Endocrine System

1
Mariebs Human Anatomy and Physiology Ninth
Edition Marieb w Hoehn

• Chapter 16
• Endocrine System
• Lecture 13

2
Midterm Grades
Your midterm grades (due March 29th) will be
calculated as follows Lec 1 Exam 100
pointsLec 2 Exam 100 pointsLab 1 Exam
100 pointsLaboratory Grade 30 points (6
labs so far) Total points possible so far...330
points Your grade (Total points you have /
330) 100 Notes 1) Extra credit points you
have earned so far will be included.2) No grades
will be dropped for calculation of midterm grade.
3
Mid-term Checkup
Based on the three (3) grades you have received
so far, you should do a mid-term checkup. To find
your average so far total the following points
Lec Exam 1 Lec Exam 2 Lab Exam 1 Lab points
(6 labs) Example (83 67 90 26) ? 330
0.80 (80) Dropping the low grade (83 90 26)
? 230 0.86 (86) To figure out what you need
to AVERAGE for the next lecture and/or lab exam
and the final COMBINED to get a particular grade
Average grade needed on remaining exams
Points desired (see syllabus) Total points so
far

350 (if no grade dropped) or 450 (if low grade
dropped)
This formula assumes you will have 50 pts for
lab and 6 XC pts at the end of the course
4
Points and Grades (from Syllabus) - Revised
Grade for Course Grade as Points (of a possible 700) Quality Points
A 92-100 644-700 4.0
A- 90-91 630-643 3.7
B 88-89 616-629 3.3
B 82-87 574-615 3.0
B- 80-81 560-573 2.7
C 78-79 546-559 2.3
C 70-77 490-545 2.0
D 68-69 476-489 1.0
D 60-67 420-475 0.7
F less than 60 less than 420 0.0
Example 1 To get a grade of B for the course,
using the example grades on previous slide, and
not dropping lowest grade (50), and assuming 50
pts for lab and 6 XC points
574 (83 67 90 50 6) x
x 0.79 (79) Average on upcoming exams
350
Example 2 To get a grade of B for the course,
using the example grades on previous slide, and
dropping lowest grade (67), and assuming 50 pts
for lab and 4 XC points
574 (83 90 50 6) x
x 0.76 (76) Average on upcoming exams
450
5
Lecture Overview

• Overview of the Endocrine System
• Hormone Chemistry and Actions
• Control of Hormone Secretion
• ----------------------------------------------
• The Hypothalamus / Pituitary Gland
• The Thyroid Gland
• The Parathyroid Glands

6
Overview of the Endocrine System
The endocrine system consists of collections of
cells located in tissues scattered throughout the
body that produce substances released into the
blood (hormones) to ultimately affect the
activity and metabolism of target cells.
Figure from Martini, Anatomy Physiology,
Prentice Hall, 2001
7
Endocrine System

• Endocrine glands are ductless
• Effects of hormones are INTRAcellular

• Exocrine glands have ducts
• Effects are EXTRAcellular

Figure from Holes Human AP, 12th edition, 2010
8
Endocrine Glands

• Endocrine glands
• release hormones
• hormones travel throughout body in blood to
  targets
• targets must have receptors to respond

• Paracrine secretions
• act locally
• do not travel through blood

• Autocrine secretions
• affect only the secreting cell

Hormones regulate metabolic processes and change
activity of cells - Rates of biochemical
reactions - Water/electrolyte balance - Blood
pressure - Reproduction, development, and growth
9
Comparison of Nervous and Endocrine Systems
Figure from Holes Human AP, 12th edition, 2010

• Neurons release neurotransmitters into a
  synapse, affecting postsynaptic cells
• Glands release hormones into the bloodstream
• Only target of hormone responds

10
Classification of Hormones
Amino acids
Amino Acid Derivatives
Peptides
Proteins, glycoproteins
Hormones
Steroids (cholesterol-derived)
Lipid Derived
Eicosanoids (cell membranes)(locally acting)
11
Eicosanoid Synthesis

• Eicosanoids are important paracrine factors that
  mediate many processes in the body, including
• Inflammation- blood vessel constriction -
  blood clotting- smooth muscle contraction and
  relaxation

12
Types of Hormones
Figure from Holes Human AP, 12th edition, 2010
13
Steroid Hormones
Composed of rings of C and H Steroid hormones are
hydrophobic, i.e., lipid soluble
What does this mean for - Blood (plasma)
solubility? - Cell membrane solubility?
14
Actions of Steroid Hormones

