Motivation

Motivation

• Motivation is composed of two parts, Biological needs and Emotion.

• Both involve the hypothalamus and the autonomic NS.

• Emotional behavior also involves the cognitive structure of the brain along with the autonomic NS.

Motivational States (Biological Needs)

• Are controlled by basic homeostatic regulatory processes essential for survival; eating drinking and sex behavior.

• Motivation varies as a function of deprivation.• Motivational states are produced by changes

in internal conditions of the animal relative to a given set point of the regulatory process.

• Several of the most basic issues that surround internal motivational states are related to survival.

• Activities that enhance immediate survival (eating , drinking and sexing) are pleasurable and there is a great urge to repeat these behaviors.

• These states guide and shape our behavior for future action.

• Internal needs require organization of individual behavioral components into a specific goal-oriented sequence.

• Goal attainment increases the behavioral threshold leading to the drop off of the behavioral components necessary for goal attainment, leading to other classes of behavior (i.e. the animal stops eating).

Three functions of motivational states

• 1) The have a direct function: they steer behavior toward a specific goal.

• 2) Motivational states have an activating function: they increase general alertness and energize the individual to action.

• 3) Motivational states have an organizing function: combining individual behavioral components into a coherent, goal-oriented behavioral sequence.

Motivation is an inferred internal state

• One can only infer from what the organism does (behavior) as to the motivational state. Like learning it can not be seen.

The brain circuit involved

• The hypothalamus

• There are 19 different centers in the hypothalamus.

Hypothalamus Pituitary Interaction

• Brown study of Pineal - hypothalamus – Pituitary interaction

• End result, molecules move from the pineal gland to the pituitary by axonal transport and are released into the pituitary portal system .

• The molecules circulate through the circulatory system to reach their target organs.

Autonomic vs. Neural secretory systems

Skeltal vs. Autonomic systems

Parasympathetic vs. Sympathetic

• Parasympathetic – cholinergic – cranial sacral.• Sympathetic – adrenergic - Thorasico-lumbar .

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For the purpose of this class we will look at temperature regulation as the model system

• The concept of a feedback system

• The two system inhibit one another.

Antagonistic systems

• The parasympathetic and sympathetic system oppose one another.

Positive feedback

• For each increment of output, a part of that out put if fed back as input. The next increment of output is larger than the previous output. Leads to an ungoverned out but to self destruction.

Negative feedback

• For each increment of output, a part of that output if fed back as input. The next increment of output is smaller than the previous output. Drives the system to a very low state or zero.

Homeostasis

• First used by Claude Bernard as “milieu interne” or internal medium.

• Developed by Walter Cannon as “homeostasis” the attempts of the autonomic NS to bring the biological system back to the set point by use of the hypothalamus and the two divisions of the autonomic NS.

• One can use the concept of set point in many different context.: Glucostat,

The concept of set point for household use

• How does your household furnace act.• Set a temperature (the set point) by a movable

gage. Behind the gage is a tube of mercury. Rotating the front dial tilts the tube of mercury. The electrode at the bottom of the tube is then disconnected from the electrode at the top of the tube. The furnace turns on. Heat from the furnace expands the mercury. When contact is made between the two electrodes, the furnace shuts off.

The two regulatory system of the hypothalamus controlling temperature regulation

What behaviors are exhibited when one is cold?

• Biological (under the control of the posterior hypothalamus):

• Shiver; increase the rate at which glucose is metabolized, a byproduct is heat. When glucose stores are empty, metabolize free fatty acid.

• Piloerrection, trap air by changing position of hair on arms, legs and chest.

• Remove blood from periphery to core of the body to retain heat.

When cold

• Stimulating the posterior center gives rise to the shivering, piloerection, chnging blood compartments

• Behavioral:• Turn up the furnace.• Put on more close.• Move to a warmer room

What happens when on is hot?

• Sweat: put water on the skin.• Change blood pool from core to periphery.• The above two work together. Blood moved

to the skin of the periphery is a source of energy. It take 423 small calories to break the hydrogen bond that keeps water together on ones skin. That much energy is given up to remove one molecule of water from the skin

(evaporative sweating).

Eating Behavior

• Two active regions:• Ventromedial hypothalamus• Lateral hypothalamus

Ventromedial hypthalamus

• Lesion: leads to overeating (hyperphagia), sever obesity

• Stimulation: suppresses eating (aphagia)

Lateral hypothalamus

• Lesion: sever abstention of eating (aphagia)

• Stimulation: active eating

Lesion of the lateral hypothalamus

Emotions are a sub category of motivation

• Includes the hypothalamus, Autonomic NS and

• Portion of the thalamus, cingulate gyrus, amygdala, hippocampus and prefrontal cortex.

Papez Circuit

Papez named this circuit the Limbic system

A (above)

• A. (two slides above) Medial view of the brain shows the limbic lobe, which consists of primitive cortical tissue (lighter blue area ) that encircles the upper brain stem, The underlying structures (hippocampus and amygdala are not visible,

B (above)

• B. (two slides above) Interconnections of the deep-lying structures included in the limbic system. The prominent direction of neural activity in each trace is indicated by an arrow, but activity in the tracts is typically bidirectional

A system diagram of the limbic (dark arrow) and associated corteceis

• A proposed neural circuit for emotion. The circuit originally proposed by Papez is indicated by the thick lines; more recently described connections appear as thin lines.