Concept of Homostasis Flashcards
What is homeostasis?
The ability to maintain a relatively stable internal environment.
Explain how homeostasis is maintenance of a state of dynamic constancy.
IT means that conditions are stabilized above and below a physiological set point.
What is the ideal normal value of a variable ?
Set point
What are the three interdependent components of control mechanisms?`
Receptor
Control Center
Effector
What is the function of the receptor component of control mechanisms?
Moniter the environment and responds to stimuli
What is the function of the Control center component of control mechanisms?
Determines the set point at which the variable is maintained
What is the function of the effector component of control mechanisms?
Provides the means to respond to the stimulus
What is the pathway of information going into a control center? Leaving the control center?
afferent is incoming
efferent is outgoing.
Explain the process of a Generic negative feedback pathway.
- A deviation is detected by the receptor
- Control center receives information, processes, and initiates effector
- Effector caused value to return to set value
What does is mean when an organ has intrinsic control ?
homeostasis regulation is built into the organ
What does is mean when an organ has extrinsic control ?
homeostasis regulation comes from outside organ
Give an example of extrinsic control
Body temperature (sweating and shivering)
Blood glucose
(hormones)
Explain temperature regulation in regard to an increase in body temp.
- increase in body temp is detected by receptors in the hypothalamus and skin
- The ANTERIOR hypothalamus responds to the receptor and activates heat loss mechanisms.
- A. increased sweating increases evaporative heat loss
3 B. dilation of skin blood vessels increases heat loss from the skin - C. Behavior modification such as taking off jacket or moving to cooler environment
- Body temp returns to set value
Explain temperature regulation in regard to an decrease in body temp.
- decrease in body temp is detected by receptors in the hypothalamus and skin
- The POSTERIOR hypothalamus responds to the receptor and activates heat-generating and heat conserving mechanisms.
- A. Constrictions of skin blood vessels decreases heat loss from the skin
3 B. Shivering increases heat production - C. Behavior modification such as putting on jacket or moving to warmer environment
- Body temp returns to set value
What is the immediate effects of acclimatization to high altitude?
- Hyperventilation resulting in increase proportion of fresh air to alveoli
- Better oxygen loading in lungs
What is the effects of acclimatization to high altitude after a couple days?
Increase oxygen unloading in tissues
What is the effects of acclimatization to high altitude after a couple weeks?
Increase oxygen content of blood
Give four examples of homeostasis regulation in the cardiovascular system.
Blood pressure
Baroreceptor reflex
Volume regulation
Blood osmolality
What is the structure that serves as the command center for blood pressure homeostasis?
Medulla Oblongata
Explain the Blood pressure negative feedback for elevated blood pressure
- increase in blood pressure is detected by receptors in blood vessels
- The control center in the brain that regulates heart rate responds
- Heart rate decreases
- decrease in blood pressure cause decrease in blood pressure
Explain the Blood pressure negative feedback for Decreased blood pressure
- Decrease in blood pressure is detected by receptors in blood vessels
- The control center in the brain that regulates heart rate responds
- Heart rate increases
- increase in blood pressure cause increase in blood pressure
Where are the baroreceptors located?
Aortic arch and carotid sinuses
What does the baroreceptors detect that relates to blood pressure?
Wall Stretching
The baroreceptors send the action potential generated by wall stretching to what locations?
vasomotor and cardiac control centers in medulla
The baroreceptor reflex is mos sensitive to ____ and sudden changes in _____
decrease
Blood pressure
Explain the homeostasis regulation in response to a increase in blood pressure
- Increase in BP is detected by baroreceptor reflex
- A. the cardioregularory center increases parasympathetic stimulation of the heart and decrease sympathetic stimulation of the heart
- B. The vasomotor center decreases sympathetic stimulation of the blood vessel
- A. Decrease heart rate and stroke volume result from the changed ANS stimulation the heart
- B. Vasodilation of blood vessels, caused by decreased sympathetic stimulation, decrease peripheral resistance.
- a decrease in BP is caused by a decrease in HR, stroke volume and peripheral resistance.
