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BPK 432 > Lecture 5 > Flashcards

Lecture 5 Flashcards

1
Q

To explain the different types of thermal panting and their components.

A

Thermal panting is increased respiratory evaporative heat loss (REHL) due to increased respiratory minute volume.

There are 2 types of thermal panting: 1st phase panting aka thermal TACHYPNEA, and 2nd phase panting aka thermal HYPERPNEA.

1st phase panting aka thermal TACHYPNEA:

  • A rapid respiratory frequency accompanied by an increase in respiratory minute volume and, commonly, a decrease in tidal volume, in response to a thermoregulatory need to dissipate heat.
  • Synonym: thermal polypnea.
  • PETCO2/PaCo2 is maintained during this response

2nd phase panting aka thermal HYPERPNEA:
- An increase in tidal volume associated with an increase in alveolar ventilation occurring during severe heat stress which has caused a large rise in Tcore. In animals capable of thermal panting, the phase of thermal hyperpnea with its slower, deeper breathing is also named second phase panting, since it is usually preceded by a phase of typical panting
- PETCO2/PaCo2 is
decreased during this response.

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2
Q

To explain thermal hyperpnea and how hyperthermia influences pulmonary ventilation responses in resting and exercising humans.

A

Thermal hyperpnea is the second phase panting. An increase in tidal volume associated with an increase in alveolar ventilation occurring during severe heat stress which has caused a large rise in core temperature. In animals capable of thermal panting the phase of thermal hyperpnea with its slower, deeper breathing is also named second phase panting, since it is usually preceded by a phase of typical panting PETCO2/PaCo2 is
decreased during this response.

Pulmonary ventilation

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3
Q

To describe and explain the putative neural pathways underlying the thermal hyperpnea response in hyperthermic humans

A

a

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4
Q

To define and describe selective brain cooling (SBC) in non humans.

A
  • A thermoregulatory phenomenon(?) in which the brain and body temperature are separated during exercise or body warming.
  • This allows the brain to stay cooler than the body during hyperthermia, either passively or actively.
  • Benefits to this include potential protective mechanism and water loss reduction.
  • SBC in non humans occur via countercurrent heat exchange. Non humans have a number of sites for countercurrent heat exchange e.g. nasal turbinates and the carotid rete. These sites provide greater SA for heat exchange. Countercurrent heat exchange gives gradually declining temperature differential, and that the once hot and cold streams exit at the reversed temperature difference (aka hotter entering stream exists cooler and vice versa). In the case of the brain, the cooler blood coming down mixes with the warm blood coming up such that the blood coming INTO the CAROTID RETE becomes warmer(??)
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5
Q

To describe and explain SBC in humans including the differing
avenues of heat exchange thought to participate in this response.

A

SBC also hypothesized to happen in humans
problem, however the problem is measuring human brain temp. Humans also do not have a carotid rete, whoever SBC may occur by diff avenues of heat exchange including ventilation from upper airways and surface cooling of sweat on the head. Another avenue of heat exchange may be through the cavernous sinuses, cavities located at the base of the skull. It is the only anatomic location in the human body in which an artery travels completely thru a venous structure. This suggests that despite no carotid rete in humans, there’s still a counter current heat exchange.

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6
Q

Define thermal panting

A

Increased respiratory evaporative heat loss (REHL) due to increased respiratory minute volume.

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7
Q

What is 1st phase panting or thermal tachypnea?

A
  • A RAPID RESPIRATORY FREQEUNCY accompanied by an INC in respiratory MINUTE VOLUME and, commonly, a DEC in TIDAL VOLUE, in response to a thermoregulatory need to DISSIPATE HEAT.
  • (Gk. ta- khus-swift; pnoia-breath)
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8
Q

How does PETCO2/PaCO2 change during first phase panting/thermal tachypnea?

A

PETCO2/PaCo2 is maintained during this response

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9
Q

Synonym for 1st phase panting/thermal tachypnea?

A
  • thermal polypnea
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10
Q

What is 2nd phase panting or thermal Hyperpnea?

A
  • (rapid, shallow breathing). (Gk. hyper-above, over; pnoia-breath)
  • An INC in TIDAL VOLUME associated with an INC in ALVEOLAR VENTILATION occurring during SEVERE HEAT STRESS which has caused a large RISE in Tc. In animals capable of thermal panting the phase of thermal hyperpnea with its SLOWER, DEEPER breathing is also named second phase panting
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11
Q

How does PETCO2/PaCO2 change during 2nd phase panting/thermal tachypnea?

