Neurons and the Brain

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Neurons and the Brain

• 3/21-23/05

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Next TestNeurons, Emotions and Beyond

• Jansens lecture notes
• Bedells notes and handout
• Jacobsons lecture notes
• Reading on emotions
• Clark Reading
• TEST 4/12
• Presentations 4/14 4/19 4/21 4/26

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Individualism

• And its consequences
• Discussion Why isnt a memory just in your
  head?

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• The nervous system is the information highway of
  the body. It consists of the central and
  peripheral nervous systems. The central nervous
  system is composed of the brain and the spinal
  cord. The peripheral nervous system is made up of
  neurons and nerve endings. The neuron is the
  basic unit and messenger of the peripheral
  nervous system. It is composed of dendrites, a
  cell body, an axon and axon terminals. When a
  nerve signal is sent by the nervous system, the
  dendrites receive the signal. The axon then
  transmits the nerve signal to the axon terminals
  which synapse with dendrites or other tissues
  such as a muscle.
• There are two types of axons, myelinated and
  unmyelinated. Unlike unmyelinated axons,
  myelinated axons have a sheath of fatty tissue
  called myelin wrapped around them. There are
  breaks in the myelin called Nodes of Ranviers
  which allow the nerve signal to jump from node to
  node. This causes the nerve signal to be
  transmitted faster.

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• The Nerve Action Potential
• Nerve action potentials are the electrical
  signals sent out by the body to control bodily
  processes such as muscular movement. They are
  controlled by ions and their concentrations
  around the nerve cell. They propagate uniformly
  along the nerve cell and are governed by the
  all-or-none phenomena. This means that a nerve
  action potential will not occur unless the
  depolarization threshold is met. The
  depolarization threshold is the potential that
  must be reached before depolarization of the
  nerve cell will occur. As a nerve action
  potential propagates along a neuron it goes
  through several phases which are shown in the
  graph below.  
• where(A) Resting state the membrane potential
  at rest(before the nerve action potential
  occurs)(B) Depolarization occurs when there is
  a drastic reversal in membrane potential(C)
  Repolarization occurs when the membrane
  potential is returning to the resting state(D)
  Undershoot occurs because the potassium gate
  stays open too long

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The Role of Ions

•   The concentration of ions around the nerve cell
  controls the action potential. There are two ions
  that are essential to a normal action potential.
  These ions are Sodium (Na) and Potassium (K).
  The Depolarization phase is controlled by Sodium.
  An external stimulus causes an influx of Sodium
  in the nerve cell. This depolarization, or action
  potential continues down the neural pathway,
  until it reaches its destination. After the cell
  depolarizes, it must repolarize to its resting
  potential before it can depolarize again. This
  repolarization phase is controlled by Potassium.
  An efflux of Potassium causes the potential to
  return to its resting state. The influx of
  Sodium ions and the efflux of Potassium ions are
  controlled by protein gates in the plasma
  membrane. The influx and efflux of these ions
  occurs by diffusion. Diffusion is the process by
  which ions move from an area of higher
  concentration to lower concentration. For
  example, after the nerve cell has been stimulated
  by an external stimulus, an influx of Sodium
  occurs because the extracellular concentration is
  higher than that of the intracellular.The
  Sodium-Potassium Pump is a separate protein
  channel that replenishes the extracellular
  environment with Sodium, and the intracellular
  environment with Potassium. This protects the
  extracellular environment from becoming saturated
  with Potassium and the intracellular with sodium.

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signals
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Camillo Golgi