Explain the homeostasis regulation in response to a decrease in blood pressure via the baroreceptor reflex
- Decrease blood pressure is detected.
- Baroreceptor reflex detects decrease via baroreceptors
- A. baroreceptor reflex makes the cardioregularory center decreases parasympathetic and increases sympathetic stimulation of the heart.
3.B. Baroreptor reflex cause the vasomotor center to increase sympathetic stimulation of blood vessels - A. increase HR and stroke volume from ANS stimulation of the heart
4 B. vasoconstriction of blood vessels in skin and viscera increase peripheral resistance - Increase in blood pressure due to increase HR, stroke volume, and Peripheral resistance
Explain the homeostasis regulation in response to a decrease in blood pressure via the adrenal medullary mechanism.
- Decrease blood pressure is detected.
- Adrenal medullary detects decrease in BP via baroreceptors
- The adrenal medulla increase secretion epinephrine and norepinephrine due to increased sympathetic stimulation from the baroreceptor reflex
- A increased HR and stroke volume
- B. vasoconstriction of blood vessels in skin and viscera increase peripheral resistance
- Increase in blood pressure due to increase HR, stroke volume, and Peripheral resistance
What system produces Angiotensin 2 ? What cause production?
The Renin-angiotension-Aldosterone system
Salt deficiency and low blood volume/pressure
What are the effects of Angiotensin 2?
Vasoconstriction Aldosterone secrection ( Na retention) thirst
Explain the The Renin-angiotension-Aldosterone system process.
- Decrease in BP
- Renin is released by kidney and reacts the angiotensinogen ( released by liver) to create angiotensin 1.
- Angiotensin 1 is converted to angiotensin 2 by enzyme in lungs
- A. angiotensin 2 causes vasoconstriction which increases BP.
- B. Angiotensin 2 cause aldosterone to be secreted from adrenal cortex.
- Aldosterone cause increased water reabsorption and decreased urine volume which increase BP / volume.
Where is renin secreted from?
Juxtaglomerular apparatus in kidneys
What causes the release in Atrial Natriuretic Peptide?
Expanded blood volume detected by stretch receptors in right atrium
What is the function of Atrial Natriuretic Peptide (ANP)?
inhibit aldosterone which promotes salt and water excretion to lower blood volume and promotes vasodilation
Explain the vasopressin (ADH) mechanism process.
- A. Osmoreceptors detect increase osmotic pressure.
- B. Baroreceptors( found in aortic arch and carotid sinus) detect decreased BP
- Information is relayed to hypothalamus neuron which stimulates the secretion of Anti-diuretic hormone from the posterior pituitary.
- ADH causes vasoconstriction and increased reabsorption of water in kidneys which results in increase BP and blood volume
What is the range of blood osmolality ?
300mOsm
Dehaydration causes Osmoreceptors in the hypothalamus to stimulate what?
secretion of ADH
What are two biological effects of ADH?
increases permeability of distal tubules and collecting ducts to water
increase thirst
Explain the hormonal regulation of blood osmolality in regards to an increase in blood osmolality
- increase in blood osmolality is detected by Osmoreceptors in hypothalamus
- Osmoreceptors stimulate ADH secretion from the posterior pituitary.
- Increase thirst and permeability of distal tubules and ducts
- decrease in blood osmolality from increase movement of water into blood
Explain the hormonal regulation of blood osmolality in regards to an decrease in blood osmolality
- decrease in blood osmolality is detected by Osmoreceptors in hypothalamus
- Osmoreceptors inhibit ADH secretion from the posterior pituitary.
- decrease thirst and permeability of distal tubules and ducts
- increase in blood osmolality from decrease movement of water into blood
Which mechanisms regulate ECF volume?
- Neural
- Renin-angiotensin-aldosterone system
- Atrial natriuretic hormone
- Antidiuretic hormone
Increase in ECF results in what biological changes?
- decreased aldosterone secretion
- increased ANH secretion
- decreased ADH secretion
- Decreased sympathetic stimulation
decrease in ECF results in what biological changes?
