Explain why a firewalker can step quickly without harm on red-hot coals with bare feet.
THE CELL RER o The synthesis of proteins that will be secreted from the cell or incorporated into the plasma membrane, or are destined for another organelle SER o The site of synthesis of lipids, including triglycerides and steroids o A site for calcium ions o Specialized in certain cells Attached (bound) ribsosomes o Located on the surface of the endoplasmic reticulum o Produce proteins that are transported out of the cell Free ribosomes o Located in the cytoplasm o Produce proteins that are used by the cell Golgi apparatus o Cis face associated with endoplasmic reticulum o Trans face associated with plasma membrane o Processes molecules synthesized in the endoplasmic reticulum and prepares them for transport to their final location o Packages molecules into vesicles Lysosomes o Degrate intracellular debris and extracellular debris that has been taken into the cell o Digestive enzymes Peroxisomes o Oxidative enzymes o Membrane, enzyme core, lume o H2O2 H2O+ O2 Hydrogen peroxide water and oxygen Mitochondria o Outer and inner membranes, matrix, cristae o Has there own DNA o “Powerhouses” because of ATP produced Exocytosis o Ribosome deposits protein in ER o Protein exits ER o Protein enters Golgi for processing o Protein exits Golgi o Protein exits cell Endocytosis movement inside the cell o Pinocytosis Process of bringing small amounts of fluid in the cell “cell drinking” o Phagocytosis these cells bring in solids and debris to destroy “cell eating” Cytoskeleton Meshwork throughout cytosol Anchors organelles Microtubules o Hollow o Protein tubulin o Largest tubule o Functions include: Maintains shape by resisting pushing Cell division Moves cell o Microtubule track ——> vesicle (within axon) Actin Filaments (microfilaments) o Protein actin o Double helix o Smallest tubule o Functions include moving organelles Intermediate filaments o Protein keratin o Wound into thick cables o Functions include Anchors the nucleus Resists tension CAMS Cell Membrane Cytosol (ICF) Plasma membrane • Hydrophilic phosphate head • Hydrophobic fatty acid tails Extracellular fluid (ECF) Concentration gradient between ICF and ECF Membrane proteins • Many different membrane proteins • Help function the cell Channels • Allows small polar molecules to go down concentration gradient • Specific channels allow only certain things to pass through (ex: calcium channels) • Regulated channels open and close Carriers • Means of transporting large polar molecules through concentration gradient • Specific carriers depends on shape Passive transport • Does not require ATP • Ex: Facilitated diffusion with aid Active transport • Does require ATP Enzymes • Biological catalyst • Chemical messengers Hormones • Speeds up reactions Anchors • Cytoskeleton to membrane Cell Adhesion molecules • Forms tissues • Attach cells together Surface markers • Found on outer surface • Allows cells to recognize “like” cells • Forms tissues Receptors Membrane Carbohydrates Are attached to protein or lipid as glycoprotein or glycolipid Membrane sugars seem to be involved in identification and recognition Ampipathic molecule o Molecule with both a polar and non polar region Phospholipids o Amphipathic molecules that align themselves in the membrane in a bimolecular layer such that their hydrophilic region is oriented toward the aqueous border (either extracellular fluid or the cytosol, or the intraorganelle fluid or cytosol), and their nonpolar fatty acid chains are oriented toward the middle of the membrane Membrane Transport Solubility o ECF and ICF o Water and ions move through channels o Glucose and amino acids move by carrier proteins o Polar o Nonpolar can permeate the plasma membrane and will simply move across the membrane by diffusion Size o Small polar molecules can get through protein channels o Large polar molecules require a carrier 2 Post Receptor Binding Events 1) Channel regulation • Chemical messenger opens or closes channel • Change in activity of the cell 2) Activation of second messenger systems • Binding of chemical messenger to receptor • Activates adenylate cyclase • Adenylate cyclase catalyses the conversion of ATP cAMP • Cyclic AMP actives protein kinase A (cAMPdependent) • Adds phosphate group to specific protein • Altered protein shape and function brings about cellular response • Connective Tissue Binds, anchors, supports other tissues Extensive amount of extracellular matrix (ECM) widely scattered cells embedded in a mass of noncellular material that contain a dense meshwork of proteins and other • Collagen strength in tissues • Elastingives the tissue the ability to stretch and recoil Bones, blood, tendons, cartilage, adipose tissue Intercellular Junctions Desmosomes • Attach cells together • Adhering junction • Things can get between • EX: Heart cells Gap Junctions • Create gaps that connect animal cells • Create tunnels (connexons) Tight Junctions • Impermeable junction Intercellular Chemical Messengers Paracrine • Chemical messenger that communicates with cells by simple diffusion • Binds to receptor • Secretory ———> target cell • Can only act upon nearby cells • EX: Histamine causes blood vessels to dilate • Short distance