown
• animal studies seem to indicate parental
  caretaking behavior toward offspring
• sexual pleasure during and after intercourse

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ADH

• antidiuretic hormone
• decreases urine production
• kidneys return water to blood
• decreases sweating
• causes constriction of arterioles
• increases blood pressure
• AKA vasopressin

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Control and secretion of ADH
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Table 17.5
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Concept 17.5 Thyroid Gland
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TSH (Thyroid stimulating hormone)

• Triggers
• follicular cells to produce
• thyroxine (T4)
• triiodothyronine (T3)
• parafollicular cells produce
• calcitonin
• involved in calcium homeostasis
• brings calcium levels down when too high

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Figure 17.10
Synthesis, secretion and transport of T3 and T4
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Figure 17.11
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Actions of Thyroid Hormones

• thyroxine and triiodothyronine
• regulate oxygen use and BMR

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Concept 17.6 Parathyroid
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PTH (parathyroid hormone)

• parathyroid hormone
• major regulator of calcium, magnesium, and
  phosphate ions in blood
• PTH brings blood levels of calcium up when too
  low

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Figure 17.13
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Table 17.7
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Concept 17.7 Adrenal Gland
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Adrenal Cortex

• divided into three zones
• each secretes its own hormone
• mineralocorticoids
• glucocorticoids
• androgens

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Figure 17.15
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Figure 17.16
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Figure 17.5
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Glucocorticoid Functions

• Protein breakdown
• Glucose formation
• Triglyceride breakdown
• Resistance to stress
• Anti-inflammatory effects
• Depression of immune responses

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Adrenal Medulla

• modified sympathetic ganglion of ANS
• epinephrine
• norepinephrine

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Concept 17.8 Pancreas
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Figure 17.17a
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Figure 17.17b
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Figure 17.17c
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Figure 17.17d
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Blood Glucose Level Regulation

• glucagon released when
• blood glucose is low
• insulin released when
• blood glucose is high

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Figure 17.18
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Table 17.9
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Concept 17.9 Gonads
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Gonads

• Produce
• estrogens
• progesterone
• testosterone
• Androgens
• Are affected by
• FSH (follicle stimulating hormone)and LH
  (luteinizing hormone)

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Table 17.10
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Concept 17.10 Pineal Gland
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Pineal Gland

• hormone secreted is melatonin
• contributes to setting the bodys biological
  clock
• promotes sleepiness in small doses
• in animals with breeding seasons, melatonin
  inhibits reproductive functions outside the season

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End Chapter 17