NEUR532 - The Diencephalon Flashcards
Identify and describe the anatomical land marks and features of the 3rd ventricle
Identify and describe the major regions of the thalamus, subthamalus, epithalamus, hypothalamus
What are the major anatomical regions that comprise the Diencephalon?
Identify and describe the anatomical land marks and features of the 3rd ventricle
Ientify the major divisions of the pituitary gland
Identify the hormones of the anterior and posterior pituitary glands
Undertstand the function of the pituitary hormones
What are the 2 major subdivisions of the forebrain?
- Telencepalon
- diencephalon
What is the diencephalon divided symmetrically by?
Third ventricle
What is the diencephalon divided symmetrically by?
Third ventricle
What is the junction of the midbrain and diencephalon represented by?
Line that passes through the posterior commissure
What is the boundary between the diencephalon and the telencephalon represented by?
A line that traversess the interventricular foramen (foramen of monro) and the optic chiasma.
What is the adhesion or massa that bridges grey matter, joining the left and right thalami?
- Inter-thalamic adhesion
- Massa intermedia
What is the bundle of nerve fibers called that forms a prominent ridge along the junction of the medial and dosal diencephalon surfaces?
- Stria medullaris thalami
What is suspended from the roof of the third ventricle?
- Choroid plexus
What are the 4 major components of the diencephalon?
- Thalamus
- Subthalamus
- Epithalamus
- Hypothalamus
What is the largest component of the diencephalon?
Thalamus
The thalamic nuclei receive input from all sensory pathways EXCEPT.. WHAT?
Smell
What is the general shape of the thalamus?
egg shape
What is the narrow end of the thalamus called?
Anterior tubercle/nuclei
What does the anterior tubercle form?
Interventricular foramen
What is the wide posterior end of the thalamus called?
The pulvinars
What is the name of the thin laminae of white matter on the dorsal surface of the thalamus?
The stratum zonale
What is the name of the thin laminae of white matter on the dorsal surface of the thalamus?
The stratum zonale
What outlines the thalamus laterally?
The external medullary lamina
What divides the thalamus into groups of nuclei?
The internal medullary lamina
What is every thalamocortical projection reciprocally copied by?
Corticothalamic connection
The thalamocortical and corticothalamic
axons give collateral branches to
neurons in the…. what?
reticular nucleus
Where do thalamocortical axons originate?
Thalamocortical axons originate in the thalamus and project to the cerebral cortex
Where do corticothalamic axons originate?
Corticothalamic axons originate in the cortex and project to the thalamus
Are thalamic interneurons inhibitory or excitatory?
Inhibitory
What neurotransmitters do thalamic interneurons release?
gamma-aminobutyric acid (GABA)
- Glycine
What is the excitatory neurotransmitter within the thalamus?
Glutamate
Is the reticular nucleus connected with the reticular formation of the brain stem?
No
What is the reticular nucleus of the thalamus?
is a thin layer of cells located on the surface of the thalamus
What does the reticular nucleus do?
It receives excitatory corticothalamic and
thalamocortical fibers.
Certain features of the electroencephalogram
(EEG) in normal sleep depend on the activity of
neurons in the reticular nucleus of the thalamus,
which can suppress the transmission of signals
through the thalamic nuclei of the ascending
sensory pathways.
Certain features of the electroencephalogram
(EEG) in normal sleep depend on the activity of
neurons in the reticular nucleus of the thalamus,
which can suppress the transmission of signals
through the thalamic nuclei of the ascending
sensory pathways.
Certain features of the electroencephalogram
(EEG) in normal sleep depend on the activity of
neurons in the reticular nucleus of the thalamus,
which can suppress the transmission of signals
through the thalamic nuclei of the ascending
sensory pathways.
Is the subthalamus ventral or dorsal to the thalamus?
Ventral
What does the subthalamus include?
Tracts from the:
- Brain stem
- Cerebellum
- Corpus striatum
These terminate in the thalamus
What does the subthalamus include?
Tracts from the:
- Brain stem
- Cerebellum
- Corpus striatum
These terminate in the thalamus
What is the subthalamus primarily associated with?
- Movement
- Motor coorindation
- Muscle tone
What bundles of fibers does the subthalamus contain?
Sensory fasciculi
What are the key areas of the epithalamus?
- Habenular nuclei
- Pineal gland
- ANS tracts associated with behavioural and emotional changes
What is the shape of a the pineal gland?
pine cone
Where does the pineal gland receive afferent stimuli from?
Superior cervical ganglion
What are the pean gland cells called?
pinealocytes
The ventral wall of the pineal
stalk is attached to the
posterior commissure, which
carries axons involved in
pupillary reflexes and eye
movements.
What is the principal hormonal secretion from the pineal gland?
Melatonin
THE HYPOTHALAMUS
It is the part of the forebrain that integrates and controls the activities of the autonomic nervous system
and of several endocrine glands.
WHAT ARE THE 6 IMPORTANT STRUCTURES OF THE HYPOTHALAMUS?
- Third ventricle
- Mamillary bodies
- Tubercinereum
- The pituitary stalk
- The organum vasculoscum laminae terminalis (OVLT)
- The preoptic area
What surrounds the third ventricle?
Hypothalamus
What is the The Organum vasculosum
laminae terminalis (OVLT)?
one of the four
circumventricular organs associated
with the third ventricle.
What is the Organum vasculosum laminae terminalis (OVLT) associated with?
- Fevers
- Sodium regulation and metabolism
- Sodium appetite
The columns of the fornix anatomically do what?
These columns traverse the hypothalamus to
reach the mamillary bodies
What regulates the function of the hypothalamus?
