VPHY 3100: Week of 8/31
VPHY 3100: Week of 8/31 VPHY 3100
Popular in Elements of Physiology
Popular in Animal Science and Zoology
verified elite notetaker
This 8 page Class Notes was uploaded by Lorin Crear on Friday September 4, 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 105 views. For similar materials see Elements of Physiology in Animal Science and Zoology at University of Georgia.
Reviews for VPHY 3100: Week of 8/31
Report this Material
What is Karma?
Karma is the currency of StudySoup.
Date Created: 09/04/15
Chapter 7 The Nervous System Note Typo in Week 1 Notes stated that intemodes are spaces between myelin sheaths This is INCORRECT Nodes or Nodes of Ranvier are spaces between myelin sheaths Internodes are the parts of the axon covered by myelin sheaths o Membrane Potential and Electrical Excitability o Neurons muscle cells and cardiac cells are electrically excitable cells I Membrane potential Vm uctuates due to changes in membrane s permeability to certain ions I Resting membrane potential VI of neuron 70 mV 0 Fluctuations in Membrane Potential I Depolarization Vm becomes more positive than Vr I Hyperpolarization Vm becomes more negative than Vr I Repolarization Vm moves back toward Vr 0 Ion channels and the Action Potential 0 Types of ion channels I Mechanicallygated I Ligandgated aka ionotropic receptors I Voltage gated o Involved in action potential 0 Action Potential I An electrical wave running the length of the axon I Allornothing can t have half an action potential either occurs or not I Threshold membrane potential for action potential 55 mV I Depolarization 9 repolarization 9 hyperpolarization 9 slower repolarization 0 Ion Channels of Action Potential I Fast Na channel 1 At Vr main gate closed and inactivation gate open 2 Main gate opens during depolarization Na begins to ow 3 In ux of Na causes further depolarization 4 After short delay inactivation gate closes in response to voltage change Na can no longer ow 5 Membrane returns to Vr 6 Main gate closes Inactivation gate opens I Slow K channel 1 At Vr gate closed 2 Gate opens during depolarization 3 Out ow of K causes repolarization 4 Membrane returns to Vr 5 Gate closes o Refractory Periods I Absolute refractory period 0 Membrane incapable of generating another action potential 0 Due to inactivated Na channels 0 During period of depolarization and first repolarization I Relative refractory period 0 More difficult for another action potential to be generated 0 Na channels are fully closed and could potentially be opened 0 After absolute refractory period during second repolarization I Prevents voltage charge of action potential going back up axon I Limits frequency of action potentials o Conduction of Action Potentials I Larger internal core of axon possible to carry more current I BUT larger internal core of axon larger surface area of axon more ion channels on membrane more leakage I Larger axons are myelinated to prevent this leakage I Myelin sheaths also increase velocity of action potentials o salutatory conduction action potentials are regenerated at nodes of Ranvier and jump over each myelin sheath to the next node 0 The synapse and synaptic transmission 0 Terminology I Synapses can be electrical or chemical 0 We are focused primarily on chemical synapses I Synaptic cleft 0 Physical space between presynaptic nerve terminals and postsynaptic neuron 0 Filled With extracellular uid I Presynaptic cell sends signals I Postsynaptic cell receives signals 0 Types of synapses I Axosomatic 0 Nerve terminals of presynaptic neuron communicate With soma of post synaptic neuron I Axodendritic 0 Nerve terminals of presynaptic neuron communicate With dendrites of post synaptic neuron 0 Most common I Axoaxonic 0 Nerve terminals of presynaptic neuron communicate With nerve terminals of post synaptic neuron o Neurotransmission synaptic transmission 1 Release of neurotransmitters NTs from presynaptic nerve terminal 0 Action potential reaches axon terminals 0 Voltagegated