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This 33 page Class Notes was uploaded by Maddie Rapp on Thursday October 8, 2015. The Class Notes belongs to PSYC2005 at The University of Cincinnati taught by Dr. Carol Wissman in Fall 2015. Since its upload, it has received 10 views. For similar materials see Child and Adolescent Development in Psychlogy at The University of Cincinnati.
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Date Created: 10/08/15
SodiumPotassium Sodium Channel Pump Sodium Ions i E t II C Q Q Q C xaceuar Action Potentials m We Membrane W W 39 U l C Intriacelular Potassium Ions Potassium Channel Neurons maintain different concentrations of certain ions across their cell membranes Concentration Gradient Neurons pump out positively charged sodium ions and they pump in positively charged potassium ions Therefore there is a high concentration of sodium ions present outside the neuron and a high concentration of potassium ions inside The neuronal membrane also contains specialized proteins called channels which form pores in the membrane that are selectively permeable to particular ions Sodium channels allow sodium ions through the membrane while potassium channels allow potassium ions through Resting Potential Under resting conditions the potassium channel is more permeable to potassium ions than the sodium channel is to sodium ions So there is a slow outward leak of potassium ions that is larger than the inward leak of sodium ions This means that the membrane has a charge on the inside that is negative relative to the outside as more positively charged ions ow out of the neuron than ow in The membrane is polarized Sodium channel quot V Open Fiefractory Reset r gt A u i j sodiqmionsremera 40 Na chewy become refractory no more Na enters cell K continues to leave cell causes membrane potential to return to resting level K channels open K begins to leave cell Na channels open Na begins to enter cell it f V Threshold of I Extra K outside excitation diffuses away Membrane potential mV K channels close Na channels reset Action Potential There is a pressure for the sodium ions to enter the neuron but they are prevented from doing so by the membrane and the pumping mechanisms that remove any ions that manage to get in However if the sodium channels are opened positively charged sodium ions ood into the neuron making the inside of the cell momentarily positively charged the cell is said to be depolarized This has the effect of opening the potassium channels allowing potassium ions to leave the cell Thus there is rst an in ux of sodium ions leading to massive depolarization followed by a rapid ef uX of potassium ions from the neuron leading to repolarization Excess ions are subsequently pumped inout of the neuron This transient switch in membrane potential is the action potential The cycle of depolarization and repolarization is extremely rapid taking only about 2 milliseconds 0002 seconds and thus allows neurons to re action potentials in rapid bursts a common feature in neuronal communication Na channels become refractory no more Na enters cell 8 K continues to 1 0 leave cell 5 4 causes membrane K channels 93 potential to return 8 Open39 K to restin level 0 begins to leave 9 ES cell 0 E 4 Na channels 2 open Na begins to enter cell I K channels close f I Na channels reset 7O J Extra K outside diffuses away Threshold of excitation How does the action potential propagate along the axon The sodium channels in the neuronal membrane are opened in response to a small depolarization of the membrane potential So When an action potential depolarizes the membrane the leading edge activates other adjacent sodium channels A wave of depolarization spreads from the point of initiation Action potentials move in one direction This is achieved because the sodium channels have a refractory period following activation during Which they cannot open again This ensures that the action potential is propagated in a speci c direction along the axon B propagation Na channels closed inactivated open closed 1 A Q r o o 0 a c Q membrane repolarized depolarized resting axon plasma membrane propagation Na channels closed inactivated open closed membrane repolarized depolarized resting axon cytosol Figure 1238 Essential Cell Biology 219 2004 Garland Science The speed of propagation is related to the size of