BODY SYSTEMS REVIEW NERVOUS SYSTEM

Complex and highly organized Coordinates all of the many activities of the body Allows the body to respond and adapt to changes that occur both inside and outside the body

NEURON Neuron is also called a nerve cell Basic structural unit of the nervous system Parts of neuron Cell body Nucleus Dendrites Axon Myelin sheath Schwann’s cells Node of Ranvier Axon Terminals

NERVES Combination of nerve fibers Located outside the brain and spinal cord Afferent Nerves Sensory nerves Carry messages from all parts of the body to the brain and spinal cord Efferent Nerves Motor nerves Carry messages from the brain and spinal cord to the muscles and glands Associative—internuncial nerves Carry both sensory and motor messages

THE NERVOUS SYSTEM Consists of two main divisions Central nervous system (CNS) Consists of the brain and spinal cord Peripheral nervous system Somatic nervous system Autonomic nervous system

CENTRAL NERVOUS SYSTEM THE BRAIN Cerebrum Cerebellum Diencephalon Midbrain Pons Medulla oblongata

CENTRAL NERVOUS SYSTEM THE SPINAL CORD Continues down from medulla oblongata and ends at the 1 st or 2 nd lumbar vertebrae Surrounded and protected by the vertebrae Responsible for many reflex actions Carries sensory (afferent) messages to the brain Carries motor (efferent) message from the brain

CENTRAL NERVOUS SYSTEM Meninges - Three membranes that cover and protect the brain and spinal cord 1.Dura mater – thick, tough outer layer 2.Arachnoid membrane – middle layer, delicate and web- like 3.Pia mater – innermost layer, closely attached to the brain and spinal cord, contains blood vessels that nourish the nerve tissue

CENTRAL NERVOUS SYSTEM Ventricles – Hollow spaces that connect with each other and with the space under the arachnoid membrane (the brain has 4 ventricles) Filled with clear, colorless fluid called cerebrospinal fluid Cerebrospinal Fluid Serves as a shock absorber to protect the brain and spinal cord Carries nutrients to some parts of the brain and helps to remove waste

PERIPHERAL NERVOUS SYSTEM Consists of the somatic nervous system and the autonomic nervous system (ANS) Somatic Nervous System Contains 12 pairs of cranial nerves and their branches Some are responsible for special senses, others receive general sensations such as touch, pressure, pain, and temperature Send out impulses for involuntary and voluntary muscle control Contains 31 pairs of spinal nerves and their branches Carry messages to and from the spinal cord 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal pairs

PERIPHERAL NERVOUS SYSTEM Autonomic Nervous System-2 divisions of the ANS (sympathetic and parasympathetic) 1.Sympathetic Nervous System Prepares the body to act (fight or flight) Increases heart rate, respiration, and blood pressure Decreases the activity in the digestive tract 2.Parasympathetic Nervous System Counteracts the sympathetic nervous system Returns the body to normal after the threat has passed

DISEASES AND ABNORMAL CONDITIONS Amyotrophic lateral sclerosis (ALS) Carpal tunnel syndrome Cerebral palsy Cerebrovascular accident (CVA) Encephalitis Epilepsy or seizure syndrome Hydrocephalus Meningitis Multiple sclerosis (MS) Neuralgia Paralysis Parkinson’s disease Shingles or herpes zoster