This lecture covers types of nervous systems, the structure of the human nervous system, and the structure of the brain. It also explains how the nervous system transmits electrical signals. Neurons have a resting potential of around -70 mV due to the differing ion concentrations (sodium and potassium) inside and outside of the cell. The cell membrane maintains the charge using gated ion channels and selective permeability. Signals are transmitted via large changes in membrane potential. A cell is at rest until a stimulus allows sodium into the cell, causing some depolarization. At a certain potential, sodium channels open, increasing positive charge. They close quickly and voltage-gated potassium channels open, allowing potassium out of the cell. This impulse travels along the line of cells like a row of dominoes.
Neuron structure: The cell body
contains the nucleus and organelles. Dendrites extend from the cell
body and receive incoming stimuli. The axon hillock is the region
where the action potential is initiated. The impulse is carried away
from the cell body by the axon.
The myelin sheath is produced
by Schwann cells and acts as an insulator, increasing the conduction
of the electrical signal.
The Nodes of Ranvier are
segments of the axon that are not myelinated.
An action potential is
triggered when a stimulus causes sodium channels to open, thus
depolarizing a cell. If the cell reaches its threshold potential,
voltage-gated sodium channels will open, resulting in a rapid, large
depolarization of the cell.
The voltage-gated sodium
channels close quickly and voltage-gated potassium channels open,
repolarizing the cell.
During the absolute refractory
period following an action potential, another action potential
cannot be initiated.
Depolarization of the synaptic
terminal membranes by an action potential stimulates the opening of
voltage-gated calcium channels. The subsequent increase in calcium
concentration in the synaptic terminal causes the exocytosis of
The Nervous System
Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.
The book and CD package include two full length practice exams that are presented with all questions answered and explained. The author also presents detailed reviews of all test topics and includes multiple-choice and free-response questions with answers at the end of each topic's chapter.
This book includes a review of the AP Biology exam format and scoring, proven strategies for answering multiple-choice questions, and hints for tackling the essay questions. The practice tests include answers and explanations and there is also proven test-taking strategies for both the multiple choice and essay parts.