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ANSC 311 - Metabolic Physiology > Midterm 3 - Lecture 20 > Flashcards

Midterm 3 - Lecture 20 Flashcards

1
Q

What are the inputs of heat exchange?

A
  1. metabolism - 50% efficiency
  2. work (muscles) - 25% efficiency
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2
Q

What are the outputs of heat exchange?

A
  1. conduction (contact)
  2. convection (air)
  3. radiation (skin)
  4. evaporation (sweat/panting)
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3
Q

What is the shivering pathway?

A

Inputs
- central thermoreceptors = hypothalamus, CNS, abdominal organs
- peripheral thermoreceptors = skin

Integration
- hypothalamus

Effectors
- motor neurons
- skeletal muscle

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4
Q

What is shivering?

A

uncoordinated contraction of skeletal muscles
- little work, a lot of heat!

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5
Q

What is non-shivering thermogenesis?

A

*remember, shivering is only 25% efficient

Use brown adipose tissue for heat production
- uncoupling generates heat = rather than generating ATP, we allow H+ to come in
- burn fuel instead of making ATP bc metabolism is 50% efficient

Mediated by
- thyroid hormones
- SNS

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6
Q

What is countercurrent heat exchange?

A
  • veins exchange (take) heat from arterial blood
  • heating up venous blood which is returned to the heart
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7
Q

Thermoneutral zone

A

the temperature range in which an animal does not have to use any energy to conserve or dissipate heat

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8
Q

What happens if an animal is below ambient temp?

A
  • increase metabolic rate
  • shivering
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9
Q

What happens if an animal is above ambient temp?

A
  • sweating and respiration
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10
Q

What is sweating? What is it stimulated by?

A
  • heat loss by evaporation
  • stimulated by sympathetic nervous system
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11
Q

Does environmental temperature alter metabolism?

A

Yes!

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12
Q

What happens when blood is warmer than hypothalamic set point?

A
  1. activates heat-loss center in hypothalamus
  2. a. skin blood vessels dilate; capillaries become flushed w/ warm blood; heat radiates from skin
    b. sweat glands activated: secrete perspiration which is vaporized by body heat helping to cool body
  3. body temperature decreases; blood temp declines and hypothalamus heat-loss center shuts off
  4. body returns to normal temp
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13
Q

What happens when blood is cooler than hypothalamic set point?

A
  1. activates heat-promoting center in hypothalamus
  2. a. skin blood vessels constrict; blood is diverted from skin capillaries and withdrawn to deeper tissues; minimizes overall heat loss from skin surface
    b. skeletal muscles activated when more heat must be generated = shivering
  3. body temp increases; blood temp rises, and hypothalamus heat promoting center shuts off
  4. body returns to homeostasis
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14
Q

What are the body’s temperature receptors?

A
  1. CNS thermoreceptors (core temp)
  2. Arterial blood (most important)
  3. Peripheral thermoreceptors (skin)
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15
Q

Why is a cow at risk of acidosis and reduced milk yield during high ambient temperature?

A
  • high temp = panting, reduced feed intake, decreased rumination, drooling
  • panting = CO2 expelling = reduced saliva buffering power
  • drooling = less saliva to the rumen = decreased buffer effect
  • reduced buffering effect = reduced rumen pH
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16
Q

What is happen physiologically to induce a fever?

A
  1. infection/inflammation
  2. macrophages release endogenous pyrogen
  3. pyrogens induce the release of prostaglandins
  4. increase hypothermic set point
  5. initiation of cold response (activates thermogenesis)
  6. increase heat production
  7. increase body temp to new set point
17
Q

When does a fever “break”?

A
  • when prostaglandins stopped being produced
  • set point is lowered and current temp is too high = induces sweating
18
Q

How does aspirin help with a fever?

A
  • blocks prostaglandin synthesis = prevents hypothermic set point from increasing
19
Q

Circadian Rhythm

A

a daily rhythmic activity cycle, based on 24-hr intervals
- feed forward control = initiates changes in physiological systems rather than correcting them

20
Q

What is responsible for circadian rhythms in mammals?

A
  • photosensitive cells in the retina detect light and directly signal the suprachiasmatic nucleus
  • for other animals, the pineal eye has photosensitive cells
  • regulates rhythms based on photoperiod
21
Q

What is meant by the circadian rhythm being endogenous?

A

does not require sensory information for timing

22
Q

What sort of activities are regulated by circadian rhythms?

A

Circannual rhythms (~365 days) = migration, repro

Photoperiod rhythms (24h) = sleep/wake cycle, metabolism/body temp, locomotor activity, pheromone release

23
Q

What is a photoperiod?

A

The amount of light exposure in a 24 hr period
- earth receives an average of 12 light, 12 dark
- short day = 6L:18D
- long day = 18L:6D

24
Q

What is the response to a photoperiod?

A

Light: inhibits the rate-limiting enzyme for the synthesis of melatonin

Dark: ‘biological night’, pineal gland secretes melatonin

25
Q

Melatonin

A
  • high in response to darkness
  • short day increases duration of melatonin secretion
  • regulates circadian clock
26
Q

What hormone regulates the circadian clock?

A

melatonin

27
Q

Prolactin

A
  • secreted from the pars tuberalis of the pit gland
  • secretion increased in long day and decreased in short day
  • affects energy metabolism, gonadal activity, pregnancy, and lactation
28
Q

During lactation, what type of day increases milk yield?

A

LD increases milk yield

29
Q

During a dry period, what type of day increases milk yield?

A

SD increases milk yield

30
Q

A long day increases milk yield and what hormone?

A
  • increases IGF-1 which mediates GH response
31
Q

What 2 hormones mediate the response to photoperiod?

A

melatonin and prolactin

32
Q

How can photoperiod affect salmon?

A
  • can be used to influence juvenile growth
33
Q

How can photoperiod affect goats?

A
  • long day photoperiod increases milk production
34
Q

How can photoperiod affect birds?

A
  • drives seasonal events like molting, breeding and song production
35
Q

How can photoperiod affect broiler breeders?

A
  • used to initiate/synch egg production
36
Q

How can photoperiod affect pigs?

A
  • long days may enhance sow and litter performance

ANSC 311 - Metabolic Physiology (17 decks)

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