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Central Nervous System (CNS) •CNS develops from the embryonic neural tube •The neural tube becomes the brain and spinal cord •The opening of the neural tube becomes the ventricles •Four chambers within the brain •Filled with cerebrospinal fluid © 2012 Pearson Education, Inc. Cerebral hemisphere Outline of diencephalon Midbrain Cerebellum Brain stem (a) 13 weeks © 2012 Pearson Education, Inc. Figure 7.12a Regions of the Brain •Cerebral hemispheres (cerebrum) •Diencephalon •Brain stem •Cerebellum © 2012 Pearson Education, Inc. Cerebral hemisphere Diencephalon Cerebellum Brain stem (b) Adult brain © 2012 Pearson Education, Inc. Figure 7.12b Regions of the Brain: Cerebrum •Cerebral Hemispheres (Cerebrum) •Paired (left and right) superior parts of the brain •Includes more than half of the brain mass •The surface is made of ridges (gyri) and grooves (sulci) © 2012 Pearson Education, Inc. Precentral gyrus Central sulcus Postcentral gyrus Parietal lobe Frontal lobe Parieto-occipital sulcus (deep) Lateral sulcus Occipital lobe Temporal lobe Cerebellum Pons Medulla oblongata Cerebral cortex (gray matter) Gyrus Spinal cord Sulcus Fissure (a deep sulcus) (a) © 2012 Pearson Education, Inc. Cerebral white matter Figure 7.13a Regions of the Brain: Cerebrum •Lobes of the cerebrum •Fissures deep grooves that divide the cerebrum into lobes •Surface lobes of the cerebrum •Frontal lobe •Parietal lobe •Occipital lobe •Temporal lobe © 2012 Pearson Education, Inc. Parietal lobe Left cerebral hemisphere Frontal lobe Occipital lobe Temporal lobe Cephalad Caudal (b) © 2012 Pearson Education, Inc. Brain stem Cerebellum Figure 7.13b Regions of the Brain: Cerebrum •Specialized areas of the cerebrum •Primary somatic sensory area •Receives impulses from the body’s sensory receptors •Located in parietal lobe •Primary motor area •Sends impulses to skeletal muscles •Located in frontal lobe •Broca’s area •Involved in our ability to speak © 2012 Pearson Education, Inc. Primary motor area Premotor area Anterior association area • Working memory and judgment • Problem solving • Language comprehension Broca’s area (motor speech) Olfactory area Central sulcus Primary somatic sensory area Gustatory area (taste) Speech/language (outlined by dashes) Posterior association area Visual area Auditory area (c) © 2012 Pearson Education, Inc. Figure 7.13c © 2012 Pearson Education, Inc. Figure 7.14 Regions of the Brain: Cerebrum •Cerebral areas involved in special senses •Gustatory area (taste) •Visual area •Auditory area •Olfactory area © 2012 Pearson Education, Inc. Regions of the Brain: Cerebrum •Interpretation areas of the cerebrum •Speech/language region •Language comprehension region •General interpretation area © 2012 Pearson Education, Inc. Primary motor area Premotor area Anterior association area • Working memory and judgment • Problem solving • Language comprehension Broca’s area (motor speech) Olfactory area Central sulcus Primary somatic sensory area Gustatory area (taste) Speech/language (outlined by dashes) Posterior association area Visual area Auditory area (c) © 2012 Pearson Education, Inc. Figure 7.13c Regions of the Brain: Cerebrum •Layers of the cerebrum •Gray matter outer layer in the cerebral cortex composed mostly of neuron cell bodies •White matter fiber tracts deep to the gray matter •Corpus callosum connects hemispheres •Basal nuclei islands of gray matter buried within the white matter © 2012 Pearson Education, Inc. Longitudinal fissure Lateral ventricle Basal nuclei (basal ganglia) Superior Association fibers Commissural fibers (corpus callosum) Corona radiata Fornix Thalamus Internal capsule Third ventricle Pons Projection fibers Medulla oblongata © 2012 Pearson Education, Inc. Figure 7.15 Cerebral hemisphere Corpus callosum Choroid plexus of third ventricle Occipital lobe of cerebral hemisphere Thalamus (encloses third ventricle) Pineal gland (part of epithalamus) Corpora quadrigemina Midbrain Cerebral aqueduct Third ventricle Anterior commissure Hypothalamus Optic chiasma Pituitary gland Mammillary body Pons Medulla oblongata Spinal cord Cerebral peduncle of midbrain Fourth ventricle Choroid plexus Cerebellum (a) © 2012 Pearson Education, Inc. Figure 7.16a Homeostatic Imbalance •Huntington’s Disease •Genetic disease that strikes during middle age and leads to massive degeneration of the basal nuclei and later the cerebral cortex •Initial symptoms include wild, jerky, and almost continuous flapping movements that are involuntary •Usually fatal within 15 years of the onset of symptoms © 2012 Pearson Education, Inc. Homeostatic Imbalance •Parkinson’s Disease •Typically strikes people in their 50’s and 60’s •Results from a degeneration of the dopamine releasing neurons of the substantia nigra of the midbrain •People have persistent tremors at rest (head nodding and “pill rolling” movement