Chapter 3: Neuroscience 1
Physiological Activity of the Brain: When you’re ‘experiencing’ your General Structure of Cells: Fairly complex internal structure
environment, you’re actually experiencing a series of events in your ● Soma: Cell body surrounded by membrane separating it
CNS, which were set in motion by stimuli in the environment, not the from other cells
environment itself ○ Soma of a neuron = quite small (4 microns for the
Mind-Body Problem: Our widespread belief that our mind is smallest type of neuron/granule cell, up to about
somehow separate from our physical nature due to irreconcilable 100 microns for a motor neuron in the spinal cord)
differences between things like thoughts, memories, sensations and ● Nucleus: Within soma, contains the DNA that regulates
the physical operation of our bodies much of the cells operation + various other
● First philosopher to discuss it was René Descartes, a dualist membrane-bound organelles (ie. mitochondria and
who suggested that the body was like a machine that ribosomes)
followed the laws of physics, and was distinct from the ● Organelle: Act as chemical factories, responsible for
mind, which was a non-physical entity that did not follow synthesizing various substances needed for the operation of
physical laws, he also believed that the seat of the soul was the cell, each of these cell types are specialized
in the pineal gland and it somehow affected control of the Neuron: Cell that specializes in integrating + communicating info +
body through the nerves has a number of special adaptations that allow it to process + transmit
● Modern update to this framework would be to consider the info via electrical and chemical signals
brain as the hardware that is driven by the software of the ● Cell Body: Carries genetic info, maintains structure, and
mind provides energy to keep the neuron functioning
Central Nervous System: Brain + spinal cord (both encased in bone) ● Dendrites: Special structures dedicated to receiving +
● Brain: 2% total body weight but consumes around 20% of integrating incoming info
our oxygen intake when we are at rest (vast majority of this ○ Branching dendrites receive impulses from many
energy is expended on the energetic needs of the neurons) other neurons + bring them together/converge at
● Brain = contained within skull the cell body
● Spinal cord = encased within vertebral column ○ Branched projections that conduct the nerve
● Two basic cell types in the brain impulses received from other cells to the cell body
○ Glial cells: Provide structural support, are fairly short (extending only a few hundred
nourishment, insulation needed by neurons and microns away from the cell)
perform various ‘housekeeping’ tasks in the brain ■ They are covered in tiny spines on
○ Neuron: Most important elementary unit in your which the connections from the axons of
nervous system, specialized for communication other neurons are made at a junction
■ Outnumbered by glial cells by a fairly known as a synapse
large margin ■ Some neuron types have up to 200,000
■ About 100 billion neurons in the synapses, although 1,000-10,000
average adult human brain synapses per neuron is more typical
■ Perform the more interesting functions ● Axon: Pass info received by dendrites onto other cells by
■ Form synapses (ie connections) to passing it from the cell body through a long narrow fibre
thousands of other neurons, resulting in tube to the ends of the axon where the terminal boutons/ends
a brain with about a thousand trillion (look like little feet) are located as this is where connections
different connections to the dendrites (receptive zones) of other nearby neurons
■ Receptive Zone: Designed to receive are made
signals from other neurons ○ Usually one axon exits the cell body and can
■ Transmission Zone: Designed to pass on extend for long distances, even the entire length of
signals to other cells the spinal cord, and may branch multiple times to
carry the neuron's impulses to multiple
destinations
○ At the end of the axon, the destination of the
neuron's impulse might be another neuron, or
some other cell such as a muscle/gland capable of
receiving + responding to a nerve impulse (known
as effectors)
■ Short axons = 1-3 mm
■ Longest axons = 1 metre (extend from
base of the spine to the bottom of your
feet through the sciatic nerve)
■ Action Potential: Basic message carried
by the axon
■ Myelin Sheath: A tube of fatty tissue
that surrounds the axon, part of a glial
cell, serves to insulate the axon from
other axons + speeds up the conduction
