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Chapter 4

Chapter Four Notes

Course Code
Steve Joordens

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Chapter 4:
-nerve cells of brain are organized in modules
-modules: clusters of nerve cells that communicate with each other
-brain has three major functions
1) controlling behaviour
2) processing and retaining the information we receive from the environment
3) regulating the bodys physiological processes
-the nervous system consists of 2 divisions
1. Central Nervous System
2. Peripheral Nervous System
-the brain and the spinal cord make up the central nervous system
-the central nervous system communicates with the rest of the body through nerves
-nerves are attached to the spinal cord and base of the brain; make up peripheral
nervous system
-human brain has three major parts
1) The brain stem
2) The cerebellum
3) Cerebral hemispheres
-brain stem: primarily control of physiological functions and automatic behaviours
-cerebral hemisphere: largest part of the brain; covered by cerebral cortex and
containing parts of the brain that evolved most recently
-cerebellum: primary function is to control and coordinate movements
-brain encased in skull, and spinal cord runs through middle of vertabrae (a column of
hollow bones)
-> both brain and spinal cord enclosed by 3-layered set of membranes called
-> float in clear liquid called cerebrospinal fluid (CSF)
-blood brain barrier: make it less likely that toxic chemicals found in what we eat or
drink can find their way into the brain, where they might do damage to neurons
-cerebral cortex: outer layer of the cerebral hemispheres of the brain
-> referred to as grey matter
-> perceptions take place, memories are stores, and plans are formulated and
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-nerve cells connected to other parts of the brain by a layer of nerve fibres called white
-human cerebral cortex is full of bulges separated by grooves
-> bulges = gyri
-> large grooves = fissures
-> both expand surface area of cortex and increase the number of nerve cells it
can contain
-neurons: (nerve cells) elements of the nervous system that bring sensory information
to the brain, store memories, reach decisions, and control the activity of the muscles
-> neurons are assisted by the glia (provides support for neurons and supplies
them with some essential chemicals)
-dendrites: a tree-like part of a neuron on which other neurons form synapses
-> function principally to receive messages from other neurons
-most drugs that affect the nervous system, do so by affecting the chemical
transmission of messages between cells
-axon: caries messages away from the soma toward the cells with which the neuron
-> many axons are insulated with substance called myelin
-white matter beneath cerebral cortex gets its colour from the myelin sheaths
-myelin sheath: insulating material that encases most large axons
-> principal function of myelin is to insulate axons from one another and prevent
scrambling of messages
-action potential: abrupt, short-lived reversal in the electrical charge of an axon
-> occurs because of an unequal distribution of positively and negatively charged
particles inside axon and fluid surrounding it
-ions produced when various substances are dissolved in water
-axonal membrane contains special submicroscopic proteins that serve as ion channels
or ion transporters
-neurons communicate with other cells by means of synapses
-synapses: conjunction of a terminal button of one neuron and the membrane of
another cell
-when terminal buttons become active, they release chemical neurotransmitter
-presynaptic neuron: neuron that sends message
-postsynaptic neuron: neuron that receives message
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