Download Endocrine System

Endocrine System
Overall Functions

Regulatory System
 Maintains homeostasis internally
 Responds to environmental changes
 Growth and development
 Reproduction
Glands

Exocrine e.g. salivary glands
 Endocrine e.g. Thyroid gland
Hormone

Definition: A chemical messenger carried
by bloodstream and made by endocrine
glands.
 Structure
 Transport in body
Action of hormones

Target cell
 Receptors
– Plasma membrane
– Within target cell

Second messenger (cAMP)
 Activation of genes
Relationships

To other hormones
 To nervous system
Controls

Negative Feedback
 Releasing hormones and Inhibiting
hormones from Hypothalamus
PITUITARY GLAND
(Hypophysis)

Location – in sella turcica of sphenoid bone
Hormones of the
Adenohypophysis

Gonadotropins
– FSH = Follicle Stimulating Hormone
– LH/ICSH = Luteinizing hormone in female,
Interstitial cell stimulating hormone in male
Adenohypophysis

TSH = Thyroid stimulating hormone
 ACTH = Adrenocorticotropic hormone
 GH = Growth hormone
 Prolactin
 MSH = Melanocyte stimulating hormone
 (endorphins)
Adenohypophysis

Controls
 Inhibiting hormones and Releasing
hormones
 Brain
 Negative feedback
Neurohypophysis

Infundibulum (hypothalamic-hypophyseal
tract)
 ADH = Antidiuretic hormone = Vasopressin
 Oxytocin
Thyroid Gland

Location
 Histology
 Follicles, colloid
 Thyroid hormones
Thyroid hormone

Iodine
 T4 (thyroxine – 90%)
 T3 (thriiodothyronine – 10%)
 TBG (thyroid binding globulin)
 Function
 Controls
Thyroid Hormone Synthesis
Tyrosine + Iodine  Monoiodotyrosine
 + Iodine  Diiodotyrosine
 2 Diiodotyrosine  Tetraiodothyronine =
T4 = Thyroxine

Thyroid Hormone Synthesis

1 Diiodotyrosine + 1 mono… 
Triiodothyronine = T3
Thyroid gland

Calcitonin
 Parafollicular (C) Cells
 Decreases Ca and P
 Controls
Parathyroid glands

Location
 PTH (Parathromone)
 Increases Ca and decreases P
 Controls
Adrenal gland

Location
 Adrenal Medulla
 Chromaffin cells
 Epinephrine (80%)
 Norepinephrine (20%)
 Action
 Release
Adrenal gland

Adrenal Cortex
 Mineralocorticoids
– Zona glomerulosa
– Aldosterone (90%)
– Na reabsorption, K excretion in kidneys
Aldosterone

Release/Controls
 Renin, Angiotensin
 K/Na levels
 ACTH, CRH
Adrenal cortex

Glucocorticoids
– Zona fasciculata
– Conserves and supplements energy
– Anti-inflammatory
– Release/Controls
 ACTH, CRH,
 Stress
Adrenal cortex

Sex hormones
– Zona reticularis
Pancreas

Location
 Endocrine AND Exocrine
 Pancreatic islets = Islets of Langerhans
Insulin

Beta cells
 Lowers blood glucose
 Controls
Glucagon

Alpha cells
 Raises blood glucose
 Controls
Somatostatin

Delta cells
 Inhibits GH release
Controls

Blood glucose levels
 GI
 ANS
Gonads

Testes make androgens
 Ovaries make estrogen and progesterone
 TO BE DISCUSSED LATER
Pineal Gland

Location
– Roof of third ventricle in brain

Melatonin
– Decreases reproductive activity
Thymus

Location
– Mediastinum, above heart

Puberty
 Immunity
 Thymic Hormone stimulates T cell
maturation
Prostaglandins

Fatty acids
 Localized hormones
 Functions vary