the axon The speed of action potential propagation is usually directly related to the size of the axon Big axons result in fast transmission rates For example the squid has an axon nearly 1 mm in diameter that initiates a rapid escape re ex Increasing the size of the axon retains more of the sodium ions that form the internal depolarization wave inside the axon If we had to have axons the size of the squid giant axon in our brains We would have HUGE heads therefore The answer is to insulate the axonal membrane to prevent the dissipation of the internal depolarization in small axons myelin Remember Myelin 5 f Myelin is the fatty membranes of cells called Oligondendroglia in the CNS and Schwann Cells in the PNS that wraps around the axon and To rminal buttons 39I 7 II 399 Cell nucleus 41 new acts as an insulator The sodium and potassium ion 0 quot may channels pumps etc associated with action Axon MYe39m potential propagation are concentrated at sites 739 between blocks of myelin called the Nodes of RanVier This myelin sheath allows the action potential to jump from one node to another greatly increasing the rate of transmission Myelin sheath Synapse axon synaptic vesicles synapse neurotransmitte 39 m receptor When the action potential reaches the terminal buttons the depolarization causes voltagedependent calcium Ca2 channels on the presynaptic membrane to open and allows Ca2 to enter into the cell Ca2 binds with the membrane of the synaptic vesicles which causes the vesicles to break and release the neurotransmitter into the synaptic cleft dendrites Synapse axon synaptic vesicles synapse 39 d 6 11391 Q 39 r J Jquot 1 l 3 nourotransmitto quot quot receptor dondritos Charles Sherrington neuron neuron communication is different than that along the axon Neurons communicate at structures called synapses in a process called synaptic transmission The synapse consists of the two neurons one of which is sending information to the other The sending neuron is known as the presynaptic neuron i e before the synapse while the receiving neuron is known as the post synaptic neuron ie after the synapse Now although the ow of information around the brain is achieved by electrical activity communication between neurons is a chemical process When an action potential reaches a synapse pores in the cell membrane are opened allowing an in ux of calcium ions positively charged calcium atoms into the pre synaptic terminal This causes a small vesicle of a chemical neurotransmitter to be released into a small gap between the two cells known as the synaptic cleft The neurotransmitter diffuses across the synaptic cleft and interacts with specialized proteins called receptors that are embedded in the post synaptic membrane Synaptic Events Synthesis neurotransmitter and vesicles are synthesized in cell body Transport neurotransmitter transported down axon to terminal Action potential travels down axon and enables calcium to enter the cell and release neurotransmitter Binding Neurotransmitter travels through synaptic cleft and binds to postsynaptic receptor Seperaiton Neurotransmitter separates from receptor Reuptake Neurotransmitter is taken up by presynaptic cell for recycling Postsynaptic signaling postsynaptic cell releases retrograde transmitters that signal the presynaptic cell to sloW release Autoreceptors negative feedback sites respond to postsynaptic signaling or presynaptic cell s own neurotransmitter Synapse axon synaptic vesicles synapse neurotransmitte 39 receptor dendrites Plasticity The phrase 39synaptic transmission is plastic39 means that the post synaptic response to the release of neurotransmitter is not necessarily always the same For example the post synaptic response may be made stronger or weaker for a short whileor for a long time The ability for something to change is termed plasticity and plasticity at synapses is termed synaptic plasticity The brain is plastic throughout life it is constantly changing The ability to learn and form memories comes about because of the ability of neurons to change the way in which they communicate with each other through synaptic plasticity One of the greatest challenges in neuroscience is to determine how synaptic plasticity and learning and memory are linked Such insights are essential in order to understand the nature of diseases that affect memory systems such as