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Chapter 4

PSYA01H3 Chapter Notes - Chapter 4: Nuda, Myelin, Neurotransmitter

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Aqdas Qasem
Intro to Psychology I Textbook Notes
Chapter 4 Biology of Behaviour
The Brain and its Components (Part 1 page 89)
- There are different types of nerve cells, in terms of shape, size, and the kinds of chemicals they
- Different parts of the nervous system are responsible for different functions.
- Donald Hebb considered how individual nerve cells are organized into larger units, and they units
can generate the higher processes of the brain (i.e. memory, thought, and decision making).
- Nerve cells of the brain are organized in modules clusters of nerve cells that communicate with
each other.
- Individual modules do not stand alone, they are connected to other neural circuits, receiving
information from some of them, processing this information, and sending the results to other
modules. Specific modules have specific functions.
Structure of the Nervous System
- The brain has three major functions: controlling behaviour, processing and retaining information
we receive from the environment, and regulating the body’s physiological processes.
- Brain needs to receive information from the body’s sense receptors, and it must be connected with
the muscles and glands of the body if it is to affect behaviour and physiological process; the brain
cannot act alone.
- Nervous system consists of two divisions:
- Central Nervous System: which the brain and spinal cord make up.
- The spinal cord is a long, thin collection of nerve cells attached to the base of the brain and
running the length of the spinal column.
- The spinal cord has a circuit of nerve cells that control some reflexes (i.e. moving your hand away
when it gets burned).
- The central nervous system communicates with the rest of the body through nerves bundles of
fibres that transmit information in and out of the central nervous system.
- The peripheral nervous system is made up of the nerves that connect the spinal cord to the
base of the brain.
- Sensory information (about the internal and external environment) is conveyed from sensory
organs to the brain and spinal cord.
- The cranial nerves send information from the head neck region to the brain.
- Sensory information from the rest of the body reaches the spinal cord (and ultimately the brain)
through spinal nerves.
- These two types of nerves also carry information to the central nervous system.
- The human brain has three major parts: brain stem, cerebellum, and the cerebral hemispheres.
- The brain stem is one of the primitive regions of the brain, and its functions are correspondingly
basic ones: primarily control of physiological functions and automatic behaviours.
- The pair of cerebral hemispheres constitutes the largest part of the brain.
- This part of the brain contains the part of the brains that evolved most recently and thus are
involved in behaviours of particular interest to psychologists.
- The cerebellum (attached to the back of the brain stem) looks like a miniature version of the
cerebral hemisphere. Its primary function is to control and coordinate movements.
- The brain is encased in the skull, and the spinal cord runs through the middle of a column of hollow
bones known as vertebrae.

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Aqdas Qasem
Intro to Psychology I Textbook Notes
Chapter 4 Biology of Behaviour
- The brain and spinal cord are enclosed by a three-layered set of membranes called meninges
(single form is meninx).
- The brain and spinal cord float in a clear liquid called cerebrospinal fluid (CSF).
- The liquid fills the space between two of the meninges, therefore providing a liquid cushion
surrounding the brain and spinal cord and protecting them from being bruised by the bones that
encase them.
- Cells of the body receive water and nutrients through capillaries.
- In most of the body, the capillaries have openings that let chemicals pass freely from the blood into
the surrounding tissues.
- The capillaries in the brain do not have these openings for fewer substances can pass from the blood
to the brain this barrier of exchange of chemicals is called blood-brain barrier. Its major function
is to make it less likely that toxic chemicals found in what we eat or drink can find their way into the
brain, where might do damage to the neurons. The barrier is not foolproof; there are many poisons
that can affect the brain.
- The surface of the cerebral hemisphere is covered by the cerebral cortex consists of a thin layer
of tissue approximately 3mm thick and is often referred to as grey matter because of its
- Perceptions take place in the cerebral cortex, memories are store and plans are formulated and
- The nerve cells in the cerebral cortex are connected to other parts of the brain by a layer of nerve
fibres called white matter because of the white appearance of the substance that insulates them.
- The bulges in the brain are called gyri and the large grooves are called fissures.
- The gyri and fissures increase the surface area of the brain, allowing there to be more in less.
- Peripheral nervous system consists of the nerves that connect the central nervous system (CNS)
with sense organs, muscles, and glands.
- Sense organs detect change in the environment and send signals via nerves to the CNS. The brain
sends signals via nerves to the muscles (causing behaviour) and the glands (producing adjustments
in internal physiological processes).
Cells of the Nervous System
- Neurons (nerve cells) are the elements of the nervous system that bring sensory information to the
brain, store memories, reach decisions, and control the activity of the muscles.

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Aqdas Qasem
Intro to Psychology I Textbook Notes
Chapter 4 Biology of Behaviour
- Neurons contain structures specialized for receiving, processing, and transmitting information to
other neurons.
- Nerves are assisted in their function by another kind of cell called the glia they hold neurons in
place and during development of the brain, some types of glial cells form long fibres that guide
developing neurons from their place of birth to their final resting places. They also manufacture
chemicals that neurons need to perform and absorb chemicals that might impair neurons
functioning. They also form protective insulating sheaths around nerve fibres and also serve as the
brains immune system.
- Dendrites (tree-like branches as the end of a nerve cell) receive messages from other neurons.
- Dendritic spines (small protuberances on the surface of dendrites) appear on neurons in the
- The soma (cell body) is the largest part of the neuron and contains the mechanisms that control the
metabolism and maintenance of the cell. Somas can also receive messages from other neurons.
- The axon carries messages away from the soma toward the cells with which the neuron
- These messages, action potentials, consist of brief changes in the electrical charge of the axon.
- Axons end in terminal buttons, which are located at the end of the twigs” that branch off from
their ends.
- Terminal buttons rest against dendrites, dendritic spine, the soma, or the axon of another neuron.
- Terminal buttons secrete a chemical called neurotransmitter whenever an action potential is sent
across the axon.
- Neurotransmitters affect the activity of other cells with which the neuron communicates.
- Most axons (especially long ones) are insulated with a substance called myelin. White matter
located beneath the cerebral cortex gets its colour from the myelin sheaths which are around the
- Myelin is part protein and part fat, produced by glial cells. They leave small bare patches of axon
between them.
-Myelin insulates the axon, preventing the scrambling messages and also increases the speed of the
action potential.
-People with multiple sclerosis (a neurological disease) attack a protein in myelin sheath and
although most axons survive, they can no longer function properly.
The Excitable Axon: The Action Potential
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