Chapter 2 Part 1-combined PDF

WHAT CELLS MAKE UP OUR NERVOUS SYSTEM? Chapter 2 – Part I WHAT CELLS MAKE UP OUR NERVOUS SYSTEM? Chapter 2 – Part I WHAT CELLS MAKE UP OUR NERVOUS SYSTEM? Chapter 2 – Part I  QUIZZES (20% OF FINAL GRADE)...

WHAT CELLS MAKE UP OUR NERVOUS SYSTEM? Chapter 2 – Part I WHAT CELLS MAKE UP OUR NERVOUS SYSTEM? Chapter 2 – Part I WHAT CELLS MAKE UP OUR NERVOUS SYSTEM? Chapter 2 – Part I  QUIZZES (20% OF FINAL GRADE) - ▪ Quiz 1 opens today, closes 9/8. Covers today’s material only ▪ Highest 8 quiz scores will count towards your final grade  controls our internal organs 8 WHAT IS THE NERVOUS SYSTEM? PVS-CNS - Brain ▪ Complex & highly organized body system: Receives information from the world around us PNS ↓ Transmits the information through the spinal CNS cord/brain extreme amount of of organization the nervous system ↓ Processes the information in the brain generates motor command ↓ Directs our body’s reaction to the world back out to PNS & Controls our internal functions  HOW DOES THE NERVOUS SYSTEM CONTROL BEHAVIOR? takes external world in fo ↑ to brain. neurons process signol Neuron 1 ▪ 2 types of cells – neurons & glia send it back out and Synapses → Neurons transmit information → Glia act as supporting cells ↳ Support neuron al metabolism protect help , ▪ Neurons communicate with each maintains activity Neuron 2 other through L synapses Specialized structure where mode projections are very close not but exectly touching ▪ Neurons are organized in a precise order to form a circuit - how information travel I through multiple neurons  All behavior arises from neurons – even if they are few in number True of humans + animals not everything has neurons SIMPLE TO COMPLICATED NERVOUS SYSTEMS  ROUNDWORM (C. ELEGANS) Sensory ?302 Neurons ▪ 302 Neurons → Sensory neurons (receive input) ↳ sense water , small , ph → Motor neurons (move body) carry out information → Interneurons: neurons that Interneurons process information between very simplistic nervou system no the broin ; body neurons distributed throughout sensory & motor neurons Depends combine information on internal conditions process information & can sense temp smell , ph make decision and eX : predator near w h e r if thirsty may ignore pred. , C Ele from send info to motor neurons food is.... Le towards ▪ Arranged in simple circuits that can or away can more if well fed will avoid pred. effectively things smells reactions through produce simple behavior Can be taught ↳ Smells ex : can have pepperment meaning small = food nearby Motor Neurons ROUNDWORM (C. ELEGANS) most congregated ganglion(nucleus (Not suphisticated enoughfo toward head be abrein D a cellbodya neurons This movie was generated by Chris Grove. HTTPS://DOI.ORG/10.7554/ELIFE.17686.020  BRAIN NO SEA SLUG (APLYSIA CALIFORNICA) one of the first used for learning and memory ▪ ~ ?1818,000 , 000 Neurons → Sensory (receive same S input) elegant → Motor (move body) as c. → Interneurons Where it draws in water ▪ Gill and siphon withdrawal reflex processing ▪ Eric Kandel won the Nobel will retreat Gill Prize in 2000 based on information from interneuron  RAT (RATTUS NORVEGICUS) ↳ mammals ~50 ▪? 50million ~ million neurons · have a brain ▪ Nervous system now has many parts same S→ Central nervous system (brain & spinal cord) &→ Peripheral nervous system: as humon → Sympathetic nervous system fight / flight · → Parasympathetic nervous system a digest rest + → Enteric nervous system digestive system ▪ More neurons → more complex circuits → more complex functions & · nervous system organization very similar to humans  HUMAN (HOMO SAPIENS) Sensory Motor Neurons Neurons categorization und based on function , location ▪ ?~8080billion ~ billion neurons interneurons ↳ can have subcategories ▪ More neurons, more discrete brains regions, more complex circuits ▪ Capable of abilities no other species on earth  SIMILARITIES ▪ Neurons are the building blocks of the nervous system and the element of processing information decisions ↳ even wh few neurons can process and more ▪ Neurons are connected to each other via synapses to form circuits in all species including C elegans. ▪ Certain aspects of the nervous system are shared across all species (e.g. sensory neurons) and especially closely related species (e.g. brain and spinal cord in mammals) - only humans and rodents  CLASS QUESTION True or False? In all animals, circuits formed by neurons drive behavior Answer: True ? TRUE NOT TRUE of