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What is cell-to-cell communication?
Cell-to-cell communication is the process by which cells send and receive signals to coordinate functions in the body.
What are the different ways cells communicate?
Cells communicate through direct contact, local signaling (paracrine signaling), and long-distance signaling (hormonal communication).
What are hormones?
Hormones are chemical messengers that are transported through the bloodstream to stimulate physiological responses in target cells.
How do hormones travel through the body?
Hormones travel through the bloodstream to reach their target cells, which must have specific receptors to respond to them.
Why do hormones only affect certain cells?
Hormones only affect certain cells because target cells must have specific receptors that bind to the hormone and trigger a response.
What type of signaling do hormones use?
Hormones use long-distance signaling, where the chemical message is broadcasted throughout the body via the bloodstream.
What is paracrine signaling?
Paracrine signaling, also known as "local hormone" signaling, occurs when a cell secretes chemical signals to influence nearby cells over short distances.
How does paracrine signaling differ from hormonal signaling?
Paracrine signaling affects nearby cells through diffusion without needing the bloodstream, while hormonal signaling travels through the bloodstream to reach distant target cells.
What is an example of paracrine signaling?
An example of paracrine signaling is the release of growth factors, which stimulate nearby cells to grow and divide.
Why doesn’t paracrine signaling require the bloodstream?
Paracrine signaling does not require the bloodstream because the chemical signals diffuse over short distances to reach nearby cells.
What do target cells need to respond to a hormone?
Target cells need specific receptors to bind to a hormone and initiate a physiological response.
What type of communication in the body involves very specific signaling over a short distance?
Communication in the body that involves very specific signaling over a short distance occurs through neurotransmitters released from neurons into the synaptic cleft.
What is contact-dependent signaling?
Contact-dependent signaling is a type of cell communication that requires direct physical contact between cells, involving membrane-bound signal molecules.
What structures allow direct cytoplasm-to-cytoplasm communication between cells?
Gap junctions allow direct cytoplasm-to-cytoplasm in contact-dependent communication between cells, enabling ions and small molecules to pass between adjacent cells.
What type of communication is seen in antigen presentation, development, and the immune system?
Contact-dependent signaling is seen in antigen presentation, development, and the immune system, where membrane-bound signal molecules facilitate direct cell-to-cell interaction.
What do exocrine glands secrete their products through?
Exocrine glands secrete their products through ducts.
Where do exocrine glands release their secretions?
Exocrine glands release their secretions onto epithelial surfaces.
What are some examples of exocrine glands?
Examples of exocrine glands include sweat glands in the skin and glands in the digestive tract.
What type of effects do exocrine glands have?
Exocrine glands have extracellular effects, meaning their secretions work outside of the cells.
What is an example of an extracellular effect of exocrine glands?
An example of an extracellular effect is the digestion of food by enzymes secreted into the digestive tract or the cooling effect of sweat on the skin.
What are mixed glands?
Mixed glands are glands that have both exocrine and endocrine functions.
What are some examples of mixed glands?
Examples of mixed glands include the liver and pancreas.
What is the exocrine-to-endocrine ratio of the pancreas?
The pancreas is 99% exocrine and 1% endocrine.
What is a characteristic of endocrine glands that differentiates them from exocrine glands?
Endocrine glands do not have ducts and lose their connection to the surface, while exocrine glands have ducts that transport their secretions.
Why do endocrine glands have a high density of capillaries?
Endocrine glands have a high density of capillaries to facilitate the efficient uptake of hormones into the bloodstream.
What is the function of fenestrated capillaries in endocrine glands?
Fenestrated capillaries have small pores that allow hormones to pass through easily and enter the bloodstream for distribution to target cells.
How do endocrine glands release their secretions?
Endocrine glands release their secretions directly into the bloodstream, which is why they are referred to as having "internal secretions."
What happens when hormones bind to target cells?
When hormones bind to target cells, they trigger intracellular effects, such as altering metabolism and regulating physiological processes.
Why can lipid-based (steroid) hormones easily pass through fenestrated capillaries?
Lipid-based steroid hormones can easily pass through fenestrated capillaries because they are nonpolar and can diffuse through cell membranes and capillary pores without resistance.
What are neuroendocrine cells?
Neuroendocrine cells are hybrid cells that share characteristics of both neurons and endocrine cells, allowing them to receive neural signals and release hormones into the bloodstream.
What are examples of neuroendocrine cells in the body?
Examples of neuroendocrine cells include those found in the adrenal medulla, which release epinephrine and norepinephrine in response to stress, and the hypothalamus, which regulates various physiological processes through hormone secretion.
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What is the primary function of the endocrine system?
The primary function of the endocrine system is to regulate various physiological processes in the body through the secretion of hormones.
What structures are included in the endocrine system?
The endocrine system includes glands, tissues, and cells that produce and release hormones into the bloodstream.
What are the three chemical classes of hormones?
The three chemical classes of hormones are steroids, monoamines, and peptides.
