comp phys exam 3

difference between nervous signals and endocrine signals

• nervous= fast and targeted

• endocrine= slow and broadcast

why is the endocrine system slow? broadcast?

• hormone released → circulate to target tissues → reach necessary concentrations → elicit a response which takes time (seconds to hours)

• carried to virtually all cells in the body

hormone definition

a chemical substance produced and released by endocrine cells or neurons that regulates the activities of other cells and is transmitted through a circulatory system

what are some of the things that hormones do?

• can travel to distant targets

• permit widespread responses

• tend to signal slowly over long time periods

• effective at very low concentrations

• bind non covalently to receptor proteins

two types of endocrine cells

nonneural or neurosecretory

nonneural

• doesn’t receive information from a neuron

• stimulated to secrete their homes by other hormones

• express receptor proteins for the hormones that control them

what does a neuron do?

• releases a neurotransmitter molecules that act on receptor molecules of the postsynaptic cell

neurosecretory

• a neuron that secretes hormones into the blood stream

neuron vs neurosecretory?

*

paracrine definition

autocrine definition

• binds to receptors on cells in the neighborhood of the cell that released it, exerting a regulatory effect on those cells

• after being secreted by a cell, diffuses in the surrounding extracellular fluid to bind to receptors on that same cell and affect its function

difference paracrine vs autocrine

affects neighborhood vs affects cell itself

3 classes of hormones

1. steriod hormones

2. peptide hormones

3. amine hormones

steroid hormones

• synthesized from cholesterol, lipid soluble

• ex testosterone

peptide hormones

• made from chains of amino acids, water soluble

• ex insulin

amine hormones

• modified amino acids, can be lipid or water soluble

• ex melatonin (lipid soluble), norepinephrine (water soluble)

how do hormones work?

by binding to receptors

• to respond to a hormone a cell needs to be an appropriate receptor molecule

• cells express different assemblages of receptors

• the sensitivity of a cell to a hormone depends on the type and number of receptors it expresses

• sensitivity also depends on the concentration of a circulating hormone

• the same signal can have different meanings depending on the receiver

5 functional types of protein + which is important for signaling?

• channel

• transporter

• structural

• enzyme

• receptor

receptor

what do signaling molecules bind to?

receptors on the cell

what is a ligand?

a molecule that binds specifically to a receptor

where does ligand binding occur?

at specific receptor site(s)

what does binding cause?

change in the molecule conformation of the receptor protein → iniating further response by the cell

4 types of receptors

1. ligand gates channels

2. g protein coupled receptors

3. enzyme enzyme linked receptors

4. intracellular receptors

g protein coupled receptors

• binding of ligand to g protein coupled receptor activates a separate g protein

• g protein activates an enzyme

• enzyme initiates a intracellular second messenger system

enzyme/enzyme linked receptors

• cell membrane proteins that either are enzymes themselves or that interact directly with enzyme proteins when activated

• activated protein initiates an intracellular second messenger

intracellular receptors

• small signaling molecules dissolve in the lipid bilayer of the cell membrane and diffuse through to the cell interior

• receptors for these molecules are inside the cell

• hormone receptor complex acts as a transcription factor (targeting DNA and altering gene expression)

• turning transcription on and off influences the synthesis of proteins which then carry out the cells physiological responses

what is the main mechanism for steroids?

intracellular receptors

protein kinases and signal amplification *

where is endocrine control iniated? executed?

• hypothalamus

• pituitary gland

what does the pituitary gland consist of?

anterior pituitary and posterior pituitary

anterior pituitary-

posterior pituitary-

• control of nonneural endocrine portion

• control of neuroendocrine portion

what is adh? (an example of and what does it do?)

• an example of hormone regulated homeostasis by the posterior pituitary gland

• antidiuretic hormone, also known as vasopressin, stimulates the reabsorption of water in the kidneys

how does hormone regulated homeostasis by the posterior pituitary gland work for adh?

• adh works by stimulating the incorporation of specific aquaporin molecules into the wall of the collection duct

• adh binds to a receptor, initiates a second messenger system (PKA), which stimulates storage vesicles with AQP to use with membrane

• water follows its osmotic gradient out of the collecting duct and into blood

what does adh do?

increase the number of aquaporin molecules in apical cell membranes as a ratio of number of number in intracellular membranes & increases permeability to water

how does the anterior pituitary gland work?

neurosecretory cells in the hypothalamus secrete hormones that stimulate/inhibit the non neural endocrine cells in the anterior pituitary

what does the anterior pituitary gland do? what are some examples of what it impacts?

• targeting and magnifying responses throughout different situations

• metabolism, growth, stress response, sex hormone production and secretion, sperm production in males, skin darkening in amphibians, milk production, more

what is the hypothalamus-pituitary- adrenal cortex (HPA) axis?

has sophisticated modulation and is very important in the stress response

• allows for sophisticated regulation, coordination, and amplification of response

what is an axis in hormones?

when one endocrine gland acts on another in sequence

what are the two pathways stress can work through?

sympathetic nervous system and HPA axis

stress and sympathetic nervous system

• activation of the sympathetic nervous system by stress causes →

• secretion of norepinephrine and epinephrine creating physiological impacts

physiological impacts of secretion of norepinephrine and epinephrine

• increased heart rate

• increased ventilation

• increased vasoconstriction of specific areas (such as skin)

• decreased digestion

• increased glucagon

• increased fat catabolism

• decreased insulin

• glucose released from muscle and liver

which of the physiological impacts of secretion of norepinephrine and epinephrine are also caused by the HPA axis?

