Hypothalamus Flashcards

Question

Ghrelin

Answer 1

* Released by **stomach****** in blood * Highest just prior to a meal * Falls after eating * **Stimulates food intake** * May have role in meal initiation * signaling involves **gastric vagal afferent** * action on **ghrelin-sensitive arcuate neurons** * ↑ [Ghrelin] during diet/weight-loss episode ⟾ harder to maintain diet

Answer 2

Factors controlling hormonal secretion of anterior pituitary gland → HPA axis portal system → target. Influences activity of acidophils and basophils in anterior pituitary.

Answer 3

1. **_Control of parasympathetic system_** * **Descending hypothalamic fibers** → **preganglionic PNS neurons** in _cranial nerve nuclei (CN III, VII, IX, X)_ and _IML cell column_ (**S2-S4**) * Produces **parasympathetic and rest-and-digest responses** * Lesion ⟾ **deficit in PNS function** 2. **_Control of thermoregulation_** * Mediates dissipation of heat (**thermolysis**) * vasodilation and sweating * Lesion ⟾ **hyperthermia**

Answer 4

1. **Controls circadian rhythms** * **pacemaker** or biological clock (25 hr cycle) * receives **light info** from **retinal ganglion cells** via **retinohypothalamic tract** * adjusts rhythm to 24-hr cycle 2. **Modulates pineal gland function** * **inhibits** production of **melatonin** during the **day** * _light info_ from **hypothalamus** via _descending SNS fibers_ → **IML nucleus** → **superior cervical gnaglia** → **pineal gland** * lesion → **disruption of cyclic variations** of bodily functions * BP, hormone levels, body temp, sleep/wake

Answer 5

Contains **magnocellular neurosecretory neurons** ⟾ **projects directly to posterior pituitary** ⟾ releases **oxytocin or vasopressin** (ADH) into general circulation 1. **_Vasopressin-secreting neurons_** * **promotes water retention** * causes urine concentration by kidneys * lesion = **diabetes insipidus** 2. **_Oxytocin-secreting neurons_** * **promotes milk letdown** * **promotes contraction of uterine muscles**

Answer 6

Contains **parvocellular neurosecretory neurons** ⟾ projects to **median eminence/portal system** ⟾ **controls anterior pituitary function** 1. **Corticotropin-releasing-hormone neurons** (CRH-neurons) * ⊕ adrenocorticotropic hormone (ACTH) secretion * involved in stress/HPA-axis response 2. **Thyrotropin-releasing-hormone neurons** (TRH-neurons) * ⊕ thyroid-stimulating hormone (TSH) secretion 3. **Somatostatin-releasing neurons** * ⊖ growth hormone secretion * lesion = endocrine deficits

Answer 7

Involved in temperature regulation, behavioral courting, and mating displays. Contains medial and lateral preoptic nuclei. Substantia innominata and anterior commisure present at this level.

Answer 8

Found within **ventrolateral (anterior) preoptic hypothalamus**. * Contains **GABAergic neurons** which _inhibit_: * wake-promoting **orexinergic neurons** in _lateral hypothalamus_ * **histaminergic neurons** in _posterior hypothalamus_ * **cholinergic, serotonergic, and noradrenergic neurons** in _brainstem_ * Functions: * **inhibits wakefulness** * **promotes non-rapid eye movement sleep (non-REM)** * control global brain activity

Answer 9

Found in **anterior preoptic region** of hypothalamus. Functions: 1. **_Thermoregulation set-point:_** * contains set-point **temperature-sensitive neurons** * _regluates body temp_ * controls activity of heat conservation/dissipation hypothalamic centers * _fever triggered by pyrogens_ * prostaglandins (PGE2) act on medial preoptic neurons * resets set-point to higher temp * cytokines * NSAIDS ↓ fever by ⨂ COX * lesion ⟾ **hyperthermia** 2. **_Regulates release of gonadotrophic hormones & sexual behavior:_** * contains **gonadotropin-releasing neurons** (GnRH-neurons) * ⊕ LH and FSH from anterior pituitary * _sexually dimorphic_ * larger in males ⟾ continual release of GnRH * small in females ⟾ cyclical release of GnRH * lesion ⟾ **amenorrhea** and **impotence**

Answer 10

Present above the **preoptic region** of hypothalamus. Contains commissural fibers **innterconnecting anterior temporal lobes**.

