The Nervous System: Neurons, Synapses, & Signaling PDF

The Nervous System: Neurons, Synapses, & Signaling  ⑧ i perception Overview...

The Nervous System: Neurons, Synapses, & Signaling  ⑧ i perception Overview 3 collect info how to sense purpose : higher level sense of info sephalized > - 5 make thinking Nervous system must be able to gather information, process that information, and then respond appropriately Divided into central nervous system and peripheral nervous system Neurons are cells of the nervous system; they communicate with each other & other cell types using both electrical and chemical signals Electrical signals are identical (impulse/no impulse) Chemical signals are more diverse (neurotransmitters) Glia are support cells that protect, provide for, and facilitate neuron activities neurons can't does ↳ 5 6 everything - - categories  each of L Function 1 axon dendrite -V-sends I S I signal was j neuron -yes sonasan motor Neurons / pre-synaptic terminal (soma) ~ neurogila Structure: Cell body: location of nucleus & most not organelles (soma) Dendrites: receiving structures connected to avebergtion cell body Axon: typically single long ‘arm’ that transmits signals Axon hillock: connection between cell body & respond can also axon; where electrical signal starts I mean > don't respond Synapse: junction at the end of axon where - communication with other cell(s) occurs via neurotransmitter release from pre-synaptic terminal to post-synaptic membrane cause of brain cancer due to cell div undergoing  %-derance neuron sensory Information Processing pseudounipolar bipolar 1. Sensory input: sensory neurons receive stimulus ‘senses’ ie. smell, sound, sight, taste, touch (including pressure, texture, pain); may be internal or external stimulus 2. Integration: interneurons in brain or ganglia ‘process’ - assessing internal (analyze/interpret) to determine response ' I external signals Brain: [in most animals] large, complex grouping of neurons; associated with head/CNS Ganglia: simple clusters of neurons found in multiple areas throughout the body/PNS /gagged brains ; amts mini can small do processing of facilitates 3. Motor output: muscle-based responses Body movement, gland secretions, changes to heart rate, pupil shifts, etc  know 3 types - Peripheral Nervous System (PNS): sensory and motor neurons Central Nervous System (CNS): interneurons  Sending Signals Neurons use electrical and chemical signals gradient Electrical signals rely on ion establin distributions across membrane Unequal concentrations produce changes differences, aka membrane potential ↑ + Non signaling membrane has resting potential with inside more negative than outside (form of potential energy) Resting potential forms due to action of I sodium-potassium (Na-K) pump actively + wants transporting ions against their gradients to flow sell Membrane should be impermeable to Na+ into and K+, unless ion channels open  impt for cells to maintain ions more + k electro gradient via [high] > - [low] Ion Channels Should allow ions to diffuse across membrane (facilitated diffusion) If prevented, have net positive charge outside cell, net negative charge inside (due to Cl- and negatively charged proteins) Works K+ moves through leak channels that are w/ con. always open; it should exit the cell until equiliom equilibrium potential (chemical gradient gradient balances electrical gradient, preventing net movement) Calculated via Nernst equation y negative ↳ calculated c = rich Vm = 61 5. in (log  · all or nothing response Action Potential To send a message down the axon, depolarize it Open ion channels; net movement of positive ions will move via diffusion, shifting the membrane potential; if enough depolarization, threshold is met, membrane depolarizes, and action potential carries the signal toward the synapse Ion channels: Ligand gated: controlled by chemical canart a signals Acetylcholine ex. Voltage gated: controlled by electrical signals S I · open doors propagation plug ; triggered by electricity wave of very fast signals * refractory period -  Notes on Action Potentials same+ volume - all chem signals same They are all or nothing signals; once threshold is met, voltage-gated channels will open & action potential will go All electrical signals are at the same ‘volume’; frequency of signals can send ‘stronger’ or ‘weaker’ signals & reestavin, Cannot send action potentials too closely due to refractory period when Na+ modify can this channels cannot be stimulated due to inactivation during action potential Action potentials may need to move through very long axons; speed transit time by insulating axons to ‘skip’ between nodes of Ranvier via saltatory conduction lipids > - Insulation from glial cells: oligodendrocytes (CNS) or Schwann cells (PNS) wrap axons lipid-rich myelin sheaths speeds> - up rxn rate don't need to open all Nat channels pre TEF -can skip some & insulated  skip sections I opening less = Faster channels signal  Synapse Connection between axon and post-synaptic membrane/cell could use either electricity or chemicals Electrical synapses use gap ~ hearts junctions to directly connect neurons (rare) Chemical synapses leave a synaptic cleft (space) between cells, bridged via neurotransmitters (common) ( ligand for post syn - terminal chemical syn electrical I 2 + & acts like a chemical signal + 1 Ca chemical of · more complex chemical syn > - variety response - - action - electic -----  Chemical Synapse Neurotransmitters are stored in synaptic vesicles and released when the action potential reaches the synapse due to the movement of Ca2+ Amount of neurotransmitter released and receiving receptor sensitivity allows for complex communication Recipient cell has ligand-gated ion channels that recognize neurotransmitters (ionotrophic receptors) Receptors related to being responsive = excitatory postsynaptic potential (EPSP) gas pedal [depolarize, making sending signals easier] - lets something ! initiates response do Receptors related to reducing response = inhibitory postsynaptic potential (IPSP) [hyperpolarize, making sending signals harder] reduce response - brake pedal - Chemical Synapse Con’t receiving information Responses to synaptic messages in neurons: One synapse is unlikely to trigger a neuron to initiate an action potential Summation = combination of EPSPs may be sufficient to depolarize above threshold in axon hillock, starting signal [signals that are close together may ‘add’ together] What happens after synapse? Neurotransmitters are collected from the synaptic cleft and returned to vesicles in the pre-synaptic terminal Enzymes are crucial to this process; without them there cannot be C continued function dean up neurotrans > - shove into new rescicles in presyn. Terminal (recycle neurotrans Ctiming adding 2 together to amplify signal 1 excitatory - builds up signals 2. Inhibitory over time - repeative  of brain perception - Neurotransmitters Neurons use multiple neurotransmitters, and each can have multiple effects on different postsynaptic receptors channels not ion GPCRs - Neurotransmitters include: trigger effects in phos activities. ↳ control cascades to inside of cell Acetylcholine: organic molecule that triggers both ligand-gated ion channels (ionotropic) and G protein-coupled receptors (metabotrophic: non-ion channel receptors that trigger secondary messenger(s) & metabolic steps); used to trigger skeletal muscle contractions > inhibits - overreactive (too communication) neurons much Amino acids: ex: GABA (major inhibitor in the brain; used in anxiety meds) Biogenic amines: ex: norepinephrine (alertness), dopamine (‘reward’), serotonin Chappy) (‘happy’); levels may be impacted by depression meds ↑ pleasure Neuropeptides: endorphins (dull pain perception); opiates mimic Gases: NO (relax smooth muscle; made on demand & locally; breakdown inhibited by Viagra) can affect to response Stimuli