LAB DEMO 1

Question 1

Eccrine sweat glands are under sympathetic _____ control and the _______ of these eccrine sweat glands vary over the surface of the body. These glands secrete fluid that varies in their electrolyte and solute
concentrations as a function of ________ and ________ state of the individual. ________ of eccrine sweat from
the skin surface provides the most powerful cooling system for the human body

Answer 1

Eccrine sweat glands are under sympathetic CHOLINERGIC control and the DENSITY of these eccrine sweat glands vary over the surface of the body. These glands secrete fluid that varies in their electrolyte and solute
concentrations as a function of TRAINING and ACCLIMATION state of the individual. EVAPOURATION of eccrine sweat from
the skin surface provides the most powerful cooling system for the human body

Question 2

_________ of eccrine sweat from the skin is considered quantitatively to be the most important avenue of heat loss for humans during _______. Forehead _______ (Esw) in this lab will be measured using the _______ method. A capsule (surface area: 5.31 cm2 ) will be secured to the ______ using a headband and flushed with a _______ air source a rate of 1 L • min-1 . The relative humidity (RH) of the dry air source will be verified by a __________ (RH201C, Omega Engineering Inc., Stanford, CT, USA) in a sealed container. Next air will be passed through a capsule on the forehead where it will be ______ after the participant begins to sweat. Finally, the humidified air will be passed from the forehead capsule through a third sealed container enclosing a __________ (HMT337, Vasaila, Helsinki, Finland) in order to measure the RH of the air after passing over the forehead. The HMT337 capacitance hygrometer is employed because it is capable of measuring RH in _________ conditions. Eccrine sweat rate will be calculated with the equation in Bullard (1) with the inclusion of the ________ of the sweat capsule (m2 ):

Answer 2

EVAPOURATION of eccrine sweat from the skin is considered quantitatively to be the most important avenue of heat loss for humans during HYPEREMIA. Forehead ECCRINE SWEAT (Esw) in this lab will be measured using the VENTILATED CAPSULE method. A capsule (surface area: 5.31 cm2 ) will be secured to the FOREHEAD using a headband and flushed with a DRY COMPRESSED air source a rate of 1 L • min-1 . The relative humidity (RH) of the dry air source will be verified by a RESISTANCE HYGROMETER (RH201C, Omega Engineering Inc., Stanford, CT, USA) in a sealed container. Next air will be passed through a capsule on the forehead where it will be HUMIDIFIED after the participant begins to sweat. Finally, the humidified air will be passed from the forehead capsule through a third sealed container enclosing a CAPACITANCE HYGROMETER (HMT337, Vasaila, Helsinki, Finland) in order to measure the RH of the air after passing over the forehead. The HMT337 capacitance hygrometer is employed because it is capable of measuring RH in NEAR CONDENSATION conditions. Eccrine sweat rate will be calculated with the equation in Bullard (1) with the inclusion of the SURFACE AREA of the sweat capsule (m2 ):

Question 3

ESW (mg·m-2·s-1) = FAIR (L⋅s
-1) • (Δ RH ÷ 100) • ρair (mg⋅L-1)] • [SA (m2)]-1

Describe each component

Answer 3

ESW is the calculated eccrine sweat rate; FAIR is the air flow rate through the forehead capsule; Δ RH is the change in RH between the first and second humidity sensor; ρair is the density of the saturated steam at the ambient dry bulb temperature (°C), use 19.877 mg/L for ρair; and SA is the surface area of skin covered by the sweat capsule

Question 4

A brief synopsis of the physiology and function of cutaneous vasodilatation is given as background for this second part of this lab.

Cutaneous vasodilatation is a ______ response in acral regions and a ______ response in nonacral regions of the body. In the acral regions the cutaneous blood vessels are under a ________ control whereas non-acral regions are under _________ control and a _________ system.

The first phase in the non-acral regions of the body surface includes a _______ control followed by an _______ control that includes __________ and unknown __________(s).

Answer 4

A brief synopsis of the physiology and function of cutaneous vasodilatation is given as background for this second part of this lab.

