PSYC 223
Research Methods
Session 9 – REGULATORY AND NON-REGULATORY
MECHANISMS
Lecturer: Dr. Adote Anum, Dept. of Psychology
Contact Information: [email protected]
College of Education
School of Continuing and Distance Education
2014/2015 – 2016/2017
Session Overview
• The human body has a remarkable ability to regulate bodily
functions. These include maintaining body temperature
within a specified range, trigger hunger, regulate fluid levels,
and heart and respiration. In this session, we will describe the
role of the brain and nervous system in body regulating body
mechanisms. We will focus on a few of these body
mechanisms.
Slide 2
Session Outline
The key topics to be covered in the session are as follows:
• Introduction
• Temperature regulation
• Sleep
• Hunger
• Thirst
Slide 3
Reading List
• Read Chapter 15 of Biological Psychology 9th Edition by J. W.
Kalat; pages 295 – 321
• Read Chapter 12 & 13 of An Introduction to Brain and
Behavior 4th Edition by Kolb and Wishaw
Slide 4
Topic One
INTRODUCTION
Slide 5
Homeostasis
Homeostasis –
• Introduced by Walter Cannon (1929)
• Refers to the body’s regulation of internal body
states within a fixed range
– Temperature
– Water
– Heart rate
Topic One
TEMPERATURE
Slide 7
Core temperature
• The core temperature of the human body is
37°C
• The core of the human body includes the organs
of the thorax, abdomen and the head
• This is where the vital organs are located
• Their enzyme systems must operate in optimum
conditions
• The periphery of the body can withstand some
deviation from the core temperature
Body Temperature
• Normal internal body temperature is
370C.
– Temperatures above this:
• leads to denature (losing ability to
function) of enzymes
– Temperatures below this:
• low down metabolism and affect the
brain.
Temperature Regulation
• Human beings are homeothermic – that they use
physiological mechanisms to regulate body
temperature
• About 2/3s of body energy is used to regulate body
temperature
Temperature Regulation – Brain
Mechanisms
• Hypothalamus monitors body temperature by
monitoring its own temperature
• Preoptic area (POA) regulated autonomic reactions
to temperature changes
• Lateral hypothalamus regulated behavioral reactions
to temperature changes
• Receptors on the skin also regulated temperature
Topic three
SLEEP
Slide 12
Endogenous Cycles
• Cycles or rhythms that last or occur seasonally.
• In humans we are interested cycles that last for
about a day or 24 hours – known as circadian
rhythms.
– These rhythm are consistent for every individual in most
environments
Mechanism of Biological Clock
• Role of Suprachiasmatic Nucleus (SCN)
• Melatonin
• What is jet lag?
– a disruption of circadian rhythms when time zone is
changed.
• Sleepiness during the day, sleepiness at night, increased
stress, impaired concentration
Sleep
•
•
•
•
Stages of Sleep
Stage 1
Stage 2
Stage 3 slow wave sleep (physiological activities slow
down
• Stage 4 slow wave sleep
REM Sleep
• REM Sleep (paradoxical sleep)
– Irregular wave, low voltage, fast waves that indicate
increased neuronal activity.
Brain Structures
• The Brainstem and sleep
– RAS
– Pontomecenchphalon - sends activation into the
forebrain. Maintains arousal during wakefulness
– Locus Coeruleus
Sleep Disorders
• Insomnia
– the inability to get the amount of sleep you need to wake
up feeling rested and refreshed, is the most common sleep
complaint. Insomnia is often a symptom of another
problem, such as stress, anxiety, depression, or an
underlying health condition.
Sleep Disorders
• Sleep apnea
– Frequent cessation of breathing during sleep
– It leads to frequent arousal and therefore lack of rest
following sleep.
– Can be fatal if breathing stops for a longer period
Slide 20
Sleep Disorders
• Narcolepsy
– A sleep disorder that causes excessive sleepiness and
frequent daytime sleep attacks.
– The exact cause is unknown.
– In some patients, narcolepsy is linked to reduced amounts
of a protein called hypocretin, which is made in the brain.
What causes the brain to produce less of this protein is
unclear.
