Exam (elaborations) BSC 2346 (BSC2346) BSC 2346 Module 07 Lab Worksheet: Central Nervous System- Sheep Brain Dissection

BSC 2346 Module 07 Lab Worksheet: Central Nervous System- Sheep Brain Dissection.Introduction This week’s lab will focus on the central nervous system (CNS) and the identification of the anatomical structures that define the CNS. Objectives Objectives for this week’s lab include: 1) Demonstrate knowledge and understanding of specimen dissection, 2) Identification of gross anatomy of the sheep brain, and 3) Recognize gross anatomy of the CNS on pictures of human cadaver. Overview The CNS consists of the brain and spinal cord. The brain consists of the cerebrum, cerebellum, and brain stem. The cerebrum is divided into left and right hemispheres with frontal, parietal, temporal and occipital lobes within each hemisphere. The brain stem consists of the midbrain, pons, and medulla oblongata. Each region/component of the CNS has a specific function, for example, the occipital lobe allows for the function of vision. When viewing any aspect of the CNS including the spinal cord, you will notice grey and white sections referred to as grey matter and white matter. The grey matter is technically where the somas (cell bodies) of millions and millions of neurons are collectively found while the white matter is technically where the axons (remember the myelin sheaths) of millions and millions of neurons are collectively found. Basically, the grey matter consists of the somas of neurons that allow for the neural integration (decision making) and the white matter consists of myelinated axons that “transport” neural information from one region of the CNS or PNS to another region of the CNS and/or PNS. Remember, myelin is mainly composed of lipids (fats) giving it a white appearance. The cerebral cortex of the cerebrum is what many references refer to as “executive suite”, or “higher order” or even “the boss” as it involves the function of our conscious mind. Our ability to remember, communicate, initiate voluntary movement, perceive sensations, and be aware that “voice” in your head stems from the cerebral cortex function. The cerebral cortex is composed of grey matter on the outer layer of the cerebrum (technically only about 2-4mm thick) but accounts for 40% of the overall brain mass. That’s amazing! Internally, the brain has chambers or open spaces called ventricles that are filled with cerebral spinal fluid (CSF) that literally “baths” and surrounds the CNS including the spinal cord. The brain and spinal cord float within the CSF in the cranial and vertebral cavity. There are two lateral ventricles, a third ventricle and a fourth ventral within the brain. The fourth ventricle connects to central canal, which allows CSF to pass down and “bath” the spinal cord. The cerebellum plays an important function in our coordination; it receives neural information from a number of regions of the brain and body including cerebral cortex, brain stem, and sensory receptors within the body. It provides an unconscious ability to regulate timing and movement of skeletal muscle contraction allowing for smooth, coordinated and balanced movements including walking, driving, typing, and writing. A field sobriety test (drunk driving test) is largely testing the function of the cerebrum. Again, the function of the cerebellum is unconscious, meaning we have no conscious awareness of it. The brain stem contains nuclei centers that produce programmed, automatic functions vital for survival including various cardiovascular and respiratory controls, such as sneezing, and setting the respiration rate. It also serves as a pathway connecting the spinal cord and cerebellum to the cerebrum