Chapter Three: The Biological Bases of Behavior

D. The Brain and Behavior

Specific structures in the three major regions of the brain are associated with different functions

1. The Hindbrain
2. The Midbrain
3. The Forebrain

Contents

The Hindbrain

The hindbrain includes the cerebellum and two structures found in the lower part of the brainstem: the medulla and the pons.


Medulla

• Attaches to the spinal cord.

• Unconscious but essential functions.
  • Reguating Breathing.
  • Maintaining muscle tone.
  • Regulating circulation.

• See view below.

Pons

• A bridge that connects the brainstem with the cerebellum

• Involved with sleep and arousal.

• See view below.

Cerebellum

• Sense of coordination.

• Sense of equilibrium.

• Assists in the execution of commands for muscular movements
  • One of first structures affected by alcohol
  • Damage also disrupts fine motor skills like typing or picking your nose.

	3-D image of Medulla, Pons, and Cerebellum in the Brainstem: Click the "Label All" button to see the parts labeled.

The Midbrain

The midbrain is strategically placed in between the hindbrain and the forebrain -- get it? --that's why they call it the "midbrain." Fortunately it does more than hold the hindbrain and forebrain together -- it is responsible for sensory processes.

Areas of the midbrain

• Dopamine releasing neurons which help with voluntary movements controlled by the forebrain.

• Reticular formation which is involved in:
  • Best known -- for regulation of sleep and wakefulness
  • Lesser known -- for modulation of muscle reflexes, breathing, and pain perception.

The Forebrain

Just about everything else in the brain, 70% of the neurons in the CNS, is organized into the cerebrum, the thalamus, hypothalamus, limbic system, and the Louisiana Purchase.


The Thalamus: A Way Station

3-D image: It's the Purple structure

The Hypothalamus

Although you might think we are referring to the "fat" thalamus, we are really referring to "under" the thalamus. It might be the underthalamus, but it has some very important functions.


3-D image: It's the Yellow structure


Functions of the Hypothalamus

• Controls the autonomic nervous system.

• Link between the brain and the endocrine system.

• Key SURVIVAL functions -- the "4 F's"
  • fighting
  • fleeing
  • feeding
  • "mating"

The Limbic System: The Seat of Emotion

The limbic system did not get its name from a Caribbean dance routine, or a sure-fire gambling strategy, or the part of your back that goes out when you reach 30.

• The real of the limbic system.
  
  
• Our text"spicture of the limbic system is in figure 3.18.
  
  
  

The following Web sites give three dimensional views:

Overview
Closeup
2.9M

Hippocampus

• Important in the formation of memories.

• Is damaged in Alzheimer's disease.

Medial forebrain bundle

Home of the "pleasure centers" that has millions of laboratory rats pressing levers thousands of times per hour to activate ESB. This one of the few studies the rats actually volunteer for!

• May not be anatomical structures so much as neuron circuits using dopamine

The Cerebrum: The Seat of Complex Thought

The largest and most complex part of the brain.

• Cerebral cortex
  
  
• Cerebral hemispheres
  • The corpus callosum connects the hemispheres.

  • Another view of the corpus callosum

  • for discussion of the functional specialization of each hemisphere.

Lobes - each hemisphere is divided into four parts or lobes. Summary figure of the lobes (3.21


Occipital lobe

• Primary visual cortex
• to Chapter 4 (not active at this time).

Parietal lobe

• Primary somatosensory cortex.
• Integrates visual inputs.
• Monitors body's position in space.

Temporal lobe

• Primary auditory cortex

Frontal lobe

• Primary motor cortex, figure 3.22
• Prefrontal lobe is a mystery area when higher complex thoughts are suppose to take place.

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