PPT Notes Chapter 12 Flashcards
Central Nervous System (CNS)
CNS consists of the brain and spinal cord
Cephalization
Evolutionary development of the rostral (anterior) portion of the CNS
Increased number of neurons in the head
Highest level is reached in the human brain
Background: Embryonic Development
Neural groove fuses dorsally to form the neural tube
Neural tube gives rise to the brain and spinal cord
Anterior end of the neural tube gives rise to three primary brain vesicles
Prosencephalon—forebrain
Mesencephalon—midbrain
Rhombencephalon—hindbrain
Background: Effect of Space Restriction on Brain Development
Midbrain flexure and cervical flexure cause forebrain to move toward the brain stem
Cerebral hemispheres grow posteriorly and laterally
Cerebral hemisphere surfaces crease and fold into convolutions
Midbrain flexure and cervical flexure cause forebrain to move toward the brain stem
Cerebral hemispheres grow posteriorly and laterally
Cerebral hemisphere surfaces crease and fold into convolutions
Regions and Organization of the CNS
Adult brain regions Cerebral hemispheres Diencephalon Brain stem (midbrain, pons, and medulla) Cerebellum Spinal cord Central cavity surrounded by a gray matter core External white matter composed of myelinated fiber tracts
REMEMBER! Gray matter interprets, white matter transmits!!
Brain
Similar pattern with additional areas of gray matter
Nuclei in cerebellum and cerebrum
Cortex of cerebellum and cerebrum
Ventricles of the Brain
Connected to one another and to the central canal of the spinal cord
Lined by ependymal cells
Contain cerebrospinal fluid
Two C-shaped lateral ventricles in the cerebral hemispheres
Third ventricle in the diencephalon
Fourth ventricle in the hindbrain, dorsal to the pons, develops from the lumen of the neural tube
Cerebral Hemispheres: Important!!
Surface markings Ridges (gyri), shallow grooves (sulci), and deep grooves (fissures) Five lobes Frontal Parietal Temporal Occipital Insula Surface markings Central sulcus Separates the precentral gyrus of the frontal lobe and the postcentral gyrus of the parietal lobe Longitudinal fissure Separates the two hemispheres Transverse cerebral fissure Separates the cerebrum and the cerebellum
Cerebral Cortex
Thin (2–4 mm) superficial layer of gray matter
40% of the mass of the brain
Site of conscious mind: awareness, sensory perception, voluntary motor initiation, communication, memory storage, understanding
Each hemisphere connects to contralateral side of the body
There is lateralization of cortical function in the hemispheres [right brain/left brain]
Functional Areas of the Cerebral Cortex
The three types of functional areas are:
Motor areas—control voluntary movement
Sensory areas—conscious awareness of sensation
Association areas—integrate diverse information
Conscious behavior involves the entire cortex
Motor Areas
Primary (somatic) motor cortex
Premotor cortex
Broca’s area
Frontal eye field
Primary Motor Cortex
Large pyramidal cells of the precentral gyri
Long axons pyramidal (corticospinal) tracts
Allows conscious control of precise, skilled, voluntary movements
Motor homunculi: upside-down caricatures representing the motor innervation of body regions
Premotor Cortex
Anterior to the precentral gyrus
Controls learned, repetitious, or patterned motor skills
Coordinates simultaneous or sequential actions
Involved in the planning of movements that depend on sensory feedback
Broca’s Area
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
Anterior to the premotor cortex and superior to Broca’s area
Controls voluntary eye movements
Sensory Areas
Primary somatosensory cortex
Somatosensory association cortex
Visual areas
Auditory areas
Primary Somatosensory Cortex
In the postcentral gyri
Receives sensory information from the skin, skeletal muscles, and joints
Capable of spatial discrimination: identification of body region being stimulated
Somatosensory Association Cortex
Posterior to the primary somatosensory cortex
Integrates sensory input from primary somatosensory cortex
Determines size, texture, and relationship of parts of objects being felt
Visual Areas
Primary visual (striate) cortex
Extreme posterior tip of the occipital lobe
Receives visual information from the retinas
Visual association area
Surrounds the primary visual cortex
Uses past visual experiences to interpret visual stimuli (e.g., color, form, and movement)
Complex processing involves entire posterior half of the hemispheres
Auditory Areas
Primary auditory cortex
Superior margin of the temporal lobes
Interprets information from inner ear as pitch, loudness, and location
Auditory association area
Located posterior to the primary auditory cortex
Stores memories of sounds and permits perception of sounds
OIfactory Cortex
Medial aspect of temporal lobes (in piriform lobes)
Part of the primitive rhinencephalon, along with the olfactory bulbs and tracts
(Remainder of the rhinencephalon in humans is part of the limbic system)
Region of conscious awareness of odors
Gustatory Cortex
In the insula
Involved in the perception of taste
Visceral Sensory Area
Posterior to gustatory cortex
Conscious perception of visceral sensations, e.g., upset stomach or full bladder
Vestibular Cortex
Posterior part of the insula and adjacent parietal cortex
Responsible for conscious awareness of balance (position of the head in space)
Multimodal Association Areas
Receive inputs from multiple sensory areas
Send outputs to multiple areas, including the premotor cortex
Allow us to give meaning to information received, store it as memory, compare it to previous experience, and decide on action to take
There are several multimodal association areas.
Limbic Association Area
Part of the limbic system
Provides emotional impact that helps establish memories
