Download Bio 257 Day 23

Bio 257 Day 23
Today’s topic
 Ch 10 Endocrine System
Objectives:
• Define endocrine gland,
hormone and target tissue.
• List the chemical types of
hormones
• Characterize control of hormone
secretions.
Objectives:
• Describe the structure of the
pituitary gland, thyroid gland,
parathyroid glands, pancreas,
and adrenal glands.
Objectives:
• List hormones, describe
their actions and name the
target tissues of the major
endocrine glands.
• Organs:
–Endocrine glands = ductless
glands, which secrete hormones
into body fluids (blood)
Similarity and Differences b/w
Nervous and Endocrine Systems
control over
organs it is in
direct contact with
indirectly affect
many organs of
the body at a
distance by
secreting
chemicals into
the blood
• General Function of the Endocrine System:
– Coordinates & regulates body systems
to maintain homeostasis
• Organs:
–Hormone(s) = organic
compound, that exerts
specific effects on certain
organs (target organs) at
some distance away
Hormone receptors
Sites on or in the target
tissue (organ) to which a
chemical (e.g. hormone) binds to
similar to a lock-n-key.
Receptors
• Membrane-Bound Receptor Responses
– Alter membrane permeability by directly opening or
closing membrane channels
– Activate G proteins that in turn can open or close
membrane channels or activate enzymes that
produce intracellular chemical signals (2nd
messenger)
– Alter the activity of enzymes directly leading to an
increase or decrease in the level of intracellular
chemical signals or add phosphate groups to cellular
proteins
Polar hormone in blood
Cytoplasm
ATP
E
receptor
Receptors
• Intracellular receptors:
– Located in the cytoplasm or nuclei
– Regulate the synthesis of specific messenger
RNA moleculesProtein Synthesis
Lipid Soluble Hormone
Overview of
Types of Chemical Signals
• Intracellular- produced in one part of a cell
and travel to another part of the same cell
and bind to either cytoplasmic or nuclear
receptors.
– Often produced at the level of the cell
membrane
Overview of
Types of Chemical Signals
• Intercellular chemical signals
– Autocrine- released by cells and have a local
effect on the same cell or cell type
eicosanoids released from smooth muscle
and platelets lead to blood vessel dilation and
platelet aggregation
– Paracrine- released by cells that have effects
on other cell types near the cells from which
they are released (e.x. somatostatin inhibits
release of insulin in the pancreas)
Overview of
Types of Chemical Signals
• Intercellular chemical signals
– Neuromodulators and neurotransmitters-secreted by
nerve cells function in the nervous system
– Pheromones-secreted into the environment may
modify the behavior and physiology of other
individuals (pheromones produced by humans not
fully understood)
– Hormones-secreted by endocrine glands into the
circulatory system, transported and act on tissues
distant from the site of release in a specific way
• Neurohormones-hormones secreted from cells of the
nervous system
Localized chemical signal
Hormone
Hormone Effects on Target
Organs
REGULATE:
• Growth
• Stress
• pH of body
• Reproduction system
• Use of food sources (metabolism)
• Water Balance
• Uterine contractions/milk release
• Heart rate and blood glucose control
• Immune system
Chemistry
of Hormones
• 2 classes:
– Synthesized from amino acids (AA)
• Proteins or peptides (insulin, ADH, oxytocin)
• Thyroid hormones derived from AA Tyrosine (throxine,
triiodothyronine)
• Amines (catecholamines) epinephrine and
norepinephrine)
– Epinephrine released from the adrenal medulla (ie
(Endocrine fxn)
– Norepinephrine released more from neurons (not much
from adrenal medulla)
– Synthesized from cholesterol
• Steroids (lipid-like) cortisol, estrogen, testosterone
Mechanism of
Hormone Action
1. Hormones are released on
demand and determined by
the body’s need
2. Hormone’s principle
action site is its target
tissue or organ.
3. The target tissue
contains specific
receptors, which the
hormone binds.
