Brain and Cranial Nerves SI Worksheet Part I PDF

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KIN 2500 – Human Anatomy The Brain

SI: Matt Landry [email protected]

Major Parts of the Brain  The brain is composed of four major components: o Cerebrum o Cerebellum o Diencephalon (hypothalamus and thalamus) o Brainstem (midbrain, pons, medulla oblongata) Cranial Meninges  Cranial meninges are three connective layers that o Protect blood vessels that supply the brain o Separate the soft tissue of the brain from the bones of the cranium o Contain and circulate the cerebrospinal fluid  The pia mater is the innermost cranial meninges. It is a thin layer of areolar connective tissue that is highly vascularized and tightly adheres to the brain.  The arachnoid mater lies external to the pia mater. It is a delicate web of collagen and elastic fibers. o Immediately deep to the arachnoid mater is the subarachnoid space.  The dura mater is an external tough, dense irregular connective tissue layer composed of two fibrous layers. It is the strongest of the three layers. o Between the arachnoid mater and the overlying dura mater is the subdural space. o It is composed of two layers:  Meningeal (deepest layer)  Periosteal (superficial layer) o The dura mater and the bones of the skull may be separated by the epidural space, which contains arteries and veins that nourish the meninges.  Review of Layers and Spaces (Deep to Superficial): Pia Mater, Subarachnoid space, arachnoid mater, subdural space, dura mater (meningeal and periosteal layer), epidural space, cranial bones  Cranial Dural Septa o The meningeal layer of the dura mater extends as flat partitions into the cranial cavity in 4 locations called the cranial dural septa. o The falx cerebri is the largest of the four dural septas. It separates the hemispheres of the cerebrum. o The tentorium cerebelli is a horizontal fold of the dura mater that separates the cerebrum from the cerebellum o The falx cerebelli is the vertical partition that separates the hemispheres of the cerebellum

KIN 2500 – Human Anatomy The Brain

SI: Matt Landry [email protected]

o The smallest of the dural septa is the diaphragm seliae, which forms a “roof” over the sella turicica of the sphenoid bone. Brain Ventricles  Ventricles are cavities or expansion within the brain that are continuous with one another as well as with the central canal of the spinal cord.  There are four ventricles in the brain: o Two lateral ventricles in the cerebrum  They are separated via the septum pellucidum o The third ventricle within the diencephalon  The lateral ventricles communicate with the third ventricle via the interventricular foramen. o The fourth ventricle is located between the pons/medulla and the cerebellum.  A narrow canal called the cerebral aqueduct passes through the midbrain and connects the third and fourth ventricle.  It merges with the central canal. Cerebral Spinal Fluid  A clear, colorless liquid that circulates in the ventricles and subarachnoid spaces. CSF preforms several important functions: o Buoyancy o Protections o Stability  Formation of CSF o CSF is formed by the choroid plexus in each ventricle. It is composed of ependymal cells and the capillaries that lie within the pia mater.  CSF Circulation o Put the following terms in order of CSF starting with production of CSF in the choroid plexus in each ventricle.  . Cerebral aqueduct b. Lateral ventricles c. Subarachnoid space d. Lateral and medial apertures e. Third ventricle f. Venous blood flow g. Fourth ventricle h. Interventricular foramen i. Arachnoid villi of the dura venous sinuses. o Correct Order: B, H, E, A, G, D, C, I, F o Excess CSF is continuously removed from the subarachnoid space so the fluid does not accumulate. The Cerebrum

KIN 2500 – Human Anatomy The Brain

SI: Matt Landry [email protected]