PLANTS , Viruses NEURONS  THE FIRST CELLULAR NEUROANATOMISTS - NOBEL PRIZE IN 1906 Camillo Golgi processesofneuroanother # ▪ Staining technique to visualize entire neuron ▪ Thought neurons were continuous like tubing Soma = cell body Neurites = axons & dendrites  THE FIRST CELLULAR NEUROANATOMISTS - NOBEL PRIZE IN 1906 Camillo Golgi Santiago Ramon y Cajal ▪ Staining technique to ▪ Used Golgi’s method visualize entire neuron ▪ Thought neurons ▪ Thought neurons came close to each were continuous like other, but did not tubing (NOT TRUE) touch (TRUE) & ▪ Neuron Doctrine: - each neuron is an independent unit - information must be transmitted across gaps between neurons We now know as synopse GOLGI STAINING REVEALS VARIETY OF NEURON SHAPES different neuron shopes Notoll look the some All nove cell bodies and neurites but in diff potterns  NEURONS ARE POLARIZED one flow can't even though go have they backwards elaborate polorized/ structures directiooil they nove to neurons the some basic structure No spine  DENDRITES AND SPINES INPUT ZONE receive informations to get info from & ↑ ▪ Dendrites = branches neurons many numerous branches Dendrites every dendrite ▪ Spines = mushroom-shaped has many spines Gunere protrusions from dendrites synopses form ▪ A neuron has many dendrites/ spines most input directly Spines are specialized can come on to spine but input and create greeter connections dendrite also through ▪ Input zone - where information/ signals are received ▪ Dendrites/spines from one neuron receive chemical signals from other neurons Spines  SOMA ▪ Soma = cell body Soma ▪ Integration zone of all the signals various dendrites from ▪ Mitochondria – produce energy ▪ Cell nucleus – contains genetic instructions ▪ Ribosomes – translate genetic instructions into proteins  AXON HILLOCK at end of Soma ▪ Also called axon initial segment ↑ decision location send info whether to to next neuron or not ▪ Final location where integration occurs and the decision to generate an electrical communication signal is Axon hillock made if decision is to send signol - electrical will be sent ▪ Most neurons have one axon hillock ↳ only can make quick can be one decision of a yes , No , yes, no time but can't say at some time Y/N  AXON electrical a close as signal/Action possible potential gets to next neuron conducted down axon ▪ Conduction zone ▪ Most neurons have one axon Axon ▪ Role #1: Conduct electrical signal on the cell membrane away from cell body to next neuron  AXON protein transport ▪ Role #2: Transport 9 material between electrical signal one action potential only travele anterograde soma and axon direction only direction terminal back forth + eX : proteins ; was te if protein misforms ▪ Anterograde S terminal away from = to axon cell body if axon termine the body damaged communicateis to needs body there rode · retrog tocell -ex of domage Transport ▪ Retrograde = from axon From end of terminal toward axon body cell AXON Axon  Synapses AXON TERMINAL release info to cross gop in synopse to dendritic Spines of the second neuron Neuron 1 ▪ Output zone ▪ Axon terminals from one neuron axomind releases chemical signals onto many other neurons Neuron 2 signal electrica to causes pockets chemical releasein to gop Axon ↓ terminals electricol signal converted to chemied signal at oxon terminal  (2) dendridic Spine SYNAPSE connects to axon terminal (1) as chemical signol Pre-synaptic axon terminal axon termine con also be Synaptic colled pre-synoptic cleft: where chemical terminal dendritiv spine = post-synoplic signal terminal When chemical signal released reaches dendritic spine flow across gop into it converte book Post-synaptic signal electrical by of dendritic binding proteins spine dendritic spine INFORMATION FLOWS THROUGH A NEURON new electrice signol generated ▪ Electrical signal in neuron at hillock ▪ Chemical signal between neurons ↳ does not enter the cell releases onto a lot of information neurons  Each neuron may receive and make thousands to tens of thousands of synapses to proportional of neurons species amount neuron constantlyot work  CLASS QUESTION · Where is the neuron's output zone? Answer: F?F terminal the axon GLIA (GLIAL CELLS)  GLIAL CELLS SUPPORT AND ENHANCE NEURAL ACTIVITY Oligodendrocyte/ Astrocyte Schwann cell Neuron ▪ Types of glial cells → Astrocytes → Oligodendrocytes/ Schwann cells → Microglial cells Microglial Cell ASTROCYTES - STAR SHAPED CELLS  ASTROCYTES tripartite - ▪ Monitor & support the