Physiology Concepts IV Flashcards
1
Q
What did Claude Bernard say in 1865?
A
stability of internal environment is crucial for life
2
Q
What did Charles Richet say in 1990?
A
the living system is stable, it must be in order not to be destroyed, dissolved, or disintegrated by colossal forces, often adverse, which surround it
3
Q
T/F: The living system is stable because it is not modifiable
A
False, living system is stable because it is modifiable
4
Q
When and who coined the word “homeostasis”?
A
1963, walter cannon
5
Q
What is the current definition of homeostasis?
A
self-regulating process by which biological systems maintain stability while adjusting to changing external conditions
6
Q
What is stability?
A
a particular physiologic parameter that is monitored and maintained within a relatively narrow range at all times
7
Q
Define equilibrium.
A
When a process proceeds in the forwards & backwards direction at the same rate - no net change occurs
8
Q
Is energy expended during equilibrium?
A
No
9
Q
Does regulation occur in equilibrium?
A
no
10
Q
Define dynamic steady state
A
when a process or system exerts energy to maintain a particular state
11
Q
Is a dynamic steady state at equilibrium?
A
No
12
Q
Give an example of a dynamic steady state?
A
Na+/K+ pump
13
Q
T/F: Dynamic steady state is not monitored w/ clear feedback loops & sensors
A
True
14
Q
What are the components of homeostasis?
A
sensor, regulated variables, error detector, controlled, effevctors
15
Q
What are regulated variables? Give examples.
A
Parameter that is measured in the body w/ sensors & is kept within a set of limits ex., blood glucose, blood pressure etc.
16
Q
What is the “thing” homeostasis is devoted to regulating?
A
regulated variable
17
Q
What is a sensor?
A
Process that can measure the regulated variable & deliver a signal about that variable
18
Q
When do sensors signal?
A
- signal only happens when regulated variable falls outside normal range
- signalling is constant reflecting overall state of regulated variable
19
Q
Give an example of a sensor?
A
baroreceptor
20
Q
What are the two parts of a control centre? Define them.
A
Error detector: “calculates” difference b/w set-point value of regulated variable & actual value of regulated variable & sends error signal to the controller
controller: sends output signals to effectors that can change the regulated variable depending on data (error signal) from the rror detector
21
Q
What is a set point?
A
range of values of the regulated variable that the system tries to maintain
22
Q
What does the controller manipulate, why?
A
effector - to get the “job done”
23
Q
What do effectors do?
A
respond to information from the controller & change the value of the regulated variable to closer to the set point
24
Q
What do effectors change the value of and why?
A
nonregulated variable in order to bring the regulated variable closer o the set point
25
Which is the regulated variable & nonregulated variable: if pH drops, then respiratory rate increases in order to "get rid of" excess CO2
regulated: pH
nonregulated: respiratory rate
26
Are homeostasis & negative feedback the same?
- homeostasis uses negative feedback loops but not all negative feedback loops are homeostatic
- negative feedback does not have the components of homeostasis
27
Define negative feedback.
output of a system is fed back in a manner that tends to reduce the fluctuations in the output (oscillating high and low amounts of product)
28
Where are major baroreceptors?
carotid arteries
arch of aorta
29
What happens when your blood pressure drops?
pressure drops --> message sent to brainstem via nerves -->
- (1) activation of sympathetic nervous system --> release of epinephrine, norepinephrine
- (2) Epi & NE --> elevation in HR & constriction of arterioles & increased stroke volume
30
Give examples of the components of homeostasis with reference to blood pressure dropping.
sensor: baroreceptors
error detector & controller: brainstem
control signals: Epi & NE
effector: heart & arteries
31
What is a muscle spindle?
proprioceptor that senses muscle strectch
32
What happens as a muscle is stretched?
muscle spindle activates the muscle to contract against the stretch by stimulating the motor neuron in the ventral horn & inhibits the antagonist muscle
33
Is stretch reflex a negative feedback loop or homeostatic system?
negative feedback loop
34
T/F: homeostatic mechanisms only "turn on" when the regulated variable is outside the stepoint
False, most sensors usually constantly deliver info to control centre, may respond "more intensely" but is always sending info
35
What is the regulated variable in the body's ECF?
potassium is the regulated variable
36
What is the normal range, sensor, control centre, effector, and effector response for the regulated variable **arterial oxygen**?
normal range: 80-100 mmHg
sensor: chemosensors (carotid, aortic)
control centre: brain stem
effector: respiratory muscles
effector response: altered respiratory rate
37
What is the normal range, sensor, control centre, effector, and effector response for the regulated variable arterial CO2?
normal range: 35-45 mmHg
sensor: chemosensors (carotid, aortic)
control centre: brain stem
effector: respiratory muscles
effector response: altered respiratory rate
38
What is the normal range, sensor, control centre, effector, and effector response for the regulated variable [K+]?
