Limbic System Overview

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Questions and Answers

What does the hippocampus help with?

Transforming short-term to long-term memory.

What is the fornix and what is it responsible for?

The fornix is a white matter pathway that takes hippocampal axons to other parts of the brain. Though it connects parts of the cerebrum, it is technically not considered to be a part of the cerebrum.

What are the three main portions of the diencephalon?

The diencephalon is divided into three main portions; medial-posterior, lateral-posterior and anterior-superior divisions.

What is the function of the anterior thalamic nuclei and where is it found?

The anterior-superior division contains the anterior thalamic nuclei, which receive the mammillothalamic tract, and project to the cingulate gyrus. Signup and view all the answers

What are the two portions of the lateral-posterior division?

The lateral-posterior division is divided into dorsal and ventral tiers. Signup and view all the answers

What is the function of the ventral posterior nucleus?

The ventral posterior nucleus (commonly referred to as the VPN) receives sensation from the brainstem. Its medial portion receives trigeminal and gustatory signals, and its lateral portions receives spinal signals. Signup and view all the answers

What is the function of the lateral geniculate nucleus?

The lateral geniculate nucleus (LGN) is a protuberance on the inferior-lateral aspect of the pulvinar. It is important as part of the visual pathway, where retinal ganglion cell axons enter, to synapse. Signup and view all the answers

What is the medial geniculate nucleus and what is it responsible for?

The medial geniculate nucleus (MGN) is a protuberance on the inferior-medial aspect of the pulvinar. It receives auditory information from both ears (mainly the contralateral ear) and sends efferent axons to the auditory cortex within the temporal lobe via the auditory radiations. Signup and view all the answers

Which three main sections make up the brainstem?

The brainstem is divided into the hindbrain, which is both the medulla oblongata (myelencephalon) and the pons (metencephalon), plus the midbrain (mesencephalon). Signup and view all the answers

What are the pyramids and where are they located?

The pyramids, which are divided from one another by the midsagittal anterior median fissure, contain the major white matter motor/efferent tracts (corticospinal & corticobulbar). Signup and view all the answers

What are the olives responsible for?

The olives contain the olivary nuclei. Signup and view all the answers

The gracile and cuneate nuclei are responsible for receiving touch sensation from the spinal cord.

True Signup and view all the answers

What is the function of the nucleus ambiguous?

The nucleus ambiguous (CNs IX, X, and XI) control muscles of the throat via many cranial nerves. Signup and view all the answers

What is the function of the solitary tract nucleus?

The solitary tract nucleus (CNs VII, IX, X) receive visceral sensation and taste from several CNs that help make the solitary tract. Signup and view all the answers

What function does the dorsal nucleus of the vagus serve?

The dorsal nucleus of the vagus (CN X) control parasympathetic functions of the vagus nerve throughout the body. Signup and view all the answers

What is the location of the facial nucleus?

The facial nucleus (CN VII; at the inferior pons) is immediately posterior to the trapezoid bodies. Signup and view all the answers

What is the function of the abducens nucleus?

The abducens nucleus (CN VI; at the inferior pons) is in the posterior tegmentum. Signup and view all the answers

Where are the trigeminal nerve nuclei located?

They are located throughout the pons. Signup and view all the answers

Where is the superior cerebellar peduncle located?

It is located on the dorsal surface of the pons. Signup and view all the answers

What forms the medial eminences and where are they located?

The median sulcus, with the medial eminences on either side. Signup and view all the answers

What are the facial colliculi?

The facial colliculi are the expanded inferior ends of the medial eminences. Signup and view all the answers

What are the pontine nuclei and what are they responsible for?

The pontine nuclei are located in the basal part of the pons and receive corticopontine fibers from the cerebral cortex. Signup and view all the answers

What is the tegmentum and what does it contain?

Pontine tissue posterior to the trapezoid body is the tegmentum. Signup and view all the answers

What connects the pons and cerebellum with the diencephalon and cerebrum?

It is the mid brain. Signup and view all the answers

What area is known as the posterior perforated substance?

The crus cerebri (cerebral peduncles). Signup and view all the answers

Where is the pretectal nuclei located?

They are located anteriorly to the superior colliculi, the superior part of the corpora quadrigemina. Signup and view all the answers

What is the superior colliculi responsible for?

