Endocrine System (unit 1) Flashcards
Ligand
Chemical messenger
Communication of the nervous system
A nerve signal causes neurotransmitter release from a neuron into the synaptic cleft
other features of the nervous system
targets other neurons, muscle and gland cells
response time is rapid
localized effects
short duration
Communication of the endocrine system
secretes hormone into the blood, hormones transported are then distributed throughout to target cells
other features of the endocrine system
targets any cell with a receptor
relatively slow reaction time
widespread effects
long lasting
general functions of endocrine system
- regulation of growth metabolism and development
- maintaining homeostasis of blood composition and volume
- controlling digestive processes
- controlling reproductive processes
Hormonal stimulation
releasing a hormone in response to another hormone
Humoral stimulation
release of a hormone in response to changes in level of nutrient or ion in the blood
Nervous system stimulation
release of a hormone based on nervous stimulation
steroids
lipid soluble
formed from cholesterol
ex. estrogen, progesterone, testosterone, cortisol, aldosterone
biogenic amine
water soluble
ex. norepinephrine, epinephrine, TH
Proteins
water soluble
amino acid chains
ex: antidiuretic hormone, insulin,glucagon
Lipid soluble hormones
use carrier proteins
-dont dissolve in blood easily
-carriers are water soluble protein produced by liver
-binding is temporary
-must be unbound to bind with target
Water soluble hormones
travel freely in blood
Hormone synthesis
is done by the gland
Hormone elimination
-carried out by enzymatic degradation in the liver
-removal from blood by kidneys excretion or target cell uptake
Half-life
time necessary to reduce a hormone’s concentration to half of its original level
-water soluble hormones have shorter half lives
-steroid hormones generally have a longer half life
Responses to water soluable hormone pathway
- Enzymes activated or inhibited
- Growth is stimulated (cell division)
- Cellular secretions may be released
- Membrane permeability may be changed
- Muscles can be contracted or released
Intracellular enzyme cascade
signal is amplified at each step
there are many places to regulate pathway activities
Signaling pathways
Cells possess mechanisms to quickly
inactivate intermediate
A cell’s response to a hormone varies with
-Its number of receptors for the hormone
-Its simultaneous response to other hormones
Up regulation
increases cell’s receptors
- makes cell MORE sensitive
Down regulation
Decreases cell receptors
- makes cell LESS sensitive
Synergistic interactions
One hormone reinforces activity
of another hormone
Permissive interactions
One hormone requires activity of
another hormone
Antagonistic interactions
One hormone opposes activity of
another hormone
Pituitary gland
Inferior to hypothalamus
connected via infindibulum
anterior and posterior lobes
Posterior pituitary
Smaller part of pituitary gland, directly connected to hypothalamus
-Cell bodies found in the paraventricular nucleus (oxytocin) and supraoptic nucleus (ADH)
-Axon extends through the infundibulum via the hypothalamo-hypophyseal tract
-Terminals in the pars nervosa of the posterior pituitary
Anterior pituitary
Larger part of pituitary
-Partitioned into three areas:
-Pars distalis, pars tuberalis, pars intermedia
-Hypothalamo-hypophyseal portal system of blood vessels
posterior pituitary hormones
Oxytocin and antidiuretic hormone are synthesized in the neurosecretory cells of the hypothalamus and shipped to the posterior pituitary for storage and release
Oxytocin
uterine contraction, milk ejection, emotional bonding
Antidiuretic hormone
decrease urine production, stimulate thirst, constrict blood vessels
Regulatory hormone
secreted by hypothalamus
travel to the anterior pituitary
can be
1. releasing hormones
increases anterior pituitary’s release of hormone
2. inhibiting hormones
decreases anterior pituitary’s release of hormone
Anterior pituitary hormones
Thyrotropin releasing hormone (TRH)
Prolactin releasing hormone (PRH)
Gonadatropin releasing hormone (GnRH)
Corticotropin releasing hormone (CRH)
Growth Hormone releasing hormone (GHRH)
Prolactin Inhibiting hormone (PIH)
Growth hormone Inhibiting hormone (GHIH)
Hepatocytes
Liver cells that release IGF (insulin like growth factor) increase glucogenisis and lysis, increases blood glucose when targeted by GH
Thyroid
Largest endocrine organ
left and right lobes connected by isthmus
Follicular cells
-Produce and release Thyroid hormone (TH)
-TH is synthesized in follicular cells from a combination of iodine and thyroglobulin
-TH is stored in the follicular cells until release is stimulated by TSH
Thyroid hormone
TH increases metabolic rate and body
temperature
Parafollicular cells
Cells around follicular cells that make calcitonin
calcitonin
Hormone that decreases blood calcium
levels
Hypothalamic-pituitary-thyroid axis
◦ Cold temperature, pregnancy, high altitude, hypoglycemia, or low TH cause hypothalamus to release TRH (thyrotropin releasing hormone)
◦ TRH causes anterior pituitary to release TSH which travels to the thyroid and causes a release of TH from follicular cells
Net effects of TH
-Increased protein synthesis (especially in neuronal tissue), rise in temperature, increased glucose uptake, increased metabolic rate, increased oxygen demand to facilitate aerobic cellular respiration.
