Lecture 8 Block 3

Question 1

explain the bottom up modulation of endocrine system by brainstem, hypothalamus and CVO

Answer 1

physiological stress causes homeostatic imbalance, pain, and inflammation. these stress stimuli may be sensed by peripheral sensory system and sent to brainstem and hypothalamus. sensors in CVO and hypothalamus may also sense the imbalance and relay info to brainstem and hypothalamus which directly modulate HPA and SAM systems

Question 2

explain the top down modulation of endocrine system by limbic forebrain

Answer 2

psychological stress is perceived as a threat to homeostasis by the forebrain limbic system which in turn modulates hypothalamus. amygdala is required for learned emotional response. hippocampus is required for context learning and context-dependence of learned fear response. it is required for recently acquired memory about context and context-dependence. anterior cingulate cortex is required for remote context learning

Question 3

what is the hippocampus’ influence on HPA axis

Answer 3

inhibitory

Question 4

how is the hippocampus inhibitory on HPA axis

Answer 4

• stimulation decreases glucocorticoid secretion

- hippocampal damage increases stress-induced and basal glucocorticoid secretion

Question 5

how does the hippocampus influence autonomic system

Answer 5

lowers heart rate, respiratory rate and BP

Question 6

what is the amygdala’s influence on HPA axis and ANS

Answer 6

excitatory

Question 7

what does medial and basolateral nucleus of amygdala respond to

Answer 7

psychological stressors but not homeostatic stressors

Question 8

what is the central nucleus of the amygdala important for

Answer 8

autonomic responses to homeostasis stressors

Question 9

what does dorsal anterior cingulate cortex inhibit

Answer 9

HPA axis and bases for parasympathetic activity

Question 10

what does ventral anterior cingulate cortex activate

Answer 10

HPA axis and bases for sympathetic activity

Question 11

what do hippocampal lesions prevent

Answer 11

learned HPA/ANS responses to learned taste aversion and learned fear to context

Question 12

what do amygdala lesions prevent

Answer 12

HAP/ANS responses to all learned fear

Question 13

explain the integration of bottom up and top down modulations at hypothalamus

Answer 13

hypothalamus receives input from and is modulated by brainstem and the limbic system. limbic influences of the HPA and ANS responses are mediated by hypothalamus

Question 14

where are steroid hormone receptors expressed

Answer 14

the limbic system

Question 15

how do CRH and glucocorticoids have excitatory influences on hippocampus

Answer 15

• CRH increases pyramidal neuron firing rate
• cortisol increases burst firing in hippocampal neurons
• corticosterone lowers seizure threshold

Question 16

how are hippocampal GR involved in HPA negative feedback control

Answer 16

in the forebrain GR knockout mouse, GR expression is ablated in forebrain, but is normal in other brain regions including paraventricular nucleus of hypothalamus and anterior pituitary gland. when the GR receptor level is diminished baseline corticosterone is elevated. thus, corticosteroids activate hippocampus and hippocampus in turn inhibits HPA axis to down regulate glucocorticoid levels