A&P 1 Brain & Cranial Nerves Guide #1 - Pre-Lab Exercises In this "Pre-lab Guide", we will be looking at the brain & cranial nerves. This should be done before lab, so we don't waste time in lab! This guide should only be attempted after reading the correct sections in either the lab or lecture book, or watching any videos that have been assigned. The Steps found in this first "Pre-lab Guide" do NOT have to be done in the order they are found. However, please do all the questions within a step before moving on to another step!
Development of the Brain The brain consists primarily of nerve tissue, including billions of neurons and their associated neuroglia cells. One thing that makes the brain different from the spinal cord is that it is where we do complex analysis, forming thoughts of a situation, and identifying complex patterns. It is also where we find consciousness and emotions, as well as control memory, learning, and personality.
Images show different things on different sides
Brain is an enlargement at the anterior end of the CNS, adapted to receive sensory input, process the information, and develop a motor output (that is, a response to the stimulus). The brain has a rather simple anatomy. Early in the development of an embryo, the nervous system originates as a tube. The neural tube is hollow, with a canal running down its length.
The anterior portion of that tube, which will become the brain, has a series of enlargements, each with a specific job: the forebrain, the midbrain, and the hindbrain. The hollow are inside widens, and becomes the VENTRICLES.
In adult humans (and other mammals) the linear relationship of forebrain to diencephalon to brain stem is no longer as obvious. This is due to the massive LATERAL AND POSTERIOR growth and development of the cerebrum, which dominates the brain in terms of both anatomy and physiology.
There are 4 commonly referred to subdivisions of the adult brain: A. Cerebrum (telencephalon) B. Diencephalon C. Brain Stem D. Cerebellum
Of course, all the subdivisions can be further subdivided into more specific regions. A. Cerebrum (telencephalon) 1. Cerebral cortex (outer gray matter) 2. Inner white matter (inner tracts, nuclei, etc.) B. Diencephalon 1. Epithalamus 2. Thalamus 3. Hypothalamus C. Brain stem 1. Midbrain 2. Pons 3. Medulla oblongata D. Cerebellum 1. Arbor vitae (inner white matter) 2. Folia (outer gray matter)
And of course, reach sub-region has individual structures you need to know:
Cerebrum has 2 hemispheres Sulci & Gyri Everything anterior = motor output Everything posterior = sensory Stick to your word list!
In-lab guide includes dissections Clean Up Procedures
STEP 1. Study the outer brain #1 Get everything you need Read Me Get a dissecting pan, 1 scalpel, 1 pair scissors, and some latex-free surgical gloves. Your group should have the following in front of you: 1. Human Brain Model 2. Sheep Brain - Whole, with Dura Mater (you will be dissecting this!) 3. Sheep Brain Whole - without dura mater (you will not be dissecting this) 4. Sheep Brain Frontal Section Human brain model Sheep brain with meninges Sheep brain without meninges Sheep brain - Frontal section We will be comparing these four at the same time.
First compare with meninges/without meninges
You will be comparing things. Such as brain with meninges versus brain without meninges:
Commissures are large chunks of white matter that go between hemispheres Hypothalamus with optic chiasma
Then compare sheep brain to models/images
You will be dissecting the brain with meninges. Use your scalpel like a butter knife! Not a saw! You are responsible for all terms on your wordlist, whether or not they are covered in the following description Special Ethmoid bone instruction : Ask instructor if necessary Determine if your specimen still has a part of the ethmoid bone attached on the anterior frontal lobe. If the bone is present, slip a blunt probe between the bone and the dura to carefully separate the bone away from the specimen. Then, using your scissors, snip away any attached dura. Examine the removed ethmoid bone and identify the cribriform plates, where the olfactory bulbs were sitting, and the crista galli: crest of bone where that serves as the surface of attachment of the meninges. Also, the optic nerve may still be attached to 2 large fat bodies these are 2 pads that sit behind your eyeball. Using the scissors, cut the optic nerves to remove the pads, trying to get the brain to look like the one in the image below
Clean Up Procedures 1. Replace the following back into the buckets from which they came: Sheep Brain Whole - without dura mater (you will not be dissecting this) Sheep Brain Frontal Section 2. Place the brain you dissected, and any parts, in the designated container. When you are ready, place your gloves in a regular trash can and NOT in the container with the dissected brains. 3. Take the dissection tray and all instruments to the sink to be washed. 4. Remove the pad from the dissection tray and wash them separately using the provided disinfectant and sponge. 5. Also spray the instruments with disinfectant and clean them using the provided toothbrushes. 6. Rinse the pad, dissecting tray, and all tools and place them in the drying tray. 7. Place the instruments SHARP END DOWN in the appropriate portion of the drying tray. 8. Spray down the area of the lab bench where the dissection was completed with disinfectant and dry using a paper towel.
The Cranial Nerves Some = mixed, others = sensory or motor only! For lab, know all 12 in order. Also, ID first 6, & # 10 off the model. Notice that I am only asking 1 off the brain stem, so if I point there, you know which one it is! X Vagus on Brainstem In Anatomy & Physiology class, you are going to hear a lot about the "vagal tone" of many visceral organs.
Look for trends among the cranial nerves, to help make your life easier. How many of the cranial nerves are involved with eye movement? List them: How many of the cranial nerves are involved with chewing, moving the tongue, or swallowing? Name them: How many are purely or mainly sensory? List their names here:
Check with your table Cranial Nerve Organization Table Mnemonic: Oh, oh, oh, to touch and feel very good velvet...ah, heaven Cranial Nerve: I Olfactory II Optic III Oculomotor IV Trochlear V Trigeminal VI Abducens Major Functions: Sensory only: smell Sensory only: vision Mainly Motor: eyelid and eyeball movement Mainly Motor: eyeball movement Motor & Sensory: chewing most face & mouth senses of touch & pain Mainly Motor: eyeball movement laterally More on next page
VII Facial VIII Vestibulocochlear (auditory) IX Glossopharyngeal X Vagus XI Accessory (spinal accessory) XII Hypoglossal Motor & Sensory: controls most facial expressions taste Mainly Sensory: hearing equilibrium sensation Motor & Sensory (only sense listed here): taste senses blood pressure Motor & Sensory: senses blood pressure slows heart rate stimulates most thoracic and abdominal visceral organs Mainly Motor: controls swallowing movements Mainly Motor: controls tongue movements
How many of the cranial nerves do you think have a completely obvious name, given their function? Below is a list of the nerves, plus a brief description of what their names mean (in mostly Latin). Place a check next to any name you think is obvious: I Olfactory - "of smell" II Optic - "of vision" III Oculomotor - "eye mover" IV Trochlear - "pulley" V Trigeminal - "3 bodies" VI Abducens - "to cause abduction" VII Facial - "of the face" VIII Vestibulocochlear - "from the vestibule and cochlea" IX Glossopharyngeal - "tongue and throat" X Vagus - "wandering" XI Accessory - "helper" XII Hypoglossal - "below the tongue"