Nervous System - Neuron Structure, Action Potential, and Synapses PDF

1.​ Functions of the Nervous System ○​ Sensory: Detects internal and external stimuli through receptors. ○​ Integrative: Processes and interprets sensory input, deciding on appropriate responses. ○​ Motor: Initiates responses by activating effectors such as muscles an...

1.​ Functions of the Nervous System ○​ Sensory: Detects internal and external stimuli through receptors. ○​ Integrative: Processes and interprets sensory input, deciding on appropriate responses. ○​ Motor: Initiates responses by activating effectors such as muscles and glands. 2.​ Central Nervous System (CNS) vs. Peripheral Nervous System (PNS) ○​ CNS: Composed of the brain and spinal cord; processes information and coordinates responses. ○​ PNS: Consists of nerves and ganglia outside the CNS; connects the CNS to the rest of the body. 3.​ Neuron and Types ○​ A neuron is a specialized cell for transmitting electrical signals. ○​ Types: ​ Sensory (afferent): Transmit signals from receptors to the CNS. ​ Motor (efferent): Transmit signals from the CNS to effectors. ​ Interneurons: Connect sensory and motor neurons; process information. 4.​ Divisions of the PNS ○​ Somatic Nervous System (SNS): Controls voluntary movements; innervates skeletal muscles; includes sensory and motor pathways. ○​ Autonomic Nervous System (ANS): Controls involuntary functions; innervates smooth muscle, cardiac muscle, and glands; divided into sympathetic and parasympathetic systems. ○​ Enteric Nervous System (ENS): Governs the gastrointestinal tract; functions independently but can interact with the CNS and ANS. 5.​ Neurons vs. Neuroglia ○​ Neurons: Excitable cells responsible for transmitting electrical signals. ○​ Neuroglia: Supportive cells providing protection, nourishment, and insulation for neurons. 6.​ Types of Neuroglia and Functions ○​ Astrocytes: Maintain the blood-brain barrier; regulate ion and nutrient levels. ○​ Microglia: Act as phagocytes; remove debris and pathogens. ○​ Oligodendrocytes: Produce myelin in the CNS. ○​ Schwann Cells: Produce myelin in the PNS. ○​ Ependymal Cells: Line brain ventricles; produce and circulate cerebrospinal fluid. ○​ Satellite Cells: Provide support and nutrients to neurons in the PNS. 7.​ Neuron Structure ○​ Cell Body: Contains nucleus and organelles. ○​ Dendrites: Receive input from other neurons. ○​ Axon: Transmits electrical impulses. ○​ Axon Terminals and Synaptic End Bulbs: Release neurotransmitters into the synaptic cleft. 8.​ Axonal Transport ○​ Purpose: Moves substances along the axon.  ○​ Methods: ​ Anterograde: Transport from the cell body to the axon terminals. ​ Retrograde: Transport from axon terminals to the cell body. 9.​ Types of Neurons ○​ Multipolar: One axon, multiple dendrites (common in the CNS). ○​ Bipolar: One axon, one dendrite (found in special senses). ○​ Unipolar: Single process splitting into two branches (common in sensory neurons). 10.​Definitions ○​ Nerve: Bundle of axons in the PNS. ○​ Cranial Nerves: Originate from the brain. ○​ Spinal Nerves: Originate from the spinal cord. ○​ Ganglia: Clusters of neuron cell bodies in the PNS. 11.​White Matter vs. Gray Matter ○​ White Matter: Composed of myelinated axons. ○​ Gray Matter: Composed of neuron cell bodies, dendrites, and unmyelinated axons. 12.​Types of Ion Channels ○​ Voltage-gated: Open/close in response to voltage changes. ○​ Ligand-gated: Open/close when specific chemicals bind. ○​ Mechanically-gated: Open/close in response to physical deformation. ○​ Leak Channels: Allow constant ion flow. 13.​Graded Potential vs. Action Potential ○​ Graded Potential: Small, localized changes in membrane potential. ○​ Action Potential: Large, uniform depolarizations propagated along axons. ○​ Hyperpolarization: Membrane potential becomes more negative. ○​ Hypopolarization/Depolarization: Membrane potential becomes less negative. 14.​Neuron Action Potential ○​ Resting Potential: -70 mV maintained by Na+/K+ pumps. ○​ Threshold: Membrane potential at which an action potential is triggered. ○​ Depolarization: Rapid Na+ influx. ○​ Repolarization: K+ efflux restores resting potential. 15.​All-or-None Principle ○​ An action potential occurs fully if threshold is reached; otherwise, it does not occur. 16.​Refractory Period ○​ Absolute: No new action potential can occur. ○​ Relative: Action potential can occur with a stronger stimulus. 17.​Summation ○​ Temporal: Multiple signals from one source over time. ○​ Spatial: Signals from multiple sources. 18.​Nerve Fiber Classification ○​ A Fibers: Large, myelinated, fast. ○​ B Fibers: Medium, lightly myelinated.  ○​ C Fibers: Small, unmyelinated, slow. 19.​Conduction ○​ Continuous: Slow conduction in unmyelinated fibers. ○​ Saltatory: Fast conduction in myelinated fibers. 20.​Chemical vs. Electrical Synapses ○​ Chemical: Use neurotransmitters; slower. ○​ Electrical: Use gap junctions; faster. 21.​Ionotropic vs. Metabotropic Receptors ○​ Ionotropic: Directly open ion channels. ○​ Metabotropic: Trigger secondary messengers. 22.​Chemical Synapse Events ○​ Action potential triggers Ca2+ influx. ○​ Neurotransmitter release into the synaptic cleft. ○​ Binding to post-synaptic receptors. 23.​Definitions ○​ Pre-synaptic Cell: Releases neurotransmitter. ○​ Post-synaptic Cell: Receives signal. ○​ Synaptic Gap: Space between cells. ○​ Neurotransmitter: Chemical messenger. ○​ Receptor Sites: Bind neurotransmitters. 24.​Neurotransmitter Removal ○​ Diffusion: Away from synaptic cleft. ○​ Reuptake: Into presynaptic cell. ○​ Enzymatic Degradation: Breakdown by enzymes. 25.​Excitatory vs. Inhibitory Neurotransmitters ○​ Excitatory: Depolarize post-synaptic cell. ○​ Inhibitory: Hyperpolarize post-synaptic cell. 26.​IPSP and EPSP ○​ IPSP: Inhibitory post0-synaptic potential. ○​ EPSP: Excitatory post-synaptic potential. 27.​Neurotransmitter Modifications ○​ Alter release, receptors, or reuptake. 28.​Neural Circuits ○​ Simple Series: One-to-one pathway. ○​ Diverging: One input, multiple outputs. ○​ Converging: Multiple inputs, one output. ○​ Reverberating: Feedback loop. ○​ Parallel After-Discharge: Multiple pathways converging on one output. 29.​Plasticity and Neurogenesis ○​ Plasticity: Neural adaptability. ○​ Neurogenesis: Formation of new neurons. 30.​Regeneration and Repair- a process by which damaged tissue undergoes regrowth or renewal, leading to eventual restoration of nervous system function know channels & stimulus