Transcript Endocrine System

Endocrine System
Biology 2122
Introduction
(1) What are hormones?
(2) What are the functions of hormones?
(3) What are the types of hormones?
– Amino Acids
– Steroids
– Eicosanoids
How do Hormones Work?
(1) Action on Target Cells
– Membrane permeability
– Synthesis of proteins or enzymes
• Or inhibits
– Induces secretory activity
– Stimulates mitosis
(2) Target-Specific
– Target cell receptor sites
– “Turns on cell”
– “Dynamic”
How do Hormones Work?
(3) Half-Life
(4) Interaction – Target Cells
– Permissive
– Synergistic
– Antagonistic
(5) Control of Release
– Negative feedback
– Endocrine Gland Stimuli
• Humoral stimuli
• Neural stimuli
• Hormonal stimuli
Plasma Membrane Receptors
(1) Second Messenger System
– All amino acid hormones (except thyroid)
Plasma Membrane Receptors
(2) Intracellular – Direct Gene Activation
–
–
–
–
Lipid soluble; steroid
Binds to intracellular receptors
Binds to DNA
Activates a gene
Anterior Pituitary Hormones-HGH
(1). Somatotroph cells produce GH
(2). Secretion
– GHRH – stimulates release (GHIH) inhibits
– Produced in the hypothalamus
(3). Effects
– Anabolic – protein synthesis
– Targets bones and muscles
– Stimulates epiphyseal plates during
development
(4). Disorders
– Gigantism and Acromegaly
Thyroid-Stimulating Hormone
• (1). Also referred to as thyrotropin.
– Produced by thyrotroph cells
• (2). Secretion
– TRH or thyrotropin releasing hormone stimulates the release
of TSH
– Negative feedback – rising levels of thyroid hormones
• ANIMATION
• (3). Effects
– Moderates normal thyroid gland activity.
Adrenocorticotropic Hormones
• (1). ACTH – adrenocorticotropic hormone
secreted
– corticotroph cells
• (2). Stimulation-Secretion
– CRH – corticotropin-releasing hormone – hypothalamus
• Levels peak in the morning
– Negative feedback
• (3). Effects
– Stimulates the Adrenal gland (cortex) to release Glucocorticoids
• Cortisol (stress hormone)
Gonadotropins
 (1). FSH and LH – gonadotrophic cells
 (2). Stimulus-Secretion
◦ Puberty
◦ GnRH – prompts the anterior pituitary to release hormones
◦ ANIMATION
 (3). Effects
◦ (a). LH
 FSH - maturation of follicle
 Ovulation
 Stimulates interstitial cells - testosterone in males
◦ (b). FSH – stimulates gamete production; follicle development.
Prolactin
(1). PRL or prolactin is a protein hormone.
– Produced by the lactrotroph cells
(2). Stimulus – Secretion
– PRH and PRH
– PRH plays dominant role – dopamine prevents secretion
(3). Effects
– Stimulate milk production in the breasts
Acromegaly
Posterior Pituitary Gland Hormones
(1). Production-
hypothalamic neurons
(2). ADH or Antidiuretic Hormone
– Reabsorption of water – collecting tubules
– Release stimulated by – increasing osmolarity
• Diabetes insipidus
(3). Oxytocin
– Stimulated release by positive feedback – contractions
during birth
– Milk ejection
– Synthetic – induce contractions
Thyroid Gland
(1). Produces TH or thyroid hormones
◦ T4 or thyroxin; T3 or triiodonthyronine
(2). Stimulus – Secretion
◦ Hypothalamus (TRH) - Pituitary (TSH) --
TH
◦ Stress - cold, pregnancy – cause
hypothalamus to produce TRH.
◦ Rising TH levels – negative feedback to
hypothalamus-pituitary axis.
(3). Effects
◦ Increases BMR
◦ body heat production (stimulates enzymes
to increase glucose oxidation)
Synthesis of TH
Thyroid Imbalances
• (1). Myxedema – hypothyroid
• (2). Goiter
• (3). Cretinism
– Infant hypothyroidism
• (4). Grave’s Disease
– Hyperthyroid
Calcitonin
(1). Polypeptide hormone
– Parafollicular cells of the thyroid
– Lowers calcium blood levels
– Reabsorption back into the bones
(2). Stimulus for release
– 20% above normal levels for calcium blood levels
– Lower than normal – inhibitory effect
(3). More important in childhood
– Due to developing bones and keeps calcium levels in check
Parathyroid Hormones
(1). Cells in the parathyroid gland
– Oxyphil and chief cells (secretes ) PTH
(2). Stimulus and Secretion
Increases
calcium
absorption
Kidney
Osteoclast
activity
increased
Intestines
Bone
– Hypocalcemia ----- PTH
Increases
calcium
reabsorption
Adrenal Hormones
(1). Adrenal gland has two distinct regions
◦ (a). Cortex - outer region
◦ (b). Medulla - inner region
(2). Hormones produced
–
corticosteroids
◦ 12 total
(3). Steroid Hormones
–
Not stored in cells – rate of release depends on productivity
(4). Cortical regions
◦ (a). Zona glomerulosa – mineralocorticoids
◦ (b). Zona fasciculata – glucocorticoids
◦ (c). Zona reticualaris – adrenal sex hormones called
gonadocorticoids.
Mineralocorticoids
(1). Produced in the zona glomerulosa of the cortex
◦ Mostly aldosterone
◦ Balances ions and water
(2). Stimulus and Secretion
◦ Renin-angiotensin mechanism
◦ Elevated K+ levels
(3). Disorders
◦ Aldosteronism
◦ Addison’s disease
Glucocorticoids
(1). Produced in the zona
fasciculata
– Metabolic hormones
(2). Cortisol is the main hormone
– Gluconeogenesis; lipolysis;
protein metabolism
(3). Stimulation and secretion
– ACTH from the anterior pituitary
(low levels of hormones)
(4). Disorders
– Cushing’s syndrome
– Addison’s disease
Gonadocorticoids
(1). Androgens produced in the zona reticularis
– Converted to testosterone and estrogen
(2). Stimulus and secretion
– ACTH released from anterior pituitary
(3). Effects
– Males
– Female libido; pubic and axillary hair in females; estrogen
after menopause