A chemical substance produced in the body that controls and regulates the activity of certain cells or organs. Many hormones are secreted by special glands, such as thyroid hormone produced by the thyroid gland.
Gastrointestinal Hormones by Pandian M, Dept of Physiology DYPMCKOP, for MBBS...Pandian M
Classify GIT hormones
List the source and functions of different GI hormones
Explain the mechanism of action and regulation of secretion of different GI Hormones
Describe the role of GI hormones in regulation of GI functions
Explain the dysfunctions produced by alteration in secretion of GIT hormones
A chemical substance produced in the body that controls and regulates the activity of certain cells or organs. Many hormones are secreted by special glands, such as thyroid hormone produced by the thyroid gland.
Gastrointestinal Hormones by Pandian M, Dept of Physiology DYPMCKOP, for MBBS...Pandian M
Classify GIT hormones
List the source and functions of different GI hormones
Explain the mechanism of action and regulation of secretion of different GI Hormones
Describe the role of GI hormones in regulation of GI functions
Explain the dysfunctions produced by alteration in secretion of GIT hormones
Biochemistry Of Hormones
Contains All Important topics with best key points....
Made By Sanjay kumar (Student Of PharmD Faculty of Pharmacy Hamdard University)
Hormones are chemical messengers that are secreted directly into the blood, which carries them to organs and tissues of the body to exert their functions. There are many types of hormones that act on different aspects of bodily functions and processes.
Biochemistry Of Hormones
Contains All Important topics with best key points....
Made By Sanjay kumar (Student Of PharmD Faculty of Pharmacy Hamdard University)
Hormones are chemical messengers that are secreted directly into the blood, which carries them to organs and tissues of the body to exert their functions. There are many types of hormones that act on different aspects of bodily functions and processes.
g protein coupled receptors, ion channels, types of receptors, wnt signalling, cell signalling, tranduction pathway, disorders regarding the signalling
1.Receptors Link to other Enzymatic Activity.
2.Pathway of Intracellular Signal Transduction.
3.The Cyclic AMP pathway4.Cyclic GMP pathway
5.Phospholipids and Ca2+
6.The PI3-Kinase /Akt and mTOR pathways.
7.MAP Kinase Pathway.
1. INTRODUCTION
2. WHAT IS A RECEPTOR
3. HISTORY
4. CONCEPT OF CELL SIGNALLING
5. RECEPTOR SUPER FAMILIES
6. GPCRs- SIGNAL TRANSDUCTION & ITS SECOND MESSENGERS
receptor as drug target (receptor structure and signal transduction)Ravish Yadav
The all the content in this profile is completed by the teachers, students as well as other health care peoples.
thank you, all the respected peoples, for giving the information to complete this presentation.
this information is free to use by anyone.
Overview of epigenetics and its role in diseaseGarry D. Lasaga
Epigenetics is the study of heritable changes in gene expression (active versus inactive genes) that do not involve changes to the underlying DNA sequence — a change in phenotype without a change in genotype — which in turn affects how cells read the genes.
Epigenetics is the study of heritable changes in gene expression (active versus inactive genes) that do not involve changes to the underlying DNA sequence — a change in phenotype without a change in genotype — which in turn affects how cells read the genes. - [https://www.whatisepigenetics.com/fundamentals/]
Author of this presentation: The University of Western Australia
Introduction Artificial Intelligence a modern approach by Russel and Norvig 1Garry D. Lasaga
In computer science, artificial intelligence, sometimes called machine intelligence, is intelligence demonstrated by machines, in contrast to the natural intelligence displayed by humans and animals. - Wikipedia
In computer science, artificial intelligence, sometimes called machine intelligence, is intelligence demonstrated by machines, in contrast to the natural intelligence displayed by humans and animals. - Wikipedia
Artificial intelligence (AI) is an area of computer science that emphasizes the creation of intelligent machines that work and react like humans. Some of the activities computers with artificial intelligence are designed for include: Speech recognition, Learning, Planning and Problem solving - [Source: https://www.techopedia.com/definition/190/artificial-intelligence-ai]
The epithelium lining the respiratory tract from the nasal fossa through the bronchi is called the respiratory mucosa and is characterized by a pseudostratified ciliated epithelium with abundant non-ciliated cells known as goblet cells. - [Source: medcell.med.yale.edu/histology/respiratory_system_lab.php]
Structurally, the skin consists of two layers which differ in function, histological appearance and their embryological origin. The outer layer or epidermis is formed by an epithelium and is of ectodermal origin. ... The skin and its appendages together are called the integumentary system. - [Source: Blue Histology - Integumentary System]
The lymphatic system consists of organs, ducts, and nodes. It transports a watery clear fluid called LYMPH distributes immune cells and other factors throughout the body.
