The Brain

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The Brain

• Understanding The Amazing Brain

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(No Transcript)
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What is the Brain

• The brain is incredibly complex.
• It makes us human.
• It gives people the capacity for art, language,
  moral judgments, and rational thought.
• It's also responsible for each individual's
  personality, memories, movements, and how we
  sense the world.

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What is the Brain

• Physically, the brain looks very simple.
• It is a jellylike mass of fat and protein
  weighing about 3 pounds (1.4 kilograms).
• It is one of the body's biggest organs,
  consisting of some 100 billion nerve cells.
• Our brains allow us to put together thoughts and
  highly coordinated physical actions.
• They also regulate our unconscious body
  processes, such as digestion and breathing.

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Neurons

• The brain's nerve cells are known as neurons,
  which make up the organ's so-called "gray
  matter."
• The neurons transmit and gather electrochemical
  signals that are communicated via a network of
  millions of nerve fibers called dendrites and
  axons.
• These are the brain's "white matter."

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Cerebrum

• The cerebrum is the largest part of the brain,
  accounting for 85 percent of its weight.
• The distinctive, deeply wrinkled outer surface is
  the cerebral cortex, which consists of gray
  matter.
• Beneath this lies the white matter.
• It's the cerebrum that makes the human brainand
  therefore humansso formidable.
• Whereas animals such as elephants, dolphins, and
  whales have larger brains, humans have the most
  developed cerebrum.

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Lobes of the Cerebrum

• The cerebrum has two halves, or hemispheres.
• Each hemisphere is divided into four regions
  called lobes.
• Each lobe seen here is mirrored in the other
  hemisphere.

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The Functions of the Lobes

• The frontal lobes, located behind the forehead,
  are involved with speech, thought, learning,
  emotion, and movement.
• Behind them are the parietal lobes, which process
  sensory information such as touch, temperature,
  and pain.
• At the rear of the brain are the occipital lobes,
  dealing with vision.
• Lastly, there are the temporal lobes, near the
  temples, which are involved with hearing and
  memory.

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The Cerebellum

• The Cerebellum controls movement and balance.
• It is the second largest part of the brain.
• The cerebellum sits beneath the back of the
  cerebrum.
• It is responsible for coordinating muscle
  movement and controlling our balance.
• The cerebellum transmits information to the
  spinal cord and other parts of the brain.

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Diencephalon

• The diencephalon is located in the core of the
  brain.
• It consists of two major sections the thalamus
  and hypothalamus.

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Thalamus

• The thalamus acts as a relay station for incoming
  nerve impulses from around the body.

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Hypothalamus

• The hypothalamus controls hormone secretions from
  the pituitary gland.
• These hormones govern growth and instinctual
  behavior such as eating, drinking, sex, anger,
  and reproduction.
• The hypothalamus, for instance, controls when a
  new mother starts to lactate.

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The Brain Stem

• The brain stem, located at the base of the brain,
  controls reflexes and crucial, basic life
  functions.
• This includes heart rate, breathing, and blood
  pressure.
• It also regulates when you feel sleepy or awake.

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Protecting the Brain

• The brain is extremely sensitive and delicate,
  and so requires maximum protection.
• This is provided by the surrounding skull and
  three tough membranes called meninges.
• The spaces between these membranes are filled
  with fluid that cushions the brain and keeps it
  from being damaged by contact with the inside of
  the skull.

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Brain Communication

• The brain communicates through neurons.
• A neuron is a nerve cell that sends and receives
  electrical signals within the body and
  communicates these signals to the brain.
• The human brain has approximately 100 billion
  neurons.

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Axons and Dendrites

• Neurons have specialized extensions called axons
  and dendrites.
• Axons carry information away from the cell to the
  brain.
• Dendrites bring information to the cell from the
  brain.