Alzheimer39s disease and dementias In addition to roles in learning synaptic plasticity is crucial for the physical building of our brains during development and throughout the rest of our lives The circuits in our brains that allow us to eXperience the world via our senses to move and think are built through a process of synapse formation an removal Synapses that are active and actively changing are kept the rest are pruned The neuronal circuits needed to move the appropriate muscles that allow us to walk and talk are created in infancy through use to become permanent features of our brains However if those circuits are damaged through a stroke or instance they can be re built through a process of learning especially in children demonstrating the amazing plastic abilities of the brain Anatomy of the nervous system Terminology v 4 I quot K quot Dorsal towards the top it xi I m a b Ventral toward the stomach superordorsal v coronal frontal r midsagittal 39 t39 d39 I t39 Anterior towards the front sec 39 quot g 3 me Ialsec Ion g 77 if posterior toward the back 239 I cf Medial towards the midline horizontal sec on inferior ventral leuu A IESJ 9 Lateral Toward the side I Anatomy of the nervous system Coronal Plane More terms Horizontal view separate top from bottom Sagittal viewzseparate side from side Coronal viewSeparate front from back Midsagigal Plane Anatomy of the nervous system Even More terms Gyrus protuberance on surface of brain Sulcus fold or grooves that seperates one gyrus from another ssure long deep sulcus Lateral Sylvian fissure Precentral gyrus Central sulcus Postcentral gyrus Superior temporal gyrus Entering dorsal Roots carry sensory Info 0 Exiting ventral roots Carry motor info 0 gray matter cell Bodies and dendrites 0 White matter Myelinated axons Spinal cord Intemeuron Central canal Dorsal root amass Dorsal column Cortloosplnal mm W tract Cell body of Rubrosplnal sensory neuron quot991 Spinothaemlc tract Dendrite of sensory neuron White matter Grey matter Cell body 0 motor neuron Receptor Ventral root Axon of motor neuron Synaptlc knobs Effector muscle Sympathetic nervous system and Parasympathetic nervous system Symathetic activates the quot ght or flight response ll breathing and heart rate lower digestive activity main neurotransmitter norepinephrine Getting body ready for a situation STRESS Parasympathetic facilitates nonemergency responses by organs lower breathing and hear rate l digestive activity main nerotransmitter Acetylcholine Pzasyrnpathetic 3mm mmc c Consulcts Dilatos pupil pupil Stimulatesquot 39 quotV No effect on tear glands tear glands Weak stimulation Strong stimulation 1 0g sauivary now oi salivary flow I inhibits heart gx g heart dilath 39 artetioies l artonolos r I Dilates 30mm 39 bronchi mnc I i 344 Inhibits stomach Stinulates stomach 39 I c a mom quot9 motility and secretion 3 388632082 Inhibits stimulates pancreas o 39 and adrenals Strnulates g 39 I 39 Inhibits quot 0 39 a I intestinal 4 motility Contracts bladder Mal can quot Relaxas bladdec Stimulates Stimulates emotion ejaculation prosencephalon is made up of the diencephalon and telencephalon and include the following structures Diencephalon thalamus hypothalamus TEIE nCe pha IOh cerebral cortex hippocampus and basal ganglia mesencephalon includes tectum tegmentum sup Colliculus inf Colliculus substrantia nigra metencephalonpons and cerebellum and mvelencephalon medulla Major divisions of the brain Hindbrain Part of the Hindbrain IVIedulla Controls vital re exes breathing heart ratevomiting sneezing coughing and salivation through the cranial nerves Cranial Nerves Sensory Motor l l IOIfaCtOW Id IIIOculomOf39or I ptquot IVTrochlear v VI Abducens 2quot V rug emlna I 5 I f VII Fa cia 4VIII Vestibuloco chlear quot XI Spinal Cranial Nerve I II III IV V VI VII VIII IX XI XII Olfactory Optic Oculomotor Trochlear Trigeminal Abducens Facial Vestibulocochlear Glossopharyngeal Vagus Accessory Ilypogiossal Cranial Nerves General Function Sense of Smell Sight Eye Movement Eye Movement Face sensory motor Eye Movement Face expression and sensory Hearing and Balance Tongue and Throat motor and sensory Parasympathetic Head neck shoulder movement S swallowing Speech Chewing and Swallowing Cranial Exit Opening Cribriform Plate of the Ethmoid Optic Foramen Superior Orbital Fissure Superior Orbital Fissure Superior Orbital