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BMS08 > Control of Physiological Systems > Flashcards

Control of Physiological Systems Flashcards

1
Q

Where are voluntary control mechanisms initiated?

A

Cerebral cortex

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2
Q

What are two purposes of voluntary control mechanisms?

A

Modulation

Reflexes

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3
Q

What systems are involved in involuntary control?

A

ANS

Endocrine system

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4
Q

What are the four important components in the feedback mechanism of a variable?

A

Sensor

Set point

Comparator

Effector(s)

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5
Q

What is a sensor for?

A

Measures current variable/tells you where the variable is now

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6
Q

What is the set point?

A

Where you want the variable to be

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7
Q

What does the comparator do?

A

Compares the current variable (measured by sensor) to the set point

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8
Q

What is an effector for?

A

Alters the variable

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9
Q

How do you calculate the difference signal in a negative feedback system?

A

a - b

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10
Q

What does ‘a’ represent in a feedback system?

A

Negative feedback system

Set point

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11
Q

What does ‘b’ represent in a feedback system?

A

Negative feedback system

Sensor measurement/current variable

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12
Q

What is the difference signal?

A

Difference between set point and current variable

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13
Q

What is the result if the difference variable is negative in a negative feedback system?

A

Effector turns ‘off’ as variable is too great

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14
Q

What is the result if the difference variable is positive in a negative feedback system?

A

Effector turns ‘on’ as variable is too small

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15
Q

What is slack?

A

Range in the variable between which the effector is not turned ‘on/off’

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16
Q

What is the range in which body pH is maintained?

A

7.35 - 7.45

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17
Q

What is the range in which body temperature is maintained?

A

36.1 - 37.2°C

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18
Q

What is the negative response loop?

A

Stimulus -> receptor/sensor -> afferent pathway -> integrating centre -> efferent pathway -> effector/target -> response -> receptor

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19
Q

What turns off the negative response loop?

A

Variable reaching set point

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20
Q

What is the discrimination of the comparator?

A

Difference between the endpoints of a variable

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21
Q

Why can it be dangerous when the set point of a variable changes?

A

Body does not detect harmful changes in the variable which may affect important metabolic processes/structures

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22
Q

What does anaesthesia affect in feedback systems?

A

Effector sensitivity

Sensor sensitivity

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23
Q

What must you be careful when using anaesthesia?

A

Decreased sensitivity of effector = limited response

Decreased sensitivity of sensor = limited detection of variable

Insufficient responses to reestablish homeostasis (= death)

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24
Q

Why are signal delays dangerous in feedback systems?

A

Cannot respond to changes in internal environment sufficiently quickly (more fluctuation)

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25
Q

What is the name given to the fluctuation of the variable about the set point?

A

Hunting oscillation

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26
Q

What is the difference between positive and negative feedback?

A

Negative: response counteracts/removes initial stimulus to shut off response loop

Positive: response builds on stimulus causing further response; external stimulus required to shut off response loop

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27
Q

What is an example of feed-forward control?

A

Gastric secretions on sight and smell of food

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28
Q

When does feed-forward control occur?

A

Anticipatory/prior knowledge situations

29
Q

What type of feedback is childbirth?

A

Positive

30
Q

Describe the feedback loop in childbirth

A

Baby drops lower in uterus to initiate labour

Cervical stretch

Oxytocin release

Uterine contractions

Baby pushed against cervix

Further cervical stretch and cycle repeats until baby is delivered

31
Q

What does ‘X’ represent in a feedback system?

A

Positive feedback

Sensor measurement/current variable

32
Q

What does ‘Y’ represent in a feedback system?

A

Positive feedback

Set point

33
Q

How do you calculate the difference signal in a positive feedback system?

A

X - Y

34
Q

What is the result if X>Y?

A

Effector works harder as variable is greater than set point

Variable further increases so X&raquo_space; Y and cycle continues

35
Q

What are some examples of positive feedback mechanisms?

A

Action potentials

Blood clot formation

Childbirth

Lactation

36
Q

What are two examples of negative feedback mechanisms?

