Hypothalamus & Temperature Regulation

Question 1

The _____, a heavily myelinated fiber bundle, divides the lateral and medial hypothalamus

Answer 1

fornix

Question 2

Neural information from the hypothalamus to the autonomic and somatic nervous systems
travels in what 3 tracts:

Answer 2

A. Dorsal longitudinal fasciculus: to autonomic nuclei in the brainstem reticular system and
spinal cord

B. Medial forebrain bundle (mfb): to the brainstem reticular formation

C. Mammillotegmental tract: from the mammillary bodies to the midbrain reticular formation
(tegmentum).

Note: Pathways A and B also carry afferent information (visceral sensory) to the hypothalamus

Question 3

The preganglionic neurons of the sympathetic nervous system are located in the \_\_\_\_\_\_  of the thoracic and upper three lumbar segments of the
spinal cord (T1-L3)

Answer 3

intermediolateral column

Question 4

Hypothalamic neurons innervate upper motor neurons in the _________ which then project to the lower motor neurons that innervate skeletal muscle

Answer 4

brainstem reticular formation

Question 5

The hypothalamus directly secretes two hormones in the _______ lobe of the pituitary. It
also, by a distinct pathway, regulates the release of the _______hormones

Answer 5

posterior,

anterior pituitary

Question 6

The hormones of the posterior pituitary, vasopressin (also called antidiuretic hormone, ADH) and oxytocin are made by neurons in the _______ & _______

Answer 6

supraoptic (SON),
paraventricular nuclei (PVN)

Question 7

______ acts on the kidneys to increase water reabsorption and on the vascular smooth muscle cells to cause ______.

Answer 7

Vasopressin (ADH),

vasoconstriction

Question 8

_______ causes constriction of smooth muscle in the uterus and mammary glands and
thereby plays important roles in parturition and lactation

Answer 8

Oxytocin

Question 9

Receptors for both ______ & _______ are

found in the brain where they modulate behavior.

Answer 9

ADH,

Oxytocin

Question 10

The hypothalamus synthesizes and releases hormones into the hypothalamo-pituitary portal circulation that regulate the release of hormones from the _____of the anterior pituitary

Answer 10

glandular cells

Question 11

Several regions in the hypothalamus and preoptic area lack a blood-brain barrier. These areas are called _________.

Answer 11

circumventricular organs

Question 12

circumventricular organs include the _________ located at the front of the bottom of the third ventricle, the __________ located at the top of the third ventricle, the ________ located at the bottom of
the third ventricle, and the posterior pituitary

Answer 12

organum vasculosum of the lamina terminalis (OVLT),
subfornical organ (SFO),
median eminence

Question 13

angiotensin II produced by the peripheral renin-angiotensin system induces thirst by acting on neurons in the _______.

Answer 13

subfornical organ (SFO)

Question 14

Leptin (a hormone produced by white adipocytes) accesses hypothalamic neurons involved in regulation of food intake via the ________.

Answer 14

median eminence

Question 15

The hypothalamus contains neurons specialized for monitoring physiological parameters such as temperature, osmolality of the extracellular fluid, and glucose concentration called _________

Answer 15

Intrinsic sensory neurons

Question 16

________, a unique radial glial-like cell
that occupies the floor and ventrolateral walls of the third ventricle, regulate the transport of hormones and metabolites into the hypothalamus

Answer 16

tanycytes

Question 17

Neural Connections: The following reciprocal neural pathways carry both afferent and efferent
axons:
A._________ :connects hippocampus with mammillary bodies
B. _________: connects amygdala with the anterior and tuberal regions of hypothalamus
C. _________: connects hypothalamus with prefrontal cortex and septum
D. A fourth, strictly efferent neural pathway, the ________, carries information from the mammillary bodies of the hypothalamus to the anterior nucleus of the thalamus.

Answer 17

Fornix
Stria terminalis
Medial forebrain bundle (mfb)
mammillothalamic tract

Question 18

Light information from specialized retinal ganglion
cells that are intrinsically photosensitive travels directly to the _________ of the hypothalamus via the retinohypothalamic tract. This pathway is important for entraining our endogenous circadian rhythms to the environmental light/dark cycle.

