College of Education

School of Continuing and Distance Education 2014/2015 – 2016/2017

PSYC 223

Research Methods

Session 9 – REGULATORY AND NON-REGULATORY MECHANISMS

Lecturer: Dr. Adote Anum, Dept. of Psychology Contact Information: aanum@ug.edu.gh

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

INTRODUCTION Topic One

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

TEMPERATURE Topic One

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

SLEEP Topic three

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

HUNGER Topic Four

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

THIRST Topic Five

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