• Biographical Sketch and Scientific Work
• Camillo Golgi was born in July 1843 in Corteno, a
  village in the mountains near Brescia in northern
  Italy, where his father was working as a district
  medical officer. He studied medicine at the
  University of Pavia, where he attended as an
  'intern student' the Institute of Psychiatry
  directed by Cesare Lombroso (1835-1909). Golgi
  also worked in the laboratory of experimental
  pathology directed by Giulio Bizzozero
  (1846-1901), a brilliant young professor of
  histology and pathology (among his several
  contributions, Bizzozero discovered the
  hemopoietic properties of bone marrow). Bizzozero
  introduced Golgi to experimental research and
  histological techniques, and established with him
  a lifelong friendship. Golgi graduated in 1865
  and was, therefore, a student during the last
  years of the fights for the independence of Italy
  (Italy became a united nation in 1870). Seated
  left to right Perroncito, Kölliker, Fusari In
  1872, due to financial problems, Golgi had to
  interrupt his academic commitment, and accepted
  the post of Chief Medical Officer at the Hospital
  of Chronically Ill (Pio Luogo degli lncurabili)
  in Abbiategrasso (close to Pavia and Milan). In
  the seclusion of this hospital, he transformed a
  little kitchen into a rudimentary laboratory, and
  continued his search for a new staining technique
  for the nervous tissue. In 1873 he published a
  short note ('On the structure of the brain grey
  matter') in the Gazzetta Medica Italiana, in
  which he described that he could observe the
  elements of the nervous tissue "studying metallic
  impregnations... after a long series of
  attempts". This was the discovery of the 'black
  reaction' (reazione nera), based on nervous
  tissue hardening in potassium bichromate and
  impregnation with silver nitrate. Such
  revolutionary staining, which is still in use
  nowadays and is named after him (Golgi staining
  or Golgi impregnation) impregnates a limited
  number of neurons at random (for reasons that are
  still mysterious), and permitted for the first
  time a clear visualization of a nerve cell body
  with all its processes in its entirety.

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Golgi
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Hippocampus
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Hippocampus

• hippocampus means "sea horse", and is named for
  its shape. It is one of the oldest parts of the
  brain, and is buried deep inside, within the
  limbic lobe. The hippocampus is important for the
  forming, and perhaps long-term storage, of
  associative and episodic memories. Specifically,
  the hippocampus has been implicated in (among
  other things) the encoding of face-name
  associations, the retrieval of face-name
  associations, the encoding of events, the recall
  of personal memories in response to smells. It
  may also be involved in the processes by which
  memories are consolidated during sleep. 

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Santiago Ramon y Cajal

• Cajal turned all his efforts to improving the
  silver nitrate technique. As Golgi had developed
  it, the staining involved including soaking the
  tissue in various substances. Cajal added several
  levels of preparation and made other refinements
  as the debate over the true structure of the
  central nervous system was intensifying. While no
  one had yet seen an entire nerve cell, or could
  tell whether it was independent or just part of a
  larger structure, some scientists already
  questioned the old "single network" theory.
  Fridtjof Nansen, better known today for his
  Arctic explorations, had joine several others in
  theorizing that nerve cells were independent,
  basic structures. Still, almost everyone else,
  including Golgi and Cajal, believed in the
  network structure.
• In 1887, Cajal became chair of Normal and
  Pathological Histology at the university in
  Barcelona. His most consuming work, however, was
  slicing, soaking, staining and affixing to glass
  slides, slivers of the cerebellum of the embryo
  of a small bird. Then he carefully drew what he
  saw under the microscope. He became an ardent
  convert to the independent-cell camp. In 1889, he
  was invited to show his drawings to the Congress
  of the German Anatomical Society at the
  University of Berlin. It could easily have been a
  disaster.
• The "short, powerfully built Spaniard with
  penetrating black eyes set up a small exhibit of
  drawings done on paper with colored inks,"
  Everdell writes, reconstructing the scene. Cajal
  had explanatory papers delivered to the German
  scientists in advance, but few who tried to read
  them knew any Spanish. Cajal delivered his speech
  in fractured French, but still won his case on
  the strength of his drawings and slides.
• "Each stained cell stood out perfectly against a
  background of staggering complexity," writes
  Everdell, "and no matter how many times the tiny
  fibers of one nerve cell met those of another,
  there was clearly no physical connection between
  them. The basic unit of the brainthe neuronhad
  been isolated." To this day, Cajals meticulous
  drawings are a defining fixture in neuroscience
  texts.

