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Neuroscience I > Thermoregulation Lecture (Dr. Karius) TEST 2 > Flashcards

Thermoregulation Lecture (Dr. Karius) TEST 2 Flashcards

1
Q

Normal Body Temperature

A
  • In the MORNING: 36.7 Degrees Celsius

- The NORMAL RANGE: 36.3 to 37.1

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2
Q

Control Systems

A

1) Controlled Variable

2) Is measured by
- —>

3) Sensory
- —->

4) Controller (SET POINT)
- —->

5) Effector
- —->

This is a FEEDBACK System, Information is FED BACK to the CONTROLLER to Report CHANGES in the Controlled Variable*

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3
Q

Variable Maintained around a Set Point

A
  • Any change in the Controlled Variable causes a Reaction that brings it back to the SET POINT!!!
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4
Q

Feed- Forward Systems

A
  • In Feed- Forward System, information is used to PREVENT Changes in the Controlled Variable
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5
Q

Negative Feedback Systems

A
  • The Vast Majority of Feedback Systems in the Human Body are NEGATIVE FEEDBACK
  • Thermoregulation is one of these, although there are FEED-FORWARD Aspects
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6
Q

Thermoreceptors

Definition

A

DEFINITION: Thermoreceptors are Neurons which Change their FIRING RATE in Response to Changes in LOCAL TEMPERATURE

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7
Q

Thermoreceptors

Description

A
  • Presumed to be BARE NERVE EDINGS (Neuritis Complex)
  • May be WARM or COLD Sensitive
  • Found in:
    1) The SKIN!!!!!!!
    2) The VISCERA!!!!!!
    3) The BRAIN!!!!!!
  • Different Locations tell the Brian about DIFFERENT TEMPS

WARM SENSITIVE:

  • 4 Channels Id’d so far
  • TRP-V1 through 4!!!!!!!!!!!!!
  • Sensitive Over Different Ranges
  • V = VANILLOID = CAPSAICIN (Hot Peppers)!!!!!!!!!!
  • Allows Na+ or Ca++ INFLUX

COLD SENSITIVE:

  • Two Receptors
    a) TRPM8 (= CMR-1)
    b) TRPA2?
  • Also ACTIVATED by MENTHOL!!!!
  • Activation:
    a) Opens as Temp DECR
    b) Allows Na+ or Ca++ INFLUX
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8
Q

Hypothalamus

A
  • The Hypothalamus has the Connections to Control the HORMONAL, AUTONOMIC, and BEHAVIORAL Changes that are part of Thermoregulation
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9
Q

Thermoregulatory System

Respons to Hear and Cold

A

1) ANTERIOR HYPOTHALAMUS:
- Response to HEAT!!!!
* ** HEAT LOSS Behavior!!!

2) POSTERIOR HYPOTHALAMUS:
- Response to COOLING!!!!
* * HEAT PRODUCTION Behavior!!!!1

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10
Q

Core Temperature

A
  • Core Temp: 36
  • Oral Temp: 34
  • “Average Skin”: 32
  • Hands: 30
  • Feet 26
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11
Q

Body Temp Changes with Activity

A

1) With SLEEP:
* ** TEMP DECREASES!!!!***
- Circadian Influence!
- Set Point Decrease?

2) With EXERCISE:
* ** TEMP INCREASES (As HIGH as 40C)!!!**
- INCR Heat Production
- Set Point Increase

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12
Q

Body Temp is Influenced by the Circadian Rhythm

A
  • Varies about 1 to 2 Degrees over 24 Hour Period

*** LOW at 6:00 am!!!!!

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13
Q

The Hypothalamus- Core Temp

A
  • The Hypothalamus has a “SET POINT” for Core Temperature!!!!