It is responsible for visual reflexes (i.e., tracking eye movements). Signup and view all the answers

What connects the superior colliculi with the lateral geniculate nucleus (LGN)?

The superior brachium. Signup and view all the answers

What connects the inferior colliculi with the medial geniculate nucleus (MGN)?

The inferior brachium. Signup and view all the answers

What is the tectum and where is it located?

The tectum is the posterior-most portion of the midbrain. Signup and view all the answers

What is the function of the cerebral aqueduct?

It connects the 3rd and 4th ventricles. Signup and view all the answers

What does the substantia nigra help with?

It functions as a motor nucleus. It is connected to the cerebral cortex, spinal cord, hypothalamus and basal nuclei to help control muscle activity. Signup and view all the answers

What is the function of the red nucleus?

It is found in the tegmentum, at the level of the superior colliculi. Signup and view all the answers

What does the crus cerebri connect?

The crus cerebri is a region in the midbrain connecting the cerebral cortex with the spinal cord, pons, cerebellum, and cranial nerve nuclei. Signup and view all the answers

What does the reticular formation do?

It is a network of nerve cells that runs vertically from the spinal cord to the thalamus. Signup and view all the answers

What is the cerebellum responsible for?

It integrates proprioceptive information (movement of voluntary muscle, tendons, joints) with balance and sight information, and sends inhibitory signals to the nuclei of origin of certain efferent tracts to the spinal cord and motor cortex. Signup and view all the answers

What are the three lobes of the cerebellar hemispheres?

The three lobes of the cerebellar hemispheres are anterior lobe, middle lobe, and flocculonodular lobe. Signup and view all the answers

What are the three layers of the cerebellar cortex?

They are molecular layer, Purkinje cell layer and granular layer. Signup and view all the answers

What is the spinal cord and what is its function?

The spinal cord is the most caudal portion of the CNS, a long cylindrical structure extending from the foramen magnum to the L1 vertebra. Signup and view all the answers

What are the meninges and what do they do?

The meninges are three layers of protective tissue that surround the spinal cord, similar to those surrounding the brain. Signup and view all the answers

What is the function of the ligamentum denticulatum?

These thicken in between the nerve roots, giving the structure a toothy appearance. Signup and view all the answers

What is the function of the filium terminale?

It is a thin, fibrous extension of the pia mater that extends from the conus medullaris to the coccyx. Signup and view all the answers

What are the two parts of the gray matter?

The two parts are the anterior and posterior horns. Signup and view all the answers

What is the commissure?

It connects the anterior and posterior horns, with the central canal located in the center of the commissure. Signup and view all the answers

What is the function of the anterior (ventral) horn?

It contains a-efferent and y-efferent neuron cell bodies, which are large, multipolar cells that exit via the anterior spinal root to innervate extrafusal skeletal muscle and muscle spindles, respectively. Signup and view all the answers

What is the function of the posterior (dorsal) horn?

It contains several cell body groups for touch, pain, and temperature signals. Signup and view all the answers

What does the nucleus proprius cell group do?

It receives fibers from the posterior white column of spinal cord (mainly ascending sensory information). Signup and view all the answers

What is the nucleus dorsalis and where is it located?

The nucleus dorsalis (Clark's column) is located in the posterior horn and is only found from T1 to L3. Signup and view all the answers

Where is the lateral horn located and what does it contain?

Located in the thoracic and upper lumbar segments of the spinal cord. Signup and view all the answers

What is the function of the interneurons in the spinal cord?

They are small neurons that links two longer neurons together and are most often inhibitory and associated with a reflex arc to inhibit the action of the antagonistic muscle. Signup and view all the answers

What are the three parts of the white matter?

It is divided into three main parts: anterior, posterior, and lateral columns. Signup and view all the answers

What are the three types of neuronal pathways in the spinal cord?

They are ascending, descending and intersegmental. Signup and view all the answers

What is the general pathway followed by ascending neuronal pathways?

The ascending neuronal pathways carry afferent signals from the spinal cord to the brain and follow a general pattern involving three neurons: first-order, second-order, and third-order neurons. Signup and view all the answers

Where does the first-order neuron start and end?