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Neurotransmitters

• Communication of information between neurons is
  accomplished by the movement of chemicals across
  a small gap called the synapse.
• Chemicals called neurotransmitters are released
  from one neuron at the presynaptic nerve
  terminal.
• Neurotransmitters then cross the synapse where
  they may be accepted by the next neuron at a
  specialized site called a receptor.

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How a Nerve Works

• Once a receptor site is activated it is either
  depolarized or hyperpolarized.
• Depolarization excites the nerve so the nerve
  will fire.
• Hyperpolarization inhibits the nerve so the nerve
  wont fire.

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Neurotransmitters

• Some of the best known neurotransmitters include
• Acetylcholine
• Dopamine
• Epinephrine and Norepinephrine
• Serotonin
• Histamine

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Acetylcholine

• Acetylcholine is important in the stimulation of
  muscle tissue.
• Since the heart is a muscle, acetylcholine
  breakdown to cause the heart to stop functioning.

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Dopamine

• Dopamine affects brain processes that control
  movement, emotional response, and ability to
  experience pleasure and pain.
• Because of this, it is one of the
  neurotransmitters that plays a major role in
  addiction.
• As a chemical messenger, dopamine is similar to
  the hormone adrenaline.
• The brains of people who have Parkinson's disease
  contain almost no dopamine.
• Cocaine and other drugs of abuse can alter
  dopamine function.

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Epineprine and Norepinephrine

• Norepinephrine is a neurotransmitter that acts
  with the hormone epinephrine to react to stress.
• This is also called the fight or flight response.

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Serotonin

• The functions of serotonin are numerous and
  appear to involve control of appetite, sleep,
  memory and learning, temperature regulation,
  mood, behavior (including sexual and
  hallucinogenic behavior), cardiovascular
  function, muscle contraction, endocrine
  regulation, and depression.

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Histamines and Allergies

• Histamines are the neurotransmitters that cause
  the reactions of people who have allergies.
• People who have allergies exhibit certain common
  symptoms like sneezing, itchy and watery eyes, an
  itchy throat, a runny nose, and itchy rashes are
  all possible symptoms of an allergy.

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Allergens

• This is an overreaction by the body's immune
  system to a substance that would not normally
  provoke such a response in other people.
• Common substances such as pollen, dust particles,
  animal dander (pieces of dry skin, hair and fur),
  and mould spores can prompt a severe reaction in
  people who are allergic to them.
• These substances are collectively referred to as
  "allergens".

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Drugs and the Brain

• How drugs affect the brain depends on several
  factors including
• The dose taken
• How the drug was taken pill, injection, smoked
  etc.
• The rate of absorption into the blood stream.
• The rate at which the body can eliminate it.
• http//www.pbs.org/wnet/closetohome/science/html/s
  imilar.html

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Effects of Drugs on the Brain

• A drug might cause a physiological or a
  behavioral effect.
• It might cause a decrease in heart rate or an
  increase in sexual arousal level.
• Most importantly, the presence of the drug may
  trigger responses that change the reaction to
  future encounters with the drug.
• Drugs may cause an increase or decrease in
  tolerance and ultimately lead to dependency in
  order to feel effects that your body should
  naturally feel.

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• Your body may react to a drug by either
• Trying to stop the drug from reaching the
  receptors
• Or
• By attacking the drug using the bodies immune
  responses.

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Citation

• The next group of slides are taken directly from
  http//www.brainsource.com/brain_on_drugs.htm

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Heroin

• Heroin is a highly addictive opiate (like
  morphine). Brain cells can become dependent
  (highly addictive) on this drug to the extent
  that users need it in order to function in their
  daily routine.
• While heroin use starts out with a rush of
  pleasure, it leaves the use in a fog for many
  hours afterwards.
• Users soon find that their sole purpose in life
  is to have more of the drug that their body has
  become dependant on.

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Marijuana

• The parts of the brain that control emotions,
  memory, and judgment are affected by marijuana. 
• Smoking it can not only weaken short-term memory,
  but can block information from making it into
  long term memory.
• It has also been shown to weaken problem solving
  ability.

