NURSING 2LA2 Chapter Notes - Chapter 9: Lightdark, Endocrine System, Sickle-Cell Disease
16 Sep 2018
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- Interactions between body cells and its many organ systems require a level of homeostasis to be maintained
during the many changes that occur in the internal and external environments
o Homeostasis requires feedback control systems that regulate cellular function and integrate the
function of different body systems
CONSTANCY OF THE INTERNAL ENVIRONMENT
- The environment in which the body cells live is the local fluid environment, not the external environment that
surrounds the organism
- Claude Bernard was the first to describe the importance of a sable internal environment, he termed it milieu
interieur
o Recognized that body fluids surrounding the cells (extracellular fluid) and the organ systems provide
means for exchange between internal and external environments
▪ Cells get their nourishment from it and secrete their waste into it
- A multicellular organism can only survive as long as the internal environment can provide survival needs of
individual cells
- Walter B Cannon proposed homeostasis was achieved though coordinated physiologic processes that
oppose change
o Processes were automatic
o Involves resistance to both internal and external disturbances
▪ When a factor shifts homeostasis in one direction, expect mechanisms that have an opposite
effect
o As long as the responding mechanism to the initiating disturbance can recover homeostasis, the
integrity of the body and its normality is retained
CONTROL SYSTEMS
- Homeostasis depends on control systems that regulate body function
o Control system consists of a collection of interconnected components that function to keep a
parameter of the body constant
o They regulate cellular function, control life processes, and integrate functions of the different organ
systems
- Neuroendocrine control systems are biochemical messengers that influence behavior, which mediate the
physical, emotional, and behavioral reactions to stressors (stress response)
o Each stress response involves a sensor to detect change, integrator to sum incoming data and
compare it with normal, and effector to reverse the change
- Sometimes, with complex stressors, the stress response can’t restore balance, and the physical and psych
impact presents itself years later it’s important to identify early negative experiences and treat them
- Trying to create feeling of balance within through journal, communication, etc should facilitate some
physiological benefits as the brain will attempt to reorganize itself by changing prefrontal cortex and neural
pathways
o neuroplasticity emotional balance, flexibility, immune and cardiac function, and empathy ability
FEEDBACK SYSTEMS
- Many control systems operate by negative feedback mechanisms which return values to set point if they
deviate
o eg. If blood glucose it stimulates in insulin blood glucose
o if blood glucose it prohibits insulin release and glucagon stimulates insulin release from liver
- Positive feedback mechanisms interject instability rather than stability into a system
o Produces a cycle where initiating stimulus produces more of the same
THE STRESS RESPONSE
- Hans Selye was first to describe anatomic changes that occurred in rates that were exposed to different
stimuli
- Selye described stress as “a state manifested by a specific syndrome of the body developed in response to
any stimuli that made an intense systemic demand on it”
- He noticed that despite the disease, patients had some signs and symptoms in common (weight loss, ill
facial expression)
o In the rats he was using, the same three changes occurred in response to different environmental
challenges
o To Selye the response (GAS: general adaptive syndrome) to stressors allowed rats to resist the
challenge by using the function of the system best able to respond to it
▪ GAS involves: the alarm stage, the resistance stage, and the exhaustion stage
▪ Alarm stage: stimulation of sympathetic nervous system and HPA axis resulting in
catecholamine and cortisol release
▪ Resistance stage: body selects most effective and economic channel of defense; cortisol
drops because it isn’t needed anymore
▪ Exhaustion stage: if stress overwhelms body’s ability to defend itself, resources are depleted
and systemic damage is a result
o Many ailments were initiated by the body as a result of faulty adaptive reactions to injurious agents
- Stressors: events responsible for initiating the stress response
o Can be endogenous or exogenous
▪ Two factors determine the nature of a stress response: properties of the stressor and
conditioning of the person
▪ Not all stress is detrimental. There’s eustress and distress
• Mild, brief stress can be positive to growth and development
• Severe, uncontrolled stress is disruptive to health
- Conditioning factor: the different responses produced in different people, or the same person at different
times, indicating influence of adaptive capacity of the person
o Can be internal (age, sex) or external (life experiences, diet, level of social support)
o Risk for development of a stress related pathologic process depends on these factors
- Richard Lazarus considered meanings and values to be at the center of human life and to represent the
essence of stress, emotion, and adaptation
o There’s evidence that the HPA axis, the AHS, and SNS are differentially activated depending on type
and intensity of stressor
Neuroendocrine Responses
- Manifestations of stress are influenced by the nervous and endocrine systems
o Neuroendocrine systems integrate signals received along neurosensory pathways and from
circulating mediators that are carried in the bloodstream
Document Summary
The environment in which the body cells live is the local fluid environment, not the external environment that surrounds the organism. A multicellular organism can only survive as long as the internal environment can provide survival needs of individual cells. Walter b cannon proposed homeostasis was achieved though coordinated physiologic processes that oppose change: processes were automatic. Sometimes, with complex stressors, the stress response can"t restore balance, and the physical and psych impact presents itself years later it"s important to identify early negative experiences and treat them. Positive feedback mechanisms interject instability rather than stability into a system. Produces a cycle where initiating stimulus produces more of the same. Hans selye was first to describe anatomic changes that occurred in rates that were exposed to different stimuli. Selye described stress as a state manifested by a specific syndrome of the body developed in response to any stimuli that made an intense systemic demand on it .
