Copyright © 2010 Pearson Education, Inc. Functional Brain Systems Networks of neurons that work together and span wide areas of the brain Limbic system Reticular formation
Copyright © 2010 Pearson Education, Inc. Limbic System Structures on the medial aspects of cerebral hemispheres and diencephalon Includes parts of the diencephalon and some cerebral structures that encircle the brain stem
Copyright © 2010 Pearson Education, Inc. Figure Corpus callosum Diencephalic structures of the limbic system Fiber tracts connecting limbic system structures Cerebral struc- tures of the limbic system Limbic System
Copyright © 2010 Pearson Education, Inc. Limbic System Emotional or affective brain Amygdala—recognizes angry or fearful facial expressions, assesses danger, and elicits the fear response Cingulate gyrus—plays a role in expressing emotions via gestures, and resolves mental conflict Puts emotional responses to odors Example: skunks smell bad
Copyright © 2010 Pearson Education, Inc. Limbic System: Emotion and Cognition The limbic system interacts with the prefrontal lobes, therefore: We can react emotionally to things we consciously understand to be happening We are consciously aware of emotional richness in our lives Hippocampus and amygdala—play a role in memory
Copyright © 2010 Pearson Education, Inc. Reticular Formation Runs through brainstem (medulla, pons, midbrain) Has far-flung axonal connections with hypothalamus, thalamus, cerebral cortex, cerebellum, and spinal cord
Copyright © 2010 Pearson Education, Inc. Reticular Formation: RAS and Motor Function Reticular Activating System (RAS) Sends impulses to the cerebral cortex to keep it conscious and alert Filters out repetitive and weak stimuli (~99% of all stimuli!) Severe injury results in permanent unconsciousness (coma)
Copyright © 2010 Pearson Education, Inc. Figure Visual impulses Reticular formation Ascending general sensory tracts (touch, pain, temperature) Descending motor projections to spinal cord Auditory impulses Radiations to cerebral cortex Reticular activating system
Copyright © 2010 Pearson Education, Inc. Consciousness Conscious perception of sensation Voluntary initiation and control of movement Capabilities associated with higher mental processing (memory, logic, judgment, etc.) Loss of consciousness (e.g., fainting or syncopy) is a signal that brain function is impaired
Copyright © 2010 Pearson Education, Inc. Consciousness Clinically defined on a continuum that grades behavior in response to stimuli Alertness Drowsiness (lethargy) Stupor Coma
Copyright © 2010 Pearson Education, Inc. Protection of the Brain Bone (skull) Membranes (meninges) Watery cushion (cerebrospinal fluid) Blood-brain barrier
Copyright © 2010 Pearson Education, Inc. Meninges Cover and protect the CNS Protect blood vessels and enclose venous sinuses Contain cerebrospinal fluid (CSF) Form partitions in the skull
Copyright © 2010 Pearson Education, Inc. Meninges Three layers Dura mater Arachnoid mater Pia mater
Copyright © 2010 Pearson Education, Inc. Figure Skin of scalp Periosteum Falx cerebri (in longitudinal fissure only) Blood vessel Arachnoid villus Pia mater Arachnoid mater Dura mater Meningeal Periosteal Bone of skull Superior sagittal sinus Subdural space Subarachnoid space
Copyright © 2010 Pearson Education, Inc. Dura Mater Strongest meninx Two layers of fibrous connective tissue (around the brain) separate to form dural sinuses
Copyright © 2010 Pearson Education, Inc. Dura Mater Dural septa limit excessive movement of the brain Falx cerebri—in the longitudinal fissure; attached to crista galli Falx cerebelli—along the vermis of the cerebellum Tentorium cerebelli—horizontal dural fold over cerebellum and in the transverse fissure
Copyright © 2010 Pearson Education, Inc. Figure 12.25a Falx cerebri Superior sagittal sinus Straight sinus Crista galli of the ethmoid bone Pituitary gland Falx cerebelli (a) Dural septa Tentorium cerebelli
Copyright © 2010 Pearson Education, Inc. Arachnoid Mater Middle layer with weblike extensions Separated from the dura mater by the subdural space Subarachnoid space contains CSF and blood vessels Arachnoid villi protrude into the superior sagittal sinus and permit CSF reabsorption
Copyright © 2010 Pearson Education, Inc. Figure Skin of scalp Periosteum Falx cerebri (in longitudinal fissure only) Blood vessel Arachnoid villus Pia mater Arachnoid mater Dura mater Meningeal Periosteal Bone of skull Superior sagittal sinus Subdural space Subarachnoid space
Copyright © 2010 Pearson Education, Inc. Pia Mater Layer of delicate vascularized connective tissue that clings tightly to the brain
Copyright © 2010 Pearson Education, Inc. Cerebrospinal Fluid (CSF) Composition Watery solution Less protein and different ion concentrations than plasma Constant volume
Copyright © 2010 Pearson Education, Inc. Cerebrospinal Fluid (CSF) Functions Gives buoyancy to the CNS organs Protects the CNS from blows and other trauma Nourishes the brain and carries chemical signals
Copyright © 2010 Pearson Education, Inc. Figure 12.26a Superior sagittal sinus Arachnoid villus Subarachnoid space Arachnoid mater Meningeal dura mater Periosteal dura mater Right lateral ventricle (deep to cut) Choroid plexus of fourth ventricle Central canal of spinal cord Choroid plexus Interventricular foramen Third ventricle Cerebral aqueduct Lateral aperture Fourth ventricle Median aperture (a) CSF circulation CSF is produced by the choroid plexus of each ventricle. 1 CSF flows through the ventricles and into the subarachnoid space via the median and lateral apertures. Some CSF flows through the central canal of the spinal cord. 2 CSF flows through the subarachnoid space. 3 CSF is absorbed into the dural venous sinuses via the arachnoid villi
Copyright © 2010 Pearson Education, Inc. Choroid Plexuses Produce CSF at a constant rate Hang from the roof of each ventricle Clusters of capillaries enclosed by pia mater and a layer of ependymal cells Ependymal cells use ion pumps to control the composition of the CSF and help cleanse CSF by removing wastes
Copyright © 2010 Pearson Education, Inc. Figure 12.26b Ependymal cells Capillary Connective tissue of pia mater Wastes and unnecessary solutes absorbed Section of choroid plexus (b) CSF formation by choroid plexuses Cavity of ventricle CSF forms as a filtrate containing glucose, oxygen, vitamins, and ions (Na +, Cl –, Mg 2+, etc.)
Copyright © 2010 Pearson Education, Inc. Blood-Brain Barrier Helps maintain a stable environment for the brain Separates neurons from some bloodborne substances
Copyright © 2010 Pearson Education, Inc. Blood-Brain Barrier Selective barrier Allows nutrients to move by facilitated diffusion Allows any fat-soluble substances to pass, including alcohol, nicotine, and anesthetics Formed by Continuous endothelium of capillary walls Basal lamina Feet of astrocytes Absent in brain areas that “need to know” about blood composition (vomiting center, etc.)
Copyright © 2010 Pearson Education, Inc. Figure 11.3a Capillary Neuron Astrocyte Blood brain barrier Notice feet of astrocytes wrapping around capillaries
Copyright © 2010 Pearson Education, Inc. Traumatic brain injuries Concussion—temporary alteration in function Contusion—permanent damage Subdural or subarachnoid hemorrhage—may force brain stem through the foramen magnum, resulting in death Cerebral edema—swelling of the brain associated with traumatic head injury Contrecoup injury (to opposite side)