Thermoregulation Flashcards
What’s a normal body temperature?
Morning –> 36.7 C (98.06 F)
Normal Range (in the morning) –> 36.3 - 37.1 C
What is a feed-forward system?
Information is used to PREVENT changes in the controlled variable (i.e it’s cold outside and you wear a coat to keep your core-temperature normal)
Differentitate between Warm- and Cold-Sensitive Thermoreceptors.
Warm-Sensitive Thermoreceptors –> Firing rate increases as local temperature goes UP; TRP-V1 - V4 which are sensitive over different ranges; Capsaicin is a protein that is in spicy foods; Firing rate will hit a maximum and then starts to decrease which deals with the different thermoreceptors
Cold-Sensitive Thermoreceptors –> Firing rate increases as local temperature goes DOWN; TRPM8 and TRPA2; Also activated by Menthol;
**** Neurons which change their firing rate in response to changes in local temperature
**** Opening of the various channels will allow Na+ or Ca2+ to enter the cell!
**** Found in the Skin, Viscera, and the BRAIN
What is the main “controller” of body temperature?
How does it respond to Heat versus the Cold?
HYPOTHALAMUS!
Response to HEAT –> Activation of the Anterior Hypothalamic areas when we are trying to LOSE heat (cool down)
Response to COOLING –> Activation of the Posterior Hypothalamic areas when we are trying to GAIN heat (warms you up!)
Describe changes in body temperature with Activity.
Sleep –> Temperature DECREASES (Circadian influence, set point decreases)
Exercise –> Temperature INCREASES (Increase heat production, set point increases)
Setting the temperture in the body is only based on one parameter, what is it?
How does the hypothalamus actually perform its “thermostat” duties?
ONLY interested in the CORE TEMPERATURE!!! (We DO NOT have a set point for skin temperature)
**** Hypothalamus has a set of neurons that establishes the “Set Point” by matching Action Potential Numbers
How do you know your current body temperature?
How do you know what the temperature of the external environment is?
Current Body Temperature –> Temperature affects enzyme activity (Q10); Cellular function will change usually for the worse; Thermoreceptors are going to be in the BRAIN and the VISCERA (Food ingested may change your body temperature, tells hypothalamus about these threats!)
Environmental Temperature –> Thermoreceptors are going to be in the SKIN! Cutaneous Thermoreceptors are BIMODAL (Temperature and Touch) and may be warm or cold-sensitive (10x more cold-sensitive receptors). Visceral Thermoreceptors can also respond to changes in the external environment (i.e. ingesting ice cream)
Where are the Central Thermoreceptors located?
Are there more Warm- or Cold-Sensitive Neurons here?
PRE-OPTIC and SUPEROPTIC region of the hypothalamus
**** 3x as many warm sensitive neurons; Relay information to other regions of the Hypothalamus
Which sequence does the Hypothalamus use in order to determine the “Set Point” for body temperature?
- Integration of Afferent Signals
- Determination of “Set Point”
- Compare Core Temperature to “Set Point”
- Responds to environment
How is Heat Produced in the body?
- *1. Mechanisms:**
- ANS: Sympathetic Nervous System
- Hormonal –> Thyroxin, Epinephrine/Norepinephrine
- *2. Ways of Producing Heat:**
- Muscular Activity –> Initiate VOLUNTARY MOTION via the Cortex* (jumping around) and SHIVERING (produced by *DORSOMEDIAL POSTERIOR HYPOTHALAMUS), Excitation from the hypothalamus is going to be tied to your breathing rate!
- Non-Shivering Thermogenesis –> HORMONAL (Thyroxin, Epinephrine), Increase FOOD INTAKE (increases the metabolic rate) and BROWN Adipose Tissue
Describe the purpose of Brown Adipose Tissue.
- Low efficiency hydrolysis of ATP (energy is LOST as HEAT)
- Innervated by SYMPATHETIC Nervous System and EPINEPHRINE is going to INCREASE Un-Coupling Protein’s (UCP) activity
- Strong presence in infants; Recent studies show existance in ADULTS within the White Fat
Talk about the different mechanisms for Heat Loss in the body.
*** Controlled in the ANTERIOR HYPOTHALAMUS!
EVAPORATIVE Heat Loss:
- Insensible (Respiration)
- Sweating (Controlled)
CONVECTION Heat loss:
- Molecules move away from contact (air heating and rising)
CONDUCTION Heat Loss:
- Transfer of heat between objects IN physical contact with one another
RADIATION Heat Loss:
- Infrared radiation transferring heat between 2 objects NOT IN Physical Contact
Talk about some responses that will occur in the body when you have an INCREASED core temperature.
DECREASED Heat Production –> Apathy/inertia (Not moving much), Anorexia
INCREASED Heat Loss –> Blood to Skin, Sweating, Insensible heat loss (Panting)
Describe the innervation to Sweat Glands.
Sympathetic Cholinergic binding to a MUSCARINIC receptor
*** Releases ACETYLCHOLINE
Describe the composition of Sweat.
Differentiate between Low and High Flow Rates.
- Coiled-Region* –> Composition is essentially the same as Plasma (no-proteins)
- Moving-up the Gland* –> Water and Na+ are reabsorbed into the DUCT of the sweat gland
Low Flow Rate –> CONCENTRATED (Little water and HIGH Na+), Na+ control is regulated by ALDOSTERONE
High Flow Rate –> DILLUTED (LOTS of water and Low Na+); Working out heavily and you need to sweat a lot