What are steroids made from, and where are they produced?
Steroids are made from cholesterol and are produced in the gonads and adrenal glands.
How do steroids interact with the plasma membrane?
Steroids are small hydrophobic molecules, meaning they can pass straight through the plasma membrane.
What are examples of sex steroids?
Examples of sex steroids include progesterone and testosterone.
What are examples of corticosteroids?
Examples of corticosteroids include cortisol and aldosterone.
Why are steroids considered hydrophobic?
Steroids are lipid-based, which makes them hydrophobic, meaning they do not mix with water.
How are monoamines chemically modified from amino acids?
Monoamines are created by removing a carboxyl group from amino acids.
What are some examples of monoamines?
Examples of monoamines include dopamine, epinephrine, norepinephrine (from the adrenal medulla), melatonin, and thyroid hormone (TH).
Which monoamines are hydrophilic, and which are hydrophobic?
All monoamines are hydrophilic except for thyroid hormone (TH), which is hydrophobic.
What are peptides in hormone chemistry?
Peptides are hormones composed of 3 to over 200 amino acids.
What are some examples of peptide hormones?
Examples of peptide hormones include the releasing and inhibiting hormones of the hypothalamus, most pituitary hormones, and insulin.
Are peptide hormones hydrophilic or hydrophobic?
Peptide hormones are hydrophilic.
What is the difference between steroids and other hormones in terms of their functional group?
Steroids differ from other hormones based on the functional group added to the steroid backbone, which consists of four rings.
Where are steroids primarily synthesized in the body?
Steroids are primarily synthesized in the ovaries, testes, and adrenal glands, specifically in the adrenal cortex.
What organelle is involved in the synthesis of steroids?
The smooth endoplasmic reticulum (Smooth ER) is involved in the synthesis of steroids.
What enzymes are essential for steroid production?
Enzymes in the body that are essential for producing steroids include those found in the Smooth ER, which help facilitate the process.
What are monoamines and how are they related to aromatic amino acids?
Monoamines are hormones derived from aromatic amino acids, which undergo decarboxylation to remove the carboxyl group from the amino acid.
What role do decarboxylase enzymes play in the synthesis of monoamines?
Decarboxylase enzymes, which require Vitamin B6, play a crucial role in removing the carboxyl end of the aromatic amino acid, turning it into a monoamine.
How is tryptophan modified to produce melatonin?
Tryptophan is modified into melatonin through a series of biochemical steps, primarily through decarboxylation and subsequent enzymatic reactions.
How is tyrosine involved in the production of thyroid hormones (TH)?
Tyrosine is a precursor for thyroid hormone (TH), which are made up of 2 tyrosine molecules.
How are peptides produced in the body?
Peptides are produced like other proteins through transcription of DNA to mRNA, followed by translation on the rough endoplasmic reticulum, and then folding and modification into their active forms.
What role does the enzyme play in thyroid hormone production?
The enzyme adds iodine to the tyrosines of thyroglobulin (Tg), which is essential for producing thyroid hormones.
How does thyroglobulin (Tg) contribute to thyroid hormone production?
Thyroglobulin (Tg) folds, and the tyrosines within it link together to form the precursors needed for thyroid hormone production.
What happens to thyroglobulin (Tg) after it folds and the tyrosines link together?
Lysosomes hydrolyze thyroglobulin (Tg), breaking it down to release the thyroid hormones.
Why do thyroid hormones need to be transported by the bloodstream?
Thyroid hormones are hydrophobic, so they need to be carried by the bloodstream to reach their target cells.
How do steroids and thyroid hormones (TH) influence gene activation?
Steroids and thyroid hormones are hydrophobic, meaning they diffuse through the membrane to activate gene expression.
What is the exception to the general mechanism of steroid and thyroid hormone transport?
The exception is thyroid hormone (TH), which is transported via a channel rather than diffusing through the membrane like other hydrophobic molecules.
What role does the nuclear receptor play in gene activation?
The nuclear receptor binds with the steroid or thyroid hormone and causes a change in gene expression through transcription and translation processes.
What is the function of a cytoplasmic receptor?
A cytoplasmic receptor binds to hormones or steroids and helps in the regulation of gene expression, typically by acting as a precursor to the nuclear receptor pathway.
What effect do glucocorticoids have in terms of gene activation or inactivation?
Glucocorticoids can either activate or inactivate target genes, depending on the specific regulatory mechanisms and receptors involved.
What is the concept of time lag in hormone-induced gene activation?
The time lag refers to the delay between the initial activation of a hormone and the observable effects on gene expression or cellular processes, as transcription and translation take time.
What is a coordinated unit in the context of genetics and expression levels?
A coordinated unit refers to a group of genes that are regulated and expressed together in response to certain factors, such as hormones or environmental stimuli.
In this context, it indicates that specific genes are working in tandem to influence biological processes, like cortisol concentration.
How are genes with hepatic expression levels correlated with cortisol concentration?
Genes with hepatic expression levels are correlated with cortisol concentration because they are involved in regulating processes in the liver that respond to cortisol.
