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NE Exam 3 > Hypothalamus > Flashcards

Hypothalamus Flashcards

1
Q

Describe the location and structure of the hypothalamus

A

Inferior to thalamus
Forms walls and floor of 3rd ventricle
Anatomically part of the diencephalon but functionally part of the limbic system

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2
Q

What are some functions of the hypothalamus?

A

Regulates basic drives (motivated goal-directed behaviors) as well as emotional or affective behavior
Regulator of homeostasis, ANS and endocrine function
Food intake/body weight, fluid and electrolyte balance, body temperature
Sexual and reproductive behavior
Sleep-wake cycles/circadian rhythms

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3
Q

What is the rostral/anterior boundary of the hypothalamus?

A

Optic chiasm

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4
Q

What is the caudal/posterior boundary of the hypothalamus?

A

Merges into tegmentum and PAG (midbrain)

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5
Q

What do the mammillary bodies form?

A

Posterior part of the hypothalamus and are adjacent to the cerebral peduncles

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6
Q

What is the tuber cinereum?

A

Small swelling between the mammillary bodies and the optic chiasm + tract

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7
Q

What is the median eminence?

A

Arises from the tuber cinereum and narrows into the infundibulum
Attaches to pituitary gland

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8
Q

What are the hypothalamic zones?

A

Divided into functional areas of nuclei along the lateral -> medial and anterior -> posterior axes
Columns of the fornix cut through the hypothalamus en route to the mammillary bodies -> divide hypothalamus into lateral and medial zones

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9
Q

What does the lateral zone contain?

A

Scattered neurons interspersed among major bundles of fibers, which carry two-way traffic through the hypothalamus, rostrally toward the forebrain and caudally toward the brainstem

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10
Q

What does the medial zone contain?

A

The majority of hypothalamic nuclei

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11
Q

What are the hypothalamic areas?

A

Three functional areas exist within the medial zone along the AP axis
Includes the anterior, middle (tuberal) and posterior area

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12
Q

Where is the anterior area of the hypothalamus and what nuclei does it contain?

A

Superior to optic chiasm

Contains the preoptic, suprachiasmatic, supraoptic (medial and lateral), pareventricular and anterior nuclei

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13
Q

Where is the middle (tuberal) area and which nuclei does it contain?

A

Superior to and including the tuber cinereum

Contains the dorsomedial, ventromedial and arcuate nuclei

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14
Q

Where is the posterior area and which nuclei does it contain?

A

Superior to and including the mammillary bodies

Contains the posterior nucleus and mammillary bodies

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15
Q

Describe the nucleus of the lateral zone

A

Diffusely arranged neurons with few named nuclei
Contains the median forebrain bundle
Damage results in a decrease in feeding behavior with a resultant weight loss

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16
Q

Describe the supraoptic/pareventricular nucleus of the anterior area

A 
Contain oxytocin (PVN) and ADH (SON) —> posterior pituitary 
Lesions result in diabetes insipidus (DI), increased H2O intake and increased urination
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17
Q

Describe the suprachiasmatic nucleus of the anterior area

A

Receives input and is involved in circadian rhythms

Damage to this area may modify or abolish these rhythms

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18
Q

Describe the anterior nucleus of the anterior area

A

Range of visceral/somatic functions

Temperature regulation

19
Q

Describe the ventromedial nucleus of the middle (tuberal) area

A

Satiety center

Lesions cause excessive eating and abnormal weight gain

20
Q

Describe the dorsomedial nucleus of the middle area

A

Subserves emotional behavior
Stimulation causes sham rage
Destruction results in decreased aggression and feeding

21
Q

What is the function of the arcuate nucleus of the middle area?

A

Secretes releasing/inhibiting hormones

22
Q

Describe the medial mammillary nucleus of the posterior area

A

Afferents from the hippocampus via the fornix
Efferents to the thalamus and brainstem
Lesions result in an inability to process short term events into long term memory

23
Q

What provides blood supply to the hypothalamus?

