The Nervous System Responsible for Sending, Receiving, and Processing nerve impulses. Includes 3 sub-systems working together: Central – analyze data, issues impulses (ie. Responses) Peripheral – carries impulses to and from body structures Autonomic – regulation and control of body functions Brain is the primary component of this system. It is protected by an outer covering, called the Dura mater. Without the dura mater, the brain weighs approx. 3 pounds, comprising about 97% of the CNS. The brain issues nerve impulses, processes data, and engages in higher order thought processes. Divided into 3 main parts: the large cerebrum, the smaller cerebellum, and the brainstem leading to the spinal cord. The brainstem is further divided into the medulla oblongata, the midbrain, and the pons.

The Components of the Nervous System

The Brain - 6 Divisions Cerebrum – largest part, divided into 2 hemispheres, then further subdivided into 4 lobes. Controls sensory / motor activities, and intelligence. Cerebellum – 2nd largest part, lying beneath and behind the cerebrum. Coordinates muscle function and balance. Brainstem – located below cerebrum, in front of cerebellum. Controls autonomic functions, muscle tone, eye movement. Diencephalon – located between the cerebrum and brainstem, containing the thalamus and hypothalamus. Thalamus – screening and relay centre for sensory stimuli, pain awareness Hypothalamus – control centre for appetite, body temperature, emotions Limbic System – located within the cerebrum. Responsible for screening info entering the cerebral cortex. Regulates basic drives (hunger, aggression, emotion) RA System – A neuron network within the cerebrum which directs incoming stimuli to appropriate areas for analysis. Crucial for maintaining consciousness

The Proprioceptor System Specialized receptors located within tendons, muscles, and joints Provide sensory information (ex. state of muscle contraction) through the primary use of two sensory receptors: golgi tendon organs and muscle spindles Continuously monitor muscle actions “Tell” the nervous system about the state of muscle contraction Act as a kind of safety device allowing the nervous system to respond accordingly

Lobes of the Cerebrum Lobe Name Location Responsibility 1 Occipital In the back of the brain Processes sensory information from the eyes. 2 Temporal On the side of the brain Processes sensory information from the ears 3 Frontal In the front of the brain Controls voluntary movement, personality, intelligence, and speech 4 Parietal Located in the center of the brain, behind frontal lobe Controls sensory information for skin receptors, as well as processing information regarding body position

Spinal Cord and Head Injuries Spinal cord injuries: Damage to the spine can result in an inability to send impulses to body parts Nerves above injury keep working, nerves below may not Paraplegia: Injury prevents use of legs but not arms Quadriplegia: Injury prevents movement of both arms and legs © iStockphoto.com/”caracterdesign”

Spinal Cord and Head Injuries Most common head injury is a concussion: Occurs when brain literally hits the skull; often involves injury to nerve fibres Ranges from mild to severe Symptoms can include: headaches, fatigue, memory problems, or slurred speech © iStockphoto.com/”AlexKalina”

Nervous System Disorders Hydrocephalus – often referred to as “water on the brain”, caused by an over-production of cerebrospinal fluid or a blockage that prevents proper drainage. Fluid collects in the brain, increasing pressure and squeezing the brain against the skull. Sometimes children with the condition have shunts inserted to drain the fluid into the stomach. Parkinson’s Disease – involves degeneration of tissue in the midbrain, rendering it incapable of producing dopamine (a neurotransmitter). The disease becomes progressively worse with age. The midbrain abnormality causes muscle tremors, slow movements, partial facial paralysis, and general weakness. Cerebral Palsy – caused by abnormal functioning cerebrum. It is characterized by difficulties with muscle coordination. The cause is theorized to result from a lack of oxygen to the developing fetus; severity of symptoms varies among individuals. Encephalitis – sometimes called the “sleeping sickness”, patients may experience apathy, double vision, and extreme weakness. This is due to an inflammation of the brain, usually caused by a viral or bacterial infection.