Cutaneous vasodilatation is a SINGLE-PHASE response in acral regions and a 2-PHASE response in nonacral regions of the body. In the acral regions the cutaneous blood vessels are under a SYMPATHETIC NORADRENERGIC control whereas non-acral regions are under NORADRENERGIC VASOCONSTRICTOR control and a NON-ADRENERGIC ACTIVE VASODILATOR system.

The first phase in the non-acral regions of the body surface includes a SYMPATHETIC NORADRENERGIC control followed by an ACTIVE CUTANEOUS VASODILATION control that includes ACH and unknown COTRANSMITTERS (s).

Question 5

Cold-induced reflex vasoconstriction in the limbs can substantially reduce _____ blood flow and allows a
______ of heat. The CNS mediated mechanism of vasoconstriction is via ______ neurons releasing norepinephrine that binds to _________ receptors on vascular smooth muscle. Other details of this reflex vasoconstriction, that appears to involve co-transmitters and _______ vasoconstriction,
are given by Kellogg 2006.

Answer 5

Cold-induced reflex vasoconstriction in the limbs can substantially reduce PERIPHERAL blood flow and allows a CONSERVATION of heat. The CNS mediated mechanism of vasoconstriction is via ADRENERGIC SYMPATHETIC neurons releasing norepinephrine that binds to A1 AND A2 receptors on vascular smooth muscle. Other details of this reflex vasoconstriction, that appears to involve co-transmitters and LOCAL COOLING INDUCED vasoconstriction,
are given by Kellogg 2006.

Question 6

Theory of Laser Doppler Velocimetry:

A beam of _____ light, carried by a ______ probe, is widely scattered and partly absorbed by _______. Light hitting moving ______ in these tissues undergoes a change in
wavelength known as a _______. The wavelength of light hitting static objects is ______ in these tissues.

The magnitude and frequency distribution of these changes in wavelength are directly related to the _____ and _____ of blood cells but unrelated to their ______ of movement. The information is picked up by a returning _____, is converted into an _____ signal. No currently available laser Doppler instrument can present absolute perfusion values (e.g. ml/min/100 gram tissue). Measurements are expressed in arbitrary _______ (PU) or Arbitrary Units. To enable comparison of results, it is important to _______ the laser Doppler.

Answer 6

Theory of Laser Doppler Velocimetry:

A beam of LASER light, carried by a FIBRE-OPTIC probe, is widely scattered and partly absorbed by SURFACE TISSUES. Light hitting moving BLOOD CELLS in these tissues undergoes a change in
wavelength known as a DOPPLER SHIFT. The wavelength of light hitting static objects is UNCHANGED in these tissues.

The magnitude and frequency distribution of these changes in wavelength are directly related to the NUMBER and VELOCITY of blood cells but unrelated to their DIRECTION of movement. The information is picked up by a returning FIBRE OR FIBRES, is converted into an ELECTRICAL signal. No currently available laser Doppler instrument can present absolute perfusion values (e.g. ml/min/100 gram tissue). Measurements are expressed in arbitrary PERFUSION UNITS (PU) or Arbitrary Units. To enable comparison of results, it is important to CALIBRATE the laser Doppler.

Question 7

What is the FLUX

Answer 7

estimate of the RBC flux in the cutaneous tissues. It is a quantity proportional to the product of the average speed of the blood cells and their # concentration (often referred to as blood volume).

Question 8

What is CONC

Answer 8

estimate of the RBC conc in the cutaneous tissues

Question 9

What is DC

Answer 9

the reflectance value of the tissue. This value gives a measure of the total intensity of the backscattered light
Typical DC values for a standard optical probe (e.g. MP 1 or MP 2) is 30 to 50 although this value varies

Question 10

What is FS

Answer 10

Output scale settings for analog output. The default setting is 1000 arbitrary units (AU) for 0 to 10 V. Other
scale settings are 500, 200, 100, 50, 20 and 10.

Question 11

How is laser doppler calibrated

Answer 11

The laser Doppler probes are calibrated with polystyrene microspheres undergoing thermal or Brownian motion. The average speed of the microspheres is proportional to the square root of the temperature in Kelvin. Ideally the calibration is at the same temperature, although a change of ±5°C gives only ±1% change in the mean speed of the microspheres.

