Click here to proceed.

1

• Hormones and the Endocrine System

2
Hormones 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

• Example
• Insect
• metamorphosis is
• regulated by
• hormones

3
Regulation and Communication

• Animals rely on 2 systems for regulation
• endocrine system
• system of ductless glands
• secrete chemical signals directly into blood
• chemical travels to target tissue
• target cells have receptor proteins
• slow, long-lasting response
• nervous system
• system of neurons
• transmits electrical signal release
  neurotransmitters to target tissue
• fast, short-lasting response

4
Intracellular Communication

• Endocrine Signaling
• Hormones secreted by endocrine cells reach their
  targets via the bloodstream
• Endocrine signaling maintains homeostasis,
  mediates responses to stimuli, regulates growth
  and development

5
Intracellular Communication

• Local regulators- molecules that act over short
  distances, reaching target cells solely by
  diffusion
• Ex cytokines enable communication between
  immune cells
• Paracrine signaling- target cells lie near the
  secreting cells
• Autocrine signaling- target cell is also the
  secreting cell

6
Intracellular Communication

• Synaptic signaling- neurons form specialized
  junctions with target cells, called synapses
• At synapses, neurons secrete molecules called
  neurotransmitters that diffuse short distances
  and bind to receptors on target cells
• Neuroendocrine signaling- specialized
  neurosecretory cells secrete molecules called
  neurohormones that travel to target cells via the
  bloodstream.
• Ex ADH (antidiuretic hormone), essential to
  kidney function and water balance.

7
Signaling by Pheromones

• Pheromones- chemicals that are released into the
  environment by animals of the same species
• Functions
• marking trails leading to food
• defining territories
• warning of predators
• attracting potential mates

Asian army ants (Leptogenys distinguenda) follow
a pheromone-marked trail as they carry pupae and
larvae to a nest site.
8
Endocrine Tissues and Organsendocrine cells are
grouped together to form glands they secrete
hormones directly into surrounding fluid
9
Classes of Hormones

• Protein-based hormones
• polypeptides
• small proteins insulin, ADH
• glycoproteins
• large proteins carbohydrate FSH, LH
• amines
• modified amino acids epinephrine, melatonin
• Lipid-based hormones
• steroids
• modified cholesterol sex hormones, aldosterone

insulin
10
How do hormones act on target cells?

• Lipid-based hormones
• hydrophobic lipid-soluble
• diffuse across cell membrane enter cells
• bind to receptor proteins in cytoplasm nucleus
• bind to DNA as transcription factors
• turn on genes
• Protein-based hormones
• hydrophilic not lipid soluble
• cant diffuse across cell membrane
• bind to receptor proteins in cell membrane
• trigger secondary messenger pathway
• activate internal cellular response
• enzyme action, uptake or secretion of molecules

11
Action of Lipid (steroid) Hormones response is
usually a change in gene expression
steroid hormone
target cell
blood
S
1
S
cross cell membrane
protein carrier
S
2
cytoplasm
binds to receptor protein
becomes transcription factor
5
mRNA read by ribosome
S
3
plasma membrane
4
DNA
mRNA
6
7
nucleus
protein
protein secreted
ex secreted protein growth factor (hair, bone,
muscle, gametes)
12
Action of Protein Hormones
signal-transduction pathway
1
signal
proteinhormone
plasma membrane
P
activates G-protein
binds to receptor protein
activates enzyme
cAMP
acts as 2 messenger
receptor protein
ATP
transduction
GTP
activatescytoplasmicsignal
ATP
activates enzyme
2
secondary messengersystem
activates enzyme
cytoplasm
response
3
produces an action
target cell
13
Example of Signal Transduction Fight-or-Flight
Response- epinephrine (adrenaline) secreted by
adrenal gland
signal
1
epinephrine
activatesG protein
3
activates adenylyl cyclase
receptor protein in cell membrane
cAMP
GDP
transduction
4
ATP
2
GTP
activates protein kinase-A
5
activates GTP
activates phosphorylase kinase
cytoplasm
releasedto blood
activates glycogen phosphorylase
7
6
glycogen
glucose
liver cell
response
14
The same hormone may have different effects on
target cells
15
Coordination of Neuroendocrine and Endocrine
Signaling

• Endocrine and nervous systems generally act
  coordinately to control reproduction and
  development
• example larvae of butterflies and moths,
  signals direct molting originate in the brain
• A brain hormone (PTTH) stimulates release of
  ecdysteroid from the prothoracic glands
• Juvenile hormone promotes retention of larval
  characteristics
• Ecdysone promotes molting (in the presence of
  juvenile hormone) and development (in the absence
  of juvenile hormone) of adult characteristics

16
(No Transcript)
17
Simple Hormone Pathways

• Simple Endocrine Pathway
• 1. Hormones are released from an endocrine cell,
  
• 2. Travel through the bloodstream
• 3. Interact with specific receptors within a
  target cell
• 4. Cause a physiological response

