Download Lecture 15: The Brain

Lecture 15: The Brain
M/O Chapters 15, 17
73. List the three primary brain vesicles and the five secondary brain vesicles, and identify the major areas
of the adult brain that arise from each region.
74. Correlate functions with each major area of the adult brain.
75. Identify the five lobes of the cerebral cortex and describe how the motor and sensory functions of the
cerebrum are distributed among the lobes.
76. Discuss the role of the corpus callosum in connecting the two halves of the cerebrum.
77. Describe the location and functions of the limbic system.
Embryological development of the brain
Neural tube
formation
Swelling of
cephalic end
(4 wks)
(4 wks)
Primary brain
Secondary brain
vesicles
vesicles
(4 wks)
(5 wks)
Mature brain structures
Adult brain functions
Secondary brain vesicles
Telencephalon
Bio 6: Human Anatomy
Mature brain structures Function(s)
Cerebrum
• Conscious thoughts (superficial); Memory and emotions (deep)
• Divided into right and left hemispheres separated by longitudinal
fissure
• Two hemispheres are connected by the corpus callosum
-Frontal lobe
• Anterior to the central sulcus, and superior to the lateral sulcus
• Includes precentral gyrus (anterior to central sulcus) which contains
the primary motor cortex.
• Functions include voluntary motor, personality, verbal
communication, planning and decision making.
-Parietal lobe
• Posterior to central sulcus, superior to lateral sulcus
• Includes postcentral gyrus (posterior to central sulcus) which includes
the primary somatosensory cortex
• Functions involve general sensory functions
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-Temporal lobe
-Occipital lobe
-Insula
Diencephalon
Epithalamus
Thalamus
Hypothalamus
Mesencephalon
Corpora quadrigemina
-Superior colliculi
-Inferior colliculi
Metencephalon
Pons
Cerebellum
Myelencephalon
Medulla oblongata
• Inferior to lateral sulcus.
• Involved in auditory and olfactory perception and memory.
• Posterior region
• Involved in processing visual information and storing visual
memories
• Deep to lateral sulcus
• Functions in memory and taste
• Includes the pineal gland, which produces melatonin and plays a role
in circadian rhythms and other rhythmic behaviors
• Has connections to the retina, and is thus affected by LIGHT!
• Gateway to the consciousness
• Filters sensory information to determine which info is worthy of
consciousness.
• Only smell is not processed through the thalamus
• Ultimately controls the autonomic nervous system (ANS)
• Ultimately controls the endocrine system (because it is connected to
the pituitary gland via the tiny infundibulum)
• Controls body temperature and is thus affected by pyrogens
(chemicals produced by an immune response that re-set the
hypothalamic thermostat!)
• Controls emotional behavior as part of the limbic system
• Controls food intake by initiating HUNGER sensations!
• Controls water intake by monitoring the solute concentration in blood
• The name means “4 brother bodies”
• Visual reflex center with explicit links to peripheral vision
• Auditory reflex center that enables you to turn quickly toward a loud
noise
• Contains centers that regulate rate and depth of breathing
• Bridges to cerebellum
• Coordinates complex motor activity
• Is capable of learning and can adjust a response without conscious
input.
• Sensitive to alcohol...(and underdeveloped in toddlers, which is why
drunk folk and toddlers walk in similar manners!)
• This is the reptilian brain with tracts to and from the higher brain
• Regulates the ANS, including heart rate and force of contraction,
blood pressure, and respiratory rate.
• Also involved in coughing, sneezing, salivating, swallowing, gagging
and barfing.
• Contains visceral motor nuclei, including respiratory centers
Limbic system
This set of brain structures (deep telencephalon and some diencephalon) work together to enable deep, emotional memory. It includes
the amygdala and the hippocampus (both part of the temporal lobe).
Research indicates that psychopaths have non-functioning limbic systems. Why do you think this is?
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Lab 15: The Brain
Reading: M&O Ch. 15
You are responsible for identifying all of the following structures on both the sheep brain and the human brain. Figures in M&O are
useful for the human brain. There is a figure for the sheep brain included in this handout.
Start with the regional and external anatomy of the brains. Then study internal anatomy on sagittally sectioned brains. Finally,
examine our special demonstration specimens and identify what you can. Try to stay cognizant of the function of each structure.
Otherwise, they are no more than gushy chunks of neural tissue.
