Hormones:
• Produced by endocrine glands [e.g. pituitary]
• Circulate in the blood stream
1. Steroids - lipid soluble
2. Nonsteroids - not lipid soluble
• Often interact with nervous system
• Act on specific cells [target cells] in the body
Endocrine System: Regulates body
functions with Hormones
• Access to every cell
• Each hormone acts only on specific target cells
• Target cells have receptors for specific hormones
• Endocrine control slower than nervous system
• Endocrine & nervous systems interact
Endocrine System Characteristics
Steroid Hormones:
• Lipid soluble, chemically derived from cholesterol
• Enter target cells
• Activate specific genes to produce specific proteins
• Slower acting than nonsteroid hormones, minutes to hours
Classification of Hormones: Steroid
Nonsteroid hormones:
• Water soluble
• Bind to receptors on target cell membranes
• Work through intermediate mechanisms to activate existing enzymes
• Faster action than steroid hormones, seconds to minutes
Classification of Hormones: Nonsteroid
Posterior pituitary gland:
Connection to hypothalamus: hormones made in hypothalamus, stored in posterior pituitary
Hormones: nonsteroidal operate here
1. Antidiuretic hormone (ADH): conserves water in kidneys, regulates water balance in body
2. Oxytocin: causes uterine contractions during labor & milk ejection through neuroendocrine reflex
Hypothalamus and the Posterior Pituitary Gland
Anterior pituitary gland:
Connection to hypothalamus: releasing and inhibiting hormones from hypothalamus travel to pituitary through pituitary portal system
Hormones: nonsteroidal operate here
1. ACTH- stimulates adrenal cortex
2. TSH- acts on thyroid gland
3. FSH, LH, Prolactin- related to control of reproductive cycles and lactation
4. Growth Hormone- widespread effects on body
Hypothalamus & the Anterior Pituitary Gland
1. Hypersecretion of ADH - excessive water retention
2. Diabetes Insipidus - hyposecretion of ADH, inability to conserve water appropriately
3. Gigantism- hypersecretion of growth hormone
4. Pituitary Dwarfism- hyposecretion of growth hormone
Pituitary Disorders
Hormones secreted by islets of Langerhans are
Nonsteroidal:
1. Glucagon - raises blood sugar
2. Insulin- lowers blood sugar
Pancreas: Endocrine Functions include
Adrenal cortex - secretes steroid hormones
Produces small amounts of estrogen & testosterone
Produces:
• Cortisol [regulates blood glucose]
• Aldosterone [regulates sodium & potassium]
Adrenal Glands: 2 small endocrine glands located
just above kidneys
Adrenal medulla- secretes nonsteroid hormones
Secretion: stimulated by sympathetic nervous system
Nonsteroidal hormones that control metabolism, blood pressure & heart rate
1. Epinephrine [adrenaline]
2. Norepinephrine
They both enhance function of sympathetic
nervous system (Fight or Flight Response)
Adrenal Glands: Medulla
• Secretion: mediated through hypothalamus-pituitary secretions
• Secretes Steroidal hormones:
• Thyroxine (T4) and Triiodothyronine (T3) - both regulate production of ATP from glucose, affects metabolic rate
• Calcitonin: lowers blood calcium levels
Thyroid Gland
• Secretion: response to lowered blood calcium levels
• Hormone: Parathyroid hormone (PTH), nonsteroidal
• Removes calcium and phosphate from bone
• Increases absorption of calcium by the digestive tract
• Increases renal retention of calcium and excretion of phosphate
Parathyroid Glands
Hormone secreted = Testosterone (steroidal)
Functions:
1. Regulates development and normal functioning of sperm, male reproductive organs, male sex drive
2. Development of male secondary sex characteristics
Testes
Hormones (steroidal) & functions:
1. Estrogen- initiates development of secondary sex characteristics, regulates menstrual cycle
2. Progesterone - regulates menstrual cycle
Ovaries
1. Histamine - inflammation
2. Prostaglandins - local control of blood flow
3. Growth factors - local acting/ mitotic activity
Other Chemical Messengers
Thyroid Disorders:
1. Hypothyroidism - underactivity of thyroid
• Children: slows body growth, brain development & delays puberty
• Adults: causes edema, weight gain, lethargy, low body temp.
2. Hyperthyroidism: [Graves Disease]
• Overactive thyroid
• Causes- Increased BMR, hyperactivity, nervousness, weight loss
Disorders of the Endocrine System
Adrenal Gland Disorders:
1. Addison’s Disease: failure of adrenal cortex to secrete sufficient cortisol & aldosterone
• Lowers blood glucose & sodium
• Symptoms: Chronic fatigue, weakness, weight loss & abdominal pain
2. Cushing’s Syndrome: excessive cortisol produced
• High blood glucose & reduced muscle mass
• Retension of too much salt & water
• Symptoms: weakness & fatigue, edema, high blood pressure
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