THE BRAIN

READING ASSIGNMENT:
                TEXT, CHAPTER 48, PAGES  979-989

I. Evolution of the Brain

The most primitive vertebrate brain consists of three irregular swellings, anterior bulges of the dorsal hollow nerve cord, named:  hindbrain, midbrain, and forebrain.

 
 
 

A. Hindbrain

1. Medullar oblongata and the pons

2. Cerebellum

B. Midbrain

C. Forebrain

1. Thalamus

2. Hypothalamus

3. Cerebrum

i.    Cerebral cortex
ii.   Cerebral hemispheres
iii.  Four lobes of the cerebral cortex
a. Front lobe motor functions, integration of muscular activity, speech
b. Parietal lobe sensory functions, touch and taste.
c. Temporal lobe auditory
d. Occipital lobe visual

II. Chemical Activity of the Brain

A. Neurotransmitters in the brain
    In nervous system, neurotansmitters are released into synapse by neuron.  Some of these chemicals (neurotansmitters) may

    have a profound effect on behavior, if their synthesis in brain nerons is altered by drugs:

        i.e.  Excessive use of amphetamines would increase the synthesis of dopamine and norepinephrine (neurotansmitter),

               which would cause psychotic behavior, and antipsychotic drugs such as thorazine would block receptors for

               dopmine and norepinephrine, therfore, Thorazine is used as antipsychotic drugs to treat psychotic behavior.

                If there is too little dopamine in the brain, it may lead to Parkinson's disease---- the loss of muscular control,

                particularly in the face.

B. Internal opiates

Opiates are derivatives of opium, such as morphine.  They come from the poppy plant and have been used to control pain.

Why opiates are considered as painkiller?

Opiates act by binding to specific opiate receptors in the limbic system of the brain.  Sensory receptors transmit the pain impulse to the brain, but essentially, the circuit is shut off by the binding of the opiates.
 

Natural painkillers produced by our brain tissue: enkephalins and endorphins.

Recentaly, researchers have discovered that natural substances produced by our body can bind with opiate receptors.  One class of natural painkillers, enkephalins is found in brain tissue.  Another class, endorphins, has been isolated from the pituitary gland.  It is hypothesized that these internal opiates occur at low levels, but their synthesis increases under conditions of pain and stress.

This finding could explain the variation in individual's tolerance of pain.

III. The Dream Debate

A. Five stages of sleep

B. Two hypotheses on the fundamental nature of dreams

1. Psychoanalytical model of Sigmund Freud
    Freud predicts that dreams are the conscious expression of our unconscious fantasies.

2. Modern activation synthesis model

    This model assumes that dreams are random occurrences produced when the hindbrain stimulates the forebrain through the

    reticular activating formation.  THe forebrain then tries to make sense out of disparate sets of data.

    Think of a dream that you had recently and interpret it in the light of the psychoanalitical model.

GLOSSARY

Brainstem The hindbrain and midbrain of the vertebrate central nervous system.  In humans, it forms a cap on the anterior end of the spinal cord, extending to about the middle of the brain.

Cerebellum part of the vertebrate hindbrain located dorsally; functions in unconscious coordination of movement and balance.

Cerebral cortex The surface of the cerebrum; the largest and most complex part of the mammalian brain, containing sensory and motor nerve cell bodies of the cerebrum.

Cerebrospinal fluid Formed in the brain by filtration of the blood, circulating through the central canal and ventricles, conveying nutrients, hormones, and white blood cells across the blood-brain barrier to different parts of the brain.  It also functions as a shock absorber, cushioning the brain.

Cerebrum The dorsal potion of the vertebrate forebrain, composed of right and left hemispheres; the integrating center for memory, learning, emotions, and other highly complex functions of the central nervous system.

Corpus callosum - A large band of axons, communicating between two cerebral hemispheres of the cerebrum.

Endorphin A hormone produced in the brain and anterior pituitary that inhibits pain perception.

Limbic system A group of nuclei (clusters of nerve cell bodies) in the lower part of the mammalian forebrain that interact with the cerebral cortex in determining emotions.

Medullar oblongata The lowest part of the vertebrate brain; a swelling of the hindbrain dorsal to the anterior spinal cord that controls autonomic, homeostatic functions, including breathing, heart and blood vessel activity, swallowing, digestion, and vomiting.

Neurotransmitter A chemical messenger released from the synaptic terminal of a neuron at a chemical synapse that diffuses across the synaptic cleft and binds to and stimulates the postsynaptic cell.

REM-Sleep - A stage of our sleep which is characterized by rapid eye movement, fluctuations in heart rate, blood pressure and respiration.  We can recall dreams from this stage.

Ventricles series of hollow compartments continuous with the central canal of the spinal cord and are filled with cerebrospinal fluid.