- increased aldosterone secretion
- decreased ANH secretion
- increased ADH secretion
- increased sympathetic stimulation
Explain the hormonal regulation of increase blood volume by the ADH mechanism
- Increase in blood volume is detected by baroreceptors
- ADH secretion is inhibited
- Vasodilation and decrease reabsorption results in lowered BP
Stress induces a non-specific response called a _______ which causes ACTH and cortisol release
General adaptation syndrome (GAS)
Explain the hormonal regulation of increase blood volume by the ANH mechanism
- Increase in blood volume is detected by atrial cardiac muscle
- ANH secretion is increased and aldosterone is inhibited
- Vasodilation and decrease reabsorption results in lowered BP
Explain the negative feedback hormonal control of increased blood glucose
- Eating cause increase blood glucose
- The pancreatic islets increase insulin
- insulin cause increased cellular uptake of glucose
- A. Glucose is converted to glycogen in liver and skeletal muscle.
- B. glucose is converted to triglyceride in adipose
- decreased BG
Explain the negative feedback hormonal control of decreased blood glucose
- Fasting causes decreased blood glucose
- Pancreatic islets inhibit insulin secretion and increase glucagon secretion.
- Cellular uptake of glucose is decreased and glucose is secreted into blood by liver
- increase BG
What stimulates the release of parathyroid hormone?
Decreased blood calcium
What does parathyroid hormone work on?
blood, kidney, and intestines
What is the major storage site for calcium in the body?>
bone
What builds new bone?
Osteoblast
What cycle breaks down bone?
osteoclasts
Explain the homeostasis process that results from decreased blood calcium.
- Decreased Ca causes the parathyroid to release parathyroid hormone
- The hormone cause the kidneys to reabsorb Ca, dissolve CaPO4 crystals in bone and increase absorption of Ca by intestines
- A. increased blood Ca
- B. decreased urinary excretion of Ca
What is the hypothalamic-pituitary-gonad axis control system?
It is a feedback control involves a short feedback loop in which the retrograde flow of blood and hormones from the anterior pituitary to the hypothalamus inhibits secretion of releasing hormones.
The hypothalamic-pituitary-gonad axis control system involves ______ feedback to target gland ______.
negative
horomones
Durinf the menstrual cycle, estrogen stimulates a “__ _____” by _____ feedback.
LH surge
Positive
The hypothalamus controls release of ___ and __ from anterior pituitary with ____
LH and FSH
GnRH
What is the function of LH and FSH ?
stimulate production of sperm and eggs, and gonadal sex steroids; and maintain size of gonads
Sex steroids provide ______ ______ on hypothalamus and Ant Pit
negative feedback
Testosteron. inhibits __ and ____ secretion but not ___.
LH and GnRH
FSH
Gonads also secrete hormone ____ ( from the _____ cells) which negatively feeds back on FSH secretion.
inhibin (sertoli cells)
Explain the interaction between the hypothalamus, anterior pituitary, and bonads
- The hypothalamus secretes GnRH
- GnRH stimulates the anterior pituitary to release FSH and LH (gonadotropins)
- The gonads (testes) have two negative feedbacks. The seminiferous tubules release inhibin which inhibits FSH secretions. The interstitial (leydig cells) releases testosterone that inhibits LH secretion as well as GnRH secretion.
Explain the follicular ( proliferative) phase
Its the phase before ovulation in which estrogen is released from the ovary causing the secretion of GnRH and LH. Its is the positive feedback aspect of the menstrual cycle.
Explain the Luteal (secretory) phase
Its the phase after ovulation in which progesterone is released from the ovary inhibiting the secretion of GnRH and LH. Its is the negative feedback aspect of the menstrual cycle.
What is a vascular spasm ?
vasoconstriction of damaged blood vessels
What kind of feedback is blood clotting?
Positive
Name some examples of positive feedbacks homeostasis.
Blood clot production Follicular phase of menstruation Oxytocin secretion during labor second messenger amplification inflammatory response antibody formation conductance changes during action potential
