Download This week`s lab will focus on the central nervous

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.
Materials
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Anatomical models of central nervous system-specifically brain
Sheep brain specimens
Dissection kits and trays
Pre-Lab Evaluation Questions
The pre-lab evaluation questions must be answered prior to lab and demonstrated
to your lab instructor. You must read through the assigned chapter readings, lab
introduction, objectives, overview and procedure to answer these questions.
Please cite your work for any reference source you utilize in answering these
questions.
1. Compare and contrast the lobes of the cerebrum specifically their overall
function and location.
2. Compare and contrast Wernicke’s area and Broca’s area, specifically the
location, function and dysfunction that would occur with damage to that
region.
3. Explain the role of the cerebellum in normal skeletal muscle movement.
4. The limbic system is a diffuse network of structures in the brain. In your
own words, what is the overall function of the limbic system? What role do
the following regions of the brain have: thalamus, hypothalamus and
hippocampus and amygdala?
5. In your own words, explain the flow/movement of cerebral spinal fluid (CSF)
in the CNS. What are the functions of the CSF?
Part 01 Procedure: Brain Dissection of Sheep
1. “Appendix A”, contains the anatomical structures that will be identified in the
sheep brain dissection. These structures may also have to be identified on
your lab final examination.
2. Utilizing the “Rasmussen Lab Dissection Guide”, follow the directions and
figures under Topic 04: Brain Dissection of Sheep.
Part 02 Procedure: Case study of the CNS
1. Please read the case study handout and work with your lab partners on
answering the following questions:
Case Study A:
Case Study B:
Two point discrimination L/R:
Deep tendon reflexes L/R:
Babinski reflex L/R:
Blood pressure:
Diagnosis (be specific):
Causes/Types:
What side of the brain is being affected and why?
What is the difference between ischemia and infarct (infarction)?
If the next day in the hospital, Samuel was still having extreme
difficulty moving and sensation awareness in his right arm and leg, what
specific region of the brain would be affected?
If the next day in the hospital, Samuel was still having difficulty with
his vision, what specific region of the brain would be affected?
If the next day in the hospital, Samuel’s personality changed
drastically (for example from normally being happy and funny to being angry
and violent), what specific area of the brain would be affected?
If the next day in the hospital, Samuel was having a difficult time
answering questions/directions posed to of him, what specific region of the
brain would be affected? For example, if Samuel was shown a picture of a
sailboat and when asked if he knew what it was, he shook his head yes but
when he tried to say, “sailboat” he had a difficult time being able to articulate
the word.
If the next day in the hospital, Samuel was having a difficult time
understanding questions/directions posed to him, what specific region of the
brain would be affected? For example, if Samuel was asked how he was
doing today and he responded, “The sky is the color of the rainbow” with
little, if any slurring of speech.
Will Samuel recover from this occurrence with no residual effects or could
there be complications?
How does the term neuroplasticity relate to Samuel’s condition and
recovery?
Case Study C:
Post-Lab Evaluation Questions
The post lab evaluation questions must be completed prior to your submission of
the lab. Answers for these questions will be derived from the lab protocol, the
weekly concepts associated with the lab and possibly research content from the
book and/or online resources.
Please cite your work for any reference source you utilize in answering these
questions.
1. Describe at least two interesting experiences/knowledge gained from the
sheep brain dissection.
2. Compare and contrast the spinothalamic spinal cord tract and the
corticospinal tract along with the complications that could occur if any
damage occurs with them.
3. Briefly explain the role of the meninges and the three layers that it is
composed of. Compare and contrast the procedures of a lumber puncture
and an epidural.
4. In your own words, describe the role and significance of the blood brain
barrier. What are some “items” that can pass easily through it? What are
some “items” that cannot pass through it?
5. In your own words, how would you describe the function and role of the
spinal cord? What function does the grey and white matter have in the spinal
cord? What role do spinal tracts have within the spinal cord? Lastly, what’s
the difference between the terms- ipsilateral and contralateral regarding the
spinal cord?
Appendix A
Anatomical Points of the Sheep and Human Brain to Identify
External Examination
 Cerebrum
o Frontal lobe
o Parietal lobe
o Temporal lobe
o Occipital lobe
 Cerebellum
 Brain stem
o Pons
o Medulla oblongata
 Gyri
 Sulci
 Longitudinal fissure
 Mammillary bodies
 Optic tract/nerve
 Olfactory bulbs/tract
Mid-Sagittal Examination
 Cerebrum
o Corpus callosum
 Cerebellum
o Arbor vitae
 Brain stem
o Pons
o Medulla oblongata
 Pineal gland
 Thalamus
 Hypothalamus
 Pituitary gland (may not be present)
 Lateral ventricle
 Third (III) ventricle
 Fourth (IV) ventricle
 Cerebral aqueduct
Neural Tissue Examination
 Grey matter
 White matter
 Cerebral cortex