Topography of the Brain Flashcards
What are the pyramidal tracts/medullary pyramids?
Motor fibres for the corticospinal and corticobulbar tracts (pyramidal tracts) which pair as white matter structures (medullary pyramids)
What are the peduncles?
Elongated stalks of tissue that connect structures of the brain
What are the red nuclei?
The red nucleus is one of the brainstem nuclei and part of the extrapyramidal system. They are situated within the tegmentum of the midbrain. Involved in coordination of muscle tone, body position and gait
What are the substantia nigra?
Pat of the midbrain, the substantia nigra is an important player in brain function, in particular, in eye movement, motor planning, reward-seeking, learning, and addiction. It is closely linked to the striatum
What are the colliculi?
Make up the corpora quadregemina - reflex centres involving hearing and balance. Two superior two inferior. Superior - preliminary visual processing, control of eye movements Inferior - auditory processing
What is the inferior olivary nucleus?
The largest nucleus situated in the olivary body, part of the medulla oblongata. It is involved in motor control. It is a major source of input to the cerebellum. The hypoglossal nucleus sends its fibers ventrally between the pyramid and inferior olivary nucleus to exit as the hypoglossal nerve
What is the reticular formation?
A set of interconnected nuclei located throughout the brainstem
What are the two key functions of the cerebellum?
Maintain posture
Fine tune motor activity
How can signals reach the cerebellum?
Information from pyramidal tracts - motor intention of the brain
Information from the ipsilateral proprioceptors
Information from vestibular nuclei(in the vestibule) re balance and posture
What are the three main components of the brainstem?
Midbrain, pons, medulla
What does the brainstem contain?
CN III-XII, tracts from spinal cord, vital centres e.g. cardiorespiratory centre
Generally speaking, what do the brainstem centres govern?
The rigidly programmed automatic behaviours essential for survival
With how many of the cranial nerves is the brainstem involved?
10
From where does the medulla develop?
Hindbrain vesicle
What is the cavity of the medulla also known as?
The IV ventricle
At what point do the medullary pyramids cross over?
The decussation (at the lower limit of the pyramids)
Which cranial nerves emerge from the surface of the medulla?
IX, X, XI & XII
What structure connects the medulla to the cerebellum?
The inferior cerebellar peduncle
From where does the pons develop?
Mentencephalon part of the hindbrain vesicle
What structure is the pons anterior to?
The IV ventricle
What peduncle is present on the surface of the pons?
Middle cerebellar peduncle
Which cranial nerves originate from the surface of the pons?
V, VI, VII & VIII
From where does the midbrain originate?
The mesencephalon
What is the name of the central cavity of the midbrain?
Cerebral aqueduct
What peduncles are present on the surface of the midbrain?
The cerebral peduncle, superior cerebellar peduncle
Which cranial nerves originate in the midbrain?
III, IV
What is unique about the trochlear nerve (IV) in relation to the brainstem?
It is the only nerve to originate posteriorly
What is the function of the central cavity, by what name is it also known, in which part of the brainstem does it reside?
It connects the III & IV ventricles, cerebral aqueduct, midbrain
What is the cerebral peduncle?
Made up of the tegmentum and the cerebral crus of the midbrain
What are the two parts of the cerebellar white matter?
Arbor vitae, cerebellar peduncles
What are the two parts of the cerebellar grey matter?
Cortex on the surface, deep nuclei
What separated the right and left hemispheres of the cerebellum?
The Vermis
What lobes are present in both hemispheres of the cerebellum?
Anterior, posterior, flocculondular lobes
What are present on the surface of the cerebellum?
Sulci and folia
What are the two main functions of the cerebellum?
Posture maintenance
Fine tuning motor activity
Where does the cerebellum receive its information from?
Pyramidal tracts
Ipsilateral proprioceptors from periphery
Vestibular nuclei re balance and posture
What is ataxia?
A loss of full control of body movements, abnormality affecting cerebellum
Tests for ataxia?
Finger - nose test, knee - heel test, walking in a straight line
What is the diencephalon?
The thalamus, hypothalamus and pituitary, epithalamus (pineal gland). All are mainly grey matter
From where does the diencephalon develop?
The diencephalic vesicle - part of the forebrain vesicle
Where is the diencephalon?
Deep within the cerebral hemispheres, around the III vesicle
What is the thalamus?
A sensory relay station, an egg shaped body on either side of III ventricle, around 80% of diencephalon
What does the thalamus consist of?
Mainly groups of nuclei - anterior medial lateral. Lateral group are involved in sensory processing
What is the hypothalamus?
The main visceral control centre and essential for overall homeostasis
What separates the hypothalamus from the thalamus?
The hypothalamic sulcus
What are the homeostatic roles of the hypothalamus? (six)
Autonomic control centre Body temperature regulation Regulation of food intake Regulation of water balance and thirst Regulation of sleep-wake cycle Control of endocrine system functioning
What are the main arteries supplying the brain?
The two ICAs via the carotid canal (foramen lacerum) and the two vertebral arteries via the foramen magnum
What artery is formed when the two vertebral arteries meet?
The basilar artery. The vertebra-basilar system gives branches that supply the brainstem and cerebellum
What is the Circle of Willis?
Branches of the ICAs joining with branches of the PCA (branch of the basilar artery) to form a continuous circle at the base of the brain
What protective role does the Circle of Willis serve?
Protects against vast-occlusion of large arteries and resulting ischaemia. However, the arteries supplying the circle are end arteries and occlusion in these vessels beyond the circle will result in ischaemia
Describe the venous drainage of the brain
Superficial and deep veins of the brain drain into venous sinuses which lie between 2 layers of dura matter
Describe the fate of the dural venous sinuses
They join together, ultimately draining into the IJVs