• hormone crosses membranes

Figure from Holes Human AP, 12th edition, 2010

• hormone combines with receptor in nucleus or
  cytoplasm

• synthesis of mRNA activated

• mRNA enters cytoplasm to direct synthesis of
  protein, e.g., aldosterone-gtNa/K Pump

(Thyroid hormone has a similar mechanism of
action, even though it is a tyrosine derivative)
Magnitude of cellular response proportional to
the number of hormone-receptor complexes formed
15
Amino Acid-Derived Hormones
Figure from Holes Human AP, 12th edition, 2010
Water soluble (hydrophilic) What does this imply
about their solubility in blood and the cell
membrane?
16
Actions of Amino Acid-Derived Hormones
Figure from Holes Human AP, 12th edition, 2010

• hormone (first messenger) binds to receptor on
  cell membrane

• adenylate cyclase activated

• ATP converted to cAMP

• cAMP (second messenger) promotes a series of
  reactions leading to cellular changes

Magnitude of response is not directly
proportional to the number of hormone-receptor
complexes its amplified
17
Target Cell Activation by Hormones

• Target cells must have specific receptors to be
  activated by hormones
• Target cell activation depends upon
• Blood levels of the hormone
• Rate of release from producing organ
• Rate of degradation (target cells, kidney, liver)
• Half-life
• Relative numbers of receptors for the hormone
• Cellular receptors can be up- or down-regulated
• Affinity (strength) of binding of the hormone to
  its receptor

18
Control of Hormone Secretion
Ca2
Ca2
Endocrine organ 1
Blood plasma
Ca2
Ca2
Ca2
Ca2
2) Humoral control
3) Hormonal control
(Hormone)
Ca2
1) Neural control
Endocrine organ
Endocrine organ 2
Endocrine organ
Hormone secretion
Slide moved
19
Negative Feedback for Hormone Regulation
Figure from Holes Human AP, 12th edition, 2010
Recall that homeostasis is the maintenance of
STABLE (not constant) internal conditions
Slide moved
20
Control of Hormonal Secretions
Figure from Holes Human AP, 12th edition, 2010

• primarily controlled by negative feedback
  mechanism

Humoral
Hormonal
Neural
Control mechanisms for hormone release
21
Major Endocrine Glands
Figure from Holes Human AP, 12th edition, 2010
22
Pituitary Gland (Hypophysis)

• Two distinct portions
• anterior pituitary (adenohypophysis)
• posterior pituitary (neurohypophysis)

Figure from Holes Human AP, 12th edition, 2010
23
Overview of the Pituitary Hormones
Figure from Martini, Anatomy Physiology,
Prentice Hall, 2001
All anterior and posterior pituitary hormones
bind to membrane receptors and use 2nd messengers
(cAMP)
SeT GAP
24
Pituitary Gland Control
Figure from Holes Human AP, 12th edition, 2010

• Hypothalamic releasing hormones stimulate cells
  of anterior pituitary to release their hormones
• Nerve impulses from hypothalamus stimulate nerve
  endings in the posterior pituitary gland to
  release its hormones

Note the hypophyseal portal system (two
capillaries in series)
25
Hormones of the Anterior Pituitary (SeT GAP)
Figure from Holes Human AP, 12th edition, 2010
(an axis)
Tropic hormones (in black ? ) control the
activity of other endocrine glands
All anterior pituitary hormones use second
messengers
26
Anterior Pituitary Hormones

• Pro-opiomelanocortin (POMC) has also been
  isolated from the anterior pituitary
• A prohormone that must be split enzymatically in
  order to become active
• POMC is the source of several other hormones
• ACTH
• Natural opiates (enkephalin, ?-endorphin)
• Melanocyte-stimulating hormone (MSH)

27
Anterior Pituitary Hormones - GH

• Growth Hormone (GH)
• main target is skeletal muscle, bone, and
  cartilage
• stimulates increase in size and metabolic rate
  of body cells
• anabolic (tissue building) and diabetogenic (?
  glucose)
• Circadian (24-hour) pattern of secretion -
  highest during sleep
• action via insulin-like growth factors
  (somatomedins)
• enhances movement of amino acids through
  membranes
• promotes lipolysis and glycogenolysis
  (diabetogenic effect)
• promotes growth of long bones
• secretion inhibited by somatostatin (GHIH)
• somatotrope secretion stimulated by growth
  hormone-releasing hormone (GHRH)

