Chapter 12

Homeostasis

The maintenance of stable internal conditions in the body, such as temperature, pH, and electrolyte balance, necessary for optimal functioning of cellular processes.

Action Potential

An electrical impulse that travels along the axon of a neuron, characterized by a rapid depolarization followed by repolarization, allowing communication of signals over long distances within the nervous system.

CNS (Central Nervous System)

Composed of the brain and spinal cord, the CNS processes sensory information, coordinates responses, and is central to cognition, memory, and emotional regulation.

PNS (Peripheral Nervous System)

Includes all neurons outside the CNS, including cranial and spinal nerves, responsible for transmitting signals between the CNS and the rest of the body, facilitating voluntary and involuntary actions.

Neuroglia

Supportive cells in the nervous system that provide support, nourishment, and protection to neurons, playing essential roles in maintaining homeostasis and modulating neuronal activities.

Dendrites

The branched extensions of a neuron that receive signals from other neurons, facilitating the integration of synaptic inputs that influence neuronal firing.

Axon

The long projection of a neuron that transmits electrical impulses away from the cell body, often covered by a myelin sheath to enhance signal transmission speed.

Synapse

The space between two neurons where neurotransmitters are released, allowing for communication and signal transmission from one neuron to another.

Neurotransmitters

Chemicals released from presynaptic neurons that transmit signals to postsynaptic neurons, involved in various processes such as mood regulation, movement, and cognition.

Resting Membrane Potential

The voltage difference across the plasma membrane of a resting neuron, typically around -70 mV, which is crucial for the generation of action potentials when stimulated.

Myelination

The process of forming a myelin sheath around the axons of neurons to increase the speed of impulse transmission, essential for efficient nervous system functioning.

Excitatory Postsynaptic Potential

A change in the postsynaptic membrane that makes it more likely to fire an action potential, typically caused by the influx of sodium ions due to neurotransmitter binding.

Inhibitory Postsynaptic Potential

A change in the postsynaptic membrane that makes it less likely to fire an action potential, often resulting from the influx of chloride ions or efflux of potassium ions.

Graded Potentials

Local changes in membrane potential that vary in size and can determine whether an action potential occurs, influenced by the strength and duration of the stimulus.

Oligodendrocytes

Neuroglial cells in the CNS that produce myelin sheaths, which insulate axons and increase the speed at which electrical signals propagate along neurons.

Schwann Cells

Neuroglial cells in the PNS responsible for myelination of peripheral axons, aiding in signal conduction and regeneration of damaged nerves.

Astrocytes

Star-shaped neuroglial cells that maintain the blood-brain barrier, support neuronal metabolism, and modulate synaptic transmission and repair.

Microglia

Phagocytic neuroglial cells that remove debris and pathogens in the CNS, acting as the immune defense of the central nervous system and involved in neuroinflammation.

Synaptic Cleft

The gap between the presynaptic and postsynaptic neurons, where neurotransmitter diffusion and receptor binding occur, facilitating neuronal communication.

Neuronal Plasticity

The ability of neurons to change their connections and behavior in response to new information or damage, enabling learning, memory, and recovery from injury.