PSY 102 - Chapter 1 (Nerve Cells & Impulses)

What two kinds of cells comprise the human nervous system?

Neurons & glia

How many individual neurons does the human brain contain?

86 billion

How many neurons are in the cerebral cortex and associated areas?

12 to 15 billion neurons

How many neurons in the spinal cord?

1 billion

How many neurons in the cerebellum?

70 billion

Who was the first to demonstrate that the individual cells comprising the nervous system remained separate?

Santiago Ramón y Cajal

Like other cells in the body, neurons contain the following structures

Membrane, nucleus, mitochondria, ribosomes, endoplasmic reticulum

Function of membrane

separates the inside of the cell from outside environment

Function of nucleus

contains chromosomes

Function of mitochondrion

performs metabolic activities and provides energy that the cell requires

Function of ribosomes

synthesize new protein molecules

Function of endoplasmic reticulum

transports newly synthesized proteins to their location

A motor neuron

• has its soma in the spinal cord

• receives excitation from other neurons

• conducts impulses along its axon to a muscle or gland

A sensory neuron

is specialized at one end to be highly sensitive to a particular type of stimulation (touch, light, sound, etc.)

Dendrites

• branching fibers with a surface lined with synaptic receptors responsible for bringing information into the neuron

• some also contain dendritic spines that further branch out and increase the surface area of the dendrite

• the greater the surface are of the dendrite, the more information it can receive

Cell body/soma

• contains the _________

• responsible for the ___________

• covered with _______

• contains the nucleus, mitochondria, and ribosomes

• responsible for the metabolic work of the neuron

• covered with synapses on its surface in many neurons

components of all neurons

dendrites, soma/cell body, axon, presynaptic terminals

axons

• thin fiber of a neuron responsible for transmitting nerve impulses toward other neurons, organs, or muscles

• maybe have a myelin sheath, an insulating material that contains interruptions in the sheath known as nodes of Ranvier

• Presynaptic terminals at the end points of an axon release chemicals to communicate with other neurons

afferent axon

refers to bringing information into a structure

efferent axon

refers to carrying information away from a structure

Interneurons or intrinsic neurons are

those whose dendrites and axons are completely contained within a single structure