Gene regulation is how a cell controls which genes, out of the many genes in its genome, are "turned on" (expressed). Thanks to gene regulation, each cell type in your body has a different set of active genes – despite the fact that almost all the cells of your body contain the exact same DNA. These different patterns of gene expression cause your various cell types to have different sets of proteins, making each cell type uniquely specialized to do its job. [Source: https://www.khanacademy.org/science/biology/gene-regulation/gene-regulation-in-eukaryotes/a/overview-of-eukaryotic-gene-regulation]
The mitochondrial DNA (mtDNA) is a small circular molecule that codes for some proteins in the respiratory chain and RNA molecules involved in translation of these proteins inside mitochondria. Mitochondria have their own DNA and express their genes to produce proteins active in the electron transport chain. However, most of the proteins they need are encoded in the nucleus of the cell. They need to import most of their proteins to function.
Alterations in the DNA code, such as changing a letter, deleting a letter, inserting a letter or moving sections aroun proteins with abnormal functions.
If these abnormal functions cause the cell to grow, divide, ignore regulatory signals or assume new functions, cancers can develop
Fortunately, normal cells are good at repairing mistakes should they occur and have multiple systems for ensuring that the DNA co transmitted to its two daughter cells when it divides. Normal cells even have suicide programs if the mistakes are beyond repair, a p death, known as apoptosis. [Source: https://www.loxooncology.com/genomically-defined-cancers/genomic-alterations]
The study of nucleic acids began with the discovery of DNA, progressed to the study of genes and small fragments, and has now exploded to the field of genomics. Genomics is the study of entire genomes, including the complete set of genes, their nucleotide sequence and organization, and their interactions within a species and with other species. The advances in genomics have been made possible by DNA sequencing technology. [Source: https://opentextbc.ca/biology/chapter/10-3-genomics-and-proteomics/]
DNA cloning is the process of making multiple, identical copies of a particular piece of DNA. In a typical DNA cloning procedure, the gene or other DNA fragment of interest (perhaps a gene for a medically important human protein) is first inserted into a circular piece of DNA called a plasmid.- [https://www.khanacademy.org/science/...dna.../dna-cloning.../a/overview-dna-cloning]
DNA and RNA molecules are linear polymers built from individual units called nucleotides connected by bonds called phosphodiester linkages. DNA and RNA are used to store and pass genetic information from one generation to the next.
"The body maintains a balance of acids and bases in order to constantly maintain blood pH within a narrow range, despite the continuous generation of metabolic products. In turn, this allows the body to maintain cell enzyme systems in good operation conditions, together with the proper concentration of ionized (active) forms of various electrolytes such as Ca and Mg . This influences the speed of metabolic reactions and trans-membrane transportation systems (pharmacokinetics and pharmacodynamics)." - Luis Núñez Ochoa, Facultad de Medicina Veterinaria y Zootecnia, Unam, Mexico
Production Performance and Management Practices of Philippine Native Pigs in ...Garry D. Lasaga
Recently, there has been a proliferation of studies that deals with the major topic on the Conservation, Improvement and Profitable Utilization of the Philippine Native Pigs. One of the main reasons why there is an influx of research on native pigs is because there is a need to promote one of the government’s aim to the country, w/c is ultimately POVERTY ALLEVIATION.
African Swine Fever: Nature, Impacts and Threats to the Global Pig Industry Garry D. Lasaga
In August 2018, African Swine Fever (ASF), one of the world’s most feared swine infection made headlines as it hit for the first time ever, the world’s largest pig producer – China. This review paper summarizes the current state of knowledge and very recent updates on ASF.
