Brain’s Building Blocks

 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

Six week old 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

 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

 Neuron ◦ a brain cell with 2 specialized extensions ◦ one extension is for receiving electrical signals ◦ the other extension is for transmitting electrical signals

 ns-and-Neuro-transmitters ns-and-Neuro-transmitters

 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) 

 Repairing the Brain ◦ advances in stem research suggest the human brain may be able to grow more neurons ◦ repair damages:  accident  disease  Alzheimer’s

 Mind-body Question ◦ how complex mental activities such as  feeling  thinking  learning ◦ can be explained by the  physical  chemical  electrical activities ◦ of the brain

 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

 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

 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 ◦ 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

 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 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

 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

◦ 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

 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

 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

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 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

 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

 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

 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 (ethyl alcohol) ◦ A psychoactive drug that is classified as a depressant, which means that it depresses the activity of the central nervous system

 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

 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

 Number of well-known neurotransmitters, such as ◦ Acetylcholine ◦ GABA ◦ Norepinephrine ◦ Epinephrine ◦ Dopamine ◦ Serotonin

 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

 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 ◦ unlearned, involuntary reaction to some stimulus ◦ neural connections underlying a reflex are prewired by genetic instructions

 Reflex sequence ◦ sensors  sensors trigger neurons that start the withdrawal effect ◦ afferent neurons  carry information from the senses to the spinal cord

◦ 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

 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 ◦ 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

 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

 Removing part of the brain ◦ Thalamotomy (Michael J. Fox)  Brain Stimulation ◦ electrodes placed into thalamus ◦ patient controls amount of stimulus ◦ helps reduce tremors