Question 12

What is the Data Output Rate/Frequency

Answer 12

This varies with the number of channels. For 1 to 2 channels the frequency is 40Hz for 2 to 3 channels the frequency is 20Hz.

Question 13

What are the units

Answer 13

Arbitray Units (AU) are employed for FLUX, CONC, SPEED and DC.

Question 14

What is the Flux Accuracy

Answer 14

± 10 AU for a Moor Standard DRT4 probe

Question 15

What is the Flux Precision

Answer 15

± 3% of measurement value

Question 16

Shivering is an _______ tremor of skeletal muscles not involving voluntary movements or external _____. It is a _______ response giving increased contractile activity of skeletal muscles to increase metabolic heat production. It is referred to as shivering thermogenesis and has an _______ distinct pattern of motor unit discharges that is quantified as the _______ deflections per unit time (t): Σ(ΔV·Δt)·t –1 ·[V].

Answer 16

Shivering is an INVOLUNTARY tremor of skeletal muscles not involving voluntary movements or external WORK. It is a THERMOEFFECTOR response giving increased contractile activity of skeletal muscles to increase metabolic heat production. It is referred to as shivering thermogenesis and has an ELECTROMYOGRAPHICALLY distinct pattern of motor unit discharges that is quantified as the INTEGRATED VOLTAGE deflections per unit time (t): Σ(ΔV·Δt)·t –1 ·[V].

Question 17

As body temps dec, shivering thermogenesis progresses from increased thermoregulatory _____, to ______, to ______ of both flexor and extensor muscles. The shivering pathway begins with signals from the _____ or the ______. These impulses are conducted by ______ neurons down the _______ tract through the
______ of the spinal cord and across synapses to large ______ neurons or _______ neurons in the brainstem and spinal cord. Upper motor neurons release ________ that is received by sensory receptors of nicotinic receptors on the alpha motor neurons.
Alpha motor neurons send an impulse down their axons via the ________ of the spinal cord. Subsequently alpha
motor neurons release ACh from their axon terminal knobs at the NMJs of skeletal muscles and this received by postsynaptic _______ receptors of skeletal muscles. Shivering thermogenesis is blocked by curare. _____, specifically tubocurarine, is a toxic alkaloid that is found as a resinous extract from ______ plants. It acts as a muscle ________ and is used in anesthesia. Outside of clinical settings curare was used in the past in arrow poisons during hunting by people indigenous to South America living in the in the valleys of the Amazon and the Orinoco rivers. Curare competes with ______ for binding on nicotinic receptors and blocks transmission of the signal from ______ neurons to the skeletal muscle involved in shivering.

Answer 17

As body temps dec, shivering thermogenesis progresses from increased thermoregulatory MUSCLE TONE, to MICRO-VIBRATIONS, to CLONIC CONTRACTION of both flexor and extensor muscles.

The shivering pathway begins with signals from the PRECENTRAL GYRUS or the PREMOTOR CORTEX. These impulses are conducted by UPPER MOTOR neurons down the CORTICOSPINAL tract through the VENTRAL HORN of the spinal cord and across synapses to large LOWER MOTOR neurons or ALPHA MOTOR neurons in the brainstem and spinal cord.

Upper motor neurons release ACH that is received by sensory receptors of nicotinic receptors on the alpha motor neurons. Alpha motor neurons send an impulse down their axons via the VENTRAL ROOT of the spinal cord. Subsequently alpha
motor neurons release ACh from their axon terminal knobs at the NMJs of skeletal muscles and this received by postsynaptic NICOTINIC ACH receptors of skeletal muscles. Shivering thermogenesis is blocked by _____. Curare, specifically tubocurarine, is a toxic alkaloid that is found as a resinous extract from TROPICAL plants. It acts as a muscle RELAXANT and is used in anesthesia. Outside of clinical settings curare was used in the past in arrow poisons during hunting by people indigenous to South America living in the in the valleys of the Amazon and the Orinoco rivers. Curare competes with ACH for binding on nicotinic receptors and blocks transmission of the signal from ALPHA MOTOR neurons to the skeletal muscle involved in shivering.

