Anatomy and Physiology

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Anatomy and Physiology

• 9.4 CNS (contd)

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Warm Up 01.26.07

• Explain what a nerve impulse is.

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Diencephalon

• A small but important part of the brain located
  between the midbrain and the cerebrum
• Consists of two major structures hypothalamus
  and the thalamus

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Hypothalamus

• This is located below the thalamus
• The pituitary gland is an extension of the
  hypothalamus
• It is one of the smallest parts of the brain, but
  it is one of the most important parts of the
  brain it has major control over virtually all
  of the internal organs
• Including heartbeat, constriction of the blood
  vessels and contractions of the stomach and
  intestines

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Hypothalamus (contd)

• Some neurons make hormones
• Ex. Antidiuretic hormone (ADH) affects the
  volume of urine excreted (so it plays an
  essential role in maintaining water balance)
• So, the hypothalamus indirectly helps control the
  functioning of every cell in the body

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Thalamus

• Dumbbell shaped-section of gray matter
• Composed mostly of dendrites and cell bodies of
  neurons that have axons extending up toward the
  sensory areas of the cerebrum

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Functions of the Thalamus

• 1. Helps produce sensations
• Relay impulses from the sensory organs
• 2. Associates sensations with emotions
• 3. Plays a part in the arousal or alerting
  mechanism

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Cerebellum

• The cerebellum is the second largest structure of
  the brain
• Lies under the occipital lobe of the cerebrum
• Gray matter composes the outer layer and white
  matter composes the majority of the interior

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Function of the Cerebellum

• Most of our observations come from disorders we
  note what goes wrong when a part of the
  cerebellum is damaged and discern what its
  function is
• The cerebellum is essential to normal movement
• Ex. A tumor of the cerebellum is cause an
  individual to stumble and lose his balance and he
  loses his ability to make precise movements

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Functions of the Cerebellum

• Most obviously
• Produce smooth coordinated movements
• Maintain equilibrium
• Sustain normal postures
• Recent studies suggest there may be more!
• Perhaps an overall coordinating function for the
  whole brain

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Cerebrum

• The largest and uppermost portion of the brain
• The ridges are called convolutions or gyri and
  the groves are called sulci
• The deepest sulci are called fissures
• The longitudinal fissure divides the brain into
  right and left hemispheres
• The halves are almost separate structures held
  together by the corpus callosum

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Lobes of the Cerebrum

• Two deep sulci divide each hemisphere into four
  major lobes and each lobe into a number of gyri
• The lobes are named for the bones that lie over
  them
• Frontal lobe, parietal lobe, temporal lobe and
  occipital lobe

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Cerebral Cortex

• A thin layer of gray matter (neuron dendrites and
  cell bodies) makes up the surface the cerebral
  cortex
• White matter (bundles of nerve fibers) composes
  the interior
• Within this interior, there are some islands of
  gray matter the cerebral nuclei or the basal
  ganglia (responsible for automatic movements or
  postures)

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Function of the Cerebrum

• The neurons do not function alone but they
  function with other parts of the brain
• Page 278, Second column, Here are some of the
  things you could not do
• Consciousness, thinking, memory, sensations,
  emotions and willed movements, vision, hearing,
  speech