Download Anatomy of the Brain: Structures, Functions, and Clinical Relevance and more Cheat Sheet Anatomy in PDF only on Docsity!
BIO 141
Lab 7: Brain Anatomy and Cranial Nerves Objectives
- Identify the major clinical divisions of the brain and its regions on a figure, model, human brain, and/or MRI scan of the brain.
- Identify the brain’s meninges, dural folds, and associated meningeal spaces on a figure, human brain, and/or MRI scans).
- Identify the cerebral hemispheres and listed components of the hemispheres on a figure, model, human brain specimen and or MRI scan of the brain.
- Identify the cerebellum and listed components of the cerebellum on a figure, model, human brain specimen, and/or MRI scan of the brain.
- Identify selected structures of the diencephalon on a figure, model, human brain specimen, and/or an MRI scan of the brain.
- Identify the major structures that compose the brainstem and identify selected structures of the brain stem on a figure, model, human brain specimen, and/or MRI scan of the brain.
- Identify the brain ventricles and connecting channels on a figure, model, human brain specimen, and/or MRI scan of the brain.
- Identify listed arteries that supply arterial blood to the brain on a model and/or angiogram and determine which cerebral artery is experiencing a cerebrovascular accident (CVA) when presented a patient scenario with a specific body deficit.
- Identify dural venous sinuses on a model or cadaver specimen. State what forms the walls of a dural venous sinus, what is normally located within the interior space, and identify and state into which vessel they ultimately drain.
- Name the twelve pairs of cranial nerves by name and number, describe a function of each nerve, and state which nerve is involved in a deficit. **Procedures by Objectives
- Identify the major clinical divisions of the brain and its regions on figure, model, human brain, and/or MRI scan of the brain.** The brain can be divided into different regions and is clinically organized as follows: o The cerebral hemispheres are two large, curved mushroom-like caps that rest on deeper brain structures. o The diencephalon , consisting of the thalamus and hypothalamus, is a portion of the brain sandwiched between the brainstem and the cerebrum. o The brainstem is a column-like continuation of the spinal cord after the spinal cord passes through the foramen magnum. The brainstem is the “stem” from which other brain structures emanate. o The cerebellum , which means “little brain,” is a brain structure sandwiched between the posterior cerebral hemispheres and the brain stem. However, it is only physically connected to the brain stem. Complete Exercise 1 in Canvas: Identify the labeled divisions of the brain on a figure of a sagittal section of the brain.
2. Identify the brain’s meninges, dural folds, and associated meningeal spaces on a figure, human brain, and/or MRI scans. Surrounding the central nervous system are three connective tissue layers, called the meninges (singular is meninx). Surrounding the meningeal layers are spaces named according to their location relative to the meninges. These spaces can be categorized as real space or potential. A real space contains something in it such as fluid or fat. A potential space lacks contents, which means the layers that form the boundaries of the space are in contact with each other. However, due to injury or pathology, the layers can be pushed apart by substances such as blood or CSF to create a real space. The meninges include: o The dura mater (from Latin meaning “tough mother”) is the thickest connective tissue layer surrounding the CNS. In the cranial cavity it consists of two layers: periosteal dura and meningeal dura. The periosteal dura is the superficial layer of the dura and is the periosteum of the bone forming the cranial cavity. This layer is not continuous with the dura surrounding the spinal cord. Because this layer is only present in the cranial cavity and is adhered to the bone, the epidural space in the cranial cavity is a potential space. Recall from the previous lab that the epidural space in the vertebral canal is a real space. The deep layer of the dura is the meningeal layer. This layer of the dura continues through the foramen magnum to surround the spinal cord. The two layers of dura are joined to each other as they surround most of the brain, but in specific regions, the meningeal dura separates from the periosteal dura to form folds that occupy large fissures. These folds of the dura mater create a double layer that divides particular regions of the brain. A dural (venous) sinus is an endothelial-lined vascular channel formed at the location where meningeal dura separates from periosteal dura. (There are two named dural sinuses that are exceptions to this description, and the entire channel is formed by meningeal dura.) The dural (venous) sinuses contain venous blood that is collected from cerebral and cerebellar veins. The drainage of venous blood will be presented in further detail in objective 9. Arachnoid villi are microscopic protrusions of arachnoid mater that penetrate the dura mater to reside within the dural venous sinus. They function as one- way valves to allow the cerebrospinal fluid (CSF) within the subarachnoid space to enter the venous circulation. o The dura mater also forms 3 folds which include: The falx cerebri is the double layer of meningeal dura present in the longitudinal fissure that separates the right and left cerebral hemispheres. The tentorium cerebelli is the double layer of meningeal dura present in the transverse fissure that separates the cerebral hemispheres from the cerebellum. The falx cerebelli is the double layer of meningeal dura present in the groove between the cerebellar hemispheres.
