Ch. 49 Chemical Signals in Animals Flashcards
endocrine system
gland & tissues that produce/secrete hormones into the bloodstream
hormone
any of many different signaling molecules that circulate throughout the plant or animal body
- can trigger characteristic responses in distant target cells @ very low concentrations
- controlled
- big size
- specific function
- result in longer response than the action potential of the CNS
- long lasting effect
- chemical signal
animal chemical signals
1) present in extremely low concentrations
2) have enormous effects on their target cells
properties of electrical impulses
1) short-term effect
2) fast response
major categories of chemical signals
- grouped based on effect produced on cell/organ
1) autocrine signals
2) paracrine signals
3) endocrine signals
4) neural signals
5) neuroendocrine signals
autocrine signal
a chemical signal that affects the same cell that produced/released it
(ie) cytokines
cytokine
(autocrine) any of a diverse group of signaling proteins
- secreted largely by cells of the immune system
- stimulates leukocyte production
- recruits cells to site of infection, tissue repair & fever
- FCN: regulate the type, intensity & duration of an immune response
- amplify the response of a cell to a stimulus
paracrine signal
a chemical signal that diffuse locally& affects neighboring cells
(ie) insulin, glucagon & somatostatin
insulin
a peptide hormone produced in pancreas in response to HIGH levels of GLUCOSE in blood
- enables cells to absorb glucose
- coordinates synthesis of fats, proteins & glycogen
- paracrine signal
- produced by islets of Langerhan
glucagon
a peptide hormone produced by the pancreas in response to LOW blood GLUCOSE
- raises blood glucose by triggering breakdown of glycogen & stimulating gluconeogenesis
- paracrine signal
- produced by islets of Langerhan
somatostatin
a hormone secreted by the pancreas & hypothalamus that inhibits the release of several other hormones
- paracrine signal
- produced by islets of Langerhan
islets of Langerhans
cells in the pancreas that produces insulin, glucagon & somatostatin
endocrine signal
a chemical signal (hormone) that is released into the bloodstream by a producing cell (gland)
- acts on a distant target cell
- most common
- most effective
neural signal
neurotransmitters that diffus a short distance from presynaptic cell to a postsynaptic cell, where it binds to a membrane receptor & results in a change in the membrane potential
- very fast
- short-lived
*synapse
neuroendocrine signal
nerve cells (neurons) that release hormones into the blood or to hormones themselves
- considered hormones
- carried by blood & otro body fluids
- act on distant cells
- do not act on/at synapse
(ie) antidiuretic hormone
(aka) neurohormone
“nerve inside separated”
antidiuretic hormone (ADH)
a peptide hormone, secreted from the posterior pituitary gland
- stimulates water retention by the kidney
(aka) vasopressin
hormone signaling pathways
1) endocrine pathway
2) neuroendocrine pathway
3) CNS-to-endocrine pathway
endocrine pathway
sends hormones directly from endocrine cells to effector cells
signal -> endocrine cell -> effector cell
neuroendocrine pathway
releases neuroendocrine signals that act directly on effector cells
signal -> sensor cell -> CNS -> effector cell
hormones in insects regulate _____.
molting & metamorphosis
CNS-to-endocrine pathway
neuroendocrine signals stimulate cells in the endocrine system, which respond by producing an endocrine signal that acts on effector cells
stimulus -> receptor cell -> endocrine cell -> effector cell
steps to shutting down a hormone
1) hormones produced by effector cells feed back to endocrine cells, lowering hormone production
2) effector hormone also feeds back to neuroendocrine & neuroendocrine-to-endocrine pathways
3) endocrine signals are released in response to electrical signals, which modulate the signal from the nervous system
endocrine gland
a gland that secretes hormones directly into the bloodstream or interstitial fluid instead of into ducts
hormones in insectes regulate _____.