Swine Production Performance Monitoring Data for 2014 - Dr. Arturo CaludGarry D. Lasaga
This is the 2014 Swine Production Performance Monitoring Data among participating commercial swine farms in the Philippines as provided by Dr. Arturo Calud.
Prix Galien International 2024 Forum ProgramLevi Shapiro
June 20, 2024, Prix Galien International and Jerusalem Ethics Forum in ROME. Detailed agenda including panels:
- ADVANCES IN CARDIOLOGY: A NEW PARADIGM IS COMING
- WOMEN’S HEALTH: FERTILITY PRESERVATION
- WHAT’S NEW IN THE TREATMENT OF INFECTIOUS,
ONCOLOGICAL AND INFLAMMATORY SKIN DISEASES?
- ARTIFICIAL INTELLIGENCE AND ETHICS
- GENE THERAPY
- BEYOND BORDERS: GLOBAL INITIATIVES FOR DEMOCRATIZING LIFE SCIENCE TECHNOLOGIES AND PROMOTING ACCESS TO HEALTHCARE
- ETHICAL CHALLENGES IN LIFE SCIENCES
- Prix Galien International Awards Ceremony
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Couples presenting to the infertility clinic- Do they really have infertility...Sujoy Dasgupta
Dr Sujoy Dasgupta presented the study on "Couples presenting to the infertility clinic- Do they really have infertility? – The unexplored stories of non-consummation" in the 13th Congress of the Asia Pacific Initiative on Reproduction (ASPIRE 2024) at Manila on 24 May, 2024.
Title: Sense of Taste
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the structure and function of taste buds.
Describe the relationship between the taste threshold and taste index of common substances.
Explain the chemical basis and signal transduction of taste perception for each type of primary taste sensation.
Recognize different abnormalities of taste perception and their causes.
Key Topics:
Significance of Taste Sensation:
Differentiation between pleasant and harmful food
Influence on behavior
Selection of food based on metabolic needs
Receptors of Taste:
Taste buds on the tongue
Influence of sense of smell, texture of food, and pain stimulation (e.g., by pepper)
Primary and Secondary Taste Sensations:
Primary taste sensations: Sweet, Sour, Salty, Bitter, Umami
Chemical basis and signal transduction mechanisms for each taste
Taste Threshold and Index:
Taste threshold values for Sweet (sucrose), Salty (NaCl), Sour (HCl), and Bitter (Quinine)
Taste index relationship: Inversely proportional to taste threshold
Taste Blindness:
Inability to taste certain substances, particularly thiourea compounds
Example: Phenylthiocarbamide
Structure and Function of Taste Buds:
Composition: Epithelial cells, Sustentacular/Supporting cells, Taste cells, Basal cells
Features: Taste pores, Taste hairs/microvilli, and Taste nerve fibers
Location of Taste Buds:
Found in papillae of the tongue (Fungiform, Circumvallate, Foliate)
Also present on the palate, tonsillar pillars, epiglottis, and proximal esophagus
Mechanism of Taste Stimulation:
Interaction of taste substances with receptors on microvilli
Signal transduction pathways for Umami, Sweet, Bitter, Sour, and Salty tastes
Taste Sensitivity and Adaptation:
Decrease in sensitivity with age
Rapid adaptation of taste sensation
Role of Saliva in Taste:
Dissolution of tastants to reach receptors
Washing away the stimulus
Taste Preferences and Aversions:
Mechanisms behind taste preference and aversion
Influence of receptors and neural pathways
Impact of Sensory Nerve Damage:
Degeneration of taste buds if the sensory nerve fiber is cut
Abnormalities of Taste Detection:
Conditions: Ageusia, Hypogeusia, Dysgeusia (parageusia)
Causes: Nerve damage, neurological disorders, infections, poor oral hygiene, adverse drug effects, deficiencies, aging, tobacco use, altered neurotransmitter levels
Neurotransmitters and Taste Threshold:
Effects of serotonin (5-HT) and norepinephrine (NE) on taste sensitivity
Supertasters:
25% of the population with heightened sensitivity to taste, especially bitterness
Increased number of fungiform papillae
Report Back from SGO 2024: What’s the Latest in Cervical Cancer?bkling
Are you curious about what’s new in cervical cancer research or unsure what the findings mean? Join Dr. Emily Ko, a gynecologic oncologist at Penn Medicine, to learn about the latest updates from the Society of Gynecologic Oncology (SGO) 2024 Annual Meeting on Women’s Cancer. Dr. Ko will discuss what the research presented at the conference means for you and answer your questions about the new developments.