Question 18

Electromyograms (EMG) give one method to quantify _______ thermogenesis. Indirect and direct _______ can also estimate shivering thermogenesis, but the focus here is EMG. Electromyograms give a recording of the ionic
potential associated with the ________. With increasing activation of motor units there is an increase in the electrical activity of the muscle. The EMG method employs surface electrodes that record muscle action potentials that occur mostly in the frequency range of _____ Hz. These signals are acquired by a data acquisition
system and then the data is processed to quantify the level of activity in the muscle.

Answer 18

Electromyograms (EMG) give one method to quantify SHIVERING thermogenesis. Indirect and direct CALORIMETRY can also estimate shivering thermogenesis, but the focus here is EMG. Electromyograms give a recording of the ionic
potential associated with the MUSCLE ACTION POTENTIALS. With increasing activation of motor units there is an increase in the electrical activity of the muscle. The EMG method employs surface electrodes that record muscle action potentials that occur mostly in the frequency range of 30 TO 300 Hz. These signals are acquired by a data acquisition system and then the data is processed to quantify the level of activity in the muscle.

Question 19

A raw EMG signal typically is given a _______. This is to invert all signals that are less than the _______ making all signal values ______. The rectified signal is then typically ______ to give the area under the curve and this area is proportional to the _______. Another method to quantifying the raw EMG signal is to calculate a ______. This moving average method is to allow one to see ______ in muscle activity as a function of time. The greater number of points chosen for the moving average gives a greater ______ of the raw EMG signal.

Answer 19

A raw EMG signal typically is given a FULL WAVE RECTIFICATION. This is to invert all signals that are less than the ISOELECTRIC LINE making all signal values POSITIVE. The rectified signal is then typically INTEGRATED to give the area under the curve and this area is proportional to the MUSCLE ACTIVITY. Another method to quantifying the raw EMG signal is to calculate a MOVING AVG. This moving average method is to allow one to see INCREASES OR DECREASES in muscle activity as a function of time. The greater number of points chosen for the moving average gives a greater SMOOTHING of the raw EMG signal.

Question 20

Plot Figure 1 using your data and Excel in a scatterplot to allow you to answer this question. What was the core
temperature (TCORE) threshold for eccrine sweating (Esw)?

Answer 20

A

Question 21

Plot Figure 2a and 2b using your data and MS Excel in a scatterplot to allow you to answer this question. What were the two core temperature thresholds from the two cutaneous vasodilatation measurements?

Answer 21

A

Question 22

Calculate and state the suprathreshold gain or slope of the eccrine sweating (E . sw) vs. TCORE plot in Figure 1.

Answer 22

A

Question 23

Calculate and state the suprathreshold gains or slopes from Figure 2a, 2b for the cutaneous vasodilatation vs TCORE. Show all calculations.

Answer 23

A

Question 24

Calculate the mean skin temperature from the surface sites employed. Show all calculations. Plot Figure 3 of mean skin temperature vs. TCORE using your data and Excel in a scatterplot to allow you to answer this question. What was the mean skin temperature at the onset of both sweating and increases in cutaneous blood velocity? What would you expect to happen to these thresholds if we held skin temperature at a lower level? Same question if we held skin temperature at a higher level?

Answer 24

A

Question 25

What other information would be required to determine a participant’s set-point of temperature regulation or a participant’s null zone of thermoregulation? How would you obtain (i. e. what experiment should you conduct?) to get the remaining information to establish either a participant’s set-point of temperature regulation or a participant’s null zone of thermoregulation?

Answer 25

A

Question 26

From your readings to date, speculate on the influence of a higher rate of increase of core temperature on the onsets of sweating and increases in cutaneous blood velocity. Same question for a lower rate of increase of core temperature.

Answer 26

A

Question 27

Speculate on how you would expect the threshold and gain of these two thermoregulatory responses to change in a heat-acclimatized athlete who lives and trains a hot humid climate?

Answer 27

A