PSY 4791 Lecture Notes - Sympathetic Nervous System, Speech Perception, Mania

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31 Jan 2013
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Brain stem – most primitive regions of brain, and its functions are basic ones
– control of physiological functioning and automatic behaviour (amphibeans
have brain stem and simple cerebellum)
cerebral hemispheres – constitue large portion of brain
contains parts of brain that evolved most recently: involved in behaviours of
particular interest to psychology
cerebellum – attached to bain of brain, looks like miniature version of cerebral
hemispheres
functions are control and coordination of posture and movement, especially
rapid ones
brain is encased in skull and spinal cord runs through middle of hollow bones
(vertebra: vertebral column)
both brain and spinal cord are enclosed in 3 layered set of membrane called
meninges
float in clear liquid called cerebrospianl fluid (CSF)
fills between 2 meninges, providing cushioning
cerebral cortex – outer layer of cerebral hemisphere of brain, approxiamtely
3 mm thick
often referred to as grey matter – contains billions of nerve cells
(abundant in nerve cell bodies rather than axons)
where perceptions take place,memories are stored, plans are formulated
and executed
nerve cells in cerebral cortex are connected to other parts of brain by layer
of nerve fibres called white matter
shiny white appearance of substance that coats and insulates axons that
travel trough area (axons' myelin sheath)
very wrinkled appearance – full of bulges seperated by grooves
bulges – gyri
grooves – fissures
they expand amount of surface are of cortex and greatly increase
number of nerve cells – more complex the brain, larger cortex
Peripheral nervous system – consists of nerves that connect central nervous
system with sense organs, muscles and glands
nerves carry incoming and outgoing information
sense organs detect changes in environment and send signals
throughnerves to central nervous system
brain sends signals trhough nerves to muscles (causing behaviour) and
glands (producing adjustments in internal physiological processes)
nerves – bundles of many thousands of individual fibres all wrapped in tough,
protective membrane (look like table clothes)
nerve fibres transmit message through nerve, from sense organ to brain or
from brain to muscle/gland
these make up white matter and other axon tracts
some attached to spinal cord and others to brain
spinal nerves – bundle of nerve fibres attached to spinal cord; conveys
sensory information from body and carries mesages to muscles and
glands
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cranial nerves – 12 pairs, attached to base of brain; conveys sensory
information from face and head and carries messages to muscles and
glands
Cells of Nervous System
Neurons – nerve cell; consists of cell body with dentrites and an axon whose
branches end in terminal bittons that synaps to muscle fibres, gland cells, or
other neurons
elements of nervous system that bring sensory information to brain, store
memories, reach decisions, control activity of muscles
assisted by glia
Glial cells – cell of central nervous system that provides support for neruons
and supplies them with essential chemicals
during development of brain, some types of glial cells form long fibres that
guide develping neurons from place of birth to final resting place
manufacture chemicals that neurons need to perform tasks and absorb
chemicals that might impair neuron's functioning
form protective insulating sheaths around nerve fibres
serve as brain's immune system, protecting it from micro-organisms
Three basic parts of neruron:
soma – cell body; largest part of neuron
containts mechanisms that control metabolism and maintenance of cell
receives messages from other neurons
dentrites – treelike part of neuron on which other neurons form synapses
transmit information they receive down trunks to soma
axon – long,thin part of neuron attached to soma; divides into a few or
many branches, ending in a terminal button
carries message away from soma toward cell with which neuron
communicates – action potential (brief changes in electrical charge) also
referred to as firing of an axon
Two complex structures seen in neurons:
dentritic spines – small protuberance on surface of dentrite; appear on
neurons in brain
synapse can occur on smooth dentrite or on dentritic spine
terminal button – round swelling at end of axon; releases transmitter
substance
connect to dentrites, dentritic spine, soma, and axon on other neuron
secrete transmitter substance/neurotransmitter (chemical that causes
postsynaptic neuron to be excited or inhibited) whenever AP travels
down axon
many axons insulated with myelin sheath
myelin – part protein, part fat
produced by glial cells that individually wrap themselves around
segments of axon
insultates axons from each other and prevents scrambling of messages
increases speed of AP
multiple sclerosis – immune system attack protein in myelin and so suffer
from various sensory and motor impairments
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The Action Potential
travels less than 100 m/second
membrane of axon is electrically charged – at rest is -70 milivolts with respect
to outside
action potential – brief electrochemical event that is carried by an axon from
soma of neuron to its terminal button; causes release of transmitter signal
unequal distribution of + or - charge occurs inside axon and in fluid that
surrounds it
axon membrane contains ion channels – special protein molecule located
on membrane of cell which controls entry or exit of particular ion
ion transporters – special protein moelcule located in membran of cell
taht actively transports ions into or out of cell
use energy resource from cell to acituvely pump
outside of membrane is + charged and inside is – charged
when axon is resting, ion channels are closed
AP is caused by opening of some ion channels in membrane at end of axon
near soma – opening permits + charged sodium ions to enter, which reverses
membrane potential at that location causing nearby ion channels to open,
producing reversal at that point too – prossess continues all way down to
terminal button
as soon as charge reverses, ion channels close and another set opens letting +
charged potassium ions out of axon – restores normal charge
ion transporters pump sodium back out of cell and potassium back in
Synapses
synapse – junction between terminal button of one neuron and membrane of
muscle fibre, gland, or other neuron
terminal button belongs to presynaptic neuron and sends out message
(neurotransmitter) to postsynaptic neuron
motor neuron – neuron whose terminal button forms synapse with muscle
fibres; when AP travels down its axon, associated muscle fibres with twitch
Two types of synapses:
excitatory – transmitter signal excites postsynaptic neuron increasing
chances it will fire too
inhibitory – transmitter signal inhbits postsynaptic neuron decreasing
chances it will fire
when AP reaches terminal button, it causes terminal button to release small
amount of transmitter substance into synaptic cleft (fluid-filled gap between
pre- and postsynaptic neuron)
reactions are triggered by special submicroscopic protein molecules embedded
in postsynaptic membrane called receptor molecules (receptors that respond
to opiates are sometimes found elsewhere on surface of neuron)
once activated, receptor molecules produce excitatory or inhibitory effects of
postsynaptic neuron – open ion channels
excitatory – sodium channels open and Na+ moves in
inhibitory – potasssium channels open and K+ moves in
reuptake – process by which terminal buttom retrieves molecules of
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