28
Anterior Pituitary Hormones - PRL

• Prolactin (PRL)
• stimulates milk production by the breasts (rises
  at end of pregnancy infant suckling after birth)
• amplifies effect of LH in males (? sens. of
  interstitial cells)
• secretion inhibited by hypothalamic PIH
  (dopamine)
• secretion stimulated by PRF (serotonin?)
• produced by lactotropes (mammotropes)
• brief rise in PRL levels just before menstrual
  period partially accounts for breast swelling and
  tenderness

29
Anterior Pituitary Hormones TSH/ACTH

• Thyroid Stimulating Hormone (TSH)
• controls secretions of hormones from the thyroid
  gland
• release controlled by thyrotropin-releasing
  hormone (TRH) from the hypothalamus
• produced by thyrotropes

• Adrenocorticotropic Hormone (ACTH)
• controls secretions of some hormones of adrenal
  cortex
• release controlled by corticotropin-releasing
  hormone (CRH) from the hypothalamus
• produced by corticotropes

What term would describe these two hormones that
cause the secretion of other hormones in distant
endocrine tissues?
- Tropic hormones -
30
Anterior Pituitary Hormones FSH/LH
- Tropic hormones -

• Follicle-Stimulating Hormone (FSH)
• stimulates gamete production in males and
  females
• controlled by gonadotropin-releasing hormone
  (GnRH)
• stimulates follicular cells to secrete estrogen

• Luteinizing Hormone (LH)
• promotes secretions of sex hormones in both
  sexes
• controlled by gonadotropin-releasing hormone
  (GnRH)
• stimulates release of egg from ovaries in
  females promotes growth of long bones
• known as Interstitial Cell Stimulating Hormone
  in males

FSH and LH are gonadotropins produced by
gonadotropes
31
Posterior Pituitary Hormones ADH/OT

• Antidiuretic Hormone (ADH vasopressin or AVP)
• causes kidneys to reduce water excretion
• in high concentration, raises blood pressure
• controlled by hypothalamus in response to
  changes in blood water concentration
  (osmoreceptors) and blood volume
• inhibited by alcohol, diuretics

• Oxytocin (OT) smooth muscle contraction
• stimulates uterine contractions
• stimulates lactating mammary glands to eject
  milk
• controlled by hypothalamus in response to
  stretch in uterine and vaginal walls and
  stimulation of breasts
• thought also to play a role in sexual arousal,
  orgasm, sexual satisfaction, and promotion of
  cuddling behavior

Both hormones use IP3-calcium second messenger
32
Thyroid Gland
Figure from Martini, Anatomy Physiology,
Prentice Hall, 2001
33
Thyroid Gland
Follicular cells produce thyroglobulin (TG) After
being attached to iodine, TG is stored in colloid
in the follicles I-bound TG is the source of
thyroid hormones, T3 (3 I-) and T4 (4 I-)
Parafollicular cells, or C, cells, of the
thyroid gland produce calcitonin
Figure from Martini, Anatomy Physiology,
Prentice Hall, 2001
34
Thyroid Hormones
Figure from Martini, Anatomy Physiology,
Prentice Hall, 2001

• Thyroxine (T4) and Triiodothyronine (T3)
• increases BMR and rate of energy release from
  CHO (calorigenic effect)
• ? rate of protein synthesis
• accelerates growth critical for
  skeletal/nervous system
• important for reproductive function
• release controlled by TSH (from anterior
  pituitary) highest before sleep and at night

35
Thyroid Gland Disorders

• General Hyperthyroidism
• high metabolic rate
• hyperactivity
• weight loss
• protruding eyes

• Congenital hypothyroidism (Older terminology -
  Cretinism)
• hypothyroidism in infants
• leads to small stature and mental retardation

36
Thyroid Gland Disorders

• Myxedema
• adult hypothyroidism
• low metabolic rate
• sluggishness

• Simple (Endemic) Goiter
• deficiency of iodine
• leads to deficiency of thyroid hormones
• thyroid gland enlarges

• Graves disease
• overstimulation of gland by antibodies that
  mimic TSH
• hyperthyroidism

37
Calcitonin
3
1
Figure from Martini, Anatomy Physiology,
Prentice Hall, 2001
2

• Calcitonin
• lowers blood calcium and phosphate ion
  concentrations by inhibiting release of calcium
  and phosphate from bones
• increases rate at which calcium and phosphate
  are deposited in bones
• most important in children weak hypocalcemic
  agent in adults