-Negative feedback of TH decreases TRH release
Adrenal medulla
inside
◦ Red-brown color due to extensive blood vessels
◦ Releases epinephrine and norepinephrine with sympathetic stimulation
Adrenal cortex (outside)
◦ Synthesizes and releases corticosteroids
◦ Yellow color due to lipids within cells
◦ Three zones:
◦ Zona glomerulosa
◦ Zona fasiculata
◦ Zona reticularis
Hormones of the Adrenal cortex
corticosteroids
Corticosteroids
Mineralocorticoids
Gonadocorticoids
Glucocorticoids
Mineralocorticoids
hormones that regulate electrolyte levels
◦ Aldosterone regulates Na+ and K+ retention in body
Gonadocorticoids
sex hormones
◦ Androgens are male sex hormones converted to estrogen in females
◦ Amount of androgen produced by adrenals is less than amount from testes
Glucocorticoids
hormones that regulate blood sugar
◦ Cortisol increases nutrient levels in the blood
cortisol release
CRH stimulates anterior pituitary to release ACTH
◦ ACTH stimulates adrenal cortex to release cortisol and corticosterone
Cortisol
Resists stress and helps to repair tissue
Net effects of cortisol
increase of all nutrient levels in the blood
◦ Liver cells increase glycogenolysis and gluconeogenesis; decrease glycogenesis
◦ Adipose cells increase lipolysis and decrease lipogenesis
◦ Many body cells break down proteins to amino acids
◦ Liver cells use the amino acids for gluconeogenesis
◦ Most cells decrease their glucose uptake, sparing it for brain
Pancreas
Contains alpha, beta and delta cells
help maintain blood glucose
Alpha cells
release glucagon
Beta cells
release insulin
delta
secrete somatostatin
(inhibits insulin and glucagon release)
Insulin
lowers blood glucose
Glucagon
raises blood glucose
How does insulin lower blood glucose
◦ Hepatocytes remove glucose from blood; store it as glycogen
◦ Glycogenesis stimulated; glycogenolysis and gluconeogenesis inhibited
◦ Adipose cells store fat
◦ Lipogenesis stimulated
and lipolysis inhibited
◦ Most body cells increase nutrient uptake in response to insulin
How Glucagon Raises Blood Glucose
◦ Alpha cells detect drop in blood glucose and release glucagon
◦ Glucagon acts through 2nd messengers causing body cells to release stored
nutrients into blood
◦ Hepatocytes release glucose
◦ Glycogenolysis and
gluconeogenesis stimulated;
glycogenesis inhibited
◦ Adipose cells release fatty acids
and glycerol
◦ Lipolysis stimulated, while
lipogenesis inhibited
Pineal gland
a small unpaired body in the epithalamus of the diencephalon
-Pineal secretes melatonin at night
◦ Causes drowsiness, regulates circadian rhythm
Parathyroid glands
are small structures on the back of the thyroid gland
contain chief cells
chief cells
make PTH
PTH
Increases blood calcium
calcitonin
decreases blood calcium
Thymus cells
secrete thymosin
◦ Helps with maturation of white blood cells
Kidney secretes
erythropoietin (EPO)
◦ EPO causes increased red blood cell production
Stomach secretes
gastrin
◦ Gastrin increases secretion and motility in stomach for digestion
Skin produce
Vitamin D3
◦ Converted to calcitriol (synergistic to PTH)
Liver secretions
angiotensinogen
◦ Helps raise blood pressure when it starts to fall
Small intestine secretes
secretin
and cholecystokinin (CCK)
Secretin
stimulates secretion of
bile and pancreatic juice
CCK
CCK stimulates release of bile
from gall bladder
Adipose connective tissue
secretes
leptin
leptin
controls appetite
Heart produces
atrial natriuretic peptide
atrial natriuretic peptide
decreases BP
Ovaries secrete
Estrogen & progesteron + Inhibin
Testes secrete
Testosterone and Inhibit
