The Endocrine
System
Honors
Physiology
What are hormones?
 Hormones:




send messages
act locally or at a distance
work quickly or slowly
can be created/excreted by cells, tissues or
organs, collectively known as “glands”
 secreted via epithelial cells  extracellular fluid
 blood stream  receptors on target cells
 ducts are not used by endocrine system
Comparison to Nervous
System
Fig.
13.2
Comparison to Nervous
System
Entity
Cell type
Chemical
signal
Specificity of
response
Speed
Length of
effect
Nervous Sys
Endocrine Sys
Neurons
Epithelial
Neurotransmitter
Hormone
Receptors on
postsynaptic cell
Receptors on
target cells
Milliseconds
Seconds to hours
Brief
Brief or long
Example of Hormonal
Regulation—Today’s Lab
 Thyroxine
 Released from thyroid
gland
 Target: cells all over body
 Influences metabolism
 Thyroid stimulating
hormone (TSH)
 Released from anterior
pituitary gland
 Target: thyroid gland
 Signal: “release thyroid
hormones!”
Endocrine System—Relative Stability of
Hormone Concentrations
 Negative feedback
maintains stable
hormone levels
Fig. 13.11
Endocrine System—3 Ways To
Control Hormonal Secretions
Fig. 13.8
Example: Negative Feedback
Controls Blood Glucose Levels
 What
happens
when your
blood
glucose
gets too
low?
Fig 13.36
Example: Negative Feedback
Controls Blood Glucose Levels
 What
happens
when your
blood
glucose
gets too
high?
Fig 13.36
Steroid Hormones
Fig. 13.5
Steroid Hormones
 Lipid soluble
 Receptor in the nucleus
 binds hormone  gene transcription
 mRNA is then translated into a protein in the
cytoplasm
 Examples
 estrogen, testosterone
 aldosterone, cortisol
Nonsteroid Hormones
Fig. 13.7
Nonsteriod Hormones
 Cannot move through lipid bilayer
 Instead they bind to receptors in cell
membrane
 Examples:
 TSH
 Epinephrine
 Glucagon
Hypothalamus
 Regulates other glands to tell them when
to release their hormones
Fig. 13.9
Pituitary Gland
Fig. 13.9
Anterior Pituitary
 Adrenocorticotropic hormone (ACTH)
 Target: adrenal cortex, stimulates cortisol release
 influences protein and fat metabolism
 Gonadotropins
 follicle stimulating hormone (FSH)
 egg or sperm maturation
 For egg, stimulates release of egg from follicle mid cycle
 luteinizing hormone (LH)
 Stimulates release of sex hormones
Anterior Pituitary cont.
 Growth Hormone (GH)
 bone growth/osteogenesis
 Melanocyte Stimulating Hormone (MSH)
 skin color, includes tanning
 Prolactin (PRL)
 lactation
 Thyroid Stimulating Hormone (TSH)
 stimulates thyroid secretions
Robert P. Wadlow
8’ 11”
Yikes, his anterior pituitary
released too much growth
hormone!
Age
Height
8
6’
14
7’5”
18
8’4”
22
8’11”
Anterior Pituitary cont.
 How am I going to remember all of
this???
 A Green Giant Makes PRetty
Things






ACTH
Gonadotropins (FSH, LH/ICSH)
GH
MSH
PR
TSH
Posterior Pituitary
 Antidiuretic Hormone (ADH)
 decreases urine formation
 when you are dehydrated, your body says
“don’t lose water!”, so ADH is increased
 increased ADH = concentrated urine
 Oxytocin
 smooth muscle contractions in the uterus
during childbirth
 Recent studies = “bonding” hormone
Posterior Pituitary cont.
 Why do you urinate more when you drink
caffeine?
 Your body recognizes caffeine as a toxin
that it needs to expel from the body
 Caffeine is a diuretic – it makes you urinate
 it inhibits secretion of ADH
 you don’t get the “don’t lose water!” signal
 so you expel more water to try and flush out the
toxin
Pineal Gland
 Melatonin
 Helps regulate circadian rhythms (sleepwake cycle)
Thyroid
 Thyroxine or tetraiodothyronine (T4)-and
Triiodothyronine (T3)
 regulate your food metabolism (break down
glucose, fat & protein to create energy)
 increase temperature, growth and
development
Fig. 13.16
Thyroid & Parathyroid
 Thyroid releases
Calcitonin
 lowers calcium levels
in the blood
 Parathyroid releases
Parathyroid Hormone
(PTH)
Fig. 13.24
 increases calcium
levels in the blood
Pancreas
 Insulin
 Glucagon
 Islets of
Langerhans
 regulate blood
glucose levels
 Both hormones
created in the…
Fig. 13.34
Pancreas cont.
Islets of Langerhans
 Alpha Cells
 Make Glucagon
 Released when your
blood sugar levels get
low
 Increases blood
glucose levels by
breaking down
glycogen (storage
form of glucose in the
liver) and
noncarbohydrates
into glucose
 Beta Cells
 Make Insulin
 Released when your
blood sugar levels get
high
 Tells your body cells
to take sugar in, and
decreases blood
glucose levels by
stimulating the liver to
form glycogen
Pancreas cont.
 Diabetes- can’t regulate your blood glucose
 Type I - Juvenile
 Islets of Langerhans don’t work properly & cannot create
sufficient insulin (or glucagon)
 usually need insulin injections (why not glucagon
injections?)
 usually inherited
 Type II - Adult onset
 Insulin receptors throughout body don’t work properly
 usually can use oral treatment
 related to weight gain
 About 17 million people in the US have diabetes!
Adrenal Glands
 Adrenal Medulla
 epinephrine/adrenalin
Fig.
 norepinephrine/noradrenalin
13.28
 Increases blood glucose, heart
rate, etc.
 Blood vessels constrict in digestive
tract and kidneys, dilate in blood
vessels of the muscles
Adrenal Glands cont.
Adrenal Cortex
 Aldosterone
 Target cells in kidneys
 Maintain Na+ and K+ balance
 Cortisol
 Glucose, protein and fat metabolism
 Anti inflammatory
 Androgens
 supplement gonad sex hormones
Reproductive Organs
 Ovaries
 Estrogen
 stimulates egg maturation
 secondary female sex characteristics
 Progesterone
 maintains uterine lining in case of implantation
 Testes
 Testosterone
 regulates spermatogenesis
 secondary male sex characteristics
Adrenal Glands cont.
 Addison disease
 Cortisol hyposecretion
 low Na+, high K +, dehydration, low glucose,
can be very serious
 Cushing syndrome
 Cortisol hypersecretion (usually
by too much ACTH)
 High Na+, low K+, high glucose,
water retention
Thyroid cont.
 Grave’s disease
 too much hormone
 Hyperthyroidism
 Hashimoto’s disease
 too little hormone
 Hypothyroidism