molting & metamorphosis
major human endocrine glands
1) pituitary gland
2) thyroid gland
3) parathyroid gland
4) kidney
5) adrenal gland
6) pancreas
pituitary gland
a small gland located directly under the brain
- physically/functionally connected to hypothalamus
- produces/secretes hormones that affect many other glands & organs
- regions: anterior & posterior
thyroid gland
a gland in the neck that releases thyroid hormone (increases metabolic rate) and calcitonin (lowers blood calcium)
parathyroid gland
a part of the thyroid gland
- controls calcium levels (calcitonin)
polypeptide
a chain of 50+ amino acids linked juntos by peptide bonds
- nonsoluble lipids
- need receptor
- acts @ cell surface
amino acid derivative
- not lipid soluble
- bind to receptors located in the membranes of target cells
- acts @ cell surface
steroid
a class of lipid w/ a characteristic 4-ring hydrocarbon structure
- large molecule
- lipid soluble
- acts inside cell
kidney
one of a paired organ situated @ back of abdominal cavity
- filters blood
- produces urine
- secretes several hormones
- attached to adrenal glands
adrenal glands
endocrine glands
- sit on top of kidneys
- cortex secretes steroid hormones
- medulla secretes epinephrine & norepinephrine
major human endocrine glands
1) pituitary gland
2) thyroid gland
3) parathyroid gland
4) kidney
5) adrenal gland
6) pancreas
7) ovary
8) testes
pancreas
a large gland in vertebrates that has both exocrine & endocrine functions
- secretes digestive enzymes into a duct connected to the intestine
- secretes several hormones (insulin & glucagon) into the bloodstream
a single hormone can
exert a variety of effects
ovary
egg-producing organ of a female animal
seed-producing structure in female part of a flower
testis
sperm-producing organ of a male animal
exocrine gland
a gland that secretes some substance through a duct into a space other than the circulatory system
- major role in puberty acne
(ie) digestive tract or skin surface
chemical families
1) polypeptides
2) amino acid derivatives
3) steroids
secretin
a peptide hormone produced by cells in the small intesting in response to the arrival of food from the stomach
- stimulates secretion of bicarbonate (HCO3) from the pancreas
epinephrine
a catecholamine hormone produced & secreted by adrenal medulla
- triggers rapid responses related to fight-or-flight response
(aka) adrenaline
thyroxin (T4)
a lipid-soluble hormone derived from the amino acid tyrosine
- produced/secreted by thyroid gland
- regulates cellular metabolism
- (humans) converted to active triiodothyronine (T3) in the liver
- lipid soluble
thyroxin (T4)
a lipid-soluble hormone derived from the amino acid tyrosine
- produced/secreted by thyroid gland
- regulates cellular metabolism
- (humans) converted to active triiodothyronine (T3) in the liver
- lipid soluble
to affect a target cell, all polypeptides & most amino acids derivatives
bind to receptor on the cell surface
lipid-soluble hormone (steroids) can diffuse
through the plasma membraane & bind to receptors inside the cell
growth hormone (GH)
a peptide hormone produced/secreted by anterior pituitary
- promotes lengtheing of long bones in children and muscle growth, tissue repair & lactation in adults
- stimulates mitosis & growth
- determines how fast to grow
(aka) somatotropin
what happens when the pituitary gland of an animal is removed?
animal stops growing
single hormone can
exert a variety of effects
several hormones may
affect the same aspect of physiology
hormones coordinate the activities of cells in 3 areas
1) development growth & reproduction
2) response to environmental challenges
3) maintenance of homeostasis
growth + sex hormones
- promotes cells division
- promotes growth
- promotes sexual differentiation
metamorphosis
transition from 1 developmental stage to another
- requires a lot of energy
- (during) immune system shuts down, makes more susceptible to diseases/viruses
(ie) larval to adult form of an animal
triiodothyronine (T3)
thyroid hormone responsible for most changes observed in metamorphosis
- produced in response to signals from brain
- lipid soluble
- derived from amino acid tyrosine
- increases cellular metabolism
- has stronger effect than thyroxine (T4)
ways juvenile amphibians resond to increased levels of T3
1) grow & form new structures: legs
2) cells die: tadpole tail
3) cell change structure & function
larva
an immature stage of an animal species in which the immature & adult stages have different body forms
- juvenile stage
pupal case
a tough case that juveniles secrete during metamorphosis
metamorphosis depends on interactions between
juvenile hormone (JH) & ecdysone
juvenile hormone (JH)
an insect hormone that prevents larvae from metamorphosing into adults
ecdysone
an insect hormone that triggers either molting (to a larger larval form) or metamorphosis (to the adult form)
- depends on the level of juvenile hormone (JH)
if juvenile hormone (JH) levels are high, ecdysone triggers _______.
growth of juvenile by molting
if juvenile hormeon (JH) levels are low, ecdysone triggers ________.
