Chapter 12 Flashcards
Cephalization
Cephalization is the evolutionary development of the rostral (anterior) portion of the CNS
- Cephalization resulted in an increased number of neurons.
- This is the highest level reached in the human brain.
Organization of the brain regions
- Adult brains have 4 regions:
1. Cerebral hemispheres
2. Diencephalon
3. Brain stem, consisting of:- Midbrain
- Pons
- Medulla
4. Cerebellum
Brain regions illustration
Gray matter
Gray matter is short, nonmyelinated neurons and cell bodies.
White matter
White matter is myelinated and nonmyelinated axons.
Cross section of the spinal cord
Ventricles
- Ventricles are any fluid filled chamber that are continuous to one another and to the central canal of the spinal cord.
- Ventricles are filled with cerebrospinal fluid (CSF)
- Ventricles are lined by ependymal cells (neuroglial cells)
- Lateral ventricles (paired): C shaped; deep in each of the hemispheres; separated by a membrane called a septum pellucidum.
- Third ventricle is in the diencephalon;
- Fourth ventricle is in the hind brain which is continuous with the central canal of the spinal cord;
Surface marking on cerebral hemispheres
- Gyri: ridges
- Sulci: shallow grooves
- Fissures: deep grooves
- Longitudinal fissure: separates the 2 hemispheres
- Transverse cerebral fissure: separates cerebrum and cerebellum
Lateral view of the cerebral hemispheres
Several sulci divide each hemisphere into 5 lobes:
- Frontal
- Parietal
- Temporal
- Occipital
- Inusla
The lobes and sulci of the cerebrum
The major sulci that divide the lobes:
- Central sulcus separates pre central gyrus of the frontal lobe and post central gyrus of the parietal lobe.
- Parieto-occipital sulcus separates the occipital and parietal lobes.
- The lateral sulcus outlines the temporal lobes.
Each hemisphere has 3 basic regions:
- The cerebral cortex of gray matter superficially.
- White matter internally
- Basal nuclei deep within the white matter. Basal nuclei is island of gray matter situated deep within the white matter.
The cerebral cortex
- The cerebral cortex is the executive suite of the brain.
- It is a superficial layer of gray matter.
- Mostly made up of neuron cell bodies, dendrites, glial cells and blood vessels.
- Has no axons
- Makes up about 40% of the brain.
4 general considerations of the cerebral cortex:
- Contains 3 types of functional areas:
A. Motor areas: control voluntary movement
B. Sensory areas: conscious awareness of sensation.
C. Association areas: integrate diverse information - Each hemisphere is concerned with contralateral (opposite) side of the body.
- Lateralization (specialization) of cortical function can occur in only one hemisphere.
- Conscious behavior involves the entire cortex in one way or another.
Motor areas of the cerebral cortex
- Located in the frontal lobe, motor areas act to control voluntary movement.
- Primary motor cortex is in the precentral gyrus
- Premotor cortex is anterior to the precentral gyrus
- Broca’s area is anterior to the inferior premotor area.
- Frontal eye field is within and anterior to the premotor cortex; superior to Broca’s area.
The motor areas of the cerebral cortex, illustrated study from this picture
The primary (somatic) motor cortex
- Located in the precentral gyrus of the frontal lobe
- Pyramidal cells - large neuron cell that allow conscious control of precise skilled skeletal muscle movements
- Somatotopy - all of the muscles of the body that can be mapped to an area on the primary motor cortex
Premotor cortex
- Helps plan movements
- Staging area for skilled motor activities
- Controls learned, repetitious, or patterned motor skills
- Coordinates simultaneous or sequential actions
- Controls voluntary actions that depend on sensory feedback
Broca’s Area
- Present in one hemisphere (usually left)
- Motor speech area that directs muscles of speech production
- Active in planning speech and voluntary motor activities
Frontal eye field
Controls voluntary eye movements
Sensory areas of the cerebral cortex
- Areas of the cortex concerned with conscious awareness of sensation
- 8 main areas include:
1. Primary somatosensory cortex allows spatial discrimination and the ability to detect the location of stimulation.
2. Somatosensory association cortex integrates sensory information and produces an understanding of the stimulus being felt.
3. Visual areas
4. Auditory areas
5. Vestibular cortex is responsible for conscious awareness of balance.
6. Olfactory cortex
7. Gustatory cortex
8. Visceral sensory area s are involved in conscious awareness of visceral
sensation.
Multimodal association areas of the cerebral cortex
- Receive inputs from multiple sensory areas.
- Send outputs to multiple areas.
- Allows us to give meaning to information received, store it in memory, tie it to previous experience, and decide on actions.
- Sensations, thoughts and emotions become conscious; this makes us who we are.
- Broadly divided into 3 parts:
1. Anterior association area - prefrontal cortex: intelligent condition, recall and personality; working memory
2. Posterior association area - temporal, parietal and occipital lobes; recognizes patterns and faces; understanding written and spoken language
3. Limbic association area - limbic system; helps establish memories
Lateralization of cortical functioning
- Lateralization: division of labor between hemispheres; The hemispheres are not identical
- Cerebral dominance: refers to the hemisphere that is dominant for language
- 90% of humans have left-sided dominance.
- This usually results in right handedness
- In the other 10%, the roles of the hemispheres are reversed.
Cerebral white matter
- Responsible for communication between cerebral areas, and between the cortex and lower CNS
- Consists of myelinated fibers bundled into large tracts
- Classified according to the direction they run:
- Association (connect regions within the same hemisphere), commissure (connect the hemispheres), and projection fibers (connect each region to other parts of the brain or to the spinal cord).
- Left hemisphere thought to control language thought and logic.
- Right hemisphere is more for visual, spatial skills, intuition, emotion, artistic and musical skills.
- The 2 hemispheres communicate with each other via fiber tracts and functional integration.
White fiber tracts of the cerebral hemispheres
Basal Nuclei (Ganglia)
This is the 3rd of the 3 basic regions of the cerebrum
- Each hemisphere’s basal nuclei include a:
- Caudate nucleus
- Putamen
- Globus pallidus
- Cuadate nucleus + putamen = Striatum
- Function of basal nuclei: Influence muscle movements, play a role in emotion, regulate movement intensity, filter out inappropriate responses.
Basal nuclei illustrated