hypothalamus Flashcards
the hypothalamus is involved in
functions that require the integration of somatic, autonomic, and endocrine mechanisms with motivated behavior expression
- feeding
- fight
- flight
- reproduction
the hypothalamus is anatomically linked to (projects and receives)
- reticular formation
- limbic system - emotion, memory
- pituitary gland - master gland of endocrine system
anatomical boundaries of hypothalamus
caudal: mammillary body
dorsal: hypothalamic sulcus
rostral: lamina terminalis
inferior: optic chiasm, pituitary stalk
lateral: internal capsule
divisions of the hypothalamus
- supraoptic/anterior - above optic chiasm
- tuberal/middle - above stalk of pituitary
- mammillary/posterior - above mammillary bodies
hypothalamic efferents
- medial forebrain bundle (MFB)
- dorsal longitudinal fasciculus (DLF)
- hypothalamo-hypophyseal tract
medial forebrain bundle (MFB)
- not a typical tract
- has variety of cells, fibers, etc.
- go to hypothalamus
dorsal longitudinal fasciculus (DLF)
- goes from hypothalamus to dorsal nucleus of vagus
- controls parasympathetic part of NS
hypothalamo-hypophyseal tract
- unique neurons
- synthesize proteins/hormones that are released into blood vessels
- 2 nuclei (supraoptic and paraventricular)
tubero-infundibular tract
- from hypothalamus
- neurosecretory cells secrete hormones
- released into blood vessels
afferents to hypothalamus
- reticular formation via MFB
- limbic pathways (fornix and amygdalar pathways)
- monoaminergic pathways
functions of anterior hypothalamus
- thermoregulation
- water balance
- circadian rhythms
- maternal behavior
- sleep
thermoregulation by hypothalamus
- somatic NS (shivering)
- autonomic NS (sweating, vasomotion)
- behavior
- thermoreceptor neurons
mechanism of fever
- body temp increases
- set-point is raised to a higher temperature
- we shiver because the muscles shiver to increase heat of the body
infection
- macrophage consumes bacteria
- release interleukins (1 and 6) to hypothalamus
- hypothalamus uses phospholipids to create arachidonic acid
- arachidonic acid forms prostaglandin by COX (inflammation)
- aspirin and NSAIDs inhibit COX (inhibits inflammatory and pain)
water balance
in high heat you lose water so the responses:
- endocrine (ADH)
- behavior (water drinking)
circadian rhythms
- generated by suprachiasmatic nucleus (SCN)
- SCN receives collaterals from optic tract (retino-hypothalamic fibers)
- lesions of SCN disrupt 24-hour temperature, sleep, and endocrine cycles
where is the suprachiasmatic nucleus
- above the optic chiasm
functions of tuberal hypothalamus
- control plasm hormone levels
- feeding behavior
- sexual behavior
- aggressive behavior
feeding behavior
concept of feeding center (LH) and satiety center (VMH)
- lesions of LH induce anorexia
- lesions of VMH (ventromedial nucelus of hypothalamus) induce obesity
important nuclei of feeding behavior
- arcuate nucleus
- paraventricular nucleus
sensing metabolic state (hormones?)
- ghrelin-appetite promoting (GI tract)
- insulin (pancreas)
- leptin (adipose tissue)
feeding behavior is controlled by
- behavior
- autonomic NS (salivary secretion, gastric secretion)
- metabolic need
aggressive behavior includes
- attack behavior
- defense behavior
- flight behavior
attack behavior is evoked by
stimulation of lateral hypothalamus
defense behavior is evoked by
stimulation of ventral medial hypothalamus
flight behavior is evoked by
stimulation of dorsal hypothalamus
sexual behavior
- VMN has estrogen receptors
- VMN important in female sexual behavior
- sexually dimorphic nucleus in POA (pre-optic area)
signs and symptoms of a hypothalamic lesion:
- anterior pituitary dysfunction
- posterior pituitary dysfunction
- hypothalamic dysfunction
- visual symptoms
anterior pituitary dysfunction
- gonad dysfunction
- thyroid
- cortisol
- growth hormone
posterior pituitary dysfunction
- diabetes insipidus
hypothalamic dysfunction
- polyphagia or starvation
- impaired temperature regulation
- impaired autonomic function
horner’s syndrome
- miosis: reduced diameter of pupil
- ptosis: drooping of eye
- anhydrosis: lack of sweat
