Chapter 11, Section 3
Development of the Brain & The Cerebrum
The Brain • Functions of the brain: • Sensations and perceptions • Memory • Reasoning • Makes decisions • Commands skeletal muscles • Regulates visceral activities • Provides personality
• Major parts of the brain: • Cerebrum •Diencephalon • Cerebellum • Brainstem • Midbrain • Pons • Medulla oblongata
The Brain
Figure 11.15b. Sagittal section of human brain. The major portions include the cerebrum, the diencephalon, the cerebellum, and the brainstem. The brainstem includes the midbrain, the pons, and the medulla oblongata.
Brain Development The central nervous system develops from a neural tube that gives rise to the brain and spinal cord. The brain begins as three primary (vesicles): 1. Prosencephalon – forebrain 2. Mesencephalon – midbrain 3. Rhombencephalon – hindbrain
cavities
Later: The prosencephalon divides into the • telencephalon & diencephalon. mesencephalon remains as the midbrain The rhombencephalon divides into the • metencephalon & myelencephalon
Brain Development •Five secondary vesicles: • Telencephalon • Diencephalon • Mesencephalon • Metencephalon • Myelencephalon
Brain Development Eventually the vesicles give rise to regions of the brain: telencephalon gives rise to the cerebrum and basal nuclei diencephalon gives rise to the thalamus, hypothalamus, and pituitary gland mesencephalon becomes the midbrain metencephalon forms the pons and cerebellum myelencephalon forms the medulla oblongata.
Functions of the Cerebrum The cerebrum provides higher brain functions: 1. Interpreting senses 2. Voluntary muscle movements 3. Memory 4. Reasoning 5. Intelligence 6. Personality
Figure 11.16 Colors distinguish the lobes of the cerebral hemisphere. (a) lateral view. (b) superior view
Structure of the Cerebrum The cerebrum consists of two hemispheres. •Longitudinal fissure • deep groove that separates the left and right cerebral hemispheres •Corpus callosum • Bridge of nerve fibers that connects cerebral hemispheres. •Transverse fissure •Deep groove that separates the cerebrum from the cerebellum
The surface of the cerebrum contains many ridges and grooves. • Gyri (sing. gyrus) = Bumps or convolutions • Sulci (sing. Sulcus)= Grooves in cerebrum
Lobes of the Cerebrum • Five (5) lobes bilaterally: • Frontal lobe • Parietal lobe • Temporal lobe • Occipital lobe • Insula – deep lobe
Figure 11.16(c) lateral view of the cerebrum using colors to distinguish the individual lobes. The temporal lobe is retracted to expose the deeper insula.
Functional Regions of the Cerebral Cortex • Cerebral cortex • Thin layer of gray matter • Outermost portion of cerebrum • Contains 75% of all neurons in the nervous system • Cerebral medulla • Thick layer of underlying white matter • bulk of cerebrum
Functional Regions of the Cerebral Cortex Sensory Areas – cerebrum interprets impulses from receptors Motor Areas – cerebrum controls voluntary motor actions Association Areas- cerebrum connects from one region of the brain to another • Thoughts, emotions, and understanding
Functions of the Frontal Lobes Frontal Lobes • Association areas = higher intellect • Judgment • Complex problem solving • Planning and decision making • Motor areas = Voluntary motor control • Frontal eye field – voluntary movements of eyes • Broca’s area – coordinates mouth, tongue, and pharynx for speech • Precentral gyrus – motor areas involved with control of voluntary muscles
Pyramidal cells- Pyramind shaped cells within the frontal lobe that initiate voluntary movements
Functions of the Parietal Lobes Parietal Lobes • Sensory Areas • Sensation of touch temperature, pain involving the skin • Post-central gyrus – sensory areas involved with cutaneous and other senses • Wernike’s Area – sensory speech area. Usually within left hemisphere
•Association areas - Interpret sensory information • Choosing words to express thoughts and emotions • Wernike’s Area - Also called the general interpretive area •Integrates visual, auditory, and other sensory information an then interprets a situation.
Figure 11.18. Functional regions of the cerebral cortex. (a) motor areas that control voluntary muscles. (b) sensory areas involved with cutaneous and other senses.
Functions of the Temporal and Occipital Lobes Temporal Lobes • Sensory Areas • Hearing and smell (smell within deep temporal lobe) •Association areas – interpret complex sensory experiences • Understand speech and reading • Stores memories of visual scenes, music, and other sensory patterns
Occipital Lobes • Sensory Areas • Visual Cortex - vision •Association areas • Areas for analyzing visual patterns • Combines visual images with other experiences – face recognition
Hemisphere Dominance • The left hemisphere is dominant in most individuals • Dominant hemisphere controls: • Speech • Reading and writing • Verbal skills • Analytical skills • Computational skills
• Nondominant hemisphere controls: • Nonverbal tasks • Motor tasks • Understanding and interpreting musical and visual patterns • Provides emotional and intuitive thought processes
Corpus callosum enables the dominant hemisphere to control the motor cortex in the nondominant hemisphere. It also relays sensory information reaching the nondominant hemisphere to the dominant hemisphere to be interpreted.
Basal Nuclei The basal nuclei are three masses of grey matter deep within the cerebrum: 1. Caudate nucleus 2. Putamen 3. Globus pallidus
The basal nuclei secrete the inhibitory neurotransmitter dopamine • Basal nuclei interact with a region in the midbrain, called Substantia Nigra • Basal nuclei & substantia nigra facilitate voluntary movements
Parkinson’s Disease Parkinson’s Disease (PD) results occurs from degeneration of the basal nuclei and the substantia nigra. This results in a deficiency of dopamine. Symptoms include: • tremors at rest • poor small muscle control • rigidity • difficulties speaking
End of Chapter 11, Section 3
Figure 11D. Muhammed Ali has PD from many years of head injuries as a boxer. Michael J. Fox first experienced symptoms of PD at age 29, which is unusual.