The first-order neuron starts at the sensory receptor in the periphery and ends on the dendrites or soma of the second-order neuron in the CNS. Signup and view all the answers

What happens to the second-order neuron axon?

The second-order neuron axon usually decussates (crosses over to the contralateral side) at or slightly above this same level via the anterior white commissures. Signup and view all the answers

What is the function of 3rd order neurons?

They ascend to the brain to synapse on the third-order neuron. Signup and view all the answers

What are the two specific ascending spinal tracts?

The two specific ascending spinal tracts are the spinothalamic (anterolateral) tract and the dorsal column (posterior funiculus) – medial lemniscal tract. Signup and view all the answers

What does the spinothalamic (anterolateral) tract transmit?

It transmits course touch and pressure as well as pain and temperature sensation. Signup and view all the answers

Where do first-order neurons synapse in the spinothalamic tract?

They synapse on second-order neurons within the posterior gray horn (specifically the substantia gelatinosa). Signup and view all the answers

Where do second-order neurons in the spinothalamic tract decussate?

They decussate at or slightly above this same level via the anterior white commissures. Signup and view all the answers

What does the dorsal column (posterior funiculus) – medial lemniscal tract transmit?

It transmits light touch, vibration, proprioception from joints and musculature (body posture, balance) and 2-point discrimination sensation. Signup and view all the answers

Where do first-order neurons synapse in the dorsal column-medial lemniscal tract?

They synapse on second-order neurons in the nuclei gracilis and cuneatus of the dorsal medulla. Signup and view all the answers

What do second-order neurons in the dorsal column-medial lemniscal tract do?

They decussate in the medulla oblongata via the sensory decussation. Signup and view all the answers

What are the functions of descending neuronal pathways?

They carry efferent signals from the brain to the spinal cord, allowing muscle and glandular activity. Signup and view all the answers

What are the two main neurons involved in descending neuronal pathways?

The two neurons are upper motor neurons and lower motor neurons. Signup and view all the answers

Where do upper motor neurons start?

They start with the neuronal soma in the cerebral cortex and deep cerebral and brainstem nuclei. Signup and view all the answers

What happens to the axons of upper motor neurons?

They descend to different spinal segments, where they synapse on neuronal cell bodies in the anterior gray horn of the spinal cord. Signup and view all the answers

What is the function of lower motor neurons?

They have their soma in the anterior gray horn of the spinal cord, and their axons exit the spinal cord in the anterior spinal root and run to muscles and glands. Signup and view all the answers

What are corticospinal tracts and what do they send?

Corticospinal tracts send efferent information that controls voluntary, skilled movements, such as those involved in fine motor control and complex movements. Signup and view all the answers

Where do most of the corticospinal tracts decussate?

They decussate at the inferior/caudal border of the medulla oblongata at the area called the decussation of the pyramids. Signup and view all the answers

What do the fibers that decussate in the corticospinal tract do?

They descend through the spinal cord in the contralateral corticospinal tracts in the white column and terminate in the ventral gray horn of the spinal cord. Signup and view all the answers

What do the fibers that do not decussate in the corticospinal tract do?

They descend in the ipsilateral anterior corticospinal tract in the white column. Signup and view all the answers

Study Notes

Limbic System

The hippocampus is an extension of the cerebral cortex in the medial temporal lobe.
It transforms short-term memory into long-term memory.
The fornix is a white matter pathway connecting the hippocampus to other brain areas.
The fornix is not part of the cerebrum, despite connecting to it.
Axons in the hippocampus ascend into the fornix, forming its crura.
The crura form the fornix body, running alongside each other and interconnecting.
The fornix bodies lie below the corpus callosum and descend, splitting into anterior and posterior columns of white matter.
The fornix bodies are above the hypothalamus.
The Papez circuit involves short-term memory, long-term memory formation and linking to the autonomic nervous system, endocrine system and emotions.
The amygdala mediates fear, connecting to the olfactory system, septal nuclei, diencephalon and midbrain.
Phobias are tied to early reactions in the amygdala before the hippocampus fully developed.
Post-traumatic stress disorder can affect the hippocampus and long-term memory, leading to flashbacks triggered by certain stimuli.