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The Nobel and Beyond

• In 1906, Cajal and Golgi shared a Nobel Prize for
  medicine. The two met for the first time in
  Stockholm, and while Cajal was tactful about
  sharing the prize, the two still disagreed about
  the structure of the brain. Golgis speech
  attacked Cajals concept of the independent
  neuron, while Cajals speech the next day
  defended it.
• Cajal continued his research, introducing four
  major new hypotheses, three of which are now
  accepted by neuroscientists. He died in Madrid in
  1934

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The Nervous Sytems

• Structure of the Nervous system
• 1. Central Nervous system (red)
• Brain
• Spinal Cord
• 2. Peripheral Nervous System (blue)
• Somatic
• sensory-afferents from skin/muscle
• motor-efferents controlling movement
• Autonomic
• sympathetic- Active in emergency "fight or
  flight" reactions
•  Parasympathetic-dominant in functions related to
  life maintenance (eating, storage of fuels)

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Medial Saggital View
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Coronal SectionMid-Brain/MRI
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• The brain is surrounded and protected by the
  rigid, bony skull and three membranes, or
  meninges. The tough, fibrous outer membrane is
  the dura mater. The intermediate membrane, named
  the arachnoid, is thin and weblike. The pia mater
  is the innermost covering and is the most
  delicate. It is molded to the shape of the brain.
  The cerebrospinal fluid (CSF) surrounds the brain
  and spinal cord and flows through open chambers
  in the brain, known as ventricles, and out an
  opening to the spinal cord. The brain actually
  floats in the shock-absorbing CSF, and is thus
  protected from trauma. The CSF also brings
  nutrients to the brain and removes wastes.

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Gyrus and Sulcus

• gyrus a fold or convolution in the cerebrum
• Sulcus a cleft or fissure in the cerebrum

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Central Sulcus
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Brain Development

• The brain develops, in utero, in three separate
  portions, reflecting evolutionary history the
  hindbrain, the midbrain, and the forebrain.

• The bottom-most part of the brain is the brain
  stem. The brain stem is attached to the spinal
  cord. It relays information between parts of the
  brain or between the brain and body and regulates
  basic body function. It is made up of the
  midbrain, medulla and the pons.
• Midbrain The midbrain contains the major motor
  supply to the muscles controlling eye movements
  and relays information for some visual and
  auditory reflexes.
• Pons The pons is a mass of nerve fibers that
  serves as a bridge between the medulla and
  midbrain above it. The pons is associated with
  face sensation and movement.
• Medulla The medulla (also known as the medulla
  oblongata) is located at the base of the brain
  stem and controls many of the mechanisms
  necessary for life, such as heartbeat, blood
  pressure and breathing.

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Hindbrain

• The hindbrain (the oldest part of the brain)
  develops into the cerebellum, the pons and the
  medulla.

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• The outermost and top layer of the brain is the
  cerebral cortex. The cerebral cortex is the most
  recently evolved and most complex part of the
  brain. As one moves lower into the brain, the
  parts have increasingly primitive and basic
  functions and are less likely to require
  conscious control.

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Cerebellum

• At the back of the head, in between the brain
  stem and cerebral cortex, is the cerebellum. The
  cerebellum controls balance and coordination and
  is where learned movements are stored. Purkinje
  neurons that control the refinement of motor
  movements are found in the cerebellum. The
  cerebellum receives input from many parts of the
  brain regarding pressure on the limbs, limb
  movement, and the position of the limbs in space.
  The dentate nucleus, located within the
  cerebellum, coordinates skilled movement. Damage
  to this region, as a result of HD, causes
  movements that were once smooth and refined to
  become jerky. Movements must also be constantly
  relearned.

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Lobes
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Frontal lobe

• Frontal Lobe - Front part of the brain involved
  in planning, organizing, problem solving,
  selective attention, personality and a variety of
  "higher cognitive functions" including behavior
  and emotions.
• The anterior (front) portion of the frontal lobe
  is called the prefrontal cortex. It is very
  important for the "higher cognitive functions"
  and the determination of the personality.
• The posterior (back) of the frontal lobe consists
  of the premotor and motor areas. Nerve cells that
  produce movement are located in the motor areas.
  The premotor areas serve to modify movements.
• The frontal lobe is divided from the parietal
  lobe by the central culcus.

