Chapter 16

Endocrine System

Endocrine System

Endocrine System

• Acts with the nervous system to coordinate and integrate activity of body cells

• Influences metabolic activities via hormones transported in blood

• Responses are slower but longer lasting than nervous system responses

Endocrinology

Study of hormones and endocrine organs

Neuroendocrine Axis

Nervous system and endocrine system work together to achieve homeostasis

The Endocrine System Controls/ Integrates:

• Reproduction

• Growth/Development

• Maintenance of electrolytes, water, nutrients

• Regulation of cellular metabolism/ energy balance

• Mobilization of body defenses

Exocrine Glands

• Produce nonhormonal substances (sweat/saliva)

• Have ducts to carry secretion to membrane surface

Endocrine Glands

• Produce hormones

• Lack ducts

Target Cells

Cells with a receptor for a certain ligand (cognate)

2 Types of Proteins

• structural

• machines (motor, enzymes ect)

What does enhancing transcription factor and increasing RNA do to protein production?

Increases it

What does inhibiting transcription factor and decreasing RNA do to protein production?

Decreases it

Polar Hormones

• Water soluble

• Most are peptides

• Most common type of hormone

• Transported directly in ECF

Nonpolar Hormones

• Lipid soluble

• Hydrophobic

• Most are steroids

Examples of nonpolar hormones

• Estrogen

• Progesteron

• Testosterone

• Aldosterone

• Cortisol

• Thyroid

Two Types of Hormones

• Circulating Hormones

• Local Hormones

Circulating Hormones

Long distance and circulates everywhere

Local Hormones

Don’t circulate; stays in the same spot

Two types of local hormones

• paracrines

• autocrines

Paracrine Hormones

One cell stimulates cells around it

Autocrine Hormones

Cell releases hormone to stimulate itself

Hypothalamus

Neuroendocrine organ

Endocrine Glands

• pituitary

• thyroid

• parathyroid

• adrenal

• pineal

Organs that have exocrine and endocrine functions

• pancreas

• gonads

• placenta

Up Regulation

increasing the production of receptors when hormones are low

Down Regulation

decreasing the production of receptors when hormones are high

Why do cells up regulate?

to increase likelihood of binding to the limited hormone in order to increase protein production

Why do cells down regulate?

hormones are bound to too many receptors which causes too much protein expression

Ways to produce protein

• permissive effect

• antagenistic hormones

• synergy

Permissive Effect

need binding hormones to produce protein

areas of the adrenal gland

• zona glomeralosa

• zona fasiculata

• zona reticularis

Non hypothyseal structures

• adrenal gland

• parathyroid gland

• pineal gland

• pancreas

• adipose tissue

• GI tract

• bone

• heart

• kidneys

trophs

• cells of the anterior pituitary

• thyrotrophs

• gondotrophs

• corticotrophs

• somatotrophs

• lactotrophs

post pituitary (neurohypophysis)

makes no hormones, only releases hormones made in the hypothalamus

oxytosin

• happens in the post pituitary

• released during childbirth and milk production

ADH

• decreases urine production

• used when you’re very dehydrated

Vasopressin

shrinks blood vessels to increase blood pressure

Short term effect of ADH

Vasoconstriction or vasopressin (puts pressure back into blood; increases BP)

Long term effects of ADH

• dry mouth, eyes, no sweating (conserve H2O)

• hormone goes to kidneys causing them to pull H2O from urine and put it back into the blood (increase blood volume and BP while decreasing blood osmolarity

Hypovolemic shock

• systemic decrease in BP

• prevents cells from being fed

Nonhypophyseal Organs

Adrenal gland and kidney

Kidney

• Moniters BP at cells JG complex

• If blood pressure drops, JG cells produce an enzyme that is secreted into the blood (renin)

