Endocrine System

Endocrine System

Chapter 13

Endocrine System

Releases hormones Into bloodstream that are then delivered to cells

Works with the nervous system Nervous system can stimulate or inhibit hormone

release Hormones can promote or inhibit nerve impulses http://www.unitedstreaming.com/search/assetDetail

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Two Types of Glands

Exocrine glands – secrete hormones into ductsSweat, digestive, mucous, and oil glands

Endocrine glands – secrete hormones into interstitial fluid Pituitary, thyroid, parathyroid, adrenal, and

pineal glands

Functions of Hormones

Regulate body functionMetabolism, energy balance, immune

systemControl growth and developmentGovern operation of reproductive

systems

Hormones

Circulating hormones = pass from the cells that make them into interstitial fluid

Inactivated by liver and excreted by kidneysOnly affects target cellsBinds to particular receptors that are

only found on the specific target cellsLocal hormones = act on neighboring

cells or same cell that made itDo not enter bloodstream

Lipid Soluble Hormones

Steroid hormonesThyroid hormonesNitric oxide

Water Soluble Hormones

Amine hormonesPeptide and protein hormonesEicosanoid hormones

Control of Hormone Secretion

1. Signals from nervous system2. Chemical changes in blood3. Other hormones

Hypothalamus

“master” of pituitary glandMajor connection between endocrine

and nervous systemMakes atleast 9 hormonesNeurosecretory cells- release hormones

into the bloodstream

Anterior Pituitary Hormones

1. Human growth hormone (hGH)- cells secrete insulinlike growth factors (IGFs)

1. Cause cells to grow and multiply2. Increase protein synthesis rate Controlled by GHRH and GHIH

2. Thyroid-stimulating hormone (TSH)- stimulates thyroid to produce and secrete T3 and T4

Anterior Pituitary Hormones (cont.)

3. Follicle-stimulating hormone (FSH):1. Initiates the development of follicles2. Stimulates secretion of estrogen from follicular

cells3. Stimulates sperm production Estrogen and testosterone inhibit FSH release

4. Luteinizing hormone (LH):1. Triggers ovulation2. Stimulates estrogen and progesterone secretion3. Secretes testosterone

Anterior Pituitary Hormones (cont.)

5. Prolactin (PRL)- initiates milk secretion from mammary glandsRegulated by PIH and PRH

6. Adrenocorticotropic hormone (ACTH)- controls production and secretion of glucocorticoids

Posterior Pituitary Hormones

Tropic hormones = influence other endocrine glands

Does not synthesize hormones1. Oxytocin (OT):

1. Enhances contraction of muscle cells in uterus wall

2. Stimulates milk ejection

Posterior Pituitary Hormones (cont.)

2. Antidiuretic hormone (ADH): 1. Kidneys to return more water to the blood2. Decrease water loss through sweat3. Constriction of arterioles

Increases blood pressure Other name: vasopressin

Thyroid Gland

Just below the larynxRight and left lobes connected by

isthmusTwo hormones: thyroxine (T4) and

triiodothyronine (T3)Calcitonin (CT)

T3 and T4

Regulate basal metabolic rate and oxygen use

Regulate cellular metabolismRegulate growth and developmentRegulated by blood iodine level, TRH,

and TSH

Calcitonin (CT)

Decreases level of calcium in bloodUnclear importance: can have lots or be

absent and no clinical symptoms

Parathyroid Gland

Four small, round masses of tissuePrincipal cells- secrete parathyroid

hormone (PTH)PTH:

Regulates calcium, magnesium, and phosphate ions in the blood

Increases osteclastsPromotes formation of calcitriol

Blood calcium level regulates PTH secretion

Adrenal Glands

Located on top of the kidneysAdrenal cortex on the outsideAdrenal medulla is the middle of the

adrenal gland

Adrenal Cortex Hormones

1. Mineralocorticoids: control homeostasis of water, sodium ions, and potassium ions

Most influential hormone: aldosterone2. Glucocorticoids: protein breakdown,

glucose formation, lipolysis, resistance to stress, anti-inflammatory effects, and depresssion of immune response

Most popular: cortisol

Adrenal Cortex Hormones (cont.)

3. Androgens:Males: secrete small amountsFemales: contribute to sex drive and

converted to estrogensStimulate growth of axillary and pubic hair

and contribute to prepubertal growth spurt

Adrenal Medulla Hormones

Sympathetic postganglionic cells of the autonomic nervous system

1. Epinephrine (adrenaline)2. Norepinephrine (NE) (noradrenaline) Increase blood pressure, increase

blood flow, dilate airways to the lungs, increase glucose and fatty acid blood levels

Pancreas

Located in the curve of the duodenum Pancreatic islets (islets of Langerhans)

contain:1. Alpha cells- secrete glucagon2. Beta cells- secrete insulin3. Delta cells- secrete somatostatin4. F cells- secrete pancreatic polypeptide

Glucagon

Increase blood glucose level by:Accelerating conversion of glycogen into

glucosePromoting conversion of amino acids and

lactic acid into glucoseStimulating the release of glucose into the

blood

Insulin

Accelerates diffusion of glucose into body cells

Accelerates conversion of glucose into glycogen and fatty acids

Promotes amino acid uptake into body cells

Slows conversion of glycogen to glucoseSlows glucose formation by liver cells

Ovaries

Produce estrogens and progesterone:Regulate the menstrual cycle, maintain

pregnancy, prepare mammary glands for lactation, develop and maintain sex characteristics

Inhibin: inhibits secretion of FSHRelaxin: helps enlarge birth canal

Testes

Oval glands that lie in scrotumProduces testosterone:

Regulates sperm productionStimulates development and maintenance

of male characteristicsProduces inhibin: inhibits FSH secretion

Pineal Gland

Small glandSecretes melatonin:

Sets body’s biological clockMore melatonin released in darknessLevels are decrease with adulthood

Thymus

Located behind the sternum between the lungs

Hormones: thymosin, thymic humoral factor (THF), thymic factor (TF), and thymopoietinPromote maturation of T cells May delay the aging process