o Temporal lobe o Occipital lobe The shallow grooves on the surface of the hemispheres are called sulci. Many of the sulci are given specific names, we will focus on two. o The Central sulcus is a groove that extends from the longitudinal fissure to the lateral sulcus. It is the sulcus that separates the frontal lobe from the parietal lobe. o The Lateral sulcus is the sulcus that separates the temporal lobe from both the frontal lobe and parietal lobe. Fissures are deep grooves that separate large areas of the brain. o The longitudinal fissure is a deep groove that separates the right and left cerebral hemispheres. The falx cerebri, a large dural fold, is present in the longitudinal fissure. o The transverse fissure is a deep groove that separates the cerebrum from the cerebellum. The tentorium cerebelli, a dural fold, is present in the transverse fissure. The raised areas on the surface of the cerebral hemispheres are called gyri (singular: gyrus). Many of the gyri of the brain are given specific names; we will focus on two important gyri involved in conscious motor control and sensory perception. o The precentral gyrus lies immediately anterior to the central sulcus and is a component of the frontal lobe. The cortex of the precentral gyrus consists of neurons that control conscious skeletal muscle contraction. o The postcentral gyrus lies immediately posterior to the central sulcus and is a component of the parietal lobe. The cortex of this precentral gyrus consists of neurons that are involved in receiving sensory information from the body. Cerebral Cortex (gray matter): When the cerebrum is cut, the outer one-eighth inch thickness appears gray. This gray surface region, called the cerebral cortex, contains many neuron cell bodies (40% of total neuron mass). White matter: Deep to the cerebral cortex, the tissue of the hemisphere appears white. This region of white matter consists of bundles of myelinated axons. The main connection between the two cerebral hemispheres is an arch shaped band of white matter called the corpus callosum , which consists of about 100 million axons that connect corresponding areas of the hemispheres to each other.
4. Identify the cerebellum and listed components of the cerebellum on a figure, model, human brain specimen, and/or MRI scan of the brain. The Cerebellum is located posterior to the brainstem and separated from the cerebral hemisphere on its superior side by the tentorium cerebelli within the transverse fissure. Like the cerebrum, the cerebellum is separated into cerebellar hemispheres and consists of a cortex composed of gray matter that is highly folded. Functionally it plays a major role in coordinated muscular moments. o The cerebellar cortex is composed of many folds of gray matter that form gyri and sulci. o Arbor vita is the white matter of the cerebellum that has the appearance of a tree when cut in the midsagittal plane. Complete Exercise 4 in Canvas: Identify the labeled cerebral hemisphere structures on a figure of the brain.
Complete Exercise 5: Identify the labeled structures on a brain model. You will have to pull apart pieces of the brain model to find all the labels.
