Download INTEGUMENTARY SYSTEM

ENDOCRINE SYSTEM
General Overview
Major Control System
Ductless Glands; Produce Hormones
Diffuse into Blood
Slow Initial Effects, but Effects Persist
much longer
Hormones act on specific Targets
Regulated by Negative Feedback
Classification of Glands
Endocrine – ductless
glands that secrete
hormones into the blood
stream
Exocrine – ducted
glands that secrete their
products onto a surface
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
There are Two Types of
Hormones
Steroid Hormones (cholesterol based)
- Attach to intracelluar receptor
- Directly activate genes
Non-steroid Hormones (amino acid
based)
- Attach to receptor on plasma membrane
- A second messenger forms inside the cell to
change cell’s activity
Mechanisms of Hormone Action
Steroids (Synthesized from Cholesterol)
- Hormone enters cell
- Hormone forms complex with receptor
- Complex binds to DNA in nucleus
- Transcription of mRNA
- New protein is synthesized in cytoplasm
(Translation)
- E.g. Testosterone
Mechanisms of Hormone Action
continued
Non-Steroids (Proteins/Peptides/Amine)
- Hormone does not enter cell & acts as
1st messenger
- Hormone binds to receptor on cell
membrane
- Enzyme is activated
- 2nd messenger is produced inside cell
- 2nd messenger affects cell function
- E.g. Pituitary hormones
How do Cells Respond to
Hormones?
Precise response depends on target cell
type
 or  rates of normal cellular processes:
- Activates/deactivates enzymes
- Stimulates protein synthesis
- Opens/closes ion channels
- Stimulates mitosis
What Stimulates Endocrine
Glands?
Hormonal
- Tropic hormones alter activity of other
endocrine glands
- Most common
Humoral (Chemical)
- Changing levels of ions or nutrients
trigger release of hormones
Neural
- Nerve Impulses stimulate hormone
release
What if Hormone Levels are too
High or too Low?
Cells can change the number of receptors
they have:
- 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
Endocrine Organs
Hypothalamus
Pituitary
- Anterior
- Posterior
Thyroid Gland
Parathyroid Glands
Adrenal Glands
- Cortex
- Medulla
Pancreas
Pineal Gland
Thymus
Gonads
Hypothalamus
Controls anterior pituitary
- Releasing hormones stimulate secretion
- Antagonistic Inhibiting hormones
- Portal system carries hormones to Anterior
Pituitary
Secretes & stores hormones in posterior
pituitary (neural tissue carries & stores)
Neurally stimulates adrenal medulla (Master
controller of ANS)
Pituitary Gland
Attached to Hypothalamus via
infundibulum
Protected by sella turcica of sphenoid
Divided into 2 lobes:
- Anterior (glandular)
- Posterior (neural)
Anterior Pituitary
“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 Hormones
Human Growth Hormone (GH)
- Target: All/Most Body Cells (esp. Bone &
Muscle)
- Action: Promotes Growth & Repair
Prolactin (PRL)
- Target: Mammary tissue
- Action: Promotes milk production
Anterior Pituitary continued
Thyroid Stimulating
Hormone/Thyrotropic Hormone (TSH)
- Target: Thyroid Gland
- Action: Stimulates production of
Thyroid Hormone
Anterior Pituitary continued
 Adrenocorticotropic Hormone (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:
Produce sex hormones
Prepare uterus for implantation
Develop corpus luteum in ovary
Posterior Pituitary
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:
Conserves water (decreases urine
volume)
Raises blood pressure
Thyroid Gland
Thyroid Hormone
- T3 (Triiodothyronine), T4 (Thyroxine)
- Target: All body cells
- Action:
*Increase metabolic rate
*Regulate body temperature
*Influence development
Thyroid Gland
Calcitonin
- Target: Bone/Osteoclasts
- Action:
*Inhibit osteoclasts
*Increase Ca2+ deposition in bone
*Decrease blood Ca2+
Parathyroid Glands
Parathyroid Hormone
- Target: Bone/Osteoclasts
- Action:
*Stimulate osteoclasts
*Stimulate bone resorbtion
*Increase absorption from urine &
small intestine
*Increase blood Ca2+
Adrenal Glands
 Adrenal Cortex (outer/glandular)
- Cortisol
* Target: Many tissues
* Action: make glucose, decrease
inflammation
- Aldosterone
* Target: Kidneys
* Action: Increase blood Na+ & water;
decrease blood K+
Adrenal Glands continued
Adrenal Medulla (inner/nervous)
- Epinephrine/Adrenalin (Fear/Flight)
- Norepinephrine/Noradrenalin
(Anger/Fight)
- Target: Heart, Liver, Muscles, Blood
Vessels, etc.
- Action: Intensify sympathetic responses
(threat response)
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Pancreas
Glucagon
*Target: Liver
*Action: Glycogen breakdown;
raises blood glucose
Insulin
*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 biological rhythms & 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