Download Module 3 - yhernandez

Module 3
Brain’s Building
Blocks
Objectives
 Students
will be able to…
– Explain the causes and effects of
Alzheimer's
– Distinguish the different parts of a
neuron and discuss their roles.
5 min quiz – Type 1
 Please
fill in the chart – DO NOT USE
NOTES – you will be graded on
participation.
Alzheimer’s disease
– 10% of cases start after age 50
– 90% of cases start after age 65

Symptoms:
– Problems with memory
– Forgetting and repeating things
– Getting lost
– Being mildly confused
Alzheimer’s disease
–
–
–
–
–
–
Period of 5 to 10 years, symptoms worsen
Result is profound memory loss
Lack of recognition of family and friends
Deterioration in personality
Emotional outbursts
Widespread damage to the brain (hippocampus,
involved in memory)
 no cure; always fatal
Alzheimer’s disease

Diagnosis and causes
– Researchers are close to identifying cause
– Genetic
– Neurological
– Possible environmental factors
– Certain chemicals (proteins and peptides) that occur
naturally in all brains seem to multiply and are believed
to cause Alzheimer’s (chemicals act like glue and destroy
brain cells)
– Film
DEVELOPMENT OF THE
BRAIN
Genes
– Chains of chemicals arranged like rungs on a
twisting ladder
– You have about 20,000 to 25,000 genes that
contain chemical instructions equaling roughly
300,000 pages of written instructions
– Genes program the development of individual
parts into a complex body and brain
DEVELOPMENT OF THE
BRAIN (CONT’D)
DEVELOPMENT OF THE
BRAIN (CONT’D)
STRUCTURE OF THE BRAIN
 Human
–
–
–
–
–
–
brain
Shaped like a small, wrinkled melon
1,350 grams (less than three pounds)
Pinkish-white color
Consistency of firm Jell-O
Fueled by sugar (glucose)
1 trillion cells divided into
 glial cells
 neurons
STRUCTURE OF THE BRAIN
(CONT’D)
 Glial
cells
– Guide the growth of developing neurons
– Wrap around neurons and form an insulation
to prevent interference from other electrical
signals
– Release chemicals that influence a neuron’s
growth and function
STRUCTURE OF THE BRAIN
(CONT’D)
STRUCTURE OF THE BRAIN
(CONT’D)
 Neuron
– Brain cell with two specialized extensions
– One extension is for receiving electrical signals
– The other extension is for transmitting electrical signals
STRUCTURE OF THE BRAIN
(CONT’D)
GROWTH OF NEW NEURONS
 Can
a brain grow new neurons?
– Canary brain
 can grow about 20,000 neurons a day during the
spring (learns new breeding song)
– Primate and human brain
 researchers conclude that adult monkey and human
brains are capable of growing relatively limited
numbers of neurons throughout adulthood
 some new neurons play important role in continuing
to learn and remember new things (hippocampus)
GROWTH OF NEW NEURONS
(CONT’D)
 Repairing
the brain
– Advances in stem research suggest the human brain
may be able to grow more neurons
– Repair damages due to
 accident
 disease
 Alzheimer’s
BRAIN VERSUS MIND
 Mind-body
question:
– How complex mental activities such as
 feeling
 thinking
 learning
– can be explained by the
 physical
 chemical
 electrical
activities
– of the brain
ALZHEIMER’S DISEASE AND
NEURONS
 Alzheimer’s
disease
– Excessive buildup of glue-like
substances
– Gradually destroy neurons
 Researchers
can study a person’s
mental activities by taking brain
scans of the neural activities going
on inside the living brain
ALZHEIMER’S DISEASE AND
NEURONS
NEURON
PARTS OF THE NEURON
 Cell
body
– Large egg-shaped structure that
provides fuel, manufactures chemicals,
and maintains the entire neuron in
working order
 Dendrite
– Branch-like extensions that arise from
the cell body
 Receive
signals from other neurons,
muscles, or sense organs
PARTS OF THE NEURON
(CONT’D)
 Axon
– A single thread-like structure that
extends/carries signals away from the
cell body to neighboring neurons,
organs, or muscles
 Myelin
sheath
– Looks like separate tube-like segments
composed of fatty material that wraps
around and insulates an axon
– Prevents interference from electrical
PARTS OF THE NEURON
(CONT’D)
 End
bulbs or terminal bulbs
– Located at extreme ends of the axon’s
branches
– Miniature container that stores
chemicals called neurotransmitters
(used to communicate with neighboring
cells)
 Synapse
– Infinitely small space (20-30 billionths
of a meter)
NERUONS VERSUS NERVES
 Reattaching
limbs
– John Thomas
 lost
arms in farming accident
 Transplanting
a face
– Isabelle
 face
severely disfigured by a dog
 received
– new nose
– lips
– chin
NERUONS VERSUS NERVES
PERIPHERAL & CENTRAL
NERVOUS SYSTEM
 Peripheral
nervous system
– Made up of nerves located throughout
the body, except in the brain and spinal
cord
 Nerves
– String-like bundles of axons and
dendrites that come from the spinal
cord and are held together by
connective tissue
– Carry information from the senses, skin,
PERIPHERAL & CENTRAL
NERVOUS SYSTEM (CONT’D)
 Central
nervous system
– Made up of neurons located in the brain
and spinal cord
 Multiple
–
sclerosis
Disease that attacks the myelin sheaths that
wrap around and insulate cells in the central
nervous system
SENDING INFORMATION:
ACTION POTENTIAL
SEQUENCE
– Stimulus (tack or nail)
– Skin has sensors that pick up
mechanical pressure and transform it
into electrical signals
– Signals are sent by the neuron’s axon to
various areas in the spinal cord and
