HSE208: Practical Investigation of Cardiovascular Responses to Stress

This practical report investigates the cardiovascular system's response to stress by analyzing heart rate, systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) under various stressors such as postural changes, cold pressor tests, and isometric handgrip exercises. The aim was to determine the regulation of blood pressure during physiological challenges, elaborating on heart regulation through practical experimentations using a sphygmomanometer and stethoscope. The results and discussion address orthostatic hypotension, the effects of cold environments on the cardiovascular system, and the involvement of the nervous, endocrine, immune, and limbic systems in mediating stress responses. The sympathetic nervous system's role in releasing norepinephrine and adrenaline, the endocrine system's regulation of metabolic functions through glands like melatonin and pituitary glands, and the overall integrated response to stress are thoroughly examined.

Physiological Response to Stress
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Introduction
Cardiovascular system functions as a network pathway for transportation of substrate and
oxygen to the peripheral organs and excretion of waste products such as heat and carbon dioxide.
This report is mapped to investigate the functioning, to express and elaborate the cardiovascular
reactions due to stress. In order to determine the holistic and the most appropriate stressors that
affect the blood pressure and the heart rate, several practical measures have to be performed. The
measures include; systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR)
and also determine the mean arterial pressure (MAP).
Aim
The main aim of the practical was to determine the actual regulation of blood pressure at
the time when a person is experiencing some physiological challenges. The practical aimed
elaborating the understanding of the heart regulation through practical experimentations of
diastolic and systolic blood pressures and the heart rate using the sphygmomanometer and
stethoscope. All the practical test was carried out including the handgrip, change in posture and
cold pressor test with an overall objective in human physiology to acquire the integrated result of
how blood pressure in human circulation system behaves due to stressors and how it is regulated.
Question 1:
Orthostatic hypotension is the decrease in systolic blood pressure (SBP) of 20 mm Hg or
in the other hand the decrease of the diastolic blood pressure (DBP) of 10 mm Hg after standing
for around three minutes in comparison to the blood pressure while in a supine or sitting
position. According to the experimental result, orthostatic hypotension did not occur because the
difference between the SBP while at the supine position and after standing is less than 20 mmHg

and also the difference of the blood pressure in DBP while at supine and after standing is less
than 10 mmHg [2].
Question 2:
Extreme cold environment leads to the activation of the neuron that results to the
sympathetic stimulation and thus the release of noradrenaline. The sensory afferent nerves
stimulate the activation of the sympathetic system which results to vasoconstriction. The pulse
pressure is elevated due to the release of the catecholamine release. The ventricles are filled by
the high pressure to a greater level, but the increase in the afterload reduces the stroke volume.
Immersion in cold water leads to changes in the physiological processes as the regulatory system
detects and responds to maintain a stable environment for the body homeostasis. The capacity to
respond depends on the integrity of the cardiovascular system to control the heart rate and blood
pressure through the mechanism that regulates water levels in the blood. The nervous system
responds to the changes in the blood pressure due to immersion while the renal and hormonal
responses function to mitigate the changes for a long period [4].
Question 3:
Some of the physiological systems that have worked together during the practical
investigation to evaluate the effect of stress in the body include; the nervous system, endocrine
system, immune system and the limbic system [1].
Nervous system
The sympathetic nervous system is the one associated and response to fight and stress. Various
neural synapses release substances specifically norepinephrine and adrenaline in many body
organs and tissues which prepares the body for the immediate physical movement and rapid

metabolic change. Sympathetic branch of the central nervous system triggers the catabolic
functioning when an element of threat within the body [3].
The Endocrine system
The endocrine system consists of four glands that are located in the whole body which are
responsible for regulating the metabolic functions due to endurance such stress. These glands
include; melatonin, hypothalamus, serotonin and pituitary glands. Serotonin; is a
neurotransmitter associated with moods- when in low levels is related to depression and it is
affected by food consumed and stress hormones. Melatonin is related to moods, sleep, and
consciousness. Pituitary glands, through the hypothalamus commands it releases ACTH which
then triggers the adrenal glands to secrete stress hormones. Hypothalamus is associated with
emotional status and releases substances to pituitary glands that activate the flight-or-fight
response [3].

Reference
1.) Ellis BJ, Del Giudice M. Beyond allostatic load: Rethinking the role of stress in
regulating human development. Development and Psychopathology. 2014 Feb;26(1):1-
20.
2.) Oscar CG, de Figueirêdo Müller-Ribeiro FC, de Castro LG, Lima AM, Campagnole-
Santos MJ, Santos RA, Xavier CH, Fontes MA. Angiotensin-(1–7) in the basolateral
amygdala attenuates the cardiovascular response evoked by acute emotional stress. Brain
research. 2015 Jan 12;1594:183-9.
3.) Levi L, editor. Stress and distress in response to psychosocial stimuli: laboratory and
real-life studies on sympatho-adrenomedullary and related reactions. Elsevier; 2016 Jan
26.
4.) Lovallo WR. Stress and health: Biological and psychological interactions. Sage
publications; 2015 Feb 10.