CNS General Structure Composed of brain and spinal cord Brain enclosed in skull and surrounded by a tough three-layer membrane called meninges The meninges forms the blood brain barrier – determines what chemicals reach the brain
Cerebrospinal Fluid Circulates between two layers in the meninges and also in spinal cord Functions: Shock absorber Transport medium Spinal Tap – extraction of cerebrospinal fluid to diagnose infection
Spinal Cord Carries sensory nerve messages to the brain and motor nerve messages from the brain to effectors Emerges from skull through opening called foramen magnum and extends down through canal in backbone
Spinal Cord Organization Two types of nerve tissue White matter – myelinated nerve fibres from sensory and motor neurons Grey matter – nonmyelinated interneurons Interneurons form nerve tracts that connect spinal cord with brain Dorsal nerve tract – sensory info into spinal cord Ventral nerve tract – motor info from spinal cord to effectors
The Brain
Brain Structure Three distinct regions: forebrain, midbrain and hindbrain Forebrain contains: Olfactory lobes – receive info about smell Cerebrum – major coordinating centre Two hemispheres Contain regions associated with speech, reasoning, memory, and other higher functions Surface called cerebral cortex – made of grey matter with many folds to increase surface area
Lobes of the Cerebrum Cerebral cortex divided into parts called lobes: the frontal lobe the parietal lobe the temporal lobe the occipital lobe
The frontal lobe is the center for voluntary movement is called the “motor area” (movement) includes the prefrontal area, for intelligence, creativity, memory, and personality.
The parietal lobe Collects, recognizes, and organizes sensations: feelings of pain temperature touch position movement
The temporal lobe processes auditory (hearing) information stores auditory (hearing) and visual (seeing) memories
The occipital lobe is at the back of the cerebral hemisphere involves vision visual memory eye movements
Cerebral Hemispheres Two cerebral hemispheres are not mirror images of each other Right side associated with visual patterns or spatial awareness Left side linked to verbal skills Some people may have one side more dominant which may affect the way they learn Corpus callosum – bundle of nerve fibres connecting two hemispheres
Midbrain Less developed than forebrain Consists of four spheres of grey matter Mostly composed of tracts of nerve fibers Relay centre for some eye and ear reflexes
Hindbrain Joins to spinal cord Major regions: Cerebellum Pons Largest section of hindbrain Controls limb movements and balance Pons Relay station passes info between two regions of cerebellum Medulla oblongata Controls involuntary muscle action (breathing movements, heart rate, etc)