HUMAN HEALTH PSYCHOLOGY PART 2: Biopsychological interactions
Chapter 1: Homeostatic regulation
1. Homeostatic regulation
• Homeostatic regulation
o = equilibrium/balance
o = the organism’s ability to keep its internal environment stable, despite changes in the external
environment
o Vb: temperature, blood pH, oxygen pressure, blood glucose
o → done by the Central nervous system
▪ = the interface for interaction between the internal & external environment
2. Stress
• ‘Stress’
o = threat to homeostasis
o → Has 2 aspects:
▪ 1) The Stressor
• Can be Physical (e.g. cold) : threatens homeostasis bottom up
• Can be Psychological (e.g. anticipation of pain, exam): threatens homeostasis top
down
▪ 2) Results in a Compensatory stress response
• = homeostatic machine (the inner body) tries to achieve homeostasis again
3. Feedback & feedforward control
• 2 ways to achieve homeostasis:
• To achieve homeostasis again: there is (Negative) feedback control of vb:
o 1) Temperature
o 2) Blood pressure
o 3) Blood pH levels/ arterial carbon dioxide pressure (PaCO2 )
• Feedback control: Temperature
o Start: normal body temperature (37°C/98,6°F)
o 1) Body temperature rises above normal → nervous system signals dermal blood vessels to dilate &
sweat glands to secrete → body heat is lost to its surroundings → body temperature drops toward
normal
o 2) Body temperature drops below normal → nervous system signals dermal blood vessels to
constrict and sweat glands to remain inactive
▪ → body heat is conserved → body temperature rises toward normal
▪ → or if body temperature continues to drop, nervous system signals muscles to contract
involuntarily → muscle activity generates body heat → body temperature rises toward
normal
• Feedback control: Blood pressure/ arterial pressure
o 1) Baroreceptors detect changes in arterial pressure / blood pressure
o 2) Heart sends via glossopharyngeal nerve signals to the medulla of the brain stem, the change in BP
o 3) Medulla of the brain stem signals via the vagus nerve, signals to the heart
o 4) Heat rate can be adjusted (vb slowed down when BP was too high)
• Feedback control: Blood pH/PaCO2
o 1) The increase in blood pH (caused by a decrease in blood CO2) is detected by the central &
peripheral chemoreceptors
▪ Vb decrease in blood CO2: when someone hyperventilates (too much & heavy breathing)
o 2) Resulting in decreased stimulation of the respiratory center
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, o 3) Decreased stimulation of the respiratory muscles by the respiratory center results in decreased
ventilation → which decreases gas exchange
o 4) Blood CO2 levels increase, causing a decrease in blood pH
o 1) The decrease in blood pH (caused by an increase in blood CO2) is detected by the central &
peripheral chemoreceptors
▪ Vb increase in blood CO2: when someone hypoventilates, when fire smoke
▪ The decrease in blood O2 is detected by the peripheral chemoreceptors
o 2) Increased stimulation of the respiratory center results
o 3) Increased stimulation of the respiratory muscles by the respiratory center results in increased
ventilation, which increases gas exchange
o 4) Blood CO2, decreases, causing an increase in blood pH
▪ Blood O2 increases
• To achieve homeostasis: there is also Feedforward control
o = Perturbations are being anticipated & corrected before they occur
o Happens via Classical conditioning as a viable mechanism
▪ Which can lead to vb “Exercise Hyperpnea” (breathing more)
• = increases in ventilation and heart rate occur at the onset of physical exercise, even
before an increase in PaCO2
4. Hierarchy of Homeostatic Controls
• Hierarchy of Homeostatic Controls (zie ppt): 5 levels
o 1) Individual organs have self-regulating capacity
▪ = determined by internal reflexes & the actions of the autonomic ganglia located in or near
the organs
o 2) Local regulation is modulated in turn by descending influences from the autonomic nervous
system, the brainstem, the hypothalamus, and higher centers in the CNS
4.1 Organ level: vital organs & local reflexes
• Intrinsic control mechanisms, at organ level
o = Organ adapts its functioning on its own in response to slow, local changes (without help of higher
instances vb the brain)
o Example: Frank Starling Mechanism (the heart)
▪ 1) If returning (venous) blood volume increases then atrium chambers fill more before next
beat
