Download Chapter 45

Chapter 45
Chemical Signals in
Animals
Endocrine system
• regulates activity of target organs at distant sites
• secretes hormones (chemical messengers)- secreted
by neurosecretory cells or endocrine cells that travel in
body fluids to target cells & bind to specific receptors
eliciting response via ductless glands
• antagonistic hormones function in homeostasis
• pheromones – communication signals between
different individuals of same species
• local regulators (neurotransmitters, growth factors,
prostaglandins) affect target cells in immediate vicinity
of secretion
Hormone binding
• Steroid hormones – enter target cells & bind
to specific protein receptors forming
complexes that enter nucleus & bind to
acceptor proteins on a chromosome initiating
transcription
• Nonsteroid hormones – bind to specific
receptors on membrane triggering a
cascade of metabolic reactions within cells
using messengers like cAMP & IP3 (inositol
triphosphate)
Invertebrate control systems
• Using endocrine/nervous integration
• Arthropods have well developed endocrine
systems
Vertebrate control systems
• hypothalamus & pituitary gland integration
• neurosecretory cells of hypothalamus integrate
endocrine & neural function by influencing pituitary
• anterior pituitary produces several tropic hormones
that act on other endocrine glands under direction
from hypothalamus – produces TSH, FSH, LH, GHstimulates growth factor production, prolactin (PRL) –
diverse effects, ACTH – affects on adrenal cortex,
MSH – skin pigmentation, endorphins – natural
opiates
• posterior pituitary – stores/releases 2 peptide
hormones; repository for oxytocin & ADH –
enhances water reabsorption
Vertebrate endocrine system
• regulates growth, reproduction, & development &
coordinates hormones
• thyroid – stimulates metabolism & influences
development & maturation in vertebrates
-secretes calcitonin – lowers blood Ca+ levels
• parathyroid – secretes PTH & raises blood Ca+ levels
• pancreas – secretes insulin & glucagon
* increase in blood glucose levels stimulates insulin release
*promotes glycogen storage in liver
*stimulates protein synthesis & fat storage
Type I diabetes – lack insulin
Type II diabetes – loss of responsiveness of target cells to insulin
• adrenal glands:
medulla – releases epinephrine or norepinephrine;
“fight or flight” response
cortex – releases corticosteroids including sex
hormones, glucocorticoids, & mineralocorticoids
• gonads – produce varying androgens, estrogens, &
progestins
• pineal gland – secretes melotonin – influences skin
pigmentation, biological rhythms & reproduction
• thymus – secretes thymosin
Endocrine/Nervous
• structurally, functionally, & chemically related
• maintain homeostasis, development, &
reproduction
• some endocrine glands have evolved from nervous
tissue
• hormones such as epinephrine – used as signals
for both systems
Chapter 46
Animal Reproduction
Asexual
• producing offspring whose genes came
from 1 parent
• ex: fission, budding, fragmentation with
regeneration
Sexual
• requires fusion of male & female gametes to form
diploid zygote
• advantages: enhances reproductive success in
changing environments
• variations through:
a) parthenogenesis – eggs develop without fertilization
b) hermaphroditism – has both M & F reprod. Systems
c) sequential hermaphroditism – individual reverses its
sex during its lifetime protogynous – female 1st
protoandrous – male 1st
ex: wrasses – sex reversal assoc. w/age & size
Reproductive cycles
• Controlled by hormones & environmental
cues, such as:
•
•
•
•
temp. changes
rainfall
day length
seasonal lunar cycles
Sexual methods
• external fertilization – requires critical timing,
mediated by env. cues, pheromones &/or courtship
*most common in aquatic or moist env.
where zygote develops without desiccation &
heat stress
• internal fertilization – requires important behavioral
interactions between M & F, compatible copulatory
organs
*usu. fewer zygotes, but increased protection of
embryos & parental care of young
Reproductive systems
• Invert. systems range from simple gamete
production by undifferentiated cells in body
cavity to complex assemblages of M & F
gonads w/ accessory tubes & glands that
carry/protect embryos
• Vert. systems are similar, but nonmammals
usu. have a cloaca
Human reproduction
• male external genitalia – scrotum, penis
• accessory glands – add secretions to semen
• female internal – 2 ovaries, oviducts, uterus,
vagina
-external – vestibule w/ urethra & vagina
openings, labia minora & majora, clitoris
-Bartholin’s gland – secretes mucus for
lubrication
-mammary glands – (in breasts) evolved in
association w/ parental care
Sexual response
• hormones –
– androgens – (M) cause dev. of primary &
secondary sex characteristics; secretion of
androgens & sperm produced both controlled by
hypothalmic & pituitary hormones
-(F) – secreted in rhythmic fashion:
menstrual (endometrial bleeding) & estrous
(sexual receptivity) cycles
cycle: endometrium thickening in preparation for
possible implantation
Human menstrual cycle
1) menstrual flow phase – shedding endrometrium;
~5 days
2) proliferative phase – follicle produces estrogen that
stimulates thickening; ~1-2 weeks
3) secretory phase – continuing thickening, becomes
more vascularized & secretes fluid rich in glycogen;
~2 weeks
*if no implantation occurs, phase repeats
Ovarian cycle
• follicular – several follicles in ovary grow, egg
cell enlarges
• luteal – follicular tissue transformed into corpus
luteum
• gonadotropin–releasing hormone (GnRH)
from hypothalamus & FSH & LH from anterior
pituitary gland, estrogen & progesterone from
ovaries coordinate menstrual & ovarian cycles
Chapter 48
Nervous Systems
Function
• Sensory input, integration, & motor output
• CNS (central nervous system) – integrates info.
*consists of brain, spinal cord
• PNS (peripheral nervous system) –
communicate sensory & motor signals between
CNS & rest of body
*sensory neurons – carry info. from CNS to
target cells
Neurons
• transmit signals
• interneurons of CNS integrate sensory & motor
output
• supporting cells (glial cells) – support, insulate,
protect neurons
a) astrocytes – blood/brain barrier
b) oligodendrocytes – insulate w/myelin
sheath (Schwann cells in PNS)
Synaptic terminals
• at ends of axons; release neurotransmitters –
molecules released into synapses thereby relaying
neural signals to dendrites or cell bodies of other
neurons or effectors
• impulses – action potentials (electrical signals
transmitted along neuronal membranes)
• potential is unequal due to unequal distribution of
ions (K+ or Na+) across plasma membrane
• stimulus changes permeability to ions & either
depolarizes or hyperpolarizes membrane;
magnitude proportional to stimulus strength
• impulse is rapid, transient depolarization of neuron’s
membrane
• synapses conduct signals from axon of presynaptic cell to
dendrite or cell body of postsynaptic cell
• electric synapses directly pass an action potential between 2
neurons by gap junctions
• depolarizaton stimulates fusion of synaptic vesicles with
presynaptic membrane & release of neurotransmitter
molecules into synaptic cleft
• neurotransmitters bind to receptor proteins assoc. w/particular
ion channels or postsynaptic membrane
• Ach (acetylcholine) is common in verts. & inverts.
(also dopamine, serotonin, epinephrine, norepinephrine),
several AA’s, endorphins, nitric oxide (signal othe cells)
PNS
• Sensory – somatic
(afferent) – visceral
• Motor –
(efferent)
-somatic (voluntary) – signals skeletal
muscles
-autonomic (involuntary) – regulates smooth &
cardiac muscles
-sympathetic
-parasympathetic
*usu. antagonistic in effect on target organs