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BMS 100 > Homeostasis and Intercellular Signaling > Flashcards

Homeostasis and Intercellular Signaling Flashcards

1
Q

a particular physiologic parameter that is
monitored and maintained within a relatively narrow range at all times

A

Stability

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2
Q

Examples of physiological parameters

A

blood glucose levels, body
temperature, blood pressure, ECF osmolarity

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3
Q

When a process proceeds in the forward and backward direction at the same rate – no net change occurs. What is an example of this?

A

Equilibrium
- a chemical reaction

No energy is expended or regulation occurs

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4
Q

When a process or system exerts energy to maintain a particular state that is optimal for its function. What is an example of this?

A

Dynamic steady state
For example – the Na+/K+ pump moves sodium out of the cell, preventing swelling (maintaining a constant volume)

this steady state is not monitored with clear feedback loops and sensors (that we know of)*

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5
Q

component of homeostasis: give an example of the regulated variable

A

blood glucose level

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6
Q

component of homeostasis: what does an internal disturbance have an impact on?

A

any change in the structure or function of the organisms that results in a change to the magnitude of the regulated variable

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7
Q

component of homeostasis: what does an external disturbance have an impact on?

A

any change in the conditions of the external environment that results in a change to the internal environment

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8
Q

a parameter that is measured in the body with sensors and is kept within a set of limits

A

Regulated variable
Limit = between a low and a high range
i.e. extracellular pH – between 7.35 and 7.45

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9
Q

what is the “thing” that homeostasis is devoted to regulating?

A

Regulated variable

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10
Q

a process that can measure the regulated variable and deliver a signal about that variable

A

a sensor
- can be constant or when happen the regulated variable falls outside of the “normal” range

This can be a cell, or a biochemical reaction, or a channel, or a
tissue – good example is a baroreceptor

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11
Q

Sometimes signals only happen when the regulated variable falls ________ of the “normal” range

A

outside

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12
Q

Usually, signalling is __________, reflecting the overall state of the regulated variable

A

constant

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13
Q

has a controller and an error detector

A

Control centre

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14
Q

“calculates” the difference between the set-point value of the regulated variable and the actual value of the regulated variable and sends an error signal to the controller

A

Error detector

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15
Q

sends output signals to effectors that can change the regulated variable depending on data (error signal) from the error
detector

A

Controller

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16
Q

– the range of values of the regulated variable that the system tries to maintain

A

Setpoint
Very difficult to “find where the set-point exists” in a biological system

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17
Q

what the controller manipulates to “get the job done”. ________ respond to information from the controller and change the value of the regulated variable

A

They will change the regulated variable in such a way that it comes closer to the setpoint

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18
Q

effectors usually change values of the non-regulated variable in order to bring the regulated variable closer to the set point

A
  • Nonregulated variable
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19
Q

example of nonregulated variable: if your pH drops, then your respiratory rate increases in order to “get rid of” excess carbon dioxide. What is the regulated variable and what is the non-regulated variable?

A

Regulated variable = pH
Non-regulated variable = respiratory rat

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20
Q

Are homeostasis and negative feedback
the same?

A

Note that there is no:
- Control centre
- Setpoint
- Error signal
- Regulated variable

  • Therefore, this is not what physiologists consider homeostasis
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21
Q

where are the major baroreceptors? (2)

A
  • carotid arteries
  • arch of the aorta
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22
Q

baroreceptors: once the pressure drops, the message is sent to the brainstem via nerves…then what?

A
  1. Activation of the sympathetic nervous system > release of epinephrine, norepinephrine
  2. Epi and NE > Elevation in HR and constriction of arterioles and increased stroke volume
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23
Q

a proprioceptor that senses muscle stretch

A

Muscle spindle

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24
Q
  • As the muscle is stretched: activates the
    muscle to contract against the stretch
    by stimulating the _____ neuron in the _______ horn
A

motor neuron in the ventral horn
- inhibits the antagonist muscle

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25
Q

relaxes: Stretch caused by hitting the _______ with a reflex hammer

A

tendon

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26
Q

Do homeostatic mechanisms only “turn on” when the regulated variable is outside the setpoint?

A

No, most sensors usually constantly deliver information to the control centre

The controller responds “more intensely” with a larger error signal… but it’s almost always sending input to the effectors at some basal rate

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27
Q

Homeostatic systems tend to _______, rather than be ________

A

overlap, rather than be isolated

28
Q

Effectors can be “turned up” or “turned down” to achieve homeostasis, or different effectors can be called upon to control the regulated variable. What is an example of effectors being turned up down? What is an example of different effectors being called upon?

A

BP regulation – effectors are “turned up” or “turned down”

Glucose regulation – separate metabolic pathways are activated in hyperglycemia vs. hypogycemia

29
Q

are oscillations in the regulated variable typical?

A

yes. Regulated variables fluctuate constantly

30
Q

what can cause larger fluctuations that are unstable and altered set points

A

disease

31
Q

what is an example of a disease state causing an altered set point?

A

hypertension is partially a “set point
error” disease
- the new normal is just high

32
Q

The more vital the parameter, the ______ number of systems that regulate it

A

greater
redundancy is common!

