Hormones
Teen Steroids In The News
Hormones Chemical messengers Produced in one part of the body, have an effect on another part Carried in bloodstream
Chemical Signals
Endocrine System Hormonal system of vertebrates Endocrine glands secrete hormones Ductless Empty into bloodstream Exocrine glands Secrete products into ducts
Hormone Actions Affects parts distant from gland May affect numerous parts of the body Effects take longer than nervous system Effects may be long lasting
Types of Hormonal Control Regulation Response Reproduction Growth & development
Human Endocrine System
Hormone Activity Affect only target cells Hormone must bind to a receptor Receptor activates chain of events
Classes of Hormones Peptide hormones Steroid hormones
Hormone Regulation Feedback Loops
Stimulation of Endocrine Glands Direct stimulation by nervous system Indirect stimulation by nervous system by means of releasing hormones Concentration of specific substances in the bloodstream
Pituitary Gland Secretes 9 major hormones Hangs from the underside of the brain Regulated by hypothalamus
Hypothalamus Regulation of Pituitary Anterior pituitary Hypothalamus produces releasing hormones Posterior pituitary Neural regulation
Pituitary Hormones
Growth Hormone Controls normal growth Hypersecretion Gigantism Acromegaly Bones of hands & face thicken
Pineal Gland Embedded within brain Produces melatonin Increase in secretion at night Helps set circadian rhythms
Thyroid Gland Below level of voice box Hormones that regulate metabolism Most body cells have receptors Negative feedback loop regulates release
Thyroid Disorders Graves disease Hyperthyroidism Rapid heart rate Nervousness Protrusion of eyes
Thyroid Disorders Goiter Hypothyroidism Slow growth Caused by insufficient iodine in diet Thyroid enlarges
Parathyroid Gland Embedded on posterior of thyroid gland Secretes parathyroid hormone (PTH) PTH works antagonistically to Calcitonin Calcitonin produced in Thyroid Regulate calcium levels
Adrenal Glands Located on top of kidneys Each gland has two parts Adrenal cortex (outer) Adrenal medulla (inner)
Adrenal Hormones Adrenal cortex Adrenal medulla Corticosteroids Mineralocorticoids Glucocorticoids Adrenal medulla Cells similar to neurosecretory cells Epinephrine & norepinephrine
Alarm Reaction to Stress
Pancreas Endocrine portion in islets of Langerhans Hormones that regulate levels of glucose
Diabetes High levels of glucose in blood Two types Lack of insulin Inability of tissue to respond to insulin Two types Type I = insulin dependent Pancreas does not produce enough insulin Type II Often occurs later in life
Other Endocrine Glands Thymus Hormones to mature lymphocytes Ovaries Estrogens & progesterone Testes testosterone