A

since it is usually preceded by a phase of typical panting PETCO2/PaCo2 is DEC during this response.

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12
Q

Explain Slide 4

A

a

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13
Q

Describe the Pattern of breathing during panting in dogs

A

a

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14
Q

How does ventilation change in regards to inc Tc in humans?

A

Ventilation increases proportionally to core temps in humans

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15
Q

How is ventilation similar to fxn of carotid rete?

A

ventilation, like in the rabbit that has no carotid rete, is influencing BRAIN to THORAX TEMP GRADIENTS

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16
Q

Slide 7

A

a

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17
Q

Slide 7

A

a

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18
Q

Slide 8

A

a

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19
Q

Slide 9

A

a

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20
Q

Slide 10

A

a

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21
Q

Slide 11

A

a

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22
Q

Slide 12

A

a

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23
Q

Slide 13

A

a

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24
Q

Slide 15

A

a

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25
Q

Draw phrenic nerve amplitude as a fxn of temp

A

As temp inc from 25 to 38 we see an inc in phrenic nerve amplitude aka greater drive to breathe as temp inc.

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26
Q

Draw phrenic nerve amplitude as a fxn of PACO2

A

As temp inc from 25 to 38 we see an inc in PACO2 aka the higher the CO2 the higher the drive to breathe

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27
Q

Slide 17 a

A

a

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28
Q

Slide 17

A

a

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29
Q

Slide 18

A

a

30
Q

Slide 18

A

a

31
Q

Slide 18

A

a

32
Q

Slide 19

A

a

33
Q

Slide 20

A

a

34
Q

Slide 21

A

a

35
Q

Define brain meninges

A

The three membranes that envelop the brain and spinal cord. In mammals, the meninges are the dura mater, the arachnoid mater, and the pia mater. Cerebrospinal fluid is located in the subarachnoid space between the arachnoid mater and the pia mater. The primary function of the meninges is to protect the central nervous system.

36
Q

Define choroid plexus and its fxn

A

a plexus of cells that produces the cerebrospinal fluid in the ventricles of the brain. The choroid plexus consists of modified ependymal cells.

37
Q

Define subarachnoid space

A

is the interval between the arachnoid membrane and the pia mater. It is occupied by delicate connective tissue trabeculae and intercommunicating channels containing cerebrospinal fluid (CSF).

38
Q

Define epidermis

A

The surface epithelium of the skin of an animal, overlying the dermis.

39
Q

Define dermis

A

The thick layer of living tissue below the epidermis that forms the true skin, containing blood capillaries, nerve endings, sweat glands, hair follicles, and other structures.

40
Q

Define carotid rete or rete mirabile

A

The rete is a configuration of arteries and veins in a sinus at the base of the brain. The rete mirabile utilizes countercurrent BF within the net (blood flowing in opposite directions) to act as a countercurrent exchanger. It exchanges heat, ions, or gases between vessel walls so that the two bloodstreams within the rete maintain a gradient with respect to temperature, or concentration of gases or solutes.

41
Q

Define cavernous sinus

A

ne of dural venous sinuses[1] creating a cavity called the lateral sellar compartment bordered by the temporal bone of the skull and the sphenoid bone, lateral to the sella turcica

42
Q

Which researchers discovered “Brain Cooling System in Mammals” in hyperthermic animals

A

Mary-Ann Baker/ J.N. Hayward

43
Q

What is selective brain cooling (SBC)

A
  • brain and body temp are separated during exercise/body warming
  • brain stays cooler than body
44
Q

Where are the sites of countercurrent heat exchange in non humans

A
  1. Nose (nasal turbinates)

2. Carotid rete/rete mirable

45
Q

Reason for long horse nose and long dog nose?

A

Give greater SA for heat exchange

46
Q

What is countercurrent exchange or countercurrent multiplier?

A

a mechanism occurring in biological systems where there is a CROSSOVER of some property, usually HEAT or some component, BTWN 2 OPPOSING FLOWS

47
Q

What property can countercurrent exchange entail

A

can be between liquids, gases, or even solid powders, or any combo of those.

48
Q

What is countercurrent HEAT exchange

A

gives gradually DECLINING TEMP DIFFERENTIAL and that the once hot and cold streams exit at the REVERSED TEMP difference e.g. the hotter entering stream becomes the exiting cooler stream and vice versa.