9. _____________________________
10. _____________________________
11. _____________________________
12. _____________________________
13. _____________________________
14. _____________________________
15. _____________________________
16. ____________________________
5. Identify selected structures of the diencephalon on a figure, model, human brain specimen, and/or an MRI scan of the brain. The diencephalon consists of several structures including the thalamus, hypothalamus, infundibulum and pineal gland. o The thalamus consists of paired rounded structures on either side of the midline sandwiched between the cerebral hemispheres and the midbrain. The rounded thalamic masses are joined at the midline by the interthalamic mass (adhesion). The thalamus is a large cluster of neuron cell bodies that functions primarily to relay sensory information to the postcentral gyrus. o The hypothalamus is located deep to the thalamus and forms the anterior region on the diencephalon. o The infundibulum (pituitary stalk) is an inferior extension of the hypothalamus consisting of axons whose cell bodies are located in the hypothalamus. The ends of the axons of the infundibulum terminate in the posterior pituitary gland. The Mammillary bodies are two rounded masses of gray matter that can be seen on the inferior side of the brain. They are surrounded laterally by the cerebral peduncles and anteriorly by the pituitary stalk. o The Pineal body (gland) is a small endocrine gland located in the midsagittal plane dorsal to the thalamus and superior to the corpora quadrigemina. The Pituitary gland is a spherical gland about the size of a pea attached to the distal end of the infundibulum. It is composed of two distinct lobes: the posterior pituitary and the anterior pituitary. Embryonically the two lobes are derived from different regions. The posterior pituitary is an extension of the hypothalamus and consists of the axonal endings of neurons whose cell bodies are in the hypothalamus. The anterior pituitary consists of clustered hormone producing cells that embryonically were derived from the roof of the mouth. The anterior pituitary does not contain neuron endings. Optic nerve, Optic tracts, Optic chiasm: All three structures are components of the visual pathway and are extensions of the diencephalon. The optic nerve consists of neurons that
7. Identify the brain ventricles and connecting channels on a figure, model, human brain specimen, and/or MRI scan of the brain. The brain ventricles are a series of interconnected cavities within the brain that contain a fluid called cerebrospinal fluid. All four ventricles multiple clusters of blood vessels covered by epithelial cells, called the choroid plexus that functions to produce cerebrospinal fluid, which is a filtrate of the blood. The CSF circulates throughout the brain by passing through channels that interconnect the ventricles. CSF ultimately flows out of the fourth ventricle to enter both the subarachnoid space and the central canal of the spinal cord. Ventricles o The lateral ventricles are slightly lateral to the midsagittal plane, and therefore are not visible in a midsagittal brain section but can be visualized by pushing a probe through the membrane (septum pellucidum) that separates them from each other. o The third ventricle is a narrow chamber between the thalamic masses and does lie in the midsagittal plane, so when the brain is bisected by an incision through the longitudinal fissure, the narrowness and the position of this chamber makes it difficult to see in a midsagittal view. o The fourth ventricle is located dorsal to the pons, anterior to the cerebellum, and superior to the medulla. It receives the flow of CSF from the third ventricle via the cerebral aqueduct. From the fourth ventricle CSF flows inferiorly into the central canal of the spinal cord or into the subarachnoid space by three openings. Connecting Channels o The cerebral aqueduct is a narrow channel that runs through the midbrain and allows CSF to flow from the third ventricle into the fourth ventricle. o Interventricular foramina are small channels that drain each ventricle allowing CSF to flow into the third ventricle. Complete Exercise 7, Part A in Canvas: Identify the labeled ventricles and channels on a figure of the brain ventricular system. Part B: Gray Ventricular System Model 1. _____________________________ 2. _____________________________ 3. _____________________________
4. _____________________________
5. _____________________________
Part C: Brain Model.
4. _____________________________
5. _____________________________
Complete Exercise 8: Identify the labeled structures on human brain specimens from the following views: superior view, inferior view, and midsagittal section. Part A: Superiolateral View Human Brain
1. _____________________________
2. _____________________________
3. _____________________________
4. _____________________________
5. _____________________________
6. _____________________________
7. _____________________________
8. _____________________________
9. _____________________________
10. _____________________________
11. _____________________________
Part B: Inferior View Human Brain
6. _____________________________
7. _____________________________
8. _____________________________
9. _____________________________
Part C: Midsagittal Section of Human Brain
9. _____________________________
10. _____________________________
11. _____________________________
12. _____________________________
13. _____________________________
14. _____________________________
15. _____________________________
Complete Exercise 9 in Canvas: Identify the labeled brain structures on MRI images.
8. Identify listed arteries that supply arterial blood to the brain on a model and/or angiogram and determine which cerebral artery is experiencing a cerebrovascular accident (CVA) when presented a patient scenario with a specific body deficit. The brain’s entire arterial blood supply is transported into the cranial cavity via two different vessels that are both paired: the paired vertebral arteries and the paired internal carotid arteries. o The right and left vertebral arteries branch from the subclavian arteries at the base of the neck. As the vertebral arteries traverse the neck in a superior direction toward the brain, they pass through the transverse foramina of cervical vertebrae. After passing
the body can also occur on the opposite side of the body from the vessel experiencing the stroke.
