Integration and Control IV: The Vertebrate Brain

1
Integration and Control IVThe Vertebrate Brain

• By Katie Buskirk

2

• The human brain weighs about 1,400 grams equal
  to about 3 pounds
• Consisting of white and grey matter
• White matter- fiber tracts that are white in
  color because of lipid rich myelin sheaths
• Gray matter- cell bodies of nearly 100 billion
  neurons and supporting cells of the neuralgia
• Necessary for integration, and physiological
  activities. Ex memory, thought, consciousness,
  and emotions

www.csm.ornl.gov/ SC99/VHwall.html
3
The Structural Organization of the Brain An
Evolutionary Perspective

• Development of the brain starts as a series of
  three bulges at the the anterior of the dorsal
  neural tube.
• The groove at the surface of the embryo closes it
  give rise to the tubular structure from where the
  brain and spinal cord (central nervous system)
  develop.
• Cavities or Ventricles inside the anterior bulges
  are present in the mature brain and are filled
  with cerebrospinal fluid which also fills the
  spinal cord
• In lower vertebrates the three bulges retain in a
  linear arrangement Ex fish, and frogs
• In higher vertebrates the bulges fold over on
  each other in the course of development. Ex
  Humans, dogs, and birds
• These three bulges are still visible in all
  brains and are known as the Hindbrains, Midbrains
  and Forebrain

4
Hindbrain and Midbrain

• Knobby extension of the spinal cord- the
  brainstem and a convoluted structure- the
  cerebellum
• Brainstem- contains nuclei involved with reflexes
  and controls sensory and motor neurons
• Medulla- posterior portion of brainstem it
  control respiration and heartbeat
• Many fibers cross over between the right and left
  side. The right side receives while the left side
  send and nice versa
• Cerebellum- is a dorsal outgrowth of primate
  hindbrain.Controls the muscles and movement of
  them
• Auditory messages go through the pons

5
Hindbrain Midbrain
www.sciencemaster.com/.../ life/brain_02c.gif
www.sciencemaster.com/.../ life/brain_02b.gif
6
Forebrain

• Two parts
• -Diencephalon
• -Telecephalon

www.med.umich.edu/.../ Page20620Forebrain.gif
7
Diencephalon

• Contain the Thalamus and the Hypothalamus
• Thalamus- two egg shaped grey matter is main
  relay center between the brainstem and higher
  brain centers
• Hypothalamus- responsible for activities such as
  hunger, pleasure, pain, and anger. Controls
  thermostat and ADH hormone and oxytocin

8
Telencephalon

• Towards the back of the brain and has evolved the
  most.
• In primitive vertebrates it dealt with olfactory
  or rhinencephlon info
• Corpus Striatum- most primitive structure which
  controls stereotyped behavior of animals
• Cerebrum- central part, largest part and folded
  into two hemispheres
• -Cerebral cortex- upper surface of the cerebrum
• Corpus Callosum- fibers that connect the cerebral
  hemispheres

9
http//faculty.washington.edu/chudler/nsdivide.htm
lstruc
10
Reticular Activating System

• Monitors incoming stimuli and analyzes it
• It is a core of tissue that runs through the
  brainstem and neurons in thalamus are extensions
• Ex being able to sleep through normal sounds
  like TV, planes or even alarm clocks, but walking
  up to a faint scream or the turn of door knob

11
Limbic System

• Subcortial neurons- form loop around the upper
  Diencephalon. Links hypothalamus with the
  cerebral cortex.
• Believed to translate emotions like hunger into
  complex action like seeking food.

12
Cerebral Cortex

• Gray matter, thin layer
• Fish and amphibians dont have any while reptiles
  and birds only have indications of a cortex
• Primitive mammals have a smooth cortex while homo
  sapiens have a complex cortex
• In homo sapiens there are four lobes the frontal,
  parietal, temporal, and occipital. They are on
  both hemisphere

13
(No Transcript)
14
Motor and Sensory Cortices

• Information is based on humans that have areas of
  the cortex destroyed, or animals that have been
  stimulated in that area
• Anterior to Central sulcus in frontal lobe is
  where skeletal muscles are controlled and each
  point of cortex controls a different part of the
  body
• Parietal lobe- sensory cortex, and responds to
  the stimuli of touch as well as taste, pain and
  temperature.
• Temporal Lobe- in within the lateral sulcus and
  is the auditory cortex. Receives and send neurons
  to the ears
• Occipital Lobe- is the visual cortex and controls
  sight. The fovea represents 1 of area of retina
  and makes up 50 of visual cortex

15
The Perception of Form

• Each of the regions of the visual cortex to which
  different regions of the retina project contains
  a variety of cells, different groups of which
  respond to different types of visual stimuli
• David H. Hubel and Torsten N. Weisel at Harvard
  University first revealed visual processing in
  experiments. They tested the responses of a cat
  to different stimuli by using microelectrodes to
  record the responses of individual cells in the
  visual cortex.
• Visual info occurs in the retina before it is
  passed on to the ganglion cells which bring it to
  the brain. The ganglion cells synapse with other
  neurons in the geniculate nucleus and then pass
  the info on to the visual cortex

