Chapter 9 - Reticular Formation & Limbic system Flashcards
3 longitudinal Columns of the Reticula Formation
- Median column
- Medial column
- Lateral column
“M”edian”L” has L meaning it is more “L”ateral than median with no “L”
Size of neurons in:
(1) Median longitudinal column
(2) Medial longitudinal column
(3) Lateral longitudinal column
(1) Intermediate sized neurons
(2) Large sized neurons
(3) Small sized neurons
Media”N” for i”N”termediate, media”L” one L for “Large”. “L”atera”L” two Ls for sma”LL”
Reticular Formation Relations:
(1) superiorly
(2) inferiorly
(3) laterally
(1) cerebral cortex
(2) interneurons of spinal cord gray matter
(3) cerebellum
Reticular Formation Functions (#7)
- control of skeletal muscle
- control of facial expression muscle
- control of somatic and visceral sensations
- control of ANS
- control of endocrine system
- influence biologic clock
- reticular activating system (consciousness)
Location of reticular formation
At the center of the cerebrospinal axis
at the brinstem (?)
Components of the Hippocampal Formation
1) hippocampus
2) dentate gyrus
3) parahippocampal gyrus
Hippocampus is a curved elevation of gray matter that extends throughout the entire length of the floor of the inferior horn of the lateral ventricle
Hippocampus
A curved elevation of gray matter that extends throughout the entire floor of the inferior horn of the lateral ventricle
Limbic System Structures
- amygdaloid nucleus
- parahippocampal gyri
- hippocampal formation
- subcallosal
- cingulate
- mammillary bodies
- anterior thalamus nuclei
Limbic system connecting pathways
*alveus
*fimbria
*fornix
*mammillothalamic tract
*stria terminalis
white nerve fibers extending from hippocampus converging into the fimbria
alveus
Notch of gray matter that lies between the parahippocampal gyrus and the fimbria
Dentate gyrus
Thin vestigial layer of gray matter that covers the superior surface of the corpus callosum (below cingulate gyrus)
Indusium griseum
posteriorly, the dentate gyrus accompanies the fimbria and becomes continuous to the indusium griseum
Between the hippocampal fissure and the collateral sulcus;
continuous with the hippocampus along the medial edge of the temporal lobe
parahippocampal gyrus
Nuclei groups of the amygdala
*basolateral group (larger)
*corticomedial group (smaller)
Connects the Right and left crura of the fornix to form the body of the fornix
commissure of the fornix
Foramen of Monro
The body of the fornix splits anteriorly into two columns of the fornix that curves anteriorly and inferiorly over the foramen of monro
Interventricular foramen connects the lateral ventricles and the 3rd ventricle
Major output pathway of the limbic system
Hypothalamus
Emotional behavior influenced by the limbic system
Fear, anger, sexual behavior
Converts short term memory to long term memory
Hippocampus
When new short term memory cannot be converted to long term but previous memory is unaffected
50 First Dates
Anterograde Amnesia
Expanded anterior end of the hippocampus
Pes Hippocampus
Net of nerve cells and fibers strategically placed to connect important nerve tracts and nuclei
Reticular formation
Reticular meaning
Having form a net
Afferent Projections to the Reticular Formation
(1) from spinal
(2) from cranial nerve nuclei
(3) from cerebellum
(4) from basal nuclei
(1 - From spinal)
Spinoreticular, spinothalamic, medial lemniscus
(2 - From cranial nerve nuclei)
Vestibular, acoustic, visual pathway, primary cortex of the frontal lobe, somesthetic cortex from parietal lobe
(3 - From cerebellum)
Cerebroreticullar pathway
(4 - From basal nuclei)
subthalamic, hypothalamic, thalamic nuclei, corpus striatum, and limbic system
Efferent projections from the Reticular Formation
(1) to the brainstem & spinal cord
(2) to sympathetic outflow & the craniosacral parasympathetic outflow of ANS
(3) to other parts of the brain
(4) to the cerebral cortex
(1 - to brainstem and spinal cord)
reticulobulbar & reticulospinal
(2 - to the sympathetic outflow and the craniosacral parasympathetic outflow of the ANS)
(3 - to the corpus striatum, cerebellum, red nucleus, substantia nigra, tectum, nuclei of the thalamus, subthalamus, and hypothalamus)
(4 - to cerebral cortex)
Reticular formation is a net of nerve cells and fibers that receives and sends signals to influence ()
- skeletal muscle activity (movement)
- somatic and visceral sensations
- autonomic and endocrine system
- level of consciousness
Limbic System
Initially reffering to a group of structures that lie in the border zone between the cerebral cortex and the hypthalamus - now includes other structures beyond border zone
Important in “BE DiM” - Behavior, Emotion, Drive, Memory
Limbic System - label
1) subcallosal gyrus
2) cingulate gyrus
3) parahippocampal gyrus
4) uncus
Limbic System - label
1) subcallosal gyrus
2) cingulate gyrus
3) parahippocampal gyrus
4) uncus
Limbic System - label
1) mammillary body
2) fornix - column
3) fornix - body
4) fornix - commissure
5) fornix - crus
6) fimbria (of the hippocampus)
7) hippocampus
8) dentate gyrus
9) pes hippocampus
10) amygdaloid body
11) mammillothalamic tract
12) anterior thalamic nucleus
Named due to it ressembling a seahorse
Hippocampus
Resembles an almond
amygdaloid nucleus
At which area do fibers of the fornix decussate to join the hippocampi of the two sides?
