Ch 12

Central Nervous System (CNS) Organs

Brain and spinal cord

Peripheral Nervous System (PNS) Organs

Cranial nerves and spinal nerves

Three Functions of the Nervous System

Sensory (sensing changes), Motor (stimulating contractions), and Integrative (analyzing, storing info, making decisions)

Two Primary Cells Found in Nervous Tissue

Neurons (electrically excitable) and Neuroglia (supportive cells)

Nissl Bodies

Rough endoplasmic reticulum in a neuron cell body responsible for helping make proteins

Dendrites

Neuron processes that receive information

Axon

Neuron process that sends out information

Multipolar Neuron

Has 1 axon and multiple dendrites; functionally serves as an integrative and motor neuron

Bipolar Neuron

Has 1 axon and 1 dendrite; functionally serves as a sensory neuron

Unipolar Neuron

Has the axon and dendrite fused into one long process; functionally serves as a sensory neuron

Sensory / Afferent Neurons

Perform the sensory function of the nervous system

Motor / Efferent Neurons

Perform the motor function of the nervous system

Interneurons / Association Neurons

Perform the integrative function of the nervous system

Astrocyte (CNS Neuroglia)

Forms the blood-brain-barrier (BBB)

Oligodendrocyte (CNS Neuroglia)

Makes myelin for multiple axons of multiple neurons in the CNS

Microglial Cell (CNS Neuroglia)

Phagocytizes cellular debris, old/worn-out/dead cells, and pathogens

Ependymal Cell (CNS Neuroglia)

Lines cavities in the brain and makes cerebrospinal fluid

Schwann Cell (PNS Neuroglia)

Makes myelin for one axon of one neuron in the PNS

Satellite Cell (PNS Neuroglia)

Provides support for neuron cell bodies in the PNS

Gray Matter

Nervous tissue consisting of unmyelinated neurons; found in the periphery of the brain and central regions of the spinal cord

White Matter

Nervous tissue consisting of myelinated neurons; found in the periphery of the spinal cord and central regions of the brain

Resting Membrane Potential (~ -70mV)

Difference in charge across the plasma membrane (positive outside, negative inside), maintained largely by Na+/K+ pumps

Na+/K+ Pump Contribution to Resting Potential

Pumps out 3 Na+ ions for every 2 K+ ions it brings in

Threshold Potential

The critical membrane potential level (-55mV) required to trigger an action potential

Depolarization

Change in membrane potential from negative to positive along the inner border, caused by an influx of Na+ through voltage-gated Na+ channels

Repolarization

Change in membrane potential from positive back to negative along the inner border, caused by an efflux of K+ through voltage-gated K+ channels

Hyperpolarization

Change in the membrane potential to a value more negative than the resting membrane potential

Saltatory Conduction

Fast conduction process in myelinated neurons where the action potential "jumps" from one Node of Ranvier to the next

Continuous Conduction

Slower conduction process in unmyelinated neurons where the action potential travels continuously down the entire length of the axon

Axodendritic Synapse

Synapse where the axon of the presynaptic neuron interacts with the dendrite of the postsynaptic neuron

Acetylcholine (ACh)

A major excitatory neurotransmitter used by neurons

Substance P

A neurotransmitter that sends pain information

Neuron Regeneration Rule

Repair of a damaged neuron will occur ONLY if the cell body remains intact

Steps in the Repair of a Neuron Process

1. Wallerian degeneration (distal axon breaks down), 2. Regeneration tube formation (by Schwann cells), 3. Growth of axon, 4. Connection to target cell