1 - Hypothalamus and Pituitary

Question 1

Key functions of hypothalamus?

Answer 1

HEAL

Homeostasis

Endocrine (+ pituitary)

Autonomic (sympathetics/parasympathetics)

Limbic (behavior)

Question 2

Embryology development of Pituitary

Answer 2

Two Sources:

Anterior Pituitary - ectodermal cells of developing pharynx (Rathke’s Pouch)

Posterior Pituitary - Prosencephalon (diencephalon)

Question 3

How does the mature pituitary reflect is origin?

Answer 3

Anterior Pituitary - Glandular cells secrete hormones into circulation through vascular portal system (via median eminence)

Posterior Pituitary - Axon terminals of hypothalamic neurons release hormoes into circulation

Question 4

What marks the superior border with hypothalamus and thalamus?

What can help identify the posterior border of the hypothalamus?

What can help mark the lateral border?

Answer 4

Hypothalamic Sulcus (groove)

Mammillary Bodies

Internal capsule

Question 5

Tuber Cinereum

Answer 5

Bulge between optic chiasm and mammillary bodies (marks ventral border)

Infundibulum arises from this structure

“sort of the area between the balls and the infundibulum”

Question 6

Medial Forebrain Bundle

Path

Function

Answer 6

Path: Runs from basal forebrain to brainstem tegmentum, connects hypothalamus to forebrain and brainstem tegmentim

Functions: Carries axons from monoaminergic nuclei in brainstem to cerebrum

**runs through lateral zone**

Question 7

Major Nuclei: Feeding and Satiety

Lateral Hypothalamic Area

Ventromedial Nucleus

Answer 7

Lateral Hypothalamic Area - Feeding Center

- Electrical simulation in animals increases feeding; lesions reduce feeding

Ventromedial Nucleus - Satiety Center

• Electrical stimulation in animals decrease feeding; lesions increase feeding

Question 8

Major Nuclei: Sleep and Circadian Rhythms

Answer 8

Preoptic Area

• Telencephalon (all others from diencephalon)

- Ventrolateral Preoptic Area (VLPO) Regulates Sleep

Tuberomammillary Nucleus

• Projects to cerebral hemispheres; release histamine
• Helps maintain wakefullness

Suprachiasmatic Nucleus

- “Master Clock” for circadian rhythms

• Receives light input from retina

Question 9

Major Nuclei: Anterior Pituitary

Arcuate Nucleus (Ar)

Paraventricular Nucleus (PV)

Medial Preoptic Area

Answer 9

Project to Median Eminence

***Control hormon release from Anterior Pituitary***

Question 10

Major Nuclei: Posterior Pituitary

Suproptic Nucleus (SO)

Paraventricular Nucleus (PV)

Answer 10

Project to posterior pituitary

Release Oxytocin / Vasopressin

Question 11

Hormones of Posterior Pituitary?

Answer 11

Ocytocin: Milk ejection, uterine contractions, maternal behavior, bonding

Vasopressin (ADH): Stimular water retention in kidney to regulate plasma osmolarity

Question 12

Major Nuclei: Autonomic Control

Paraventricular (PV)

Dorsomedial (DM)

Lateral (L)

Posterior (Po)

Answer 12

Autonomic control by descending fivers

Medial forebrain buncle

Preganglionic parasympathetics nuclein in brainstem and sacral spinal cord

Preganglionic sympathetic in intermediolateral column of thoracolumbar spinal cord

Question 13

Major Nuclei: Memory

Mammillary Bodies (MB)

Input

Output

Lesions

Answer 13

Input: Receive input from hippocampal formation (via Fornix)

Output: Anterior thalamus (mammillothalmamic tract); anterior thalamus projects to cingulate gyrus

Lesions: Impair memory formation; ex. Korsakoff Syndrome - Thiamine (B1) Deficiency = Chronic alcohol abuse

Question 14

Major Nuclei: Thermoregulation

Divisions of nervous system?

Locations key for function?

Lesions?

Answer 14

Divisions

Autonomic: Sweating, altered blood flow

Somatic: Shivering, panting

Locations

Anterior - Heat dissipation

Posterior - Heat conversion

Lesions

Hypothermia, hyperthermia, fluctuation body temperature

Question 15

Input to Hypothalamus: Visceral Sensory

Answer 15

From spinal cord, solitary nucleus, periaqueductal grey, anterolateral system; mostly via medial forebrain bundle

Question 16

Input to Hypothalamus: Blood

Answer 16

Temperature, osmolarity, glucose/other metabolites, homrones

Circumventricular organs, anterior pituitary median eminence (circulating hormones)

***These structures MUST be outside Blood/Brain barrier to regulate this function***

Question 17

Input to Hypothalamus: Retina

Answer 17

to Suprachiasmatic Nucleus

Question 18

Input to Hypothalamus: Prefrontal and Limbic Cortex, Hippocampus, Amygdala

Answer 18

Integration of emotion with autonomic function and homeostatic pathways, memory function

Question 19

Output from Hypothalamus: Preganglionic autonomic neurons

Answer 19

Through medial forebrain bundle

Direct and indirect (relays in PAG, reticular formation) control parasympathetic and sypathetic preganglionic fibers

Question 20

Output from Hypothalamus: Prefrontal and Limbic Cortex, Hippocampus (indirect) and Amygdala

Answer 20

Intregration of emotion with autonomic function and homesostatic pathways, memory formation

Question 21

Output from Hypothalamus: Anterior and Posterior Pituitary

Answer 21

Endocrine regulation

Question 22

Hormones:

Suprotic Nucleus, Paraventricular Nucleus to posterior pituitary?

Arcuate Nucleus, Paraventricular nucleus, preoptic nucleus, Periventricular nucleus?

Answer 22

Oxytocin

Vasopressin

Release of regulating factors into portal system via medial eminence

Question 23

Hypothalamic Pituitary Adrenal (HPA) Axis System

Hormone Release Control?

Hormon Release Location?

Downstream Effects?

Feedback

Answer 23

Hormone Release: Preoptic, Supraoptic, Paraventricular Nuclei release Corticotrophin Releasing Hormon (CRH)

Location: Corticotropin (ACTH) releasef from Anterior Pituitary (+ by CRH)

Downstream: ACTH stimulates release of Cortisol from Adrenal Cortex

Feedback: Negative Feedback to Ant. Pituitary and Hypothalamus regulates CRH/ATCH

Question 24

How/When is the HPA Axis activated?

Chronic over activation?

Answer 24

Response to stress, emotion (input from amygdala)

Chronic over activation can lead to stress, depression, and neuronal atrophy in hippocampus

Question 25

Clinical: Pituitary Adenomas

Answer 25

Benign, slow growing

Endocrine disturbance

Non-secreting may grow large, and cause symptoms

Question 26

Clinical: Panhypopituitarism

Answer 26

Deficiency of ALL pituitary hormones

Causes: Tumors, treatment of tumors (tissue loss), infections, autoimmune disorders

**Requires hormone replacement**