VPHY3100 Notes: Week of 8/24
VPHY3100 Notes: Week of 8/24 VPHY 3100
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This 5 page Class Notes was uploaded by Lorin Crear on Sunday August 30, 2015. The Class Notes belongs to VPHY 3100 at University of Georgia taught by Dr. Li, Dr. Wells, Dr. Brown in Summer 2015. Since its upload, it has received 353 views. For similar materials see Elements of Physiology in Animal Science and Zoology at University of Georgia.
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Date Created: 08/30/15
Chapter 6 Interactions Between Cells amp Their Extracellular Environment 0 Membrane Transport Proteins 0 Only gases and small uncharged polar molecules can move through simple diffusion in and out of the cell I Solute can only cross membrane at certain maximum rate 0 Ions large uncharged polar molecules and charged polar molecules move through carriermembrane transport proteins 0 Pumps carriers aka transporters and channels I Transporters may also be used to encompass all transport proteins 0 Types of proteins I ATPpowered pumps 0 Move molecules against gradient I Ion channels 0 Move molecules down gradient I Transporters 0 Uniporters 0 Moves one molecule at a time down gradient 0 Symporter aka cotransporter 0 Moves one molecule down gradient 0 Energy generated from first molecule used to move another against its gradient 0 Molecules move in same direction 0 Antiporter aka exchanger 0 Moves one molecule down gradient 0 Energy generated from first molecule used to move another against its gradient 0 Molecules move in opposite directions 0 Channels affect change faster than carriers Which are faster than pumps channels gt carriers gt pumps 0 Energetics of Membrane Transport Protein I Passive transport 0 Facilitated diffusion 0 Molecule is moved down gradient 0 All channels and uniporters I Active transport 0 Molecule is moved against gradient 0 Primary active transport O O o Implies harnessing of some primary energy source e g ATP 0 All pumps 0 Second active transport 0 Relies on energy of one molecule moving down gradient to move another against gradient 0 Made possible by gradients established by pumps primary active transporters o Symporters and antiporters SodiumPotassium Pump I Maintains primary ionic concentration gradient Na across plasma membrane 0 High sodium concentration outside cell low inside 0 Low potassium concentration outside cell high inside 0 Primarily created by ion channel activity I Electrogenic net movement of charge With each cycle 0 Moves 3 Na ions out of cell and 2 K into cell With each ATP molecule used Vesicular Transport I Large polar molecules e g neurotransmitters can t move through membrane or membrane transporters I They are brought intaken out via vesicular fusion I Vesicles are pinched off pieces of cell membrane that form capsule around molecules for transport I Entering cell endocytosis I Exiting cell exocytosis o Membrane potential Vm O 0000 The charge gradient across plasma membrane that exists in addition to concentration gradients More negative inside cell than outside cell Resting membrane potential Vr is typically 60 to 80 mV Mostly determined by leaky K channels Dependent on ionic concentration gradients and permeabilities of each ion across membrane Vr is approximately equal to Ek Nernst equilibrium of K ions due to leaky channels 0 Nernst Equation 0 Represents balance point between chemical and electrical diffusional forces acting on ion 61mV x 0 Ex 2 Z l0g10x forlonx I Z magnitude and sign of ion s charge I First half of equation pertains to electrical potential I Second half logarithm pertains to chemical potential I When EX Vm there is no longer net movement of ion x across membrane 0 Can be used in conjunction With membrane potential and charge of ion x to predict net movement of ion x 0 Cell Signaling 0 Cells communicate With each other via chemical signals 0 Types I Local signaling 0 Autocrine signaling same type of cell sends and receives 0 Paracrine signaling different type of cell sends than receives I Neurotransmission I Endocrine signaling 0 Target cells respond to signals via receptor proteins 0 Receptor Proteins o Channellinked receptors I aka ligand gated ion channels I transmembrane proteins With binding site on outside of cell changes shape openscloses in response to binding I EX acetylcholine and nicotinic receptor 0 Enzymelinked receptors I Transmembrane enzyme activated in response to binding I Converts substrate to product inside cell When activated 0 Gproteincoupled receptors I Transmembrane receptor activates Gprotein in response to binding 0 Intracellular receptors I Inside of cell I Activated When signaling molecule passes through membrane to bind Chapter 7 The Nervous System 0 Terminology 0 Central Nervous System CNS brain and spinal chord Peripheral Nervous System PNS nervous tissue outside CNS Nuclei CNS vs Ganglia PNS I Clumps of neuronal cell bodies grey matter 0 Tracts CNS vs Nerves PNS I Fibers o Bundles of axons 0 Anatomy of Neuron o Dendrites I Center of input functions Cell body I Houses typical organelles nucleus endoplasmic reticulum etc o Axon hillock I Center of output functions 0 o Axon I Some dotted with myelin sheaths for insulation I Internodes 0 Spaces between sheaths 0 Location of action potentials o Nerve terminals I Release neurotransmitters into synapse 0 Classes of Neurons 0 Functional classes I Afferent neurons 0 Sensory neurons 0 Information ows to CNS I Efferent neurons 0 Motor neurons 0 Information ows away from CNS I Interneurons 0 Short distance signaling between different types of neurons 0 Morphological classes I Pseudounipolar o Effectively a simple axon 0 Typical for afferent sensory neurons I Bipolar o Dendrite and axon portions 0 Typical interneurons in retina I Multipolar 0 Many different processes emanate from cell body 0 Typical for motor and projection neurons Glial cells 0 Aka support cells 0 Microglia I Immune cell in interstitial uid 0 Ependymal cells I Barrier between cerebral spinal uid and interstitial uid of brain 0 Astrocytes CNS I Most abundant type I Multiple end feet either make connections With surrounding nerve cells or capillaries near brain I Converts glucose to lactate and shuttles it to neurons I Cleans up glutamate and K ions in very active synapses I Important for proper brain development establishment and maintenance of bloodbrain barrier o Oligodendrocytes CNS I Insulates central axons I Can wrap around about 15 different neurons and create myelin sheaths out of membrane 0 Schwann cells PNS I Insulates peripheral axons I Unlike oligodendrocytes one Schwann cell one internode I Neurilemma vs myelin sheath 0 Every PNS axon has internodes but not all truly myelinated 0 Neurilemma aka sheath of Schwann made of body of Schwann cell 0 Typically larger axons have true myelin sheaths to prevent leakage of current 0 Smaller axons typically only have neurilemma
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