• increased fat catabolism

• decreased insulin

• glucose released from muscle and liver

stress and HPA axis

• stress cue forces hypothalamus to activate →

• secretion of CRH and vasopression, then activating →

• ACTH in the anterior pituitary, then causing →

• adrenal cortex to create glucocorticoids

what do glucocorticoids do?

• enhance some early effects in nervous system

• produces a suite of responses that are largely related to creating energy that can be used to fight the stress response (downregulates processes we don’t need during stress response")

examples of downregulation by glucocorticoids

• instead of catabolizing muscle and bones, that energy is used to make proteins which can → form glucose for energy, fuel muscle contraction/movement to get away from stress, etc

how is glucose regulated in vertebrates?

inslun and glucagon

insulin (where is it produced? why is it secreted? what does it increase? what does it synthesize?)

• produced in the beta cells of pancreatic islets of langerhands

• secreted in response to high blood glucose levels and/or high blood amino acid levels

• increases glucose uptake from the blood into tissues

• promotes synthesis of glycogen via glycogenesis and triglyceride via lipogenesis

glucagon (where is it produced? why is it secreted? what does it increase? what does it synthesize?)

• produced in the alpha cells of pancreatic islets of lagerhands

• secreted in response to low blood glucose

• increased glucose levels in the blood

• breaks down glycogen via glycogenolysis and formation of glucose from noncarbohydrate sources via gluconeogenesis

what are blood glucose levels like after eating a high carb meal? what are the impacts of this?

• high

• insulin is released to take some of that glucose and put it in storage → as glucose is removed from the blood there is less need for high levels of insulin, so insulin levels drop → blood glucose levels are high, go no need to increase blood glucose levels, levels of glucagon are low

what are blood amino acid levels like after eating a high protein meal? what are the impacts of this?

• high

• blood glucose levels don’t spike since no carbs → insulin is released to put some of those amino acids into storage in the tissues → increase in insulin also takes glucose out of the blood → so we increase glucagon levels to replace the glucose taken out of the blood and maintain constant blood glucose levels

what do invertebrates rely on for endocrine regulation? why?

• neurosecretory cells

• they use hormones the same way as vertebrates (to regulate important processes like water balance, urine production, stress response), but most lack specific endocrine organs and neurosecretory cells secrete hormones into the blood/hemolyph that travel to target cell

exceptions to general invertebrate endocrine regulation?

• insects

• crustaceans

• octopus

what is controlled by hormones in insects?

• insect metamorphosis from larva → pupa → adult

• specifically the timing of molting and what phase insects molt into

control of metamorphosis by hormones

• iniated by the secretion of PTTH into the blood by the corpus allatum →

• stimulates the secretion of ecdysone, the molting hormone in the prothoracic gland

what does the larva molting into a larva or pupa or adult depend on?

• the levels of the juvenile hormone that is produced in the corpus allatum

• high JH= stay at larva

low JH= become pupa or adult

molting

getting rid of outer exoskeleton

ecdysone vs juvenile hormone

• only refers to molting and when it is time to grow

• determines need for cells to generate proteins and cells for growth

what are the three main endocrine glands/organs in crustaceans?

x organ, y organs, & mandibular

x-organ-sinus gland complex (XOSG) or just X organ

• made up of neurosecretory cells that are released at the sinus gland

• releases 3 main hormones: crustacean hyperglycemic hormone (CHH), molt inhibiting hormone (MIH), gonad inhibitng hormone (GIH)

y organs

produce ecdysteroids for molting

mandibular

produce methyl farnesoate to advance development (similar to JH)

why are crustacean’s endocrine control weird? why do they molt into adulthood?

• their endocrine system inhibits things rather than promoting them like most species

• combative animals who need hard shells

what does the endocrine system program in octopus?

death

optics gland in octopus

functions similarly to the pituitary glands in vertebrates

how does programmed death work in octopus?

• after reproduction, otic gland shifts hormonal output to produce 7-DHC, pregnane steroids, and maternal cholestanoids trigger a transition in reproductive state which causes them to frenzy and become very “helicopter parent”

• this triggers a cessation in feeding, and affects insulin signaling to promote tissue breakdown

• death then occurs due to starvation even when food is available

what happens when the optics gland is removed?

• octupus is able to live happy healthy life

what are the challenges in reproduction?

• when to reproduce (timing and environmental cues)

• how to reproduce (reproductive strategies)

• how much to invest in offspring

• how to deal with competition

what determines the timing of reproduction? what does reproduction require?

• reproduction is energetically expensive

• requires the optimum environment for finding and allocating resources

what two things regulate reproductive state (timing of reproduction)?

environmental cues and endocrine control

how is regulation of reproductive state by reproductive cues and endocrine control happen in mammals? how does this work?

