Pathways to the Nervous System
The Neuron
The Neuron
•
• Approximately
before birth
upon birth
• 90% of your cells are glia cells (in CNS) and
Schwann cells (in PNS)
• (fun fact: prenatal neurons develop at the rate of
250,000/minute!!)
Nerve fibers are long dendrites and axons
bundled together. They are called nerves in
the PNS and tracts in the CNS
Nerves that lead to the brain are also known as:
Nerves going from the brain are:
Neuron
Parts:
dendrites
soma
nucleus,
nissl substance
axon
myelin sheath
nodes of Ranvier
terminal feet
terminal buttons
Chemicals contained in
the terminal buttons
are called
neurotransmitters,
which will leave:
The area between
neurons is known as:
All-or-none law
• The all-or-none law
states that when a
neuron is stimulated,
it must stimulated to:
Ways of Measuring the Brain
Electroencephalograph
-EEGMeasures:
Used in sleep
research, detects
dreams and sleep
disorders
Ways of Measuring the Brain
Lesioning
Intentional damage to brain cells:
Lesioning has taught us a lot about the
functions of the brain
Ways to Measure the Brain
CT-Computerized
Tomography
Horizontal slices:
Least expensive –
widely used
Ways to Measure the Brain
Positron Emission
Tomography (PET)
Radioactive tracer
Color coded map
Ways to Measure the Brain
Magnetic Resonance
Imaging (MRI)
What it is:
Very expensive
Ways of Measuring the Brain
Electrical Stimulation of the Brain (ESB)
Sends a weak:
Stimulates areas of the brain to determine what
effect the stimulation has
Discovered by Penfield, done:
Neurotransmitters
Acetylcholine-Ach
Involved in voluntary movements
Contributes to:
Lack of Ach –
Low levels of Ach – cells die
Acetylcholine
Hippocampus of the brain
Overabundance of Ach-
Curare-a poison that blocks the transmission
of Ach, which will lead to intense spasms
of the muscles, including heart –
Dopamine-DA
Controls voluntary muscles
A monoamine
Lack of –
Too much –
Dopamine
Tardive Dyskenesia-a disease which can
cause Parkinson’s-like tremors. This
occurs when a person takes meds for:
Plays a major role in addiction as it is similar
to adrenaline and controls:
Serotonin-SE
Highly implicated in
, hence your SSRI’s
(antidepressants)
Low levels of SE seemed to
be linked to:
Involved in wakefulness
and:
A Monoamine
Norepinephrine-NE
Low levels of NE have been associated with:
Cocaine and amphetamines may stimulate
the activity of this neurotransmitter (may
cause hallucinations)
A monoamine
Epinephrine
• Synthesized by the:
• Activates the
sympathetic nervous
system and puts the
body:
Endorphins
Resemble opiates
Pain blockers
Gate control theory:
GABA
Low levels:
Antianxiety drugs:
Central and Peripheral Nervous
Systems
• Central Nervous
System –
– Consists of the:
Peripheral Nervous
System
• Contains:
– Somatic Nervous
System:
– Autonomic Nervous
System:
• Sympathetic NS
Peripheral Nervous System
• Parasympathetic
– Rest and digest
response
– Brings the system
back to:
The Brain
• Did you know that the
brain weighs only
about 1 pound at
birth?
• By one year of age,
the brain will double
in size and be almost
90% of its adult size
Lobes of the Brain
• FRONTAL LOBE
• Located in front of
the central sulcus.
• Concerned with:
•
Lobes of the Brain
• Frontal Lobe• On the left side is
Broca’s area –
Motor Strip
Phineas Gage
• After Gage had an
accident in which a
metal pipe went
through his brain, it
was thought that he
would not survive.
• However, he did –
with interesting
consequences
•
Lobes of the brain
• PARIETAL LOBE
• Located behind the
central sulcus.
• Concerned with:
The Primary Somatosensory Cortex
Neurons in the primary somatosensory are activated when the skin
is touched. However, the body is NOT represented in the cortex in
proportion to the amount of skin.
• A map of the human
somatosensory cortex
was drawn by Dr. Wilder
Penfield in the 1950's.
• By observing the
location on the brain that
caused patients to feel
sensations on different
parts of their bodies, Dr.
Penfield was able to
draw a map of the brain
Lobes of the Brain
• TEMPORAL LOBE
• Located below the
lateral fissure.
• Concerned with:
Lobes of the Brain
• Temporal Lobe –
• Behind the temporal lobe
is the uncus –
• Left side of temporal lobe
is Wernicke’s area -
Lobes of the Brain
• OCCIPITAL LOBE
• Located at the back
of the brain, behind
the parietal lobe and
temporal lobe.
• Concerned with:
The Lobes of the Brain
.