The cerebrum is the location for conscious thought processes and the origin of all complex intellectual functions  The surface of the cerebrum is covered by elevated ridges called gyri. Adjacent ridges are separated by shallow sulci or grooves called fissures Cerebral Hemispheres  The cerebrum is composed of two halves, called the left and right cerebral hemispheres  The paired hemispheres are separated by a deep longitudinal fissure that extends along the midsagittal plane.  A large tract of white matter called the corpus collosum connects the hemispheres (viewable in a midsagittal view). It’s function is to allow communication between the two hemispheres.  Three points should be kept in mind with respect to the cerebral hemispheres. o The two hemispheres appear as anatomic mirror images, but they display some functional differences termed, hemispheric lateralization o Due the decussating of pyramids the cerebral hemispheres receive their sensory information from and project motor commands to the opposite side of the body.  The right central hemispheres controls the left side of the body Lobes of the Cerebrum  Each cerebral hemisphere is divided into five anatomically and functionally distinct lobes. o The frontal lobe lies deep to the frontal bone and forms the anterior part of the cerebral hemisphere  This lobe ends posteriorly at a deep groove called the central sulcus, which separates it from the parietal lobe.  The inferior border of the frontal lobe is marked by the lateral sulcus, which separates the frontal and parietal lobes from the temporal lobe.  This lobe is primarily concerned with voluntary motor functions, concentration, verbal communication, decision making and planning, and personality.  An important anatomic feature of the frontal lobe is the precentral gyrus. o The parietal lobe lies internal to the parietal bone and forms the superoposterior part of each cerebral hemisphere. 

KIN 2500 – Human Anatomy The Brain

SI: Matt Landry [email protected]

This lobe terminates anteriorly at the central sulcus and posteriorly at the parieto-occipital sulcus and laterally at the lateral sulcus.  This lobe is involved with general sensory functions, such as evaluating shape and texture of objects being touched  An important anatomic feature of the parietal lobe is the postcentral gyrus. o The temporal lobe lies inferior to the lateral sulcus and underlies the temporal bone.  This lobe is involved with hearing and smell o The occipital lobe forms the posterior region of each hemisphere and immediately underlies the occipital bone.  This lobe is involved with processing incoming visual information and storing visual memories o The insula is a small lobe deep to the lateral sulcus.  This lobe is involved with interoceptive awareness, emotional responses, empathy, and interpretation of taste.  Functional Areas o Three categories of functional areas are recognized:  Motor areas that control voluntary motor functions  Sensory areas that provide conscious awareness of sensation  Association areas that primarily integrate and store information. o Functional areas of the brain can be visualized by a distorted image called a homunculus to reflect the amount of cortex dedicated to the motor activity of each body part. o One functional region is Wernicke’s Area which is located within the left hemisphere overlapping the parietal and temporal lobes.  This region is responsible for recognizing, understanding and comprehending spoken or written language Central White Matter  The central white matter lies deep to the gray matter and is composed of primarily myelinated axons. o Association Tracts connect different regions of the cerebral cortex within the same hemisphere. o Commissural Tracts connect corresponding lobes of the right and left hemispheres. o Projection Tracts connect cerebral cortex in the diencephalon, brain stem, cerebellum, and spinal cord. Cerebral Nuclei 

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SI: Matt Landry [email protected]

The cerebral nuclei (aka basal nuclei) are paired, irregular masses of the gray matter buried deep within the central white matter. Inferior to the floor of the lateral ventricle. The C-shaped caudate nucleus has an enlarged head and a slender, arching tail that parallel the swinging curve of the lateral ventricle. o The function of this region is to produce a rhythm when we’re walking The putamen and the globus pallidus are two masses of gray matter. They combine to form the lentiform nucleus. o The putamen functions in controlling, muscular movement at the subconscious level o The globus pallidus both excites and inhibits the activities of the thalamus to control and adjust muscle tone. Together the caudate nucleus, the putamen, and the globus pallidus form the corpus striatum The amygaloid body is an expanded region at the tail of the caudate nucleus. o The function of this region is to participate in the expression of emotions, control of behavioral activities, and the development of moods The colostrum is a thin sliver of gray matter. It processes visual information at the subconscious level....