Download Brain Hormone

Hormones and the Endocrine
System
By Elizabeth Chapman, Alec Smith, and
Niki Williams
Hormones and the Endocrine System
Key Points of Focus:
• Nervous system relationship
• Maintenance of homeostasis
• Types of hormones/effects on vertebrates
• Effect on invertebrates
Review and Overview
• The Endocrine System is composed of all of the body's hormone
secreting cells
• Hormones are chemical signals carried by the circulatory
system that communicate regulatory messages through the body
• One hormone can elicit a variety different responses from different
target cells
• There are 3 simple hormonal pathways
1.Simple endocrine
2.Simple neurohormone
3.Simple neuroendocrine
The Three Simple Pathways
Review of Hormonal Signaling
• Hormonal signaling occurs through the binding of a receptor
protein to a target cell:
1.Water-soluble hormones bind to plasma membrane, triggering a
signal transduction pathway
2. Lipid-soluble hormones bind to an intracellular receptor
(Either the cytoplasm or nucleus), where it acts as a
transcription factor
Water-Soluble
Hormone
Lipid-Soluble
Hormone
Hormone binds to
receptor on plasma
membrane
Hormone binds
to intracellular
receptor either
in the nucleus
(as shown) or
the cytoplasm
Triggers signal
transduction
pathway; leads to
response
Signal-receptor
complex acts as a
transcription factor
Review of Hormone Signaling
Anterior and Posterior Pituitary
posterior pituitary:
• stores/secretes two
hormones made
by hypothalamus
1. ADH
2. Oxytocin
anterior pituitary:
• synthesizes/secretes
hormones;
• four are tropic (regulate
function of other endocrine
organs)
• others nontropic
• growth hormone
Anterior Posterior Hormones
Growth Hormones
• release insulin-like growth factors which circulate in the blood
to stimulate bone/cartilage growth
• hypersecretion leads to gigantism
• hyposecretion leads to dwarfism
Thyroid Gland
• Two lobes on trachea
• Maintain homeostasis (blood pressure, heart rate, muscle tone,
and digestion)
• Affected by iodine in diet
Control of Blood Glucose
Pancreas:
• produces bicarbonate ions and
digestive enzymes
• carried to small intestine via
pancreatic duct
Exocrine: tissues and glands that
discharge secretions into ducts
Islets of Langerhans: clusters of
endocrine cells (in exocrine tissue of
pancreas
Blood glucose regulated by glucagon
and insulin
Glucagon
• Raises Blood Glucose Levels
• From alpha cells
• Promotes liver's glycogen breakdown and release of glucose
• Only liver cells are responsive to glucagon
• Fat cells convert sugars to fats
• Skeletal muscles use released glucose
for use in exercise
COOKIES
Insulin
• Lowers Blood Glucose Levels
• From beta cells
• Slows liver's glycogen breakdown
• Inhibits conversion of amino acids and glycerol to glucose
• Promotes uptake of glucose by most somatic cells and synthesis and
storage
Glucose Homeostasis (blood glucose regulation)
When blood glucose is too
HIGH
insulin is released to lower
blood sugar concentration
When blood glucose is too
LOW
>glucagon is released to
increase blood glucose
concentration
Diabetes Mellitus
Type 1: Insulin Dependent (usually
children)
• Immune system destroys
pancreas's beta cells which
produce insulin
Type 2: Non Insulin
Dependent (anyone, yet obese
susceptible)
• deficiency of insulin or reduced
responsiveness of target cells
from change in insulin receptors
Calcium Homeostasis
Too much calcium:
thyroid gland releases calcitonin
which is deposited in bones;
reduces kidney absorption
Too little calcium:
parathyroid glands (on thyroid)
release PTH, take calcium from
bones, increase absorption from
kidneys
Adrenal Hormones: Response to Stress
Adrenal Cortex: (outer)
-made of true endocrine cells
Adrenal Medulla: (center)
made of secretory cells
-secretes catecholamines
Catecholamines: act directly on
target tissues for a bioenergetic
boost
Catecholamines: Epinephrine and
Norepinephrine
Positive or negative stress: catecholamines released by adrenal medulla
Epinephrine(adrenaline)- heart and metabolic rates
Norepinephrine(noradrenaline) - sustains blood pressure
Functions:
-increase rate of liver's glycogen breakdown
-promote glucose release by liver cells
-stimulate release of fatty acids from fat cells
Effects on Respiratory and Cardiovascular System
-increased rate of heart beat
-dilated bronchiloes in lungs, more oxygen to body
-smooth muscles contract, other relax, blood goes to heart brain
and skeletal muscles
Steroid Hormones from Adrenal Cortex
Adrenal cortex: endocrine signals cause hypothalamus to secrete
releasing hormone that stimulates anterior pituitary gland to release
tropic hormone ACTH, causes release of steroids
Corticosteroids:
Mineralocortecoids
-act on salt/water balance
ie:aldosterone
stimulates kidney cells to reabsorb
salt ions and water, raising blood
pressure and volume
Glucocortecoids
-breakdown of muscle proteins
-helps body with longterm
environmental changes
-anti-inflammatory, supresses
immune system
-carbon skeletons go to liver and
kidneys, converted to glucose,
released
Gonadal Sex Hormones
Androgens: (testosterone)
-stimulates development of male
reproductive system
-can determine gender of fetus
-PUBERTY
Estrogen:(estradiol)
-maintenance of female
reproduction system
-female secondary sex
characteristics
Progestins
(progesterone)
-prepares and
maintains uterus
Melatonin and Biorhythms
Pineal gland: small mass of tissue near center of brain
-sometimes has light sensitive cells that control secretory activity
-synthesizes and secretes MELATONIN
Melatonin regulates light/season changing /day length related
functions(ie: reproduction)
Invertebrate Regulatory System- Insects
Brain Hormone: made by
neurosecretory cells in brain
-stimulates release of ecdysone
Ecdysone: promotes molting and
development of adult
characteristics
Balanced out by:
Juvenile Hormone: promotes
larval characteristics
Overlap of Endocrine and Nervous Systems
• Specialized nerve cells called neurosecretory cells release
hormones into the blood via the extracellular fluid
• Some chemicals serve as both
o hormones in the endocrine system
o chemical signals in the nervous system
• Nervous system plays a role in regulating the secretion of certain
endocrine glands in certain sustained responses like the
reproductive cycles of many animals
Quick Note About Local Regulators
• Local regulators convey messages between neighboring cellsparacrine signaling
• Elicit quicker responses than long-distance endocrine signaling by
hormones
• The binding of a local regulator triggers events within the target
cell that are similar to those elicited by hormones
• Includes neurotransmitters, the key local
• regulators of the nervous system, growth factors,
• prostaglandins, and nitric oxide
Group Activity
• Get one set of notecards
• Use notecards to answer questions asked by
Alec, Elizabeth, or Niki
• First person to put up the correct notecard wins a
point
• Group that wins gets a random bag of stuff