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BIOB32H3 Lecture Notes - Medial Longitudinal Fissure, Neural Groove, Coccyx

Biological Sciences
Course Code
Kenneth Welch

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Central Nervous System (CNS)
Central Nervous System (CNS)
CNS composed of the brain and spinal cord
Elaboration of the anterior portion of the CNS
Increase in number of neurons in the head
Highest level has been reached in the human brain
The Brain
Composed of wrinkled, pinkish gray tissue
Surface anatomy includes cerebral hemispheres, cerebellum, and brain stem
Embryonic Development
During the first 26 days of development:
Ectoderm thickens along dorsal midline to form the neural plate
The neural plate invaginates, forming a groove flanked by neural folds
The neural groove fuses dorsally and forms the neural tube
Primary Brain Vesicles
The anterior end of the neural tube expands and constricts to form the three primary brain
Prosencephalon the forebrain
Mesencephalon the midbrain
Rhombencephalon hindbrain
Secondary Brain Vesicles
In week 5 of embryonic development, secondary brain vesicles form:
Telencephalon and diencephalon arise from the forebrain
Mesencephalon remains undivided
Metencephalon and myelencephalon arise from the hindbrain
Adult Brain Structures
Fates of the secondary brain vesicles:
Telencephalon cerebrum: cortex, white matter, and basal nuclei
Diencephalon thalamus, hypothalamus, and epithalamus
Mesencephalon brain stem: midbrain
Metencephalon brain stem: pons
Myelencephalon brain stem: medulla oblongata
Adult Neural Canal Regions
Adult structures derived from the neural canal
Telencephalon lateral ventricles
Diencephalon third ventricle
Mesencephalon cerebral aqueduct
Metencephalon and myelencephalon fourth ventricle
Basic Pattern of the Central Nervous System
Spinal Cord
Central cavity surrounded by a gray matter core
External to which is white matter composed of myelinated fiber tracts
Similar to spinal cord but with additional areas of gray matter

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Cerebellum has gray matter in nuclei
Cerebrum has nuclei and additional gray matter in the cortex
Ventricles of the Brain
Arise from expansion of the lumen of the neural tube
The ventricles are:
The paired C-shaped lateral ventricles
The third ventricle found in the diencephalon
The fourth ventricle found in the hindbrain dorsal to the pons
Cerebral Hemispheres
Form the superior part of the brain and make up 83% of its mass
Contain ridges (gyri) and shallow grooves (sulci)
Contain deep grooves called fissures
Are separated by the longitudinal fissure
Have three basic regions: cortex, white matter, and basal nuclei
Major Lobes, Gyri, and Sulci of
the Cerebral Hemisphere
Deep sulci divide the hemispheres into five lobes:
Frontal, parietal, temporal, occipital, and insula
Central sulcus separates the frontal and parietal lobes
Parietal-occipital sulcus separates the parieto and occipital lobes
Lateral sulcus separates the parietal and temporal lobes
The precentral and postcentral gyri border the central sulcus
Cerebral Cortex
The cortex superficial gray matter; accounts for roughly 40% of the mass of the brain
It enables sensation, communication, memory, understanding, and voluntary movements
Each hemisphere acts contralaterally (controls the opposite side of the body)
Hemispheres are not equal in function
No functional area acts alone; conscious behavior involves the entire cortex
Functional Areas of the Cerebral Cortex
Three types of functional areas are:
Motor areas control voluntary movement
Sensory areas conscious awareness of sensation
Association areas integrate diverse information
Cerebral Cortex: Motor Areas
Primary (somatic) motor cortex
Premotor cortex
Broca’s area
Frontal eye field
Primary Motor Cortex
Located in the precentral gyrus
Composed of pyramidal cells whose axons make up the corticospinal tracts
Allows conscious control of precise, skilled, voluntary movements
Motor homunculus caricature of relative amounts of cortical tissue devoted to each motor
Premotor Cortex
Located anterior to the precentral gyrus

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Controls learned, repetitious, or patterned motor skills
Coordinates simultaneous or sequential actions
Involved in the planning of movements
Broca’s Area and Frontal Eye Field
Broca’s area
Located anterior to the inferior region of the premotor area
Present in one hemisphere (usually the left)
A motor speech area that directs muscles of the tongue
Is active as one prepares to speak
Frontal eye field
Located anterior to the premotor cortex and superior to Broca’s area
Controls voluntary eye movement
Sensory Areas
Primary somatosensory cortex
Somatosensory association cortex
Visual areas
Auditory areas
Olfactory cortex
Gustatory cortex
Vestibular cortex
Primary Somatosensory Cortex
Located in the postcentral gyrus, this area:
Receives information from the skin and skeletal muscles
Exhibits spatial discrimination
Somatosensory homunculus caricature of relative amounts of cortical tissue devoted to
each sensory function
Somatosensory Association Area
Located posterior to the primary somatosensory cortex
Integrates sensory information
Forms comprehensive understanding of the stimulus
Determines size, texture, and relationship of parts
Visual Area
Primary visual cortex
Located on the extreme posterior tip of the occipital lobe
Receives visual information from the retinas
Visual association area
Surround the primary visual cortex
Interprets visual stimuli (e.g., color, form, and movement)
Auditory Areas
Primary auditory cortex
Located at the superior margin of the temporal lobe
Receives information related to pitch, rhythm, and loudness
Auditory association area
Located posterior to the primary auditory cortex
Stores memories of sounds and permits perception of sounds
Association Areas
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