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THE BRAIN

BRAIN REGIONS & STRUCTURES

MODULE 1.4B

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LOWER LEVEL BRAIN STRUCTURES�LEARNING TARGETS:

LT 1.4-4

LT 1.4-5

LT 1.4-6

Explain how the hindbrain, midbrain, and forebrain apply to behavior and mental processes.

Describe the structures of the brainstem, and explain the functions of the brainstem, thalamus, reticular formation, and cerebellum.

Explain the limbic system’s structures and functions.

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Subdivided Brain

Hindbrain - direct essential functioning like breathing, heart rate, sleep-wake cycle, and balance and coordination.
Midbrain - connects the forebrain to the hindbrain for communication. Enables seeing & hearing.
Forebrain - complex functioning such as cognitive activities, sensory functions, and voluntary movements.

Compared to other species, the human forebrain has evolved into a more sophisticated area.

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Older/Lower Level Brain Structures

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Primitive Parts of Brain

Like the oldest part of a tree is in the center that is then surrounded by newer growth, the older parts of the brain that we share with other animals, are found at the central lower region of the brain.

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The Brainstem�

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Hindbrain Structures

Brainstem

medulla
reticular formation
pons

Cerebellum

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Medulla

Breathing
Heart rate
Digestion
Other vital reflexes

swallowing
coughing
vomiting
sneezing

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Pons

Helps coordinate movements on left and right sides of the body
Sends motor info to Cerebellum

postural reflexes which help you maintain balance while standing or moving

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Reticular Formation/Activating System

Network of neurons in the brainstem (and thalamus)
Sleep and arousal
Attention – filters incoming sensory info

Turns up and down sensory information

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Cerebellum

Word actually means “little brain”
Place where procedural memories are kept.

how to ride a bike, swim

Coordinated, rapid voluntary movements

playing the piano, kicking, throwing, etc.

Damage to cerebellum

jerky, exaggerated movements
difficulty walking
loss of balance

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Midbrain Structures

Middle Region involved in visual & auditory processing.
Early warning system gets you ready for flight or fight

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Forebrain Structures

Thalamus
Limbic System
Cortex

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Thalamus

Sensory control center in brain
Sends sensory info to parts of the brain that can understand it
Receives replies back from higher brain areas and sends them to lower level structures
Like the Post Office taking incoming messages and delivering them

_______

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The Limbic System

Emotional Center:

Thalamus
Hypothalamus
Amygdala
Hippocampus

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Parts Of The Limbic System

Hippocampus

Helps us form new episodic or semantic (knowledge based) memories.
What happens when this is damaged?

Remember the video of Clive Wearing & EP?

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Parts of the Limbic System

Amygdala

Fear
Aggression

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Amygdala and Emotion

Helps us identify emotion from facial expressions

Amygdala damage makes this task difficult

(click on picture to advance photos)

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Parts of the Limbic System

Hypothalamus

Link between the Nervous System & Endocrine System.
Provides us with pleasurable feelings for doing the things that keep our species alive.

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Hypothalamus

Involved in the 5 F’s

1. Food/Thirst,
2. Flight,
3. Fight,
4. Furnace (Temperature)
5. Fornication

sexual behavior
hunger, thirst
sleep
water and salt balance
body temperature regulation
circadian rhythms
role in hormone secretion

The hypothalamus is made up different subregions or nuclei. These nuclei generally differ in terms of gross anatomy and function.

Sexual behavior: The medial preoptic and medial anterior hypothalamic nuclei of the hypothalamus are heavily involved in mating behaviors of animals. Damage to these areas results in a loss of mating behaviors. Electrical stimulation of these areas (or insertion of sex hormones in these areas) can elicit sexual behaviors.

Hunger: Lesions to the hypothalamus can lead to severe obesity or extreme weight loss, depending upon the region damaged.

Thirst: Electrical stimulation of the hypothalamus can cause an animal to start drinking even in animals that have plenty of water in their systems. Neurons in the supraoptic nucleus of the hypothalamus are sensitive to changes in the osmolarity of blood. These neurons control the secretion of vasopression, which is more commonly known as "anti-diuretic hormone" or ADH. ADH acts in the kidney to increase fluid retention.

Sleep:

Temperature regulation: Your body tries to keep the same body temperature regardless of how hot or cold it is outside. The hypothalamus helps maintain a constant body temperature. Hypothalamus contains temperature-sensitive neurons. Neurons in the posterior hypothalamus become active when you are cold; whereas, heat activates the anterior hypothalamus. Changes in body temperature can cause the hypothalamus to initiate such behaviors as shivering, hunger, adrenaline secretion and fever to help you get back to the proper body temperature.

Circadian rhythms: the suprachiasmatic nucleus (or SCN) of the hypothalamus is thought to be involved in regulating the body's natural 24 hour rhythms.

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Hypothalamus – Pleasure Center of the Brain

Rat with an electrode implanted in a reward center of its hypothalamus, See some actual footage of this.
Rat readily crosses an electrified grid, accepting the painful shocks, to press a lever that sends electrical impulses to its "pleasure centers."
How often did the rat press the lever in an hour?
1001 times!!! It finally collapsed from exhaustion (Olds 1958)

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Hypothalamus and Hormones�The Feedback Loop

Feedback Loop lets brain know when to start & stop secreting hormones
Hypothalamus tells pituitary gland to send messages to other glands to release their hormones.
Once hormones are released, hypothalamus registers this and sends message to pituitary gland to send continue or stop messages out to glands.

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DAILY

DOUBLE

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What are the 5 F’s that the Hypothalamus influences?

Food/Thirst
Flight
Fight
Furnace – Body temperature
Fornication