38
Parathyroid Glands
Figure from Holes Human AP, 12th edition, 2010

• PTH (parathormone, parathyroid hormone)
• increases blood calcium levels
• stimulates bone resorption by osteoclasts
• stimulates kidneys to retain calcium and excrete
  phosphate
• promotes calcium absorption into intestine

39
Parathyroid Hormone
1
3
Figure from Martini, Anatomy Physiology,
Prentice Hall, 2001
2
Calcium ion homeostasis is maintained by a
negative feedback system involving a pair of
hormones with opposite effects, PTH and calcitonin
40
Parathyroid Glands
PTH promotes Ca2 absorption in the intestine
(via vitamin D) and Ca2 reabsorption by the
kidney
Figure from Holes Human AP, 12th edition, 2010
41
Overview of Calcium Homeostasis
Figure from Martini, Anatomy Physiology,
Prentice Hall, 2001
42
Review

• The endocrine system consists of
• Tissues scattered throughout the body that
  secrete
• Hormones, which are chemical messengers,
• Into the blood to circulate throughout the body
• And affect metabolism/activity of target cells
• A major control system of the body
• Regulates many body functions
• Rates of reactions
• Transport of substances
• Water and electrolyte balance
• Blood pressure
• Reproduction, development, and growth

43
Review

• Hormones can be divided chemically into
• Amino acid derivatives
• Peptides, proteins, glycoproteins, amines
• Water soluble (cannot cross cell membranes)
• Use membrane-based receptors
• Response can be amplified by intracellular
  cascades
• Use second messengers (cAMP, cGMP, DAG, IP3)
• Examples norepinephrine, insulin, ADH, TSH
• Steroid hormones
• Composed of rings of C and H
• Lipid soluble (can cross cell membranes)
• Response is proportional to number of
  intracellular hormone-receptor complexes
• Examples Sex hormones, aldosterone, cortisol

44
Review

• Hormone release is controlled by
• Humoral factors, e.g., blood Ca2, glucose
• Neural mechanisms, e.g., SNS stimulation of
  adrenal medulla
• Hormonal mechanisms, e.g., hypothalamus-pituitary
• Control of hormone secretion is mostly
  accomplished by negative feedback

45
Review

• The pituitary gland is a major site of hormone
  production
• Anterior (adenohypophysis)
• Hormone secreting cells
• Release controlled by hypothalamic releasing
  hormones
• ACTH, GH, LH/FSH, Prolactin, TSH
• Posterior (neurohypophysis)
• Storage area for hormones produced in the
  hypothalamus
• Release controlled by neural activity
• ADH and OT

46
Review
HORMONE SECRETED BY WHAT GLAND? TARGET(S)? EFFECT(S) AT TARGET SITE
Growth Hormone (GH) anterior pituitary bone, muscle, fat growth of tissues
Thyroid Stimulating Hormone (TSH) anterior pituitary thyroid secrete hormones
Prolactin (PRL) anterior pituitary mammary glands produce milk
Adrenocorticotropic hormone (ACTH) anterior pituitary adrenal cortex secrete adrenal hormones
Luteinizing Hormone (LH) anterior pituitary In males interstitial cells in testes in females mature ovarian follicle males testosterone secretion females ovulation
Follicle stimulating hormone (FSH) anterior pituitary males semin-iferous tubules of testes females ovarian follicle males sperm production females follicle/ovum maturation
Anti-Diuretic Hormone (ADH) (Vasopressin) posterior pituitary Collecting ducts of kidneys reabsorption of water increases blood pressure
Oxytocin (OT) posterior pituitary uterine smooth muscle breast contraction during labor milk letdown
47
Review
HORMONE SECRETED BY WHAT GLAND? TARGET(S)? EFFECT(S) AT TARGET SITE
Triiodothyronine (T3) Thyroxine (T4) Thyroid (follicular cells) all cells increases rate of metabolism
Calcitonin Thyroid (C cells) Distal convoluted tubules and osteoblasts secretion of Ca into urine, bone formation (de-creases blood Ca)
Parathyroid Hormone (PTH) Parathyroids Proximal kidney tubules, osteoclasts, intestine reabsorption of Ca into blood, bone resorption, dietary Ca absorption (increases blood Ca)
Remember that PTH and calcitonin have opposing
effects in regulating blood calcium levels (they
are antagonists)