Diencephalon

The diencephalon surrounds the third ventricle.
It stretches from the optic chiasm to the mammillary bodies.
Visible structures on the inferior surface include the optic chiasm and optic tracts, tuber cinereum, infundibulum and the pituitary gland.
Mammillary bodies are gray matter protuberances with a white matter capsule.
The lateral surface is defined by the internal capsule and the medial surface by the walls of the third ventricle.
The thalamus acts as a relay for sensory information (except olfaction)—this information is organized and then sent to the appropriate area of the cerebral cortex.
Inside the thalamus, the internal medullary lamina separates into medial-posterior, lateral-posterior and anterior-superior divisions, which further divide into nuclei with different functions.
The anterior thalamic nuclei receive the mammillothalamic tract, and project to the cingulate gyrus.
Many nuclei in the medial-posterior division integrate somatic, olfactory and visceral information to emotions.
The lateral-posterior division contains dorsal and ventral tiers.
The ventral tiers include the ventral anterior, ventral lateral and ventral posterior nuclei which receive trigeminal, gustatory and spinal signals respectively.
Lateral geniculate nucleus (LGN) relays visual information to the primary visual cortex.
Medial geniculate nucleus (MGN) relays auditory information to the auditory cortex.

Brainstem

The brainstem connects the spinal cord, diencephalon and cerebrum.
It's responsible for reflexes that control respiration and cardiovascular functions and consciousness.
It contains nuclei for cranial nerves III through XII.
The brainstem includes the hindbrain (medulla oblongata and pons) and the midbrain.
The medulla oblongata connects to the spinal cord and lies caudal to the pons.
Its anterior surface has pyramids, which are white matter tracts carrying motor/efferent signals.
The pyramids cross over in the decussation, making the right and left hemispheres control opposite sides of the body.
The posterior surface has the gracile and cuneate tubercles, containing nuclei responsible for touch sensation from the spinal cord.
The pons carries transverse fibers and has nuclei for cranial nerves V, VI, VII.
Its surface has the basilar groove and middle cerebellar peduncles.
The midbrain connects the pons and cerebellum to the diencephalon and brainstem.

Cerebellum

The cerebellum integrates proprioception, balance and sight with muscle movements.
It has two hemispheres and vermis connected at midline.
The cerebellum has three lobes including the anterior, middle and flocculonodular lobes, separated by fissures.
Cerebellar cortex is comprised of gray matter over internal white matter.
It has three layers (molecular, Purkinje cell and granular)
Input to the cerebellar cortex is mainly via climbing and mossy fibers.
Climbing fibers originate in the contralateral olivary nuclei and form synapses in the molecular layer,
Mossy fibers originate from other inputs and synapse in the granular layer.

Spinal cord and ascending/descending tracts

The spinal cord is the most caudal portion of the CNS, transmitting information from the brain to the periphery and vice-versa.
It contains 31 pairs of spinal nerves that emerge from each segment.
Contains internal and external structures for various functions.
The internal includes the gray matter (H-shaped), containing anterior and posterior horns and the gray matter commissure.
Anterior horns have a- and y-efferent neurons that innervate skeletal muscles.
Posterior horns have sensory neurons for touch, pain, and temperature.
White matter tracts include ascending and descending pathways.
Ascending pathways carry sensory information to the brain, with first, second and third order neurons involved.
Descending pathways carry motor instructions from the brain to the spinal cord.
Specific ascending tracts include the spinothalamic (temperature and pain), and the dorsal column/medial lemniscus (touch and proprioception) tracts.

Reticular Formation

The reticular formation is a network of cells that runs vertically from the spinal cord to the thalamus.
It receives input from many sensory systems.
It transmits efferent information to influence many CNS processes.
It has one median column and two medial and lateral columns.
It has numerous functions including, control of skeletal muscle activity, and eye movements, including arousal and states of consciousness.

Spinal Cord Tracts

Ascending tracts carry sensory information to the brain, first via sensory receptors to the spinal cord.
Descending tracts carry motor signals from the brain to the spinal cord, with upper and lower motor neurons involved.
Spinothalamic tract carries pain and temperature, and dorsal column/medical lemniscus carries vibration and touch.

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Description

Explore the essential functions and structures of the limbic system, including the hippocampus, fornix, and amygdala. This quiz highlights the interaction between memory formation and emotional responses. Test your knowledge on how these components connect and operate within the brain.