Nervous System Overview

Nervous System Overview

• Nissl Bodies: Correspond to rough endoplasmic reticulum; involved in protein synthesis; scattered in neuronal cytoplasm.
• Neurofibrils: Fine thread network within the nerve fiber; provide structural support to the axon.
• Dendrites: Branching neuron processes that receive impulses and direct them towards the cell body.
• Collateral: Branching extensions of an axon contributing to signal distribution.

Types of Neurons

• Axon: A single nerve fiber that transmits impulses away from the neuron’s cell body.
• Interneurons: Connect sensory and motor neurons; function within the central nervous system to process information.
• Motor Neurons (Efferent): Relay impulses from the CNS to effectors like muscles and glands.
• Sensory Neurons (Afferent): Conduct impulses from sensory receptors to the CNS.

Neuroglial Cells

• Astrocytes: Star-shaped cells that maintain the blood-brain barrier and provide structural support in the CNS.
• Oligodendrocytes: Form the myelin sheath around axons in the CNS.
• Microglia: Phagocytic cells that act as immune defense within the CNS.
• Ependyma: Line the ventricles and central canal; involved in cerebrospinal fluid production.
• Schwann Cells: Myelinate peripheral neurons and form the neurilemma.
• Satellite Cells: Support neurons in ganglia within the PNS.

Neuroanatomy

• Cell Body Features: Contains neurofibrils, Nissl bodies (protein synthesis), and the nucleus.
• Axon Components: Includes collaterals, axon terminals, synaptic knobs, reliant on Schwann cells for myelination, and features nodes of Ranvier for signal transmission.
• Parts of a Neuron: Dendrites, cell body, and axon form the core structure.

Physiological Principles

• Action Potential: Describes the nerve impulse; a sequence of electrical changes following stimulation.
• Threshold Potential: Minimum level required to trigger an action potential in a neuron.
• Saltatory Conduction: Rapid impulse conduction across myelinated axons, jumping between nodes of Ranvier.
• Refractory Period: Time post-stimulation when a neuron is non-responsive to additional stimuli.

Synaptic Mechanism

• Synapse: Junction between neurons; consists of presynaptic and postsynaptic neurons.
• Neurotransmitters: Chemicals released into synapses to stimulate or inhibit target cells; include excitatory and inhibitory types.
• Synaptic Transmission: Process where impulses from the presynaptic neuron influence the postsynaptic neuron.

Membrane Dynamics

• Membrane Potential: Electrical difference across a cell membrane due to ion distribution.
• Resting Potential: Established when a neuron is inactive; key for creating action potentials.
• Synaptic Potential: Changes in postsynaptic membrane potential following neurotransmitter release.

Nervous System Functions

• Three Main Functions:
  • Sensory: Receives and processes environmental stimuli.
  • Integrative: Evaluates sensory information and makes decisions.
  • Motor: Carries out responses by activating effectors.

Nervous System Subdivisions

• Central Nervous System (CNS): Comprises the brain and spinal cord.
• Peripheral Nervous System (PNS): Encompasses cranial and spinal nerves; facilitates communication between the CNS and the body.

Neuron Classification

• Multipolar Neurons: Multiple processes; most common type found in the CNS.
• Bipolar Neurons: Two distinct processes; involved in sensory pathways.
• Unipolar Neurons: Single process diverging into peripheral and central branches; primarily found in sensory neurons.

Tissue Appearance

• Myelinated Axons: Appear white and conduct impulses rapidly.
• Unmyelinated Tissue: Appears gray; generally slower in impulse conduction.

Explore the essential components of the nervous system, including Nissl bodies, neurofibrils, and various types of neurons. This quiz covers the roles and structures of axons, interneurons, motor and sensory neurons, as well as neuroglial cells. Test your knowledge of how these elements interact to maintain neural function.