Coronary Circulation and Temp Reg

Question 1

period of the cardiac cycle during which coronary blood flow in the left ventricle is lowest.

Answer 1

systole - END OF ISOVOLUMETRIC CONTRACTION

Question 2

why coronary perfusion of the left ventricular myocardium is low during systolic periods and higher during diastolic periods

Answer 2

in systole there is a compressive force that that compresses the vessels

Question 3

effect of cardiac dilation on ventricular wall tension and myocardial perfusion.

Answer 3

• The ventricular wall tension is HIGHER.Duh.
• myocardial perfusion is decreased even less
• wall tension directly translates to ovstruction (compression) of the coronary vessels

Question 4

location of the most frequent myocardial infarctions and correlate the location with coronary perfusion.

Answer 4

left ventricle-inner myocardium (subendocardiaL)

• inner myocardial vessels most compressed during systole
• Subendocardial MIs are especially prone to develop when both diastolic and systolic perfusion are low eg) Dilated Heart

Question 5

effects of increased heart rate on myocardial perfusion

Answer 5

increased heart rate = decreases time spent in diastole. = DECREASED coronary eprfusion

Question 6

why it is important to keep body temperature within a fairly tight range

Answer 6

A.) Appropriate temperature regulation is crucial to survival.
B.) Cellular functions are very sensitive to changes in body temperature.
C.) The body temperature is optimum for most cellular biochemical and transport
processes.
D.) Specific cellular dysfunctions will occur as a result of changes in body temperature.

Question 7

List the location for typical body temperature measurements. Why are values for “body temperature” for each of these areas different.

Answer 7

A.) Oral Temperature - Average 37 oC (98.6 F)
B.) Normal range for oral temperature: 36.1to 37.2 C (97-99 F)
C.) Rectal Temperature- Average 37.6 C (99.7 F)
D.) Normal range for rectal temperature: 36.1 to 37.8 C (97-100 F)
E.) Ear Temperature: Average & Range is the same as oral
F.) Axillary Temperature: Average & Range are 1 F below oral

DONT MEMORIZE THIS I GUESS?

WHY? Body temperature varies according to a circadian pattern.

Question 8

List and describe three causes for normal variations in body temperature.

Answer 8

-Body temperature is lowest just before rising in morning & highest in the late afternoon to evening.
-Body temperature of the female tends to run 0.5 C (0.9 F) higher from the time period beginning at ovulation and up to menstruation.
-During exercise & fever, the set point is elevated. The body will regulate at a higher temperature.
dehydration = higher body temp

Question 9

Differentiate between “core” and “shell” temperature

Answer 9

A.) The Core Body Temperature:
-Is the temperature of the heart, brain, thoracic and abdominal organs.
-Average 37.8 C (100 F)
-Normal range 37.2 to 38.3 C (100-101 F)
B.) The Shell Temperature - allow variance to keep core constant
-Is the temperature of skin & subcutaneous fat
-the shell temperature is quite variable. This occurs because the core body temperature must be maintained constant.
-Skin temperature generally ranges from 20-40 C (68-104 F).

Question 10

dialation of coronary vessels during normal exercise steps

Answer 10

1) Inc sympathetic tone = inc release of NE and inc in metabolsim
2) the work performed by heart will inc and heart will experience hypoxia with inc HR
3) hypoxia leads to breakdown and synth of ATP ==> AMP ACCUMULATES
4) AMP dephosphorylated to adenosine
5) Adenoside diffuses out of cells and stimulates adenosine receptors (A2) ==> VASODIALATION OF CORONARY VESSELS

Question 11

heat exchange between the body and the

environment: Radiation

Answer 11

1. Electromagnetic waves (heat waves): are a component of the electromagnetic spectrum.
2. The human body emits electromagnetic waves and when these waves strike objects that have a cooler surface than the body, heat is lost
   from the body.
3. The human body absorbs electromagnetic waves from objects having a warmer surface than body surface
4. Net heat transfer is always down a thermal gradient.
5. A naked human body ABSORBS nearly 100% of the incident radiation.
6. A body that is clothed with light colored clothes REFLECTS nearly all of the incident radiation.
7. Thus, light colored, loose-fitting clothes are cooler in hot environments with high radiation (ie - in desert sun with hot sand)

Question 12

Why does water in a pool at 72 F in which you are immersed feel cooler than air at 72 F?

