Homeostasis Flashcards
What is the definition of homeostasis?
A condition of equilibrium (stability or balance) in the body’s internal environment in response to a stimulus via receptors. This system works to keep the body within the limits to maintain optimum cellular activity.
What does the pH of blood usually stick between?
7.35-7.45
What are the two main systems in the body that contribute to homeostasis?
The nervous and endocrine systems
What are the components of a feedback system?
- Stimulus
- Receptor/sensor
- Control centre
- Effector
What is the stimulus in a feedback system?
Any disruption to a controlled condition
What does the receptor/sensor do in a feedback system?
Monitors the environment and responds to a stimulus
What does the control centre do in a feedback system?
Determines set-point/range to be maintained
Analyses input and determines the appropriate response (output)
What is the role of the effector in a feedback system?
It involves muscles or glands which bring about a response or effect
Define Disease
Any failure of normal physiological function leading to negative symptoms
What factors are necessary for homeostasis?
Effective receptors
Effective brain function
Effective major organs
An adequate blood volume
More specific
- Effective blood vessels
- An effective cardiac pump
- Effective kidney function
What are the role of Baroreceptors?
The baroreceptors send signals to the brain and the signals are interpreted as a rise in blood pressure.
What are the role of chemoreceptors?
The chemoreceptors transmit nervous signals to the respiratory center in the brain to help regulate respiratory activity.
What are the role of Mechanoreceptors?
Mechanoreceptors respond to physical forces in touch, hearing, and pressure
What are the role of Nocireceptors?
Nociceptors are sensory receptors that detect signals from damaged tissue or the threat of damage and respond to chemicals released from the damaged tissue.
What is the role of Photoreceptors?
Photoreceptors are specialized neurons found in the retina that convert light into electrical signals that stimulate physiological processes
What is the role of Thermoreceptors?
Thermoreceptors give the body the ability to detect heat and cold in the environment.
Abnormal vital signs = what?
A change in homeostasis due to an acute situation or chronic disease process
What is negative feedback?
Feedback which prevents sudden severe changes within the body ie, reverses or negates original stimulus. Once equilibrium is achieved this responses is reduced and “Shuts off”
What is positive feedback?
These enhance and amplifies an effector of a change in order for the response to continue at a faster rate. This loop only stops when the stimulus is removed.
Which are more common, positive or negative feedback loops?
Negative
Which feedback loop works to maintain equilibrium? Positive or Negative?
Negative
Which type of diabetes is NO insulin produced?
Type 1 diabetes
How does homeostasis balance BGLs?
A rise in blood glucose levels above a set point causes a receptor to make insulin-secreting cells in the pancreas, insulin is released into the blood allowing for glucose to be absorbed by the blood and removed from the body causing BGL levels to return to normal.
What does the term hyperglycaemia mean?
This is where the level of sugar in your blood is too high. It mainly affects people with diabetes and can be serious if not treated.
Define polyuria.
production of abnormally large volumes of dilute urine.
Define Polydipsia.
Intense thirst despite drinking plenty of fluids.
Why does a pt with COPD have an increased RR?
Because the build up of CO2 in the lungs (hypercapnia) is sensed by neurons in the brain and major blood vessels signalling to the brain and lungs that CO2 levels are above normal, effector signals then cause increased breathing to attempt to exhale more CO2 and restore homeostasis
Why will a pt with COPD have increased WOB?
To try increase the amount of O2 in the lungs
Why will a patient with COPD have a decreased sp02
Because they are hypoxic due to poor gas exchange
Why will a patient with COPD have cyanosis lips and peripheries?
This is caused by decreased local circulation and increased extraction of oxygen in the peripheral tissues related to poor gas exchange in the lungs. (I.e not enough 02 to go around)
Why will a patient in cardiogenic shock have hypotension?
Without oxygen-rich blood reaching the brain and other vital organs, your blood pressure drops
Why will a patient in cardiogenic shock have Tachycardia?
Due to the direct release of noradrenaline to try increase cardiac output (blood flow)
Why will a patient in cardiogenic shock have oliguria?
Because reduced cardiac output leads to a reduced GFR so the kidneys will start retaining fluid
Why will a patient in cardiogenic shock have a low sp02 and be in hypoxia?
Because reduced cardiac output will cause reduced 02 perfusion to vital organs leading to hypoxia hence a low sp02
How does a person with autonomic dysreflexia maintain equilibrium in the body?
They are unable to as ….
Why may a patient with autonomic dysreflexia have hypertension?
Due to the SNS response to a stimuli below the T6
Why may a patient with autonomic dysreflexia have bradycardia?
Because the parasympathetic nervous system (PNS) simulates the vagus nerve (above the T6) to try reduce hypertension
Why may a patient with autonomic dysreflexia have diaphoresis?
Due to severe hypertension that is unable to be managed by the body due to the injury at the spine T6 or above
Why may a patient with autonomic dysreflexia have a pounding headache?
Due to severe hypertension that is unable to be managed by the body due to the injury at the spine T6 or above
How does homeostasis help a patient with short term hypovolaemic shock (decreased blood pressure/volume)?
Sympathetic activation (activation of adrenal glands releasing epinephrine and norepinephrine) causes an increase in cardiac output and peripheral vaso-constriction to increase blood pressure and restore homeostasis
How does homeostasis help a patient with long term hypovolaemic shock (decreased blood pressure/volume)?
The kidneys will produce renin which activates angiotensin 2 increasing thirst which increases blood volume it also is an antidiuretic so holds onto this fluid. The kidneys also produce erythropoietin which increases red blood cell formation increasing blood volume.
Both these processes will hence restore homeostasis.
Signs and symptoms of hypovolaemic shock?
Hypotension rt loss of blood volume
Tachycardia rt heart compensation for reduced CO
Grey pallor rt less blood to skin as blood being directed to heart
Excess haemorrhage (inc bleeding)
Why does a patient with hypovolaemic shock have hypotension?
Due to the loss of blood volume
Why does a patient with hypovolaemic shock have tachycardia?
The heart is compensating for reduced cardiac output
Why does a patient with hypovolaemic shock have a grey pallor?
There is less blood flow to the skin as blood flow is being directed to the core to preserve vital organs