SET POINT: the Desired Value

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14
Q

Current Body Temp and the Temp around the Body

A

What my Current Body Temp is:

  • Temp affects ENZYME ACTIVITY (Q10)
  • Will Change CELLULAR FUNCTION
  • For better or Worse (Usually Worse)

What is the Temp around Me:
- Environmental Temperature is a Threat to MY TEMP

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15
Q

Thermoreceptors in the Core and Cutaneous

A

1) Thermoreceptors in “CORE”:
- Brain
- Viscera

2) Cutaneous Thermoreceptors:
- Axons located IN SKIN

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16
Q

Peripheral Thermoreceptors

A
  • Often BIMODAL (Temp and Touch Sensitive)
  • May be Warm or Cold Sensitive
  • ** 10x as many COLD SENSITIVE!!!!!****
  • These tell us about ENVIRONMENTAL CONDITIONS!!!!!
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17
Q

Visceral Thermoreceptors

A

Why would I put Thermoreceptors in the Gut?
- Not just sending Core Temp

  • Threats to Maintenance:
    a) Food Ingested may Change Body Temp
    b) Tell Hypothalamus about these Threats
18
Q

Central Thermoreceptors

A

LOCATION:

1) PREOPTIC Region of Hypothalamus
2) SUPEROPTIC Region of Hypothalamus

WHAT:

  • Neuron cell Bodies Sensitive to CHANGE Sin Temp
    a) 3x as many WARM SENSITIVE RECEPTORS
    b) They relay their Information to Other areas of the Hypothalamus

****These Regions detect CORE TEMPERATURE!!!!!!

19
Q

The Hypothalamus and Thermoregulation

A
  • Integration of AFFERENT
    1) Determination of “Set Point”
    2) Compare CORE TEMP to “Set Point”
    3) If Different: Generate RESPONSE
    4) RESPOND to Environment
20
Q

Effectors of the Hypothalamus

A

1) Heat Production

2) Heat Loss

21
Q

Heat Production

A

MECHANISM:

1) ANS: SYMPATHETIC System!!!!!
2) HORMONAL:
a) Thyroxin
b) Epinephrine/ Norepinephrine

2) WAYS to PRODUCE HEAT
a) MUSCULAR ACTIVITY
b) NON-SHIVERING THERMOGENESI (Non-Muscular)

22
Q

Heat Production

Muscle Activity

A

MUSCULAR ACTIVITY

1) SHIVERING
a) DORSOMEDIAL POSTERIOR HYPOTHALAMUS!!!!!!!!!!!!!!
b) Incr Motoneuron Excitation

2) INCR Voluntary Activity
a) Via CORTEX
b) Jumping, Running

23
Q

Heat Production

Non-Shivering Thermogenesis

A

1) HORMONAL INGLUENCE STRONG:
a) THYROXIN INCR Metabolic Rate (Heat Production)
- Stimulus for TRH Release: COLD

b) EPINPEHRINE
2) INCR Food Intake: INCR Metabolism
3) BROWN ADIPOSE TISSUE

24
Q

Heat Production

Brown Adipose Tissue

A

1) LOW EFFICIENCY HYDROLYSIS of ATP
- Low Efficiency = Lots of Heat Production

2) SYMPATHETIC
a) Innervation of Brown Fat
b) Circulating Epinephrine (A Catecholamine)

3) IMPORTANCE IN HUMAN:
a) STRONG in Infants
b) Recent Evidence shows Existence in Adults

Additional Information:

  • Distribution APPEARS to differ from that of Other Animals
  • Requires EXPOSURE to COLD (Acute)
  • Requires SYMPATHETIC ACTIVATION
25
Q

Heat Loss

A

ANTERIOR!!!!!!!!!
(Heat Loss Behavior)

***EVAPORATION Heat Loss: Energy (Heat) LOST as WATER EVAPORATES

Two Kinds of Heat Loss:

1) INSENSIBLE (Respiratory)
2) SWEATING (Controlled)

26
Q

Heat Loss

Convection and Conduction

A

CONVECTION:
- Movement of MOLECULES AWAY from Contact (Air Heating and Rising)

CONDUCTION:
- Transfer of Heat between Object in PHYSICAL CONTACT with One Another

RADIATION:
- Infrared Radiation transferring HEAT between 2 Objects NOT in PHYSICAL CONTACT

How can we Control These Forms?
- Add layers of Clothing!!!

