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Biology 143 Lab 8 8-1 LAB 8: CENTRAL NERVOUS SYSTEM This lab examines the tissues of the nervous system: both functional and supportive. You will also examine the gross anatomy of the central nervous system. i.e. brain and spinal cord in detail. Prelab • • • • Fill in blanks on p. 1, 2, 3, 8-16 Label the diagrams on p 2, 7 and 16 Complete the table on p. 4 Draw a section through a nerve on p. 3 Objectives 1. Identify the various structures of the brain and spinal cord and recognize these structures in specimens and models 2. Know the function of the parts of the brain and spinal cord 3. Know the structure of a nerve, the various types of cells that make up nerve tissue and their functions; recognize these in a microscope slide STATION 1 PART I. NEURAL TISSUE A. SUPPORT CELLS (neuroglia) 1. Neuroglia in CNS Examine the slide of astrocytes and using your text record the functions of each of the following neuroglial cells: • astrocytes ____________________________________________________ • oligodendrocytes____________________________________________________ Describe the "Blood Brain Barrier” _________________________________________ ______________________________________________________________________ 2. Neuroglia in PNS Give the location and functions of the following neuroglia: • Schwann cells____________________________________________________ • satellite cells ____________________________________________________ Camosun College 2008 Biology 143 B. Lab 8 8-2 NEURONS What is the general function of a neuron? ________________________________________ Describe the specific functions of the 4 types of neurons and indicate whether they function as motor neurons, sensory neurons, or interneurons : • Anaxonic __________________________________________________________ • Unipolar __________________________________________________________ • Bipolar __________________________________________________________ • Multipolar __________________________________________________________ Observe the giant multipolar neurons slide and note the actual appearance of these cells. Label the multipolar neuron in the space below with the following: dendrites, axon, axon hillock, myelin sheath (Schwann cell), Nodes of Ranvier (myelin sheath gaps), cell body, nucleus, terminal arborizations (telodendria), synaptic knobs (terminal boutons). A cluster of neuron cell bodies in the PNS is known as a ____________________________ Camosun College 2008 Biology 143 Lab 8 8-3 C. NERVE STRUCTURE A nerve is basically a bundle of axons. Nerves are part of the PNS. In this lab you will study some of the nerves associated with the brain (the cranial nerves). Peripheral nerves will be studied in more detail in the lab next week. Study the medullated nerve slide (c.s.) and observe the epineurium, perineurium and endoneurium. What general type of tissue forms these 3 partitions? _____________________________ Sketch and label the parts of a nerve c.s. in the space provided below: Camosun College 2008 Biology 143 Lab 8 8-4 STATION 2 PART II : THE BRAIN A. MAJOR REGIONS There are 6 major divisions of the adult brain as outlined in the table below. Complete the table by filling in the key functions of each division. Locate the major regions on the model of the human brain. MAJOR DIVISION FUNCTIONS cerebrum thalamus diencephalon hypothalamus midbrain pons medulla oblongata cerebellum Examine the model of the human brain. Locate the structures labeled on the diagrams of the human brain and sheep brain (p 5 - 7). Camosun College 2008 Biology 143 Lab 8 SHEEP BRAIN (dorsal and ventral views) Camosun College 2008 8-5 Biology 143 SHEEP BRAIN (sagittal section) Camosun College 2008 Lab 8 8-6 Biology 143 HUMAN BRAIN Camosun College 2008 Lab 8 8-7 Biology 143 Lab 8 8-8 STATION 3 Examine the coloured brain model and locate the following CEREBRUM The cerebrum is composed of an outer layer of gray matter, the cerebral cortex; underlying white matter - myelinated axons - called tracts: and basal or subcortical nuclei - groups of cell bodies (hence gray matter) found deep to the tracts. 