Endocrine System

Some Review First4 types of cell signal mechamisms

Direct Contact- see table and page 127

Paracrine Signaling, message transmitted to neighboring cells

Synaptic signaling —neurotransmitters carry messages between nerve cells

*Endocrine signaling —hormones travel through circ system

Focus of this presentation

Hormones-4 groups

Polypeptides-short chains of aa’s- insulin and ADH (anti-diuretic hormone)

Glycoproteins-longer chains of aa’- FSH and LH (from reproductive system)

Amines-from tyrosine and tryptophan-melanin and epinephrine

Steroids- derived from cholesterol (inc. ring shape)-testosterone and progesterone

2 Hormone Mechanisms

Lipid or steroid hormones—diffuse into cell and trigger response

Protein or peptide hormones– use a second messenger system Hormone binds (1st messenger) Triggers intracellular response via a G

protein c AMP (second messenger)

ANTERIOR PITUITARY HORMONES

Growth Hormone (GH) – Stimulates bone growth

Luteinizing Hormone (LH) – Stimulates ovaries and testes

Named for corpus luteum Follicle Stimulating Hormone(FSH)-

stimulates gonads to produce sperm and ova

Named for follicle Thyroid Stimulating Hormone (TSH)-

Stimulates thyroid gland

Gigantism

Posterior Pituitary Hormones

Oxytocin – Stimulates contractions of uterus and mammary glands, associated with love and bonding.

Antidiuretic hormone (ADH) – retention of water by kidneys

GONADS AS GLANDS

Ovaries Estrogen – stimulates uterine lining,

development of primary and secondary female characteristics

Progesterone – Uterine lining growth, helps maintain pregnancy

Testes Androgens (testosterone) – sperm

production (after stimulation by FSH), secondary sex characteristics

Thyroid

Thyroxine– controls metabolic rate Calcitonin– lowers blood calcium

levels (deposits Ca++ in bone)

Hypothyroidism may lead to goiter Hyperthyroidism may lead to protrusion of

the eyes (bulging) and Grave’s Disease Both problems make it difficult to control

metabolic rate

CretinismHyposecretion of thyroxine in childhood

Parathyroid

Parathyroid Hormone (PTH) Raises blood calcium level (removes Ca ++ from bone)

Hypoparathyroidism - Bones become weakened

Osteoporosis—same outcome, but for a variety of reasons

Osteoporosis

PANCREAS- Islets of Langerhans

Insulin – β cells – lowers blood glucose levels

Glucagon – α cells -raises blood glucose levels

Read Analyzing Functions of Pancreas(Dog Studies)

Diabetes

Type 1 – Hyposecretion of Insulin, Insulin Dependent diabetes

Type 2 – Cellular response to insulin is decreased Associated with obesity, strong diet

correlation

Diabetes

Uncontrolled diabetes can lead to damage of many systems. Some problems may be kidney disease, nervous system problems, blindness, peripheral vascular disease.

Adrenal Glands

Adrenal Medulla – Catecholamines Epinephrine and Norepinephrine raises blood sugar by incr. breakdown of glycogen in liver, short term stress response

Adrenal Cortex --Glucocorticoids -- raise blood sugar levels, long term stress response Overproduction—Cushing’s Disease (breakdown of

proteins and unusual fat distribution) Long term stress has adverse effects on many

systems

THYMUS

Thymosin– Stimulates T lymphocytes

Pineal

Melatonin - Biorhythms –Day and Night Cycles

Homeostasis

Homeostasis may be thought of as a see-saw

(Look at anatomy transparency 14.20)

Negative feedback--Return to baseline- balance see-saw

Positive feedback--Continued unbalance

ANTAGONISTS

Antagonistic hormones have opposite effects. They work together to maintain homeostasis.

Ex: Insulin and Glucagon, PTH and Calcitonin

GLAND INTERACTIONS

Glands may stimulate (or inhibit) other glands See Thyroxine secretion page 1004 See testes and anterior pituitary page

1071

CASE STUDIES

See page 102 in ABLE