of the fingers), forward bent walking posture, and shuffling gait •Ex: Muhammad Ali and Michael J. Fox © 2012 Pearson Education, Inc. Regions of the Brain: Diencephalon •Sits on top of the brain stem •Enclosed by the cerebral hemispheres •Made of three parts •Thalamus •Hypothalamus •Epithalamus © 2012 Pearson Education, Inc. Cerebral hemisphere Diencephalon Cerebellum Brain stem (b) Adult brain © 2012 Pearson Education, Inc. Figure 7.12b Cerebral hemisphere Corpus callosum Choroid plexus of third ventricle Occipital lobe of cerebral hemisphere Thalamus (encloses third ventricle) Pineal gland (part of epithalamus) Corpora quadrigemina Midbrain Cerebral aqueduct Third ventricle Anterior commissure Hypothalamus Optic chiasma Pituitary gland Mammillary body Pons Medulla oblongata Spinal cord Cerebral peduncle of midbrain Fourth ventricle Choroid plexus Cerebellum (a) © 2012 Pearson Education, Inc. Figure 7.16a Radiations to cerebral cortex Visual impulses Reticular formation Ascending general sensory tracts (touch, pain, temperature) Auditory impulses Descending motor projections to spinal cord (b) © 2012 Pearson Education, Inc. Figure 7.16b Regions of the Brain: Diencephalon •Thalamus •Surrounds the third ventricle •The relay station for sensory impulses •Transfers impulses to the correct part of the cortex for localization and interpretation © 2012 Pearson Education, Inc. Regions of the Brain: Diencephalon •Hypothalamus •Under the thalamus •Important autonomic nervous system center •Helps regulate body temperature •Controls water balance •Regulates metabolism •Houses the limbic center for emotions •Regulates the nearby pituitary gland •Produces two hormones of its own © 2012 Pearson Education, Inc. Regions of the Brain: Diencephalon •Epithalamus •Forms the roof of the third ventricle •Houses the pineal body (an endocrine gland) •Includes the choroid plexus—forms cerebrospinal fluid © 2012 Pearson Education, Inc. Regions of the Brain: Brain Stem •Attaches to the spinal cord •Parts of the brain stem •Midbrain •Pons •Medulla oblongata © 2012 Pearson Education, Inc. Cerebral hemisphere Corpus callosum Choroid plexus of third ventricle Occipital lobe of cerebral hemisphere Thalamus (encloses third ventricle) Pineal gland (part of epithalamus) Corpora quadrigemina Midbrain Cerebral aqueduct Third ventricle Anterior commissure Hypothalamus Optic chiasma Pituitary gland Mammillary body Pons Medulla oblongata Spinal cord Cerebral peduncle of midbrain Fourth ventricle Choroid plexus Cerebellum (a) © 2012 Pearson Education, Inc. Figure 7.16a Regions of the Brain: Brain Stem •Midbrain •Mostly composed of tracts of nerve fibers •Has two bulging fiber tracts— cerebral peduncles •Has four rounded protrusions— corpora quadrigemina •Reflex centers for vision and hearing © 2012 Pearson Education, Inc. Regions of the Brain: Brain Stem •Pons •The bulging center part of the brain stem •Mostly composed of fiber tracts •Includes nuclei involved in the control of breathing © 2012 Pearson Education, Inc. Regions of the Brain: Brain Stem •Medulla oblongata •The lowest part of the brain stem •Merges into the spinal cord •Includes important fiber tracts •Contains important control centers •Heart rate control •Blood pressure regulation •Breathing •Swallowing •Vomiting © 2012 Pearson Education, Inc. Regions of the Brain: Brain Stem •Reticular Formation •Diffuse mass of gray matter along the brain stem •Involved in motor control of visceral organs •Reticular activating system (RAS) plays a role in awake/sleep cycles and consciousness © 2012 Pearson Education, Inc. Radiations to cerebral cortex Visual impulses Reticular formation Ascending general sensory tracts (touch, pain, temperature) Auditory impulses Descending motor projections to spinal cord (b) © 2012 Pearson Education, Inc. Figure 7.16b Regions of the Brain: Cerebellum •Two hemispheres with convoluted surfaces •Provides involuntary coordination of body movements © 2012 Pearson Education, Inc. Cerebral hemisphere Corpus callosum Choroid plexus of third ventricle Occipital lobe of cerebral hemisphere Thalamus (encloses third ventricle) Pineal gland (part of epithalamus) Corpora quadrigemina Midbrain Cerebral aqueduct Third ventricle Anterior commissure Hypothalamus Optic chiasma Pituitary gland Mammillary body Pons Medulla oblongata Spinal cord Cerebral peduncle of midbrain Fourth ventricle Choroid plexus Cerebellum (a) © 2012 Pearson Education, Inc. Figure 7.16a Homeostatic Imbalance •Ataxia •Usually occurs if the cerebellum is damaged (blow to the head, tumor, or stroke) •Movements become clumsy and disorganized •Victims cannot keep their balance because of the loss of muscle coordination •Unable to touch their finger to their nose while their eyes are closed © 2012 Pearson Education, Inc. Protection of the Central Nervous System •Scalp and skin •Skull and vertebral column •Meninges