BRAIN PART I (A & B): VENTRICLES & MENINGES

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1 BRAIN PART I (A & B): VENTRICLES & MENINGES Cranial Meninges Cranial meninges are continuous with spinal meninges Dura mater: inner layer (meningeal layer) outer layer (endosteal layer) fused to periosteum venous sinuses between 2 layers Arachnoid mater: subarachnoid space Pia mater: adhered directly to brain surface Ventricles of the Brain 4 ventricles Lateral ventricles (2) Septum pellucidum Third ventricle Connects to 4th ventricle via cerebral aqueduct Fourth ventricle Connects to central canal of spinal cord Cerebral Spinal Fluid Choroid plexus Produces CSF in ventricles ~500 ml/day Arachnoid villi Reabsorbs CSF, superior cranial region Returns CSF to blood in venous sinus Problems Hydrocephaly watery brain Cerebral Spinal Fluid Pathway CSF circulates: from choroid plexus thorough ventricles to central canal of spinal cord into subarachnoid space around cauda equina, the spinal cord, and brain reabsorbed by arachnoid villi around brain

2 Functions of CSF Cushions delicate neural structures Supports brain Transports nutrients, chemical messengers, and waste products Blood-Brain Barrier Selective barrier between capillaries and extracellular space around brain Molecules that can pass freely: H2O, CO2, O2, glucose Fat soluble substances Molecules that are regulated: Ions, ph, neurotransmitters & hormones Molecules that do not cross: Large proteins, many medications Blood Supply to the Brain Supplies nutrients and oxygen to brain Delivered by internal carotid arteries and vertebral arteries Removed from dural sinuses by internal jugular veins BRAIN PART I (C): VENTRICLE FORMATION Embryonic Development of the Brain Neural tube formation First month of development Brain and spinal cord Lumen becomes ventricles of the brain and central canal if the spinal cord Problems Spina Bifida and Anencephaly Detected by alpha (α) fetal protein Prevented by folic acid

3 BRAIN PART II (A): CEREBRUM Regions of the Brain Cerebrum Diencephalon Brain stem Mesencephalon Pons Medulla oblongata Cerebellum Gray and White Matter Gray matter: in cerebral cortex and basal nuclei cell bodies, dendrites, axon terminals (where synapses occur) White matter: myelinated axons Structures of the Cerebrum Gyri and sulci of neural cortex Lobes: divisions of hemispheres: Frontal Parietal Temporal Occipital Divisions of the Cerebrum Longitudinal fissure: separates cerebral hemispheres Central sulcus divides: frontal lobe from parietal lobe Lateral sulcus divides: frontal lobe from temporal lobe Parieto-occipital sulcus divides: parietal lobe from occipital lobe Functional Principles of the Cerebrum Each cerebral hemisphere receives sensory information from, and sends motor commands to, the opposite side of body The 2 hemispheres have different functions although their structures are alike Hemispheric Lateralization Functional differences between left and right hemispheres Each cerebral hemisphere performs certain functions not performed by the opposite hemisphere

4 Motor and Sensory Areas of the Cortex Central sulcus separates motor and sensory areas Motor Areas (Frontal Lobe) Primary motor cortex: is the surface of precentral gyrus Premotor cortex (somatic motor association area): coordinates learned movements Broca s area: control muscles used in speech Somatosensory Areas (Parietal Lobe) Primary somatosensory cortex: surface of postcentral gyrus Proprioception, touch, pressure, pain, vibration, taste, and temperature Somatosensory association area: Interpretation of sensations Gustatory area: Region for taste sensation Cerebral Cortex: Sensory Areas Parietal Lobes: Feel and Taste Temporal Lobes: Hear and Smell Occipital Lobes: Vision Hear & Smell (Temporal Lobe) Primary auditory cortex: Receives information about pitch and volume Auditory association area: Interpretation of sounds Wernicke s area: (different from text) Understanding (interpreting) words we hear Olfactory cortex: Region for smell sensation Medial (deep) portion of temporal lobe Vision (Occipital Lobe) Primary visual cortex: Receives information about light, dark, shape, and color Visual association area: Interpretation of visual stimuli recognition

5 Higher-Order Thinking Prefrontal cortex of frontal lobe: integrates information from association areas performs abstract intellectual activities predicting consequences of actions decision making planning and future comprehension General Interpretive Area (NOT called Wernicke s area ) Complex, learned reflexes Language Integrative Areas Left side Broca s area: speech formation (motor control of muscles) Wernicke s area: speech comprehension (understanding words) Right side Affective Language area for Broca s put emotion into speech/words Affective Language area for Wernicke s understand emotion in other s speech/words

6 BRAIN PART II (B): ELECTROCENCEPHALOGRAM What are the origins and significance of the major categories of brain waves seen in an electroencephalogram? Monitoring Brain Activity Electroencephalogram (EEG): patterns of electrical activity are monitored 4 Categories of Brain Waves Alpha (α) waves: healthy, awake adults at rest Beta (β) waves: adults concentrating or mentally stressed Theta waves: found in children found in intensely frustrated adults may indicate brain disorder in adults Delta waves: during sleep found in awake adults with brain damage

7 BRAIN PART III (A): DIENCEPHALON What are the main components of the diencephalon and their functions? The Diencephalon Epithalamus Thalamus Hypothalamus Epithalamus, Thalamus and Hypothalamus Epithalamus: melatonin secretion via pineal gland Thalamus: relays and processes sensory information Hypothalamus: hormone production emotion autonomic function connected to pituitary gland via infundibulum The Hypothalamus Lies below thalamus Mamillary bodies: process olfactory and other sensory information control reflex eating movements Infundibulum: connects hypothalamus to pituitary gland Hypothalamus Functions (some) Controls ANS functions Blood pressure, heart rate, peristalsis, etc. Emotional response Pain, pleasure, fear, rage, libido Body temperature Food intake and satiety Water balance and thirst Sleep-wake cycle timing Controls pituitary gland

8 BRAIN PART III (B): LIMBIC SYSTEM What are the main components of the limbic system, their locations, and functions? The Limbic System Conscious functions of cerebral cortex with autonomic functions of brain stem Memory storage and retrieval Connects smell, memory, emotions Specific Parts of the Limbic System Amygdaloid body: interfaces limbic system, cerebrum, sensory systems (smell), emotions Hippocampus: short-term to long-term memory

9 BRAIN PART IV: BRAIN STEM & CEREBELLUM Brain Stem Mesencephalon (midbrain) Pons Medulla oblongata Structures of the Mesencephalon 2 pairs of sensory nuclei (corpora quadrigemina): superior colliculus (visual) inferior colliculus (auditory) cerebral peduncles: nerve fiber bundles contain: descending fibers to cerebellum motor command fibers reticular activating system (allow or block sensory input, see ANS chapter) The Pons Nuclei involved with respiration: apneustic center, pneumotaxic center Work with respiratory center in medulla oblongata The Medulla Oblongata Links spinal cord to brain Coordinates complex autonomic functions: Cardiovascular center Cardiac (HR, contractility) Vasomotor (peripheral blood flow) Respiratory rhythmicity center Motor and sensory nerve tracts cross over Reticular formation Alertness Functions of the Cerebellum Adjusts postural muscles Fine-tunes conscious and subconscious movements Pathology: Ataxia:ffrom trauma or stroke disturbs muscle coordination Arbor vitae