Nervous System Overview

Divisions of the Nervous System

• Comprised of the Central Nervous System (CNS) and Peripheral Nervous System (PNS).

Neurons

• Fundamental units of the nervous system, responsible for transmitting information.
• Classified into three main types: sensory neurons, motor neurons, and interneurons.

Sensory Neurons

• Gather information from internal and external environments and relay it to the CNS for processing.

Motor Neurons

• Convey commands from other neurons to muscles, organs, and glands.

Interneurons

• Exclusive to the CNS, these neurons connect other neurons, facilitating information processing.

Unipolar Neurons

• Characterized by a single projection serving both as axon and dendrites; mainly sensory neurons found in skin, muscles, and organs.

Bipolar Neurons

• Possess an axon for signals to the brain and spinal cord, and dendrites for signals from organs; relatively rare and located in sensory systems (visual and auditory).

Multipolar Neurons

• Featuring multiple dendrites and a long axon, these are primarily motor neurons and interneurons.

Functions of a Neuron

• Receive, integrate, and communicate signals to target cells (other neurons, muscles, glands).

Parts of a Neuron

• Dendrites: Receive messages from other cells.
• Cell Body (Soma): Contains the nucleus, maintaining cell health.
• Axon: Transmits messages to other cells.
• Myelin Sheath: Insulation that speeds up neural signal transmission.
• Nodes of Ranvier: Gaps in myelin facilitating rapid conduction of impulses.
• Axon Terminals: Transmit electrical signals to the synapse.
• Synaptic Knobs (Terminal Buttons): Contain synaptic vesicles with neurotransmitters.

Synapse

• Connection between neurons, transmitting information from the presynaptic neuron to the postsynaptic neuron.

Types of Synaptic Connections

• Neuromuscular Junctions: Connections between neurons and skeletal muscle cells.
• Neuroeffector Junctions: Connections between neurons and smooth muscle or glands.

Neurotransmitters

• Chemical messengers transmitting signals from nerve cells to target cells; categorized into excitatory and inhibitory.

Agonists and Antagonists

• Agonists: Enhance neurotransmitter effects.
• Antagonists: Block or diminish neurotransmitter activity.

Key Neurotransmitters

• Acetylcholine: Triggers muscle contraction, influences hormone release and memory; excitatory.
• Dopamine: Involved in memory, learning, and movement; has both excitatory and inhibitory effects.
• Endorphins: Natural pain relievers that produce feelings of euphoria; inhibitory.
• Epinephrine (Adrenaline): Prepares body for "fight or flight"; acts as both hormone and excitatory neurotransmitter.
• GABA: Regulates mood with an inhibitory action; prevents over-excitation of neurons.
• Serotonin: Influences mood, sleep, and appetite; inhibitory and linked to mental health.
• Glutamate: Critical for learning and memory; excitatory but can cause overstimulation issues like migraines.

Action Potential

• Neural impulse initiated by excitatory or inhibitory signals; travels down the axon triggering neurotransmitter release.

Reuptake

• Process where neurotransmitters exit receptor sites to allow for subsequent stimulation; involves recycling back into synaptic vesicles.

Glial Cells

• Support and protect neurons; more abundant than neurons; provide nutrients, myelinate axons, and remove waste.

Types of Glial Cells

• Astrocytes: Regulate blood flow, maintain fluid composition around neurons, and contribute to the blood-brain barrier.
• Microglia: Act as scavengers, cleaning up dead cells and debris.
• Oligodendrocytes: Produce myelin for axon insulation to enhance action potential speed.
• Schwann Cells: Similar function to oligodendrocytes in the PNS.
• Satellite Glial Cells: Support neuron function and act as a protective barrier in PNS ganglia.
• Ependymal Cells: Line ventricles of the brain and spinal canal, facilitating cerebrospinal fluid circulation.

Explore the essential components of the nervous system, including the Central Nervous System (CNS) and Peripheral Nervous System (PNS). This quiz covers the types of neurons, their functions, and how they contribute to the processing of information in the body.