signals Neurotransmitters • Chemical messenger that is released from the axon terminal of a neuron • Pre and post synaptic neuron • Electricity Hormones • Chemical messenger release from endocrine cells or glands into the interstitial fluid to then diffuse into the blood and travel to target cells • Released into blood • Secretory cells find target cells Neurohormones • Chemical messenger release from neurosecretory cells into the interstitial fluid and then is diffused into the blood to travel to target cells Osmosis passive movement of water molecules across a membrane, down it’s concentration gradient Diffusion passive movement of molecules from one location to another due to their thermal motion Fick’s laws of diffusion when a substance crosses a membrane, the net flux is proportional to the size of the concentration gradient Concentration gradient difference in the concentration of a substance between regions Electrical gradient difference in electrical charge of a substance between regions Electrochemical gradient sum of electrical and chemical gradients acting on an ion or charged molecule Active transport o Requires energy o Carried out proteins called pumps Passive transport o Does not require energy o Includes simple diffusion and forms of mediated transport Carrier mediated transport o Movement of substances across the plasma membrane by protein carrier molecules (integral membrane protein) used when molecule cannot cross membrane or crosses very slowly protein carrier molecules are embedded in lipid, and have site which specifically binds the molecules binding of the molecule to the site promotes a conformational change in protein carrier, resulting in transport of molecule across membrane. Channel is never formed o Facilitated diffusion Downhill Higher concentration lower concentration With aid o Specificity transporters can only bind to one molecule or family of closelyrelated molecules o Saturation rate of transport depends on substrate concentration and number of carriers o Competition if a transporter bind several related molecules, those molecules will compete for binding to the transporter Na+/K+ Pump Active Transport Pumps sodium and potassium Sodium is being pumped uphill Dephosphorylated Potassium is released 3 Na+ for every 2 K+ Pump requires energy Against the concentration gradient = Uphill pump Electrical properties of the plasma membrane o Anions are negative and nondiffusible in ICF (can’t get out of cell) o Actions of the sodium/ potassium pump More permeable to potassium than sodium It requires energy to move potassium into the cell but doesn’t require energy to get out Pump’s concentration gradient favors potassium’s movement into the cell Membrane Channels Leaky • Always open • Not regulated Ligand • Chemical messenger gated • Channels open only when it receives a receptor Voltage gated • Depends on the voltage of the channel (open or closed depending) Excitable tissues tissues such as neurons or muscles that are capable of producing action potentials Polarization Resting state of the cell Depolarization Change to positive potential of cell o Caused by opening of Na+ channels and movement of Na+ into the cell Repolarization Return of the membrane to resting membrane potential o Caused by Na+ channels closing o K+ channels open and K+ move out the cell Hyperpolarization Change to a negative potential of a cell o Caused by K+ channels slowly closing o 80mV below resting membrane potential Graded Potentials Short distance signals (die out very quickly) Decremental (keeps getting stronger) Strength is proportional to stimulus strength Action Potentials Long distance signals (released at axon terminal) Nondecremental Strength is not proportional to stimulus Resting membrane potential o – 70mV no potential energy o Polarization Threshold o Voltage for a typical cell is 55mV o Voltage at which many sodium gates open o Sodium gates are closed if lower than 55mV (ex: 70mV) Rising phase o Due to sodium influx o Sodium (Na+) gates are open and sodium is going into the cell o Depolarization At peak o Voltage reaches +30mV o Potassium (K+) gates are open and potassium goes out of the cell (positive charge) o More potassium can leak out at rest Falling phase o Due to potassium deflux o Voltage gates open for potassium to get back down to resting membrane potential (70mV) o Repolarization Discuss the movements of ions during resting membrane potentials and action potentials, including if they require energy or not. Myelin o Lipid (non polar) o Material that surrounds many of the axons in our body o A good insulator o PNS Swhwann cells o CNS Oligodendrocytes Formation and origin of myelin sheaths o Nodes of Ranvier gaps within the myelin along the axon o Myelin increases the speed of impulses in the axon Saltatory conduction o Action potential conduction occurring in myelinated axons o The “jumping” of impuses from node to node Multiple sclerosis. o Autoimmune disease that attacks myelin of oligdodendrocytes and leaves scarring o Scarring slows down or blocks an action potential along it’s pathway o Symptoms include blurred vision, difficulty balancing and muscle weakness Axonal regeneration in the PNS o CNS neurons cannot reproduce o Schwann cells can