of the action potential along the axon
, Chapter 3: Neuroscience 1
■ ‘White Matter’ of the Brain: Makes up ● Ions involved in generating resting potential:
more than half of the brain volume, is
composed mostly of a vast number of
myelinated axons
○ A- = Amino/organic ions that exist only on the
inside of the cell
○ Analogy: Salty banana— Na+ = outside, K+ =
inside
● Protein Channels: Act as passageways for ions to pass
Sequence of Activity in a Neuron: Info flows from the dendrites
through
(where info is gathered) → cell body (where info from all the multiple
● Two types of K+ channels:
dendrites is integrated) → down along the axon → other neurons
○ Leak K+ Channel: Always open, allows K+ to
(where complex calculations can occur) / effector cells (where the info
pass through the cell membrane out of the neuron,
is acted upon, ie heart beating faster)
however, much of the K+ remains inside the cell
Neuron Subtypes: Different kinds of neurons adapted to performing a
at rest, major contributor to maintaining the
different task within the nervous system
resting potential
● Sensory Neurons: Info from the environment (ie. sound,
○ Voltage-Gated K+ Channel: An important player
taste, touch) is gathered from the various receptors and sent
for driving the action potential
inwards towards the rest of the nervous system by sensory
● Ion concentrations are the result of the balance between two
neurons, sometimes specialized for gathering info directly
opposing forces:
from the environment (ie. cells responsible for sensing
○ Electrostatic Pressure: Forces of attraction +
pressure on the surface of the skin)
repulsion
● Effector Neurons: Activate the muscles of the body,
■ In areas with too many positive or
controlling movement, most common = motor neurons
negative ions, electrostatic pressure will
which have their cell bodies within the spinal cord + have
cause the ions to move from these areas
long axons that extend out to terminals attached to the
to areas with no net charge
individual muscle cells, nerve impulse/action potential
○ Diffusion: Force that moves molecules from areas
conducted from the motor neuron along its axon will cause
of high to low concentration
the associated muscle to contract
● Balance of Forces: Cell membrane acts as the barrier
● Interneurons: Vast majority of the neurons in the nervous
between the two compartments + the forces of electrostatic
system, come in a number of different varieties, each with
pressure and diffusion balance the relative concentrations of
different dendrite + axon sizes/shapes, most common =
the ions
multipolar neurons, comprised of multiple dendrites
○ The organic anions A- are trapped inside of the
extending from the cell body and only a single axon
cell, being unable to pass through the membrane
○ The bipolar neuron has only a single dendrite
○ K+ ions = higher concentration in cell
exiting one side of the cell body with a single
■ Diffusion = pushes them out
axon exiting the other (usually sensory neurons
■ Electrostatic Forces = attracts them in
whose dendrites terminate at receptor cells)
■ Therefore two forces balance and K+
○ The unipolar neuron has only a single dendrite
stays more or less where it is
leaving the cell body which eventually branches in
○ Cl- ions = higher concentration outside of cell
two directions, one towards the dendrites and the
■ Diffusion = pulls them inside
other along an axon
■ Electrostatic Forces = pushes them
Microelectrode: A small recording device inserted through the cell
outside
membrane into the intracellular fluid to study how action potentials
■ Therefore two forces balance and Cl-
work
stays more or less where it is
● Records the electrical potential/voltage across the cell
○ Na+ = higher concentration outside of cell
membrane and how this voltage changes across time as the
■ Diffusion = pulls them inside
action potential occurs
■ Electrostatic Forces = pulls them inside
Resting Potential: Even when the neuron is at rest there is a constant
■ Two forces are NOT in balance
electrical potential across the membrane (-70 mV)
○ The cell membrane is not very permeable to Na+
● The intracellular fluid of the cell is more negative than the
molecules
outside of cell (like a battery) due to an excess of positive
ions outside of the cell ■ Voltage gated sodium channels are
closed in the resting state of the neuron
● Cell membrane = selectively permeable (preferentially
and so the positively charged sodium
allows different ions to pass through it with various levels of
ions flow into the cell in only very low
ease)
concentrations, and only through other
