Endocrine System
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Transcript Endocrine System
Endocrine System
Chapter 26
Endocrine System
A bodily system that uses hormones for communication and
chemical regulation
Hormones are chemical signals carried by the circulatory
system, made and secreted by endocrine glands
Long-distance regulators
Not quick acting system because hormones must be made,
circulated to all body cells, and sensed
Control whole body activities like responses to stress and long-
term developmental processes such as growth
Chemical Signaling
Endocrine cells are secretory vesicles that transport
hormones for release directly into the circulatory system
Hormones travel throughout the body, but only act on target
cells that are equipped to respond
Can turn on or off enzymes = may alter cellular metabolism
Local regulators secrete signals into interstitial fluid and
affects nearby cells
Pheromones carry messages between individuals of a species
Neurosecretory cells conduct nerve signals AND secrete
hormones into blood
E.g. epinephrine (adrenaline) as a ‘fight-or-flight’ hormone and
a s a neurotransmitter
Hormonal Signaling
2 major types of hormone molecules
Amino acid derived
Proteins, peptides, and amines
hydrophilic
Steroids
Sex hormones made from cholesterol (lipids)
Hydrophobic
All hormonal signaling has 3 events
Reception: hormone binding to a receptor protein or target cell
Signal transduction: coverts the signal from 1 form to another
Response: result or change in cell’s behavior
Target range is vast so 1 hormone may effect many or few targets
E.g. sex hormones most body tissues while glucagon liver and fat cells
only
Water-soluble Hormones
Receptors is PM of target
cells
Hormone binds to receptor
protein to activate it
Initiates a series of changes
in cellular proteins
Converts extracellular signal
to an intracellular one
Final relay molecule
activates a protein to evoke
the response
Lipid-soluble Hormones
Bind receptors inside the cell
Are small and nonpolar so can
diffuse through the PM
Binds a receptor protein in the
cytoplasm or nucleus
No signal pathway, self sufficient
Attaches to enhancer site on
DNA
Stimulates transcription and
translation
Steroid hormones turn genes on
or off
Focus on
hypothalamus and
pituitary gland
secretions
Also adrenal gland
and gonads
Connection of Brain Structures
The pituitary gland hangs on a stalk-like structure that
projects inferiorly from the hypothalamus
The hypothalamus monitors internal conditions and emotional
states
Controls anterior pituitary by secreting releasing and inhibiting hormones
The pituitary gland has 2 distinct parts with different roles
Anterior pituitary
Endocrine cells that synthesize and secretes numerous hormones into
the blood
Control activity of other endocrine glands
Posterior pituitary
Bundle of nervous tissue that stores and secretes 2 hormones made in
the hypothalamus
Review positive and negative feedback
Posterior Pituitary
Hypothalmus to posterior
pituitary connection is direct
Oxytocin: uterine
contractions during childbirth
and milk letdown during
nursing
Antidiuretic hormone:
acts on walls of kidney
tubules to control body’s
water and solute levels
Anterior Pituitary
Hypothalmus to anterior
pituitary connection is
through blood vessels
Feedback controls the
secretion of these
hormones
Growth Hormone (GH)
Promotes protein synthesis and the use of body fat for
metabolism in a variety of target cells
In young mammals encourages development and
enlargement of the body
Too much or too little causes developmental problems
depending on stage on development of occurrence
Can be made artificially now by bacteria that carry the gene
Used to counter deficiencies in youth
Abused by athletes to bulk up
Can lead to heart failure, cancers, or disfigurement
Thyroid Regulation
Thyroid affects almost every tissue in the body by producing
2 amine hormones, both containing iodine (I)
Throxine (T4)
Triiodothyronine (T3)
Same effects on different target cells
Crucial for development and maturation
Maintain normal blood pressure, heart rate, and digestion
Increase rate of O2 consumption = what effect on metabolism?
Excess or insufficient amounts can have adverse health effects
E.g. hypothyroidism: weight gain, intolerance to cold, lethargy
Pancreatic Hormones
The pancreas produces insulin and glucagon to help
manage the body’s energy supply
Islets of Langerhans with beta (insulin) and alpha (glucagon)
cells
Antagonisitc hormones that regulate glucose levels
circulating in the blood
Glucose Homeostasis
o Glucose up =
insulin up = cells
store/take up
more glucose
until return to
normal
o Glucose down
= glucagon up =
liver break
glucagon into
glucose until
return to normal
Diabetes Mellitus
When cells can’t absorb glucose from blood
Develops when not enough insulin or cells don’t respond to
insulin
Cells starved for fuel so begin burning fats and proteins
Glucose absorbed by digestive system so concentration in urine is
high
Treatments but no cure
Blindness, dehydration, kidney and cardiovascular disease occur
Type 1 (insulin dependent)
Autoimmune disease: WBC’s attack beta cells
Type 2 (non-insulin dependent)
Onset is older and often associated with obesity
Gestational diabetes
Can effect any pregnant woman
Adrenal Glands
Paired structures atop the kidneys consisting of 2 parts
Each contains different cells and produce different hormones
Both respond to stress
Adrenal medulla produces ‘fight-or-flight’ response
Short term response
Produces epinephrine (epi) and norepinephrine (nor) to cause
Responds to nerve signals from the hypothalamus
Adrenal cortex
Slower, longer lasting responses
Produces corticosteroids (2 types)
Responds to endocrine signals
Adrenal Medulla
Nerve cells in
hypothalamus respond to
(+)or (–) stress stimuli
Signals via spinal cord to
adrenal medulla to release
epi or nor into blood
Prompts multiple rxns
Liver releases glucose
Raise blood pressure,
breathing and metabolic
rates
Change blood flow
patterns
Adrenal Cortex
Hypothalamus secretes
releasing hormone to
anterior pituitary to release
adrenocorticotropic
hormone (ACTH)
Adrenal cortex releases
corticoids
Mineralocorticoids
Reabsorb salt and H20 to
increase blood volume and
pressure
Glucocorticoids
Increase glucose production
from fats and proteins
Suppresses immune system
(inflammatory response)
Cortisone injections
Sex Hormones
Steroid hormones that affect growth and development as well
as regulate reproductive cycles and sexual behavior
Gonads or sex glands secrete sex hormones and produce
gametes
3 main types found in both males and females, but ratio differs
Estrogens
Maintain female repro. system and development of female features
Progestins (progesterone)
Prepare and maintain uterus to support an embryo
Androgens (testosterone)
Maintain and stimulate development of male repro. System
Synthesized by gonads in response to releasing factor from
hypothalmus to anterior pituitary to secrete FSH and LH
Hormones Vary Between Species
Prolactin is secreted by the anterior pituitary
Humans
Stimulates mammary glands to grow and produce milk during
pregnancy
Prevents ovaries from releasing eggs, decreasing the chances of a
pregnancy while breast feeding
Evolutionary adaptation to ensure adequate care to newborns possibly
Birds
Stimulates nestbuilding, regulates fat metabolism, and reproduction
Amphibians
Stimulates movement toward water in preparation for breeding and
affects metamorphosis
Fish
Regulate salt and water balance in fish that move between fresh and
salt water