Functions of Endocrine System
-Maintaining homeostasis of blood composition and volume
-Controlling reproductive activities
-Regulating development, growth, and metabolism
-Controlling digestive processes
Major Endocrine Glands
-Pituitary glands
-Adrenal glands
-Thyroid glands
Organs containing endocrine cels
-Hypothalamus
-Skin
-Thymus
-Heart
-Liver
-Stomach
-Pancreas
-Small Intestine
-Kidney
-Gonads
Hormonal Stimulation
Release of a hormone in response to another hormone
Hormonal Stimulation: TSH
Thyroid Stimulating Hormone (TSH) released from anterior pituitary, stimulating thyroid gland to secrete thyroid hormone (TH) into capillary
Humoral Stimulation
-Release of a hormone in response to changes in level of nutrient or ion in the blood
-Act on target cells to offset further loss or eliminate excess
Humoral Stimulation: Insulin
Increased blood glucose stimulates pancreas to release insulin
Nervous System Stimulation
Release of a hormone in response to stimulation by the nervous system
Nervous System Stimulation: Epinephrine and Norepinephrine
Release of epinephrine and norepinephrine by adrenal medulla in response to sympathetic nervous stimulation
Steroid Hormone
-Lipid-soluble
-Formed from cholesterol
-Produced by gonads and adrenal cortex
-Ex. cortisol
Protein Hormone
-Water-soluble
-Consists of amino acid chains
-3 Subgroups: Polypeptides, Oligopeptides, Glycoproteins
-Ex. Parathyroid hormone
Biogenic Amine
-Water-soluble (except thyroid hormone)
-Derived from amino acid that is modified (ex. tyrosine)
-Ex. Norepinephrine
Lipid-Soluble Hormone
1. Unbound LSH diffuses readily through plasma membrane and binds with intracellular receptor, within cytosol/ or nucleus to from hormone-receptor complex
2. HRC binds with specific DNA sequence (hormone-response element)
3. Binding stimulates mRNA synthe
Water Soluble Hormones
1. Hormone binds to receptor and induces shape change to activate the receptor
2. G protein binds to activated receptor
3. GDP exchanged for GTP and G protein is activated
4. Activated G protein released from receptor and moves along the inside of the pla
Target Cells: Degree of Cellular Response
Have different number of receptors for same hormone
Bind varying number of same hormone simultaneously
May possess receptors for many different hormones
Response dependent on net effect
Fluctuations in Receptor Number
-Cells up-regulate receptors in response to reduced hormone concentration in the blood
-Cells down-regulate receptors in response to elevated hormone concentration in the blood
Synergistic Hormone Interaction
Hormones work together to produce greater effect
Permissive Hormone Interaction
First hormone allows action of second hormone
Antagonistic Hormone Interaction
One hormone causes opposite effect of another
Pituitary Gland Structure and Location
Lies inferior to hypothalamus
Housed within sella turcica of sphenoid bone
Connected to hypothalamus by thin stalk, infundibulum
Partitioned into anterior and posterior pituitary
Pituitary Gland Function
Has direct control over hormone release from pituitary gland
Has indirect control over hormone release from:
thyroid and adrenal glands, liver, and gonads
Hormones stored in posterior pituitary
Synthesized in hypothalamus by neurosecretory cells
Oxytocin
Antidiuretic hormone (ADH)
Oxytocin
produced by paraventricular nucleus
Antidiuretic hormone (ADH)
produced by supraoptic nucleus
Posterior Pituitary Hormone Secretion
Nerve signal sent from hypothalamus
Travels along hypothalamo-hypophyseal tract
Hormones released into bloodstream from posterior pituitary (pars nervosa)
Hormones of the Hypothalamus
Regulatory Hormones
Releasing hormones
Inhibiting Hormones
Regulatory Hormones
secreted into blood to regulate anterior pituitary hormones
Releasing hormones
stimulate secretion of specific anterior pituitary hormones
Inhibiting Hormones
deter secretion of specific anterior pituitary hormones
Anterior Pituitary Hormone Secretion
Specific hormones within hypothalamus
Travel through from primary plexus to secondary plexus
Controls hormones of anterior pituitary which reach target cells through the bloodstream
PRL
Prolactin
Acts on mammary glands to stimulate milk production
FSH and LH
Follicle-stimulating hormone and Luteinizing hormone
Act on gonads to stimulate development of gametes
ACTH
Adrencorticotropic Hormone
Acts on the adrenal cortex to cause release of corticosteroids
Growth Hormone Stimulus
-Age
-Time of Day
-Nutrient levels in the blood
-Stress and exercise
Growth Hormone Function
Increased protein synthesis, mitosis, cell differentiation, eps. in bone, muscle and cartilage, release of store nutrients in blood
Growth Hormone
-Hypothalamus release growth hormone-releasing hormone (GHRH) into hypothalamo-hypophyseal portal system
-Anterior pituitary then releases growth hormone (GH)
-GH stimulates hepatocytes to release insulin-like growth factor (IGF) into the blood
-GH and IG
Hyposecretion
Pituitary dwarfism
Hypersecretion
Gigantism
Thyroid Hormone Function
Adjusts basal metabolic rate of many cells; Stimulates other target cells and organs to meet additional ATP requirements
Increase cellular respiration enzymes within mitochondria, increase respiration rate, increased heart rate
Hyperthyroidism vs Hypothyr
T3
Triiodothyronine
most active form of thyroid hormone
T4
Tetraiodothyronine
much greater amount of T4 produced
Thyroid Hormone
-Hypothalamus release thyrotropin-releasing hormone (TRH) into the hypothalamo-hypophyseal portal system
-Then Anterior pituitary releases TSH
-TSH stimulates thyroid gland to release TH into the blood
-TH acts in target cells
-TH levels inhibit TRH and T
Cortisol Function
Increase nutrient levels in blood
Attempts to resist stress and repair injured tissue
Cortisol Stimulus
-Negative feedback from cortisol
-Time of day
-Stress
Cortisol
-Hypothalamus release corticortropin-releasing hormone (CRH) into the hypothalamo-hypophyseal portal system
-Then anterior pituitary gland release adrenocorticotropic hormone (ACTH)
-ACTH stimulates adrenal cortex to release glucocorticoid into blood
-Cor
Liver cells effects
Increased gluconeogenesis
Decreased glycogenolysis and gluconeogenesis
Adipose tissue effects
Decreased lipogenesis
Increased lipolysis
Adrenal Medulla
Sympathetic preganglionic axons stimulate adrenal medulla to release epinephrine and norepinephrine
Enhance and prolong effects of sympathetic neurotransmitters
Pancreas
-Produces insulin and glucagon hormones
-Hormones regulates blood glucose concentration (70 to 100 mg glucose/deciliter)
-High glucose - damage blood vessel and kidneys
-Low glucose - lethargy, physical impairment, death
Insulin
-Beta cells detect increase blood glucose levels
-Beta cells within pancreas release insulin
-Insulin stimulates target cells
-Decreased blood glucose inhibit insulin
-Different liver/adipose effects
Glucagon
-Alpha cells detect decreased blood glucose levels
-Alpha cells within pancreas release glucagon
-Insulin stimulates target cells
-Increased blood glucose inhibit glucagon
Diabetes Mellitus
-Inadequate uptake of glucose from blood
-Type 1, 2, and gestational
Endocrine Glands (others)
-Pineal, melatonin
-Thymus, thymosin
-Gonads, estrogen and testosterone