Nervous System and Nervous Tissue

Chapter 12: Nervous System and Nervous Tissue

• The major anatomical divisions of the nervous system are the central nervous system (CNS), comprising the brain and spinal cord, and the peripheral nervous system (PNS), consisting of all nervous tissue outside the CNS.
• The functional divisions of the nervous system include the sensory (afferent) division, which transmits impulses from receptors to the CNS, and the motor (efferent) division, which transmits impulses from the CNS to effector organs (muscles and glands).
• Gray matter consists of neuron cell bodies, dendrites, and unmyelinated axons; functionally, it is involved in processing and integration of information.
• White matter consists of myelinated axons; it is primarily involved in transmitting nerve impulses over long distances.
• The parts of a multipolar neuron, in order of polarity, are the dendrites, cell body (soma), axon hillock, axon, and axon terminals.
• Types of glial cells in the CNS include astrocytes (support, regulate ions and neurotransmitters), oligodendrocytes (myelination), microglia (immune defense), and ependymal cells (line cavities, produce CSF).
• The main types of glial cells in the PNS include Schwann cells (myelination) and satellite cells (support and regulate neuron environment).
• The major functions of the nervous system encompass sensation (detecting internal and external stimuli), integration (processing and interpreting sensory input), and response (activating effectors to produce a reaction).
• The resting membrane potential is established by the distribution of ions (Na+, K+, Cl-) across the cell membrane, the selective permeability of the membrane to these ions, and the action of the Na+/K+ pump.
• During an action potential, the membrane undergoes depolarization (due to Na+ influx) and repolarization (due to K+ efflux).
• Graded potentials vary in magnitude and can be either depolarizing or hyperpolarizing, while action potentials are all-or-none events.
• Neurotransmitters can be categorized by chemical type (e.g., acetylcholine, amino acids, biogenic amines, neuropeptides) and by their effect (excitatory or inhibitory).

Chapter 13: Anatomy of the Nervous System

• The embryonic nervous system develops from the neural tube, which forms the CNS structures (brain and spinal cord).
• Major regions of the adult nervous system include the cerebrum, diencephalon (thalamus, hypothalamus, epithalamus), brainstem (midbrain, pons, medulla oblongata), cerebellum, and spinal cord.
• Regions of the cerebral cortex can be located based on anatomical landmarks such as the central sulcus (separates frontal and parietal lobes), lateral sulcus (separates temporal lobe), and longitudinal fissure (separates cerebral hemispheres).
• The spinal cord in cross-section has regions including the anterior (ventral) median fissure, posterior (dorsal) median sulcus, gray matter (anterior, posterior, and lateral horns), and white matter (anterior, posterior, and lateral columns).
• The cranial nerves, in order of anatomical location, are: olfactory (I), optic (II), oculomotor (III), trochlear (IV), trigeminal (V), abducens (VI), facial (VII), vestibulocochlear (VIII), glossopharyngeal (IX), vagus (X), accessory (XI), and hypoglossal (XII).
• Spinal nerves are listed by vertebral regions: cervical (C1-C8), thoracic (T1-T12), lumbar (L1-L5), sacral (S1-S5), and coccygeal (Co1).
• The cervical plexus supplies nerves to the neck, shoulder, and diaphragm.
• The brachial plexus supplies nerves to the upper limb.
• The lumbar plexus supplies nerves to the anterior and medial thigh.
• The sacral plexus supplies nerves to the posterior thigh, leg, and foot.

Chapter 14: The Somatic Nervous System

• The somatic nervous system comprises sensory receptors, sensory neurons, and motor neurons that control skeletal muscles.
• General senses include touch, temperature, pain, and pressure, distributed throughout the body.
• Special senses include vision, hearing, taste, and smell, located in specific organs.
• Regions of the central nervous system that contribute to somatic functions are the cerebral cortex (motor and sensory areas), basal ganglia (motor control), cerebellum (coordination), and spinal cord (reflexes).
• The stimulus-response motor pathway involves sensory receptors detecting a stimulus, sensory neurons transmitting information to the CNS, the CNS integrating the information, and motor neurons transmitting commands to skeletal muscles for a response.

Chapter 15: The Autonomic Nervous System

• The autonomic nervous system (ANS) components include visceral sensory neurons, integrating centers in the CNS, and autonomic motor neurons that innervate smooth muscle, cardiac muscle, and glands.
• The sympathetic division (fight or flight) has short preganglionic fibers and long postganglionic fibers, with ganglia located close to the spinal cord.
• The parasympathetic division (rest and digest) has long preganglionic fibers and short postganglionic fibers, with ganglia located near or within the effector organs.
• Visceral reflexes include a sensory receptor, afferent neuron, integrating center, efferent neurons (preganglionic and postganglionic), and an effector (smooth muscle, cardiac muscle, or gland).
• Target effector responses to autonomic input depend on the signaling molecule released; norepinephrine (sympathetic) can be excitatory or inhibitory via adrenergic receptors, while acetylcholine (parasympathetic) is typically excitatory via muscarinic receptors.
• The central nervous system coordinates and contributes to autonomic functions through the hypothalamus (major control center), brainstem (reflex centers), and cerebral cortex (emotional influences).