Zona Glamurosa

• zone 1 of the adrenal gland

• produce mineralacorticoid

• puts salt and water from urine back into blood

Mineralacorticoid

makes mineral aldosterone in order to increase BV and BP

Zona fasiculata

• zone 2 of the adrenal gland

• only zone found in the hypophyseal

• contains corticol RH

• produces glucocorticoids

Corticol RH

makes ACTH

Chromatin Cells

• trigger fight/flight

• shorten stress response

Zona reticularis

• Zone 3 of the adrenal gland

• Produces gonadocorticoid

Gonadocorticoid

• makes androgen

• testosterone-like

Hypophyseal Portal System

• primary capillary plexus

• hypophyseal portal veins

• secondary capillary plexus

Hypersecretion of GH

Caused by anterior pituitary tumor

Hyposecretion of GH

in children, dwarfism

Thyroid parafollicular cells

• nonhypophyseal

• respond to high calcium in blood

• produce calcatonin

Calcitonin

• increase osteoblast activity

• decrease blood calcium

Parathyroid gland

produces parathyroid hormone

Parathyroid hormone

• increase “clast”

• increase calcitriol

• in the kidneys

Monoiodotyrosine (MIT)

Formed if only one iodine attaches

Diiodotyrosine (DIT)

Formed if two iodines attach

Myxedema

Hyposecretion of TH in adults

Goiter

• developed due to lack of iodine

• thyroid enlarges

• decreases TH levels trigger an increase in TSH secretion, triggering thyroid to synthesize more more unusable thyroglobulin

Graves disease

body makes abnormal antibodies directed against thyroid follicular cells

Calcitriol

increases blood calcium levels

Hormones

Long distance chemical signals; travel in blood or lymph

Amino acid-based hormones

Amino acids derivatives, peptides and proteins

Steroids

• synthesized from cholesterol

• gonadal and adrenocortical hormones

Synergism

More than one hormone produces same effects on target cells, causing amplification

Antagonism

One or more hormones oppose an action of another hormone

Posterior pituitary

composed of neural tissue that secretes neurohormones

Anterior pituitary

consists of glandular tissue

Prolactin (PRL)

Stimulated: by decreased PIH released enhanced by estrogens, birth control pills, breast feeding, and dopamine-blocking drugs

Inhibited: by PIH (dopamine)

Result (hypo/hypersecretion) : poor milk production in nursing women and inappropriate milk production

Thyroid- stimulating hormone (TSH)

Stimulated: by TRH and in infants indirectly by cold temperature

Inhibited: by feedback inhibition exerted by thyroid hormones on anterior pituitary and hypothalamus and by GHH

Result (hypo/hypersecretion) : cretinism in children; myxedema in adult and hyperthyroidism

Adrenocorticotropic hormone (ACTH)

Stimulated: by CRH; stimuli that increases CRH release include fever, hypogylcemia, and other stressor

inhibited: by feedback inhibition exerted by glucocorticoids

Result (hypo/hypersecretion) : Rare hyposecretion and cushings disease

Follicle- stimulating hormone (FSH)

Stimulated: by GnRH

Inhibited: by feedback inhibition exerted by inhibin and estrogens in females and testosterones in males

Result (hyposecretion) : failure of sexual maturation

Luteinizing hormone (LH)

Stimulated: by GnRH

Inhibited: by feedback inhibition exerted by estrogens and progesterone in females and testosterone in males

Colloid

Fluid of follicle lumen containing thyroglobulin plus iodine and is precursor to thyroid hormone

Thyroxine (T4)

Major form that consists of two tyrosine molecules with four bound iodine atoms

Triiodothyronine (T3)

Form that has two tyrosines with three bound iodine atoms

Hyposecretion of basal metabolic rate from thyroid hormone

• decreased body temp

• cold intolerance

• decreased appetite

• weight gain

Hypersecretion of basal metabolic rate from thyroid hormone

• increased body temp

• heat intolerance

• increased appetite

• weight loss

hyposecretion of carbohydrate/lipid/ protein metabolism from thyroid hormone

• decreased glucose metabolism

• elevated cholesterol/ triglyceride levels in the blood

• decreased protein synthesis; edema

Hypersecretion of carbohydrate/lipid/protein metabolism from thyroid hormone

• enhanced catabolism of glucose, proteins and fats

• weight loss, loss of muscle mass

Aldosteronism

Hypersecretion usually due to adrenal tumors

Glucocorticoids

Influence metabolism of most cells and help us resist stressors

Glucagon

• extremely potent hyperglycemic agent

• raises blood glucose levels