Ozempic: Preoperative Management of Patients on GLP-1 Receptor Agonists Saeid Safari
Preoperative Management of Patients on GLP-1 Receptor Agonists like Ozempic and Semiglutide
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Title: Sense of Smell
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the primary categories of smells and the concept of odor blindness.
Explain the structure and location of the olfactory membrane and mucosa, including the types and roles of cells involved in olfaction.
Describe the pathway and mechanisms of olfactory signal transmission from the olfactory receptors to the brain.
Illustrate the biochemical cascade triggered by odorant binding to olfactory receptors, including the role of G-proteins and second messengers in generating an action potential.
Identify different types of olfactory disorders such as anosmia, hyposmia, hyperosmia, and dysosmia, including their potential causes.
Key Topics:
Olfactory Genes:
3% of the human genome accounts for olfactory genes.
400 genes for odorant receptors.
Olfactory Membrane:
Located in the superior part of the nasal cavity.
Medially: Folds downward along the superior septum.
Laterally: Folds over the superior turbinate and upper surface of the middle turbinate.
Total surface area: 5-10 square centimeters.
Olfactory Mucosa:
Olfactory Cells: Bipolar nerve cells derived from the CNS (100 million), with 4-25 olfactory cilia per cell.
Sustentacular Cells: Produce mucus and maintain ionic and molecular environment.
Basal Cells: Replace worn-out olfactory cells with an average lifespan of 1-2 months.
Bowman’s Gland: Secretes mucus.
Stimulation of Olfactory Cells:
Odorant dissolves in mucus and attaches to receptors on olfactory cilia.
Involves a cascade effect through G-proteins and second messengers, leading to depolarization and action potential generation in the olfactory nerve.
Quality of a Good Odorant:
Small (3-20 Carbon atoms), volatile, water-soluble, and lipid-soluble.
Facilitated by odorant-binding proteins in mucus.
Membrane Potential and Action Potential:
Resting membrane potential: -55mV.
Action potential frequency in the olfactory nerve increases with odorant strength.
Adaptation Towards the Sense of Smell:
Rapid adaptation within the first second, with further slow adaptation.
Psychological adaptation greater than receptor adaptation, involving feedback inhibition from the central nervous system.
Primary Sensations of Smell:
Camphoraceous, Musky, Floral, Pepperminty, Ethereal, Pungent, Putrid.
Odor Detection Threshold:
Examples: Hydrogen sulfide (0.0005 ppm), Methyl-mercaptan (0.002 ppm).
Some toxic substances are odorless at lethal concentrations.
Characteristics of Smell:
Odor blindness for single substances due to lack of appropriate receptor protein.
Behavioral and emotional influences of smell.
Transmission of Olfactory Signals:
From olfactory cells to glomeruli in the olfactory bulb, involving lateral inhibition.
Primitive, less old, and new olfactory systems with different path
The prostate is an exocrine gland of the male mammalian reproductive system
It is a walnut-sized gland that forms part of the male reproductive system and is located in front of the rectum and just below the urinary bladder
Function is to store and secrete a clear, slightly alkaline fluid that constitutes 10-30% of the volume of the seminal fluid that along with the spermatozoa, constitutes semen
A healthy human prostate measures (4cm-vertical, by 3cm-horizontal, 2cm ant-post ).
