PSL-Week 3 Flashcards
What is definition of homeostasis?
the process of maintaining constant internal environement despite changing conditions
What is the difference between positive and negative feedback?
negative feedback works for homeostasis by turning off the stimuli when the system has returned to within the normal range but positive feedback is different because it acts for change, it reinforces effect of stimuli and can only be turned off by outside factors
What is an example of negative feedback in our endocrine system which involves the hypothalamus?
cortisol secretion, where when there is enough cortisol in body, cortisol itself will start suppressing the upstream processes like action of hypothalamus secreting CRH and stop release of cortisol so it doesn;t deviate from normal
What is an example of positive feedback loop?
even though it is rare feedback, it occurs during childbirth when baby drops lower in uterus, that will initiate labour and that will stimulate oxytocin which respond by causing uterine contractions and those contractions will push baby even lower in uterus which will cause cervical stretch and that process keeps going until baby is delivered which is the external force taht will stop this positive feedback lopp
Imagine a hormone is released in response to low blood pressure and acts to reduce blood pressure, what is this example of?
positive feedback because the response is reinforcing the change of low blood pressure which is moving away from homeostasis so it is reinforcing new change which means it is positive feedback
Maintaining homeostasis isn’t possible without intercellular communication, what are the two types of communications that we have in our system?
local and long distance
What are three ways for local control type of intercellular communication
through gap junctions, by contact dependant where membrane protein bind membrane protein, and by autocrine where molecules move through interstitial fluid
Why are neuroendocrine/neurohormones distinct from neurotransmitters and hormones?
neuroendocrines are chemicals secreted by neurons but are secreted into bloodstream and act on its target as a hormone
What are the two types of long distance communication in our body and how do they differ?
the two types are our endocrine system and nervous system:
1- endocrine system is slower acting than nervous system since its hormones travel through bloodstream
2- endocrine system secrete hormones while nervous sytem secrete neurotransmitters which are chemicals
Differences between simple and complex reflexes?
simple reflezes are mediated either by nervous or endocrine system while complex are mediated by both and go through several integrating systems
What is difference between local change and systemic change?
in local change the repsonse due to stimulus is mediated by local cells close to area or repsonse
in systemic change the repsonse is mediated by cells that are further from teh area of stimuli
Stimuli has to be sensed to ilicit a response, so what sense these stimuli?
sensors in opur body can vary from being specialized cells or structures that can convert stimuli into electrical signal to being a cell membrane receptor or intracellular receptor
All are reflex pathways the same, where there is a signal, then interegating center, and then a response?
not quite, reflex systems can be as simple as having only an intergating system to ilicit teh reponse, but they can also become more complicated where there could be intergating center involved to release a hormone for example, but then that hormone will act on another cell to have it release another substance and then that susbstance, hormone for example, will go to target and then have a response
so reflex pathways can vary
What are some characteristics of hormones?
can be made in different places in body
made by cells in specific endocrine glands/tissues
transported using the blood
bind specific targets
can act on multiple tissues
alter activity of target cell
terminated by negative feedback
help with maintaining homeostasis or percipetate a change
What are the two classes of hormones?
Hydrophobic/lipophilic
Hydrophilic/lipophobic
What are characteristics of hydrophilic hormone?
get released by exocytosis, can travel freely in blood, cannot cross membrane freely, can be made in advance and stored
Whata re examples of hydrophilic hormones
peptide hormones, protein hormones, and catecholamines
What are chractersitics of hydrophbic hormones?
are released by diffusion from the cell cytoseol, can cross plasma membrane without help, cannot be made in advance and stored as they can cross freely, boudn by carrier proteins in blood to be get transported as it si hydrophobic
What are examples of hydrophobic hormones
steroid hormones and thyrpid hormones
What are the three main types of hormones based on tehir biochemical properties?
peptide/protein- made from 3 or more amino acids
steroid- made from cortisol
amine- made from single amino acid type
What are some of the distinct features of peptie hormones?
they ahve short life span in plasma and can bind membrane receptoires
How are the three types of hormones different?
steroid are different from amine and peptide because they are made form cortisol while amine and peptide are made from amino acids, steroid are also trasnported using transport proteins while amine and peptide can mix easily with blood plasma
What is difference between preporhormone, prohormone, and homrone of the peptide hormones?
preprohormone is the initial peptide sewuence that is sequenced and released by ribosome
prohormone is the preprohormone after it loses teh signal sequence which happens when preprohormone makes its way to ER as that is purpose of the signal sequence
hormone is the final product that gets released and the type of hormone that gets released from that prohormone depends on protolytic processing enzymes
What is distinct features of steroid hormones?
they are all made from same molecules, the cholestrol, so all of them have teh same backbone but end up as different hormones because of the enzymatic acivity of teh cell it is in and teh cells that make steroid hormones have large amount opf Smooth ER since that is where tehy get synthesized, and this type of hormone can act on cytosol and nucleus receptores and some plasma membrane receptores