Answer 12

• bc of thermal conductivity
• This parameter is an indicator of the rate at which heat transfer by conduction will occur.
• Air, for example, has a low thermal conductivity - it does not conduct heat at a very high rate.
• Water has a very high thermal conductivity - it conducts heat at a faster rate when compared to air.
• Water at 72 F will “feel” colder than being in a room where the air is at the same temperature because heat is conducted away from the body much more rapidly in water than in air.

Question 13

What is the mechanism by which a wet suit keeps you feeling relatively warm in cold water.

Answer 13

-A scuba diving wet suit inhibits convective heat transfer. The body traps a layer of water inside the wet suit. The body heats this layer and maintains this temperature because heat transfer is minimized between the layer of water next to the body and the wet suit. The wet suit is made from neoprene rubber which an insulator (i.e. does not promote heat transfer at an appreciable rate).

Question 14

Describe the role of cutaneous and core thermoreceptors in altering the hypothalamic temperature regulating responses.

Answer 14

Temperature sensors are present in the skin and the core of the body (more on these later). Data from the various temperature sensors are received by the hypothalamus. The hypothalamus can evoke the various behavioral/biochemical responses (shown above) which are appropriate to the change in temperature.

Question 15

temperature-induced change in skin blood flow

Answer 15

• The rule: most organs control their blood flow according local factors and events - and do not pay much attention to what the brain says. For example, if skeletal muscle requires increased blood flow - dilation is achieved according to the presence of local metabolites.
• The exception: Blood flow to the skin is primarily under central control because one of the major functions of the skin is overall temperature regulation.

Question 16

temperature-induced change in sweating

Answer 16

• Since water pulls significant heat energy on evaporation, appreciable amount of energy is lost when sweating.
• Energy loss = 0.58 Kcal per ml of evaporated liquid.
• It is significant to note that in order for heat transfer to take place (i.e. to cool the body), the fluid must evaporate.
• So, just having water move from the inside of the body to the skin does not accomplish heat transfer.
• Is a sympathetic cholinergic event.
• Muscarinic Receptors - are activated on the merocrine sweat glands.

Question 17

temperature-induced change in shivering

Answer 17

-Shivering is mediated by the Primary Motor Center for Shivering in the Posterior Hypothalamus.
-Maximum shivering can increase heat production by a factor of 4 to 5 in comparison to resting levels. With respect to short term
thermoregulatory control, shivering is most important - it can have the greatest response.

Question 18

temperature-induced change in piloerection

Answer 18

• mechanism for ehat gain
• “Goosebumps” - arrector pili muscles will be activated by via alpha1 receptors and increased sympathetic tone.
• These muscles are attached to cutaneous hair follicles.

Question 19

temperature-induced change in epinephrine and NE

Answer 19

HEAT GAIN MECH
a. Norepinephrine & epinephrine will stimulate “brown fat”.
b. Brown Fat is a specialized type of fat which is well suited for the generation of heat.
c. Heat is produced by uncoupled oxidative phosphorylation. This is a type of oxidative phosphorylation which doesn’t produce ATP. Sympathetic activation is via beta1 receptors or
possibly through beta3 receptors.
d. Human newborns are born with large amounts of brown fat located between the scapula and the heart.
e. This mechanism is important since newborns do not have the neurological sophistication that enables shivering.

Question 20

heat exchange between the body and the

environment: Conduction

Answer 20

1. This mode of heat transfer occurs between objects in DIRECT CONTACT.
2. Net Heat transfer by conduction always moves down a thermal gradient (from warmer to cooler object).
3. The rate of heat transfer is a function of TEMPERATURE DIFFERENCE and THERMAL CONDUCTIVITY.

Question 21

heat exchange between the body and the

environment: Evaporation

Answer 21

1. Water “takes with it” a high number of calories when it evaporates.
2. One avenue of water loss from the body is by “insensible” loss. Insensible loss is evaporative heat loss that is not associated with active sweating.
3. Approximately one liter per day is lost from the lungs and skin.
4. One liter per day translates into the loss of 580 Kcal per day.
5. Since the resting metabolic rate is approximately 2400 Kcal per day, approximately 25% of our energy is consumed by evaporative heat loss.

