Overview of the Nervous System

These flashcards cover major concepts related to the anatomy and physiology of the nervous system as discussed in the lecture notes.

Central Nervous System (CNS)

Consists of the brain and spinal cord; processes information and issues commands.

Peripheral Nervous System (PNS)

Includes all nerves and ganglia outside the CNS; connects the CNS to the rest of the body.

Endocrine system

communicates by means of chemical messengers (hormones) secreted into to the blood

Nervous system

utilizes neurons (nerve cells) to send messages from cell to cell by electrical and chemical means; occurs in three steps

First step in nervous system

It receives stimuli from external environment and transmits messages to central nervous system (CNS)

Second step in nervous system

The CNS processes the information and determines response

Third step in nervous system

CNS issues commands to muscle and gland cells to carry out response

Neuron

A nerve cell; the basic building block of the nervous system that transmits signals.

Nerve

a bundle of nerve fibers (axons) wrapped in fibrous connective tissue

Axon

The long, cylindrical extension of a neuron that conducts electrical impulses away from the cell body.

Dendrite

Branching extensions of a neuron that receive signals from other neurons.

Ganglion

A knot-like swelling in a nerve where neuron cell bodies are concentrated.

Sensory (afferent) neurons

Neurons that transmit signals from sensory receptors to the CNS.

Somatic sensory division

carries signals from receptors in the skin, muscles, bones, and joints

Visceral sensory division

carries signals from the viscera (heart, lungs, stomach, and urinary bladder)

Motor (efferent) neurons

Neurons that convey commands from the CNS to muscles and glands.

Somatic motor division

carries signals to skeletal muscles; causes voluntary muscle contraction and automatic reflexes

Visceral motor division

(ANS); carries signals to glands, cardiac and smooth muscle; no voluntary control; responses called visceral reflexes

Sympathetic division

Of ANS; stimulates and prepares the body for action

Parasympathetic division

Of ANS; has a calming effect on the body

Enteric Plexus

within digestive tract wall enables coordination and communication within digestive tract

Interneurons

Neurons that process information within the CNS and connect sensory and motor pathways.

Excitability

A property of neurons that enables them to respond to stimuli.

Conductivity

The ability of neurons to transmit electrical signals.

Secretion in neurons

The release of neurotransmitters when an electrical signal reaches the end of an axon.

Sensory (Afferent) Neurons

detect stimuli and transmit information about them toward the CNS

Motor (Efferent) Neurons

Send signals out of muscles and gland cells (the effectors)

Cell Body

also called neurosoma, soma, or perikaryon; contains nucleus and many organelles

Neurites

Of neurons; extensions reaching out to other cells

Axon Hillock

Mound on one side of cell body

Axoplasm

Cytoplasm of neuron

Axolemma

Membrane of neuron

Terminal arborization

Profusely branched end of axon

Axon terminal

Each branch of arborization end; bulbous; forms synapse with next cell

Multipolar Neuron

one axon and multiple dendrites; most common type in body, most neurons in CNS

Bipolar Neuron

one axon and one dendrite; examples include olfactory cells, some neurons of retina, sensory neurons of ear

Unipolar Neuron

single process leading away from cell body, splits into peripheral process and central process

Anaxonic Neuron

many dendrites but no axon; found in brain, retina, and adrenal gland

Axonal Transport

two-way passage of materials along an axon

Anterograde Transport

movement away from cell body, down the axon; driven by motor protein kinesin

Retrograde transport

movement up the axon toward the cell body; driven by motor protein dynein

Fast Axonal Transport

200 to 400 mm/day and may be anterograde or retrograde

Slow Axonal Transport

0.2 to 0.5 mm/day; “stop-and-go” movement results in slower overall speed; always anterograde

Oligodendrocytes

form myelin sheaths in CNS

Ependymal Cells

line internal cavities of brain; secrete and circulate cerebrospinal fluid (CSF)

Microglia

macrophages; engulf debris, provide defense against pathogens

Astrocytes

most abundant type; wide variety of functions

Schwann Cells

envelop axons of PNS, form myelin sheath, and assist in regeneration of damaged fibers

Satellite Cells

surround nerve cell bodies in ganglia of PNS; provide insulation around cell body and regulate chemical environment

Resting Membrane Potential (RMP)

The charge difference across a neuron’s plasma membrane at rest, typically around -70 mV.

Electrical Potential

difference in concentration of charged particles between one point and another

Current

flow of charged particle from one point to another

Action Potential

Rapid up-and-down change in voltage across the membrane of a neuron, critical for signal transmission.

Myelin Sheath

Insulating layer that surrounds axons, produced by Schwann cells in the PNS and oligodendrocytes in the CNS.

Neurotransmitter

Chemicals released by neurons that transmit signals across synapses.

Local Potential

Temporary change in voltage in a localized area of the neuron, varies with stimulus strength.

Synapse

The point where a neuron communicates with another cell, which may be another neuron, a muscle cell, or a gland cell.

Neuroglia

Non-neuronal supportive cells in the nervous system, approximately equal in number to neurons.

Calcium channel

Ion channel that opens to allow calcium ions to flow into the presynaptic neuron, triggering neurotransmitter release.

Ion channel

Protein in a cell membrane that allows ions to enter or exit a cell, crucial for action potentials.