Lecture 11 — Homeostasis, Feedback, Nervous System Divisions, Neuron Anatomy and Neuroglia

Vocabulary flashcard study set reviewing Lecture 11 topics, including homeostasis, feedback loops, nervous system structural and functional divisions, neuron anatomy, and neuroglia.

Homeostasis

Dynamic maintenance of internal variables within ranges compatible with cell survival.

Internal Environment

Conditions within the epithelial barrier, including extracellular fluid around cells.

External Environment

Conditions outside the epithelial barrier, including the surroundings and lumens of tracts open to the outside.

Steady State

A relatively constant condition that requires energy to maintain.

Set Point

A target value or range used by a regulatory control system.

Stimulus

A detectable change in a regulated condition.

Receptor

A sensor that detects a stimulus and sends information toward the control center.

Control Center

A component of a feedback system that integrates input and sends output that directs an effector.

Effector

A component of a feedback system that carries out a response that changes the regulated condition.

Afferent Pathway

The pathway along which information travels toward the control center.

Efferent Pathway

The pathway along which commands travel away from the control center to an effector.

Feedback Loop Sequence

Stimulus → receptor → afferent pathway → control center → efferent pathway → effector → response.

Negative Feedback

A mechanism that opposes or reverses the initial change, moving the condition toward its set point to support homeostasis.

Positive Feedback

A mechanism that amplifies the initial change and moves the condition farther from its set point temporarily, continuing toward a terminating event.

Central Nervous System (CNS)

Division consisting of the brain and spinal cord, responsible for integration, processing, and control.

Peripheral Nervous System (PNS)

Division consisting of nerves and ganglia outside the CNS, including cranial and spinal nerves.

Sensory (Afferent) Division

A functional division of the PNS that carries information from receptors toward the CNS.

Motor (Efferent) Division

A functional division of the PNS that carries commands from the CNS toward effectors.

Somatic Sensory Division

Division that detects sensory input from the body, including skin, skeletal muscles, joints, and special senses.

Visceral Sensory Division

Division that detects sensory information from internal organs.

Somatic Motor Nervous System

Efferent pathway that controls skeletal muscle.

Autonomic Nervous System

Efferent pathway that primarily regulates involuntary activity of smooth and cardiac muscle and glands.

Sympathetic Division

Autonomic division that coordinates fight or flight responses, preparing the body for activity or stress.

Parasympathetic Division

Autonomic division that coordinates rest and digest responses, supporting maintenance and digestion.

Neuron

An excitable nervous system cell that receives and conducts electrical signals.

Neuroglia

Supporting cells that protect and support neurons metabolically, physiologically, developmentally, and immunologically in an approximate 1:1 ratio with neurons.

Sensory Neurons

Neurons that carry signals from receptors toward CNS integration centers.

Interneurons

Neurons that process and connect information within the CNS; the most abundant functional neuron class.

Motor Neurons

Neurons that carry output from the CNS to effector cells, tissues, or organs.

Spinal Withdrawal Reflex Sequence

Sensory neuron → interneuron → motor neuron (in a typical multisynaptic reflex).

Soma

The neuron cell body, containing the nucleus.

Dendrites

Neuron structures that receive input and conduct local signals toward the cell body.

Axon

Neuron structure that conducts a nerve impulse away from the cell body toward its terminals.

Myelin Sheath

An insulating covering around parts of an axon that speeds signal conduction.

Nodes of Ranvier

Gaps between myelin segments where the axon membrane is exposed.

Synapse

A junction where a neuron communicates with another cell.

Astrocytes

The most abundant glial cells in the CNS; support neurons and help regulate ions/fluids, metabolism, and the blood-brain barrier.

Oligodendrocytes

Glial cells that form myelin sheaths around CNS axons.

Microglia

Glial cells that engulf microorganisms and debris by phagocytosis and alert immune defenses in the CNS.

Ependymal Cells

Glial cells that line CNS cavities; specialized cells help produce CSF and cilia help circulate it.

Cerebrospinal Fluid (CSF)

Fluid produced and circulated within CNS cavities with the aid of ependymal cells.

Satellite Cells

Glial cells that surround neuron cell bodies in PNS ganglia and provide support.

Schwann Cells

Glial cells that form myelin sheaths around axons in the PNS.