A word of warning: brains are prone to dry out quickly so make sure you examine them in a tray full of water and wet them down
thoroughly every 20 minutes or so.
Part 1: Brain regions - whole brain
Using whole brains, identify all the following structures:
Forebrain
1. Telencephalon
A. cerebral hemispheres
B. gyri (ridges)
C. sulci (grooves)
D. longitudinal fissure
E. central sulcus (sometimes difficult to find, unless you look at the midsagittal slice)
F. precentral gyrus
G. postcentral gyrus
H. frontal lobes
I. parietal lobes
J. occipital lobes
K. temporal lobes
L. olfactory bulbs (may be damaged)
M. olfactory tracts
2. Diencephalon
A. optic nerves
B. optic chiasm
C. optic tracts
D. hypothalamus
E. infundibulum
F. pituitary gland/ hypophysis
Midbrain
3. Mesencephalon
A. superior colliculi
B. inferior colliculi
C. cerebral peduncles (connect the midbrain to the hindbrain...visible from the ventral view of the surface of the brain)
Hindbrain
4. Metencephalon
A. cerebellum
B. pons
5. Myelencephalon
A. medulla oblongata
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Part 2: Internal structures
Slice your sheep brain in half down the mid-sagittal line, taking care to adhere as closely as possible to the midline (or find one already
sliced). Find the required structures in the text that follows on your sheep brain, using the appended figures, and then try to find them
on the human brain demonstration specimens.
1. Telencephalon
A. corpus callosum (large band of commissural fibers crossing from one cerebral hemisphere to the other) B. septum pellucidum (thin membrane that separates the left and right lateral ventricles)
C. fornix (longitudinal band of fibers running along the ventral border of the septum pellucidum that connects the
hippocampus (a nucleus that lies in the medial floor of the inferior horn of the lateral ventricle) with the hypothalamus.
2. Diencephalon
A. epithalamus (dorsal)
i. pineal gland (nubbin like)
B. thalamus (lateral)
i. third ventricle (the thalamus forms the lateral wall of the third ventricle)
ii. interventricular foramen (of Monro)- connects lateral and third ventricles
C. hypothalamus (ventral)
i. optic chiasm (lies at the rostral end of the hypothalamus)
ii. infundibulum (caudal)
3. Mesencephalon
A. mesencephalic aqueduct (cerebral aqueduct)
B. superior and inferior colliculi
4. Metencephalon
A. pons (ventral)
B. cerebellum (with its white matter arbor vitae and gray matter cortex dorsally)
5. Myelencephalon (There is little of note on the midsagittal view of the medulla).
Part 3: Meninges
Use M&O pp. 450-452 as your guide.
1. dura mater (and the following extensions of dura mater)
A. falx cerebri
B. falx cerebelli
C. tentorium cerebelli are extensions of the dura mater that have important relations to the brain. The
2. arachnoid mater (does not extend into the cerebral sulci)
3. pia mater (underlies cerebral blood vessels; extends down into the cerebral sulci)
Part 4: Ventricles and the Flow of Cerebrospinal Fluid (CSF)
Now review the following structures which you should have seen previously and learn the flow of CSF through the brain.
1. The lateral ventricles (largest in the brain) are separated by the spetum pelucidum and are found in the cerebral hemispheres,
just inferior to the corpus callosum.
2. The lateral ventricle connects to the third ventricle via the interventricular foramen (aka foramen of Monroe) in the
diencephalon.
3. The third ventricle connects to the fourth ventricle (found in the hindbrain) via the cerebral aqueduct (mesencephalic aqueduct)
in the mesencephalon.
4. CSF in the forth ventricle then flows into the subarachnoid space surrounding the brain.
5. CSF enters the venus blood supply found in the superior sagittal sinus through mushroom shaped structures called arachnoid
granulations (villi). These little one-way valves allow CSF to drain back into the blood.
NOTE: All ventricles contain a choroid plexus, which is where cerebrospinal fluid is produced.
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External Brain 15: Brain
73. List the three primary brain vesicles and the five secondary brain vesicles, and identify the major areas
of the adult brain that arise from each region.
74. Correlate functions with each major area of the adult brain.
75. Identify the five lobes of the cerebral cortex and describe how the motor and sensory functions of the
cerebrum are distributed among the lobes.
76. Discuss the role of the corpus callosum in connecting the two halves of the cerebrum.
77. Describe the location and functions of the limbic system.
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