Anatomy - Lab 6 Flashcards
Name the three major types of fibre systems in the brain.
Commissural fibres - link regions of cortex in different cerebral hemispheres (e.g. corpus callosum)
Association fibres - link related regions of cortex within a single cerebral hemisphere (e.g. superior longitudinal fasciculus)
Projection fibres - link cortex with subcortical areas of CNS (e.g. internal capsule)
What does the superior longitudinal fasciculus link?
Frontal, parieto-occipital and temporal lobes
List association fibres.
Superior longitudinal fasciculus
Arcuate fasciculus
Uncinate fasciulus
What does the arcuate fasciculus join?
Joins frontal and temporal lobes
What does the uncinate fasciculus join?
Basal part of frontal lobe to anterior part of temporal lobe
What joins the areas of language (Brocas and Wernickes area)
Arcuate fasciculus
Arcuate loops also join adjacent gyri
What forms the lentiform nucleus?
Globus pallidus (more medial, lighter) Putamen (darker)
What separates the external capsule and extreme capsule?
Claustrum (thin layer of gray matter)
What lies directly next to the lateral ventricle?
Caudate nucleus
What lies next to the caudate nucleus?
Interal capsule
What is the corona radiata made of?
Projection fibres
What does the corona radiata connect?
Internal capsule to cortex
Name the structures found from lateral to medial, starting with the insular cortex.
Insular cortex - extreme capsule - claustrum - external capsule - putamen (lateral) - globus pallidus (medial) – internal capsule - caudate nucleus - lateral ventricle
In a horizontal section of the internal capsule, how do we tell the difference between the anterior and posterior limb?
Anterior limb is between the caudate nucleus and lentiform nucleus
Posterior limb has fibres between the thalamus and lentiform nucleus
What is important to note about the coronal section of the internal capsule?
ONLY ONE LIMB IS SHOWN
Name the major fibres running within the anterior limb of the internal capsule.
Anterior thalamic radiation/fronto-pontine and fronto-striate fibres
What major fibres run in the genu of the internal capsule?
Corticobulbar fibres (motor to cranial nerve nuclei, sensory input from face)
What major fibres run in the posterior limb of the internal capsule?
Major motor (corticospinal) and sensor projections relating to body
What is the function of the sublenticular part?
Auditory projection
What is the function of the retrolenticular part?
Visual projection
What is the most common single site of CVA (stroke)?
Posterior limb
Genu and posterior limb carry motor fibres to the head (genu) and body (posterior limb)
Major sensory projection from head and body also run in posterior limb
Small lesion in posterior limb of internal capsule gives mixed loss of motor and sensory functions
What nucleus is found in the sublenticular (auditory region)
Medial geniculate nucleus
What nucleus is found in the retrolenticular region (visual)?
Lateral geniculate nucleus
What blood vessels supply the internal capsule?
Central arteries
Where do the blood vessels (central arteries) arise from?
Circle of Willis and base of MCA
Name the two groups of the central arteries.
Lateral striate arteries
Medial striate arteries
What are the lateral striate arteries composed of and what do they supply?
Initial segment of MCA and penetrate deep into the brain (anterior perforated substance)
Supply posterior limb of internal capsule and nuclei of striatum
Where do the medial striate arteries arise from and what do they supply?
Arise from the base of the anterior cerebral artery
Supply anterior limb of internal capsule
Which group of central arteries are at risk of common sites of stroke?
Lateral striate arteries - small diameter and tortuous paths = blocked by emboli
What is the fornix?
Fibre bundle carrying information from the hippocampus to the hypothalamus
Part of limbic system
What is the function of the hippocampus and hypothalamus?
Hippocampus involved in memory
Hypothalamus involved in control of endocrine and autonomic functions
Describe the layout of the fornix.
Columns of fornix (anterior) run inferiorly to mamillary body of same side
Columns then run inferiorly and join to form the body of the fornix (lies above roof of third ventricle)
Fornix divides again to form the crura (crus) of the fornix which curve around and down into the floor of the inferior horn
Fornix arises from medial aspect of hippocampus as fimbria (fibres on surface of hippocampus)
Where does the hippocampus lie?
Floor of the inferior horn of the lateral ventricle
What is the most anterior region of the hypothalamus called?
Pes (broad and ridged surface)
What is the surface of the hippocampus covered by?
Smooth white layer of hippocampal efferent nerve fibres which run into fimbria of fornix
What is the fimbria of the fornix?
Efferent fibres coming out from cells located in the hippocampus
Where is the choroid plexus found in the lateral ventricle?
Body and inferior horn
Where does the amygdaloid nucleus lie?
Beyond the anterior limit of the inferior horn of the ventricle, deep to the uncus (hook shape on ventral surface of temporal lobe)
What is the function of the amygdala?
Strong primitive emotions e.g. anger and anxiety
Belongs to limbic system
What cortical regions associated with speech are likely to be connected with each other via long association fibres?
Broca’s and Wernicke’s Areas
What bundle of commissural fibres connects the two temporal lobes?
Anterior commissure
Where are the commissural fibres that connect between the two occipital lobes?
In the splenium (posterior part) of the corpus callosum
What parts of the striatum are almost completely separated from each other by the internal capsule?
The head of the caudate nucleus and putamen are almost completely separated by the anterior limb of the internal capsule
What part of the striatum bulges into the lateral ventricle?
The head of the caudate nucleus bulges into the anterior horn of the lateral ventricle
What cortical region bulges into the inferior horn of the lateral ventricle?
Hippocampus
