BSC2085 Exam 3 Study Guide Lesson 15 The Brain Adult Human Brain Ranges 750 cc 2100 cc o Still functionally normal at extreme sizes Contains 97 of body s neural tissue Average weight 1 4 kg 3 lbs The Brain Large delicate mass of neural tissue Contains internal passageways chambers filled with cerebrospinal fluid CSF Each major brain region has specific functions o From bottom to top brain functions become more complex more variable Conscious thought intelligence produced in the neural cortex of the cerebral hemispheres Major Regions of the Brain o Cerebrum Largest part of the brain Controls higher mental functions Divided into left right cerebral hemispheres Surface layer made up of gray matter neural cerebral cortex Folded surface increases surface area Gyri Gyrus Elevated ridges Sulci Sulcus Shallow depressions Fissures Deep grooves o Cerebellum Second largest part of the brain Coordinates repetitive body movements Ex Walking Two 2 hemispheres Covered by cerebellar cortex 1 BSC2085 Exam 3 Study Guide o Diencephalon Located under cerebrum cerebellum Links cerebrum with brain stem Divisions of the Diencephalon Thalamus left right Relays processes sensory information Hypothalamus Involved in hormone production autonomic function emotion o Connected to the pituitary gland hypophysis by o Hypophysis A major endocrine gland connecting nervous infundibulum and endocrine system o Brain Stem Processes information between spinal cord cerebrum cerebellum Includes Midbrain Mesencephalon Processes sight sound and associated reflexes maintains consciousness Pons Connects cerebellum to brain stem is involved in somatic skeletal muscle visceral motor control Medulla Oblongata Connects brain to spinal cord relays information and regulates autonomic functions heart rate blood pressure digestion 2 BSC2085 Exam 3 Study Guide Ventricles of the Brain o Each cerebral hemisphere contains one large lateral ventricle Separated by a thin medial partition septum pellucidum o Third Ventricle ventricle of the diencephalon Lateral ventricles communicate with third ventricle via interventricular foramen o Fourth Ventricle Connected to the third ventricle via narrow canal in midbrain called the cerebral aqueduct Ventricle extends into medulla oblongata Becomes continuous with central canal of the spinal cord 3 BSC2085 Exam 3 Study Guide Brain Protection and Support Three 3 forms of physical protection o Bones of the cranium o Cranial meninges o Cerebrospinal fluid Biochemical isolation Blood brain barrier Cranial Meninges o Protect the brain from cranial trauma continuous with spinal meninges o Three 3 Layers Dura Mater Inner fibrous layer meningeal layer outer fibrous layer endosteal layer fused with periosteum Venous sinuses found between the two Arachnoid Mater Covers the brain subarachnoid space located between arachnoid mater pia mater Pia Mater Attaches to brain surface by astrocytes o Dural Folds Folded inner layer of dura mater Extend into cranial cavity Stabilize support brain Contain collecting veins dural sinuses Three largest dural folds Falx Cerebri Projects between the cerebral hemispheres Tentorium Cerebelli Separates cerebellum cerebrum Falx Cerebelli Divides cerebellar hemisphere below the tentorium cerebelli 4 BSC2085 Exam 3 Study Guide Cerebral Spinal Fluid CSF o Surrounds all exposed surfaces of CNS o Interchanges with interstitial fluid of brain o Functions of CSF Cushions delicate neural structures 5 BSC2085 Exam 3 Study Guide Supports brain Transports nutrients chemical messengers waste products o Produced by choroid plexus 500 mL day Consists of specialized ependymal cells capillaries Cells of the choroid plexus o Secrete CSF into ventricles o Remove waste products from CSF o Adjust composition of CSF o CSF circulates From choroid plexus through ventricles To central canal of spinal cord Into subarachnoid space via two lateral apertures one medial aperture around the brain spinal cord cauda equina o Sample of CSF can be taken by spinal lumbar tap 6 BSC2085 Exam 3 Study Guide Blood Supply to the Brain o Blood supplies nutrients oxygen to brain o Delivered by internal carotid arteries vertebral arteries o Removed from dural sinuses by internal jugular veins o Head injury that causes epidural or subdural bleeding can compress brain tissue o Cerebrovascular Disease Disorders interfere with blood circulation to brain 7 BSC2085 Exam 3 Study Guide Stroke Cerebrovascular Accident CVA Shuts off blood to portion of Blood Brain Barrier BBB brain neurons die o Isolates CNS neural tissue from general circulation o Formed by network of tight junctions Between endothelial cells of CNS capillaries o Lipid soluble compounds O2 CO2 steroids and prostaglandins can bypass through endothelial cells Diffuse into interstitial fluid of brain spinal cord o Astrocytes control blood brain barrier by releasing chemicals that control permeability of endothelium Blood CSF Barrier o Formed by special ependymal cells o Surrounds capillaries of choroid plexus o Limits movement of compounds transferred o Allows chemical composition of blood CSF to differ Movement of material between the two is selective directional to regulate ion concentration and pH Four 4 Breaks in the Blood Brain Barrier o 1 Portions of hypothalamus Secrete hypothalamic hormones o 2 Posterior lobe of pituitary gland Secretes hormones ADH oxytocin o 3 Pineal gland Pineal secretions o 4 Choroid plexus Where special ependymal cells maintain blood CSF barrier 8 BSC2085 Exam 3 Study Guide Medulla Oblongata Allows brain spinal cord to communicate Coordinates complex autonomic reflexes Controls visceral functions Nuclei in the medulla 9 BSC2085 Exam 3 Study Guide o Autonomic nuclei control visceral activities cardiovascular respiratory reflexes o Sensory motor nuclei of cranial nerves o Relay stations along sensory motor pathways Pons Sensory motor nuclei of cranial nerves V VI VII VIII o Cranial nerves 5 8 Nuclei involved with respiration o Apneustic center pneumotaxic center modify respiratory rhythmicity center activity Nuclei that process and relay information to and from cerebellum Ascending descending transverse tracts o Transverse Fibers axons Link nuclei of pons with opposite cerebellar hemisphere Cerebellum Functions of the cerebellum o Adjusts postural muscles o Fine tunes conscious subconscious movements Disorders of the cerebellum o Ataxia Lack of voluntary coordination of muscle movements Damage from trauma or stroke Disturbs muscle
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