metamorphosis and the transition to adulthood & sexual maturity
types of metamorphosis
1) complete
2) incomplete
incomplete metamorphosis
a type of metamorphosis in which the animal increases in size from one stage to the next, but does not dramatically change its body form
(aka) hemimetabolous metamorphosis
(ie) humans & animals
complete metamorphosis
a type of metamorphosis in which the animal completely changes its form
- includes a distinct larval stage
(aka) holometabolous metamorphosis
(ie) butterfly
primary sex determination
events early in development that dictate whether the sex organs (gonads) of the vertebrate embryo become male or female
- depends on genes on sex chromosomes
hormone produced by testes
1) testosterone
2) Mullerian inhibitory substance
testosterone
a steroid hormone
- produced/secreted by testes
- stimulates sperm production, various male traits & reproductive behaviors
Mullerian inhibitory substance
a peptide hormone
- secreted by embryonic testis
- causes regression (withering away) of the female reproductive ducts
estradiol
major estrogen
- produced by ovaries
- stimulates development of female reproductive tract, growth of ovarian follicles & growth of breast tissue in mammals
sex hormones play a role in
the juvenile to adult transition
(ie) puberty
sex hormone play a key role in:
1) development of the reproductive tract in embryos
2) reproductive tract maturation during transition from childhood to adulthood
3) regulation of spermatogenesis & oogenesis in adults
puberty
the various physical & emotional changes that an immature human undergoes in reaching reproductive maturity
- period when such changes occur
photoperiod
the amount of time per day (usually in hours) that an organism is exposed to light
- stimulates release of sex hormones in some mammals, birds & lizards
how photoperiod affects sex hormone release
1) photoreceptors send signals to the hypothalamus
2) hypothalamus initiates a series of signals that stimulate sex hormone production
3) in some animals, the photoreceptors are located in the retina, which signals the pineal gland
4) pineal gland secretes melatonin, which sends signals to the hypothalamus
pineal gland
an endocrine gland located in the brain
- detects light
- secretes/activates melatonin based on amount of light
melatonin
a hormone produced by the pineal gland
- regulates sleep/wake cycles
- regulates seasonal reproduction in vertebrates
- maximum secretion occurs at night
- concentration decreases during daylight hours
a decline in melatonin stimulates hypothalamus, which causes
sex organs to produce sex hormones
endocrine disruptor
an exogenous chemical that interferes w/ normal hormonal signaling
- many are xenoestrogens
xenoestrogen
foreign chemicals that bind to estrogen receptors or otherwise induce estrogen-like effects
examples of endocrine disruptor
1) atrazine, an herbicide - causes reproductive abnormalities
2) bisphenol (BPA) - causes abnormal development of the brain & reproductive tissue
fight-or-flight response
rapid physiological changes that prepare the body for emergencies
- increased heart rate
- increased blood pressure
- decreased digestion
- triggered by sympathetic nervous system
epinephrine
a catecholamine hormone produced/secreted by adrenal medulla
- triggers rapid responses related to the fight-or-flight response
- short-term stress
(aka) adrenaline
cortisol
a steroid hormone produced/secreted by the adrenal cortex
- increases blood glucose
- prepares body for stress
- major glucocorticoid hormone
- ensures continued availibility of glucose for the brain
- may cause cardiovasuclar disease
- long-term stress
(aka) hydrocortisone
glucocorticoid
a class of steroid hormones
- produced/secreted by adrenal cortex
- increases blood glucose
- prepares body for stress
(ie) cortisol & cotricosterone
how cortisol controls blood sugar in humans
1) induces liver to produce enzymes that generate glucose from amino acids
2) changes adipose tissue & resting muscles resistant to insulin so they will not take in glucose
3) promotes the release of fatty acids for use by the heart & muscles
how are hormones involved in homeostasis?
1) sensory receptors monitor conditions relative to a set point
2) an integrator processes info from the sensor
3) effector cells return the condition to the set point
parabiosis
an experimental technique for determining whether a certain physiological phenomenon is regulated by a hormone
- consists of surgically uniting 2 individuals so that hormones can pass between them
- may also be natural (conjoined twins)
leptin
a hormone produced/secreted by fat cells (adipocytes)
- stabilizes fat-tissue mass by inhibiting appetite & increasing energy expenditure
- reduces appetite in response to increase in adipose tissue mass
If ADH is present, there will be a _______ (large/small) volume of urine.
small
If ADH is not present, there will be a _______ (large/small) volume of urine.
large
antidiuretic hormone (ADH)
a peptide hormone
- secreted from posterior pituitary gland
- stimulates water retention by the kidney
- increases permeability of the kidney’s collecting ducts to water (water reabsorbed from urine)
(aka) vasopressin
aldosterone
a hormone that stimulates the kidney to conserve salt & water (electrolyte)
- promotes sodium retention
- produced in adrenal cortex
mineralocorticoid
a class of steroid hormones
- produced/secreted by adrenal cortex
- regulate electrolyte levels & overall volume of body fluids
- related to aldosterone & adrenal hormones
erthyopoietin (EPO)
a peptide hormone
- released by kidney in response to low blood-oxygen levels
- stimulates bone marrow to produce more RBC
The more red blood cells, the _______ (higher/lower) the oxygen-carrying capacity of the blood.
higher
hormones are regulated by
CNS, brain & spinal cord
adrenocorticotropic hormone (ACTH)
a peptide hormone
- produced/secretedby anterior pituitary
- stimulates release of steroid hormones (cortisol/aldosterone) from adrenal cortex
corticotropin-releasing hormone (CRH)
a peptide hormone
- produced/secreted by the hypothalamus
- stimulates the anterior pituitary to release ACTH
what happens when feedback mechanism fails (CRH, ACTH, cortisol)?
