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Lecture 3

Lecture 3 [ Notes ].docx

Course Code
PSYC 1010
Gerry Goldberg

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Cells in the Nervous System
o Neurons
o Basic links that permit communication within the nervous system
o Soma: contains cell nucleus and much of the normal chemical machinery
o Dendrites: specialized to receive information
o Axon: long, thin fibre that transmits signals away from the soma to other neurons or to
muscles or glands
o Myelin sheath: insulating material that encases some axons
o Terminal buttons: small knobs that secrete neurotransmitters
o Synapse: junction where information is transmitted from one neuron to another
o Glia
o Account for over 50% of brain’s volume
o Supply nourishment to neurons, help remove neurons’ waste products, and provide
insolation around many axons
o They also orchestrate the development of the nervous system in the human embryo
o Can also send and receive chemical signals
o Play important role in memory formation and the experience of chronic pain
The Neural Impulse
o All-or-None Law: the action being made has to fully happen or not happen at all. The action
cannot half-happen, just like you can’t half-fire a gun. However, you can change the rate at
which the action happens
Cell-Cell Communication
o Synaptic cleft: microscopic gap between terminal button of one neuron and cell membrane of
the other
o Neurotransmitters: chemicals that transmit information from one neuron to another
o Two kinds of messages sent from cell to cell
o Excitatory PSP: positive voltage shift that increases the likelihood that the postsynaptic
neuron will fire action potentials
o Inhibitory PSP: negative voltage shift that decreases the likelihood that the postsynaptic
neuron will fire action potentials
Integrating Signals: Neural Networks
o Synaptic pruning: key process in the formation of the neural networks that are crucial to
communication in the nervous system
Neurotransmitters and Behaviour
o Acetylcholine
o Found throughout the nervous system
o Only transmitter between motor neurons and voluntary muscles
o Contributes to attention, arousal, and memory
o Agonist: chemical that mimics the action of a neurotransmitter
o Antagonist: chemical that opposes the action of a neurotransmitter
o Monoamines
o Include three neurotransmitters: dopamine, norepinephrine, and serotonin
o Dopamine is used by neurons that control voluntary movements
o Serotonin controls the regulation of sleep and wakefulness and eating behaviour
o GABA and Glutamate (amino acid transmitters)
produce only inhibitory postsynaptic potentials
widely distributed in the brain
responsible for the inhibition in the central nervous system
contributes to anxiety in humans
o glutamate
always has excitatory effects
contribution to learning and memory
o Endorphins
o Internally produced chemicals that resemble opiates in structure and effects
o All over the body
o Contribute to modulation of pain
Organization of the Nervous System
Peripheral NS
o Made up of all the nerves that lie outside the brain and spinal cord
o Somatic NS
o Made up of nerves that connect to voluntary skeletal muscles and to sensory receptors
o Require to nerve fibres
Afferent: axons that carry information inward to the central nervous system
from the periphery of the body
Efferent: axons that carry information outward from the central nervous system
to the periphery of the body
o Autonomic NS
o Made up of nerves that connect to the heart, blood vessels, smooth muscles, and glands
o Controls automatic, involuntary, visceral functions
o Two branches:
Sympathetic: branch that mobilizes the body’s resources for emergencies
Parasympathetic: branch that generally conserves bodily resiurces
Central Nervous System
o Consists of the brain and spinal cord
o Cerebrospinal fluid: nourishes the brain and provides a protective cushion for it
o Spinal cord
o Connects the brain to the rest of the body through the peripheral nervous system
o Enclose by meninges and bathed in CSF
o Extension of the brain
o Has many axons that carries the brain’s commands to peripheral nerves and relay
sensations from periphery to brain
o Brain
o Contains billions of interacting cells
o 1.5 kg
Research Methods
o EEG (electroencephalograph): device that monitors the electrical activity of the brain over time
by means of recording electrodes attached to the surface of the scalp
o Lesioning:
o involves destroying a piece of the brain
o Done by inserting an electrode into a brain structure and passing a high-frequency
electric current through it to burn the tissue and disable the structure
o Stereotaxic instrument: device used to implant electrodes at precise locations in the
o ESB (electrical stimulation of the brain)
o Involves sending a weak electric current into a brain structure to stimulate it
o Most of this research is conducted with animals
o Transcranial Magnetic Stimulation
o New technique that permits scientists to temporarily enhance or depress activity in a
specific area of the brain
o Magnetic coil on a small paddle is held over an area of a subject’s head. This creates a
magnetic field that penetrates down 2 cm.
o By varying the timing and duration of the magnetic pulses, a researcher can either
increase or decrease the excitability of neurons in the local tissue
o Brain-imagine Procedures
o CT (Computerized Tomography): computer-enhanced x-ray of brain structure
o PET (position emission tomography): can examine brain function. Radioactively tagged
chemicals are introduced into the brain.
o MRI: (magnetic-resonance image): uses magnetic fields, radio waves, and computerized
enhancement to map out brain structure.
o fMRI: monitors blood flow and oxygen consumption in the brain to identify areas of high activity
The Brain and Behaviour
o Hindbrain