BSC Exam 5 Neurons and CNS

Nervous System

Master controlling and communicating system of body.

Sensory Input

Information gathered by sensory receptors about changes.

Integration

Processing and interpretation of sensory input.

Motor Output

Activation of muscles and glands produces a response.

Dorsal Root Ganglion

Housing for neuron cell bodies in sensory input.

Afferent Neuron

Sensory neuron transmitting signals to CNS.

Integration Center

Brain and spinal cord process sensory information.

Efferent Fibers

Motor neurons transmitting impulses from CNS.

Somatic Nervous System

Voluntary control of skeletal muscles.

Autonomic Nervous System

Involuntary control of smooth muscle and glands.

Effectors

Organs that perform actions in response.

Central Nervous System (CNS)

Brain and spinal cord; control center.

Peripheral Nervous System (PNS)

Nervous system portion outside CNS.

Sensory Division

Conveys impulses from sensory receptors to CNS.

Motor Division

Transmits impulses from CNS to effectors.

Visceral Sensory Fibers

Convey impulses from internal organs to CNS.

Somatic Sensory Fibers

Convey impulses from skin and muscles to CNS.

Sympathetic Division

Part of ANS; 'Fight or Flight' response.

Parasympathetic Division

Part of ANS; 'Rest and Digest' response.

Neuroglia

Supportive cells surrounding and protecting neurons.

Astrocytes

Most abundant glial cells; support neurons.

Oligodendrocytes

CNS glial cells that insulate axons.

Schwann Cells

PNS glial cells that form myelin sheath.

Microglial Cells

Small cells that monitor and support neurons.

Ependymal Cells

Line brain cavities; circulate cerebrospinal fluid.

Oligodendrocytes

Form myelin sheaths around CNS nerve fibers.

Satellite Cells

Surround neuron cell bodies in the PNS.

Schwann Cells

Myelinate peripheral nerve fibers; aid regeneration.

Neuron

Specialized cell conducting impulses in nervous system.

Neuron Cell Body

Biosynthetic center synthesizing proteins and chemicals.

Soma

Another term for neuron cell body.

Nissl Bodies

Rough ER in neuron; synthesizes proteins.

Ganglia

Clusters of neuron cell bodies in PNS.

Tracts

Bundles of neuron processes in CNS.

Nerves

Bundles of neuron processes in PNS.

Dendrites

Short branches receiving signals toward cell body.

Axon

Long extension transmitting impulses away from soma.

Axon Hillock

Cone-shaped area where axon originates.

Nodes of Ranvier

Gaps in myelin sheath along axon.

Axon Terminals

Distal endings of axon; release neurotransmitters.

Myelin Sheath

Insulating layer increasing impulse transmission speed.

Myelination

Process of forming myelin around nerve fibers.

Action Potentials

Electrical impulses transmitted along axon.

Graded Potentials

Short-distance signals in dendrites.

Neurotransmitters

Chemicals released to communicate between neurons.

Schwann Cell

Glial cell forming myelin sheath in PNS.

Myelin Sheath

Insulating layer around axons formed by Schwann cells.

Nodes of Ranvier

Gaps in myelin sheath between Schwann cells.

Nonmyelinated Fibers

Fibers not wrapped in myelin, surrounded by Schwann cells.

Oligodendrocytes

CNS cells forming myelin sheaths from flat processes.

White Matter

Brain regions with dense myelinated fiber tracts.

Gray Matter

Regions with neuron cell bodies and nonmyelinated fibers.

Multipolar Neurons

Neurons with three or more processes; most common.

Bipolar Neurons

Neurons with two processes; rare in retina.

Unipolar Neurons

Neurons with one short process; sensory receptors.

Sensory Neurons

Transmit impulses from receptors to CNS; mostly unipolar.

Motor Neurons

Carry impulses from CNS to effectors; mostly multipolar.

Interneurons

Connect motor and sensory neurons; mostly multipolar.

Membrane Potentials

Electrical differences across neuron membranes.

Action Potential

Nerve impulse generated by adequate stimulus.

Ion Channels

Proteins allowing ions to cross neuron membranes.

Leakage Channels

Always open ion channels allowing passive ion flow.

Gated Channels

Ion channels that open/close in response to stimuli.

Chemically Gated Channels

Open when neurotransmitters bind to them.

Voltage-Gated Channels

Open/close based on membrane potential changes.

Mechanically Gated Channels

Open/close due to physical deformation of receptors.

Resting Membrane Potential

Potential difference of approximately -70 mV in neurons.

Multipolar Neuron

Neuron with three or more processes; common in CNS.

Bipolar Neuron

Neuron with one axon and one dendrite; rare.

Unipolar Neuron

Neuron with one short process; T-like division.

Interneurons

Connect sensory and motor neurons; mostly multipolar.

Afferent Neurons

Sensory neurons that approach the CNS.

Efferent Neurons

Motor neurons that exit the CNS.

Membrane Ion Channels

Proteins that regulate ion flow across membranes.

Leakage Channels

Ion channels that are always open.

Chemically Gated Channels

Open when neurotransmitter binds to them.

Action Potential

Nerve impulse generated by neuron response.

Resting Membrane Potential

Potential difference across a resting neuron's membrane.

Polarized Membrane

State of membrane at approximately -70 mV.

Effectors

Muscles or glands that respond to motor neuron signals.

CNS

Central nervous system; includes brain and spinal cord.

PNS

Peripheral nervous system; includes all other nerves.

Neuron Cell Body

Contains nucleus and organelles; integrates signals.

Resting Membrane Potential

Electrical charge difference across a neuron's membrane.

Ionic Composition

Concentration of ions inside vs. outside cell.

Na+ Concentration

Higher outside the cell than inside.

K+ Concentration

Higher inside the cell than outside.

Potassium's Role

Most significant in establishing membrane potential.

Sodium-Potassium Pump

Maintains Na+ and K+ concentration gradients.

Membrane Potential Changes

Alterations in ion concentrations and permeability.

Action Potentials

Long-distance signals along axons.

Depolarization

Decrease in membrane potential, less negative inside.

Polarized State

Positive outside, negative inside the membrane.

Hyperpolarization

Increase in membrane potential, more negative inside.

Nerve Impulse Probability

Increased by depolarization, decreased by hyperpolarization.

Current Flow

Varies with stimulus strength in graded potentials.

Decay of Graded Potentials

Signal diminishes quickly over distance.

Action Potential Voltage Change

Brief change of ~100 mV during signal.

Positive Inside During AP

Inside becomes positive, reaching +30 mV.

Resting Membrane Value

Typically around -70 mV in neurons.