buffering Pre-synaptic Post-synaptic metabolic and biochemical the neuron axon dendritic terminal spine needs of neurons Pre-synaptic axon terminal ▪ Regulate synaptic signaling as part of the “tripartite pre/post synapse” / Astro wrap around synopse monitor Astrocyte chemical Post-synaptic signols dendritic spine Astrocyte  ASTROCYTES pothogen preventeentering from ▪ Help form the blood brain barrier by sitting between blood capillaries and neurons only things that een cross such as nutrients , oxygen con cross ▪ React to brain injury (repair and scarring) form will scor to blood loss prevent in brein  OLIGODENDROCYTES AND SCHWANN CELLS & secrete substance w rops that a xo n out from coming electried current insulation & prevents ~ allows current to lost from point A - B - ▪ Insulate axons by wrapping myelin Neuron axon around them – white matter Myelin ▪ Oligodendrocytes are in the central same S nervous system (brain and spinal cord) & major function ▪ Schwann cells are in the peripheral nervous system Oligodendrocyte/ Schwann cell OLIGODENDROCYTES Nodes of Ranvier = gaps in myelin sheath · doesn't evenly coot exon  will physically MICROGLIA site of injury ; ↓ ↳ constantly monitoring release chemicals to attract other (loca area microglia ▪ Brain immune cell de of threat look for any sign migrote Car brain trigger microglia throughout immune ▪ Monitor local environment for response threat or injury ▪ Migrate to injury site to remove I debris/dead cells cord · brain + Spinal immune have separate then rest of system body  CLASS QUESTION Which of the following myelinate neurons in the Central Nervous System? A. Schwann cells if said PNS B. Microglia C. Oligodendrocytes D. Astrocytes Answer: C?  SUMMARY ▪ Neurons o Polarized o Dendrites, soma, axon, axon hillock, axon terminals o Synapses ▪ Glia o Astrocytes o Myelinating cells (Oligodendrocytes and Schwann cells) o Microglia  SUMMARY ▪ Neurons o Polarized o Dendrites, soma, axon, axon hillock, axon terminals o Synapses ▪ Glia o Astrocytes o Myelinating cells (Oligodendrocytes and Schwann cells) o Microglia HOW IS OUR NERVOUS SYSTEM ORGANIZED? Chapter 2 – Part II HOW IS OUR NERVOUS SYSTEM ORGANIZED? Chapter 2 – Part II  NERVOUS SYSTEM ANATOMY ▪ The nervous system is highly organized ▪ This is true at all levels – gross anatomy (that which you can see by eye) to the microscopic level ▪ The “parts” are important because structure = function DIRECTIONAL AND PLANER LABELS front back top bottom  CENTRAL VS. PERIPHERAL NERVOUS SYSTEM cell body is defined on where the ▪ Central nervous system (CNS) – brain and the spinal cord ↳ if cell body in the spinel brain ▪ Peripheral nervous system (PNS) – all parts of the nervous system outside brain and spinal cord ↳ if cell body not in spine cord/brein PERIPHERAL NERVOUS SYSTEM (PNS)  DIVISIONS OF PNS ▪ Nerves = bundles of axons in PNS ▪ Ganglia = clusters of neuron cell bodies distributed throughout body (near spine or near organs) ▪ PNS divided into: Voluntary → Somatic nervous system (nerves between movement - brain/spinal cord and skeletal muscles/sensory between organs) → Autonomic nervous system (nerves - broinspira cova - internal orgens between brain/spinal and internal organs)  SOMATIC NERVOUS SYSTEM ▪ Nerves send information from sense organs to the brain/spinal cord ▪ Nerves from brain/spinal cord to the skeletal muscles → voluntary movements ·  SOMATIC NERVOUS SYSTEM ▪ Within a nerve, different axons carry sensory and motor information → spinal cord they travel separately in roots neurons can only send electricd info in one direction Dorsal root = de sensory nerves if we need info to flow book a single nerve will nore two neurons in different directions Ventral root = motor nerves out the function carry  AUTONOMIC NERVOUS SYSTEM ▪ Involuntary movements ↳ digestion , breathing , Blood pressure ▪ Sympathetic (fight or flight) → Norepinephrine & key neurotransmitter ▪ Parasympathetic (relax) → Acetylcholine *** Sympath and Parasympath often oppose each other *** ▪ Enteric (gut/digestive control) information bidirectional pathway  CLASS QUESTION Which nervous system gives rise to a flight-or-fight response? A. Parasympathetic B. Sympathetic Answer: B? CENTRAL NERVOUS SYSTEM  CENTRAL NERVOUS SYSTEM ▪ Responsible for: → Senses: vision vs. sight, etc… but CNs allows us (PUs) not responsible for being able to see to process what we see for interpretation → Initiating - movement of your muscles vs. moving *** how is