**In ODER to respond to Chagnes in CORE TEMPERATURE, the HYPOTHALAMUS will ADJUST BOTH HEAT LOSS and HEAT PRODUCTION

27
Q

Integrative Response: INCREASE Core Temp

A

( Tb > Tset point)

1) DECREASE Heat Production:
- Apathy/ Inertia
- Anorexia

2) INCREASE Heat Loss:
- Blood to Skin
- EHL (Sweat)
- Insensible Heat Loss (Pant)

28
Q

Heat Loss

A
  • How much Blood is sent to the Skin determines how much HEAT MOVES from Blood to External Environment
29
Q

Sweating

A

SWEAT GLAND:

  • Lots of Blood Vessels Nearby
  • Coiled Region by Vessels
  • DUCT LEADING to the SKIN

INNERVATION:

  • ** SYMPATEHTIC CHOLINERGIC!!!!****
  • ACh is the Neurotransmitter, biding to MUSCARINIC RECEPTOR!!!
30
Q

Sweating Cont

A

Primary Secretion is HIGH in:

  • Water
  • Sodium
  • **Primary Secretion is PLASMA (no proteins)
  • ** WATER and SODIUM are REABSORBED (Taken Back to the Blood) in the DUCT of the Sweat Gland!!!!!
  • Cl can also be Reabsorbed along the Duct

LOW FLOW RATES of SWEAT:

  • CONCENTRATED Sweat*
  • LITTLE Water
  • HIGH SODIUM

HIGH FLOW RATES of SWEAT:

  • * NOT Concentrated*
  • LOTS of Water
  • LITTLE Sodium
31
Q

Integrative Response: DECREASED Core Temp

A

(Tb

32
Q

Fever

A

DEFINITION:
- A CONTROLLED INCR in Body Temp

IMPLICATION:
- SET POINT INCR: Body Temp is only doing what Hypothalamus DIRECTS it to do!!!

33
Q

Making a Fever- STEP ONE

A

1) Secretions of ENDOTOXINS
2) IMMUNE CELLS activated by “Bugs” release CYTOKINES

Endotoxins and Cytokines lead to the production of PROSTAGLANDIN E2 (Major Player)!!!!!!!!!!!!!!!
- EP3 receptor

** The Production of Prostaglandin E2 leads to an INCREASE HYPOTHALAMIC SET POINT for Temp (Tb

34
Q

Making a Fever- STEP TWO

A

Tb

35
Q

Making a Fever- STEP THREE

A

Tb = Tset point

“COMFORT” - in a relative Sense

36
Q

Making a Fever- STEP FOUR

A

1) The Bud is Vanquished : NO ENDOTOXINS
2) No more Activation of Immune Systems

** These lead to the HYPOTHALAMIC Set Point returning to NORMAL

Tb > Tset point

37
Q

Making a Fever- STEP FIVE

A

( Tb > Tset point)

1) DECREASE Heat PRODUCTION
- Apathy/ Inertia
- Anorexia

2) INCREASE Heat LOSS:
a) Conduction/ Convection
b) EHL (Sweat)
c) Insensible Heat Loss (Pant)

38
Q

Making a Fever- THE END

A

Tb = Tset point

The REAL COMFORT!!!!!!!

39
Q

Hyper and Hypothermia

A

DEFINITION:
- UNCONTROLLED Changes in BODY TEMPERATURE

IMPLICAITONS

  • Set Point remains NORMAL
  • Environmental Stresses EXCEED Body’s ABILITY to REGULATE TEMP
  • At Extremes: Hypothalamic Regulation MAY BE LOST!
40
Q

Thermoregulation- Case Study about Hypothalamic Tumor

A

HYPOTHALAMIC TUMOR:
- Abolishes the ABILITY to THERMOREGULATE

  • Although a Fever is MORE COMMONLY SEEN with Tumors, this tumor has also DESTROYED her ability to SECRETE TSH, so NO Thyroxin is being Produced.
  • Thus, her BASAL METABOLIC RATE is VERY LOW and the HEAT PRODUCTION is LOW!!!

Neuroscience I (18 decks)

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