– Can occur even in the middle of an activity like eating or
talking
Slide 21
Topic Four
HUNGER
Slide 22
Hunger
• What is Hunger?
– Hunger is the motivation for us to be able to know that we
need to get the nutrients in our body
• How do we know we are hungry?
– Biological - Cannon and Washburn (1912) came up with
the stomach contraction theory which states that we know
we are hungry when our stomach contracts.
– Cognitive
• Hunger can be triggered by the site of food or people eating
– Learned
• E.g, planned eating time like lunch triggers hunger
Brain Mechanisms
• Brain stem
– Ingestive behaviors are evolutionarily old;
– thus controlled by “older” parts of the brain (mid- and
hindbrain)
– Decerebrate animals (animals in which the brain stem has
been severed from the forebrain) can still perform basic
ingestive behaviors (e.g. chewing, swallowing) but not
more complex ingestive behaviors (e.g. foraging)
Brain Mechanisms
• Hypothalamus
– The arcuate nucleus - part of the hypothalamus receives
signals about hunger and satiety
– lesions of lateral hypothalamus - little or no interest in
eating
– Lesions (damage) of ventromedial nucleus of the
hypothalamus - excessive eating (could not recognize
satiety)
• Orbitofrontal cortex
– “processes information about the potential reward value
of food”
Homeostatic Regulation
• Glucose (glucostatic theory)
– specialized glucose receptors monitor extent glucose taken
up by cells to be used for energy
• Lipids (lipostatic theory)
– set-point for body fat
– deviations “initiate compensatory behaviours to return to
homeostatis”
Physiological Mechanisms
• Gastric factors
– The stomach contains receptors that can detect the presence of nutrients
– Receptors trigger release of ghrelin is secreted which activates a hunger
signal
• Intestinal factors
– Afferent axons from the duodenum (first portion of small intestine) are
sensitive to the presence of glucose, amino acids, and fatty acids
– Entry of food into the duodenum suppresses food intake in rats; rats fitted
with a gastric fistula ( a tube that drains contents out of the stomach)
continue to consume food (this method is called sham feeding)
– The duodenum controls the normal rate of stomach empyting by secreting
a peptide called cholecystokinin (CCK),
External Motivations
• When did you eat lunch?
• Where you hungry?
• Classical conditioning
– hungry at mealtimes even though metabolic rates differ
– food - related cues (sight and smell)
• Learned preferences
– observational learning
What starts a meal?
• Social and environmental factors
– Often we eat out of habit or because of some stimuli present in our env’t (e.g.
clock, smell food)
– Meal schedule very important: rarely adjust times of meals, but can adjust size
of meals
– If we have eaten recently or if a previous meal was large, we tend to eat a
smaller meal
– However, due to other social factors, such as parental cues (“finish your
plate”) or peer influence, satiety signals can be ignored
– DeCastro and DeCastro (1989) found that the amount of food eaten was
directly proportional to the amount of other people who were present during
a meal
Topic Five
THIRST
Slide 30
Drinking
• 2 types of thirst
– Osmometric (osmotic) thirst –
• A form of thirst arising from depletion of fluid within cells and triggered by
osmoreceptors
• Osmoreceptors – neuron that detects changes in the solute conc.
• Osmoreceptors located in the anterior hypothalamus, one of the
circumventricular organs (CVO’s)
– Volumetric thirst
• Produced when blood plasma volume is low
• Leads to both thirst and salt appetite
• 2 types of receptor systems: Renin-angiotensin system & atrial
baroreceptors
Drinking
• Neural mechanisms of thirst
– Sensory info from atria is conferred to the nucleus of the solitary tract
(NTS) in the medulla
– AngII crosses weak BBB near CVO’s to provide thirst and salt appetite
signal (esp. via subfornical organ (SFO))
– Neurons in SFO project to MnPO (median preoptic nucleus)
References
• Read Chapter 15 of Biological Psychology 9th
Edition by J. W. Kalat; pages 295 – 321
• Read Chapter 12 & 13 of An Introduction to Brain
and
Behavior 4th Edition by Kolb and Wishaw
Slide 33