Bio Psychology – Chapter 2 “Neurons and Action Potential”
Anatomy of neurons and glia
o The human nervous system is comprised of two kinds of cells:
Neurons: receive and transmit information
Glia
o The human brain contains approximately 100 billion individual
neurons
o In the late 1800s, the Spaniard Santiago Ramon y Cajal (1852-1934)
was the first to demonstrate that the individual cells comprising the
nervous system remained separate
He showed that they did not grow into each other as
previously believed
o The membrane: a structure that separates the inside of the cell
from the outside environment
o The nucleus: a structure that contains the chromosomes
o The mitochondrion: structure that performs metabolic activities and
provides energy that the cells requires
o Ribosomes: sites at which the cell synthesizes new protein
molecules
o Endoplasmic reticulum: network of thin tubes that transport
newly synthesized proteins to their location
o Neuron cells are similar to other cells of the body but have a
distinctive shape
o A motor neuron has its soma in the spinal cord and receives
excitation from other neurons and conducts impulses along its axon
to a muscle
o A sensory neuron is specialized at one end to be highly sensitive to
a particular type of stimulation (touch, light, sound, etc.)
o
o All neurons have the following major components:
Dendrites
Soma/cell body
Axon
Presynaptic terminals
o Dendrites are branching fibers with a surface lined with synaptic
receptors responsible for bringing information into the neuron
o Some dendrites also contain dendritic spines that further branch
out and increase the surface area of the dendrite
, o The greater the surface area of the dendrite, the more information it
can receive
o Cell body/soma: contains the nucleus, mitochondria, ribosomes,
and other structures found in other cells
Also responsible for the metabolic work of the neuron
o Axon: thin fiber of a neuron responsible for transmitting nerve
impulses toward other neurons, organs, or muscles
o Some neurons are covered with an insulating material called the
myelin sheath with interruptions in the sheath known as nodes of
Ranvier
o Presynaptic terminals refer to the end points of an axon where
the release of chemicals to communicate with other neurons occurs
o Terms used to describe the neuron include the following:
Afferent axon: refers to bringing information into a structure
Efferent axon: refers to carrying information away from a
structure
Interneurons or intrinsic neurons are those whose dendrites
and axons are completely contained within a single structure
o Neurons vary in size, shape, and function
o The shape of a neuron determines it connection with other neurons
and contribution to the nervous system
o The function is closely related to the shape of a neuron
Example: Pukinje cells of the cerebellum branch extremely
widely within a single plane
o Glia (or neuroglia) are the other major components of the nervous
system
o Types of glia in the brain:
Astrocytes help synchronize the activity of the axon by
wrapping around the presynaptic terminal and taking up
chemicals released by the axon allowing them to send
messages in waves, remove waist material and regulate blood
flow
Microglia remove waste material and other microorganisms
that could prove harmful to the neuron
Oligodendrocytes (in the brain and spinal cord) and
Schwann cells (in the periphery of the body) build the
myelin sheath that surrounds and insulates certain vertebrate
axons
Radial glia guide the migration of neurons and the growth of
their axons and dendrites during embryonic development
o When embryonic development finishes, most radial glia differentiate
into neurons and a smaller number differentiate into astrocytes and
oligodendrocytes
The blood-brain barrier
o The blood-brain barrier is a mechanism that surrounds the brain and
blocks most chemicals from entering
o The immune system destroys damaged or infected cells throughout
the body
Anatomy of neurons and glia
o The human nervous system is comprised of two kinds of cells:
Neurons: receive and transmit information
Glia
o The human brain contains approximately 100 billion individual
neurons
o In the late 1800s, the Spaniard Santiago Ramon y Cajal (1852-1934)
was the first to demonstrate that the individual cells comprising the
nervous system remained separate
He showed that they did not grow into each other as
previously believed
o The membrane: a structure that separates the inside of the cell
from the outside environment
o The nucleus: a structure that contains the chromosomes
o The mitochondrion: structure that performs metabolic activities and
provides energy that the cells requires
o Ribosomes: sites at which the cell synthesizes new protein
molecules
o Endoplasmic reticulum: network of thin tubes that transport
newly synthesized proteins to their location
o Neuron cells are similar to other cells of the body but have a
distinctive shape
o A motor neuron has its soma in the spinal cord and receives
excitation from other neurons and conducts impulses along its axon
to a muscle
o A sensory neuron is specialized at one end to be highly sensitive to
a particular type of stimulation (touch, light, sound, etc.)
o
o All neurons have the following major components:
Dendrites
Soma/cell body
Axon
Presynaptic terminals
o Dendrites are branching fibers with a surface lined with synaptic
receptors responsible for bringing information into the neuron
o Some dendrites also contain dendritic spines that further branch
out and increase the surface area of the dendrite
, o The greater the surface area of the dendrite, the more information it
can receive
o Cell body/soma: contains the nucleus, mitochondria, ribosomes,
and other structures found in other cells
Also responsible for the metabolic work of the neuron
o Axon: thin fiber of a neuron responsible for transmitting nerve
impulses toward other neurons, organs, or muscles
o Some neurons are covered with an insulating material called the
myelin sheath with interruptions in the sheath known as nodes of
Ranvier
o Presynaptic terminals refer to the end points of an axon where
the release of chemicals to communicate with other neurons occurs
o Terms used to describe the neuron include the following:
Afferent axon: refers to bringing information into a structure
Efferent axon: refers to carrying information away from a
structure
Interneurons or intrinsic neurons are those whose dendrites
and axons are completely contained within a single structure
o Neurons vary in size, shape, and function
o The shape of a neuron determines it connection with other neurons
and contribution to the nervous system
o The function is closely related to the shape of a neuron
Example: Pukinje cells of the cerebellum branch extremely
widely within a single plane
o Glia (or neuroglia) are the other major components of the nervous
system
o Types of glia in the brain:
Astrocytes help synchronize the activity of the axon by
wrapping around the presynaptic terminal and taking up
chemicals released by the axon allowing them to send
messages in waves, remove waist material and regulate blood
flow
Microglia remove waste material and other microorganisms
that could prove harmful to the neuron
Oligodendrocytes (in the brain and spinal cord) and
Schwann cells (in the periphery of the body) build the
myelin sheath that surrounds and insulates certain vertebrate
axons
Radial glia guide the migration of neurons and the growth of
their axons and dendrites during embryonic development
o When embryonic development finishes, most radial glia differentiate
into neurons and a smaller number differentiate into astrocytes and
oligodendrocytes
The blood-brain barrier
o The blood-brain barrier is a mechanism that surrounds the brain and
blocks most chemicals from entering
o The immune system destroys damaged or infected cells throughout
the body