A

Baroreceptor reflex

Osmolarity control

37
Q

How is an action potential an example of positive feedback?

A

When threshold is reached, voltage-gated sodium ion channels open causing more depolarisation

More depolarisation causes the opening of more voltage-gated ion channels

38
Q

Describe the feedback loop of lactation

A

Suckling stimulates nerve endings

Hypothalamus (integrates information)

Posterior pituitary secretes oxytocin causing milk let down

Anterior pituitary secretes prolactin causing milk production

Cycle stops when baby is satiated/stops suckling

39
Q

What are receptors (relating to homeostasis)?

A

Specialised cells/structures that convert various stimuli into electrical signals

40
Q

Where are central receptors found?

A

In/close to the brain

41
Q

What are some examples of central receptors?

A

Eyes, ears, nose, tongue (special sensation)

Chemo, osmo, thermoreceptors

42
Q

Where are peripheral receptors found?

A

Outside the brain

43
Q

What are some examples of peripheral receptors?

A

Baroreceptors

Proprioceptors

Mechanoreceptors

Chemoreceptors

Osmoreceptors

Thermoreceptors

44
Q

What do baroreceptors detect?

A

Pressure

45
Q

What do proprioceptors detect?

A

Position

46
Q

What do mechanoreceptors detect?

A

Pain

Vibration

Touch

47
Q

What do osmoreceptors detect?

A

Osmolarity

48
Q

Where is the regulatory centre for blood pressure?

A

Medulla and brainstem

49
Q

What system is responsible for controlling blood pressure?

A

ANS

50
Q

Describe the feedback mechanism in osmolarity control

A

Dehydration/increased sodium ion intake increases plasma osmolarity

Detected by osmoreceptors in the hypothalamus

Thirst increased so more water ingested

ADH released from pituitary so increased renal water reabsorption

Plasma osmolarity returns to normal

51
Q

How do osmoreceptors detect an increase in plasma osmolarity?

A

Water moves out of cells/osmoreceptors into plasma by osmosis

Cell shrinks

52
Q

Where is the regulatory centre for breathing?

A

Pons

Medulla

(Central pattern generator)

53
Q

What factors (of higher centres) can influence breathing?

A

Temperature

Emotion

54
Q

What part of the central pattern generator is affected by higher centres in breathing?

A

Pons

55
Q

What are the two centres of the pons involved in breathing regulation?

A

Pneumotaxic

Apneustic

56
Q

What are the two groups of the medulla involved in breathing regulation?

A

Ventral respiratory

Dorsal respiratory

57
Q

Which centres of the pons do each of medulla groups interact with?

A

Ventral respiratory group interacts with pneumotaxic centre (two-way)

Dorsal respiratory group interacts with apneustic centre (one-way)

58
Q

What can affect the central pattern generator in breathing regulation?

A

Chemoreceptors

Higher centres

Lung receptors

59
Q

What receptors are present in the lungs involved in breathing control?

A

Stretch

Irritant

Proprioceptors

Juxtapulmonary

60
Q

Which muscles are used in ventilation?

A

Intercostals

Diaphragm

Abdominal

61
Q

What is detected by chemoreceptors in breathing regulation?

A

Blood pCO2 and pO2

62
Q

How does voluntary breathing override normal breathing regulation?

A

Pyramidal tracts

63
Q

What are pyramidal tracts?

A

Upper motor neurons that originate in the cerebral cortex and terminate in the spinal cord or brainstem

64
Q

What is different about the oscillations (around the set point) when there are signal delays?

A

There are gaps

65
Q

What causes Cheyne-Stokes breathing?

A

Poor oxygenation/blood flow causes delay between respiratory muscles and chemoreceptors

66
Q

What is Cheyne-Stokes breathing?

A

Deep and fast breathing followed by apnoea

67
Q

*What causes muscle tremors in Parkinson’s disease?

A

Loss of damping of basal ganglia on reticular formation

Due to lack of dopamine (to stimulate basal ganglia)

68
Q

What does damping do?

A

Reduce, restrict or prevent oscillations

BMS08 (7 decks)

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