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Alcohol

• Alcohol is no safer than drugs. Alcohol impairs
  judgment and leads to memory lapses.
• It can lead to blackouts.
• It distorts vision, shortens coordination, and in
  addition to the brain can damage every other
  organ in the body.

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Cocaine

• Cocaine, both in powder form and as crack, is an
  extremely addictive stimulant.
• An addict usually loses interest in many areas of
  life, including school, sports, family, and
  friends. Use of cocaine can lead to feelings of
  paranoia and anxiety.
• Although often used to enhance sex drive,
  physical effect of cocaine on the receptors in
  the brain reduce the ability to feel pleasure
  (which in turn causes the dependency on the drug).

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Inhalants

• Inhalants, such as glue, gasoline, hair spray,
  and paint thinner, are sniffed.
• The effect on the brain is almost immediate. And
  while some vapors leave the body quickly, others
  will remain for a long time.
• The fatty tissues protecting the nerve cells in
  the brain are destroyed by inhalant vapors.
• This slows down or even stops neural
  transmissions.
• Effects of inhalants include diminished ability
  to learn, remember, and solve problems. 

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Ecstasy

• Extended use of this amphetamine causes
  difficulty differentiating reality and fantasy,
  and causes problems concentrating.
• Studies have found that ecstasy destroys certain
  cells in the brain. 
• While the cells may re-connect after discontinued
  use of the drug, they don't re-connect normally.
• Like most drugs, this one impairs memory and can
  cause paranoia, anxiety, and confusion.

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LSD

• While some people use LSD for the sense of
  enhanced and vivid sensory experience, it can
  cause paranoia, confusion, anxiety, and panic
  attacks.
• Like Ecstasy, the user often blurs reality and
  fantasy, and has a distorted view of time and
  distance.

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Steroids

• Anabolic steroids are used to improve athletic
  performance and gain muscle bulk.
• Unfortunately, steroids cause moodiness and can
  permanently impair learning and memory abilities.

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Tobacco

• Tobacco is a dangerous drug, putting nicotine
  into your body.
• Nicotine affects the brain quickly, like other
  inhalants, producing feelings of pleasure, like
  cocaine, and is highly addictive, like heroin.

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Methamphetamine

• Known on the street as meth, speed, chalk, ice,
  crystal, and glass.
• MRI scans of addicts show evidence of
  considerable brain inflammation and functions
  similar to people with dementia.
• Meth particularly affects two key brain areas
  associated with memorythe same ones damaged in
  early Alzheimer's.
• Brain scans of meth addicts showed these had
  shrunk 10.
• http//www.sciencentral.com/articles/view.php3?typ
  earticlearticle_id218392428

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Ritalin

• This drug is often prescribed to treat attention
  deficit disorder. It is becoming an illicit
  street drug as well.
• Drug users looking for a high will crush Ritalin
  into a powder and snort it like cocaine, or
  inject it like heroin. It then has a much more
  powerful effect on the body.
• It causes severe headaches, anxiety, paranoia,
  and delusions. 

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Citations

• http//science.nationalgeographic.com/science/heal
  th-and-human-body/human-body/brain-article.html
• http//faculty.washington.edu/chudler/chnt1.html
• http//www.encyclopedia.com/doc/1E1-acetylch.html
• http//thebrain.mcgill.ca/flash/d/d_06/d_06_m/d_06
  _m_mou/d_06_m_mou_2a.jpg
• http//www.utexas.edu/research/asrec/dopamine.html
  
• http//www.encyclopedia.com/doc/1E1-norepine.html
• http//serendip.brynmawr.edu/bb/neuro/neuro99/web1
  /Byrd.html
• http//www.treatallergies.com/faq/antihistamines/
• http//www.rci.rutgers.edu/lwh/drugs/chap09.htm