Physiological Activity of the Brain: When you’re ‘experiencing’ your General Structure of Cells: Fairly complex internal structure
environment, you’re actually experiencing a series of events in your ● Soma: Cell body surrounded by membrane separating it
CNS, which were set in motion by stimuli in the environment, not the from other cells
environment itself ○ Soma of a neuron = quite small (4 microns for the
Mind-Body Problem: Our widespread belief that our mind is smallest type of neuron/granule cell, up to about
somehow separate from our physical nature due to irreconcilable 100 microns for a motor neuron in the spinal cord)
differences between things like thoughts, memories, sensations and ● Nucleus: Within soma, contains the DNA that regulates
the physical operation of our bodies much of the cells operation + various other
● First philosopher to discuss it was René Descartes, a dualist membrane-bound organelles (ie. mitochondria and
who suggested that the body was like a machine that ribosomes)
followed the laws of physics, and was distinct from the ● Organelle: Act as chemical factories, responsible for
mind, which was a non-physical entity that did not follow synthesizing various substances needed for the operation of
physical laws, he also believed that the seat of the soul was the cell, each of these cell types are specialized
in the pineal gland and it somehow affected control of the Neuron: Cell that specializes in integrating + communicating info +
body through the nerves has a number of special adaptations that allow it to process + transmit
● Modern update to this framework would be to consider the info via electrical and chemical signals
brain as the hardware that is driven by the software of the ● Cell Body: Carries genetic info, maintains structure, and
mind provides energy to keep the neuron functioning
Central Nervous System: Brain + spinal cord (both encased in bone) ● Dendrites: Special structures dedicated to receiving +
● Brain: 2% total body weight but consumes around 20% of integrating incoming info
our oxygen intake when we are at rest (vast majority of this ○ Branching dendrites receive impulses from many
energy is expended on the energetic needs of the neurons) other neurons + bring them together/converge at
● Brain = contained within skull the cell body
● Spinal cord = encased within vertebral column ○ Branched projections that conduct the nerve
● Two basic cell types in the brain impulses received from other cells to the cell body
○ Glial cells: Provide structural support, are fairly short (extending only a few hundred
nourishment, insulation needed by neurons and microns away from the cell)
perform various ‘housekeeping’ tasks in the brain ■ They are covered in tiny spines on
○ Neuron: Most important elementary unit in your which the connections from the axons of
nervous system, specialized for communication other neurons are made at a junction
■ Outnumbered by glial cells by a fairly known as a synapse
large margin ■ Some neuron types have up to 200,000
■ About 100 billion neurons in the synapses, although 1,000-10,000
average adult human brain synapses per neuron is more typical
■ Perform the more interesting functions ● Axon: Pass info received by dendrites onto other cells by
■ Form synapses (ie connections) to passing it from the cell body through a long narrow fibre
thousands of other neurons, resulting in tube to the ends of the axon where the terminal boutons/ends
a brain with about a thousand trillion (look like little feet) are located as this is where connections
different connections to the dendrites (receptive zones) of other nearby neurons
■ Receptive Zone: Designed to receive are made
signals from other neurons ○ Usually one axon exits the cell body and can
■ Transmission Zone: Designed to pass on extend for long distances, even the entire length of
signals to other cells the spinal cord, and may branch multiple times to
carry the neuron's impulses to multiple
destinations
○ At the end of the axon, the destination of the
neuron's impulse might be another neuron, or
some other cell such as a muscle/gland capable of
receiving + responding to a nerve impulse (known
as effectors)
■ Short axons = 1-3 mm
■ Longest axons = 1 metre (extend from
base of the spine to the bottom of your
feet through the sciatic nerve)
■ Action Potential: Basic message carried
by the axon
■ Myelin Sheath: A tube of fatty tissue
that surrounds the axon, part of a glial
cell, serves to insulate the axon from
other axons + speeds up the conduction
of the action potential along the axon