commissure of the fornix
Fornix relations:
(1) anteriorly
(2) inferiorly
(1) undersurface of the corpus callosum by the septum pellucidum
(2) tela choroidea and the ependymal roof of the 3rd ventricle
(True/False)
The parahippocampal gyrus is 6-layered. As it traces into the hippocampus there is a gradual transition in to 3 layers
True
3 layers: superficial molecular layer, pyramidal layer, & polymorphic layer
(True/False)
Similar to the hippocampus, the dentate gyrus is composed of a superficial molecular layer, pyramidal layer, & polymorphic layer
False
The dentate gyrus is composed of 3 layers but the pyramidal layer is replaced by the granular layer
The afferent connections of the hippocampus are divided into 6 groups namely:
“from () to the hippocampus”
(1) from cingulate gyrus
(2) from septal nuclei
(3) from one hippocampus to the other
(4) from the indusium griseum
(5) from entorhinal area or olfactory associate cortex
(6) from the dentate and parahippocampal gyri
Efferent connections of the hippocampus
“From the hippocampus to ()”
(1) mammillary body > medial nucleus
(2) anterior nuclei of the thalamus
(3) to tegementum of the midbrain
(4) to septal nuclei, lateral preoptic area, and anterior part of the hypothalamus
(5) stria medullarix thalami > habernular nuclei
Damage to the reticular formation causes
loss of consciousness or coma
MOA of lessening worse symptoms of schizophrenia
Blocking dopamine receptors of the limbic system
e.g. phenothiazine
Kluver-Bucy syndrome
patient becomes docile showing no evidence of fear and anger with increased appetite and sexual activity
Association: unilateral or bilateral destruction of the amygdaloid nucleus results in a decrease in aggressiveness, emotional instability, and restlessness with increased interest in food and hypersexuality
The following statements concern the reticular formation:
(a) Reticulobulbar and reticulospinal tracts form the afferent pathways from the reticular formation to the motor nuclei of the cranial nerves
and the anterior horn cells of the spinal cord, respectively.
(b) The reticular formation extends through the neuroaxis from the spinal cord to the midbrain.
(c) The main pathways through the reticular formation may easily be traced from one part of the CNS to another using silver stains.
(d) Superiorly, the reticular formation is relayed to the cerebral cortex.
(e) Afferent pathways project into the reticular formation from only a few parts of the CNS.
D
The following statements concern the functions of the reticular formation:
(a) It Influences the activity of the a and ‘Y motor neurons.
(b) It opposes the actions of the vestibular spinal tract.
(c) It does not bring about reciprocal inhibition during contraction of the prime mover muscles.
( d) It plays no part in maintaining the tone of the antigravity muscles.
(e) It cannot modulate reflex actMty.
A
The following statements concern the functions of the reticular formation:
(a) It does not affect the reception of pain.
(b) It cannot influence all ascending pathways to the suprasplnal levels.
(c) By means of Its reticulobulbar and retlculospinal tracts, it can control parasympathetic and sympathetic outflows.
(d) It has no effect on biologic rhythms.
(e) It does not influence the degree of wakefulness of an individual.
C
Anatomically, the following structures collectively form the limbic system:
(a) Amygdalold nucleus, red nucleus, and vestibular nuclei
(b) Pulvinar of the thalamus and the substantia nigra
(c) Hippocampal formation
(d) Cingulate gyrus and uncus
(e) Subcallosal, cingulate, and parahippocampal gyri, hippocampal formation, amygdaloid nucleus, mammillary bodies, and anterior thalamic nuclei
E
The following statements concern the efferent connections of the hippocampus:
(a) They arise from the small granular cells of the cortex.
(b) They travel through the fornix.
(c) None of the fibers enter the mammillary body.
(d) The fibers within the fomlx pass posterior to the interventricular foramen.
(e) Some of the fibers end in thalamic posterior
nuclei.
B
The following statements concern the functions of the limbic system:
(a) It is not concerned with fear and anger.
(b) It is concerned with visual experiences.
(c) The hippocampus is concerned with recent memory.
(d) The limbic system plays an important role in olfactory function.
(e) It directly influences the activity of the endocrine system.
C
(1) body of fornix
(2) dentate gyrus
(3) parahippocampal gyrus
(4) uncus