there will be high levels of ACTH in the blood
epinephrine
a catecholamine hormone produced/secreted by adrenal medulla
- triggers rapid responses related to the fight-or-flight response
- released for short-term stress
(aka) adrenaline
cortisol
a steroid hormone produced/secreted by the adrenal cortex
- increases blood glucose
- prepares body for stress
- major glucocorticoid hormone
- ensures continued availibility of glucose for the brain
- may cause cardiovasuclar disease
- other tissues/organs become expendable (abandoned/destroyed)
- released for long-term stress
- inhibits CRH & ACTH
(aka) hydrocortisone
Cushing’s disease
a human endocrine disorder
- inability of cortisol to suppress hormone production
- caused by loss of feedback inhibition of cortisol on ACTH secretion
- high ACTH levels
- high cortisol levels
- wasting of body protein reserves
hypothalamic-pituitary axis
the functional interaction of the hypothalamus & anterior pituitary gland, which are anatomically distinct but work juntos to regulate most of the other endocrine glands in the body
neurosecretory cell
a neuron that produces/secretes hormones into the bloodstream
- primarily found in the hypothalamus
(aka) neuroendocrine cell
relationship btwn ADH & oxytocin
1) both produced by neurosecretory cells of the hypothalamus
2) stored in the posterior pituitary
3) released into the bloodstream
hormones that the anterior pituitary gland produces
1) ACTH
2) follicle-stimulating hormone (FSH)
3) lutenizing hormone (LH)
4) growth hormone (GH)
5) prolactin
6) thyroid-stimulating hormone (TSH)
follicle-stimulating hormone (FSH)
a peptide hormone
- produced/secrete by the anterior pituitary
- (females) stimulates growth of eggs & follicles
- (males) stimulates sperm production
lutenizing hormone (LH)
a peptide hormone
- produced/secreted by the anterior pituitary
- (females) stimulates estrogen production, ovulation & formation of the corpus lateum
- (males) stimulates testosterone production
prolactin
a peptide hormone
- produced/secreted by the anterioro pituitary gland
- (female) promotes milk production
- has a variety of effects on parental behavior
- has effect on seasonal reproduction in other vertebrates
thyroid-stimulating hormone (TSH)
a peptide hormone
- produced/secreted by the anterior pituitary
- stimulates release of thyroid hormones from thyroid gland
modes of controlling epinephrine
1) neurotransmitters change gene expression in neurons
2) hormones change gene expression in target cells
Differences in _________ of hormones influence where a target cells receives the chemical message
lipid solubility
estradiol
major estrogen
- produced by ovaries
- stimulates development of female reproductive tract
- (mammals) stimulates growth of ovarian follicles & growth of breast tissue
- most important estrogen
- receptor found only in the nucleus of the targeted tissue
estrogen
a class of steroid hormones
- includes: estradiol, estrone & estriol
- promote female-like traits
- secreted by gonads, fat tissue & otro organs
- lipid soluble
- enters cell through plasma membrane
characteristics of steroid hormones
1) lipid soluble
2) enter a target cell
3) bind to receptors inside the cell
4) causes a change in gene expression
zinc finger
a distinctive DNA-binding region for steroid-hormone receptors
how change in gene expression occurs
1) interfere w/ transcription
2) bind directly to DNA, the steroid hormone receptor complex binds to the hormone-response gene
phosphorylase
an enzyme that catalyzes the formation of glucose from glycogen by triggering a signal transduction cascade
- activated by epinephrine
cyclic adenosine monophosphate (cAMP)
a small molecule
- derived from ATP
- widely used by cells in signal transduction & transcriptional control
- second messenger
second messenger
a nonprotein signaling molecule produced/activated inside a cell in response to stimulation @ the cell surface
- commonly used to relay the message of a hormone or other extracellular signaling molecule
cAMP-dependent protein kinase A
(triggers signal transduction cascade)
enzyme that responds to cAMP
- phosphorylated phosphorylase kinase, which phosphorylates phosphorylase
steps leading up to signal transduction cascade
1) epinephrine binds to a surface receptor
2) the enzyme adenylyl cyclase (AC enzyme) is activated
3) the AC enzyme catalyzed ATP to cAMP
4) cAMP initiates the signal transduction cascade
signal transduction cascade
a series of enzyme-catalyzed phosphorylation reactions
- commonly used in signal transduction pathways to amplify
- convey a signal inward from plasma membrane
- diverse
- complex
steps leading up to signal transduction cascade
1) epinephrine binds to a surface receptor
2) the enzyme adenylyl cyclase (AC enzyme) is activated
3) the AC enzyme catalyzed ATP to cAMP
4) cAMP initiates the signal transduction cascade
model for phosphorylation cascade
1) cAMP transmits signal from the cell surface to the signaling cascade
2) cAMP + subsequent phosphorylation events amplify the original signal from epinephrine