- Neuronal input (behaviour, limbic system, visceral origins)
- Blood properties
- Temperature
- Osmotic pressure
- Hormones
How does the hypothalamus exert its function?
-efferent pathways to autonomic nuclei
- the pituitary gland by means of neurosecretory cells
-
The hypothalamus has a major role in producing responses
to emotional changes and to needs signalled by hunger and thirst.
responses most regularly elicited by stimulation of the anterior hypothalamus (preoptic area and anterior nucleus) include… what key things?
REST AND DIGEST
INHIBITORY
– slowing of the heart rate
– vasodilation
– lowering of blood pressure (BP),
– salivation
– increased peristalsis in the gastrointestinal (GI) tract
– contraction of the urinary bladder, and
– sweating.
Stimulation in the region of the posterior and lateral nuclei elicits what type of response?
SYMPATHETIC RESPONSES
noradrenergic sympathetic responses including
– cardiac acceleration
– elevation of BP
– cessation of peristalsis in the GI tract
– dilation of the pupils, and
– hyperglycemia.
Thermosensitive neurons in the ANTERIOR hypothalamus respond to an INCREASE in
temperature of the blood (HEAT)
A lesion in the anterior hypothalamus may therefore result in hyperthermia
Cells in the POSTERIOR hypothalamic nucleus respond to LOWERING of blood temperature (COLD)
A lesion in the POSTERIOR part of the hypothalamus destroys cells involved in conservation and
production of heat
This results in a serious impairment of temperature regulation in either a cold or hot environment
Contact of pyrogens with the dendrites of anterior hypothalamic neurons
results in inhibition of the mechanisms that cause loss of heat.
- Therefore, an abnormally high body temperature (fever) is typically
associated with infectious disease.
What hormone acts on the hypothalamus to reduce food intake?
Leptin
What does the orexin hormone do?
Continued feeding
What is the centre that inhibits food intake?
The satiety centre
The zona incerta of the subthalamus, the lateral and ventromedial
hypothalamic nuclei, and the subfornical organ are interconnected to control
water intake.
During wakeful state, two nuclei in the posterior hypothalamus are
active. These are…?
– The tuberomamillary nucleus and
– Nucleus of neurons secreting orexins
What is the area that contains the brains only histaminergic neurons?
The tuberomamillary nucleus
During deep sleep, one nucleus in the ventrolateral preoptic area is active, what nucleus, what 2 neurotransmitters does the nucleus secret?
a-aminobutyrate and galanin
The neurohypophysis consists
of structures of diencephalic
origin in the embryo:
– the median eminence
– pituitary stalk, and
– the posterior (neural) lobe of the
pituitary gland.
What Atypical astrocytes
are present in the pituitary stalk and posterior lobe?
(pituicytes)
Neurohypophysis
What 2 major hormones are released by the pituitary gland posterior lobe
- vasopressin
(antidiuretic hormone, ADH) - and oxytocin.
Where are hormones stored within the pituitary gland?
Herring bodies
What is oxytocin siginificantly important for?
- Contraction of uterus
- Milk production
The preoptic area and hypothalamus contain neurons that produce 1 peptide and, 1 amine and 1 hormone… what are they?
- Somatostatin (peptide)
- Somatotrophic hormone (STH)
- Dopamine
There is a separate hypothalamic-releasing hormone for each hormone of the
anterior lobe (except for what hormone?
Follicle stimulating hormone (FSH)
The releasing and inhibiting hormones pass distally by axoplasmic transport in the
axons of the cells that produce them, enter the capillaries of the portal system in
the median eminence, and are then delivered in locally high concentrations to
cells of the anterior lobe.
What are the hormones produced in the anterior pituitary lobe?
- FSH
- LH
- (TSH) Thyrotrophic or thyroid-stimulating hormone
- (ACTH) Adrenocorticotrophic hormone
- Prolactin
- Growth hormone (GH) or somatotrophic hormone (STH)
What does Adrenocorticotrophic hormone (ACTH) do?
– stimulates the cortex of the adrenal gland to produce and secrete cortisol (hydrocortisone) and other glucocorticoids (steroids)
– These secreted hormones modulate carbohydrate metabolism and protect against many
effects of stress.
– The secretion of aldosterone (the corticosteroid that limits sodium excretion), which is
necessary for life, is not under pituitary control.
What does Follicle-stimulating hormone (FSH) do?
– As the name implies, stimulates the growth of ovarian follicles and induces
their cells to secrete estradiol and other estrogens.
– FSH makes cells of the seminiferous tubules respond to testosterone for the
production of spermatozoa (in men).
What does LH do?
– This hormone stimulates the formation of a corpus luteum in the ovary after
ovulation and induces the luteal cells to secrete progesterone.
– Ovulation is the outcome of the combined actions of FSH and LH.
– In men, LH is known as interstitial cell-stimulating hormone as it induces the
interstitial cells (Leydig cells) of the testis to secrete testosterone and other
androgens.
What does LH do?
– This hormone stimulates the formation of a corpus luteum in the ovary after
ovulation and induces the luteal cells to secrete progesterone.
– Ovulation is the outcome of the combined actions of FSH and LH.
– In men, LH is known as interstitial cell-stimulating hormone as it induces the
interstitial cells (Leydig cells) of the testis to secrete testosterone and other
androgens.
What does prolactin do?
– stimulates the development of the mammary glands and lactation.
What does Growth hormone (GH) or somatotrophic hormone (STH) do?
– stimulates growth at the epiphyses of the long bones, the muscles and other body
organs.
– Its actions are largely mediated by another protein hormone, called insulin-like growth
factor 1 (ILGF-1), which is secreted by cells acted on by STH, (principally by liver cells).
