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The Central Nervous System The structural and functional centre for entire nervous system Consists of the brain and spinal cord Made up of: 1. Grey Matter (mostly cell bodies, dendrites and short unmyelinated axons). Found on outside areas of brain and H-shaped part of spinal cord 2. White Matter (myelinated axons) Found in outer area of spinal cord and inner regions of brain The Spinal Cord A column of nerve tissue that extends out of skull and downward through a canal within a backbone Vital communication link between brain and PNS Primary reflex centre Protected by vertebrae, meninges and cerebrospinal fluid Sensory nerves enter spinal cord via Dorsal root and motor nerves leave through ventral root The Brain Maintains homeostasis; centre for intelligence, consciousness and emotions Protected by: 1. The skull 2. Meninges (3-layers of connective tissue) 3. Cerebrospinal fluid (located b/w middle and inner layers of meninges; acts as a cushion as well as nourishes the brain) Meningitis is caused by bacterial or viral infection of outer membrane. Symptoms include fever, vomiting, intense headache, stiff neck and possible rash. Left untreated can cause death. Meningitis is diagnosed by sampling the cerebrospinal fluid. The Brain (made up of 3 regions) forebrain midbrain hindbrain FOREBRAIN Region Cerebrum Thalamus Hypothalamus Olfactory Bulbs Info/ Function Largest part of forebrain Coordinates sensory and motor functions Memory, abstract thought, reasoning, personality, intellect Divided into left(verbal, logic, mathematical skills) and right(visual/spatial awareness- creativity) hemispheres 2 hemispheres connected by a nerve tract called corpus callosum Surface of cerebrum (outer layer) is known as cerebral cortex. It is made of grey matter and contains many folds [called fissures] (increases S.A.) Each hemisphere is divided into 4 lobes: a. Frontal Lobe Motor areas control movement of voluntary muscles association areas are linked to intellectual activities and personality b. Temporal sensory: vision and hearing Association areas linked to memory and interpretation of sensory info c. Parietal sensory: touch and temperature Association areas linked to emotions and interpreting speech d. Occipital sensory: vision association areas interpret visual info Relay station for sensory impulses to cerebrum; coordinating station for sensory signals Helps maintain body’s internal equilibrium Coordinates nerve and hormone functions Processes info about smell Hindbrain Cerebellum Pons Medulla Oblongata Unconscious coordination of movement, balance and muscle tone ‘bridge’ Relay centre b/w cerebrum and both halves of cerebellum Connects forebrain and spinal cord Connects brain and spinal cord Connection b/w PNS and CNS Controls involuntary muscle action Coordinating centre for autonomic system (breathing, heart rate) Midbrain Relay centre for some ear and eye reflexes Relays visual and auditory info b/w hindbrain and forebrain The Peripheral Nervous System 2 divisions: sensory-somatic and autonomic 1. Sensory-Somatic System Brings info about external environment to CNS and sends info back to skeletal muscles Voluntary Composed of 12 cranial nerve and 31 pairs of spinal nerves 2. Autonomic Nervous System Involuntary control of smooth muscle, cardiac muscle, internal organs and glands Brings info about body’s internal environment to CNS and carries signals back to regulate internal environment The ANS uses 2 groups of motor neurons to stimulate target effectors a. Preganglionic neurons (CNS ganglion) b. Postganglionic neurons (ganglion target organ, muscle, gland) Autonomic System further divides into 1. Sympathetic nervous system 2. Parasympathetic nervous system Sympathetic Prepares body for stress, ‘fight or flight’ (increase heart rate, inhibit digestion, release of adrenaline) Nerves originate from middle of spinal cord Short preganglionic nerves (release acetylcholine) Longer postganglionic nerves (release norephinephrine) Parasympathetic brings back body to a normal state (slows heart rate, promotes digestion, BP decreases) nerves originate from lower back(tailbone) and brain long preganglionic nerves (release acetylcholine) shorter postganglionic nerves(release acetylcholine and nitric oxide) IMPORTANT CRANIAL Nerve: vagus (wandering) nerve regulates many internal organs