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Chapter 3

PSY100H1 Chapter Notes - Chapter 3: Axon Hillock, Periaqueductal Gray, Axon Terminal


Department
Psychology
Course Code
PSY100H1
Professor
Michael Inzlicht
Chapter
3

Page:
of 38
Module 3.2 How the Nervous System Works: Cells and Neurotransmitters
- A bite from an Australian snake species can kill an adult human in 30 mins
o Most lethally venomous snake
o The venom of the taipan is neurotoxic
o Neurotoxic: something that specifically attacks cells of the nervous system
o Since networks of nervous system cells are essential for all types of functions such as
breathing, an attack on these cells is very dangerous
o People who get bitten go through some real shit. Drowsinessdifficulties controlling
head and neck musclesdifficulty swallowingtightness of chestbreathing
paralysiscomadeath
o Not all snake venoms attack the nervous system
The venom in most rattlesnakes in North America is not neurotoxic
- Cells (especially nervous system cells) play an important role in almost everything you do:
o Moving
o Sensing
o Thinking
o Feeling
Neural Communication
- Human body is composed of many different cells
- Psychologists are most interested in neurons
o Neurons: one of the major types of cells found in the nervous system, that are
responsible for sending and receiving messages throughout the body
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find more resources at oneclass.com
The Neuron
- Primary purpose: to fire
o To receive input from one group of neurons and to then transmit that information to
other neurons
- Single neurons work together as part of networks involving thousands-millions of other cells
o These networks lead to some type of behavior to occur
- There are parts of neurons that are specialized for receiving incoming info from other neurons
AND
- There are parts of the cell specialized for transmitting information to other neurons
- All neurons have a cell body
o Cell body (AKA soma): the part of a neuron that contains the nucleus that houses the
ell’s geetiateial
o Genes in the cell body synthesize proteins that form other chemicals and structures
that allow the neuron to function
- The activity of genes within the cell can be influenced by the input that is coming from other
cells
o This input is received by dendrites
Dendrites: small branches radiating from the cell body that receive messages
from other cells and transmit those messages toward the rest of the cell
- At any point, a neuron will receive input from several other neurons
o These impulses from other cells will travel across the neuron to the base of the cell
body, called the axon hillock
o If the axon hillock receives enough stimulation from other neurons, it will initiate a
chemical reaction that will flow down the rest of the neuron
- This chemical reaction is the first step in a neuron communicating with other cells (i.e.
influencing whether other cells will fire or not)
- The activity will travel from the axon hillock along a tail-like structure that protrudes (projects)
from the cell body
o This structure is called the axon
o Axon: transports information in the form of electrochemical reactions from the cell
body to the end of the neuron
o When the activity reaches the end of the axon, it will reach axon terminals
Axon terminals: bulb-like extensions filled with vesicles
Vesicles: little bags of molecules
The vesicles contain neurotransmitters
o Neurotransmitters: the chemicals that function as messengers
allowing neurons to communicate with each other
The impulse travelling down the axon will stimulate the release of
neurotransmitters and thus allowing for neural communication to
occur
There are different types of neurotransmitters
- Not all neurons perform the same function
o Sensory neurons: receive information from the bodily senses and bring it toward the
brain
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find more resources at oneclass.com
Neurons that respond to touch or pain sensations of the skin and bring the
message back toward the spinal cord and brain
o Motor neurons: carry messages away from the brain and spinal cord and toward
muscles in order to control their flexion and extension
- Within the brain itself, neurons function differently
o Some cells have few/if any dendrites extending from the cell body
These cells do not perform tasks requiring a lot of interactions with other
neurons
o Oppositely, some neurons have huge branches of dendrites
They perform functions involving a lot of communication among neurons
- Basically, all these differences are for a reason (not just random)
- THE PHYSICAL STRUCTURE OF A NEURON IS RELATED TO THE FUNCTION IT PERFORMS
Myths in Mind (We Are Born with All the Brain Cells We Will Ever Have)
- For years, scientists believed that nerves do not regenerate. Scientists believed that we are
born with all of the brain cells we will ever have
find more resources at oneclass.com
find more resources at oneclass.com