this different from PNS? *** → Higher-order behavior: attention, cognition, perception, thought, affect, mood decision making , emotions → Automatic life-essential function: breathing, hunger, thermoregulation, circadian rhythm  BRAIN AND THE SPINAL CORD SPINAL CORD BRAIN ▪ Cerebral cortex ▪ Corpus callosum ▪ Cervical ▪ Limbic system ▪ Thoracic ▪ Basal Ganglia ▪ Lumbar ▪ Thalamus ▪ Sacral ▪ Hypothalamus ▪ Coccygeal ▪ Brain stem (midbrain, pons, medulla) ▪ Cerebellum ▪ Cervical innervates nerves in the SPINAL CORD → Neck part of body the they ▪ 31 pairs of spinal nerves are in ▪ Thoracic → One nerve serves → Trunk left side of the body, the other the right ▪ Lumbar motor axons contains sensory + in each of the 31 pairs → Lower back ▪ Sacral → Pelvic ▪ Coccygeal control down to legs body → Tail bone  Bipolar SPINAL REFLEXES EX : poin stimula ▪ Dorsal root ganglion: - haveeites a reflex through spind Lord con bypass broin information → Bipolar neuron , pseudo-unipolar sensory information goes down exon cell body in dobel root → Information from skin enter here to broin genglion to spinal cord synepeeverneuron → Sensory - port of 7 PNS & sensory neuron goes to PRO in spinel cord interneuron ▪ Ventral root: → Cell bodies in ventral horn ↑ ↑ portor CNS → Send axon to effector bundled together as the nerve Chemical signal muscle to make it move released onto neuron → Motor THE BRAIN  SULCUS AND GYRUS ▪ Sulcus – (plural is sulci) – a groove in the cerebral cortex ▪ Gyrus – (plural is gyri) – matter between two grooves/wrinkles increases surface - ▪ Folding pattern is organized area = more spece for neurons We all have the exact some sulcus + gyros EVOLUTIONARY TRENDS dolphin broin ? more gyri I - ↑ sulci in then dolphins in humans ORGANIZATION OF THE BRAIN Brain regions do not generally function in isolation! Most brain regions have many functions!  CEREBRAL CORTEX COVERS MOST OF THE BRAIN outer covering of the brain - ▪ Cerebral cortex has 4 lobes: → Frontal lobe → Parietal lobe → Temporal lobe → Occipital lobe  SURFACE FEATURES IDENTIFY LOBES AND HEMISPHERES separates frontal from porietal lobe on both hemispheres separates frontel /tempora and temporal/parietal down center of the broin ANATOMY IN THE VENTRAL PART OF THE BRAIN Olfactory bulb Optic chiasm E occipital lobe ~ of part of cortex * motor control * Olfactory Optic nerve nerve  VIEW ALONG CORONAL PLANE: GRAY AND WHITE MATTER metter grey grey & motter D & white matter ▪ Gray matter = cell bodies and dendrites ▪ White matter = axons with white myelin sheath ~ insulated ↳ sending information from one port to another  VIEW ALONG THE SAGITTAL PLANE: AXON TRACTS ▪ Axons traveling together form a tract in the brain (vs. nerve in PNS) through information tracts from the broin one port of to another ▪ Brain regions communicate with each other via these tracts  CORPUS CALLOSUM of & not typical cluster neurons to information from L-R hemisphere white matter tract exchange major ▪ Corpus callosum – axon tract that joins the two hemispheres Corpus callosum Corpus callosum  CLASS QUESTION Grey matter is made up of? A. Myelinated axons white motter B. Cell bodies and dendrites Answer: B? CEREBRAL CORTEX  CEREBRAL CORTEX · ▪ Cerebral cortex = complex thought and function → Frontal lobe – movement, planning strategizing high-level cognition , new learning things → Parietal lobe – body’s feeling sensory info, touch pain , sensations * → Temporal lobe – hearing, smell → Occipital lobe – vision  CEREBRAL CORTEX each lobe contain ▪ Sensory cortex – processing 6 primory motor Somatosensory sensory input cortex ② & associative primary a D * sometosensory → Primary somatosensory Motor S ↳ associative ⑭ cortex re motor Q poin info e → Visual cortex sensory i Vision → Auditory cortex - would decision making , D planning , order higher thought j ▪ Motor cortex – generating motor responses → Primary motor cortex last place for primary Q Auditory the instructions in associative ↳ last place for processing of motor information ② broin theiraxons go down spind cord Visual ▪ Associative cortex · fine tune directly interests wh sensory ↓ rimery = information  HOMUNCULUS a mapped to the body ▪ Primary motor cortex (red) is in front of the con - Z central sulcus feel sensation but Cannot more gums ▪ Primary sensory cortex · > - When stimulated (blue) is behind the Pt moves that port ↳ when stimulated pt will central of body thatorea solcus feel sensation in central sulcus if you stimulate