normal range: 3.5-5.0 mmol
sensor: chemosensors (adrenal)
control centre: adrenal
effector: kidneys, many other tissues
effector response: altered K+ reabsorption, secretion
39
What is the normal range, sensor, control centre, effector, and effector response for the regulated variable **[Ca2+]**?
normal range: 2.2-2.6 mmol/L
sensor: chemosensors (parathyroid)
control centre: parathyroid
effector: kidneys, bone, intestine
effector response: altered calcium reabsorption, secretion
40
What is the normal range, sensor, control centre, effector, and effector response for the regulated variable pH?
normal range: 7.35-7.45
sensor: chemosensors (brainstem, carotid, aortic)
control centre: brainstem
effector: respiratory muscles
effector response: altered respiratory rate
41
What is the normal range, sensor, control centre, effector, and effector response for the regulated variable blood glucose?
normal range: 4-8 mmol
sensor: chemosensors (pancreas)
control centre: pancreas
effector: liver, skeletal muscle, fat
effector response: altered glucose metabolism
42
What is the normal range, sensor, control centre, effector, and effector response for the regulated variable osmolarity?
normal range: 280-296 mOsm
sensor: chemosensors (hypothalamus)
control centre: hypothalamus
effector: kidneys
effector response: sodium & water reabsorption
43
What is the normal range, sensor, control centre, effector, and effector response for the regulated variable core body temperature?
normal range: 35.5-37.5 clesius
sensor: thermosensor (hypothalamus, skin)
control centre: hypothalamus
effector: blood vessels, sweat glands, skeletal muscle
effector response: shivering, sweating, distribution of blood
44
What is the normal range, sensor, control centre, effector, and effector response for the regulated variable mean arterial pressure?
normal range: 85-100 mmHg
sensor: baroreceptor (aortic, carotid)
control centre: brain stem
effector: heart & blood pressure
effector response: change in HR, SV, vascular tone
45
What is the normal range, sensor, control centre, effector, and effector response for the regulated variable blood volume?
normal range: 5 L
sensor: heart, kidneys
control centre: medulla
effector: heart, kidneys
effector response: change in HR, SV, vascular tone, & fluid/salt retention
46
T/F: All homeostatic systems involve regulated parameters of some component of ECF
True
47
T/F: systems tend to be isolated, rather than overlap
False, tend to overlap, rather than be isolated
48
What are two ways effectors can accumulate to produce a response?
- "turned up" or "turned down" (pressure)
- called upon to control regulated variable (blood glucose)
49
What do disease states cause to oscillations?
cause large fluctuations that are unstable
50
Explain how hypertension is a "set point disease"
Because the new high blood pressure is just "normal" to the body
51
Define positive feedback.
- output of a system is fed back in a manner that tends to increase that system's output
- increases output till a limiting event is reached
52
What is an example of positive feedback?
parturition (childbirth) positive feedback loop
- limiting event: baby is expelled through birth canal, ending feedback loop
53
Explain the basics of parturition reflex.
babys head presses on & thins the cervix --> cervical thinning & stretch is detected by mechanoceptors & transmitted to the brain -->the hypothalamus release oxytocin in response --> oxytocin causes uterine contraction, forcing baby against cervix
54
What are feed-forward loops?
system where changes in regulated variable are anticipated & the controller "pro-actively" activates an effector
55
What are two examples of feed-forward loop?
1. visualizing performance prior to an athletic event (HR, SV, BP, respiratory rate increase)
2. muscle proprioceptors detect an increase in activity (signals to the respiratory centre to increase ventilatory rate before any changes in blood gases occur)
56
What is the cerebral cortex's job in regulation of ventilation?
voluntary control of respiratory rate
57
What is the hypothalamus' job in regulation of ventilation?
regulates respiratory rate based on emotional state, pain, body temp. set-points --> tells brainstem to change ventilation
58
What is the proprioceptors's job in regulation of ventilation?
when muscles & joints move, send a signal to your brainstem --> ventilation changes in anticipation of increased MSK O2 & CO2 exchange needs
59
What is the chemoreceptors's job in regulation of ventilation? What are two types?
Peripheral, central
- increase ventilation when arterial oxygen drops in CO2 increases --> Strong influence on ventilation
60
What is the strongest influence on ventilation?
drop in O2, increase in CO2
61
What is the bodies strategy for maintaining cell homeostasis?
keep internal environment constant so cells aren't in a "hostile environment" that's difficult to regulate
62
What are ways cells signal to each other?
contact, paracrine, endocrine, nervous
63
Define contact signaling.
membrane receptors contact the ECM or another cell (ligand) --> an intracellular signal in one (or both) cells
64
Define paracrine signaling.