49
Q

Example of area with countercurrent multiplier

A

Kidneys

50
Q

Problems with the hypothesis that SBC can occur in humans

A
  1. Problem is measuring human brain temp
  2. Humans don’t have carotid rete
  3. SBC may occur by diff mechanisms. This include ventilation from upper airways, surface cooling of sweat on the head
51
Q

What are cavernous sinuses

A
  • Cavities located at base of skull

- only anatomic location in human body in which an artery travels completely thru venous structure

52
Q

Fxn of cerebellar arteries

A

supply the ‘choriod plexus’ that are tufts of vascular tissue in 3rd and 4th ventricles that produce CSF

53
Q

What % of body weight does the brain encompass

A

2%

54
Q

What % of CO does the brain take

A

15%

55
Q

What are arteries

A

Blood supply from bilateral pairs of internal carotid and vertebral arteries to ‘Circle of Willis’

56
Q

What is the Circle of Willis

A

has anterior, middle & posterior distributing arteries; they envelope cortical hemispheres and turn 90º inward ending in capillary beds; Blood Brain Barrier

57
Q

What are veins?

A
  • thin walled, no valves
  • empty to dural sinuses
  • centrifugal drainage except for white matter
  • most drain to internal jugular vein
58
Q

Describe SBC in homeotherms

A

By changing the BF animals can turn their selective brain cooling ON and OFF.
Left: brain cooling on.
Right: brain cooling off.

In brain cooling ON, the line of IDENTITY the brain temp is LOWER than line of identity. This is the case when animal is sitting at rest and SNS activity is LOW. In SHADE selective brain cooling ON and evaporuative heat loss is REDUCED.

Leopard chasing apala, huge SNS outflow turns off selective brain cooling. In unstressed animals they cool their brain.

59
Q

What happens during minor sympathetic activity (SA)

A
  • angularis oculi sphincter (VAO) is RELAXED (α receptors)
  • facial vein sphincter (VF) is CONTRACTED (β receptors)
  • blood flows to cavernous sinus and this promotes SBC
60
Q

What happens during exercise or high-stress SA

A
  • VAO CONTRACTS
  • VF RELAXES
  • blood flows bypasses the cavernous sinus to venous jugularis. Potentially negates SBC as protective mechanism during severe exercise-induced hyperthermia and this inhibits SBC
61
Q

Slide 34

A
  • perfused cooling helmet

- induction of SBC

62
Q

What are valveless emissary veins

A
  • drain inward from scalp in hyperthemia/outward in hypothermia
  • large or microscopic veins
  • to bring cooled venous blood from the scalp to the intra-cranium
63
Q

What are the 3 main mechanisms for SBC in hyperthermia in humans

A
  1. Cooling of venous blood by SKIN which in turn cools arterial (internal carotid) blood supply to brain;
  2. Cooling by HEAT LOSS through the SKULL; EMISSARY VEINS
  3. Cooling by HEAT LOSS from the UPPER and/or LOWER AIRWAYS
64
Q

What evidence is there that supports there is selective brain cooling?

A

Cabanac 1986, trunk temp higher than brain temp.

65
Q

Capacitance hygrometry is a method for measuring

a) Shivering
b) Human panting
c) Eccrine sweating
d) Cutaneous BV

A

C) eccrine sweating

66
Q

Question 8: The NT ____ acts mainly on the ___ adrenergic class of receptors when cutaneous vessels constrict after central or core cooling:

a) NE; beta
b) NE; alpha
c) Acetylcholine; muscarinic
d) Acetylcholine; alpha

A

b) NE; alpha

67
Q

What do the cerebellar arteries supply?

A

supply the ‘choriod plexus’ that are tufts of vascular tissue in 3rd and 4th ventricles that produce CSF

68
Q

What % of total body weight does the brain weigh? What % of CO does it receive?

A
  • 2% of body weight

- 15% of CO (big need for O2 and nutrients)

69
Q

What is the purpose of rigid skull?

A

Prevents large Δ’s in cerebral blood flow (CBF)

70
Q

What are arteries?

A

Blood supply from bilateral pairs of internal carotid and vertebral arteries to ‘Circle of Willis’

71
Q

What is the circle of willis?

A

has anterior, middle and posterior distributing arteries; they envelope cortical hemispheres and turn 90º inward ending in capillary beds; at the Blood Brain Barrier

BPK 432 (17 decks)

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