Transcript structure of the brain (cont.)

Module 3
Brain’s Building Blocks
DEVELOPMENT OF THE BRAIN
• fact that your brain does not develop into a nose is
because of instructions contained in your genes
• Genes
– chains of chemicals that are arranged like rungs on a
twisting ladder
– there are about 20,000-25,000 genes that contain
chemical instructions that equal about 300,000 pages
of written instructions
– genes program the development of individual parts
into a complex body & brain
DEVELOPMENT OF THE BRAIN (CONT.)
DEVELOPMENT OF THE BRAIN (CONT.)
• Insert pictures of
– Six week old brain
– Mature brain
STRUCTURE OF THE BRAIN
• Human brain:
– is shaped like a small wrinkled melon
– 1,350 grams (less than 3 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.)
• Glial cells
• 3 Functions:
– 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.)
STRUCTURE OF THE BRAIN (CONT.)
• Neuron
– a brain cell with 2 specialized extensions
– one extension is for receiving electrical signals
– the other extension is for transmitting electrical
signals
STRUCTURE OF THE BRAIN (CONT.)
STRUCTURE OF THE BRAIN (CONT.)
• Insert: video Main Parts of the Neuron, Psychology
Digital Video Library 3.0. Debra Schwiesow, page 17
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.)
• Repairing the Brain
– advances in stem research suggest the human brain
may be able to grow more neurons
– repair damages:
• 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
PARTS OF THE NEURON
• Cell Body
– large egg-shaped structure that provides fuel,
manufactures chemicals, and maintains the entire
neuron in working order
• Dendrite
– branchlike extensions that arise from the cell body
– receive signals from other neurons, muscles, or
sense organs
– pass these signals onto the cell body
PARTS OF THE NEURON (CONT.)
• Axon
– a single threadlike structure that extends from and
carries signals away from the cell body to neighboring
neurons, organs, or muscles
• Myelin Sheath
– looks like separate tubelike segments composed of
fatty material that wraps around and insulates an
axon
– prevents interference from electrical signals
generated in adjacent axons
PARTS OF THE NEURON (CONT.)
• 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)
– exists between and end bulb and its adjacent body
organ, heart, muscles, or cell body
ALZHEIMER’S DISEASE AND NEURONS
• Alzheimer’s disease
– excessive buildup of gluelike substances
– gradually destroy neurons
• Researchers recently discovered an experimental
vaccine that may help stop the buildup of these gluelike,
killer substances and they continue to search for other
interventions
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
PERIPHERAL & CENTRAL NERVOUS SYSTEM
• Peripheral Nervous System
– made up of nerves that are located throughout the
body, except in the brain & spinal cord
• Central Nervous System
– made up of neurons located in the brain & spinal cord
PERIPHERAL & CENTRAL NERVOUS SYSTEM
(CONT.)
• Nerves
– stringlike bundles of axons and dendrites that come
from the spinal cord and are held together by
connective tissue
– carry information from the senses, skin, muscles, and
the body’s organs to and from the spinal cord
– nerves in the peripheral nervous system have the
ability to grow or reattach if severed or damaged
SENDING INFORMATION: ACTION POTENTIAL
SEQUENCE
– axon membrane has chemical gates that can open to
allow electrically charged particles to enter or can
close to keep out these particles
– ions are chemical particles that have electrical
charges
– opposite charges attract and like charges repel
SENDING INFORMATION: ACTION POTENTIAL
SEQUENCE (CONT.)
SENDING INFORMATION: ACTION POTENTIAL
SEQUENCE (CONT.)
• Resting state
– the axon has a charge
– the charge results from the axon membrane
separating positive ions on the outside from negative
ions on the inside
SENDING INFORMATION: ACTION POTENTIAL
SEQUENCE (CONT.)
• Action potential
– tiny electric current that is generated when the
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: ACTION POTENTIAL
SEQUENCE (CONT.)
The Action Potential
PLAY
VIDEO
SENDING INFORMATION: NERVE IMPULSE
• Sending information
– action potential is a tiny electrical current that is
generated when the positive sodium ions rush inside
the axon
– the enormous increase of Na ions inside the axon
causes the inside to reverse its charge
– the inside becomes positive & the outside becomes
negative
SENDING INFORMATION: NERVE IMPULSE
(CONT.)
• 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 end of the
axon
• Nerve impulse
– nerve impulse is made up of 6 action potentials, with
the first occurring at the beginning of the axon
SENDING INFORMATION: NERVE IMPULSE
(CONT.)
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
• block chemical locks and turn off neurons
NEUROTRANSMITTER
• Neurotransmitters
– dozens of different chemicals that are made by
neurons and then used for communication between
neurons during the performance of mental or physical
activities
ALCOHOL
• Alcohol (ethyl alcohol)
– A psychoactive drug that is classified as a
depressant, which means that it depresses the
activity of the central nervous system
ALCOHOL
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
– when GABA neurons are excited, they decrease
neural activity
WHAT DOES ALCOHOL DO? (CONT.)
• 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
– Acetylcholine
– GABA
– Norepinephrine
– Epinephrine
– Dopamine
– Serotonin
NEW TRANSMITTERS (CONT.)
• New
– Endorphins (1970’s)
• painkiller similar to morphine
• decreases effects of pain during great bodily stress
– Anandamide (1990’s)
• similar to THC (active ingredient in marijuana)
– involved with
» memory
» motorcoordination
» emotions
NEW TRANSMITTERS (CONT.)
• Anandamide may help people regulate emotions, which
would help them to better deal with anxiety and stress
– Nitric oxide (mid-1990’s)
• may be involved in regulating aggressive and
impulsive behaviors
REFLEX
• Reflex
– unlearned, involuntary reaction to some stimulus
– neural connections underlying a reflex are prewired
by genetic instructions
REFLEX (CONT.)
• Reflex sequence
– sensors
• sensors trigger neurons that start the withdrawal
effect
– afferent neurons
• carry information from the senses to the spinal
cord
REFLEX (CONT.)
– Interneuron
• relatively short neuron whose primary task
is making connections between other
neurons
– Efferent neuron
• carry information away from the spinal cord
to produce responses in various muscles
and organs throughout the body
REFLEX (CONT.)
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
– Michael J. Fox
PARKINSON’S DISEASE (CONT.)
• Parkinson’s Disease
– it is 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
EXPERIMENTAL TREATMENTS
EXPERIMENTAL TREATMENTS
• 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