Hormones

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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 RegulationFeedback 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 – 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– 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