▪ 2) This more effective filling of atria creates more wall stretch and more muscle fiber tension
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, ▪ 3) Leads to more vigorous contraction on next beat
▪ 4) Left ventricle empties more completely
▪ 5) More effective blood flow into aorta & thus into the body
▪ → Heart responses to flow demands caused by systemic circulation
▪ → Only possible when conditions are relatively stable
4.2 Autonomic Nervous System: heart rate, heart rate variability
• Autonomic control mechanisms
o Autonomic Nervous System (ANS): Brainstem Controls , send Autonomous Messages to our body
• Autonomic Nervous System (ANS)
o = enervating the viscera/inner organs
o → gives limited awareness & voluntary control of the viscera → ‘AUTONOMIC’
o → working mechanism via Negative feedback control
o Has 2 different pathways
▪ 1) Sensory pathways (afferent: information up to the brain)
▪ 2) Motor pathways (efferent: information down from the brain to body)
o Divisions ANS:
▪ 1) sympathetic (SNS)
▪ 2) parasympathetic (PNS)
▪ 3) (enteric)
▪ → Function: Reciprocal regulation of organic function (zie hieronder)
o Each division has:
▪ 1) Sensory pathways from organs via ganglia to brainstem (afferent)
▪ 2) + - 4 response components:
• (a) descending autonomic and pre-ganglionic fibers
o (coming from hypothalamus/brainstem → via intermediolateral cell column
of spinal cord)
• (b) to a ganglion
o (relay station for as-/descending signals, also part of local regulation
system/reflexes)
• (c) to postganglionic fibers
o (messages more elaborated than in preganglionic fibers)
• (d) to neuroeffector junctions
o (postganglionic fiber/receptor at target tissue, nerve impuls → motor
action)
• Sympathetic division ANS
o Origin of preganglionic fibers: thoracic & lumbar regions of spinal cord
o Structure: short preganglionic fiber, long postganglionic fiber
o Reciprocal function:
▪ Dilates pupil, decreases salivation, increases breathing rate
▪ Increases heart rate, narrows blood vessels,
▪ Slows digestive activity
▪ Stimulates secretion of epinephrine and norepinephrine
▪ Causes salt& water retention in kidney
▪ Relaxes bladder muscles
▪ Inhibits defecation
o Ratio of 1:10 pre- vs postganglionic nerves, meaning:
▪ Has general, broad influence on viscera (many organs can be reached)
▪ Allows extensive linkages across widely distributed ganglia
▪ Allows closely integrated actions across different organs (‘in sympathy’)
o Neurotransmission:
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, ▪ Acetylcholine (preganglionic)
▪ Norepinephrine (postganglionic): smooth muscle cells, cardiac muscles and pace maker:
activating function
▪ Except:
• (a) sympathetic preganglionic nerves release acetylcholine at adrenal medulla →
release of catecholamines (Nor-/Epinephrine) into blood
• (b) sympathetic nerves release acetylcholine at sweat glands (hands, feet)
o More active during stress → Crucial for Fight/flight responses
▪ Noticeable effects
• Pupils dilate, dry mouth, neck + shoulder muscles tense, heart pumps faster, chest
pains, palpitations, sweating, muscles tense for action, breathing fast + shallow
hyperventilation, oxygen needed for muscles
▪ Hidden effects
• Brain gets body ready for action, adrenaline released for fight/flight, blood pressure
rises, liver releases glucose to provide energy for muscles, digestion slows or ceases,
sphincters close & relax, cortisol released (depresses the immune system)
• Parasympathetic (vagal) division ANS
o Origin of preganglionic fibers: cranial & sacral regions of spinal cord
o Structure: long preganglionic fiber, short postganglionic fiber
▪ + Ganglia more specific and nearer to target organ
o Reciprocal Function:
▪ Constricts pupil, increases salivation, decreases breathing rate
▪ Slows heart rate, widens blood vessels
▪ Increases digestive activity
▪ Contracts bladder muscles
▪ Stimulates defecation
o Ratio of 1:3 pre- vs postganglionic nerves, meaning:
▪ localized, specific actions directed at one organ
o Neurotransmission
▪ Acetylcholine preganglionic
▪ Acetylcholine (postganglionic): smooth muscle cells & cardiac muscle and pace maker:
inhibitory influence
o Less active during stress
o Supporting energy conservation, reproduction, digestion
o Opm: Vagus nerve = biggest parasympathetic nerve
• Poll: Which part of the ANS dilates (widens) the pupils in our eyes? → sympathetic division
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