side of the Right broin the will react Left side  CEREBRAL CORTEX ▪ Associative cortex – integrate sensory inputs and help plan motor function → Prefrontal cortex Motor Somatosensory associative associative Prefrontal cortex Auditory associative Visual associative  SIX LAYERS OF THE CORTEX Skrl ▪ Different sub-regions, but similar structure (cytoarchitecture) ▪ Six layers: → Layers 3 & 5 contain pyramidal neurons * Not homogenous tissue cell bodies Some have movel less ▪ Apical (top) and basal (bottom) Center dendrites receive information Of brain ▪ Pyramidal neurons are projection cells > - long axons out of cortex cell sends information pyramidal =  CLASS QUESTION What color is the part of the brain that processes vision? ? yellow Answer: Yellow  SUBCORTICAL REGIONS AND NUCLEI Deeper than cerebral cortex know homes + functions Not location INTERNAL SYSTEMS AND SUBCORTICAL REGIONS  INTERNAL SYSTEMS AND SUBCORTICAL REGIONS ▪ Thalamus – sensory relay station info into broin primary cortex & most sensory will come poss through thalome > - ↳ routes info to the right place them absociated types of information from event to keep ↳ does not just sorts ; tags multiple one process ex : smell + sight ▪ Hypothalamus and pituitary gland – neurohormone center, biological rhythms, hunger/thirst, body temperature, sexual drive * important for hormone release  INTERNAL SYSTEMS AND SUBCORTICAL REGIONS * When things are more emotionally exciting = learned easier ▪ Limbic System: emotion and learning → Amygdala – center for negative emotion, fear, anxiety → Hippocampus – learning and memory formation for the act of learning → Cingulate gyrus – attention * What we're paying attention to  INTERNAL SYSTEMS AND SUBCORTICAL REGIONS ▪ Basal ganglia: motor control * associative → Caudate – habit formation motor · inioting sequence of movements of → Substantia nigra – neurons hobits that produce a neurotransmitter dopamine, Parkinson’s disease > - when in dopemine substantia dies nigra * DOPAMINE one of the only two regions to make dopomine BRAINSTEM  BRAINSTEM moving toward neckt Spina cord ▪ Midbrain → Visual and auditory information processing ▪ Pons → Motor control and sensory nuclei → Cranial nerves ▪ Medulla Connects to spind cord → Brain to spinal cord * most critical the Dort of broin * → Breathing and heart rate domoge to medulla negatively imports # → Cranial nerves survive  Didirectional CRANIAL NERVES eye movements + info about light Control pupil/len Pons 12 sets of cranial nerves Medulla headt face mostly control · CEREBELLUM  CEREBELLUM NOT port of cerebral cortex ▪ Fine motor control ↳ writing ▪ Gait, balance ↳ bike riding a ▪ Muscle coordination *imported function due to alcohol consumption  I CLASS QUESTION What brain region is important for fear? A. Hippocampus B. Amygdala C. Thalamus Answer: B?  SUMMARY ↑ · ▪ Directions and planes ▪ Central nervous system → Spinal cord circuit – reflexes ▪ Peripheral nervous system → Sulcus and gyrus → Somatic → White and grey matter → Autonomic – Sympathetic, → Cerebral cortex – Frontal, Parietal, Parasympathetic, Enteric Temporal, Occipital → Corpus callosum → Subcortical regions and nuclei → Brainstem → Cerebellum  SUMMARY ▪ Directions and planes ▪ Central nervous system → Spinal cord circuit – reflexes ▪ Peripheral nervous system → Sulcus and gyrus → Somatic → White and grey matter → Autonomic – Sympathetic, → Cerebral cortex – Frontal, Parietal, Parasympathetic, Enteric Temporal, Occipital → Corpus callosum → Subcortical regions and nuclei → Brainstem → Cerebellum  SUMMARY ▪ Directions and planes ▪ Central nervous system → Spinal cord circuit – reflexes ▪ Peripheral nervous system → Sulcus and gyrus → Somatic → White and grey matter → Autonomic – Sympathetic, → Cerebral cortex – Frontal, Parietal, Parasympathetic, Enteric Temporal, Occipital → Corpus callosum → Subcortical regions and nuclei → Brainstem → Cerebellum  NEUROPHYSIOLOGY study of chemical and electrical signals in neurons  INTRA-CELLULAR TRANSMISSION ▪ Intra-cellular communication: signals travel WITHIN cells/neurons ▪ Information is received – dendrites as soon as dendrite info touches it is converted into electrica signa ▪ Integrated and processed – cell body/axon hillock ▪ Transmitted/conducted – axon ▪ Action potential = rapid electrical signal that travels along the axon  INTER-CELLULAR TRANSMISSION Synapses ▪ Inter-cellular communication: signals travel BETWEEN cells/neurons ▪ A neurotransmitter is a