reproduce o Regeneration tube guides the slowly growing axon One way propagation of current o Na+ voltage gates have 3 confirmations 1) Open 2) Closed can be opened with stimulation 3) Closed can’t be opened EVENTS AT THE SYNAPSE: Synapses dendrites (from cell body) receive input from other neurons at specialized junctions Presynaptic neurons the cell that releases the neurotransmitter Postsynaptic neurons the target cell (which can be another neuron, gland cell, or a muscle cell) Events at a synapse 1) Action potential arrives at the axon terminal of the presynaptic neuron 2) Voltage calcium gates open because of action potential 3) Calcium diffuses in 4) Exocytosis of neurotransmitters 5) Neurotransmitters bind to postsynaptic receptors on neuron 6) Channel Regulation 1) Increase in permeability to sodium a. Diffuses in, depolarizes b. Creates EPSP c. Brings membrane closer to threshold 2) Increase in permeability to potassium a. Potassium diffuses out b. Hyperpolarization c. More positives are leaving (below 70mB) d. Creates IPSP 3) Increase in permeability to chloride a. Hyperpolarization b. Chloride diffuses in c. IPSP EPSP o Excitatory postsynaptic potential o Graded potential where depolarization increase as more neurotransmitters bind to more receptors o Increase in Na+ permeability IPSP o Inhibitory postsynaptic potential o Graded potential where hyperpolarization occurs due to K+ channels opening when neurotransmitters bind to receptors o Increase in K+ permeability o Increase in Cl permeability EPSP and IPSP cancelling out o Occurring at the same time o Two different inputs o No change in membrane potential GPSP o Grand postsynaptic potential o Sum of all the EPSP and IPSP occurring at the same time on the postsynaptic neuron Spatial summation addition of graded potentials generated at different locations when stimulated around the same time Temporal summation addition of graded potentials generated at a specific site when stimulated at high frequency (several occurring in a row) Convergence o Many presynaptic neurons converge onto a single postsynaptic neuron Divergence o One neuron branches out to effect others NS: Peripheral nervous system o Consists of neurons that provide communication between the CNS and organs throughout the body o Afferent Transmits sensory and visceral information Somatic senses (skin, muscles, joints) and special senses (vision, hearing, equilibrium, smell and taste) o Efferent Effectors of somatic nervous system Skeletal muscle Effectors of autonomic nervous system Sympathetic cardiac muscle, smooth muscle, glands Parasympathetic enteric nervous system, gastrointestinal tract Autonomic nervous system Parasympathetic vs. Sympathetic systems including: Rest and digest parasympathetic o Both stimulates the digestive organs (enhancing the digestion and absorption of nutrients) and inhibits the cardiovascular system (decreasing heart rate) Fight or flight response sympathetic o Prepares the body to cope with threatening situations o The rate and force of the heart’s contractions increase, blood flow shifts from gastrointestinal organs to skeletal and cardiac muscles, and energy stores are mobilized tonic activity Dual innervation Autonomic NS innervates most organs Exceptions to dual innervations o Innervated by sympathetic fibers o Adrenal medulla o Sweat glands o Arrector pilli muscles o Most blood vessels Sympathetic system: o Thoracolumbar division o Preganglionic neurons have short axons that originate in the lateral horn o Several postganglionic neurons have long axons that travel to the effector organ o Sympathetic chains and collateral ganglia (celiac division) o Innervates endocrine tissue (adrenal medulla), stomach, liver, spleen, small intestine, upper part of large intestine, kidneys, urinary bladder, and reproductive organs Parasympathetic system: o Craniosacral division o Preganglionic neurons are long and terminate in the ganglia Originate from cranial nerve Originate in spinal cord o Postganglionic neurons are short and travel to the effector organ o Cranial nerves innervate lungs, heart, stomach, small intestines, liver, sooth muscles of the eye, smooth muscle and glands of throat, and viscera of thorax and abdomen, etc. o Pelvic nerves innervate the colon, bladder and reproductive organs Cholinergic receptors Acetylcholine o Nicotinic Ionotropic 2 binding sites for acetylcholine Binding of acetylcholine triggers the opening of channels that allow both sodium and potassium to move through causing an EPSP in the postsynaptic cell o Muscarinic Metabotropic receptors that operate through the action of a G protein Acetylcholine binding causes opening and closing of ion channels and activation of enzymes Dominant cholinergic receptor type in CNS Andrenergic receptors neurons that release norepinephrine (from sympathetic postganglionic neurons) Adrenal glands and sympathetic innervations o Preganglionic neuron innervates tissue o Medulla consists of modified sympathetic postganglionic cells (chromaffin cells) that developed into endocrine cells instead of neurons o Output 80% catecholamine, 20% norepinephrine, and very little dopamine o Releases hormones into the bloodstream and contributes widespread effects on sympathetic activation