1. surface features Note the ridges are called gyri (singular - gyrus) while the depressions or furrows are called sulci (singular = sulcus). Deep sulci are called fissures. Identify the following on the model: • longitudinal fissure • lateral sulcus (or fissure) • central sulcus (or fissure) • precentral gyrus (primary motor cortex) • postcentral gyrus (primary sensory cortex) 2. lobes Note the lobes of each cerebral hemisphere. Indicate the main function of each. • frontal lobe ____________________________________________________ • temporal lobe ____________________________________________________ • parietal lobe ____________________________________________________ • occipital lobe ____________________________________________________ The longitudinal fissure separates what 2 lobes? _________________________________________ The region anterior to the central sulcus is the_________________________________ The region posterior to the central sulcus is the_________________________________ The region inferior to the lateral sulcus is the __________________________________ Does the superficial cortex consist of gray or white matter ________________________ NOTE: locate any additional structures you have labeled in the brain diagrams Camosun College 2008 Biology 143 Lab 8 8-9 STATION 4 Examine the frontal sections of the human brain, and locate the following. 3. basal nuclei The basal nuclei comprise several bodies of gray matter that lie deep within the white matter of the cerebral cortex. The basal nuclei are visible on the 12 part coronal (frontal) brain sections and of course in your text. Functions ______________________________________________________________ ______________________________________________________________________ 4. central white matter Locate the following prominent tracts of white matter in the coronal sections of the brain and classify each tract by fiber type • corpus callosum communicates between ______________________________ • fornix communicates between _______________________________________ CONSIDER: How does the relative size of the cerebral hemispheres compare in sheep and human brains and what is the significance of this difference? _________________________________________________________________________ Camosun College 2008 Biology 143 Lab 8 8-10 STATION 5 C. DIENCEPHALON Locate the following: 1. thalamus Consists of a right and a left mass of gray matter, each forming one wall of the third ventricle. The intermediate mass (visible in a midsagittal section through the brain) connects the right and left thalamic masses. 2. hypothalamus – is located inferior to the thalamus. This is the main visceral control center of the brain. List 8 functions of this structure: ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ 3. pituitary gland (hypophysis) This endocrine structure may be missing from the models and the sheep brain; it is best seen in the midsagittal section model of head (‘Prince Charles’ model) location _____________________________________________________________ function_____________________________________________________________ NOTE: the pituitary sits in the sella turcica on the superior surface of the sphenoid bone 4. pineal body (a portion of the epithalamus) location _____________________________________________________________ function_____________________________________________________________ Camosun College 2008 Biology 143 Lab 8 8-11 D. MIDBRAIN (mesencephalon) The midbrain contains nuclei which process visual and auditory information and generate reflexive responses to these stimuli. Using the ‘midbrain on a stick’ model, locate the following structures: • corpora quadrigemina Derive the meaning of this term_____________________________________________ superior colliculi (pair) function:__________________________________ inferior colliculi (pair) function:__________________________________ E. PONS AND CEREBELLUM (metencephalon) Locate these structures on the models of the human brain and the sheep brain. 1. pons Describe the location of the pons relative to the cerebellum: ______________________________________________________________________ 2. cerebellum Note there is a right and left cerebellar hemisphere separated by a narrow band called the vermis (‘worm’) and a cortex with folds or folia. Is the gray matter superficial or deep to the white matter of the cerebellum? ___________________________________ Examine a sagittal section through a cerebellar hemisphere. Is the arbor vitae made of white matter or gray matter? ___________________________________ What is the main function of the cerebellum? ______________________________________________________________________ F. MEDULLA OBLONGATA (myelencephalon) Locate this structure on the models of the human brain and the sheep brain. The medulla oblongata connects what 2 structures of the CNS? Connects ___________________________ to ___________________________________ Camosun College 2008 Biology 143 Lab 8 8-12 STATION 6 PART III: VENTRICLES OF BRAIN Observe the model of the brain ventricles, and locate the brain ventricles as you examine the models of the human brain and the sheep brain. Identify the 4 ventricles and describe what structures of the brain each passes through • lateral ventricles (1st and 2nd)______________________________________________ • 3rd ventricle __________________________________________________________ • 4th ventricle __________________________________________________________ These cavities of the brain are filled with _____________________________________ and lined by special ciliated cells, the ___________________________________ Locate each of the following and indicate which ventricles each structure connects: • interventricular foramen connects ___________________ to ___________________ • cerebral aqueduct connects __________________ to ____________________ passes through ___________________________________ The 4th ventricle is continuous with what structure in the middle of the spinal cord? _________________________________________ The 4th ventricle of the brain also connects with the subarachnoid space which circulates CSF around the brain. Between what 2 meninges does the subarachnoid space lie? between __________________________and _________________________________ Identify the choroid plexus in the sagittal sections of the brain. CSF is produced by this structure. Of what does it consist? ______________________________________________________________________ Camosun College 2008 Biology 143 Lab 8 8-13 PART IV : MENINGES Recall, the brain and spinal cord are covered by three concentric layers of connective tissue called the meninges. Locate the cranial meninges in the specimens and models provided Name the three meninges as described below: 1. _______________________ Tough, fibrous, outermost covering over the brain and spinal cord. In certain areas, it consists of layers enclosing dural sinuses. 2. _______________________ A delicate, web-like membrane separated from the pia mater by a space called the subarachnoid space which contains cerebrospinal fluid. Blood vessels to and from the brain cross through this space as do beams of connective tissue called trabeculae. 3. ________________________ Delicate, innermost membrane conforming to the contours of the brain (and spinal cord) - does not show on models but appears as "saran wrap" on sheep brain following removal of the outer meninges Identify the 3 meninges in the split brain model and the model of the spinal cord cross section when you have the opportunity to view these models NOTE: at 4 locations, the cranial dura mater extends deep into the cranial cavity providing support to the brain. Identify the following on the cranial meninges model and describe the location of each: • falx cerebri • tentorium cerebelli ____________________________________________________ • falx cerebelli Camosun College 2008 ____________________________________________________ ____________________________________________________ Biology 143 Lab 8 8-14 STATION 7 PART VI:. SPINAL CORD 1. General structure On the “loin roast" model, identify the following structures: • spinal nerve roots • cauda equina - descending lumbar and sacral nerve roots • cervical & lumbar enlargements • foramen magnum • conus medullaris • filum terminale - What is its function? ___________________________________ CONSIDER: Where does the spinal cord begin? __________________________________ and end? ____________________________________ 2. Detailed microstructure Using the spinal cord X section model, identify the following: a) grey matter - ("H" shape) • posterior grey horns • lateral grey horns • anterior grey horns • gray commissure What type of tissue is this? ________________________________________________ Which horns contain somatic motor nuclei? ___________________________________ Which horns contain somatic sensory nuclei? Camosun College 2008 _____________________________ Biology 143 Lab 8 b) white matter • posterior white columns (funiculi) • lateral white columns (funiculi) • anterior white columns (funiculi) • anterior median fissure • posterior median sulcus What type of tissue is this? _____________________________________________ The white columns contain ascending and descending tracts. Do ascending tracts carry sensory or motor info? __________________________ Do descending tracts carry sensory or motor info? __________________________ What is the difference between a fissure and a sulcus? _________________________________________________ In the space provided below, sketch a transverse section through the spinal cord and label the gray horns and white columns as described above: Camosun College 2008 8-15 Biology 143 Lab 8 8-16 STATION 8 Spinal cord cross section Label the following diagram and identify the structures indicated below on the model: 3 spinal meninges, body of vertebra, spinous process, transverse process, subarachnoid space, subdural space, epidural space, dorsal root, ventral root, dorsal root ganglion, central canal THINK! What type of vertebra is represented? ___________________________________ CONSIDER: From what area of the meninges is CSF drawn (eg. for diagnostic purposes? ___________________________________ Camosun College 2008