Ch 16: The Endocrine System

what is the endocrine system

a network of glands that produce and release hormones, control many important body functions

hormones

the stuff that controls everything outside of the nervous system

endocrine glands

pituitary, thyroid, parathyroid, adrenal, pineal, thymus

where does hormonal influence reach?

it reaches every cell in the body, and its affects can be seen for years

what are two “crines” that are not considered hormones? why?

autocrines—cell signals that work on themselves
paracrines—cell signals that work on cells nearby

hormones are long-distance chemical signals, these are short-distance

types of hormones

amino acid based and steroids

amino acid based hormones

act at the surface of the cell via 2nd messengers

amines, thyroxine, peptide, protein hormones

protein based, water soluble

transported and DISSOLVED in plasma, short half-life (seconds to minutes)

steroid hormones

act inside the cell via direct gene activation

fat and not water soluble

gonadal and adrenocortical hormones

BOUND to plasma proteins, long half life (hours)

target cell specificity

hormones circulate to all tisues but only active cells called target cells

target cells have specific receptor to bind to the hormone

the receptors can be intracellular or on the surface

mechanism of hormone action, how do hormones change cells?

alter plasma membrane permeability via ion channels

stimulate protein synthesis

activate or deactivate enzyme systems

induce secretory activity

stimulate mitosis

what mechanisms do hormones use to alter target cells

1. secondary messengers (amino acid/protein-based hormones)

2. direct gene activation

secondary messengers

hormone binds to the protein receptor

intracellular proteins are the messengers

activated protein which triggers target cell

direct gene activation

steroid/thyroid hormones

steroid hormone comes through the plasma membrane and connects directly to receptor protein

receptor protein binds to DNA sequence and initiates transcription

what three stimuli can trigger hormone release in glands

humeral stimuli

neural stimuli

hormonal stimuli (most complex)

humoral stimuli

secretion of hormones in response to changin blood levels of ions/nutrients

regulates calcium

neural stimuli

released by nerve/nervous system even

sympathetic fibers stimulate the adrenal gland to secrete hormones

much faster response

Hormonal stimuli

release of hormones in response to another hormone

tropic hormone is a hormone that releases another hormone

pituitary gland

pea-shaped, two-lobed organ that secrets nine major hormones

connected to the hypothalamus via a stalk

parts of pituitary gland

2 lobes:
Posterior lobe—neural tissue that recieves, store, and releases hormones from the hypothalamus and makes ADH and oxytocin

Anterior lobe—glandular tissue that synthesizes and secretes its own hormones, has direct vascular connection

What hormones does the pituitary gland produce

GH
TSH
ACTH
FSH
LH
PRL

what is oxytocin

strong stimulant of uterine contraction, triggers milk production in women

what is ADH

prevents urine formation, retain water and blood pressure increases (antidiuretic)

what is GH

growth hormone

anabolic effects on growth and metabolism

indirectly stimulates liver to produce insulin-like growth factors (at epiphyseal plate, cartilage formation, mitosis

directly promotes lipolysis and glycogen catabolism (fat and sugar breakdown)

what is TSH

theyroid gland

TRH (releasing hormone) from hypothalamus travels from anterior pituitary, hormone releases from thyroid into blood

thyroid hormones and calcitonin

what is ACTH

stimulates adrenal gland to release corticosteroid hormones

response to days-long stresses

what are FSH and LH

they are gonadotropins that are triggered by GnRH from the hypothalamus

both stimulate testosterone and estrogen for gamete production

LH stimulates ovulation

what is PRL

prolactin

milk production by the breasts, mammary gland growth, particularly high at. theend of pregnancy

thyroid gland

largest endocrine gland

located anterior neck below adams apple

makes TH and calcitonin

two lateral lobes connected by isthmus

what is TH

regulates the body’s basal metabolic rate

• glucose oxidation

• increasing metabolic rate

• heat production (sets core body temp)

too much: anxiety and sleeplessness
not enough: depression

how is TH made?

follicle cells produce thyroglobulin

colloid (thyroglobulin. andiodine) fills the lumen (empty space) of the follicles

TH is made and parafollicular cells are secreted to make calcitonin

what is calcitonin

in response to high blood calcium

reduces calcium

too much calcium causes heart, muscle, and bone problems

how does calcitonin lower blood calcium

1. target kidneys, prevents calcium reabsorption by urinating out access calcium

2. target bones by promoting accumulation of calcium in the bone by inhibiting clast cells and promoting blast cells

3. targets GI tract

what is the parathyroid gland

tiny gland embedded in the posterior aspect of the thyroid

raises calcium levels in blood

how to PTH raise blood calcium?

