Nervous System vs Endocrine System
Nervous System
Endocrine System
Nt’s act on a specific cell
right next to it
Hormone can act on
nearby cell or cell in
another part of body
Nt’s have their effects
within milliseconds
Hormones have effects in
minutes or days
Effects of Nt’s are shortlived
Effects of Nt’s can last
hours, days or years
Endocrine vs Exocrine Glands
Exocrine Glands
Endocrine Glands
Secrete products into
ducts
Secrete products into
extracellular fluid
Secretions go into body Secretions (hormones)
cavities, lumen of organ act on nearby cell or
or body’s surface
more commonly go into
blood vessels to act on
cell in another part of
body
E.g. sweat glands,
E.g. pituitary gland,
lacrimal glands,
thyroid gland,
sebaceous glands, etc pancreas, etc.
Endocrine Glands
• Ductless
• Produce chemical
messenger
• Hormone released into blood
stream
Exocrine Glands
• Have ducts
• Produce a variety of substances
(sweat, oil, enzymes)
• Release chemicals through
ducts
What makes a hormone a
hormone?
• 1.
• 2.
Secreted by endocrine gland
Released into circulatory
system
• 3. Travels to and acts on
specific target cells.
Major Endocrine Glands
Classification of Hormones
• Steroid Hormones – fat soluble, made
from cholesterol.
• Ex. Sex hormones
Non-Steroidal Hormones
• Protein Hormones – made from amino
•
acids, usually from tyrosine, smaller than
steroid hormones.
Peptide Hormones- chains of amino acids
• Very diverse group
•
The major categories of nonsteroid hormones are protein
hormones, glycoprotein
hormones, peptide hormones,
and amino acid derivative
hormones.
Classification of Hormones
3 major types of hormones:
1. Amino Acid Derivatives
2. Peptide Hormones
3. Lipid Derivatives
Protein Hormones
• Much faster action than
steroid hormones
• Do not enter the target cell
• Ex. Adrenalin
Mechanisms of Action (How Hormones Work)
Second Messengers:
Genes:
Hypothalamus
• Location:
•
•
•
Diencephalon
Structure:
Neurons and
neuroglia
Hormones:
Releasing
hormones, ADH,
oxytocin,
Direct action on
adrenal medulla
Hypothalamic Control of Hormone Secretion
from the Adenohypophysis
Hypothalamus regulates secretion of
hormones
• Secretes releasing factors to
release hormones
• Secretes inhibiting hormones to
turn off secretion of hormones
Hypothalamus Relationship to Anterior &
Posterior Pituitary
Hypothalamus Summary
The Pituitary Gland (Hypophysis)
• Secretes nine major hormones
• Attached to the hypothalamus by
•
the infundibulum
Two basic divisions of the pituitary
gland
• Anterior pituitary gland
• Posterior pituitary gland
The Pituitary Gland
Figure 25.3a-c
Anterior Pituitary Gland
• Location: Attached
•
•
to hypothalamus
by infundibulum
Structure:
endocrinesecreting cells
Hormones: Tropic
Hormones (ACTH,
TSH, FSH, LH)
and GH, PRL,
MSH
Posterior Pituitary Gland
•
•
•
Location: Attached to
hypothalamus by
infundibulum
Structure: Axons that
extend from the
hypothalamus
Releases (does not
make) two hormones
• Antidiuretic hormone
•
(ADH)
Oxytocin
The Thyroid Gland
• Location:
•
•
anterior neck
Structure:
Follicles and
areolar
connective
tissue
Hormones:
thyroid hormone
(TH) and
calcitonin
The Thyroid Gland
The Parathyroid Gland
• Location:
•
•
Posterior
surface of the
thyroid gland
Structure:
endocrine cells
Hormones:
Parathyroid
hormone
•
The parathyroid hormone helps maintain
calcium homeostasis. It acts on bone, kidney,
and intestinal cells to increase the release of
calcium into the blood.
The Adrenal Gland
The Adrenal Glands
•
•
•
•
•
Location: Superior surface of the kidneys
Structure: Inner adrenal medulla and outer
adrenal cortex
Nerve supply is almost exclusively sympathetic
fibers
Hormones in Adrenal Cortex: Glucocorticoids
(e.g. cortisol, corticosterone, and cortixon),
Mineralocorticoids (e.g. aldosterone), and
androgens
Hormones in Adrenal Medulla: Epinephrine and
norepinephrine
The Adrenal Cortex
Figure 25.9a
•
Antidiuretic hormone acts to reduce the
volume of urine. It does this by causing water
to be reabsorbed from the tubules of the
kidney and returned to the blood. This
increases the water content of the blood and
reduces the volume of urine.
The Pancreas
•
•
•
Location: Posterior
abdominal wall
along duodenum
Structure: Both
endocrine and
exocrine cells
(secrete digestive
enzymes)
Hormones:
Glucagon and
insulin
•
Alpha cells in the pancreatic islets produce
glucagon. Beta cells produce insulin. Delta
cells produce somatostatin, and pancreatic
polypeptide cells produce pancreatic
polypeptide.
Glucagon and Insulin
Diabetes Mellitus
•
•
This is a disease caused by elevated glucose levels
2 Types of diabetes:
Type I diabetes (10% of cases)
Type II diabetes (90% of cases)
Type I Diabetes (10% of cases)
• Develops suddenly, usually
before age 15
• Caused by inadequate
production of insulin because T
cell-mediated autoimmune
response destroys beta cells
• Controlled by insulin injections
Type II diabetes (90% of cases)
• Usually occurs after age 40 and in
obese individuals
• Insulin levels are normal or
elevated but there is either a
decrease in number of insulin
receptors or the cells cannot take it
up.
• Controlled by dietary changes and
regular exercise
Pituitary Disorders
•
•
•
Gigantism – hypersecretion of GH in children
Pituitary dwarfism – hyposecretion of GH
Diabetes insipidus – pars nervosa does not
make enough ADH
Disorders of the Thyroid Gland
•
Grave’s disease – most common type of
hyperthyroidism
• Immune system makes abnormal antibodies
• Stimulates the oversecretion of TH by follicle
cells
• Leads to nervousness, weight loss, sweating,
and rapid heart rate
Disorders of the Thyroid Gland
•
Myxedema – adult hypothyroidism
• Antibodies attack and destroy thyroid tissue
• Low metabolic rate and weight gain are
common symptoms
•
•
Endemic goiter – due to lack of iodine in the
diet
Cretinism – hypothyroidism in children
• Short, disproportionate body, thick tongue and
mental retardation
Disorders of the Adrenal Cortex
•
•
Cushing’s syndrome – caused by
hypersecretion of glucocorticoid hormones
Addison’s disease – hyposecretory disorder
of the adrenal cortex
• Deficiencies of both mineralocorticoids and
glucocorticoids
Control of Hormones Release:
Three Mechanisms
Figure 25.2a-c
•
Oxytocin has two positive feedback mechanisms
associated with it. The first is the release of milk. The
mechanical and psychological stimulation of the baby's
suckling triggers the release of oxytocin. This provides
more milk, which allows the baby to continue to suckle,
which in turn stimulates the release of more oxytocin.
The other feedback mechanism is the stimulation of
uterine contractions. Once uterine contractions begin,
they push down on receptors in the pelvis, which
triggers the release of more oxytocin, which causes
more uterine contractions.