Review! Chapter 7: The Nervous System

Functions of the Nervous System

• Monitors changes inside and outside the body.
• Processes and interprets information to solve problems.
• Commands responses by activating muscles, glands, and other nervous system components.

Central Nervous System (CNS)

• Comprises the brain and spinal cord.
• Responsible for integrating and processing sensory information.

Peripheral Nervous System (PNS)

• Consists of cranial and spinal nerves plus ganglia.
• Connects all body parts to the CNS, functioning as a communication network.

Autonomic Nervous System

• Regulates involuntary activities of the heart, smooth muscles, and glands.
• Also known as the involuntary nervous system.

Somatic Nervous System

• Controls voluntary activities, primarily activating skeletal muscles.

Neuroglia

• Support, insulate, and protect neurons.
• Capable of division, responsible for most brain tumors.

Neurons

• Exhibit irritability and conductivity.
• Facilitate electrical signal transmission and neurotransmitter release.
• Amitotic, meaning they do not divide.

Axon

• Conducts impulses away from the neuron cell body.

Axonal Terminal

• Responsible for releasing neurotransmitters into the synapse.

Dendrite

• Conducts electrical currents toward the neuron cell body.

Myelin Sheath

• Increases the speed of impulse transmission along the axon.

Cell Body

• Houses the nucleus of the neuron.

Afferent (Sensory) Neurons

• Conduct impulses toward the CNS from peripheral body parts.

Association Neurons (Interneurons)

• Connect sensory and motor neurons, processing signals within the CNS.

Efferent (Motor) Neurons

• Carry impulses away from the CNS to activate muscles and glands.

Ganglion

• A collection of nerve cell bodies outside the CNS.

Neurotransmitters

• Chemicals released by axon terminals, facilitating communication between neurons.

Nuclei

• Collections of nerve cell bodies located within the CNS.

Synapse

• Junction where communication occurs between neurons.

Tract

• Pathways for communication within the CNS, traveling up and down the spinal cord.

Stimuli

• Internal or external changes that impact the nervous system's functioning.

Cutaneous Sense Organs

• Specialized sensory receptors in the skin, detecting temperature, pressure, and pain.

Nodes of Ranvier

• Gaps within the myelin sheath that facilitate faster signal transmission.

Proprioceptors

• Sensory receptors located in muscles and tendons that sense stretching.

Schwann Cells

• Cells responsible for myelinating peripheral nerve fibers.

One-Way Conduction at Synapses

• Ensured as axons can only release neurotransmitters while dendrites receive them.

Neuron Classification

• Based on the number of processes attached: unipolar, bipolar, or multipolar.

Unipolar Neurons

• Characterized by a single, short process that divides into peripheral and central processes; mainly sensory neurons.

Bipolar Neurons

• Possess one axon and one dendrite; found in specialized sensory organs (e.g., eyes, ears).

Multipolar Neurons

• Feature multiple dendrites and a single axon; predominant in the brain and spinal cord.

Potassium Ions

• The primary positive intracellular ion in resting neurons.

Polarized State

• Electrical condition of the neuron when at rest, with differential charges inside and outside.

Depolarization

• Occurs when sodium ions rush into the neuron, reversing resting potential.

Action Potential

• The waveform of depolarization traveling along the neuron's membrane.

Repolarization

• The process in which potassium ions exit the neuron following depolarization.

Refractory Period

• A phase during which a neuron cannot respond to a subsequent stimulus.

Membrane Permeability and Nerve Impulses

• Decreased sodium permeability reduces the likelihood of generating a nerve impulse.

Endoneurium, Perineurium, and Epineurium

• Connective tissue layers surrounding individual nerve fibers (endoneurium), groups of fibers (perineurium), and entire nerve bundles (epineurium).

Mixed Nerves

• Carry both sensory and motor fibers, facilitating bidirectional communication.