PSYCH 1XX3 Final: Neuroscience I
14 Jul 2018
School
Department
Course
Professor
Neuroscience I
Introduction
• Electrochemical events in the CNS influence thought, perception, and memory, meaning that we
do not have direct experience of the world around us (millions of combinations of neuronal
activities are possible)
o Ex. We are not feeling the warmth of the sun or the grass but we are experiencing events
triggered by environmental stimuli
• To become aware, the world induces patterns of activity in the brain that we become aware of and
not the world
• Structural questions are asked: what is the brain made of, constructed with, and connected?
o We need structural AND functional information to understand the brain
• The brain is not that big and makes about 2% of body weight, but burns a lot of energy and
oxygen supply
• There are 2 types of cells found in the brain that work together:
o Glial cells – give structure and do housekeeping tasks like nourishment and insulation
(higher frequency)
o Neuron (specialized for communication) – form connections with other neurons to
perform functions
• Reductionism Problem – neurons are not the most basic possible level of explanation for social
behaviours as each neuron is composed of organelles
Consciousness and Awareness
• Mind-Body Problem - Rene Descartes was a dualist and said that mental processes of the mind
are separate from the brain’s physical processes (mind controls actions and thoughts / physical
brain connects the mind and body)
o The soul was in the pineal gland and affected control of the body through nerves
• There have not been successful challenges that it is impossible for the mental state of a person to
change without physical change in the brain (now we want to know how the brain produces the
mental processes of the mind)
Case Study - Neuroscience Explains the Different Behaviours of
Siblings
• Jill is careful, eats right, exercises, and does not put herself in harm’s way
• She was eating yogurt past the expiry date (her kind of danger) and gets a call from bro Phil who
is skydiving
• Understanding the brain’s function at a cellular and systems level helps us understand motivation
and behaviour
Neural Anatomy
• Neurons are organized into signaling pathways to communicate through synaptic transmissions
• A neuron has 2 zones: receptive zone to receive signals, and transmission zone to pass on signals
to other neurons
• Receptive zone – made up of branching dendrites
o Begins with cell body which has the organelles that keep the cell functioning
o Dendrite projections reach out to other neurons and receive signals to be relayed through
the dendritic branch to the cell body where signals go on to be conveyed down the axon
• Transmission zone – made of axon and terminal ends
o Signal passes down the long axon fiber to the branching terminal boutons which reach
out to connect with the receptive zone of nearby neurons to transmit the signal further
The Cell Membrane
• Is selectively permeable and preferentially allows different ions to pass through with various
levels of ease
• Contains proteins channels for passage of ions
• Selective movement of ions across the membrane into and out of the neuron is critical for neural
communication
The Central and Peripheral Nervous Systems
• Central Nervous System (CNS) – brain (skull) and spinal cord (vertebral column) encased in bone
o The brain weighs 1.3 kg and is a large mass of neurons (fundamental building block of
NS) and glia cells
• Peripheral Nervous System (PNS) - remaining nerve tissue and peripheral ganglia (small groups
of neuron cell bodies) located outside the CNS
o PNS is divided into 2 parts based on their function: SNS and ANS
• Efferent Nerve Fibers – carry info from CNS to PNS (ex. Bite, chew, swallow)
• Afferent Nerve Fibers – carry info from PNS to CNS (ex. Touch, positions, pain, temperature)
The Somatic and Autonomic Nervous Systems
• Somatic Nervous System (SNS) – receives sensory info from sensory organs and controls
voluntary movement of muscles, gives us conscious control (we are aware)
• Autonomic Nervous System (ANS) – controls things outside of conscious awareness and control
o Ex. Regulates smooth muscles (contracts blood vessels/pupil/gastrointestinal tract/
uterus), cardiac muscle, operates glands
o Divided into 2 systems: SD and PS
o 1. Sympathetic Division (SD) – prepares body for emergencies (fight or flight response),
causes increase in heart rate, dilation of pupils and internal lung structures, inhibition of
pee/poo/digestion
▪ These responses must occur together as nerves reach organs together and this
system releases adrenaline from the adrenal gland into the blood so the response
reaches organs that are not directly connected to the nerves
o 2. Parasympathetic System (PS) - opposite to SD, slows heart, lowers BP, contracts
pupil, increase activity in gastrointestinal tract and pee
▪ These responses return body functions to normal after activation of SD, and
conserve and increase body energy resources
The Neuron
• Eukaryotes – body cells have complex internal structures (organelles) with specific roles
o Each cell has a cell body or soma that is surrounded by a membrane separating it from
other cells
o Nucleus with DNA, mitochondria, ribosomes are found in cells that make the things
needed for operation
• Neuron – integrates, communicates info, has adaptations to process & transmit info via
electrical/chemical signals
The Neuron - Structure of the Neuron
• Dendrites – receive and integrate incoming info
o Converge at the cell body and receive impulses from other neurons
• Axons – pass info to other cells
o 1 axon exits the cell body and can extend for long distances, branches to carry impulse to
its destination
o The destination at the end of the axon can be a neuron or muscle/ gland capable of
receiving and responding to a nerve impulse (these are known as effectors)
The Neuron - The Dendrite
• Branched projections that conduct nerve impulses received from other cells to the cell body are
short
• Covered in tiny spines on which the connections from axons of other neurons are made at a
synapse
• Bring together impulses occurring at synapses (200,000) to their destination at the cell body
The Neuron - The Cell Body
• Cell body or soma is small, (4 microns) for the smallest neuron (granule cell), (100 microns) for a
motor neuron
• Proteins that participate in the metabolism of the cell are synthesized from the DNA templates in
the nucleus
• Axon Hillock – elongated portion from which the axon exits the cell body
The Neuron - The Axon
• Leaving the cell body is a long, narrow tube carrying info to the ends of the axon to the terminal
boutons
• Terminal Boutons – end terminals where connections to dendrites of nearby neurons are made
• Action Potential – message carried by the axon
• Myelin sheath – surrounds the axon, fatty tissue, part of glial cell, insulates the axon from other
axons
• Myelin – speeds up the conduction of the action potential along the axon
• White matter – makes up more than half of the brain volume and is composed mostly of
myelinated axons
• The longest axon runs from the spine to the toe through the sciatic nerve
• Nerves are large bundles of axons
o Ex. The trigeminal nerve – responsible for movement and sensation in the face and head
contain 150,000 axonal fivers of which they are mostly afferent fibers
Neuron Subtypes
• Different neurons adapt to perform different tasks in the nervous system
• Sensory neurons – info from the environment (ex. Sound/light/taste/touch) gathered by receptors
and sent to NS
Document Summary
Introduction: electrochemical events in the cns influence thought, perception, and memory, meaning that we do not have direct experience of the world around us (millions of combinations of neuronal activities are possible, ex. Case study - neuroscience explains the different behaviours of. The central and peripheral nervous systems: central nervous system (cns) brain (skull) and spinal cord (vertebral column) encased in bone, the brain weighs 1. 3 kg and is a large mass of neurons (fundamental building block of. Bite, chew, swallow: afferent nerve fibers carry info from pns to cns (ex. Regulates smooth muscles (contracts blood vessels/pupil/gastrointestinal tract/ uterus), cardiac muscle, operates glands: divided into 2 systems: sd and ps, 1. Parasympathetic system (ps) - opposite to sd, slows heart, lowers bp, contracts pupil, increase activity in gastrointestinal tract and pee: these responses return body functions to normal after activation of sd, and conserve and increase body energy resources.