chemical messenger between neurons → released at synapse I floot through to dendrites INTRA-CELLULAR COMMUNICATION: THE NEURON AT REST  NEURONS HAVE MEMBRANES both have water as their base ▪ Membrane = phospholipid bilayer ▪ Surrounded by fluid (mainly water) on both sides → intra-cellular fluid/cytosol and extra-cellular fluid MEMBRANE PROTEINS ARE EMBEDDED IN THE BILAYER memb assist in rane protein transport : or out as binding site  IONS ARE DISSOLVED IN THE INTRA/EXTRA-CELLULAR FLUID ▪ Ions are charged molecules (e.g. NaCl dissolves into Na+, Cl-) ▪ Cation = positive charge loss e- ▪ Anion = negative charge goin er ▪ When ions move across the membrane, can generate an electrical signal ▪ Ion channels & Ion Pumps can flow in ↳ requires a ions energy to either direction move in both wo energy direction  HOW DO IONS MOVE ACROSS THE MEMBRANE? ▪ 1. Diffusion – ions move from regions of high concentration to low concentration (DOWN the concentration gradient) off that particular neuron  ION CONCENTRATIONS IN NEURONS AT REST ▪ Higher concentration outside: * know numbers → Cations: Na+, Ca++ → Anion: Cl- ▪ Higher concentration inside: → Cations: K+ → Negatively charged proteins ▪ Selective ion channels · only allow specific ions to cross &  CLASS QUESTION At rest, the concentration of Na+ ions is _______ inside the neuron compared to outside the neuron A. Higher B. Lower C. The same Answer: B? HOW DO IONS MOVE ACROSS THE MEMBRANE? ▪ 2. Electrostatic pressure – ions move across an electric field because they are charged ▪ Membrane voltage differential → Inside of the cell is more negatively- charged than the space immediately outside the cell rest Diff. at / / L I -  HOW DO IONS MOVE ACROSS THE MEMBRANE? ▪ Opposite charges attract, like charges repel ▪ Selective ion channels: → Cations move into the cell C → Anions move out of the cell bC inside of cell more negative · /  ELECTROCHEMICAL GRADIENT ▪ Chemical driving force → concentration ▪ Electrical driving force → opposite charges attract ▪ These two forces can collaborate or oppose one another  ECF ICF & # E  D - W E electrica Forceona  & E C ↓ we don't know which would win wo equation  electrica gradient neurons generate specific HOW ARE THE ION CONCENTRATION GRADIENTS GENERATED/MAINTAINED? by using pumps to move ions against gredient * constantly working ▪ Sodium-Potassium pump I uses → “Pump” proteins expend energy energy 1 ATD to move ions against their gradient → Na+/K+- ATPase pump molecule used → Moves 3 Na+ ions out and 2 K+ ions in for every energy molecule if pump stopped working out the but ion channels stayed pump sodium closed ? cell would have is the inside of the n e u ron (? Why build up moving out (t) ions then It into the pump · more a re you moving in 700 muan chennek open I no pump cell Chemical I ↳ will go back to equilibrium gradient  MEMBRANE POTENTIAL IN NEURONS AT REST ▪ Resting membrane potential (RMP) Cell at rest no inputs → Rest/resting means in the absence of any other external input → -60 to -70 mV (more negative inside than outside) HOW IS THE RESTING MEMBRANE POTENTIAL GENERATED/MAINTAINED? ▪ K+ Channels At rest = always open: help maintain negative charge → open (K+ can flow in either direction) → allow positively-charged K+ ions to leave cell down concentration & potessium enonnel gradient → creates a negative charge inside cell allows K + to leave makes cell even D more negative h [k ] + HOW IS THE RESTING MEMBRANE POTENTIAL GENERATED/MAINTAINED? Eventually reach equilibrium: K ▪ - Kt out + in = chemical and electrical driving forces are equal, but opposite → -60 to -70 mV RMP · K+ channels should never be closed INTRA-CELLULAR COMMUNICATION: ACTION POTENTIALS  ACTION POTENTIALS ⑭ intra 60mV will - - switch - to(t) extra inside of ▪ Action potentials are brief (transient) membrane will become + 201 + 40 instantaneously then goes bock but large changes in the membrane down and jets more (1 to 801-9p then back to -60mV potential quick flip of potential membrane ▪ For an instant, the inside of the membrane becomes positively-charged inside of (t) then membrane very quickly book to c)  ACTION POTENTIALS ▪ Action potentials triggered in the axon hillock ▪ Conducted along the axon ↓ Heree of  Channels open/closing - HOW IS AN ACTION POTENTIAL GENERATED? ▪ Ion channels can open/close for many reasons: → a ligand/chemical can bind a receptor → temperature-sensitive → voltage-sensitive When sits membrane at + 20 mv channels may a