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Physiology
Intro to Nervous System and Action Potentials
| Concept | Explanation |
|---|---|
| Major Functions of Nervous System | Sensory input, Integration, and Motor output |
| Sensory Input | the external and internal information collected from the environment—such as sights, sounds, smells, and physical sensations (sent to the brain) |
| Integration | the process by which the brain and spinal cord process incoming sensory information, evaluate it, and make a decision for an appropriate response |
| Motor output | final stage of nervous system processing that translates sensory inputs and integrated decisions into tangible actions, such as voluntary movement, reflex reactions, or physiological responses |
| Afferent (sensory) | bring sensory information in to the central nervous system |
| Efferent (motor) | carry motor commands out from the central nervous system to the rest of the body |
| Somatic nervous system (SNS) | part of peripheral nervous system responsible for all voluntary body movements and processing conscious sensory information. |
| Autonomic nervous system (ANS) | network of nerves that regulates the body's involuntary, unconscious processes, such as heart rate, digestion, respiration, and pupil response |
| Sympathetic nervous system (SNS) | branch of the autonomic nervous system responsible for the body's involuntary "fight-or-flight" response |
| Parasympathetic nervous system (PSNS) | division of the autonomic nervous system responsible for the body's "rest and digest" state |
| Enteric nervous system (ENS) | vast, semi-autonomous network of millions of neurons embedded in the walls of the gastrointestinal tract that independently regulates vital digestive processes such as motility, enzyme secretion, and blood flow |
| Astrocytes (job in a nutshell) | structural support and blood-brain barrier maintenance |
| Oligodendrocytes (job in a nutshell) | form CNS myelin |
| Microglia (job in a nutshell) | CNS immune defense and clean up through phagocytosis |
| Ependymal cells (job in a nutshell) | CSF (cerebrospinal fluid) production and circulation |
| Schwann cells (job in a nutshell) | form PNS myelin and assist nerve regeneration |
| Satellite cells (job in a nutshell) | support neurons in peripheral ganglia |
| Myelin Fxn | Insulates axons & Increases conduction velocity |
| Myelin is produced by... | Oligodendrocytes (CNS) & Schwann cells (PNS) |
| Saltatory conduction | rapid propagation of action potentials along a myelinated axon |
| Electrical insulation | Axon wrapped in sections of myelin down its length |
| Nodes of Ranvier | uninsulated gaps in the myelin sheath along a neuron's axon that are critical for nerve signal transmission, serving as the points where electrical impulses (action potentials) are regenerated and rapidly "leap" down the axon |
| Excitable Tissue | Tissues capable of generating rapid electrical impulses in response to stimuli |
| Types of excitable tissues | Nerve, Skeletal muscle, Cardiac muscle, & Smooth muscle |
| Synapse | the specialized junction where a neuron (nerve cell) communicates with another cell |
| Presynaptic | the transmitting side of a synapse in the nervous system |
| Neurotransmitter | Chemical messengers that transmit signals from one nerve cell (neuron) to a target cell |
| EPSP | excitatory postsynaptic potential |
| IPSP | inhibitory postsynaptic potential |
| (T/F) All living cells have a voltage difference across the plasma membrane. | True |
| Resting Membrane Potential (RMP) | Occurs when a neuron is not transmitting signals |
| Typical Neuron Membrane potential (mV) | -70mV |
| (T/F) The inside of the cell is positive relative to the outside | False |
| Causes of RMP in cell | Sodium-Potassium Pump & Potassium Leak Channels |
| Ions in and out of cell due to Sodium-Potassium Pump per ATP consumed | 3 Na⁺ out & 2 K⁺ in for each ATP consumed |
| Fxn of Potassium Leak Channels | Allow K⁺ to leave the cell |
| Result of Potassium Leak Channels | Cell interior becomes negative |
| Temporal Summation | Several impulses from one neuron over time |
| Spatial Summation | Impulses from several neurons at the same time |
| (T/F) An unmyelinated axon is positively charged when active | True |
| (T/F) An unmyelinated axon is negatively charged when active | False |
| (T/F) An unmyelinated axon is negatively charged unless active | True |
| (T/F) Concentration gradients and electrical gradients do not drive ion movement | False |
| Major determinant of resting potential | Potassium Leak Channels |
| Action Potential | Rapid, transient reversal of membrane polarity |
| Threshold Potential | critical electrical charge required to trigger an action potential (nerve impulse) |
| Membrane Potential/Voltage at peak of Action Potential | + 30 to + 40 mV |
| Membrane Potential/Voltage of Threshold Potential | Approximately - 55mV |
| Depolarization | Opening of voltage-gated Na+ channels and membrane potential is becoming more positive toward AP |
| Repolarization | Opening of voltage-gated K+ channels and membrane potential is becoming more negative |
| Hyperpolarization | Membrane becomes more negative than resting |
| (T/F) Ion gradients are restored when membrane potential returns to resting state | True |
| All-or-None Principle | Once threshold reached, full AP generated |
| (T/F) During the Absolute Refractory Period a second AP is possible | False |
| (T/F) During the Relative Refractory Period a stronger stimulus is required for an AP | True |
| Propagation of AP | Local current flow activates adjacent membrane |
| Continuous Conduction | Occurs in unmyelinated axons because there are no synapses (no leaps) |
| Factors Affecting Velocity | Diameter, myelination, temperature |
| (T/F) The smaller the diameter, the faster the conduction | False |
| (T/F) Warmer temperatures accelerate ion channel gating | True |
| (T/F) Action Potentials in Skeletal Muscle do not Trigger excitation-contraction coupling | False |
| (T/F) Action Potentials in Cardiac Muscle Coordinate heart contraction | True |
| (T/F) Action Potentials in Smooth Muscle do not Control GI, vascular and reproductive functions | False |
| Synaptic Transmission | Electrical signal converted to chemical signal |
| Local Anesthetics Block voltage-gated Na+ channels | True |
| (T/F) Sodium, Na +, does not cause depolarization | False |
| Reason Myelin Increases Velocity | Nodes of Ranvier cause saltatory conduction which results in channels only needing to be open and depolarize at the nodes rather than along every single micrometer of the axon |
| Saltatory conduction occurs because of... | Nodes of Ranvier |
Created by:
satya.benoit