Brain's Building Blocks

1. Module 3Module 3
Brain’s Building BlocksBrain’s Building Blocks

2. 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

3. DEVELOPMENT OF THE BRAIN (CONT.)

4. DEVELOPMENT OF THE BRAIN (CONT.)

5. 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

6. STRUCTURE OF THE BRAIN (CONT.)

7. 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

8. 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

9. 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)

10. 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

11. PARTS OF THE NEURON

12. PARTS OF THE NEURON
• Cell Body
– large egg-shaped structure that provides fuel,
manufactures chemicals, and maintains the entire
neuron in working order

13. PARTS OF THE NEURON
• 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

14. PARTS OF THE NEURON
• Axon
– a single threadlike structure that extends from and
carries signals away from the cell body to neighboring
neurons, organs, or muscles

15. PARTS OF THE NEURON
• 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

16. PARTS OF THE NEURON
• 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)

17. PARTS OF THE NEURON
• Synapse
– infinitely small space (20-30 billionths of a meter)
– exists between and end bulb and its adjacent body
organ (e.g. heart), muscles (e.g. head), or cell body

18. 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

19. ALZHEIMER’S DISEASE AND NEURONS

20. PERIPHERAL & CENTRAL NERVOUS SYSTEM
• Peripheral Nervous System (PNS)
– made up of nerves that are located throughout the
body, except in the brain & spinal cord
• Central Nervous System (CNS)
– made up of neurons located in the brain & spinal cord

21. 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

22. 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

23. SENDING INFORMATION:
ACTION POTENTIAL SEQUENCE (CONT.)

24. 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

25. 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

26. SENDING INFORMATION:
ACTION POTENTIAL SEQUENCE (CONT.)

27. 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

28. 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

29. 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

30. 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

31. 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

32. ALCOHOL

33. 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

34. 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

35. NEW TRANSMITTERS
• Number of well-known neurotransmitters, such as
– Acetylcholine
– GABA
– Norepinephrine
– Epinephrine
– Dopamine
– Serotonin

36. 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

37. 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

38. REFLEX
• Reflex
– unlearned, involuntary reaction to some stimulus
– neural connections underlying a reflex are prewired
by genetic instructions

39. REFLEX (CONT.)
• Reflex sequence
– sensors
• sensors trigger neurons that start the withdrawal
effect
– afferent neurons
• carry information from the senses to the spinal
cord

40. 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

41. REFLEX (CONT.)

42. 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

43. 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

44. 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

45. EXPERIMENTAL TREATMENTS

46. EXPERIMENTAL TREATMENTS

47. 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

48. EXPERIMENTAL TREATMENTS