time sensitivity open/close ▪ Ions flow into/out of cell, alters membrane potential ? actionsa→ anions flows into cell - hyperpolarization (cell becomes MORE negative) (-) ; hyperpolarization more two &→ cations flows out of cell - hyperpolarization hyper ? (t ; hyperpolorization more S→ anions flows out of cell - depolarization (cell becomes LESS negative) two action ? () ; depolarization more thercoua→ cations flows into cell - depolarization ? more (H) ; depolarization  all steps generated PARTS OF AN ACTION POTENTIAL in membrane hillock of exon ▪ Stimulus causes a small depolarization of the neuron to the Threshold (#1) voltage (-40 to -55 mV) → Action potential triggered if axon hillock decides yes cases → All-or-none small depolarization to the neurons threshold ▪ Depolarization (#2) is when the interior of the cell becomes positive ▪ Repolarization (#3) is when the membrane potential becomes negative V axon hillock decision / saying nu Stimulus  PARTS OF AN ACTION POTENTIAL ▪ Hyperpolarization (#4) is when the membrane potential undershoots the RMP → Refractory period – neuron cannot westepump generate another action potential ato HOW we + until it returns to RMP al ? D S tota ▪ Resting State (#5) is when the m membrane returns to RMP ▪ Information encoded by number of action potentials, not size & if you have a week stimulu it will couse less # of action potentials ↳ strong stimul will - generate oc tion more potentials WHAT IS GOING ON DURING THE DIFFERENT PARTS OF ACTION POTENTIAL?  RESTING MEMBRANE POTENTIAL AND THRESHOLD ▪ RMP is -60 to -70 mV → K+ channels are open → Na+ channels are closed ▪ Small depolarizing stimulus causes depolarization membrane potential becomes less & comes from cell body/some negative and approach threshold potential (-40 mV)  So 40 - 78 & - & + Some V-goted Net VOLTAGE-GATED Na + this change only charnes happens at exo r hillock CHANNELS the rest of the cell is of RMP OPEN/ACTIVATE ▪ At threshold: → Voltage-gated Na+ channels open/activate (because of change in membrane voltage) → Na+ ions rush into the cell + Nat/k pump puts more Not outside the cell. Cell is (-1s0 → Membrane potential becomes ↓ Not wants to run im positive depolarization both electrically and chemically influenced  VOLTAGE-GATED Na + CHANNELS INACTIVATE Not channel * to close begin ▪ After 1 millisecond, the Na+ channels inactivate they system are on a timer Stoy → Inactivation = channel closed and closed temporarily unable to open again until are they unlocked again → No more Na+ entering cell → Absolute refractory period & Not channels a re already open/inactivated fire of another ac tion potent impossible , So it is to  VOLTAGE-GATED K + CHANNELS OPEN/ACTIVATE ▪ As membrane depolarizes, voltage- gated K+ channels slowly open/activate → “Delayed-activating” K+ channels → K+ flows out of cell & inside the cell is positive → Membrane hyperpolarizes Slower to open/close → Relative refractory period ↳ Not channels have reset even overshoot Would take m o re during this period. be due to already of a bump to re-open Not chennes Slow → Voltage-gated K+ channels close becoming m o re ( t closure but other K+ channels stay open → Na+ reset voltage activated reset when membrane voltage more  CLASS QUESTION Which number corresponds to when Na+ ions enter the neuron? Answer: 2? 2 between 1-2 when Not activated ↳ so ore K+ chemes  SUMMARY ▪ Membrane voltage potentials ▪ Overview of an action potential ▪ Concentration gradient ▪ Electrical forces ▪ Electrical forces ▪ Pumps ▪ Pumps ·  SUMMARY ▪ Membrane voltage potentials ▪ Overview of an action potential ▪ Concentration gradient ▪ Electrical forces ▪ Electrical forces ▪ Pumps ▪ Pumps ACTION POTENTIAL CONDUCTION DOWN THE AXON  every step isactive ACTIVE PROPAGATION – UNMYELINATED AXON if not attached to cell body & only happens when ? information travel short how do you get stimul bump distences ; usually in some region from of the previous segment &xon's depolarization of the broin unmyelinated neuron floats over through ICE get flipping of membrane OpenSNot works its way down the a xo n of - membrane piece of member sodium from previous leas through and allow action potential to travel down to piece Segment axon termind is active propagation P action potential Only travel in o n e direction. refractory period prevents action potential from traveling in the wrong direction toward the cell body ▪ Active propagation of action potential is slow (10 m/s), but