Cell "A" produces a soluble messenger which diffuses to a cell "B" --> binding to a membrane receptor on cell "B" --> an intracellular signal in cell "B"
65
Define endocrine signalling.
cells in endocrine organs release a chemical messenger into the bloodstream --> circulation of the messenger (hormone) --> an intracellular response in any cell that has a receptor for that hormone
66
Define nervous signaling.
a neuron "A" send an electrical signal along an axon to a synapse with cell "B" --> release a neurotransmitter --> binding of neurotransmitter to a receptor on cell "B" --> an intracellular response (cell "B" can be a neuron, muscle, or endocrine cell)
67
What is a signalling cell?
the cell that is sending out the signal to another cell
68
What is a target cell?
the cell that you want the signal sent to
69
Give examples of short-distance signalling.
contact & paracrine
70
What is contact signalling important for?
embryologic development, immune signalling, & for limiting/organizing growth
71
Give an example of contact signaling.
epithelial cells contact basement membrane via hemidesmosomes
- integrins are part of hemidesmosome & when they bind to ECM, intracellular signals are generated (determine polarity)
72
What is paracrine signalling used for?
immunological/defence, signals of local damage, regulation of growth/cell division/tissue repair, local regulation of blood flow
73
Give an example of paracrine signaling.
metabolically active tissue releases metabolites (H+, CO2, K+) that cause local vascular endothelial cells to relax --> vasodilation & improved blood flow
74
Give examples of long-distance signalling.
endocrine, neuro (sometimes)
75
What are the two major pathways for endocrine signalling?
hypothalamic-pituitary system, "other" endocrine glands
76
Define the hypothalamic-pituitary system.
hypothalamus controls endocrine secretion of pituitary gland --> pituitary secretion acts on target gland or organ
77
How do "other" endocrine glands work in endocrine signalling?
they directly sense a stimulus (they are sensor & control centre) & secrete a hormone in response to that stimulus
78
What are example of "other" endocrine gland signalling?
pancreas & GI tract, parathyroid glands, adipose tissue
79
Which organs in endocrine system are under hypothalamic contro?
thyroid, ovaries, testes, adrenal glands
80
Where is the hypothalamus, what is it connected to?
sits under thalamus, connected to pituitary gland via a vascular stalk
81
Where does the pituitary gland sit?
sella turcica in sphenoid bone
82
What is the general model of hypothalamic-pituitary system?
hypothalamic signal --> stimulates pituitary cells --> pituitary cells release a hormone --> hormone acts on another gland (usually endocrine) --> “target” gland secretes larger quantities of a hormone --> general systemic response
83
Describe the hypothalamic-pituitary system with reference to the anterior pituitary.
hypothalamus secretes releasing or inhibiting hormones into 1st set of capillaries --> these travel down to the anterior pituitary & module hormone secretion from those cells --> anterior pituitary hormones control a number of other endocrine glands (thyroid, adrenal, gonads, liver)
84
Describe the hypothalamic-pituitary system w/ reference to the posterior pituitary.
hypothalamic neurons project to posterior aspect of pituitary --> axons of these neurons release hormones into the capillaries in the posterior pituitary (ADH & oxytocin, both of these act directly on target tissues, not on other glands)
84
What is the difference between the anterior and posterior pituitary of the hypothalamic-pituitary system?
the posterior pituitary releases hormones that target tissues, the anterior pituitary releases hormones that target glands
84
What is secreted by the posterior pituitary?
ADH & oxytocin
85
What does ADH control?
water balance in the balance
86
What does oxytocin control?
positive feedback loop of childbirth
87
What controls ADH secretion?
osmolarity of the blood
88
When the blood is more concentrated, what happens to ADH? Why?
it is secreted - more water is "recovered" by kidneys & kept in blood stream
89
What happens when ADH decreases?
more water is lost in urine
90
What detects blood osmolarity?
osmoreceptors in the hypothalamus
91
What are the sensor, error detector & controller, control signals, & effector in ADH signalling and fluid homeostasis?
sensor: osmoreceptors
error detector & controller: hypothalamus
control signals: ADH
effector: kidneys
92
What is thyroid hormone release regulated by?
hypothalamus in response to cardiovascular parameter and "metabolic" parameters (ex., body temp.)
93
If thyroid hormones are low, what will happen in the body?
hypothalamus will release TRH --> anterior pituitary will release TSH --> thyroid gland will then release more thyroid hormones --> thyroid hormones increase
94
If you have sufficient thyroid hormones what occurs in the body?
they will negatively feedback to the hypothalamus & anterior pituitary
95
If you have sufficient TSH in the body what occurs?
TSH will negatively feedback to hypothalamus
96