16
www.yorku.ca/ eye/cortrfld.gif
17
Left Brain Vs Right Brain

• Two areas related to speech are in the left
  hemisphere they are Broca and Wernickles areas
• Brocas Area- controls movements of muscles of
  lips, tongue, jaw, and vocal cords. Damage in
  area results in slow and labored speech
• Wernickles area- surrounds auditory cortex.
  Damage results in meaningless but fluent speech,
  and comprehension of written and spoken words is
  impaired.
• Left hemisphere is seem as the dominant while the
  right is described as minor or passive
• The right hemisphere controls musical talent in
  humans, but damage to it results in getting lost
  easily, gets disoriented in new area, trouble
  recognizing familiar voices and faces.
• Though in young children areas of the right
  hemisphere can take over the damaged of the left
  hemisphere and have normal speech because its a
  developmental process

18
Left Vs. Right

• Fernando Nottebohm at Rockfeller University
  studied song birds and saw that a lesions in the
  left hemisphere greatly distorted the song though
  canaries with right hemisphere lesions had minor
  changes in their song
• He also found that the size of the region of the
  song nuclei vary from season to season and bird
  to bird. The size of the nuclei increases during
  the spring and decreases in the fall
• Females sing very little and have ¼ the size of
  males and males with small song centers have a
  small repertories

19

www.ling.upenn.edu/.../ broca_wernicke_speak.gif
20
Split Brain

• The two hemispheres of the brain are connected by
  the corpus callosum though in cases of epilepsy
  it has been found that severing it lessens the
  severity of epileptic attacks
• Roger Sperry and coworkers at California
  Institute of Technology launched many tests on
  these patients.
• It showed that once the corpus callosum was cut
  the two hemispheres were functionally separate
  and behave like two separate brains
• If patients are asked to identify objects with
  touch they can only name the right hand not those
  in the left hand because the information from
  right hand goes to left side of brain and left
  hand goes to right brain.
• If left hand is placed on a plastic number 2 they
  are unable to verbally identify but can readily
  tell by extending two fingers

21
www-rohan.sdsu.edu/.../ split_brain_larson.jpg
22
Intrinsic Processing Areas

• Intrinsic processing can receive and process
  information from neurons in other areas of brain
  do not receive directly relayed sensory.
  Similarly the transmit information to neurons in
  other area but not leading out of the brain
• Mapping the areas is very complex and biologist
  are just beginning to gain some insight.
• Posterior region of parietal lobe and lower
  portion of temporal lobe receive signals from
  neurons of visual cortex
• In primates the proportion of the cerebral cortex
  devoted to intrinsic process is much higher and
  even higher in humans
• About half the total area involved is located in
  the frontal lobes which was the part of the brain
  tat developed most rapidly during evolution.
• These activities controls our capacity to
  understand

23
Learning and Memory

• Learning is defined as a change in behavior based
  on experience
• Karl Lashey wanted to locate the physical change
  and trace memory or engram. He concluded he could
  not find physical form and that is was all over
  the brain
• Two types of memory. Short and long
• Short term memory is looking up a phone number
  and remembering it long enough to call though if
  you call the number repeated times it is
  transferred to long-term memory
• The establishment of pathways involves
  alternations in the synapses by which neurons
  communicate
• A blow to the head might cause amnesia which is
  lose of all past long term memories though new
  are able to develop, though Injury to hippocampus
  (part of limbic system) affect short term
  memories but not long term

24
www.morphonix.com/.../ specimens/hippocampus.gif
25
Anatomical Pathways of Memory

• The principle areas involved in memory are
  hippocampus (seahorse), amygdala (almond),
  thalamus, basal forebrain, and prefrontal cortex
• Goes from sensory cortex to Hippocampus and
  amygdala then to the basal forebrain and the
  prefrontal cortex
• The Basal forebrain is the area in which
  degenerates during Alzhemiers disease
• Amygdala is region responsible for remembering
  not only visual images about the beach but also
  sound, taste and smell
• Wilder Penfield found that some patients when
  stimulated in certain areas of the cortex they
  felt like they were actually reliving past events

26
www.psy.ohio-state.edu/ psy312/images/cogbrain.gif

27
Synaptic Modification

• It is easier to tract neurons in invertebrates so
  they are used to test behavior circuits.
• Eric Kandel at Columbia University worked with
  sea horse and their gill withdrawal. When poked
  on the underside they quickly draw up though if
  repeated poked they become habituated to the
  stimulus and dont draw up
• Habituation is regarded as a form of learning and
  is associated with a gradual decrease in the
  amount of neurotransmitters released
• Alternation in the strength of synaptic
  transmission are critical in memory and learning
• Though models are still trying to be made
  perfected some factors involved are second
  messengers.
• Learning and Memory have not been fully uncovered
  yet though neurobiologists are on a new levels of
  understanding what is going on in the brain

28
The End!!
www.th.physik.uni-frankfurt.de/.../ brain.jpg