1. makes kidney reabsorb calcium back into blood

2. increases clast activity to release more calcium in the blood

3. GI for reabsorption

adrena glands and parts

paired, pyramid shaped organs atop the kidneys

hormones regulate electrolyte balance and stress responses

two glands in one:
1. adrenal medulla
2. adrenal cortex

adrenal medulla

nerve controlled, makes catecholamines, for short term stress

makes epinepherine and norepinephrine

prepare the body for physical activity (fight or flight)

adrenal cortex and layers

hormonally controlled, makes corticosteroids, long term stress

3 layers of tissue:
1. zona glomerulosa, regulates sodium, mainly aldosterone
2. zona fasciculata, regulates sugar, mainly cortisol
3. zona reticularis, gonadicorticoids

mineralocorticoids

aldosterone to target the kidneys

regulates electrolyte levels in ECM

maintains sodium levels by reducing excretion

blood volume and pressure increase

what are the pathways for aldosterone release

ACTH and RAA Pathway

what is the RAA Pathway

renin-angiotensin mechanism causes kidneys to release renin

activates angiotensin I

ACE from lungs turn it into angiotensin II

aldosterone is released and secreted by the adrenal gland

what organs are apart of the RAA Pathway

liver, kidneys and lungs

why is the RAA Pathway activated?

in response to low Na and low blood pressure/volume

potassium out

glucocorticoids

releases cortisol, long term stresses

cortisol helps regulate glucose levels in blood

mobilizes energy by increasing blood sugar levels

cortisol prevents the release of substances in the body that cause inflammation

pancreas

insulin and glucagon to regulate blood sugar day-to-day

between the kidneys, partially behind the stomach

composed of acini and islets (islets have hormonal function)

digestive and endocrine

what do A, B, D, and F cells secrete

A cells—glucagon

B cells—insulin

D cells—somatostatin

F cells—pancreatic polypeptide

glucagon

raises blood sugar via liver action

hyperglycemic agent breaks down glycogen, which is high between meals and during fasting

triggered by decreased blood glucose levels

how does glucagon target the liver

1. glycogenolysis—breaks down sugar storage

2. gluconeogenesis—occurs in the liver, makes glucose from fat and other things

glucose is released into blood

insulin

secreted when blood glucose levels rise, usually after a meal

acts to reduce blood glucose levels

how does insulin reduce blood glucose levels

1. enhances membrane of transport of glucose into tissue (taken out of blood)

2. inhibits breakdown of glycogen. toglucose (inhibits glycogenesis)

3. inhibits conversion of amino acids or fats to glucose

Gonads (female)

paired ovaries producing estrogen and progesterone

maturation of organs (breast enlargment and uyerus development)

appearance of sexual characteristics

menstrual and uterine cycle

Gonads (male)

testes produce testosterone

initiates maturation of male reporductive organs

causes appearance of secondary sexual characteristics and sex drive

necessary for sperm production

maintains sex organs and their functional state

Pineal gland

secretes melatonin

day/night cycle, rhythmic variations of sleep/awake patterns

physiological processes that show rhythmic variations (like body temp, sleep, and appetite)

Thymus

numerous hormones involved in the development of T-cells

lobulated gland located deep to the sternum

Heart

produces atrial natriuretic peptide (ANP) via elevated BP

reduces blood sodium concentration, BV. and BP

outputs from the heart

1. natriuresis—elevated sodium. inthe urine

2. diuresis—enhances urinary output, lowers BV/BP

3. vasodilation—shuts down renin release

Kidneys

secrete erythropoietin (EPO)

regulates red blood cells in bone marrow, keeps levels up

Diabetes

type 1: cannot make insulin because of pancreatic problems

type 2: canno use insulin due to fat blockage