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Nervous System Outline. Health Occupations. Nervous System Functions. Directs the functions of all human body systems 100 Billion Nerve cells Carry messages from brain to rest of body. Neurons . The basic element of nervous system Highly specialized Vary in function, shape, and size
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Nervous System Outline Health Occupations
Nervous System Functions • Directs the functions of all human body systems • 100 Billion Nerve cells • Carry messages from brain to rest of body
Neurons • The basic element of nervous system • Highly specialized • Vary in function, shape, and size • Separated by synapses • Gaps in between each neuron • Neurotransmitters • Stimulates impulse to jump to next nerve
Neurons • 3 Parts • Cell Body • Have fibers to reach out to send or receive impulses • Dendrites • Thin branching extensions of cell body • Conduct nerve impulses to cell body • Axon • Conducts nerve impulses away from cell body • Covered by a myelin sheath • Fatty tissue that makes impulse travel faster • End of axon has fibers that let the impulse leave the nerve
Neurons • 2 Basic Properties • Excitability • Ability to respond to a stimulus • Conductivity • Ability to transmit a signal
Neurons • 3 Types • Efferent (motor) • Carry information to muscles and glands from CNS • Afferent (sensory) • Carry information from sensory system to CNS • Interneurons • Carry and process sensory information
Neuron bundles = Nerves • Stimulus Receptor Impulse Nerve Receptor
Neuroglias • Support, connect, protect, and remove debris • Do not transmit impulses • Form blood-brain barrier • Permits some chemical substances to reach the brain’s neurons but blocks most others
Central Nervous System (CNS) • Consists of: • Brain • Spinal cord • Center of Control
CNS Functions • Receives and interprets all stimuli • Sends nerve impulses to instruct muscles and glands to take over or respond to certain actions • Causes Voluntary and Involuntary actions
Brain Divisions • Brainstem • Cerebellum • Cerebrum • Diencephalon
Brain Stem • Midbrain • Visual reflexes • Pons • Controls certain respiratory functions • Medulla Oblongata • Regulates heart & lung functions • Swallowing • Vomiting • Coughing • sneezing
Cerebellum • Coordinates musculoskeletal movement • Maintains balance • Posture • Muscle tone
Cerebrum • 2 hemispheres • Left and Right • Cerebral Cortex • Conscious decision making • Four Lobes • Frontal • Moral Behavior, voluntary motor movements • Parietal • Controls and interprets senses and taste • Temporal • Memory, equilibrium, emotion, hearing • Occipital • vision
Diencephalon • Deep portion of brain • Contains: • Thalamus • Hypothalamus • Relay center for sensations • Controls: • Heart rate • Blood pressure • Temperature regulation • Water and electrolyte balance • Digestive functions • Glandular activities
Cerebrospinal Fluid (CSF) • Fills the area between the brain and cranium • Watery fluid that contains various compound • Cradles and cushions brain
Extends from base of brain to first lumbar vertebrae in back Protected by: Cerebrospinal fluid Vertebral column Meninges 3 layers of membranes that cover brain and spinal cord Spinal Cord
Meninges • Dura Mater (outer layer) • Tough, fibrous • Contains channels for blood to enter brain tissue • Arachnoid Mater (middle layer) • Web-like structure • Pia Mater (innermost layer) • Contains blood vessels that nourish spinal cord
Peripheral Nervous System • 12 Cranial Nerves • Carry impulses to and from the brain • 31 pairs of spinal nerves • Carry messages to and from the spinal cord and the torso and extremities of the body
Peripheral Nervous System • 2 Subsystems according to function • Somatic Nervous System • Autonomic Nervous System
Somatic Nervous System • Receive and process sensory input from the skin, muscles, tendons, joints, eyes, tongue, nose and ears • Excite voluntary contraction of skeletal muscles
Autonomic Nervous System • Carry impulses from the central nervous system to glands, various involuntary muscles, cardiac muscle, and membranes • Stimulates organs, glands and senses by stimulating secretions of substances • Divided into sympathetic and parasympathetic divisions
Autonomic Nervous System • Sympathetic • Operates when the body is under stress • Activates responses necessary to react in dangerous or abnormal situations • Fight or Flight response • Parasympathetic • Operates to keep the body in homeostasis under normal conditions