Download lab 8: central nervous system

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