Nervous System Part 2: Diencephalon Flashcards
Fully formed adult structures that lie rostral to the midbrain.
4 Parts:
-Thalamus
-Hypothalamus
-Epithalamus
-Subthalamus
Diencephalon
Contains 2 nuclei. Lies laterally, so difficult to visualize. Requires far lateral sagittal or coronal section to view.
Responsible for motor control of several of the basal ganglia
Subthalamus
A hollow slit contained between the two lobes of the thalamus.
Above it is the Fornix and below is the Hypothalamus
3rd Ventricle
A collection of white matter lateral to the thalamus. Contains fibers coming out of the Cerebral Cortex
Internal Capsule
Connected to the Stalk of the Pituitary Gland
Hypothalamus
Contains the Pineal Gland (which calcifies in teenage years)
Epithalamus
The largest portion of the Diencephalon; has two lobes and between them is the 3rd Ventricle
Thalamus
The connection that joins together the two lobes of the Thalamus. About 80% of the population has one. Inert tissue joining the lobes together
Massa Intermedia (Thalamic Adhesion)
Divides the thalamus into three nuclear regions:
-Lateral nuclear group
-Medial nuclear group
-Anterior nuclear group
Internal Medullary Lamina
General sensation coming from outside of the brain is projected here. Those fibers stop and new fibers are originated and project into the Cerebral Cortex.
Pain, temperature, special senses like vision, hearing, etc. enter the brain and project to one of the Lateral Nuclei (of the thalamus). Those fibers end and new fibers go into the Cerebral Cortex (Post-Central Gyrus: Primary receiving area for general sensation)
Relay Nuclei
What is the primary receiving area for general sensation?
Post-Central Gyrus
These project information from the Reticular Formation up to the relay nuclei and then to the Cerebral Cortex.
-Found in the Medial Nuclei of the thalamus and the thalamic reticular cover that runs along the side of the thalamus
Diffuse (non-specific) Nuclei
These connect ipsilateral cerebral cortex with other parts of the cerebral cortex (on the same side)
-Found in the Lateral and Anterior group.
-Receive information coming back down from the Cerebral Cortex and send it up to Association Areas (Parietal Lobe) to be integrated/associated
Association Nuclei
Have a stimulus (sensory). Goes to Relay Nuclei in Lateral group -> initiates new fibers -> Cerebral Cortex (Post-central gyrus) -> Info comes back down from Cerebral Cortex -> Association Nuclei in Anterior/Lateral Group -> Association Areas (Parietal Lobe) -> Associate and integrate stimulus to be able to describe it (hot, sharp, dull, etc).
Thalamic Nuclei
The boundary separating thalamus and hypothalamus
Hypothalamic Sulcus
-Mammillary Nucleus (has bump called Mammillary Body)
-Preoptic Nucleus
-Supraoptic Nucleus
Hypothalamic Nuclei
The integrating center for the Autonomic Nervous System.
-Anterior: Parasympathetic
-Posterior: Sympathetic
These two are constantly working in opposition to each other to see which can give the strongest effect.
Hypothalamus
-Thermoregulation (Controls body temperature)
-Appetite Regulation (controls hunger/satiety)
-Thirst regulation
-Pituitary Hormonal Regulation
Hypothalamus
The hunger center of the Hypothalamus
Lateral Hypothalamus
The satiety center of the hypothalamus (tells us when we’re full)
Ventromedial Hypothalamus
The thirst center of the hypothalamus
Anterior Hypothalamus
The thermoregulation center of the hypothalamus
Preoptic Area
Where the Optic nerves cross. Occurs right in front of the Diaphragma Sellae, so an enlarged pituitary gland can put pressure on this causing a visual defect
Optic Chiasm
Sits in the Hypophyseal Fossa (depression in the Sphenoid bone)
-Surrounded by a donut shaped layer of Dura Mater called the Diaphragma Sellae.
Pituitary Gland
Pars Anterior (Adenohypophysis)
Pars Posterior (Neurohypophysis)
and Pars Intermedia
All 3 secrete hormones
Parts of Pituitary Gland
Regulated by the Hypothalamus, but hormones are produced here.
-Thyroid Stimulating Hormone (TSH)
-Adrenocorticotropic Hormone (ACTH): stimulates adrenals
-Follicle-Stimulating Hormone (FSH): Maturation of sperm and eggs
-Luteinizing Hormone (LH): ovulation and production of testosterone
-Somatotropin Hormone (STH aka Growth Hormone)
-Prolactin: breast milk
Adenohypophysis (Anterior Pituitary)
Hypothalamus produces hormones that migrate here to be secreted into the bloodstream.
-Oxytocin: labor/pregnancy
-Vasopressin (ADH - can increase fluid retention or decrease and lead to fluid loss)
Posterior Pituitary (Neurohypophysis)
Produces Melanocyte Stimulating Hormone (MSH)
-Causes melanocytes to secrete Melanin - darkens skin. Increased during pregnancy
Pars Intermedia
Part of the Epithalamus
-Function unknown: Possible sleep/wake cycle or sexual maturity
Habenula
Part of the Epithalamus that produces Melatonin to regulate sleep patterns
-Appears to only be active for the early portion of life and during the teenage years begins to be calcified and atrophies
Pineal Gland
Inferior to the Subthalamic nucleus.
-A dark, pigmented nucleus
-Cells here secrete Dopamine
-Strongly associated with Parkinson’s Disease (degenerative condition where you gradually lose cells/cell bodies out of this)
Substantia Nigra
Exerts an inhibitory influence on bad movement (Dyskinesias).
-Prevents Hemiballismus: when someone has upper limb movements they can’t control.
-Only get a break when they’re sleeping
Subthalamus
-Tremor at rest (pill rolling)
-Muscle Rigidity (lead pipe)
-Masked face and Forward head
-Shuffling gait with festination (when they walk, get faster and faster and may not be able to stop)
-Reduced arm swing
-Stooped posture
-Slow, slurred speech
Parkinson’s Disease