Answer 11

Found within **substantia innominata** @ level of **anterior preoptic region** of hypothalamus. * **basal forebrain nucleus** * rich in **cholinergic neurons** * **wide projection to neocortex** * compromised in **Alzheimer's disease**

Answer 12

Inputs arise from 2 major regions: 1. **Forebrain projections** * associated with limbic areas 2. **Brainstem and spinal cord projections** * resonsible for conveying visceral and somatosensory information

Answer 13

3 major pathways involved in hypothalamic control of ANS: 1. Dorsal longitudinal fasciculus (DLF) 2. Mammillotegmental and mammilothalamic tracts 3. Medial forebrain bundle (MLF) Hypothalamo-hypophyseal tract is unidirectional.

Answer 14

**Hippocampal pyramidal neurons** → **mammillary bodies** and **septum** Part of **Papez's circuit** for memory consolidation.

Answer 15

**Mammillary bodies** → **anterior thalamic nucleus** Associated with **Papez's circuit** for memory consolidation.

Answer 16

Hypothalamus ↔ Amygdala

Answer 17

**Hypothalamus ↔ Brainstem & Forebrain** * Mix of **afferent and efferent** projections * Part of the **mesolimbic pathway** * contains **serotonergic, noradrenergic, dopaminergic projections** from **brainstem** * projects to **ventral striatum** and **accumbens nucleus** * Part of **reward system** * electrical stimulation of MFB produces intense pleasurable sensations

Answer 18

Contains axons from **paraventricular and supraoptic nuclei** → **posterior pituitary gland**.

Answer 19

Carries light information from **retinal ganglion cells** → **suprachiasmic nucleus** of hypothalamus.

Answer 20

1. **Contains afferent hypothalamic fibers** * carries visceral and taste sensation * inputs relayed to hypothalamus via solitary and parabrachial nuclei 2. **Contains efferent hypothalamic fibers innervating:** 1. **preganglionic parasympathetic neurons** in **brainstem** and **spinal cord** (S2-S4) * dorsal motor nucleus of X * inferior and superior salivatory nuclei * Edinger-Westphal nucleus 2. **preganglionic sympathetic neurons** in **spinal cord** * intermediolateral nucleus (T1-L2) * lesion of descending fibers in lateral medulla ⟾ Horner's syndrome 3. **autonomic regulatory centers** in **medulla** * respiration, HR, BP 4. **periaqueductal gray** (PAG) * pain modulation

Answer 21

There are various **reciprocal connections** between **hypothalamus** ↔ **cortical regions** including: ventromedial prefrontal cortex cingulate cortex insula

Answer 22

**Hypophyseal portal system** **Hypothalamus ↔ pituitary gland** Allows **endocrine signaling** between structures. _Pituitary gland supplied by 2 arteries:_ 1. **Superior hypophyseal artery** * forms **primary portal plexus** * penetrates median eminence and infundibulum 2. **Inferior hypophyseal artery** * forms **capillary network within posterior pituitary** Venous drainage via **hypophyseal veins**.

Answer 23

**Diurnal fluctuation of body temp from 93.2 → 107 °F.** * **Daytime** * hypothalamic thermostat **set point high** * **stores heat in body tissues** * **reduces need for cooling** by evaporative water loss * **Nightime** * thermostat **set point low** * **releases excess heat** absorbed during the day * body temp cools by several degrees * **reduces energy needed to maintain body temp** * prepares camel for following day by starting at abnormally low temp * **Carotid rete system** * protects brain from large ↑ in body temp * arterial blood precooled by passing through rete of thin-walled arteries * embedded in cavernous sinus * cooled by venous blood returning from nose * **Mechanisms to maintain fluid balance** * ability to excrete highly concentrated urine

Answer 24

* Don't drink water * Live on seeds and dry plant material * **Depends mostly on metabolic water from cellular respiration** * **Use behavioral habits & physiological features that conserve water** * nocturnal life * efficient kidney function * extremely hypoerosmotic urine * related to length of LoH and high [ADH] * low fecal water content * lower evaporative water loss * nasal passage as countercurrent heat exchanger * dry food stored in burrows absorps moisture lost in breathing

Answer 25

* Hibernates for 7-8 months * Rewarms body to normal temp every 2-3 weeks * uses 85-95% of fat stores * **Hyperphagy** for 4 months before hibernation * increase adipose stores * doubles body weight * **hypothalamic circuits regulating body weight become uncoupled or insensitive to signals from adipose tissue** * **Hibernation starts** → _temp set point from 98.6 to 30 °F_ * temp continuously regulated with **± metabolic rate** to ∆ body temp to ambient temp * **⨂ SNS** → ↓ shivering and vasoconstriction * **Hibernation ends** → _rewarming_ * **⊕ SNS** → brown adipose tissue → non-shivering thermogenesis * shivering is not started until body temp \> 60 °F