It surrounds the urethra just below the urinary bladder. It has anterior, median, posterior and two lateral lobes
It’s work is regulated by androgens which are responsible for male sex characteristics
Generalised disease of the prostate due to hormonal derangement which leads to non malignant enlargement of the gland (increase in the number of epithelial cells and stromal tissue)to cause compression of the urethra leading to symptoms (LUTS
4. Hormone receptors
For protein & peptide hormones – receptor is
in plasma membrane
For steroid hormones – receptor is in
nucleus
For prostaglandin hormones – receptor is in
plasma membrane
7. Steps in protein hormone action
1. Hormone-receptor binding
2. G-Protein activation
3. Adenylate cyclase activation
4. Protein kinase activation
5. Synthesis of new products
8. Mechanism of Hormone Action
Receptor
Protein Kinase A
(PKA)
Nucleus
DNA
Protein
Synthesis
(Enzymes)
Plasma Membrane
Protein Hormones
(cAMP second messenger)
C
R
R-ER
Protein Synthesis
Mitochondria
S-ER
Steroid Synthesis
LH
G
Adenylate Cyclase
9. Mechanism of Hormone Action
Receptor
Protein Kinase A
(PKA)
Nucleus
DNA
Protein
Synthesis
(Enzymes)
Plasma Membrane
Protein Hormones
(cAMP second messenger)
G
Adenylate Cyclase
C
R
cAMP
LH
ATP cAMP
C
R
R-ER
Protein Synthesis
Mitochondria
S-ER
Steroid Synthesis
10. C
R
cAMP
Mechanism of Hormone Action
Receptor
Protein Kinase A
(PKA)
Nucleus
DNA
Histones
Protein
Synthesis
(Enzymes)
Plasma Membrane
Protein Hormones
(cAMP second messenger)
G
Adenylate Cyclase
LH
ATP cAMP
(+ PO4)
R-ER
Protein Synthesis
Mitochondria
S-ER
Steroid Synthesis
mRNA
11. Mechanism of Hormone Action
Receptor
Protein Kinase A
(PKA)
Nucleus
DNA
Histones
Protein
Synthesis
(Enzymes) mRNA
Plasma Membrane
Protein Hormones
(cAMP second messenger)
Cholesterol
G
Adenylate Cyclase
C
R
cAMP
LH
ATP cAMP
(+ PO4)
R-ER
Protein Synthesis
Mitochondria
CholesterolPregnenolone
S-ER
Steroid Synthesis
Testosterone
12. Mechanism of Hormone Action
Receptor
Protein Kinase A
(PKA)
Nucleus
DNA
Histones
Protein
Synthesis
(Enzymes) mRNA
Plasma Membrane
Protein Hormones
(cAMP second messenger)
Cholesterol
G
Adenylate Cyclase
C
R
cAMP
LH
ATP cAMP
(+ PO4)
R-ER
Protein Synthesis
Mitochondria
CholesterolPregnenolone
S-ER
Steroid Synthesis
Testosterone
14. Protein Hormones (Ca2+ Second Messenger)
PLC
Endoplasmic Reticulum
Ca2+
Protein
Kinase C
Plasma Membrane
GnRH
Receptor
G-protein
R
Plasma
Membrane
Secretory
Granules
PIP2
15. Protein Hormones (Ca2+ Second Messenger)
PLC
PIP2
Endoplasmic Reticulum
Ca2+
Plasma Membrane
GnRH
Receptor
G-protein
R
Plasma
Membrane
Secretory
Granules
PIP2
Protein
Kinase C
16. Protein Hormones (Ca2+ Second Messenger)
PLC
PIP2
Endoplasmic Reticulum
Ca2+
Protein
Kinase C
Plasma Membrane
GnRH
Receptor
G-protein
DAG
IP3
R
Ca2+
Plasma
Membrane
Secretory
Granules
R
PIP2
17. Protein Hormones (Ca2+ Second Messenger)
PLC
PIP2
Endoplasmic Reticulum
Ca2+
Protein
Kinase C
Plasma Membrane
GnRH
Receptor
G-protein
DAG
IP3
R
Ca2+
Plasma
Membrane
Ca2+
Secretory
Granules
R
PIP2
18. Protein Hormones (Ca2+ Second Messenger)
PLC
PIP2
Endoplasmic Reticulum
Ca2+
Protein
Kinase C
Plasma Membrane
GnRH
Receptor
G-protein
DAG
IP3
R
Ca2+
Plasma
Membrane
Ca2+
LH
Fusion
Secretory
Granules
R
PIP2
19. Calcium Second Messenger Hormones
GnRH
Triggers release of LH in anterior pituitary
Oxytocin
Triggers contractions of smooth muscle
PGF2α
Triggers apoptosis of cell
Inhibition of progesterone synthesis
20. Steroid Hormone Action (Slow)
Cytoplasm
Cell Membrane
DNA
Receptor
Nucleus
Steroid
(estrogen)
Diffusion?