33
Q

The output of a system is fed back in a manner that tends to increase that system’s output. This tends to result in an exponential “increase” in the output until a limited event is reached

A

positive feedback

34
Q

what is an example of a positive feedback loop?

A

Basics of the parturition reflex:

Limiting event – baby is expelled through the birth canal, ending the feedback loop

35
Q

a system where changes in a regulated variable are anticipated, and the controller “pro-actively” activates an effector

A

Feed-forward loop

a change is anticipated and you prepare for it before it happens

36
Q

example of feed-forward loop

A

Example – visualizing performance prior to an athletic event
- Heart rate, stroke volume, BP, and respiratory rate increase

For example – muscle proprioceptors detect an increase in activity
- Signals to the respiratory centre to increase ventilatory rate before any changes in blood gases occur

37
Q

Voluntary control of respiratory rate

A

Cerebral Cortex

38
Q

Regulates respiratory rate based on emotional state, pain, body
temperature set-points -> tells the brainstem to change ventilation

A

Hypothalamus

39
Q

When your muscles and joints move, sends a signal to your brainstem -> your ventilation changes in anticipation of increased MSK oxygen and carbon dioxide exchange needs

A

Proprioceptors

40
Q

Increase ventilation when arterial oxygen drops and carbon dioxide increases. These have a strong influence on ventilation

A

Chemoreceptors
* Peripheral
* Central

41
Q

what are four ways that cells signal to each other?

A

contact
paracrine
endocrine
Nervous (synatpic)

42
Q

Membrane receptors contact the ECM or another cell (ligand) > an intracellular signal in one (or both) cells

A

contact intercellular signalling

43
Q

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”

A

Paracrine intercellular signalling

44
Q

what type of intercellular signalling is important for embryologic development, immune signaling, and for limiting/organizing growth

A

Contact

44
Q

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

A

Endocrine intercellular signalling

44
Q

A neuron “A” sends an electrical signal along an axon to a synapse with cell “B” > release of a neurotransmitter > binding of neurotransmitter to a receptor on cell “B”
> an intracellular response

Cell “B” could be another neuron, a muscle cell (smooth, skeletal, cardiac), or an endocrine cell

A

Nervous (synaptic) intercellular signalling

44
Q

signal cell does:
a target cell:

A

signal cell sends out the signal while a target cell is the cell receiving the singal

45
Q

example of contact intercellular signalling

A

Example – epithelial cells contact the
basement membrane via hemidesmosomes

  • Integrins are part of the
    hemidesmosome complex – when
    they bind the ECM, intracellular
    signals are generated
  • These signals help determine
    polarity (which way is “up”)
46
Q

which types of cell signalling are short-distance signalling

A

contact and paracrine

47
Q

what type of intercellular signalling is Immunological/defence, signals of local
damage, Regulation of growth/cell division/tissue repair and Local regulation of blood flow

A

paracine

48
Q

Everyday (every second) example of paracine signalling

A
  • Metabolically active tissue releases
    metabolites (H+, CO2, K+) that cause
    local vascular endothelial cells to relax >
  • Vasodilation and improved blood flow
49
Q

what type of cell signalling is long-distance

A

Endocrine

50
Q

What is the mechanism for endocrine intercellular signalling

A

Organ secretes a messenger into the bloodstream>
Messenger is widely distributed throughout the body >
Cells with receptors for the messenger respond

51
Q

The _____________ controls the endocrine secretions of the pituitary gland. Pituitary secretions act on another target gland or
organ.

A

hypothalamus

hypothalamus to pituitary to another thing

52
Q

How does “other” endocrine glands work?

A

These glands are not under hypothalamic or pituitary control

Usually they directly sense a stimulus (they are the sensor and the control centre) and secrete a hormone in response to that stimulus

53
Q

what are examples of “other” endocrine glands?

A
  • Pancreas and GI tract
  • Parathyroid glands
  • Adipose tissue
54
Q

Which of these glands are under hypothalamic control?

A

The hypothalamus ultimately affects the functions of the pituitary gland, thyroid gland, adrenal glands, kidneys, musculoskeletal system, and reproductive organs (testes, ovaries)

55
Q

The hypothalamus sits just under the thalamus and is connected to the pituitary gland via a

A

vascular stalk

56
Q

The pituitary gland sits within the

A

sella turcica
middle cranial fossa within your sphenoid bone

57
Q

General model of the hypothalamic-pituitary system

A

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

58
Q

what are the major hormones secreted by the posterior pituitary? Where do these act?

A

ADH and oxytocin

Both of these act directly on target tissues, not on other glands

59
Q

ADH (anti-diuretic hormone) controls _______ balance in the body

A

water
One of the two hormones secreted by the posterior pituitary

Other is oxytocin (hormone that controls the positive feedback loop of childbirth)

60
Q

ADH secretion is controlled by the osmolarity of the blood – when the blood is ______ concentrated (i.e. ______ water), then ADH is secreted

A

more concentrated, less water

When ADH is secreted, then more water is “recovered” by the kidneys and kept in the bloodstream

When ADH decreases, more water is lost in the urine

61
Q

Blood osmolarity is detected by ___________ in the hypothalamus

A

osmoreceptors

62
Q
A

BMS 100 (37 decks)

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