3. Middle cerebral artery (right and left) ∙ The right and left middle cerebral arteries are terminal branches of the internalcarotid arteries at the circle of Willis. ∙ The middle cerebral arteries branch in a lateral direction from the circle of Willis∙ They supply blood to the lateral portions of the frontal, middle, and temporal lobes of the brain. ∙ The middle cerebral artery is the most common site of a CVA. ∙ Partial weakness (hemiparesis) or paralysis (hemiplegia) of the face, upper,and lower extremity on the side opposite of the body from the vessel experiencing the stroke can result. In most cases the lower extremity is spared. Sensory loss to the face, upper extremity, and lower extremity on the opposite side of the body from the vessel experiencing the stroke can result. ∙In addition, speech impairments can result if the stroke occurs on the side of the body containing the speech centers, which is usually the left side for most people. 4. The posterior communicating arteries connect the posterior cerebral arteries to the middle cerebral arteries. 5. The anterior communicating arteries connect the left and right anterior cerebral arteries. 9. Identify dural venous sinuses on a model or cadaver specimen. State what composes the walls of a dural venous sinus, what is normally located within the interior space, and identify and state into which vessel they ultimately drain. Unlike other organs in the body, the brain’s venous drainage does not run parallel to the brain’s arteries. The cerebral and cerebellar veins drain venous blood into dural (venous) sinuses , which are endothelial lined channels within the dura mater. There are 6 paired and 4 unpaired named dural sinuses. Most of the dural sinuses (except two) are formed at the location where the meningeal dura separates from the periosteal dura. The venous blood within the dural (venous) sinuses drains through the system of sinuses and ultimately leaves the skull by draining into the internal jugular vein. The internal jugular vein begins at the jugular foramen of the skull and is continuous with the dural sinus that drains blood toward the jugular foramen. Complete Exercise 10: Identify labeled vessels and dural sinuses on figures and models. Part A in Canvas: Identify the labeled vessels and dural sinuses on a figure. This is a computer exercise Part B: Identify labeled vessels and dural sinuses on a model.
5. _____________________________
6. _____________________________
7. _____________________________
8. _____________________________
9. _____________________________
10. _____________________________
11. _____________________________
Part C in Canvas: Identify arteries supplying the brain on an MRA (magnetic resonance arteriogram) and determine which cerebral artery is experiencing a CVA when provided a patient scenario with a specific body deficit.∙
10. Name the twelve pairs of cranial nerves by name and number, describe a function of each nerve, and state which nerve is involved in a deficit. Cranial nerves are components of the PNS (except cranial nerve II) that connect directly to the brain, which differentiates them from spinal nerves that connect to the spinal cord. The Roman numerals are associated with each cranial nerve’s position along the longitudinal axis of the brain. You are asked to know the information in the following table. Table 1. The Cranial Nerves Cranial Nerve Name Function CN I Olfactory Nerve Sensory: smell (olfaction) CN II Optic Nerve Sensory: vision CN III Oculomotor Nerve Motor: eye movement and opening of eyelid CN IV Trochlear Nerve Motor: eye movement, superior oblique muscle CN V Trigeminal Nerve Sensory: face, mouth, and head Motor: muscles of mastication CN VI Abducens Nerve Motor: eye movement, lateral rectus muscle CN VII Facial Nerve Sensory: taste, anterior tongue Motor: facial muscles, facial expressions , closure of eyelid CN VIII Vestibulocochlear Nerve Sensory: equilibrium (vestibular portion) Hearing (cochlear portion) CN IX Glossopharyngeal Nerve Sensory: posterior tongue (taste) and throat Motor: Swallowing (pharyngeal muscles) and salivary gland secretions
- Which cranial nerve is affected if a patient has complete paralysis on one side of his/her face (Bell’s palsy)?
- Which cranial nerve is affected if a patient’s tongue deviates to one side when sticking out his/her tongue?
- Which cranial nerve is affected if a patient is unable to move his/her right eye to the right? (More details on eye movements will be covered in the next lab.)
- Which cranial nerve is affected a patient is unable to close his/her eyelid?