Ca2 ion channels open 0 Exocytosis of NTs caused by Ca2 ions 2 Interaction of NTs With postsynaptic cell membrane 0 Postsynaptic receptor either ligandgated ion channel or Gprotein coupledreceptor 0 Response of postsynaptic neuron depends on type of NT and type of receptor 0 Responses of receiving cell 0 Excitatory PostSynaptic Potential EPSP depolarization o Inhibitory PostSynaptic Potential IPSP hyperpolarization o Acetylcholine I When interacting with nicotinic acetylcholine receptor ligandgated ion channel produces EPSP and contracts muscles I When interacting With muscarinic acetylcholine receptor Gproteincoupledreceptor on cardiac cell produces IPSP I nicotinic and muscarinic refers to acetylcholine receptors specifically 3 Removal of NTs from synaptic cleft 0 Reuptake o By secondary active transporters or glial cells 0 active 0 Digestion o By enzymes 0 active 0 Diffusion 0 Into rest of extracellular uid 0 Passive o A particular synapse Will usually rely on just one active process for each NT 0 How Gproteincoupledreceptors work 1 2 3 4 5 6 Heterotrimeric Gprotein has three subunits Molecule bonds With receptor Gprotein converts GDP to GTP and becomes activated 0t subunit with GTP molecule separates from B and y subunits and receptor changes in voltage are created sometimes by ion channels exact mechanism depends on type of effectors present in cell 0t hydrolyzes GTP back to GDP and reassociates With 3 and y subunits and receptor 0 Dendrites and Soma o Dendrites and soma continuously receive signals from presynaptic nerve terminals 0 Signals cause EPSPs and IPSPs of various magnitudes o Synaptic integration I EPSPs and IPSPs are summed together and either reach threshold to spark an action potential or not Chapter 8 The Central Nervous System 0 Anatomy of the CNS 0 Seven major divisions Brain tem o m 4 a l Cerebrum 0 Cerebral cortex 0 Basal ganglia o Hippocampus o amygdala 2 Diencephalon o Thalamus o hypothalamus Midbrain Cerebellum Pons Medulla oblongata 7 Spinal cord 0 Other terminology I Cavities filled with cerebrospinal uid CSF 0 Ventricles in brain Regions of the Brain gt Forebrain 3 Midbrain Hindbrain 0 Central canal in spinal cord I Gray matter 0 Bundles of nuclei I White matter 0 Tracts bundles of axons 0 Studying the intact brain 0 EEG electroencephalography I Commonly for studying sleep CT computerized tomography I static PET positron emission tomography I dynamic monitors changes MRI magnetic resonance imaging I static fMRI functional MRI I dynamic monitors changes 0 Cerebrum o Involved in higher brain functions 0 Outer layer of gray matter 0 Inner white matter 0 Corpus callosum Major tract of the CNS Connects left and right hemispheres o Cerebral cortex Gyrus peak Sulcus valley Four lobes o Frontal o Parietal 0 Occipital 0 Temporal o Insular cortexlobe sometimes included as fifth lobe intersection of frontal parietal and temporal lobes can t be seen from surface of cortex involved in limbic system Lateral sulcus o Divider between temporal lobe and parietal and frontal lobes Central sulcus o Divider between frontal and parietal lobes Longitudinal fissure o Divider between left and right hemispheres 0 Deepest of all sulci Hemispheres 0 Left and right separated by longitudinal fissure 0 Decussation crossing over of fibers 0 Either occurs at level of spinal cord or medulla o 90 of fibers are contralateral cross over from one side of body to the other 0 10 are ipsilateral and do not 0 Left hemisphere generally controls right side of body and vice versa 0 Cerebral lateralization o Partitioning of functionality between hemispheres 0 Ex left handles language and right handles spatial awareness Broca s area 0 Responsible for physical production of speech 0 Loop of communication with Wemicke s area general interpretive area Precentral gyrus 0 Primary motor cortex Postcentral gyrus 0 Primary somatosensory cortex Unequal distribution of innervation o Innervation neurons reaching out and synapsing onto other neurons or