hypothal 3 Flashcards
fever
a regulated increase in body temperature
Pyrogen
fever producing agents which increase the “set-point” of the thermoregulatory system
Fever-producing agents
(via increased PGE2 production in the OVLT)
increase the “set point”–>
creates a relative decrease in local brain temperature –>
leads to a decrease in firing rate of the thermoreceptors in the POAH.
This decrease in POAH neuron activity leads to
activation of thermogenic responses (vasoconstriction, shivering etc.) identical to an actual fall in body temperature.
Cytokines (IL-1, IL-6, TNF, interferon) released by immune cells act at a region of the hypothalamus called the _______.
OVLT (organumvasulosum of the lamina terminalis) that lacks a blood brain barrier.
The OVLT produces
PGE2, which diffuses to the adjacent POAH (preoptic anterior hypothalamus) and decreases the activity of the thermoreceptors.
This resets the hypothalamic temperature “set-point” to a higher level.
Thermoreceptors in the POAH generate action potentials at a frequency_____
proportional to the local temperature
An increase in local temperature increases the firing rate of thermoreceptors in POAH and induces_____
heat loss mechanisms.
Posterior hypothalamic neurons receives strong input from:
strong excitatory input from cutaneous cold receptors.
They do NOT directly monitor local brain temperature as POAH neurons do.
When stimulated, these neurons induce heat gain mechanisms.
Circadian rhythms are ____.
endogenous rhythms in biological parameters that are approximately 24 hours long
The primary circadian clock is located in the _____.
suprachiasmatic nucleus of the anterior hypothalamus
The SCN gets direct innervation from the ____: this provides information about _____
retina
the light/dark cycle and allows the endogenous rhythms to become trained to the light/dark cycle.
the SCN can generate these rhythms in the absence of a 24 hour light/dark cycle! However, the endogenous cycle runs slightly shorter than 24 hours. If you lesion the SCN, you obliterate the endogenous rhythm.
the SCN can generate these rhythms in the absence of a 24 hour light/dark cycle! However, the endogenous cycle runs slightly shorter than 24 hours. If you lesion the SCN, you obliterate the endogenous rhythm.
Circadian rhythms are not just concerned with the sleep/wake cycle. Other physiological parameters run on endogenous rhythms, including:
- Body temperature
- Water and food intake
- Activity
The hypothalamus is responsible for initiating the coordinated autonomic and behavioral responses that constitute emotional expression, but higher CNS areas are responsible for modulating emotional expression such that it is appropriate for the situation.
The hypothalamus is responsible for initiating the coordinated autonomic and behavioral responses that constitute emotional expression, but higher CNS areas are responsible for modulating emotional expression such that it is appropriate for the situation.
Hypothalamic control of emotional expression involves integration of ____
somatic, autonomic, and endocrine responses
Integrated HT components:
- Somatic reactions
- ANS reactions:
- Endocrine reactions:
Somatic reactions:
- escape
- fighting
- biting
- hissing
- facial expressions
ANS reactions
- blushing
- dry mouth
- sweating
- GI reactions
- fainting
Endocrine reactions:
activation of adrenal cortex and medulla
Rage/aggressive behavior elicited by:
- Lesions of the medial HT (ventromedial nucleus)
2. Stimulation of the dorsomedial nucleus
Suppression of aggressive behavior or placid behavior:
Lesions of lateral hypothalamic area and mammillary region
Sham rage:
a phenomenon observed when the hypothalamus is disconnected from higher brain areas, but the hypothalamic connections to the brainstem and spinal cord remain in tact.
sham rage produces
animals that are extremely aggressive and irritable.
The response is different from the response of an intact animal to pain or irritation in that the response of sham rage is short-lived and poorly directed.
shame rage occurs in response to
inappropriate stimuli, such as a soft touch
______ from the brainstem abolishes sham rage, indicating that ________.
Disconnecting the HT
the hypothalamus can initiate the somatic and autonomic reactions to sensory input even in the absence of cortical inputs
