Chapter 14: The Brain
BIO 210 Lab
Instructor: Dr. Rebecca Clarke
Human Brain
 Contains almost 98% of body’s neural tissue
 Average weight about 3 lb (1.4 kg)
6 Major Regions of the Brain
 Cerebrum
 Cerebellum
 Diencephalon
 Mesencephalon
 Pons
 Medulla oblongata
The Brain
 Embryological Development
 Determines organization of brain structures
 Neural tube
 Origin of brain
 Enlarges into three primary brain vesicles

prosencephalon

mesencephalon

rhombencephalon
The Brain
 Five Secondary Brain Vesicles
 Telencephalon
 Diencephalon
 Mesencephalon
 Metencephalon
 Myelencephalon
The Brain
 Origins of Brain Structures
 Diencephalon and mesencephalon persist
 Telencephalon:
 Becomes cerebrum
 Metencephalon
 Forms cerebellum and pons
 Myelencephalon
 Becomes medulla oblongata
The Brain
Cerebrum
 Controls higher mental functions
 Largest part of brain (80% of volume)
Cerebrum
 Divided into large L and R cerebral hemispheres
 Longitudinal fissure:
 Separates upper part of R & L hemispheres
 Corpus callosum:
 Thick, crescent-shaped band of white matter
 Connects R & L hemispheres
Cerebrum
 Corpus Callosum
Figure 14–11a
Cerebral Cortex
 Surface layer of gray matter on cerebrum
 Also called neural cortex
 Folded surface:
 Increases surface area
 Provides space for more cortical neurons
Cerebral Cortex
 Folded surface has:
 Gyri (sing: gyrus) =
elevated ridges
 Sulci (sing: sulcus) = hollow
depressions
 Fissures = deep grooves
Cerebrum
 Sulci and fissures divide cerebral hemispheres into distinct
lobes (regions) (named for overlying bones of skull)
Cerebral Structures
 Central sulcus
 Groove across hemi-sphere
 Separates motor and sensory areas
 Postcentral gyrus
 Upfold posterior to central sulcus
 Primary sensory cortex
 Precentral gyrus
 Upfold anterior to central sulcus
 Primary motor cortex
Cerebral Lobes
 Frontal lobe
 Motor cortex
 Parietal lobe
 Sensory cortex
 Occipital lobe
 Visual cortex
 Temporal lobe
 Auditory cortex
 Olfactory cortex
Cerebral Structures: Insula
 “5th lobe;” deep “island” of
cortex medial to lateral sulcus
 Exposed when temporal lobe
pushed to side
 Site of gustatory cortex
Cerebral Gray Matter
 Found in:
 Cerebral cortex
 Cerebral nuclei
Cerebral White Matter
 Myelinated nerve fibers
 Makes up most of interior of cerebrum
 Located:
 Deep to cerebral cortex
 Around cerebral nuclei
Ventricles of the Brain
 Chambers lined with ependymal cells
  CSF
 4 ventricles: 2 lateral (R & L), 3rd, 4th
Ventricles of the Brain:
Lateral Ventricles (First 2)
 1/cerebral hemisphere
Ventricles of the Brain:
3rd Ventricle
 In diencephalon between R & L thalami
 Connects to lateral ventricles via interventricular foramen (of
Monro)
Ventricles of the Brain:
4th Ventricle
 Extends between pons and cerebellum into medulla oblongata; becomes
continuous with central canal of spinal cord
 Connects to 3rd ventricles via mesencephalic (cerebral) aqueduct
CSF Circulation
 Choroid Plexus
 Through ventricles
 To central canal of spinal cord
 Into subarachnoid space around
brain, spinal cord, and cauda equina
 Enters venous circulation
Cranial Meninges
 Have 3 layers (like spinal meninges):
 Dura mater
 Arachnoid mater
 Pia mater
 Are continuous with spinal meninges
 Protect the brain from cranial trauma (act as “air bags”)
Cranial Meninges: Dura Mater
 2 Fibrous layers
 Outer (endosteal) layer
 Fused to periosteum of cranial
bones
 No epidural space (vs. spinal
cord)
 Inner (meningeal) layer
 In some locations folds into
cranial cavity between
hemispheres  dural folds
 Venous (dural) sinus between
layers
Cranial Meninges: Dural Folds
 Folded inner layer of dura
mater
 Extend into cranial cavity
 Stabilize and support brain
(act like “seat belts”)
 Contain collecting veins
(dural sinuses)
 [FYI: falx cerebri, tentorium
cerebelli, falx cerebelli]
Cranial Meninges: Arachnoid Mater
 Consists of:
 Arachnoid membrane
 Epithelial layer
 Covers brain (does not
follow folds)
 Arachnoid trabeculae
 Cells and fibers that cross
subarachnoid space to pia
mater
Cranial Meninges: Pia Mater
 Attached to brain surface by
astrocytes
Cerebellum
 Coordinates repetitive body movements
 Second largest part of brain
 10% of volume but 50% of neurons
Cerebellum
 R & L cerebellar hemispheres:
 Separated at midline by vermis
 Vermis:
 Narrow band of cortex
Cerebellum
 Highly folded cerebellar cortex
  folia (less prominent than gyri)
 Arbor vitae: central, tree-like branching mass of white
matter deep to cortex
Diencephalon
 Located in central region of brain deep to cerebrum
 Links cerebrum with brain stem
Diencephalon
 4 Regions:
 Thalamus – L & R:
 Masses of gray matter (nuclei)
 Forms walls of third ventricle
 Hypothalamus:
 Below thalamus
 Forms floor and part of walls of
thalamus
Diencephalon
 Third ventricle:
 Separates L & R thalamus
 Pineal gland:
 Secretes hormone melatonin
Diencephalon
 Intermediate mass:
 Projection of gray matter
 Extends into ventricle from each side of thalamus
Hypothalamus
 Has neural and endocrine functions
 Infundibulum
 Stalk that connects pituitary gland to hypothalamus
 Pituitary Gland
Brain Stem
 Processes information between:
 Spinal cord and cerebrum or cerebellum
 Includes: mesencephalon, pons, medulla oblongata
Mesencephalon (Midbrain)
 2 pairs of sensory nuclei (corpora quadrigemina):
 Superior colliculi (visual)
 Inferior colliculi (auditory)
Pons
 Links cerebellum with mesencephalon, diencephalon,
cerebrum, and spinal cord
 Involved in motor control
Medulla Oblongata
 Connects brain to spinal cord
 Regulates complex autonomic
functions:
 Heart rate, blood pressure,
respiration
 Continuous with spinal cord