This means that the expression of these genes in the liver is influenced by cortisol levels, highlighting the relationship between gene activity and hormone regulation.
What are some examples of activation methods used in cell signaling?
Peptides and catecholamines are examples of activation methods.
These molecules are hydrophilic and cannot pass directly through the cell membrane.
How do second messenger systems work in cell signaling?
Second messenger systems work by triggering a cascade of events inside the cell.
For example, ATP is converted to cAMP through the action of adenylyl cyclase, and PIP2 is split into IP3 and DAG, which then activate or inactivate enzymes in the cell.
What is the response time of second messenger systems?
The response time of second messenger systems is rapid, allowing cells to quickly react to signals.
What role do molecular switches play in cell signaling?
Molecular switches, such as GTPases (G-proteins), play a key role in activating or deactivating cellular processes in response to signaling.
How do protein kinases influence cellular activity?
Protein kinases add phosphate groups onto proteins, causing the proteins to change shape, which in turn affects the proteins' function.
Why are the effects of second messenger systems short-lived?
The effects of second messenger systems are short-lived because they are typically degraded more quickly, limiting their duration of action.
What is the function of IP3 in the cell?
IP3 opens calcium channels, allowing Ca2+ to enter the cytoplasm and influence various cellular processes.
How does Ca2+ affect cell metabolism?
Ca2+ binds to enzymes, leading to changes in cell metabolism.
What is an example of a calcium receptor in the cytoplasm?
An example of a calcium receptor in the cytoplasm is calmodulin.
How does Ca2+ influence kinases?
Ca2+ binds to calmodulin, which can activate kinases and influence cellular activity.
What effect does Ca2+ have on membrane channels?
Ca2+ binds to membrane channels, which can change solute permeability and alter membrane potential.
What is the role of DAG in cellular signaling?
DAG activates protein kinase C, which phosphorylates enzymes to regulate cellular metabolism.
How does protein kinase C affect metabolism?
Protein kinase C can either activate or suppress metabolism by phosphorylating enzymes.
In what biological process is IP3 and DAG signaling seen?
IP3 and DAG signaling are seen in processes such as thyroid hormone (TH) release from follicular cells.
What modulates the structure of calmodulin?
Calmodulin is modulated by the presence or absence of Ca2+.
What is the structure of calmodulin?
Calmodulin has two globular ends connected by a long α helix.
How many Ca2+-binding sites does each globular end of calmodulin have?
Each globular end of calmodulin has two Ca2+-binding sites.
What happens when Ca2+ binds to calmodulin?
When Ca2+ binds to calmodulin, it activates calmodulin, which in turn activates kinases.
What does CaM-kinase stand for?
CaM-kinase stands for Ca2+/calmodulin-dependent protein kinase.
What is the role of CaM-kinases in the mammalian brain?
CaM-kinases are involved in learning and memory in the mammalian brain.
What physiological process involves CaM-kinases besides learning and memory?
CaM-kinases are involved in smooth muscle contraction.
What hormone is released by the posterior pituitary during childbirth?
Oxytocin is released by the posterior pituitary during childbirth.
Where does oxytocin bind to initiate uterine contractions?
Oxytocin binds to receptors on the smooth muscle of the uterus.
What enzyme is activated after oxytocin binds to its receptor?
Phospholipase releases IP3, which plays a key role in the signaling pathway.
How does IP3 contribute to uterine contractions?
IP3 diffuses through the cell and opens channels on the sarcoplasmic reticulum, allowing Ca2+ to enter the cytosol.
What happens when Ca2+ enters the cytosol?
Ca2+ opens additional Ca2+ membrane channels associated with the plasma membrane, leading to even more Ca2+ entering the cytosol.
What role does calmodulin play in uterine contractions?
Ca2+ binds to calmodulin, which wraps around myosin light chain kinase (MLCK) to activate it.
How does MLCK contribute to uterine contractions?
MLCK phosphorylates myosin heads, enabling cross-bridge formation and leading to uterine contractions.
What is amplification of a hormone signal?
Amplification of a hormone signal occurs when one hormone molecule triggers the production of many products, often through enzyme amplification.
How does enzyme amplification contribute to hormone signal amplification?
Enzyme amplification allows a single hormone molecule to activate a cascade of reactions, leading to the production of a large number of final products.
What is an example of hormone signal amplification?
An example of hormone signal amplification is when one glucagon molecule triggers the production of 1,000 cAMP molecules, each cAMP activates 1,000 kinases, each kinase activates 1,000 other enzymes, and each enzyme produces 1,000 products, ultimately resulting in 1 billion products.
Why are hormones effective in small quantities?
Hormones are effective in small quantities because of signal amplification, where one hormone molecule sets off a chain reaction that leads to the production of a massive number of final products.
What is hormone modulation?
Hormone modulation refers to the process by which the body adjusts the sensitivity of target cells to hormones by increasing or decreasing the number of hormone receptors.
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