0331 - Intro to the brain - CS Flashcards
- Outline the three embryonic brain vesicles, their subdivisions, and the structures derived from each
* The brain develops from a tubular structure called the neural tube.
* At the head end of this tube three swellings called primary vesicles appear and these give rise to the adult brain.
* These primary vesicles differentiate into the hindbrain, midbrain and forebrain of the adult:
- Forebrain
- Telencephalon –> Cerebral hemispheres, Limbic structures (+ lat vent)
- Diencephalon –> Thalamus, Hypothalamus, Retina (+ 3rd ventr) - Midbrain:
- Mesencephalon –> Tectum, Tegmentum (+ cerebral aqueduct) - Hindbrain:
- Metencephalon –> Pons, Cerebellum (+ 4th vent)
- Myelencephalon –> Medulla (+4th ventricle)
- Discuss, in general terms, the relationship between the brain ventricles and the embryonic brain vesicles
* The mature brain comprises collections of cells and cell processes (grey and white matter) arranged around a central complex of spaces called ventricles.
* The ventricles are remnants of the cavity of the neural tube
* The shape of the lateral ventricles reflects the growth patterns of the forebrain during foetal life
3a. Discuss in general terms, the functions of the cerebral hemispheres
* Each hemisphere is covered by a sheet of grey matter known as the cerebral cortex (see question on cerebral cortex for its function)
* A thick layer of white matter can be seen beneath the cortex. This is made up of fibres passing in both directions between the cortex and lower structures (eg thalamus, brainstem and spinal cord), fibres connecting different parts of the one hemisphere and fibres interconnecting corresponding parts of the two hemispheres.
* Masses of grey matter are embedded within the white matter. These are known collectively as basal ganglia & are important in the control of movement.
3b. Discuss in general terms, the functions of the cerebral cortex
* The site where the highest level of neural processing takes place.
* It enables us to consciously perceive sensory stimuli, to think and to make decisions.
* Because its surface area is so great the cerebral cortex is highly folded.
* The grooves are known as sulci and the bumps between the sulci are known as gyri
3c. Discuss in general terms, the names and functions of the deep nuclei in the cerebral hemispheres
* Deep nuclei including the caudate and putamen, substantia nigra and red nucleus are involved in regulating motor activity
3d. Discuss in general terms, the functions of the hippocampus
* Part of the limbic lobe, buried in the medial temporal lobe
* Essential for acquiring and retaining new learning and memories
* Major output tract is the fornix which terminates in the mammillary bodies
3e. Discuss in general terms, the functions of the corpus callosum
White matter made of axons connecting the two cerebral hemispheres and connecting homologous regions of cortex
3f. Discuss in general terms, the functions of the tectum
* Co-ordinates visual and auditory reflexes (eg. orienting gaze to a sound or movement)
* Contains:
- Superior colliculus - receives input from retina that is mapped to visual field
- Inferior colliculus - gets input from auditory field. Projects to thalamus
* Both colliculi output to other brainstem pathways
3g. Discuss in general terms, the functions of the thalamus
* Gateway to the cerebral cortex (sensory info that reaches the cortex 1st passes through thalamus)
* Comprises distinct groups of nuclei with specific functions, some from a specific modality, relayed to a specific cortical area:
- visual pathway
- auditory pathway
- somatosensory pathway
3h. Discuss in general terms, the functions of the hypothalamus
* The central control centre for the maintenance of homeostasis (a constant internal body environment). It does this either by direct neural connections with other brain structures or by controlling the levels of hormone production in the body
* A major regulator of the ANS
* Output is mainly via hormones released by the pituitary gland.
* Major input is from the limbic system via the fornix into the mammillary bodies
* Lies just beneath the thalamus.
* Is surprisingly small considering its importance
3i. Discuss in general terms, the functions of the pons
* Form the middle cerebellar peduncle, one of three bundles of fibres that connects the brainstem to the cerebellum
* CN V emerges from the lateral pons* Comprises the axons that cross the midline to enter the cerebellum
* Post-synaptic to descending motor fibres (corticopontine) which terminate on cells deep in the pons (the pontine nuclei)
* CN VI - VIII emerge in the groove between the pons and medulla
3j. Discuss in general terms, the functions of the cerebellum
* Major role in the
- learning and coordination of voluntary movements
- control of posture (including balance)
- control of muscle tone
* Gets input from joints and muscles (via spinocerebellar tracts), from CN VIII and from the cortex via pontocerebellar fibres
* Major output is from deep nuclei (eg dentate nucleus) to the thalamas and ‘red’ nucleus (motor nucleus) via the cerebellar peduncle
3k. Discuss in general terms, the functions of the medulla oblongata
* Cardiac regulation (cardiac centre),
* reflex regulation (reflex centres),
* blood pressure/vasodilation regulatin (vasomotor centre)
* respiratory regulation.
* Contains nuclei and is site of brain exit for 8 of 12 cranial nerves
- Describe, using anatomical terms, the areas of the cortex that are ‘mapped’ and those that are ‘unmapped’ and explain the relevance of this distinction
* Mapped cortical areas:
- represent a specific modality
- map that modality to create an ‘image’
- include primary and secondary cortical areas
* Unmapped cortical areas are referred to as “association cortex” and they
- Get input from other areas of the cortex
- Include a mix of modalities
- Are highly interconnected with the frontal lobe
Mapped areas examples and locations:
* Primary motor cortex (precentral gyrus/paracentral lobule)
* Primary somatosensory area (postcentral gyrus/paracentral lobule)
* Primary auditory area (superior temporal gyrus, posterior)
* Receptive speech (Wernicke’s) area (posterior to superior temporal gyrus
* Primary visual area (banks of calcarine sulcus)
* Primary olfactory area (uncus and parahippocampal gyrus, anterior)
- Explain the functional significance of each of the mapped regions of the cortex
* Mapped areas are characterised by a topographical organisation in which body surface, the range of audible frequencies or the outside world is represented on (“mapped” onto) the cortical surface.
* Maps are distorted so that highly discriminating or finely controlled items have a disproportionately large representation
- Primary motor cortex - gives rise to motor neurones for adjacent muscles of the body
- Primary somatosensory area - Sensation from adjacent areas of the body represented in adjacent cortical areas
- Primary auditory area - Related tones represented in adjacent cortical areas
- Receptive speech (Wernicke’s) area -
- Primary visual area -
- Primary olfactory area -
