HUMAN BRAIN

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HUMAN BRAIN
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HUMAN BRAIN

• Three major structural components
• Cerebrum (top) - large dome-shaped cerebrum
  Responsible for intelligence and reasoning.
• Cerebellum (lower right) - smaller somewhat
  spherical - Helps maintain balance and posture.
• Brainstem (center) - Medulla is involved in
  maintaining involuntary functions such as
  respiration, and the thalamus acts as a relay
  center for electrical impulses traveling to and
  from the cerebral cortex.

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BRAINSTEM
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BRAINSTEM

• Structure of the Brain Stem
• The brain stem is the lowest part of the brain
  and serves as the path for messages traveling
  between the upper brain and spinal cord. It
  supports basic and vital functions such as
  breathing, blood pressure, and heart rate, as
  well as reflexes like eye movement and vomiting.
  The brain stem consists of the medulla, pons, and
  midbrain.

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CEREBRAL CORTEX
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CEREBRAL CORTEX

• Functions of the Cerebral Cortex
• Many motor and sensory functions have been
  "mapped" to specific areas of the cerebral
  cortex. Both hemispheres are similar with the
  Left Hemisphere serving the right side of the
  body while the Right Hemisphere serves the left
  side of the body. Areas of association, located
  mainly in the frontal cortex, are responsible for
  the functions of thought and emotion and for
  linking input from different senses. The areas of
  language have been pinpointed to be located on
  the cortex.

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PITUITARY GLAND
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PITUITARY GLAND

• Pituitary Gland
• The Pituitary secretes hormones that control the
  activity of other endocrine glands and regulate
  various biological processes. It secretes growth
  hormone (which stimulates cellular activity in
  bone, cartilage, and other structural tissue)
  thyroid stimulating hormone (which causes the
  thyroid to release metabolism-regulating
  hormones) antidiuretic hormone (which causes the
  kidney to excrete less water in the urine) and
  prolactin (which stimulates milk production and
  breast development in females).

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LEFT/RIGHT BRAIN FUNCTIONS
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DIVISIONS OF THE BRAIN

• Hindbrain - controls structures essential for
  survival, ex. breathing, blood circulation,
  digestion, balance, posture, and muscular
  coordination.
• Midbrain - Controls motor responses, and some
  auditory and visual responses, such as the
  regulation of the size of the pupil of the eye.

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DIVISIONS OF THE BRAIN

• Forebrain - Controls complicated patterns of
  behavior and are the source of higher level
  activities that differentiate man from other
  animals. Thalamus, hypothalamus and cerebrum are
  located in this area. The hypothalamus is
  responsible for controlling processes such as
  body temperature, metabolism, hunger and thirst.
  It also plays a key role in regulating emotional
  behavior and changes in mood.

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MAJOR AREAS OF CORTEX

• Frontal Lobe - responsible for primary motor
  functions
• Temporal Lobe - responsible for auditory
  stimulation
• Occipital Lobe - responsible for vision
• Parietal Lobe - responsible for body senses

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HOW HUMANS ARE DESIGNED TO BE BIPEDAL
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THEORY

• Early origins of bipedalism began approximately
  four million years ago when the ancient hominid
  adapted to a life under the trees as opposed to
  living in them.
• It is believed that a small pocket of primates
  became isolated, the climate changed and the
  forest began to dwindle and these primates no
  longer needed to be afraid to search for food on
  the ground.

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THEORY

• The earliest fossil hominid Ardipithecus ramidus
  was bipedal and about 4 feet tall. It is believed
  that ramidus was a forest dweller.
• Bipedal adaptation appeared to be completed a
  long time ago. The earliest bipedal animal was
  different from how humans look today. While the
  early hominid was bipedal his skull closely
  resembled the ancient apes. It was only through
  the evolutionary process that his brain size
  expanded and his intellectual abilities
  increased. The facial characteristics of modern
  man are about 100,000 years old.

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THEORY

• By walking on the hindlimbs, the forelimbs were
  able to be used for the fine manipulation of
  things, such as carrying food back to a base
  camp. This allowed the earliest hominids to
  become more autonomous.
• The origin of bipedalism is considered one of the
  major steps in human evolution.

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EVOLUTIONARY PROCESS
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EVOLUTIONARY PROCESS

• Autralopithecus afrensis is ancestor to all
  hominids. He looks modern below the neck and the
  knee looks like a modern human joint. The pelvis
  is adapted for upright walking and the foot has
  both modern and primitive features with some of
  the bones being curved like someone who may have
  climbed trees.
• Overall, the skeleton of early humans differ from
  modern man in their limb proportions with their
  arms being similar to ours but their legs being
  considerably shorter.

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EVOLUTIONARY PROCESS
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EVOLUTIONARY PROCESS

• Differences are evident between early hominids
  and human feet. In an early hominid weight was
  carried along the side of the foot, and the push
  was passed through the middle of the row of toes
  while in modern humans the weight is transmitted
  along the outside of the foot, internally across
  the ball of the foot, and push-off occurs by the
  big toe.