does not weaken ▪ Takes many small steps down the axon – some chance of failure at every step a very unlikely to fail  PASSIVE PROPAGATION – MYELINATED AXON & beyond the neighboring nerrons ▪ Action potential triggered at axon hillock, moves passively through the myelinated segment – quick (150 m/s), but ion channels isbed signa weakens as it signal weakens as it travels greater chance of failure absence of myelin & ▪ At Node of Ranvier, it regains ~ where ion channels and Nat/Kt pump located d moves passively full charge through active means (Na/K channels) ↑ has to mere the Apcon be generated flow all the way to the ▪ Then moves passively through main difference Avs4 = Not has to travel further Next Node if not... of Renvier Ap is lost next myelinated segment  CLASS QUESTION If someone is exposed to a toxin that blocks voltage- gated Na+ channels, their action potentials will______ A. Get smaller B. Not be generated C. Get larger Answer: B?  TOXINS TARGET VOLTAGE-GATED CHANNELS ▪ Tetrodotoxin (puffer fish) and saxitoxin (algae) block voltage-gated Na+ channels ▪ Batrachotoxin (frog) forces Na+ channels to stay open ▪ Agitoxin (scorpion) and beta- bungarotoxin (snake) block voltage- gated K+ channels HOW ARE ACTION POTENTIALS CONVERTED INTO CHEMICAL SIGNALS AT THE SYNAPSE? PRE-SYNAPTIC SIDE  AN ACTION POTENTIAL CAUSES NEUROTRANSMITTER RELEASE ▪ Action potential reaches the pre- synaptic axon terminal: action opens potential chennels → voltage-gated Ca+2 channels open → Ca+2 enters terminal * the important trigger for the release of neurotrons mitter → Ca+2 causes synaptic vesicles to fuse with the presynaptic membrane → release neurotransmitter into the synaptic cleft = exocytosis  STEPS OF EXOCYTOSIS ▪ Vesicles are packets of neurotransmitters ▪ SNARE proteins: on the membrane → v-SNARES and t-SNARES vesicular - oxon termine tronomembrane shores → docked at presynaptic membrane, Shores waiting to fuse before Ap recenes terminal the vesicle pull towards exon membrane No trigger for binding of snores reside is transported close to axon terminal and close proximity allows shore to interest close - but hothing  STEPS OF EXOCYTOSIS ▪ Voltage-gated Ca+2 channels open ↳ by the action potential ▪ Ca+2 sensor: synoptorgmin -a binds → Synaptotagmin pulls physically vesicle closer to exon terminal - fuse colcium → Fusion and neurotransmitter release  CLASS QUESTION If someone is exposed to a toxin that changes neurotransmitter release at muscles, they may experience ______ O A. Muscle weakness or paralysis contracting O B. Muscle tightening or spasms reloxing O C. Death ? ofalltheofabove Answer: All the above  ALL ABOUT NEUROTRANSMITTERS!  NEUROTRANSMITTERS ▪ Basis of communication between neurons ▪ Many different chemicals act as neurotransmitters in brain: motor neurons make ACn → Glutamate, GABA, dopamine, serotonin, norepinephrine, - acetylcholine Specific combination based on the type of neuron ▪ Each neuron uses one (or maybe two or three!) neurotransmitters; different neurons use different neurotransmitters ▪ Each neurotransmitter can trigger a different effect on the post-synaptic cell from (often away enzyme not · converte on amino did we derive our dief into a neurotransmitter ,  NEUROTRANSMITTER PRODUCTION ▪ Neurons must synthesize their neurotransmitter and move it into vesicles ▪ A specific enzyme (protein) is involved in producing each neurotransmitter ▪ Often, that enzyme converts an amino acid we derive from our diet into a neurotransmitter SYNAPTIC CLEFT  NEUROTRANSMITTERS CROSS THE SYNAPTIC CLEFT Waves of release a re discrete waves ▪ Neurotransmitters diffuse across until they reach the post- synaptic membrane ▪ Extra neurotransmitter is * recycling degraded by enzymes, or taken up by presynaptic terminals or astrocytes (tripartite synapse) a lot of neurotronsmitted I exce degraded or are released then needed in taker book to hopes they repen the other side pre-synoptic or taken by astrocytes to book to go pre- POST-SYNAPTIC SIDE  POST-SYNAPTIC DENSITY ▪ Dendrites/spines have post-synaptic densities with receptors proteins neuro will bind ▪ Neurotransmitters bind to receptors on post-synaptic membrane  RECEPTORS ▪ Ionotropic receptors fast → Ligand-gated ion ↑ channels needs neuro bound to be activated opens on ▪ Metabotropic receptors Not ion channel Dostsynaptic and ions flow in out → Receptor activates Slow G-protein G PCR receptors - when bound activate by neuro introcellular can eventually ,