A

Served by small perforating arteries from the circle of Willis

24
Q

What does the anteromedial group of the circle of Willis supply?

A

Branches from anterior communicating and anterior cerebral arteries (A1)
Serve preoptic area and supraoptic region, septal nuclei and rostral portions of lateral hypothalamic area

25
Q

What does the posteromedial group of the circle of Willis supply?

A

Perforating arteries from the posterior communicating and posterior cerebral artery (P1)
Rostral portion of posterior communicating —> tuberal region
Caudal parts —> mammillary region

26
Q

Which fibers compose the hypothalamic afferents?

A

Fornix, stria terminalis and ventral amydalofugal fibers, corticohypothalamic input and retinohypothalamic fibers

27
Q

Describe the afferent info of the fornix

A

Afferent info from hippocampal fibers -> mammillary bodies

28
Q

Stria terminalis and ventral amygdalofugal fibers send afferents from the amygdala to what?

A

Hypothalamus

29
Q

Describe the corticohypothalamic input

A

From orbitofrontal and cingulate areas, multiple association areas, frontal lobe —> lateral zone

30
Q

Retinohypothalamic fibers target which structure?

A

SCN

31
Q

Which fibers make up the efferents from the hypothalamus?

A

Medial forebrain bundle (MFB) and dorsal longitudinal fasciculus (DLF)
Descending fibers to PAG and RF
Ascending fibers including hypothalamocortical, mammillothalamic, lateral zone projections

32
Q

The medial forebrain bundle (MFB) and dorsal longitudinal fasciculus (DLF) relay two way information to and from what?

A

The hypothalamus (efferents)

33
Q

Describe the descending efferent fibers from the hypothalamus

A

To PAG and RF
Made up of hypothalamomedullary and hypothalamospinal fibers coming from medial zone and mammillary bodies
Enables hypothalamus to influence emotional aspects of behavior

34
Q

Hypothalamocortical fibers ascend to which structures?

A

Forebrain, target frontal lobe

35
Q

Mamillothalamic tract projects to what?

A

Anterior nucleus of thalamus —> thalamic nuclei projects to frontal lobe

36
Q

The lateral zone projects to what?

A

DM nucleus of the thalamus —> thalamic nuclei projects to frontal lobe

37
Q

Which two tracts participate in hypophyseal interactions?

A

Supraopticohypophysial tract and tuberofundibular tract

38
Q

What is the supraopticohypophysial tract?

A

Made of axons of neurons in SON and PVN
Prodices oxytocin and ADH —> posterior pituitary
Stored in Herring bodies and released into capillary plexus of posterior pituitary

39
Q

What is the tuberoinfundibular tract?

A

Input from neurons located in the periventricular zone, PVN and others
Convey releasing hormones to median eminence and infundibulum

40
Q

What role does the anterior area of the hypothalamus play in regulating the ANS?

A

Activates parasympathetic activity
Efferents brainstem (CN III, VII, IX and X) parasympathetic neurons
Spinal (S1-4) neurons

41
Q

What role does the posterior area of the hypothalamus play in ANS regulation?

A

Activates sympathetic activity

Efferent to sympathetic neurons in the lateral horn of spinal cord (T1-L2)

42
Q

Lesions in the anterolateral medulla disrupt what?

A

Hypothalamomedullary fibers —> sympathetic outflow to face and head (Horner’s syndrome) or body

43
Q

Describe the role of the suprachiasmatic nucleus in circadian rhythms

A

Receives direct input from the retina to mediate circadian rhythms, hormonal fluctuations second to light-dark cycles
Conveys circadian info to other hypothalamic regions, influencing sleep wake transitions
SCN activity opposes drive for sleep and is essential for timing of rest vs activity

44
Q

Describe the genetic role the SCN for regulating circadian rhythms

A

Cells of the SCN maintain 24 hour periodicity via transcription/translational control of circadian genes
Gene products indirectly control melatonin secretion (pineal gland)
-increases just prior to normal sleep onset
-internal indicator of circadian time and feedbacks to SCN

NE Exam 3 (16 decks)

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