• Simple Neuroendocrine Pathway
• 1. Stimulus is received by a sensory neuron
• 2. Stimulates a neurosecretory cell
• 3. Neurosecretory cell secretes a neurohormone
• 4. Neurohormone enters the bloodstream and
  travels to target cells

18
Maintaining Homeostasis thru Feedback Regulation
hormone 1
Negative FeedbackModel Review
lowersbody condition
gland
specific body condition
raisesbody condition
Question How does a positive feedback system
work?
gland
hormone 2
19
Blood Osmolarity
Endocrine System Control Example
Feedback
ADH
increasedwaterreabsorption
pituitary
blood osmolarity blood pressure
increasedwater saltreabsorption
renin
aldosterone
angiotensinogen
angiotensin
20
Regulation of Blood Sugar
Endocrine System Control Example
Feedback
islets of Langerhans beta islet cells
insulin
body cells takeup sugar from blood
liver storesglycogen
reducesappetite
Question Why are insulin and glucagon considered
antagonist?
blood sugar level (90mg/100ml)
liver releasesglucose
triggershunger
islets of Langerhansalpha islet cells
glucagon
21
Coordination of Endocrine Nervous Systems in
Vertebrates

• Hypothalamus master nerve control center
• nervous system
• receives information from nerves around body
  about internal conditions
• releasing hormones regulates release of hormones
  from pituitary
• Pituitary gland master gland
• endocrine system
• secretes broad rangeof tropic hormones
  regulating other glands in body

22
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

23
Posterior Pituitary Hormones
24
Anterior Pituitary Hormones
Tropic hormones target endocrine glands
25
Hormone Cascade PathwayThyroid Regulation

• Hormone cascade pathway
• A hormone can stimulate the
• release of a series of other
• hormones, the last of which
• activates a nonendocrine
• target cell.
• Hormone cascade pathways typically involve
  negative feedback
• Example release of thyroid hormone results from
  a hormone cascade pathway involving the
  hypothalamus, anterior pituitary, and thyroid
  gland

tyrosine iodine
thyroxines
26
Hormone Cascade Pathway Example
27
Goiter

• Iodine deficiency causes thyroid to enlarge as it
  tries to produce thyroxine

?
tyrosine iodine
?
thyroxines
28
Evolution of Hormone Function
What does this tell you about these hormones?
How could these hormones have different effects?
prolactin
gene duplication?
29
Endocrine signaling regulates
homeostasis, behavior, and development
30
Regulation of Blood Calcium
Endocrine System Regulation Homeostasis
Feedback
calcitonin
blood calcium level(10 mg/100mL)
activated Vitamin D
parathyroid hormone (PTH)
31
Endocrine System Regulation Behavior
Adrenal Hormones Response to Stress
Stress
Nerve signals
Hypothalamus
Spinal cord (cross section)
Releasing hormone
Nerve cell
Anterior pituitary
Blood vessel
adrenal medulla secretes epinephrine
norepinephrine
Nerve cell
Adrenal cortex secretes mineralocorticoids
glucocorticoids
ACTH
Adrenal gland
Kidney
MEDULLA
CORTEX
(B) LONG-TERM STRESS RESPONSE
(A) SHORT-TERM STRESS RESPONSE
Effects of mineralocorticoids 1. Retention of
sodium ions water by kidneys 2. Increased
blood volume blood pressure
Effects of glucocorticoids 1. Proteins fats
broken down converted to glucose, leading to
increased blood glucose 2. Immune system
suppressed
Effects of epinephrine and norepinephrine 1. Gly
cogen broken down to glucose increased blood
glucose 2. Increased blood pressure 3. Increased
breathing rate 4. Increased metabolic
rate 5. Change in blood flow patterns, leading to
increased alertness decreased digestive
kidney activity
32
Endocrine System Regulation Reproduction

• Gonadal Sex HormonesGonads, testes and ovaries
  - produce most of the sex hormones androgens,
  estrogens, and progestinsAll three sex hormones
  are found in both males and females, but in
  significantly different proportionsSynthesis of
  the sex hormones is controlled by FSH and LH from
  the anterior pituitary

33
Sex Hormones

• Androgens
• Testes primarily synthesize androgens, mainly
  testosterone, which stimulate development and
  maintenance of the male reproductive system
• Testosterone causes an increase in muscle and
  bone mass and is often taken as a supplement to
  cause muscle growth, which carries health risks

• Estrogens
• Estrogens, most importantly estradiol, are
  responsible for maintenance of the female
  reproductive system and the development of female
  secondary sex characteristics
• Progestins
• In mammals, progestins, which include
  progesterone, are primarily involved in preparing
  and maintaining the uterus

34
Female reproductive cycle
Feedback
eggmatures is released(ovulation)
builds up uterus lining
estrogen
progesterone
FSH LH
fertilized egg(zygote)
maintainsuterus lining
pituitarygland
hCG
pregnancy
progesterone
GnRH
corpus luteum breaks down progesterone
drops menstruation
hypothalamus
maintainsuterus lining