brain
– Brain interprets electrical signals as
“pain”
 axon
membrane has chemical gates that can
open to allow electrically charged particles
to enter or can close to keep out these
particles
SENDING INFORMATION:
ACTION POTENTIAL
SEQUENCE (CONT’D)
SENDING INFORMATION:
ACTION POTENTIAL
SEQUENCE
(CONT’D)
 Resting state
– Axon has a charge
– Charge results from the axon membrane
separating positive ions on the outside
from negative ions on the inside
 Sodium
pump
– Transport process that picks up any
sodium ions that enter the axon’s
chemical gates and returns them back
outside
SENDING INFORMATION:
ACTION POTENTIAL
SEQUENCE
(CONT’D)
 Action potential
– Tiny electric current generated when
positive sodium ions rush inside the
axon
– Enormous increase of sodium ions inside
the axon causes the inside of the axon
to reverse its charge
– Inside becomes positive and outside
becomes negative
SENDING INFORMATION:
NERVE IMPULSE
SENDING INFORMATION:
NERVE IMPULSE (CONT’D)
 Nerve
impulse
– Nerve impulse is made up of six action
potentials, with the first occurring at the
beginning of the axon
 All-or-none
law
– If an action potential starts at the
beginning of the axon, the action
potential will continue at the same
speed segment to segment to the very
SENDING INFORMATION:
NERVE IMPULSE (CONT’D)
TRANSMITTERS
A
transmitter is a chemical
messenger that transmits
information between nerves and
body organs, such as muscles and
heart
 Excitatory
and inhibitory
– Excitatory transmitters
 open
chemical locks and turn on neurons
– Inhibitory transmitters
NEUROTRANSMITTERS
 Neurotransmitters
– Dozens of different chemicals made by
neurons and then used for
communication between neurons during
the performance of mental or physical
activities
NEUROTRANSMITTERS
(CONT’D)
ALCOHOL
 Alcohol
(ethyl alcohol)
– A psychoactive drug classified as a
depressant, which means that it
depresses the activity of the central
nervous system
ALCOHOL (CONT’D)
WHAT DOES ALCOHOL DO?
 Alcohol
affects the brain by imitating
a naturally occurring
neurotransmitter, GABA
 GABA neurons
– GABA neurons have chemical locks that
can be opened by chemical keys in the
form of the neurotransmitter GABA
 GABA
keys
– Alcohol molecules so closely resemble
those of the GABA neurotransmitter that
alcohol can function like GABA keys and
open GABA receptors
WHAT DOES ALCOHOL DO?
(CONT’D)
 Many
people drink alcohol to feel less
anxious and more relaxed
 Appears
to be a biological link
between alcohol and anxiety
 Deficiency
in a specific brain protein
is associated with high anxiety and
excessive alcohol use
NEW TRANSMITTERS
 Number
of well-known
neurotransmitters, such as
– Norepinephrine
– GABA
– Dopamine
– Serotonin
NEW TRANSMITTERS
(CONT’D)
– Endorphins (1970s)
 painkiller
similar to morphine
 decreases effects of pain during great bodily
stress
– Anandamide (1990s)
 similar
to THC (active ingredient in
marijuana)
– involved with
 memory
 motor coordination
 emotions
NEW TRANSMITTERS
(CONT’D)
 Anandamide
may help people
regulate emotions, which would help
them to better deal with anxiety and
stress
– Nitric oxide (mid-1990s)
 may
be involved in regulating aggressive
and impulsive behaviors
NEW TRANSMITTERS
(CONT’D)
– Orexin (hypocretin)
 late
1990s
 involved in the brain’s pleasure and reward
system
 high levels: cravings for food or drugs
 low levels: reduce cravings
 involved in sleep and wakefulness
– low levels have been linked to narcolepsy
REFLEX
 Reflex
– Unlearned, involuntary reaction to some
stimulus
– Neural connections underlying a reflex
are prewired by genetic instructions
REFLEX (CONT’D)
 Reflex
sequence
– Sensors
 sensors
trigger neurons that start the
withdrawal effect
– Afferent neurons (sensory neurons)
 carry
information from the senses to the
spinal cord
REFLEX (CONT’D)
– Interneuron
 relatively
short neuron whose primary task
is making connections between other
neurons
– Efferent neuron
 carries
information away from the spinal
cord to produce responses in various
muscles and organs throughout the body
REFLEX (CONT’D)
PARKINSON’S DISEASE
 Parkinson’s
disease
– Includes symptoms of tremors and
shakes in the limbs, a slowing of
voluntary movements, muscle stiffness,
problems with balance and coordination,
and feelings of depression
– As the disease progresses, patients
develop a shuffling walk and may
suddenly freeze in space for minutes or
hours at a time
PARKINSON’S DISEASE
(CONT’D)
 Parkinson’s
disease
– Caused by destruction of neurons that
produce dopamine
– L-dopa is a medication that boosts the
levels of dopamine in the brain
– Eventually, the drug causes involuntary
jerky movements
– After prolonged use, L-dopa’s beneficial
effect may be replaced by unwanted
jerky movements
EXPERIMENTAL
TREATMENTS
 Sterotaxic
procedure
– Fixing a patient’s head in a holder and
drilling a small hole through the skull
– The holder has a syringe that can be
precisely guided into a predetermined
location in the brain
EXPERIMENTAL
TREATMENTS (CONT’D)
EXPERIMENTAL
TREATMENTS (CONT’D)
EXPERIMENTAL
TREATMENTS (CONT’D)
 Removing
part of the brain
– Thalamotomy (Michael J. Fox)
 Brain
stimulation
– Electrodes placed into thalamus
– Patient controls amount of stimulus
– Helps reduce tremors
EXPERIMENTAL
TREATMENTS (CONT’D)