Hypothalamus Flashcards
Diencephalon is composed of:
Pituitary
Hypothalamus
Thalamus
Epithalamus
Name some of the functions of hypothalamus
Thirst
Hunger
Sleep
Thermoregulation
Stress
Blood pressure
Sexual behavior
Lactation
Body growth
Salt balance
Sexual maturation
Gametogenesis
Pair bonding
Arousal
Learning
Heart rate
Cellular metabolism
Digestion
Respiration
Aggression
Fear
Parental behaviors
& More
Transections above the hypothalamus caused what? And what conclusions did the results of the experiment
Sham Rage. Non-threatening stimuli resulted in
-Biting
- Clawing
- Arching the back
- Piloerection
- Increased respiration and heartbeat
Led to the idea that the hypothalamus serves an
integrated role in coordinating emotional behavior and
low-level, autonomic physiology.
3 Functional modes of hypothalamus
1) neuroendocrine
2) autonomic
3) limbic
Water Balance Nuclei
Neuroendocrine areas of hypothalamus
Mostly preoptic/supraoptic
regions
- Peripheral targets
- Signals go through pituitary
Name 2 neuroendocrine pathways
Parvocellular and Magnocellular
Parvocellular
is indirect:
-Parvocellular neurons secrete releasing
hormones into the pituitary’s portal
vessels
-Portal vessels transport releasing
hormones into the adenohypophysis
-Endocrine cells in the pituitary then
secrete hormones into the general
circulation, where they act on targets
throughout the body
Parvocellular Hormones
Magnocellular
is direct!
Magnocellular neurons project via the infundibulum into the posterior
hypothalamus (neurohypophysis) and
secrete hormones directly into the general
circulation
The posterior pituitary is mostly lacking in
cell bodies
Magnocellular Hormones
By which mechanism is osmolarity of blood maintined?
A negative feedback loop
Explain hypothalamic role of osmotic balance
-Supraoptic nucleus (SON) of hypothalamus releases ADH
into bloodstream
-Kidneys respond to ADH by concentrating urine,
helping to retain water in blood
-Water deprivation increases ADH release
-If blood osmolarity increases, the circumventricular
organs (OVLT and SFO) sense the change through
intrinsically osmosensitive neurons
-Activation of SON by OVLT and SFO increases
ADH secretion
How do the circumventricular organs sense blood osmotic balance?
THE CIRCUMVENTRICULAR ORGANS LACK A BLOOD-BRAIN BARRIER
How does the hypothalamus function with autonomic system?
- Interactions with sympathetic and
parasympathetic neurons in
brainstem and spinal cord.
AUTONOMIC CONNECTIONS WITH THE HYPOTHALAMUS (direct)
Direct, reciprocal projections:
Originate largely in PVN and LH
Travel primarily via the hypothalamospinal and
hypothalamomedullary tracts, which both begin within
the medial forebrain bundle
Target general visceral efferent (GVE) motor nuclei in
medulla (cranial nuclei VII, IX, X)
Also target preganglionic sympathetic neurons in
spinal cord
Control and/or detect salivation, heart rate,
respiration, blood pressure, visceral functions, etc.
indirect
AUTONOMIC CONNECTIONS WITH THE HYPOTHALAMUS (indirect)
Dorsal longitudinal fasciculus and mammilotegmental
tract innervate the periaqueductal grey
Descending projections from PAG innervate brainstem
and spinal autonomic nuclei
(Minor) Some DLF axons also project directly to
brainstem nuclei and down the spinal cord
Papez Circuit
Mammilary bodies -> thalamus cingulate cortex -> entorhinal cortex -> hippocampus -> mammillary bodies (via fornix)
Basis for the original concept of the limbic system
Convergence of signals from hypothalamus and sensory cortex at cingulate proposed to mediate conscious experience of emotion
Now known to be important for memory: links behavior to motivation