Question 22

Heat transfer by convection:

Answer 22

• Heat transfer by convection occurs down a temperature gradient as a result of air (or water) currents or movements.
• In dissipating heat, skin warms the layer of air next to it.
• Once air temperature is equal to skin temperature, no further reduction in temperature will occur. So, the removal of this layer by air circulation increases the gradient and hence the heat loss.
• So, fans and wind promote convective heat loss.
• Loose fitting clothes allow convection.

Question 23

Thyroid Response to temperature change:

Answer 23

a. Thyroid hormone is considered a thermogenic hormone.
b. In response to change in temperature, the hypothalamus can adjust this path.
c. If cold, the hypothalamus would turn this path on, and if hot, this path would be shut down.

Question 24

Motor Neurons and temperature:

Answer 24

a. The hypothalamus is capable of eliciting the response of motor neurons.
b. If cold, the motor neurons will be activated and muscle tone will increase to the extent that shivering will occur.
c. Some type of behavior may also be modified - such as putting on a coat.

Question 25

Sympathetic Response and temperature:

Answer 25

a. The hypothalamus can also affect sympathetic pathways in the autonomic nervous system.
b. Adrenergic Response - blood vessels of the skin:
- The sympathetic nervous system will influence blood flow to the skin. Blood vessels will be either dilated or constricted.
- Blood vessels in the skin contain almost all alpha 1 receptors.
3. Increased sympathetic tone will activate alpha1 receptors and cause vasoconstriction.
4. Reduction of sympathetic tone to the skin will result in vasodilation.
5. Anxiety sweating in the palms of the hands and soles of the feet is caused by activation of the few sweat glands that have apha1 receptors. -most sweat glands have muscarinic receptors and their innervation is by sympathetic cholinergic fibers.
c. Sympathetic Cholinergic Response - sweat glands of the skin:
- Innervation of sweat glands is one of the exceptional cases in that the postganglionic fibers release acetycholine rather than norepinephrine and stimulate muscarinic receptors on the sweat glands.

Question 26

Warm receptors effect when increase in temperature?

Answer 26

firing frequency will increase with increasing temp

Question 27

Cold receptors effect when increase in temp?

Answer 27

firing frequency will decrease with increasing temp

Question 28

Skin temperature and core temperature are integrated together where?

Answer 28

ant hypothalamus

Question 29

“Anxiety Sweating”

Answer 29

a. Results from sympathetic adrenergic stimulation of the few sweat glands (in the palms of the hands & soles of the feet) that have alpha1 receptors.
b. “Cold” (vasoconstricted) & “clammy” (sympathetic adrenergic anxiety sweating) hands result from anxiety sweating of a nervous person.

Question 30

Apocrine Glands location and control?

Answer 30

a. Located in the axillary areas.
b. Are under sympathetic adrenergic control.
c. Their secretions are thicker and odorous.

Question 31

If brain temperature rises above set point

Answer 31

-There will be a cutaneous dilation which will be mediated by a decreased adrenergic tone. Again, adrenergic tone implies the release of
norepinephrine.
-Recall, that in the skin, the arterioles and AV anastomoses have predominantly alpha1 receptors in which the norepinephrine binds and elicits response.

Question 32

Stimulation of Thyroid Axis:

Answer 32

• This pathway begins in the hypothalamus - which releases a hormone called Thyroid Releasing Hormone (TRH).
• TRH is released into portal circulation and is picked up by the anterior pituitary.
• In response, the anterior pituitary releases Thyrotropin (TSH) - which acts on the thyroid.
• The thyroid is stimulated to produce and release thyroxin (T4) and triiodothyronine (T3).
  k. Thyroid hormones increase cellular metabolism and heat production.

Question 33

blood flow to r ventricle

Answer 33

the R ventricle doesnt have to overcome pressure in the aorta so it doesnt really ever compromise its blood flow… unless COPD or similar when R ventricle hypertrophies

Question 34

Angina frequently associated with increased

HR because of

Answer 34

low perfusion.