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EVOLUTIONARY PROCESS

• Since some curvature in the foot bones have been
  found it is speculated there was a transition
  between primitive and modern features that
  evolved into bipedalism.
• Early hominids and modern human knee joints are
  similar having a carrying angle that is common
  of human bipeds. In the chimpanzee the thigh and
  shin bones form a straight line. This makes it
  easier for weight to be born on all four limbs.
  For bipedalism it is easier when the thigh and
  shin bones form an angle. The thighs then come
  together at the knees, and the feet trace a
  single straight line.

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EVOLUTIONARY PROCESS

• Early hominids pelvis is shallow and rounded
  with the femurs tilting towards the midline.
  Thus, the trunk is supported by the pelvis and
  body weight is transmitted downward through the
  knees when the individual stands erect.
• In bipedal hominids, the pelvis assumes a broad,
  shallow, bowl-like shape with a widened but
  shortened ilium, there is forward curvature of
  the lower spine and further flattening of the
  thoracic cage which helps transmit weight of the
  trunk directly to the legs.

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EVOLUTIONARY PROCESS

• Bipedalism improved a hominids ability to see
  over tall grasses, to wade into deeper water and
  to better seek protection from predators.
• Bipedalism made it easier for adults to carry
  food manually to their young children, allowed
  for closer social relationships and probably
  contributed to an increased longevity.

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HISTORY OF MAN

• SPECIES TIME PERIOD
• Ardipithicus ramidus 5 to 4 million years
• Australopithecus anamensis 4.2 to 3.9 million
  years ago
• Australopithecus afarensis 4 to 2.7
  million years ago
• Australopithecus africanus 3 to 2 million
  years ago
• Australopithecus robustus 2.2 to 1.6
  million years ago
• Homo habilis 2.2 to 1.6
  million years ago
• Homo erectus 2.0 to 0.4
  million years ago
• Homo sapiens archaic 400 to 200 thousand years
  ago
• Homo sapiens neandertalensis 200 to 30 thousand
  years ago
• Homo sapiens sapiens 200 thousand years ago to
  present

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HISTORY OF MAN

• Ardipithecus ramidus - bipedal, 4 feet tall,
  herbivore, had feet on one end, used club.
• Australopithecus anamensis - body showed bipedal
  features, but the skull closely resembled the
  ancient apes.

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HISTORY OF MAN

• Australopithecus afarensis - retained apelike
  face with a sloping forehead, a distinct ridge
  over the eyes, flat nose and a chinless lower
  jaw. Brain capacity of 450 cc and was between
  3'6" and 5' tall. Fully bipedal and thickness of
  its bones was quite strong. Its build was about
  the same as modern human. Head and face were
  proportionately much larger. Heavier male,
  smaller female.

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HISTORY OF MAN

• Australopithecus africanus - bipedal, larger in
  body size and brain size was slightly larger, up
  to 500cc. Brain not advanced enough for speech.
  Molars were a little larger than afarensis and
  much larger than modern humans. This homonid was
  a herbivore and the shape of the jaw was now like
  the human.
• Australopitchecus aethiopicus - Lived between 2.6
  and 2.3 million years ago. Had huge molars and
  jaws and ate a rough and hard to chew diet. Brain
  size still 500 cc with no speech functions.

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HISTORY OF MAN

• Australopithecus robustus - Body similar to
  africanus but larger and more massive skull and
  teeth. Face was flat with no forehead. Brain was
  525 cc with no indication of speech.
• Homo habilis - Brain size eventually rose to 800
  cc and some speech developed. Believed Broca area
  of brain evolved. About 5' tall and weighed about
  100 pounds. Tools were found with homo habilis
  fossil remains which led to the nickname of
  "handy man".

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HISTORY OF MAN

• Homo erectus - Brain size was 900cc and had
  speech abilities. Developed tools, weapons and
  fire and learned to cook his food. Turned to
  hunting for his food and migrated out of Africa
  into China and Southeast Asia and developed
  clothing for northern climates. Face had massive
  jaws with huge molars, no chin, thick brow ridges
  and a long low skull.
• Homo sapiens archaic - Brain averaged 1200 cc and
  had capacity of speech. Skulls more rounded with
  smaller features. Skeleton shows a stronger build
  than modern human but was well proportioned.

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HISTORY OF MAN

• Homo sapiens neandertalensis - Brain sizes
  averaged larger than modern man at about 1450 cc.
  Head was longer and lower than modern man. 5'6"
  tall with an extremely heavy skeleton that showed
  attachments for massive muscles.
• Homo sapiens sapiens - modern human with a brain
  of 1350cc.

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COMPARISON BETWEEN MODERN MAN AND MODERN APES

• Differences
• Human walks upright
• Facial features
• Similarities
• Sexual practices
• Sense of family