, Chapter 3: Neuroscience 1
■ ‘White Matter’ of the Brain: Makes up ● Ions involved in generating resting potential:
more than half of the brain volume, is
composed mostly of a vast number of
myelinated axons
○ A- = Amino/organic ions that exist only on the
inside of the cell
○ Analogy: Salty banana— Na+ = outside, K+ =
inside
● Protein Channels: Act as passageways for ions to pass
Sequence of Activity in a Neuron: Info flows from the dendrites
through
(where info is gathered) → cell body (where info from all the multiple
● Two types of K+ channels:
dendrites is integrated) → down along the axon → other neurons
○ Leak K+ Channel: Always open, allows K+ to
(where complex calculations can occur) / effector cells (where the info
pass through the cell membrane out of the neuron,
is acted upon, ie heart beating faster)
however, much of the K+ remains inside the cell
Neuron Subtypes: Different kinds of neurons adapted to performing a
at rest, major contributor to maintaining the
different task within the nervous system
resting potential
● Sensory Neurons: Info from the environment (ie. sound,
○ Voltage-Gated K+ Channel: An important player
taste, touch) is gathered from the various receptors and sent
for driving the action potential
inwards towards the rest of the nervous system by sensory
● Ion concentrations are the result of the balance between two
neurons, sometimes specialized for gathering info directly
opposing forces:
from the environment (ie. cells responsible for sensing
○ Electrostatic Pressure: Forces of attraction +
pressure on the surface of the skin)
repulsion
● Effector Neurons: Activate the muscles of the body,
■ In areas with too many positive or
controlling movement, most common = motor neurons
negative ions, electrostatic pressure will
which have their cell bodies within the spinal cord + have
cause the ions to move from these areas
long axons that extend out to terminals attached to the
to areas with no net charge
individual muscle cells, nerve impulse/action potential
○ Diffusion: Force that moves molecules from areas
conducted from the motor neuron along its axon will cause
of high to low concentration
the associated muscle to contract
● Balance of Forces: Cell membrane acts as the barrier
● Interneurons: Vast majority of the neurons in the nervous
between the two compartments + the forces of electrostatic
system, come in a number of different varieties, each with
pressure and diffusion balance the relative concentrations of
different dendrite + axon sizes/shapes, most common =
the ions
multipolar neurons, comprised of multiple dendrites
○ The organic anions A- are trapped inside of the
extending from the cell body and only a single axon
cell, being unable to pass through the membrane
○ The bipolar neuron has only a single dendrite
○ K+ ions = higher concentration in cell
exiting one side of the cell body with a single
■ Diffusion = pushes them out
axon exiting the other (usually sensory neurons
■ Electrostatic Forces = attracts them in
whose dendrites terminate at receptor cells)
■ Therefore two forces balance and K+
○ The unipolar neuron has only a single dendrite
stays more or less where it is
leaving the cell body which eventually branches in
○ Cl- ions = higher concentration outside of cell
two directions, one towards the dendrites and the
■ Diffusion = pulls them inside
other along an axon
■ Electrostatic Forces = pushes them
Microelectrode: A small recording device inserted through the cell
outside
membrane into the intracellular fluid to study how action potentials
■ Therefore two forces balance and Cl-
work
stays more or less where it is
● Records the electrical potential/voltage across the cell
○ Na+ = higher concentration outside of cell
membrane and how this voltage changes across time as the
■ Diffusion = pulls them inside
action potential occurs
■ Electrostatic Forces = pulls them inside
Resting Potential: Even when the neuron is at rest there is a constant
■ Two forces are NOT in balance
electrical potential across the membrane (-70 mV)
○ The cell membrane is not very permeable to Na+
● The intracellular fluid of the cell is more negative than the
molecules
outside of cell (like a battery) due to an excess of positive
ions outside of the cell ■ Voltage gated sodium channels are
closed in the resting state of the neuron
● Cell membrane = selectively permeable (preferentially
and so the positively charged sodium
allows different ions to pass through it with various levels of
ions flow into the cell in only very low
ease)
concentrations, and only through other