4. Hormones only affect
those organs w/ the
specific target receptor
5. When a hormone binds to
its target tissue receptor,
a chain of events are
produced that alter
the target cell activities
Polar Hormone
Polar Hormone
Polar Hormone
Polar Hormone
Control of HormoneSecretions
• 3 Mechanisms control secretion
of hormonesall use negative
feedback
1.Hypothalamus/anterior pituitary
2.Nervous system
3.Glands responding to changes
in internal environment
How do hormones work?
• Negative feedback mechanisms
–Effects of the hormone on the
target gland are “fed back” to the
endocrine gland which then
decreases the secretion of that
hormone
How do hormones work?
• Many work together = synergistic
effects (synergism)
• Many work in opposition = antagonistic
effects (antagonism)
• Hypersecretion = oversecretion of
hormone
• Hyposecretion = under secretion of
hormone
Pituitary Gland
• Sits in sella turcica
• Extends from hypothalamus
• Consist of 2 lobes (anterior lobe
& posterior lobe)
Pituitary gland
Relationship of Hypothalamus to
Pituitary gland
anterior lobe
infundibulum
posterior lobe
Posterior Pituitary
Hypothalamus/Posterior Pituitary
1. Neural stimulation of hypothalamic neurons
2. AP carried by axons from hypothalamus
to posterior pituitary. The neuron terminal
in the posterior pituitary stores hormones
3. AP cause the release of hormones from the
axons into the circulatory sytem
4. The hormones pass through the circulatory
system and influence the activity of their
target tissue
Posterior Lobe of Pituitary
Gland
• 2 hormones (peptide)
1. Oxytocin
 stimulates contraction of uterine
smooth muscle
 Stimulates milk ejection or milk
let-down from mammary glands
– target: uterus & mammary
glands
Posterior Lobe of Pituitary
Gland
• 2 hormones (peptide)
2. ADH (antidiuretic hormone or
vasopressin) = increases
reabsorption of water by kidneys
resulting in decreased urine
output (ie less water lost as urine)
target: kidneys
Anterior Pituitary
Anterior Pituitary Hormones
MSH
Melanocytes
in skin
Anterior Lobe of Pituitary Gland
• Hormones are called tropic
hormones
• 7 hormones
Anterior Lobe of Pituitary Gland
1. GH (growth hormone)
–stimulates growth (increase in
cell size & mitosis) by increasing
protein synthesis
–Increases breakdown of
lipidsincrease in free fatty acids
–Increases blood glucose levels
• target: most body tissues,
Anterior Lobe of Pituitary Gland
2. TSH (thyroid stimulating
hormone)
–stimulates thyroid gland hormone
secretions & growth
target: thyroid gland
Regulation of Thyroid Hormone
Secretion
Anterior Lobe of Pituitary Gland
3. ACTH (adrenocorticotropic
hormone)
–stimulates adrenal gland (cortex)
secretions
• Glucocorticoids  cortisol
target: adrenal cortex of adrenal
gland
Regulation of Cortisol Secretion
Anterior Lobe of Pituitary Gland
4. Prolactin
–stimulates milk production by
mammary glands
–prolongs progesterone secretion
following ovulation/during
pregnancy
target: mammary glands/ovaries
Anterior Lobe
Gonadotropins = hormones
whose target organs are gonads
5. FSH (follicle-stimulating
hormone)
 stimulate the production of gametes
(sperm cells & oocytes) & estrogen
target:
 ovariesfollicles in ovary
 testisseminiferous tubules
Anterior Lobe
Gonadotropins
6. LH (luteinizing hormone)
 stimulates the releases of egg
(oocyte) from ovary (ovulation) and
progesterone production in ovary.
 testosterone production from testis
target: ovaries & testis
Anterior Lobe
7. MSH (melanocyte stimulating
hormone)
 stimulates production of melanin
by melanocytes
 makes the skin darker
Pineal Gland
• Between cerebrum &
cerebellum (epithalamus)
• 1 hormone:
melatonin = regulates sleep wake
cycles, produced at night.
may prevent onset of puberty
higher amounts in preadolescence children
larynx
isthmus
thyroid
gland
trachea
Thyroid Gland
• Lateral to trachea & inferior to
larynx (neck)
• 2 lobes connected by narrow
band of tissue (isthmus)
• 3 hormones (thyroxine-T4,
triiodothyronine-T3, & calcitonin)