• the hypothalamus-pituitary-gonadal axis

• gondadotropin releasing hormone (GnRH) is secreted by the hypothalamus which stimulates the anterior pituitary to secrete luteinizing hormone (LH) and follicle stimulating hormone (FSH)

what do many animals rely on to initiate their reproductive cycle?

environmental cues

what is typically the reproductive season and why?

• spring-summer

• high amounts of food availability, favorable temperatures, and sufficient water

what else in reproduction is controlled by the environment?

sex determination

sequential hermaphrodites definition and example

• organisms that start out life as one sex and can later change to a different sex

• wrasse (fish)- start of as females and later change to males

what triggers sex change in wrasse? how dos this work?

1. changes in social hierarchy

2. a male controls a group of females, when that male is removed, the largest female changes sex

2. this is due to a shift in hormone production → decrease in estrogen and rise in testosterone to undergo behavioral, morphological and anatomical changes

how can the environment dictate the sex of an animal before it is born? example?

1. incubation temperature

2. at intermediate temperature of 28.5C, turtles have a mixed brood of males and females. at warmer temperatures (>30C) all. hatchlings are female. at cooler temperatures (<25C) all hatchlings are males.

what are the two types of fertilization?

internal or external

internal fertilization deifinition + what kinds of animals use this strategy-

external fertilization-

• fertilization occurs within the reproductivet ract, common with majority of terrestrial animals and some aquatic fish and mammals

• gametes are ejected into the environment, common in aquatic environments especially with invertebrates

semelparous definition + examples

individuals are physiologically capable of only one bout of reproduction in their lives, they are often programmed to die after

• nereid worm

• octopus

• mayfly

• sockeye salmon

iteroparous definition + examples

individuals are physiologically capable of two or more separate periods of reproductive activity during their lives. most common across the animal kingdom.

• sharks

• birds

• humans

• mussels

what must animals decide with respect to investment in offspring?

how much resources and energy they allocate (either nutritional or quality resources) for the offspring during embryonic development or in parental care afterwards

K species traits

• often from stable environments in which populations are density dependent

• individuals tend to be large in size

• produce fewer expensive offspring

• late maturity, long life expectancy

r species traits

• often from unstable environments in which populations are density independent

• individuals tend to be smaller in size

• produce many inexpensive offspring

• early maturity, short life expectancy

rock paper scissors effect

*

females mating polymorphism in Uta lizards (yellow throated females vs orange throated females reproductive strategies)

yellow throated

1. lay fewer, larger eggs

1. tend to have higher reproductive success when population density is high and or when predators abound

1. larger hatchlings have higher short term and long term survival rates, and these advantages are magnified in times of scarcity

orange throated

2. typically produce large clutches of many small eggs

2. more successful at lower population densities, where competition for food is less fierce and less selection pressure from predation occurs

how do female placental mammals ovulate? what types of cycle to they exibit?

• periodically

• menstrual or estrous cycle

how does the menstrual/estrous cycle work?

• FSH promotes follicle development and stimulates the production of estrogen

• high levels of estrogen produce an LH surge

• LH surge causes ovulation (the release of mature eggs from ovary) where it goes to the fallopian tube where fertilization can occur

• after ovulation, corpus luteum forms & produces progesterone, which prepares the uterine lining for pregnancy

how does egg production work in female placental mammals?

females are born with all of the eggs they will have in their life, they just go through different stages

when do male mammals produce sperm? how does this work?

1. male mammals produce sperm continuously during the reproductive season

2. LH acts on Leydig cells to produce testosterone (which is responsible for spermatogenesis)

2. FSH acts on sertoli cells, which support sperm development

neuron definition

• cells that transmit information in the form If electrical signals

• specifically adapted to generate an electrical signal, most often in the form of a brief, self-propegating impulse called an action potential

how does a signal in a neuron travel?

• they are transmitted rapidly over long distances

• a signal travels along the axon where it causes the release of a neurotransmitter at the synapse

neurotransmitter

a molecule that is used as a chemical in synaptic transmission

neuron parts (in order of how the electrical signal moves down the neuron)

• dendrite

• cell body/soma

• axon

• presynaptic terminals

• dendrite-

• cell body/soma-

• axon-

• presynaptic terminals-

• receives input

• integration

• conduction

• output

2 categories of neurons and associated cells that make up our nervous system

• peripheral nervous system (PNS)

• central nervous system (CNS)

afferent neurons-

efferent neurons-

interneurons-

• relay sensory signals from the periphery (outside) into the CNS

• relay command signals from the CNS to the periphery

• within the CNS and process the signals

how are neurons organized?

into functional circuits in nervous systems

what kind of gradients generate electrical signals?

electrochemical gradients (moving from high to low concentration)

membrane potential definition

the difference in electrical charge between the inside and outside of the cell

what concentration gradient charge do neurons have? what does this mean? what is this state called?

1. negative concentration gradient most of the time

2. more positively charged ions outside the cell than inside

3. resting membrane potential

what is the negative charge inside the cell maintained by?

selective permeability of ions