6. General Organisation and Functional Anatomy of the Brain and Brainste Flashcards
What is the CNS composed of?
Brain (cerebrum, cerebellum, brainstem) and spinal cord
What is the PNS composed of?
Dorsal and ventral roots, spinal nerves and peripheral nerves, cranial nerves
Compare motor and sensory neurones
motor - from CNS to PNS
sensory - from PNS to CNS
What is the forebrain?
part of the brain that sits atop the brain stem
What is the cerebrum?
The cerebrum is the uppermost part of the brain. It contains two hemispheres split by a central fissure
What does the diencephalon consist of?
thalamus(x2) and hypothalamus
What are the different parts of the brainstem?
Midbrain (mesencephalon), Pons (metencephalon), Medulla (myelencephalon)
What does the medulla become as it passes through foramen magnum?
spinal cord
where is the cerebellum found?
behind brainstem
Describe the axis of the brain.
neuroaxis flexes at the midbrain, therefore longitudinal axis of the cerebrum runs from frontal to occipital lobe.
Longitudinal axis of the brainstem and spinal cord runs parallel to these structures.
What are the general functions of the midbrain?
Eye movements and reflex responses to sound and vision.
What are the general functions of the pons?
Involved in feeding ans sleep
Which cranial involved in feeding arises from the pons?
Trigeminal nerve (Mandibular branch innervates muscles of matication)
What are the general functions of the medulla?
Contains the cardiovascular and respiratory centres. Contains major motor pathway.
What are the motor pathways in the medulla within?
Medullary pyramids
What is decussation?
The action of crossing (as of nerve fibers) especially in the form of an X
Give 2 examples of decussation.
Optic chiasm, fibres of the medullary pyramids
Define sulcus.
A groove or furrow in the brain separating adjacent gyri.
Define gyrus.
A ridge or fold in the brain
Why does the brain contain gyri and sulci?
to increase surface area to pack more neurones inside in a fixed volume of skull
Define fissure.
A large crack or split between adjacent large areas of the brain.
What is the name of the fissure where the falx cerebri run and splits the two hemispheres?
longitudinal fissure
What is the name of the fissure where the tentorium cerebelli run?
lateral fissure
Where is the grey matter found?
in cortex and area of thalamus
What does grey matter have a high density of and why?
have a high density of unmyelinated cell bodies as it is where sensory info needs to reach to be consciously perceived and the conscious decision to move body originates at the level of the cortex (motor)
What is white matter?
White matter forms the bulk of the deeper parts of the brain. It consists of glial cells and myelinated axons that connect the various grey matter areas.
What are the roles of thalamus and hypothalamus?
The thalamus acts as a relay station for sensory information form the head and neck region.
The hypothalamus is responsible for the regulation of certain metabolic processes. It’s involved in the synthesis of hormones.
What are the 4 lobes of the cerebrum?
- Frontal
- Parietal
- Occipital
- Temporal
Explain how the different lobes of the brain are separated from one another
The temporal lobe and the parietal lobe are separated using the lateral sulcus.
The central sulcus is used to separate the frontal and parietal lobes.
The parieto-occipital sulcus is used to separate the occipital lobe from the rest of the brain.
What is the corpus callosum?
This is a large band of nerve fibers that joins the two hemispheres of the brain allowing communication between the hemispheres
What do the ventricles contain?
CSF
What separates the two ventricles?
septum pellucidum
Define the following terms:
- Dorsal
- Caudal
- Ventral
- Rostral
- Dorsal = superior
- Caudal = posterior
- Ventral = inferior
- Rostral = anterior
What are the functions of the frontal lobe?
Voluntary motor control - Speech production - Social behaviour - Impulse control - Higher cognition (planning, thinking)
What are the functions of the parietal lobe?
- Somatosensory perception
- Spatial awareness
What are the functions of the temporal lobe?
Language
- Emotion
- Long-term memory
- Sense of Smell
- Hearing
- Taste
What are the functions of the occipital lobe?
- Visual perception
What are the functions of the cerebellum?
- Co-ordination and motor learning
What is the uncus? Determine its position and function in the brain
The uncus is a structure that lies at the most medial aspect of the temporal lobe and constitutes a large part of the primary olfactory area.
It has a relationship with the tentorum cerebelli of the brain.
What effect can an increase in intracranial pressure have on the uncus and any surrounding structures?
As the uncus has a close relationship with the tentorum cerebelli if there’s an increase in intracranial pressure the uncus can be pushed into the tentorial notch resulting in uncal herniation.
The uncus is found close to the cranial occulomotor nerve, therefore if it herniated it can push against this nerve resulting in symptoms developing.
What is the primary motor cortex and where is it located?
- located on the precentral gyrus
- conscious part of brain that makes volantary decisions to perform a particular motor action
What is the primary somatosensory cortex and where is it located?
- located on post central gyrus
- important in receiving and becoming consciously aware of somatic sensory information - all senses apart from special senses
Define homunculus
different parts of the body are represented by different points over the surface of the cortex
describe the topographical representation of the body in the primary motor cortex
At the primary motor cortex, motor representation is orderly arranged (in an inverted fashion) from the toe (at the top of the cerebral hemisphere) to mouth (at the bottom) along the precentral gyrus
limbs on most medial aspect and head and neck structures on most lateral aspect
describe the topographical representation of the body in the primary somatiosensory cortex
same as primary motor cortex in terms of how specific parts of the body are matched to specific regions of the area of cortex but certain parts of the body e.g. fingertips, tongue, lips have a greater degree of representation in the cortex
describe the uni cortical control of spinal nerves
Pathways connecting primary motor cortex (on one side) with spinal nerves controlling the limbs (on one side)
• Decussate (cross) to the opposite side at the level of the lower medulla
• Cortical control of limb movement is from one primary motor cortex, which is contralateral
this means that the PMC in one half if the hemisphere is responsible for motor control in the contralateral side of body
Describe the relationship between the motor cortex and cranial nerves innervating muscles of the head and neck
Pathways connecting primary motor cortex (on one side) with cranial nerves controlling the muscles of face/neck (on one side)
• Decussate (cross) to the opposite side at the level the nuclei onto which they communicate
• Cortical control of muscles is from one primary motor cortex, which is contralateral
• BUT!!!
• Most cranial nerves (not all!) also have cortical input from the ipsilateral cortex (a ‘back-up’)
