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Physiology I: Cellular Neuro > Lecture 2: Control Systems > Flashcards

Lecture 2: Control Systems Flashcards

1
Q

Homeostasis definition

A
  • Maintenance of a relatively constant internal environment in the presence of an ever- changing external environment
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2
Q

Homeostasis characteristics

A
  • Dynamic (not an unchanging) condition

- Achieved by physiological processes (homeostatic mechanisms)

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3
Q

Homeostatic mechanisms

A
  • Detect changes in the body and act to counter the changes

- Balance concept is inherent

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4
Q

Homeostasis refers to

A
  • The dynamic mechanisms that detect deviations in physiological variables from their “ideal” values
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5
Q

Homeostasis initiates

A
  • Effector responses that restore these variables to the optimal physiological range
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6
Q

Control systems provide

A
  • Communication between cells, tissues, and organs
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7
Q

Types of control systems

A
  • Nerves only
  • Endocrines only
  • Dual systems
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8
Q

Dual systems

A
  • Provide backup systems
  • Greater plasticity of function or control
  • Some faster, some slower
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9
Q

Chemically addressed systems

A
  • Most control is mediated via chemical messengers
  • Nervous system (via neurotransmitter)
  • Endocrines
  • Local chemicals
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10
Q

Types of chemically addressed systems

A
  • Local chemicals
  • Local hormones
  • Neurotransmitters
  • True hormones
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11
Q

Local chemicals

A
  • Oxygen, carbon dioxide, other metabolites
  • Act on adjacent cells, geared to metabolism
  • Probably play no regulatory function
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12
Q

Local hormones

A
  • Gastrin, secretin, other GI hormones, prostaglandins
  • Paracrines
  • Autocrines
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13
Q

Autocrines

A
  • Hormone or neuronal secretion that may, after being secreted from a cell, act back onto cell of origin
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14
Q

Neurotransmitters

A
  • Released into interstitial fluids (synapse)

- Affect only cells in synaptic contact

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15
Q

True hormones

A
  • Released into circulating body fluids, reaching all cells of the body
  • Endocrines
  • Neurocrines (neurosecretions)
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16
Q

Characteristics of a true hormone

A
  • Chemical substance
  • Secreted directly into the blood by discrete specialized cells
  • In response to a specific stimulus (neural or blood-borne)
  • Amounts vary with the strength of stimulus
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17
Q

True hormones are found

A
  • Only in minute (physiological) concentrations in blood
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18
Q

When carried to their target cells, true hormones

A
  • Exert specific effects that frequently involve the regulation of preexisting cellular reactions
19
Q

Six components of control systems

A
  • Sensor
  • Afferent pathway
  • Error signal generator
  • Integrator
  • Efferent pathway
  • Effector
20
Q

Sensor

A
  • Monitors environment
21
Q

Afferent pathways

A
  • Signals to integrator
22
Q

Integrator

A
  • CPU; center
23
Q

Efferent pathway

A
  • Signals from integrator
24
Q

Effector

A
  • Changes environment
25
Q

Set point

A
  • Ideal value of a control system’s parameter
26
Q

Error signal

A
  • Difference between set point and actual value
27
Q

Gain

A
  • Ratio of correction to error
28
Q

Negative feedback

A
  • Tries to restore homeostasis

- Reduces error signal

29
Q

Positive feedback

A
  • Disturbs homeostasis
  • Increases error signal
  • Often employed to generate the rising phase of a cyclic event (e.g. blood clot, action potential, birth)
  • Self-limiting normally
30
Q

Feedforward

A
  • Disturbs homeostasis
  • Regulatory mechanism for meeting future needs
  • Works with negative feedback controls
31
Q

Components of electrical communication involve

A
  • Nerves alone
32
Q

Components of chemical communication involve

A
  • Endocrines alone
33
Q

Components of electrical and chemical communication combined

A
  • Neuroendocrine
34
Q

Balance depends on

A
  • Rate of gain vs. loss of some property
35
Q

Positive balance

A
  • Net gain

- Rate of gain > rate of loss

36
Q

Negative balance

A
  • Net loss

- Rate of gain < rate of loss

37
Q

Stable balance

A
  • No net change

- Rate of gain = rate of loss

38
Q

Balance incorporates the concepts of

A
  • Steady state
  • Equilibrium
  • Both are states of stable balance
39
Q

Steady state

A
  • Requires energy to maintain it
40
Q

Equilibrium

A
  • Does not require energy to maintain it
41
Q

Nervous system control

A
  • Extrinsic control system
  • Relatively fast system
  • Controls many of one’s quick/immediate responses
42
Q

Endocrine system (extrinsic)

A
  • Controls responses that need to continue for long times or occur more slowly
  • Works with/alongside the nervous system
  • Keeping systems essentially in balance and allowing cells, tissue, organs and the entire body to adjust to changes in the environment
43
Q

Fever involves

A
  • Up-regulation and down-regulation

- Thermostatic resetting

44
Q

Effects of a fever on homeostasis

A
  • Set point for body temp is elevated
  • Release of pyrogen(s) by microorganisms (such as certain bacteria)
  • Pyrogen changes the set point
  • Increased heat production by shivering
  • Heat conservation by cutaneous vasoconstriction

Physiology I: Cellular Neuro (8 decks)

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