A&P2 - Endocrine System

What are the MAJOR endocrine glands?

Pituitary, thyroid, parathyroid, adrenal, pancreas, pineal, thymus, ovaries, testes

Why is the endocrine system considered unique?

organs are not anatomically connected

What does the endocrine system generally do?

(along with the nervous system,) regulates functions of the body to maintain homeostasis and coordinates communication

What are the endocrine glands?

cells, tissues, and organs (that make up endocrine system)

Do endocrine glands have ducts or are ductless? which means?

ductless, meaning they secrete directly into the bloodstream

What does endocrine mean?

internal secretion

What are the exocrine glands?

glands that secrete into ducts or tubes that lead to a body surface

What does exocrine mean?

secrete externally

Because exocrine glands have ducts, what does that mean in terms of their transportation?

they deliver directly to a specific site

What are local hormones?

hormones that are secreted internally

Paracrine secretions affect what?

nearby cells (“neighborhood”)

Autocrine secretions affect what?

only the cells that secrete them

Example of an endocrine gland:

thyroid gland

Example of an exocrine gland:

sweat gland

What makes the nervous and endocrine system similar?

• function in communication

• communicate via chemical messengers that bind to receptors

What makes the nervous system different from endocrine?

• releases neurotransmitters

• respond faster

What makes the endocrine system different from nervous?

• secretes hormones

• effects last longer

Hormone(s) released by the hypothalamus:

CRH, GnRH, SS, GHRH, PIH, PRF, TRH

Hormone(s) released by the anterior pituitary gland:

ACTH, FSH, GH, LH, PRL, TSH

Hormone(s) released by the posterior pituitary gland:

ADH, OT

Hormone(s) released by the thyroid gland:

calcitonin, T₄, T₂

Hormone(s) released by the parathyroid gland:

PTH

Hormones(s) released by the adrenal medulla:

EPI, NE

Hormone(s) released by the adrenal cortex:

aldosterone, cortisol

Hormone(s) released by the pancreas:

glucagon, insulin, SS

What is another name for the posterior pituitary gland? and why?

neurohypophysis; anatomically connected to hypothalamus

What is another name for the anterior pituitary gland?

adenohypophysis

Hormones are released… then diffused…

released into ECF then diffused into blood

Why does the transport method differ for certain hormones?

depends on their solubility; lipid-soluble or water-soluble?

At what concentration do hormones have an effect?

low concentrations

What type of compound are hormones?

organic

What are the general types of hormones?

steroid or steroid-like, nonsteroid

What are steroids?

lipids containing complex rings of carbon and hydrogen atoms

What produces steroid hormones?

cholesterol

Examples of steroid hormones:

sex hormones, adrenal cortex hormones

What are the 4 types of nonsteroid hormones?

amines, proteins, peptides, glycoproteins

Where are amines derived from?

tyrosine (amino acid)

How do hormones exert effects internally?

by altering metabolic processes such as:

• enzyme activity

• rate of membrane transport of a substance

Where can hormones bind to receptors at target cell?

in cell —> steroid

on cell —> nonsteroid

What determines the strength of response to a hormone? and can it change?

number of receptors; yes

How can the number of receptors in target cell change (to maintain homeostasis)?

upregulation —> increase

downregulation —> decrease

What are the similarities between steroid and thyroid hormones?

• poor water-solubility

• transported by plasma proteins thru blood

• binds to receptors in cell

• causes transcription

How is transportation through the cell membrane for thyroid hormones different from steroids?

thyroids enter by specific transport methods, while steroids diffuse through lipid bilayer

The nonsteroid hormone when binding to receptors is itself considered a…

first messenger

The chemical that induces changes leading to hormone’s effect is considered a…

second messenger

Many hormones use what as a second hormone?

cyclic adenosine monophosphate (cAMP)

What is signal transduction?

entire process of chemical communication from outside to inside cell

Why do people abuse steroids to improve athletic build?

to increase muscular strength

What are the harmful effects of using steroids to improve athletic performance?

• decreasing natural testosterone production

• stunting growth

• male breast development

• male sexual developments in females

• damage to kidney, liver, heart

• increase in LDL cholesterol

• psychiatric problems

Why do people abuse growth hormone to improve athletic performance?

to enlarge muscles

What can be used instead of or with steroids to improve athletic performance?

growth hormone

Why do people abuse erythropoietin to improve athletic performance?

to increase the number of red blood cells and oxygen delivery to muscles

What conditions can erythropoietin be used to treat?

certain forms of anemia

What are the harmful effects of abusing erythropoietin?

lead to heart attack and death

What are prostaglandins?

hormone-like substance

What type of substance are prostaglandins?

paracrine

Where are prostaglandins stored?

not stored in cells but synthesized before release

What happens to prostaglandins after use?

rapidly inactivated

How do prostaglandins affect cells?

regulate cellular response to hormones

How do prostaglandins affect the cell’s response to hormones?

• activate or inhibit adenylate cyclase

• control cAMP production

What are the effects of prostaglandins?

• contracting or relaxing smooth muscle

• stimulating or inhibiting secretion

• regulating BP

• controlling movement of H₂O and NA+ in kidneys

• promoting inflammation

Is hormone secretion regulated precisely?

yes

What is hormone secretion primarily controlled by?

negative feedback mechanisms

How long can the effects of hormone secretion last?

short-lived (few minutes) or days

How are secretions handled after exerting their effects?

excreted through urine

How can the effects from hormone secretions be stopped?

broken down by enzymes from liver

What is negative feedback in hormone secretion?

a control mechanism in which rising level of a hormone leads to a decrease in hormone secretion

What happens as a hormone is used up?

inhibition stops and secretion begins again

What are the methods of negative feedback control of hormone secretion?

1. hypothalamus

2. nervous system control

3. changes in composition of internal environment

Describe the negative feedback control by the hypothalamus

• hypothalamus release anterior pituitary hormones

• pituitary hormones secrete hormones that control activity of other glands

What are tropic hormones?

hormones that act on other glands

Describe the path of the negative feedback control from the hypothalamus

hypothalamus → anterior pituitary gland → peripheral endocrine gland → target cells → action

Describe the negative feedback control by the nervous system

nervous system directly stimulates some glands to secrete their hormones via nerve impulses

Describe the path of the negative feedback control from the nervous system

nervous system → endocrine gland → target cells → action

Describe the negative feedback control by changes in composition of internal environment

changes level of a specific substance in the blood which stimulates or inhibits secretion of certain hormones

Describe the path of negative feedback control from changes in composition of internal environment

changing level of substance in plasma → endocrine gland → target cells → action

What is a positive feedback in hormone secretion?

control mechanism in which rising level of a hormone leads to an increase in secretion; used mainly in reproductive system

Where is the pituitary gland located?

lies at the base of the brain, in sella turcica of sphenoid bone

What is it controlled by? and what does that mean?

controlled by brain, part of nervous system

What is the pituitary gland attached to and how?

attached to hypothalamus by pituitary stalk

What is the infundibulum?

pituitary stalk

What are the distinct portions of the pituitary gland?

anterior → adenohypophysis

posterior → neurohypophysis

Is secretion the same in the 2 pituitary lobes?

no, different methods by the hypothalamus

Characteristics of the small intermediate (pituitary) lobe

• pars intermedia

• develops in fetus

• produces melanocyte-stimulating hormone, which starts melanin production

How are hormones released by the hypothalamus transported to the anterior (pituitary) lobe?

through the Hypophyseal Portal Veins

How are nerve impulses released by the hypothalamus transported to the posterior (pituitary) lobe?

through the infundibulum