Medial View
Sensory & Motor
Areas
The
Brain
Brain
Weight(gm)
6,000
1,3001,400
97
72
Species
Elephant
Adult Human
Rhesus
Monkey
Dog
30
Cat
10
Rabbit
2.2
Owl
How does the human brain compare?
Parts of the Brain
• Cerebral cortex
functions:
•
•
•
•
•
Thought
Voluntary movement
Language
Reasoning
Perception
•
The
Hindbrain
• Cerebellum
• Functions:
• Looks like a mini-brain
•
Cerebellum
• Two peach-size mounds
of folded tissue at the
base of the brain form
the cerebellum.
• Damage to this area
leads to:
• Some scientists have
discovered:
The Hindbrain
• Medulla
• Control of:
– a.k.a. the medulla
oblongata
The Hindbrain
• Pons
– Located above the medulla
– Connects midbrain with the:
– Controls:
– Contains sensory and motor
tracts between the cortex and
the medulla
– Involved in:
The Midbrain
• The midbrain is
very small in
humans
• Coordinates
simple
movements with
sensory
information
The Midbrain
• Reticular formation (a.k.a.
Reticular activating system)
• Attention and arousal-
• If damaged, the person may:
• Involved in pain perception
The Forebrain
• Thalamus
– Functions as a relay
station – sends
sensory information to:
– The only sensory
information that does
not travel through the
thalamus is:
The Forebrain
• Hypothalamus
Known for four F’s-
Although the pituitary
gland is given credit for
regulating the endocrine
system, it is the
hypothalamus that sends
the message to:
The Forebrain
• Hypothalamus
– Regulates:
– Controls your
biological rhythms, so
it is also involved with
whether you are a
morning person or an
afternoon person
The Forebrain
• Limbic system:
– Regulation of
emotions-
– Also known for being
involved with:
– Hippocampus,
amygdala, septum, part
of the thalamus and
hypothalamus
The Forebrain
• Involved
Hippocampus
in memory
and how we:
Removal of
temporal lobe can
result in:
The Forebrain
• Hippocampus• Many memories are
not stored there,
however, the
hippocampus sends
information to
different areas of the
cerebral cortex for
processing
The Forebrain
Amygdala
• Plays a role in aggression
and defensiveness
• When damaged:
• When stimulated:
The Forebrain
• Septum
• Important pleasure center
of the brain – mild
stimulation of this area
may result in intense
pleasurable feelings,
including intense sexual
arousal
• Lesions to the septal area
may result in:
•
Stimulation results in:
Corpus Callosum
• The brain has
identical parts in each
hemisphere
• The corpus callosum
connects:
• Often cut in patients
with:
Cerebrum
• Largest part of the
brain
– Divided into two
hemispheres – each
hemisphere has
identical parts:
– Separate by the-
– Divided into four lobes
Hemispheres of the Brain
• Are you right-handed or left-handed?
• About 90% of the population are right-handed they prefer to use their right hand to write, eat
and throw a ball ("right hand dominant.“)
• Most of the other 10% of the population is lefthanded or "left hand dominant."
• There are few people who use each hand
equally; they are "ambidextrous.”
Brain
Hemispheres
Marion Diamond
• Demonstrated that an
enriched environment will
increase cell weight and
add to the number of
dendrites on the neuron
• An impoverished
environment decreases
cell weight:
Environmental impact on the
brain..
• From the time a baby is
born (and possibly
before) they are
beginning the formation
of trillions of neuronal
connections via the
environment
• Neurons will constantly
grow, die, become
stronger or weaker
depending on the
environment
Emotions and learning
• Positive emotions,
however, can
enhance learning
• When students laugh
or have positive
feelings towards
learning they are
more likely to learn
The Adolescent
Brain
• “What were you
thinking?”
• “Don’t you ever think
before you act?”
• “When are you going to
make better decisions?”
• “How many times do I
have to say the same
thing over and over
again?”
• Any of this sound
familiar?
The Adolescent Brain
• The prefrontal cortex
has not fully
developed and the
thinking, judging,
planning portion of
their brain is not
functioning to its
fullest capacity
The Adolescent Brain
• New research indicates
that the adolescent brain
has new cell growth and
new neural connections
• This new growth and the
pruning of neurons not in
use help the brain
develop emotional
maturity
Diseases of the brain
• Alzheimer’s Disease
– have gradual memory
loss and difficulty with
language and emotion
– while the disease
starts out slowly, it
progresses to the point
that the person needs
help eating, bathing
and using the
bathroom
Diseases of the brain
• Scans may help in the
diagnosis
– CAT scans tend to
help visualize brain
shrinkage and
enlarged ventricles
Diseases of the brain
• Research has demonstrated that the more
neuronal connections one has, the more likely
they are to lessen the effects of AD
• Therefore, one should keep active physically
and mentally