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Others

• Occipital Lobe - Region in the back of the brain
  which processes visual information. Not only is
  the occipital lobe mainly responsible for visual
  reception, it also contains association areas
  that help in the visual recognition of shapes and
  colors. Damage to this lobe can cause visual
  deficits.
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• Parietal Lobe - One of the two parietal lobes of
  the brain located behind the frontal lobe at the
  top of the brain.
• Parietal Lobe, Right - Damage to this area can
  cause visuo-spatial deficits (e.g., the patient
  may have difficulty finding their way around new,
  or even familiar, places).
• Parietal Lobe, Left - Damage to this area may
  disrupt a patient's ability to understand spoken
  and/or written language.
• The parietal lobes contain the primary sensory
  cortex which controls sensation (touch,
  pressure). Behind the primary sensory cortex is a
  large association area that controls fine
  sensation (judgment of texture, weight, size,
  shape).  
• Temporal Lobe - There are two temporal lobes, one
  on each side of the brain located at about the
  level of the ears. These lobes allow a person to
  tell one smell from another and one sound from
  another. They also help in sorting new
  information and are believed to be responsible
  for short-term memory.
• Right Lobe - Mainly involved in visual memory
  (i.e., memory for pictures and faces).
• Left Lobe - Mainly involved in verbal memory
  (i.e., memory for words and names).

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• Studies done by Brodmann in the early part of the
  twentieth century generated a map of the cortex
  covering the lobes of each hemisphere. These
  studies involved electrical probing of the
  cortices of epileptic patients during surgery.
  Brodmann numbered the areas that he studies in
  each lobe and recorded the psychological and
  behavioral events that accompanied their
  stimulation.
• The Frontal Lobe contains areas that Brodmann
  identified as involved in cognitive functioning
  and in speech and language.
• Area 4 corresponds to the precentral gyrus or
  primary motor area.
• Area 6 is the premotor or supplemental motor
  area.
• Area 8 is anterior of the premotor cortex. It
  facilitates eye movements and is involved in
  visual reflexes as well as pupil dilation and
  constriction.
• Areas 9, 10, and 11 are anterior to area 8. They
  are involved in cognitive processes like
  reasoning and judgement which may be collectively
  called biological intelligence.
• Area 44 is Broca's area.
• Areas in the Parietal Lobe play a role in
  somatosensory processes.
• Areas 3, 2, and 1 are located on the primary
  sensory strip, with area 3 being superior to the
  other two. These are somastosthetic areas,
  meaning that they are the primary sensory areas
  for touch and kinesthesia.
• Areas 5, 7, and 40 are found posterior to the
  primary sensory strip and correspond to the
  presensory to sensory association areas.
• Area 39 is the angular gyrus.
• Areas involved in the processing of auditory
  information and semantics as well as the
  appreciation of smell are found in the Temporal
  Lobe.
• Area 41 is Heschl's gyrus, or the primary
  auditory area.
• Area 42 immediately inferior to area 41 and is
  also involved in the detection and recognition of
  speech. The processing done in this area of the
  cortex provides a more detailed analysis than
  that done in area 41.
• Areas 21 and 22 are the auditory association
  areas. Both areas are divided into two parts one
  half of each area lies on either side of area 42.
  
• Area 37 is found on the posterior-inferior part
  of the temporal lobe. Lesions here will cause
  anomia.
• The Occipital Lobe contains areas that process
  visual stimuli.
• Area 17 is the primary visual area.
• Areas 18 and 19 are the secondary visual areas.

• Brodmanns Areas

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Limbic System
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http//www2.umdnj.edu/neuro/studyaid/Practical200
0/practical2000.htm
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Rods and Cones

• two kinds of photoreceptors of vertebrate eyes
• rods very light sensitive, and sensitive to wider
  range of wavelengths, useful at night and under
  low light conditions, incapable of wavelength
  discrimination
• in moderate light, both rods and cones contribute
  to vision, at high light levels, rods saturate
• cones useful in higher light conditions,
  populations with differing wavelength sensitivity
  form basis for color vision

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The LGN

• Optic nerve fibres from the eyes terminate at two
  bodies in the thalamus (a structure in the middle
  of the brain) known as the Lateral Geniculate
  Nuclei (or LGN for short). One LGN lies in the
  left hemisphere and the other lies in the right
  hemisphere.

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Visual System
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Areas of the Visual Cortex
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Macque Monkey VS
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The binding problem

• Visual information processing takes place in
  parallel with different areas processing
  different image attributes. How does brain keep
  track of how these attributes relate to one
  another? Our phenomenal experience is of a
  singular unitary visual world, how does this
  relate to the multiple visual maps of our brain?

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LOLA