Topic 1 - Homeostasis + Biological Signalling Molecules PDF

🍪 Topic 1 - Homeostasis + Biological Signalling Molecules Define Homeostasis Maintenance of a constant internal environment Not a steady state but a dynamic equilibrium...

🍪 Topic 1 - Homeostasis + Biological Signalling Molecules Define Homeostasis Maintenance of a constant internal environment Not a steady state but a dynamic equilibrium 3 levels of Homeostasis Intracellular - Control of [Ca2+] Organ - local control of Blood flow Whole Body: Thermoregulation Characteristics of Control Systems 1. Communication Nervous - action potential Endocrine - hormones Paracrine - local hormones Autocrine - many agents Topic 1 - Homeostasis + Biological Signalling Molecules 1  2. Control centre Determines set point, input & response 3. Receptor Stimuli → Sensor → Signal Afferent Pathway (information from sensory receptors) → Control Centre 4. Effector Control Centre → Effector → Efferent Pathway (motor information away from the central nervous system) Failure of homeostasis can lead to…. disease Thermoregulation - what occurs if the core temperature is GREATER than 37.2 degrees (NF) Thermoregulation - what occurs if the core temperature is BELOW 36.7 degrees (NF) Topic 1 - Homeostasis + Biological Signalling Molecules 2  Define Positive Feedback Stimulus produces a response which increases its effect System goes out of control Leads to a ‘catastrophic’ change (change in state) Biological Rhythms Pyrexia (Fever) Normal response to infection Core temp raised to higher set point Prostaglandin E2 (PGE2) acts on thermoregulatory centre Topic 1 - Homeostasis + Biological Signalling Molecules 3  Antipyretic drugs inhibit cyclo-oxygenase 2 (COX-2) enzyme, which produces PGE2 What is Hyperthermia Core temp above 38°C Malignant hyperthermia – rare reaction to some anaesthetic agents Artificially induced hyperthermia - used in the treatment of some cancers What is Hypothermia Core temp less ADH Production from P.P Gland —> Little/No water reabsorbed from collecting ducts in Kidneys —> Osmorality increases Topic 1 - Homeostasis + Biological Signalling Molecules 5  Lecture 1.2 - Biological Signalling Molecules Define Ligand + Receptor Ligand: small molecule that binds specifically to a receptor site Receptor: a molecule that binds a ligand and produces a response Define Agonist ligand Agonist: binds to a receptor and activates it Define Antagonist Ligand Antagonist: binds to a receptor, but does not activate it Define Partial Agonist Ligand Partial agonist: binds to a receptor, but does not produce a maximum response Topic 1 - Homeostasis + Biological Signalling Molecules 6  Endogenous Biological Signalling Includes…. Endogenous Endocrine - hormones Paracrine – local hormones Autocrine – many agents Neurotransmitters Exogenous Biological Signalling Includes…. Drugs Some hormones can be used as drugs e.g insulin, adrenaline Some drugs mimic hormones What are the 3 Major Types of Signalling Molecules (info) Hydrophilic 1 - Amines (Catecholamines) Amino acid derivatives – small charged hydrophilic Receptors in Plasma Membrane Hydrophilic 2 - Peptides + Proteins Short chain to complex e.g. Insulin 51 amino acids Receptors in cell membrane Lipophilic – Steroids Common derivation from cholesterol Receptors are intracellular Topic 1 - Homeostasis + Biological Signalling Molecules 7  Summary Table of the Common Neurotransmitters’ Signalling Function (info) Classification; Amino Acids, Monoamines, Peptides Exception - Acetylcholine What are 4 targets for drugs (RITE) Receptors Ion Channels Transporters - has a specific shape Enzymes What are the 4 types of Receptors (KING) Kinase Linked Receptors (K) Ion Channels (Ligand Gated) (I) Topic 1 - Homeostasis + Biological Signalling Molecules 8  Nuclear/Intracellular (N) G-Protein Coupled Receptors (G) Tyrosine Kinase Receptors activated due to phosphorylation Ion Channels (Ligand Gated) - Ionotropic Receptors When these channels bind with the ligand - open ion channels for duration of binding – many fast neurotransmitters: ACh; GABA Changes permeability of membrane to a specific ion or allows entry e.g. Ca2+ Ion Channels enable selective flow of ion current down its electrochemical gradient Topic 1 - Homeostasis + Biological Signalling Molecules 9  Nuclear/Intracellular Receptors Ligands need to be lipid soluble e.g. steroids. When bound ligand receptor complex migrates to nucleus —> binds to gene transcription factor G-Protein Coupled Receptors/GPCRs Largest receptor group in humans Includes: hormones, opioids Involves 'slow' neurotransmitters Three major types: Gs, Gi, Gq, which activate different intracellular signalling pathways How does Receptor-G Protein-Effector Signalling work? Agonist = a substance which initiates a physiological response when combined with a receptor. Topic 1 - Homeostasis + Biological Signalling Molecules 10 Topic 1 - Homeostasis + Biological Signalling Molecules 11