Complete Endocrine System Study Guide

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Function of the endocrine system

• homeostasis

• support cell growth

• coordinate development and reproduction

• respond to external stimuli

• adaptation

• metabolism

Autocrine

chemical secreted and binds to itself

Endocrine

chemical secreted and is meant for distant cells

Paracrine

chemical meant for nearby cells

Chemical messenger

hormone released to bloodstream

Nondestructive medium

blood

Target cell

cell that responds to hormones secreted by glands

Endocrine glands

stores, creates, and secretes chemical messengers

Selective receptors

receptor will only respond if a specific hormone binds to it

Properties of hormones

• molecule function as messenger, which conveys information

• transported in blood

• bind to distant target cells

• activates respoonses

• low concentration

• degraded by enzymes at target cells

Classes of hormones

• proteins and peptide

• lipids (steroids, fatty acids)

• amino acid derived

• gases (NO, CO2)

Protein hormones

• 3 amino acids to hundreds

• largest

Protein hormones are usually considered the _____ in number

largest

Protein hormones are ____ soluble

water

Amine hormones

derived from simple amino acids (tryptophan, glutamic acid, etc)

examples of amine hormones

• thyroid hormones (TSH)

• catacholamines (epinephrine)

Tryphophan is found in

serotonin and melatonin

Glutamic acid is found in

histamines

Two types of lipid hormones

steroids and fatty acids

Parent compound of steroids

cholesterol

Steroid locations

• reproductive organs

• adrenal glands

• kidneys

Types of steroids

• androgens, testosterones, and estrogens

• adrenal hormones such as aldosterone and corticosteroid

• vitamin D

Characteristics of fatty acids

• short lived, inactivated relatively quickly

• respond to injury and disease

• localized

Fatty acids are derived from

arachidonic acid

Types of hormone receptors

• membrane

• cytoplasmic/nuclear

Hormone-receptor interaction

• hormone plasma concentration

• number of receptors

• affinity

Target tissue

• cells with receptors for a given hormone

• bind with specificity

up regulation

more receptors are created

down regulation

less receptors are created

What are second messengers

• convert information in hormonal signals into chemical signals understood by cellular machinery

• amplifying energy content of original hormonal signal

Example of second messenger

cyclic AMP pathway

First step of cyclic AMP pathway

receptor binds to protein channel

Second step of cyclic AMP pathway

gets activated, G-protein activates

Third step of cyclic AMP pathway

G-protein activates enzyme to convert ATP to cyclic AMP

Hormonal release

hormone that triggers release of another hormone

Example of hormonal release

growth hormone causing release of another hormone

Humoral release

something in blood regulates the release of hormone (e.g salt, calcium, glucose levels)

Example of humoral release

release of insulin and glucagon in response to varied blood sugar levels

Neural release

hormone release from CNS

Example of neural release

breastfeeding while hearing a crying baby

Types of hormone interactions

• synergistic

• permissiveness

• antagonism

• integrative

Synergistic effect

two hormones working together in order to create a greater effect instead of working independently

Permissive effect

first hormone is needed in order for the second hormone to produce an effect

Antagonist effect

one hormone’s effect is completely opposes the actions of another

Integrative effect

hormones may produce different, but complementary results in specific organs or tissues

Tropic hormones

trigger endocrine hormones to release other hormones

Direct acting hormones

triggers physiological response when receptor is binded

Hypothalamus

• located in the brain

• neuroendocrine gland

Pituitary gland

• inferior to the hypothalamus

• has two parts (anterior and pituitary)

Adenohypophysis / par distalis

alternate name to anterior pituitary

Neurohypophysis / par nervosa

alternate name to posterior pituitary

Direct acting hormones produced by the anterior pituitary

growth hormone and prolactin

Growth hormone production location

anterior pituitary

Growth hormone target cells

skeletal/cardiac muscle, bone, liver, adipose, etc

Growth hormone function

regulates and controls growth

Prolactin production location

anterior pituitary

Prolactin target cells

Mammary glands

Prolactin function

stimulates mammary glands to produce milk, development of breast tissue

Gigantism

• hypersecretion of growth hormone before the epiphyseal plate closes

• size is proportional

Acromegaly

hypersecretion of growth hormone after the epiphyseal plate closes

Dwarfism

• hyposecretion of growth hormone

• usually less than 4 ft in height

• proportional

Hormones produced by posterior pituitary

none, used for storage and secretion

Antidiuretic hormone production location

supraoptic nuclei in hypothalamus

Antidiuretic hormone storage location

posterior pituitary

Antidiuretic hormone target cells

kidneys

Antidiuretic hormone function

water retention (decreased urinary output to preserve water in body), water reabsorption, stimulates release of adrenocorticotropic hormone (ACTH)

Oxytocin production location

paraventricular nuclei in hypothalamus

Oxytocin storage location

posterior pituitary

Oxytocin target cells

reproductive organs

Oxytocin function

• "love hormone”: bonding among peers

• increased milk production

• stimulates uterine contractions

Inhibitors of oxytocin

stress, fright, ethanol

Thyroid gland location

anterior neck

Thyroid gland functional unit

follicles

Thyroid hormone synthesis site

Follicular cells of thyroid

Thyroid hormone function

maintain basal metabolic rate (BMR) and regulation of growth

Thyroid hormone: T3 (Triiodothyronine)

Produced by: Thyroid gland

Target cells: Nearly all tissues

Function: Stimulates proteins synthesis, increases BMR/metabolic rate, and quick

Less abundant than T4

Thyroid hormone: T4 (Thyroxine)

Produced by: Thyroid gland

Target cells: Nearly all tissue

Function: Slowly increases BMR but lasts longer than T3

More abudant than T3

Parathyroid hormone production location

Parathyroid gland

Parathyroid hormone target cells

bones, kidneys, and intestines

Parathyroid hormone function

increase blood calcium levels

• stimulates osteoclasts to caused bone resorption

Calcitonin production location

parafollicular cells of parathyroid gland

Calcitonin target cells

bones, kidneys, intestines

Calcitonin function

decrease blood calcium levels

• bone deposition

• lengthens the lifespan of osteoblasts

Relationship between calcitonin and parathyroid hormone (PTH)

antagonistic

Two requirements for thyroid hormone

• tyrosine

• iodine

Thyroid stimulating hormone (TSH) production location

anterior pituitary

Thyroid stimulating hormone (TSH) target cells

thyroid gland

Thyroid stimulating hormone (TSH) function

acts on thyroid follice cells to increase thyroid hormone (T3/T4) synthesis

Effects of T3 of and T4

• increased BMR

• bone growth and maturation

• neural tissue maturation

• location