Chapter Four: Neurons, Hormones, and the Brain

A Tour Through the Brain

INTRODUCTION

Let's take a tour through the mysteries of the human brain.

WHAT'S AHEAD

• Which brain part acts as a "traffic officer" for incoming sensations?
• Which brain part is the "gateway to memory" -- and what cognitive catastrophe occurs when it is damaged?
• Why is it a good thing that the outer covering of the human brain is so wrinkled?
• How did a bizarre nineteenth-century accident illuminate the role of the frontal lobes?

KEY CONCEPTS

Introduction/Overview
The Brain Stem
The Cerebellum
The Thalamus
The Hypothalamus and the Pituitary Gland
The Limbic System

The Amygdala
The Hippocampus

The Cerebrum

The Cerebral Cortex
Lobes of the Cortex

Click on Titles or Areas to jump to text descriptions

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Introduction/Overview [p.128]

INTRODUCTION

Localization of function means that different parts of the brain perform different functions.

KEY CONCEPTS EXPLAINED

This notion can be traced back to the much maligned concept of phrenology in chapter 1 (rewind to chapter 1)

LINKS About Phrenology

• wwwlink: The theory of phrenology gets a tip of the hat from modern neuroscience (Smithsonian Magazine).
• wwwlink: A Phrenology Home Page

The Brain Stem [p.128]

INTRODUCTION

At the base of the skull, the brain stem rises out of the spinal cord and is responsible for basic bodily functions.

KEY CONCEPTS EXPLAINED

...Medulla

Automatic behaviors such as breathing and heart rate.

...Pons

Sleeping, waking and dreaming

...Reticular Activating System (RAS)

Screens information and arouses higher centers if necessary.

GLOSSARY

		brain stem
		medulla
		pons
		reticular activating system (RAS)

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

LINKS About the brain stem

• wwwlink: Interesting history of hanging but the "geocites" pages are very irritating because of the pesky advertising.
• wwwlink: Traumatic brain injuries can have significant impact on behavior.

The Cerebellum [p.129]

INTRODUCTION

The "lesser brain" has some important functions.

KEY CONCEPTS EXPLAINED

• Controls sense of balance and coordinates muscle movements
  
  
  • Trivia: the cerebellum is one of the first parts of the brain to be affected by alcohol. That is why you are likely to get "tipsy" in a very short period of time.
    
    
• Involved in remembering certain simple skills and acquired reflexes.
  
  
• Damage to cerebellum would lead to problems with fine motor skills, like writing with a pencil or picking your nose, as well as trying to ride a bike.

GLOSSARY

cerebellum

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

LINKS About the cerebrum

• wwwlink: Cerebral Palsy .

The Thalamus [p.129]

INTRODUCTION

The busy traffic officer of the brain.

KEY CONCEPTS EXPLAINED

• Directs sensory messages to higher centers.
  
  
• The olfactory bulb is not a flowering plant but the private switching station for smells (bypasses the thalamus)

GLOSSARY

thalamus

	3-D image of Thalamus: Its the Purple Structure. Click the "Label All" button at the bottom of the page to see the parts labeled.

The Hypothalamus and the Pituitary Gland [p.129]

Hypothalamus

INTRODUCTION

Involved with the drives associated with survival.

KEY CONCEPTS EXPLAINED

..The hypothalamus plays a key role in:

• Hunger
  
  
• Thirst
  
  
• Emotion
  
  
• Sex/reproduction
  
  
• Regulates body temperature
  
  
• Controls the autonomic nervous system.

	Memory Aide: The Four F's
	Feeding
	Fighting
	Fleeing
	Mating

GLOSSARY

hypothalamus

	3-D image of Hypothalamus: Its the Yellow Structure. Click the "Label All" button at the bottom of the page to see the parts labeled.

Pituitary Gland

INTRODUCTION

The "Master Gland -- no, it's not what you think."

KEY CONCEPTS EXPLAINED

• On command from the hypothalamus, the pituitary gland secretes hormones that affect the other endocrine glands.
  
  
• rewind to hormones and endocrine gland section.

GLOSSARY

pituitary gland

The Limbic System [p.129]

INTRODUCTION

The Limbic System did not get its name from a Caribbean dance routine, or a surefire gambling system, or the part of your back that goes out when you reach 30.

KEY CONCEPTS EXPLAINED

Structures in the limbic system are involved in emotions like fear and rage. Pleasure centers - All is not negative, however, as "pleasure centers" also exist in this system. Laboratory rats have been known to press a lever until exhausted in order to receive electric stimulation to this part of their brain. This is one of the few laboratory experiments that the rats will eagerly volunteer for.

.The Amygdala [p.130]

...INTRODUCTION

Associated with arousal and regulation of emotion.

...KEY CONCEPTS EXPLAINED

• Evaluates sensory information, determines its significance, and initiates a response.
  
  
• Mediates anxiety and depression

.The Hippocampus [p.130]


..INTRODUCTION

"Gateway to Memory".

..KEY CONCEPTS EXPLAINED

• Enables us to form new memories about facts and events.
  
  
• H.M.: The removal of his hippocampus led to his no longer remembering new experiences for longer than 15 minutes. He was stuck in a time warp from his life before the operation.
  
  
• May help in giving memories the necessary period of consolidation that is require for long term memory.

GLOSSARY

		limbic system
		amygdala
		hippocampus

	3-D Overview image of the Limbic System: Click the "Label All" button at the bottom of the page to see the parts labeled.
	3-D Closeup

LINKS About the limbic system

• wwwlink: Drugs and the "pleasure centers" .

The Cerebrum [p.131]

INTRODUCTION

The largest and most complex part of the brain. The cerebrum is divided into cerebral hemispheres connected by the corpus callosum. The two hemispheres have somewhat different operations (lateralization).

The Cerebral Cortex [p.131]

INTRODUCTION

The thin "bark" of cells covering the cerebrum which are largely responsible for higher mental functions.

KEY CONCEPTS EXPLAINED

• This thin layer of densely packed cells covers the cerebrum and contains 3/4 of all cells in the brain.
  
  
  • Gray matter - cell bodies in the cortex.
  • White matter - myelin covered axons prevail.
    
    
• Heavily wrinkled so that its billions of neurons can fold and fit into relatively small skulls that can pass through the birth canal.

The Lobes of the Cortex [p.132]

INTRODUCTION

There are four distinct regions of the cortex.

KEY CONCEPTS EXPLAINED

Occipital Lobe	Visual Cortex where visual signals are perceived.
Parietal Lobe	Sensory Motor Cortex where information about pressure, pain, touch, and temperature are processed.
Temporal Lobe	Memory, perception, emotion. Auditory Cortex - processes sound. Wernicke's Area - language comprehension
Frontal Lobes	Motor Cortex - controls voluntary muscles. Broca's Area - handles speech production. Planning, thinking creatively, and taking initiative.

..Association Cortex are areas responsible for higher mental processes:

...Prefrontal Cortex

• Personality processes are located here.
  
  
• Phineas Gage's splitting headache reduced his social judgment, rational decision making, the ability to make and carry through plans
  
  
• Ability to do a series of tasks and stop at the proper time.
• Ability to do a series of tasks and stop at the proper time.
• Ability to do a series of tasks and stop at the proper time.....

GLOSSARY

		cerebrum
		cerebral hemispheres
		lateralization
		occipital lobe
		parietal lobe
		temporal lobe
		frontal lobe

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Next Topic - The Two Hemispheres of the Brain.......... ............... Chapter Contents