motor cells in a certain part of the body o More cells in the cortex dedicated to receivinginterpretingcontrolling signals to some parts of body than others 0 More area in cortex for face and hands fine motor control than kneecap or lower leg gross movement 0 Subcortical regions I Basal ganglia 0 Control of voluntary movement I Hippocampus 0 Learning and memory I Amygdala 0 Important in limbic system emotion 0 Memory 0 Diencephalon o Thalamus I relay center for ascending somatosensory information 0 Numerous connections with other brain structures I Part of system that regulates voluntary movement 0 Hypothalamus I Master regulator of autonomic nervous system ANS branch of PNS in uencing internal organs and endocrine system I Regulation of essential behaviors breathing body temperature growth 0 Midbrain 0 Important in motor control 0 Dopaminergic projection pathways I Neuronal cell bodies that project to other parts of brain and release dopamine from nerve terminals I Nigrostriatal system 0 Projects to basal ganglia 0 Motor control I Mesolimbic system 0 Projects to different part of basal ganglia and prefrontal cortex 0 Addictionreward behaviors 0 Cerebellum O O O O O Often called little brain Contains more than half of all neurons in the brain Maj or input center Involved in higher cognitive functions particularly motor systems and motor based learning Regions I Cerebellar cortex 0 Three layers 0 Five neuron types 0 Four types of interneurons o Purkinje cells projection cells of cerebellum I Inhibitory release GABA I Projection cells carry signals much further than interneurons to other parts of brain 0 Internal White matter 0 Three nuclei at center 0 Project up to frontal cortex to regulate motor control 0 Pons and Medulla o Pons I Ventral stomach side nuclei 0 Relay motor and somatosensory information from cerebral cortex to cerebellum I Dorsal backside nuclei 0 Involved in respiration sleep taste 0 Medulla oblongata also simply medulla I Vital center nuclei 0 Cardiovascular regulation I Decussation crossing over of many tracts here 0 Reticular formation I Long series of neurons running the length of pons and medulla I Regulate sleep and body clock 0 Spinal cord 0 Gray matter at core I Two dorsal horns o All afferent neurons sensory information enter here I Two ventral horns o All efferent neurons motor information exits here 0 Surrounding White matter funiculi I Funiculi bundles of ascending and descending tracts o Ascending tracts I Somatosensory information from PNS to CNS I Medial lemniscal tract 0 Touch receptors and proprioceptors information about muscles tendons joints 0 Crossover at medulla I Lateral spinothalamic tract 0 Pain and temperature reception 0 Crossover at spinal cord I Both tracts go to thalamus Where thirdorder neurons take information to postcentral gyrus o Descending tracts I Motor output from CNS to PNS I No relay centers I Corticospinal tract aka pyramidal tract 0 Cell bodies originate in precentral gyrus 0 Most axons Will crossover at medulla 0 Connects to muscles I Extrapyramidal tract 0 Part of motor control overlay by thalamus cerebellum and basal ganglia 0 Functions of the CNS 0 Learning and memory I Synaptic plasticity 0 Molecular mechanism for learning and memory 0 Synapses are able to change based on experiences 0 Longterm potentiation LTP 0 Strengthening of neuronal connections I Consolidation 0 Changing memory from shortterm to longterm I Categorizing memories by type 0 Explicit or declarative o Formed in hippocampus o Rote memory facts and experiences 0 Implicit or nondeclarative o Formed by cerebellum and extrapyramidal tract 0 Skillsbased memory how to perform particular actiVities I Categorizing by endurance of memories 0 Shortterm early LTP 0 Seconds to hours 0 No new protein synthesis in synapse I Not engaging nucleusregulation of genes 0 Longterm late LTP 0 Days to years 0 New protein synthesis in synapse I Engages nucleusregulation of genes 0 Formation of any memory considered a stage of LTP