Answer 26

Functional interface between nervious and endocrine systems. BBB weak or non-existent. Can have specialized receptors or secretory propterties. * Receptor CVO's * area postrema * subfornical organ * organum vasculosum in hypothalamus * Secretory CVO's * median eminence * neurohypophysis * subcomissural organ * pineal gland

Answer 27

**Paraventricular, supraoptic, arcuate, and medial preoptic nuclei.** 1. **Neurosecretory control** ⟾ neurohypophysis * vasopressin and oxytocin from magnocellular neurons * **supraoptic and paraventricular nuclei** * travels to posterior pituitary * released into bloodstream 2. **Humoral control** ⟾ adenohypophysis * peptide hormones from parvocellular neurons * **paraventricular, arcuate, medial preoptic nuclei** * travels via portal system to anterior pituitary * stimulates/inhibits hormone release * ACTH * TSH * GH * Prolactin * LH & FSH

Answer 28

Major nuclei involved: 1. **Ventromedial nuclei (VMN)** ⟾ satiety or fullness center * lesion = extreme obesity * stimulation = stop eating 2. **Lateral hypothalamic area (LHA)** ⟾ feeding center * stimulation = eat even when not hungry 3. **Arcuate** and **Dorsomedial** nuclei **Lesion of LHA and VMN** ⟾ animal stops eating completely.

Answer 29

**Medial preoptic, anterior hypothalamic, and posterior hypothalamic nuclei.** Involves _descending hypothalamic fibers_ in **dorsal longitudinal fasciulus (DLF)** → _autonomic centers_ of **brainstem and spinal cord**. * **"set point" established** * feedback loop restores temp when actual ≠ desired * **↑ body temp:** * **anterior hypothalamic nucleus** → _thermolysis_ * vasodilation * sweating * increased respiratory rate * decreased metabolic rate * **↓ body temp**: * **posterior hypothalamus** → _thermogenesis_ * vasoconstriction * increased metabolic rate * shivering * decreased respiratory rate

Answer 30

**Medial preoptic, anterior hypothalamic, and posterior hypothalamic nuclei.** * Temp set-point in medial preoptic nucleus elevated * Normal, adaptive, nearly universal trait in vertebrates * acute phase response ⟾ coordinated response * autonomic * neuroendocrine * behavioral

Answer 31

**Subfornical organ** detects _plasma osmolality_. **Organum vasculosum** detects _angiotensin concentration_. Both CVOs _facilitate ADH release_ from **supraoptic** and **paraventricular nuclei**. Nuclei further regulated by _ascending signals_ from **carotid bodies** and **aortic arch receptors**. **Magnocellular neurons** influenced by _feedback systems_ that ∆ ADH secretion.

Answer 32

**Osmosensitive CVOs** in 3rd ventricle, lateral and anterior hypothalamus monitor water balance. Stimulates **thirst** and secretion of **ADH**. **ADH** released from **magnocellular neurons** of **supraoptic** and **paraventricular nuclei**. **↑ renal water reabsorption**

Answer 33

**Baroreceptor reflex** regulates BP. **Extrinsic baroreceptors** in _aortic arch and carotid sinus_. Sends info to **solitary nucleus of medulla** ⟾ **dorsal vagal nucleus** ⟾ ∆ HR. Solitary nucleus also sends **direct info to hypothalamus**. Hypothalamus **∆ baroreceptor reflex** via dorsal vagal nucleus.

Answer 34

Released by magnocellular neurons of supraoptic and paraventricular nuclei. 2 major effects: 1. **Initates milk letdown via lactation reflex** * Afferent limb → tactile, visual, or auditory stimuli * Efferent limb → contraction of myoepithelial cells of mammary glands * Reflex can be inhibited by anxiety 2. **Uterine contraction during parturition** * Afferent limb → pressure on cervix to hypothalamus * Efferent limb → oxytocin increases uterine contractions

Answer 35

**Parvocellular neurons** of **medial preoptic nucleus** release _GnRH_. **GnRH** stimulates _FSH and LH secretion_ by anterior pituitary. **FSH** promotes ovarian follicular growth. **LH & FSH** surge induces ovulation.

Answer 36

1. **Suprachiasmatic nucleus (SCN)** * controls circadian rhythm * receives input from retina 2. **Tuberomammillary nucleus** * histaminergic neurons * projects to cortex * important for alert state 3. **Ventrolateral preoptic area** * GABAergic neurons * projects to posterior hypothalamus * inhibits histaminergic neurons