mRNAR-ER
Protein synthesis
New
Protein
Change in
Cell
Physiology
22. Steroid Hormone (Fast)
Receptor
Protein Kinase A
(PKA)
Nucleus
DNA
Histones
Protein
Synthesis
(Enzymes) mRNA
Plasma Membrane
(cAMP second messenger)
G
Adenylate Cyclase
C
R
cAMP
Estradiol
ATP cAMP
(+ PO4)
R-ER
Protein Synthesis
Ca2+
Ca2+
Smooth Muscle Contraction
(Uterine Myometrial Cell)
23. Steroid Hormone (Fast)
Not the classical mechanism of action of a steroid
hormone
Requires plasma membrane receptor
Operates via protein kinase activation
Estradiol – smooth muscle of uterus
24. Positive & Negative Feedback
Major “controllers” of reproductive hormones
Positive feedback – stimulation of GnRH
Negative feedback – suppression of GnRH
25. Progesterone
Causes strong negative feedback
Strongly inhibits GnRH neurons – when
progesterone is high, there is only a basal
secretion of GnRH
Females under progesterone (midcycle or
pregnant) do not cycle for a period of time that
progesterone is high
26. Estradiol
When estradiol reaches a threshold level, the
surge center releases large quantities of GnRH
Causes release large quantities of LH that
stimulate ovulation
Hormone action requires the presence of receptors.
Hormones (green spheres) are produced by the cells of the endocrine gland and are released into the blood.
The blood delivers the hormones to the target tissue.
TARGET TISSUES contain receptors (orange) that specifically bind the hormone.
NONTARGET TISSUES also have receptors but for other hormones. The specific hormone here will not bind to these receptors.
HORMONES WILL ONLY BIND TO THEIR TARGET TISSUES – CONTAIN SPECIFIC RECEPTORS FOR THAT HORMONE.
NON-TARGET TISSUE WILL NOT RESPOND.
Once the hormone binds to its specific receptor in the target tissue, the target tissue performs its function.
Different hormones act on different types of receptors.
HYPOTHETICAL MODEL OF A RECEPTOR FOR A PROTEIN HORMONE (LH)
Receptors for protein hormones are integral part of the plasma membrane.
They have 3 distinct regions – these regions are referred as the receptor domains.
The receptor for protein hormone (LH) are present in the plasma membrane
HORMONE-RECEPTOR BINDING (1)
The hormone (LH) binds to a specific receptor in the plasma membrane.
ACITVATION OF THE G-PROTEIN (2)
The formation of a hormone-receptor complex activates G-PROTEIN (a membrane-bound enzyme).
G-PROTEIN is transformed and this activates another membrane-bound enzyme – ADENYLATE CYCLASE.
ADENYLATE CYCLASE converts ATP to cAMP.
CYCLIC AMP activates PROTEIN KINASES (cytoplasm). The regulatory subunit binds cAMP and this causes activation of the catalytic subunit that initiates conversion of existing substrates to new products.
SYNTHESIS OF NEW PRODUCTS (4)– products made by the cell are secreted
In this figure, since the final product is testosterone, we can assume that the target tissue is the LEYDIG CELLS OF THE TESTIS.
LH can also bind with the target tissue OVARY (FOLLICLE CELLS) to produce estradiol.
The target enzyme is phospholipase C (PLC).
PLC splits phosphatidyl 4,5, bisphosphate (PIP2) into diacylglycerol (DAG) and Inositol 1,4,5 trisphosphate (IP3).
IP3 acts by binding to IP3 receptors on the endoplasmic reticulum (ER), and releasing the Ca2+ stored within. IP3 receptors are Ca2+ channels, activated by IP3 binding.
STEPS OF STEROID HORMONE SYNTHESIS
Steroid transport
Movement through the cell membrane and cytoplasm
Binding of steroid to nuclear receptor – specific nuclear receptor (if the cell is a target cell)
MRNA synthesis and protein sysnthesis – MRNA leaves the nucleus and attaches to ribosomes where it directs synthesis of specific proteins
*Example of a hormone that exhibits a strong negative feedback
*Example of a hormone that exhibits a strong positive feedback