Thermoregulation Flashcards
Describe cutaneous thermoreceptors.
- Bimodal- temp and touch sensitive
- warm or cold sensitive
- usualy 10x as many cold sensitive ones
- tells about environment conditions
What is the importance of thermoreceptors in the gut?
- To sense threats to maintance of core tempreature
Where are thermoreceptors located in the brain and what do they do?
- Pre-optic and superoptic regions of hypothalamus
- Neuron cell bodies sensitive to chagnes in temp, 3x as many warm sensitive ones
- relay info to other hypothalamus areas
- Detect core temp
What does the hypothalamus do regarding body temperature control?
- determines set point
- recieves info about current temp
- decides if anything needs to be done about #2
How is set point determined?
Action potentials from thermoreceptors match the AP’s from neurons that make set point
How does set point flucuate throughout the day?
- Decreases with sleep and increases with exercise
If the anterior hypothalamus is active what is happening with regards to heat/cooling?
- The anterior hypothalamus responds to heat so it responds to an increase in core temp or environment temp.
- Begins heat loss behaviors
If the posterior hypothalamus is active what is happening in the body?
- It is active in response to cooling so a decrease in environment temp or core temp
- Initiates heat production behaviors
What are four mechanisms of heat production? (Effectors)
- ANS specifically sympathetic ns
- Endocrine system- thyroxin and epinephrine
- Muscles
- Non shivering thermogenesis-Brown aidpose
Describe how shivering works.
- Shivering activates dorsomedial posteiro hypothalamus and increases motorneuron excitation
- It also increases voluntary activity in the cortex
What innervates brown fat and what hormone stimulates it?
Sympathetic nervous system and epinephrine stimulates it
What are the two kinds of evaporatiave heat loss?
- Insensible respiratory
- Sweating Controlled
What is convection?
Movement of molecules away from contact, air heating and rising
What is conduction?
Transfer of heat between objects in physical contact
What is radiation heat loss?
Infrared radiation transferring heat between 2 objects not in physical contact
What kind of innervation and receptor are part of sweating?
- Sympathetic cholinergic with acetylcholine as the NT
- Muscarinic receptor
How is sweat produced?
- filtration of serum including ions
- NaCl moves into sweat
- As fluid travels up to skin surface water and sodium are reabosorbed into the duct
What is meant by low flow rate of sweat?
- It is concentrated sweat
- a lot of water is reabsorbed but not sodium
What is meant by high flow rate?
- Little water is re absorbed so the sweat is very dilute
What happens with acclimation in sweating?
- little sodium is put out due to aldosterone producing dilute sweat
How should your body respond to the set point being higher than actual body temp?
- Decrease heat loss so blood moves away from the skin
- Pale
- Decrease evaporative heat loss
- Dry skin
- Increase heat production
- Shivering
- non shivering thermogenesis
What is the major player in a fever?
Prostaglandin E2
What is happening during a fever?
- Increased heat production such as shivering and non chivering thermogenesis
- Decreased heat loss moving blood away from skin and decreased evaporative heat loss
- Same as when your body is cold, feels subjectively cold
- Body temp is less than the set point- set point was increased and even though you are hotter than normal you feel cold bc you are still below set point
What happens when a fever breaks?
No more activation of the immune system the hypothalamic set point goes back to normal
- Now your body temp is above set point-feels hot
- Decrease heat production
- apathy, less movement, anorexia
- Increase heat loss
- conduction convection EHL (sweat) Insensible heat loss
Compare contrast hyperthermia and fever:
- core temp
- Set point
- Active thermoreg response
- Signs
- Subjective
- Cause
Fever:
- Increased core temp
- Increased set point
- Produce heat
- Pallor, shivering, behave cold
- Patient describes feeling cold
- Infectioius agen producing inflammatory mediators increasing set point
Hyperthermia:
- Increased core temp
- Normal set point
- Heat loss
- Flushed skin and sweating (until too dehydrated), behave hot
- Describes being hot
- Increased heat production and decreased ability to eliminate heat, dehydration
What plays a major role in Autonomic regualtion of temp? What is the outflow?
- Dorsal longitudidnal fasciculus and within that the Paraventricular Nuclei
- Outflow DLF to:
- Dorsal motor nucleus of vagus
- Nucleus ambiguous
- Parasympathetic and sympathetic neurons in spinal cord
What does medial forebrain bundle do?
- Provides substantial input to hypothalamus especially from nucleus tractus solitaries
- outflow to same nuclei as DLF
What does amammillotegmental tract do?
smaller than MFB and DLF
Mammillary bodies to autonomic nuclei
