BSC 2346 Module 07 Lab Worksheet: Central Nervous System- Sheep Brain Dissection.Introduction
This week’s lab will focus on the central nervous system
... [Show More] (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 [Show Less]