Answer 18

suprachiasmatic nucleus

Question 19

Anterior hypothalamus: The Organum vasculosum of lamina terminalis (OVLT) and subfornical organ (SFO) monitor plasma osmolality for both ______& _____

Answer 19

thirst,

ADH release

Question 20

The Ventromedial nucleus has long been considered a
_______, because Stimulation of it inhibits the urge to
________.

Answer 20

‘satiety center’,

eat

Question 21

The ______ is considered a hunger or feeding center because Lesions result in anorexia, starvation, decreased responsivity to food and Stimulation induces food intake

Answer 21

Lateral hypothalamus

Question 22

______ nucleus monitors peripheral hormone levels

Answer 22

Arcuate

Question 23

A lesion to the Ventromedial nucleus can cause _____.

Answer 23

increased food intake,
marked obesity,
heightened sensitivity to food (both noxious and palatable)

Question 24

The hypothalamus serves as the master controller of
________,which is another important function in
the maintenance of homeostasis.

Answer 24

circadian rhythms

Question 25

The primary circadian clock in the body is located in the ______ of the hypothalamus

Answer 25

suprachiasmatic nucleus (SCN)

Question 26

The basal metabolic rate is influenced by ______ ; increases result in increased basal heat production
and decreases reduce heat production.

Answer 26

thyroxin

Question 27

Shivering is under control by the _______

Answer 27

somatic motor system

Question 28

In Non-shivering thermogenesis (NST). Infants and small-bodied cold-exposed mammals, both of which possess significant ______ , can also increase heat production by increasing the catabolic activity of this tissue

Answer 28

brown fat deposits

Question 29

There are specialized receptor neurons within the _____ that generate action potentials at a frequency proportional to the local brain temperature. The most prevalent type responds to increased temperature by
increasing its firing frequency. Decreased temperature slows the firing rate of these cells.

These central thermoreceptors also receive inhibitory synaptic input from ______ and excitatory input from ______.

Answer 29

preoptic anterior hypothalamus (POAH),
cutaneous cold receptors,
cutaneous warm receptors

Question 30

There are neurons in the posterior
hypothalamus that receive strong excitatory synaptic input from ______ and a relatively weak inhibitory input from________.. Excitation of these neurons induces heat gain mechanisms (shivering, vasoconstriction, seeking warm clothing or environment).

Answer 30

cutaneous cold receptors,

cutaneous warm receptors

Question 31

_____ is a regulated increase in body temperature (hyperthermia). It is induced by the actions of
________ which increase the “set-point” of the thermoregulatory system.

Answer 31

Fever,

pyrogens (fever producing agents)

Question 32

fever-producing agents all act ultimately by decreasing the activity of thermoreceptors in the ______.

Answer 32

preoptic anterior hypothalamus (POAH)

Question 33

When the fever-producing agent declines, the
_______ are released from inhibition and respond to the higher body temperature (the fever) by increasing their firing rate above normal. The patient feels hot and executes thermolytic maneuvers (sweating and vasodilating) until body temperature falls to
normal.

Answer 33

POAH thermoreceptors

Question 34

Due to their production by cells in the body, _______
have been termed endogenous pyrogens in contrast to exogenous pyrogens such as viral or
bacterial proteins that activate the immune system resulting in the production of cytokines. _______
has been clearly identified as one of the endogenous pyrogens.

Answer 34

cytokines,

IL-1

Question 35

IL-1 acts at a region in the hypothalamus that lacks a blood brain barrier, the _________. It induces the endothelial cells in this region to produce ______, which then diffuses into the adjacent POAH and decreases the activity of the thermoreceptors, thereby
resetting the hypothalamic temperature “set point” to a higher level.

Answer 35

OVLT (organumvasculosum of the lamina
terminalis),

prostaglandin E2 (PGE2)

Question 36

Sham rage is observed when the hypothalamus is

disconnected from _______ but the hypothalamic connections to the ______ & ______ remain intact.

Answer 36

higher brain areas (decorticate),

brainstem and spinal cord