the three connective tissue membranes covering and protecting the CNS structures •Cerebrospinal fluid (CSF) •Blood-brain barrier © 2012 Pearson Education, Inc. Skin of scalp Periosteum Bone of skull Superior sagittal sinus Subdural space Subarachnoid space Periosteal Meningeal Dura mater Arachnoid mater Pia mater Arachnoid villus Blood vessel Falx cerebri (in longitudinal fissure only) (a) © 2012 Pearson Education, Inc. Figure 7.17a Meninges •Dura mater •Tough outermost layer •Double-layered external covering • Periosteum—attached to inner surface of the skull • Meningeal layer—outer covering of the brain •Folds inward in several areas • Falx cerebri • Tentorium cerebelli © 2012 Pearson Education, Inc. Meninges •Arachnoid layer •Middle layer •Web-like extensions span the subarachnoid space •Arachnoid villi reabsorb cerebrospinal fluid •Pia mater •Internal layer •Clings to the surface of the brain © 2012 Pearson Education, Inc. Occipital lobe Tentorium cerebelli Cerebellum Arachnoid mater over medulla oblongata (b) © 2012 Pearson Education, Inc. Skull Scalp Superior sagittal sinus Dura mater Transverse sinus Temporal bone Figure 7.17b Homeostatic Imbalance •Meningitis •An inflammation of the meninges •Serious threat to the brain because bacterial or viral meningitis may spread into the nervous tissue of the CNS •Usually diagnosed by taking a sample of CSF through a lumbar puncture © 2012 Pearson Education, Inc. Cerebrospinal Fluid (CSF) •Similar to blood plasma composition •Formed by the choroid plexus •Choroid plexuses–capillaries in the ventricles of the brain •Forms a watery cushion to protect the brain •Circulated in arachnoid space, ventricles, and central canal of the spinal cord © 2012 Pearson Education, Inc. Cerebrospinal Fluid (CSF) Pathway of Flow 1. CSF is produced by the choroid plexus of each ventricle. 2. 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. 3. CSF flows through the subarachnoid space. 4. CSF is absorbed into the dural venous sinuses via the arachnoid villi. © 2012 Pearson Education, Inc. Lateral ventricle Anterior horn Septum pellucidum Interventricular foramen Inferior horn Third ventricle Lateral aperture Cerebral aqueduct Fourth ventricle Central canal (a) Anterior view © 2012 Pearson Education, Inc. Figure 7.18a Lateral ventricle Anterior horn Posterior horn Interventricular foramen Third ventricle Inferior horn Cerebral aqueduct Median aperture Fourth ventricle Lateral aperture Central canal (b) Left lateral view © 2012 Pearson Education, Inc. Figure 7.18b 4 Superior sagittal sinus Arachnoid villus Subarachnoid space Arachnoid mater Meningeal dura mater Periosteal dura mater Right lateral ventricle (deep to cut) Choroid plexus Corpus callosum 1 Interventricular foramen Third ventricle 3 Cerebral aqueduct Lateral aperture Fourth ventricle Median aperture Central canal of spinal cord (c) CSF circulation Choroid plexus of fourth ventricle 2 1 CSF is produced by the choroid plexus of each ventricle. 2 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. 3 CSF flows through the subarachnoid space. 4 CSF is absorbed into the dural venous sinuses via the arachnoid villi. © 2012 Pearson Education, Inc. Figure 7.18c Homeostatic Imbalance •Hydrocephalus •CSF accumulates and exerts pressure on the brain if not allowed to drain •Possible in an infant because the skull bones have not yet fused •In adults, this situation results in brain damage © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc. Figure 7.19 Blood-Brain Barrier •Includes the least permeable capillaries of the body •Excludes many potentially harmful substances •Useless as a barrier against some substances •Fats and fat soluble molecules •Respiratory gases •Alcohol •Nicotine •Anesthesia © 2012 Pearson Education, Inc. Traumatic Brain Injuries •Concussion •Slight brain injury •No permanent brain damage unless multiple concussions occur •Contusion •Nervous tissue destruction occurs •Nervous tissue does not regenerate •Cerebral edema •Swelling from the inflammatory response •May compress and kill brain tissue © 2012 Pearson Education, Inc. Cerebrovascular Accident (CVA) or Stroke •Result from a ruptured blood vessel supplying a region of the brain •Brain tissue supplied with oxygen from that blood source dies •Loss of some functions or death may result •Hemiplegia One-sided paralysis •Aphasis Damage to speech center in left hemisphere •Transient Ischemic Attack (TIA) temporary brain ischemia (restriction of blood flow) •Warning signs for more serious CVAs © 2012 Pearson Education, Inc. Alzheimer’s Disease •Progressive degenerative brain disease •Mostly seen in the elderly, but may begin in middle age •Structural changes in the brain include abnormal protein deposits and twisted fibers within neurons •Victims experience memory loss, irritability, confusion, and ultimately, hallucinations and death © 2012 Pearson Education, Inc.