Download INTEGUMENTARY SYSTEM

ENDOCRINE SYSTEM
Endocrine - General
Major Control System of Homeostasis
Negative Feedback
Ductless Glands; Produce Hormones
Diffuse into Blood
Slow Initial Effects, but Effects Persist
much longer
Hormones act on specific Targets
Classification of Glands
Endocrine – ductless
glands that secrete
hormones into the blood
stream
Exocrine – ducted
glands that secrete their
products onto a surface
Hormones – Definition
Definitions
- Literal: To spur on, to set in motion
- Physiological: A chemical messenger
that affects another tissue or organ
(the target)
Hormones - General Function
Modify activity of
target cells
Targets have
specific receptors
for the particular
hormone
Distributed by
blood
Location of Receptors
Cell Surface
- cell membrane
Intracellular
- Cytoplasm
- Nucleus
Mechanisms of Hormone Action
Steroids (Synthesized from Cholesterol)
-
Hormone enters cell
Hormone forms complex with receptor
Hormone/receptor complex enters nucleus
Complex binds to DNA
Protein synthesis occurs
Protein alters cell function (i.e. produces the
effect)
- E.g. Testosterone
Mechanisms of Hormone Action
continued
 Non-Steroids (Proteins/Peptides/Amine)
Hormones
- Hormone does not enter cell
- Hormone is 1st messenger
- Hormone binds to receptor on cell
membrane
- Triggers formation of 2nd messenger (cyclic
AMP)
- 2nd messenger alters cellular activities (i.e.
produce the effect)
- E.g. Pituitary hormones
Regulation by Receptors
Changeable Number of receptors on target
- Up Regulation
* Low hormone levels
* Number of receptors increases
* Target’s responsiveness increases
- Down Regulation
* Excess hormone levels
* Number of receptors decreases
* Target’s responsiveness decreases
Secretion Stimuli
Hormonal
- Tropic hormones regulate activity of
other endocrine glands
- Most common
Humoral
- Changing levels of ion or nutrients
trigger release of hormones
Neural
- Stimulated by nerve fibers
Hormonal Stimuli
of Endocrine
Glands
 Endocrine glands
are activated by
other hormones
Figure 9.2a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 9.11
Humoral Stimuli of
Endocrine Glands
 Changing blood
levels of certain
ions or nutrients
stimulate hormone
release
Figure 9.2b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 9.12
Neural Stimuli of
Endocrine Glands
 Nerve impulses
stimulate hormone
release
 Most are under
control of the
sympathetic nervous
system
Figure 9.2c
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 9.13
Endocrine Organs
Hypothalamus
Pituitary
- Anterior
- Posterior
Thyroid Gland
Parathyroid Glands
Adrenal Glands
- Cortex
- Medulla
Pancreas
Pineal Gland
Thymus
Gonads
Hypothalamus
Integrates Nervous System & Endocrine
Portal Circulation carries hormones to
Anterior Pituitary
Releasing Factors (hormones) stimulate
secretion by Anterior Pituitary
Inhibiting Factors (hormones) are
antagonistic to Releasing
Nervous tissue carries hormones to
Posterior Pituitary
Pituitary Gland
Attached to Hypothalamus via
infundibulum
Protected by sella turcica of sphenoid
Divided into 2 lobes:
- Anterior (glandular)
- Posterior (neuroendocrine)
Anterior Pituitary
(Adenohypophysis)
“Master Gland” (makes & secretes various
tropic hormones)
Tropic Hormones
- Act on other Endocrine Glands
- Serve as Hormonal Stimuli
- Stimulate release of another hormone
Anterior Pituitary
(Adenohypophysis)
- Human Growth Hormone (GH):
*Target: All/Most Body Cells (esp.
Bone & Muscle)
*Action: Promotes Growth & Repair,
*Increases Blood Glucose
- Prolactin (PRL):
*Target: Mammary Tissue
*Action: Promotes milk secretion
Anterior Pituitary continued
Thyroid Stimulating Hormone (TSH)
- Target: Thyroid Gland
- Action: Stimulates production of
Thyroxine
Anterior Pituitary continued
 Adrenocorticotropic Hormones (ACTH)
- Target: Adrenal Cortex
- Action: Controls production/secretion adrenal
cortex hormones
 Gonadotropic Hormones
- Follicle Stimulating Hormone (FSH)
* Target: Gonads (Ovaries/Testes)
* Action: Production of gametes & sex
hormones
Anterior Pituitary continued
- Luteinizing Hormone (LH/ICSH)
*Target: Gonads
*Functions:
Production of sex hormones
Prepare uterus for implantation
Develop corpus luteum
Hormones of the Anterior Pituitary
Figure 9.4
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 9.17
Posterior Pituitary
(Neurohypophysis)
Does NOT synthesize Hormones
Neural rather than glandular
Stores & Releases two hormones produced
by hypothalamus
- Oxytocin
*Target: Uterus & Mammary Glands
*Action: Stimulates Contractions to
eject fetus & milk
Posterior Pituitary continued
- Antidiuretic Hormone (ADH) also called
vasopressin
*Target: Kidneys
*Action:
Conserve Water (decrease urine
volume)
Increase BP
Hormones of the Posterior Pituitary
Figure 9.5
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide
9.22b
Thyroid Gland
Thyroid Hormone
- T3 (Triiodothyronine), T4 (Thyroxine)
- Target: Most body cells
- Action: Increase metabolic rate, regulate
body temperature
Calcitonin
- Target: Bone/Osteoclast Inhibition
- Action: Decrease blood Ca2+
(Hypocalcemia if excessive)
Parathyroid Glands
Parathyroid Hormone
- Target: Bone/Stimulation of Osteoclasts
- Action: Increase blood Ca2+
(Hypercalcemia if excessive)
Parathyroid Glands
 Tiny masses on
the posterior of
the thyroid
 Secrete
parathyroid
hormone (PTH)
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 9.26
Adrenal Glands
 Adrenal Cortex (outer/glandular)
- Cortisol
* Target: Many tissues
* Action: make glucose, decrease
inflammation
- Aldosterone
* Target: Kidneys
* Action: Maintain Na+/K+ blood levels
Adrenal Glands continued
Adrenal Medulla (inner/nervous)
- Epinephrine/Adrenalin (Fear/Flight)
- Norepinephrine/Noradrenalin
(Anger/Fight)
- Targets:Heart, Liver, Muscles, Blood
Vessels, etc.
- Functions: Prepare for sudden threat
Pancreas
Endocrine (Islets of Langerhans) &
Exocrine
Glucagon (from Alpha Cells)
- Target: Liver
- Action: Release glucose from glycogen
(increases blood glucose)
Insulin (from Beta Cells)
- Target: Most/All Cells
- Action: Promotes glucose transport into
cells (decreases blood glucose)
Pineal & Thymus Glands
 Pineal Gland (Endocrine & CNS)
- Melatonin
* Target: Hypothalamus
* Action: Sets Diurnal Clock/Circadian rhythm
& promotes sleep
 Thymus (atrophies at puberty)
- Thymosins
* Target: T cells of immune system
* Action: T cell maturation
(immunocompetence)
Gonads
 Ovaries
- Estrogen
* Target: Uterus, Ovaries, other
* Action: prepare for fetus, secondary sexual
characteristics
- Progesterone
* Target: Uterus
* Action: maintains pregnancy, prevents
uterine contractions
Gonads continued
Testes
- Testosterone
*Target: Various body parts
*Action: Secondary sexual
characteristics