Fissure Superior Orbital Fissure Styiomastoid Foramen Internal Acoustic Meatus Jugular Foramen Jugular Foramen Jugular Foramen Hypoglossal Canal Hindbrain continued Pons sleepwake cycle Cerebellum motor function and coordination Pons Roticular formation Midbrain Superior colliculus visual orientation Inferior colliculuszauditory orientation Somatosensory Cortex Cerebmm 1 Midbrain 4 SuperIor Colliculus lt InferIor Colliculus VIII Cranial Nerve if I 4 d 397 MedulIa v a I J Cochlear Nucleus Midbrain continued Substantia nigra motor function Cut section of the midbrain where a portion of the substantia nigra is visible Substantlia nigra Diminished substgntia m ra as seen In Par quot150er disease Forebrain Diencephalon Thalamuszrelay station most sensory info goes rst to the thalamus Hypothalumus motivated behaviors feeding drinking Temperature regulation sexual behavior aggression 4UOG menluj39alar smdlu uumun wenovary q A IJ n s v0 ll lcl39ll l pituitary gland Forebrain Telencephalon Basal Ganglia initiation of movement Basal Forebrain arousal and attention Hippocampus learning and memory Primary motor cortex Prolrontal ObO Primary somatosensof Y cortex Caudate nucleus Putamen Globus pallldus Subthalamus vemr39al Nrgrostriatal bundle 2332 Midb39al dopaminergic Thalamus Venlrolateral l corpu allowm I nuc39eus Auditory area S b l t39 l Hippocampus u s an laquot nigra F0 b n continued Limbic System collection of structures motivation and emotions eating and drinking anxiety aggression sexual activity Structures from both telencephalon and diencephalon olfactory bulb hypothalamus hippocampus amygdala and cingulate gyrus Ventricles Cerebralspinal uid Clear uid similar to blood plasma Cushions the brain Containshormones and nutrition for brain Central canal spinal cord Lateral ventricles Third ventricle ventricle Fourth ventricle Lateral Ventricles o 339 s Intewentrlcular I Foramen Third Ve ntricle quotits Ce 399 b fa I S t 5 539 Founh Ve ntricle Meninges Membranes that surround the brain and spinal cord 1Sku 2Dura mater 3Arachnoid 4Pia mater The meninges are Dura mater 2 layers the membranes Arachnoid covering the brain Pi and spinal cord a mater I Cerebral Cortex Neocortex Cells in the cortex are gray matter their axonal projections are white matter Neurons in each hemisphere communicate through bundles Axons known as the Corpus Caollosum and Antierior Commissure V Plate 14 Neocortex in Mammalian Brains Human Neocortex consists of multiple areas The neocortex consists of various quotsubunitsquot that are associated with different functions 80 mato SGHSO ry Frontal a 39 Parietal lobe aUd ry Temporal lobe cerebellum Connectivity makes functional differences The function of the nervous system depends on connectivity For example the visual area can perform visual function because it receives visual information from the visual organ the eye Similary the auditory area receives auditory information from the ear and the somatosensory area receives body sensations Such area specific connectivity forms the basis of functional localization somatosensory visual auditory Organization of the Cortex 6 distinct laminae layers Laminea vary in thickness depending on area Example Motor cortex has a very thick layer 5 because long axons are sent to the spinal cord whereas layer 4 is basically absent from motor cortex because that layer receives axons from sensory nuclei in the thalumus PiomfuGdgi cin Nian quotwagen sm P 39 v b t P S f l I 39 39 39 gt 39 39 N 39 39 quot 5 a I a 3 39 If 39 quot39 o v39 quot 4 t 5quot 39y quot 3 39 rizfnnvm a rilt 39Ir A 0 39 q39lquot39 39 39I39 l wl Int 2 m v21 ms II N If l o J 23quot 7 3 g tff 39 3539 3 LI g 39 ID II 139 1 ML39 l39 2 M 31 Vb 3 fur 39 r 3 Visual l my VI WWW 9A393 j li assocuatlon L at1 motor Frontal executive functions Planning and switching strategy Parietal Touch Primary Somatosensory Cortex Occipital lobezvision Temporal Hearing The Lobes Primary Central motor SUICUS Primary cortex so ma tose nsory Frontal o rtex i l 39l f 53515 n39 I quot quot3939 quot3531 Occipital Olfactory lobe quot 39A135393939 1I39D bu39b Temporal quot 39 39 Cerebellum lobe I u u t aquot 39 I A I 39 39 I I 2 39I P q39i39ff39i aI v on Aquot vt vquotquot quotquot Spinal cord Q Q C gt4 Motor Cortex The Homunculus Somatosensory Map Homunculus d TowWWW I Iq I Lateral 39 Medial 7 quot Somatosensory cortex