PSYC104 Lecture Notes - Lecture 3: Medial Forebrain Bundle, Lateral Hypothalamus, Motor System
1 Jun 2018
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Week 3 Lecture 3
MOTIVATION PART II:
Motivation to Drink and Eat
▪ Need = any condition that is necessary for life, growth and wellbeing
▪ Motive = an internal process that energises and directs behaviour
o If neglected, a need will produce damage that disrupts the biological or
psychological wellbeing
o HOWEVER - Motivation states provide the impetus to act before such
damage occurs
o Damage can be either to the body, thus motives arise from physiological
needs
o Damage can be to the self, thus motives arise from psychological needs
o Damage can also occur to ones relationship to the social world, thus motives
arise from social needs (preserve values, beliefs)
o Biological functions (eating, drinking and sleeping) are regulated by
HOMEOSTASIS (it literally means standing still which is bullshit)
o Homeostasis: the ody’s tedey to aitai a relatively ostat
state that permits cells to live and function
o Cells in the body can only survive within a narrow range of conditions:
o At the right temperature
o Bathed in the right amount of fluid
o Humans have evolved systems for regulating these conditions, which operate
like a thermostat (or a detector)
o Homeostatic systems include several important features:
o Set point – a biological optimal level that the system strives to
maintain
o Feedback mechanisms – provide ongoing information regarding the
state of the system with respect to variables being regulated
o Corrective mechanisms – restore the system to its set point when
needed
o We know that our bodily systems are inevitably displaced from homeostasis,
either from changes in environmental conditions or through ones own
behaviours
o Deprivation can also result simply as a result of the passage of time – the
cause of that:
o Thus, the body has both a tendency to maintain a steady state as well as a
means to generate the motivation necessary to energise and direct
homeostasis-restoring behaviours
Physiological Needs:
o These describe a deficient biological condition. These occur with tissue and
bloodstream deficits, as from water loss, nutrient deprivation or physical
injury
o We are constantly losing water within our body
o If water loss occurs below an optimal homeostatic level (around 2%)
this creates the physiological need that underlines thirst.
find more resources at oneclass.com
find more resources at oneclass.com
THIRST
o What is thirst?
o Defined as a consciously experienced motivational state/drive that
readies the body to perform behaviours needed to replenish water
deficits
o DRIVE is the conscious manifestation of an underlying biological need
that has motivational properties
▪ When salient enough to grab our attention, drive energises an
animal into action, and directs activity toward particular
behaviours that are capable of servicing and satisfying
particular bodily needs
• Our body has internal mechanisms that grab attention
to find and consume water
o How does thirst arise?
o In our bodies, water lies inside (intracellular fluid contributes 40% of
body weight) and outside (extracellular fluid contributes 20% of our
body weight) our cells
o Thirst can thus arise from these two distinct sources:
▪ When intracellular fluid needs replenishment because of
cellular dehydration – osmometric thirst arises
▪ When extracellular fluid needs replenishment (from bleeding
or vomiting) – volumetric thirst arises
▪ Research studies conclude that osmometric thirst is the
primary cause of thirst activation – thirst comes from mostly
dehydrated cells
o How does our body know when to stop drinking?
o Humans are capable of drinking to excess
o NEGATIVE FEEDBACK SYSTEMS – hoeostasis’ physiologial stop
system
▪ The body must also prevent drinking so much water that
dysfunction occurs
▪ A research study conducted multiple experiments;
1. The results – if water was arranged to pass through
mouth but not to reach the stomach, animals
would drink 4 times the amount of water
• This suggests that water passing through the mouth
provides a weak means of thirst
2. Results – when researchers arrange for water to
pass from mouth to stomach but not intestines,
bloodstream or cells, animals drink twice as much
water as normal
• This suggests the stomach has a weak thirst inhibitory
mechanism
3. Results – animals allowed to drink water that
passes through mouth, stomach, intestines and
into extracellular fluid but the water was a salt
solution which means that:
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Motivation to drink and eat: need = any condition that is necessary for life, growth and wellbeing, motive = an internal process that energises and directs behaviour. Physiological needs: these describe a deficient biological condition. These occur with tissue and bloodstream deficits, as from water loss, nutrient deprivation or physical injury: we are constantly losing water within our body. If water loss occurs below an optimal homeostatic level (around 2%) this creates the physiological need that underlines thirst. In response to this, it releases a hormone into blood plasma that sends a message to the liver to conserve water: kidneys also release water if we are low on fluid. Drinking occurs for three main reasons: water replenishment which satisfies physiological needs, sweet taste, cause of addiction to a substance in the water and not the water itself. Intracranial self-stimulation (electrical brain stimulation: drug self-administration.
