Textbook Notes (368,117)
Canada (161,660)
Psychology (2,971)
PSY100H1 (1,821)
Chapter 4

PSYB65 Chapter 4.doc

6 Pages
105 Views
Unlock Document

Department
Psychology
Course
PSY100H1
Professor
Zachariah Campbell
Semester
Fall

Description
PSYB65 – Chapter 4 The Neuron’s Structure: - Neurons are the information-conducting units of the nervous system o Has special characteristics that allow it to send electrical impulses by using changes in chemical charges on its cell membrane Overview of a Neuron: - The most prominent distinguishing features are the dendrites, whose presence greatly increases the cell’s surface area o The dendrites’ surface area is further increased by many branches and by many small protrusions called dendritic spines that cover each branch o Dendrites collect information from other cells, their surface areas determine how much information a neuron can gather o Dendritic spines are the points of communication between neurons, the spines provide some indication of how much information a neuron may receive - Each neuron has a single axon, extending out of an expansion of the cell body known as the axon hillock o The axon may have branches called axon collaterals, which usually emerge from it at right angles o Axon may divide into a number of smaller branches called teleodendria o At the end of each teleodendrion is a knob called an end foot or terminal button  Sits very close to a dendritic spine on another neuron, although it does not touch that spine  Synpase – the space between the axon’s end foot and the neighboring dendritic spine o The single axon limits the neuron to only one output channel for communication - The dendrites and the axon are simply fluid-filled extensions of the cell body o Information flows from the dendrites to the cell body and axon o At each terminal button, information in the form of a chemical message is released onto a target - A neuron is both an information-collecting and an information-processing device o Receives a great deal of information on its hundreds to thousands of dendritic spines, but it has only one axon  So the message that it sends must be averaged or summarized version of all the incoming signals o Information travels on a flow of electrical current that begins on the dendrites and travels along the axon to the terminals  As the impulse reaches the terminal buttons, they release one or more chemicals • These chemicals called neurotransmitter, carriers the message across the synapse o To influence the electrical activity of the receiving cell or target and pass the message along The Cell as a Factory: - The cell makes, ships and exports proteins, the cell’s products o Proteins are complex organic compounds, including enzymes, hormones and antibodies and forms the principal components of all cells - A cell’s outer cell membrane, separates it from its surroundings and allows it to regulate the materials that enter and leave its domain o It envelops the cell body, dendrites and their spines, axon and its terminals and so forms a boundary around a continuous intracellular compartment - Very few substances can enter or leave a cell because the cell membrane presents as an almost impenetrable barrier o Proteins embedded in the cell membrane serve as the gates allowing certain substances to enter or leave - Nuclear membrane – surrounds the cell’s nucleus o Nucleus – houses the genes and chromosomes, where the cell’s proteins are stored and copied o Copies are then sent to a part of the cell called the endoplasmic reticulum (ER)  ER is an extension of the nuclear membrane where the cell’s protein products are assembled in accordance with the genes’ instructions o Finished products are packed in a membrane and addressed in the Golgi bodies, that pass them along to the cell’s transportation network  The network is a system of tubules that carries the packaged proteins to their final destinations • Microfailments – constitute the cell’s structural framework • Microtubules – contract and aid in the cell’s movement o Two other components are important:  Mitochondria – the cell’s power plants that supply its energy needs  Lysosomes – saclike vesicles that transport incoming supplies and move and stores wastes The Cell Membrane: Barrier and Gatekeeper: - Neurons and glia are tightly packed together in the brain but like all cells, they are separated and cushioned by extracellular fluid o Composed mainly of water in which salts and other chemical substances are dissolved - Fluid is found inside a cell as well as intracellular fluid or cytoplasm o Made up mainly of water with dissolved salts and chemical but the concentrations of dissolved substances inside and outside the cell are very different  This difference helps explain the information-conducting ability of neurons Membrane Structure: - The cell membrane encases a cell and separates the intracellular from the extracellular fluid, allowing the cell to function as an independent unit o Special double-layer structure makes this separation possible, the membrane bilayer - The membrane bilayer regulates the movement of substances into and out of the cell o Also regulates the concentration of salts and chemicals on either side, because precise concentrations of chemicals within a cell are essential to its normal function - Membrane bilayer is composed of a molecule called a phospholipid that features: o A head that contains the element phosphate  Has a slight positive charge in one location and a slight negative charge in another o 2 tails that are lipid molecules  Consist of hydrogen and carbon atoms bound tightly to one another, making them electrically neutral - The differences in the electrical polarity of the head and tails of a phospholipid molecule are the underlying reason why it can form membranes o The head, being polar, is hydrophilic  Attracted to water molecules  Heads of one layer are in contact with the intracellular fluid • The heads of the other layer are in contact with the extracellular fluid o The tails, being nonpolar, is hydrophobic  Have no attraction for water  Tails of both layers point toward the inside of the bilayer, hidden from water How the Cell Membrane Functions: - The cell is impenetrable to intracellular and extracellular water because polar water molecules cannot pass through the hydrophobic tails of the membrane o Only a few small nonpolar molecules such as oxygen can pass - Since the heads of the phospholipid molecules are polar, the cell membrane can also regulate salt concentrations within the cell o Salts are molecules that separate into 2 parts when dissolved in water  One part carrying a positive charge  Other part carries a negative charge • These charged particles are collectively called ions - Proteins embedded in the cell membrane provide one way for substances such as ions to cross the membrane o They act as gates and transportation systems that allow selected substances to pass through the membrane What Do Membrane Proteins Do? - 3 categories of membrane proteins that assist in transporting substances across the membrane o Channels – membrane proteins are shaped in a way that they create channels, or holes  Different prot
More Less

Related notes for PSY100H1

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit