Nervous System & Nervous Tissue

Introduction to the Nervous System & Nervous Tissue

• The nervous system receives sensory information
• The nervous system processes information in the brain
• The nervous system sends out motor commands to make responses
• The central nervous system (CNS) is the body's processing center
• The peripheral nervous system (PNS) relays information from the central nervous system
• Motor components control movement by sending signals
• Sensory components receive information from body receptors
• Somatic motor division involves voluntary skeletal muscle movements
• Autonomic motor division involves involuntary functions such as heart rate
• Major neuron components: Dendrites, Soma, Neuroglia, Axon
• Dendrites receive signals
• Axon outputs signals
• Unipolar neurons have a single branch, found in afferent, and are involve in sensory reception
• Bipolar neurons have two branches, found in sensory organs (eye and nose), sends sensory information to CNS
• Multipolar neurons have one axon with multiple branches, mainly in Brain and spinal cord CNS, for motor control and sensory processing
• The nervous system includes: sensory receptors, afferent pathways, a control center, efferent pathways, and effector organs

Neuroglial Cells and Membrane Potentials

• Depolarization decreases the membrane potential
• Repolarization returns the membrane potential to resting
• Hyperpolarization increases the membrane potential
• Threshold is a critical level needed to activate an action potential

CNS and Cerebrum

• Cerebrospinal fluid (CSF) cushions from injury and provide nutrients
• Gyrus: Ridge on the surface of the brain
• Sulcus: Shallow groove on cerebral cortex
• Fissure: A larger or deeper sulcus
• Four major parts of the adult brain: Cerebrum, Cerebellum, Brainstem, Diencephalon
• Ventricular system components include two lateral ventricles, one third ventricle, one fourth ventricle connected by a passageway filled with CSF
• The blood-brain barrier (BBB) separates the brain from the bloodstream and shields the brain from toxic substances
• Major landmarks of the cerebrum include the left and right hemisphere, the four lobes, corpus callosum
• Three major cerebral regions: Cerebrum, Cerebellum, Brainstem
• Spinal nerve plexus described as a network of interweaving nerve fibers that arise from multiple spinal nerves

Reflexes

• Reflex is described as an automatic response to a stimulus

Senses

• Lens focuses light rays onto the retina to help us see clearly
• Extrinsic eye muscles action is to control eye movement
• Accessory eye structures include: Eyelids, conjunctiva, and Lacrimal (tear) glands
• Rods enable low light vision (black and white perception)
• Cones enable color vision and sharp detail
• Taste buds located on the tongue
• Taste buds appear as little bumps that are called papillae
• Primary taste sensations include: Sweet (sugar, pleasurable), sour (acid), salty (sodium ions), bitter (harsh), unami (savory). (tasted by tongue)
• Sound travels from the auditory canal to the eardrum causing vibration, Vibrations amplified by auditory ossicles
• Process of an action potential at the spiral organ causes hair cells to bend opening the ion channels which leads to depolarization and releases neurotransmitters
• Receptor cells for equilibrium are classified as Mechanoreceptors
• Static items are at rest with zero net force
• Dynamic items moving with constant velocity