Nervous System 1 - Lecture 11

1. Maintaining homeostasis. 2. Receiving sensory input. 3. Integrating information. 4. Controlling muscles and glands. 5. Establishing and maintaining mental activity.

Functions of the Nervous System

Special Senses: Conscious Stimuli - Vision (Sight) Audition (Hearing) Equilibrium (Balance) Olfaction (Smell) Gustation (Taste) General Senses: Touch Pressure Pain Temperature Unconscious Stimuli* Blood pH, gases, and pressure.

Sensation are categorized into general and special senses.

Some Spinal Nerves, like thoracic spinal nerves will not join a nerve plexus, but will innervate structures of the viscera.

Spinal Nerve, Nerve Plexus, and Peripheral Nerve

Neurons 1. Sensory (Afferent) Neurons 2. Motor (Efferent) Neurons 3. Interneurons Neuroglial Cells (Glial Cells) CNS: 1. Astrocytes 2. Ependymal Cells 3. Microglia 4. Oligodendrocytes PNS: 5. Schwann Cells 6. Satellite Cells

Cells of the Nervous System

Motor (Efferent) Division 1. The motor division transmits action potentials from the CNS to effector organs like muscles and glands. 2. The cell bodies of the lower motor neurons are located within the spinal cord within the ventral horn. 3. Lower Motor Neurons are multipolar neurons.

Divisions of the Peripheral Nervous System Motor (Efferent) Division

3. Cardiac muscle and some smooth muscle (wall of the stomach) contract autorhythmically, that is, no external stimulation is necessary for each contraction event. 4. Many glands, including sweat glands, salivary glands, and glands of the digestive system. Establishing and maintaining mental activity The brain is the center of mental activities, including consciousness, thinking, memory, and emotions.

Controlling Effector Organs (Muscles and Glands) 1. Skeletal muscles normally contract only when stimulated by the nervous system; Thus the nervous system controls the major movements of the body by controlling skeletal muscle. 2. Some smooth muscle, such as that in the walls of blood vessels, contracts only when stimulated by the nervous system or hormones.

Nerve: A bundle of axons and their sheath that connects CNS to the sensory receptors, muscles, and glands. Cranial Nerves: Nerves that originate from the brain or brainstem. There are 12 cranial nerve pairs (CN I-XII). Spinal Nerves: Nerves that originate from the spinal cord. There are 31 spinal nerve pairs: 8 Cervical 12 Thoracic 5 Lumbar 5 Sacral 1 Coccygeal Ganglion (Ganglia):A collection of neuronal cell bodies outside of the CNS. Nuclei:A collection of neuronal cell bodies within the CNS. Plexus: Extensive network of axons, and sometimes neuron cell bodies, located outside of the CNS. Synapse: A junction of a nerve cell with another cell. If there is a synapse formed with a muscle fiber, it is referred to as a neuromuscular Junction. Effector Organs: Muscles (Skeletal, Smooth, or Cardiac) and Glands.

Divisions of Peripheral Nervous System (PNS): 1. Consists of all the nervous tissue, like nerves and ganglia, outside the CNS. 2. It links the CNS with the various parts of the body. 3. It carries information about the different tissues of the body to the CNS and carries commands from the CNS that alter body activities.

Sympathetic Nervous System: "Fight or Flight" Prepares the body for physical activity. Parasympathetic: "Rest and Digest" Regulates the resting or vegetative functions such as digesting food or emptying of the urinary bladder. Enteric Nervous System Nerve Plexuses within the wall of the digestive tract. Enteric neurons monitor and control the digestive tract independently of the CNS through local reflexes. However, the CNS can override enteric functions via parasympathetic and sympathetic actions

Divisions of the Autonomic Nervous System The ANS controls your unconscious activities, such as contractions of smooth muscle, cardiac muscle, and secretion by certain glands.

2. Autonomic Nervous System (ANS): Involuntary - Action potentials originate from CNS to regulate smooth muscle, cardiac muscle, and certain glands. - Two Neuron System with the effector organ: 1st Motor Neuron (Preganglionic Neuron) conveys action potentials from CNS to a ganglion. 2nd Motor Neuron (Postganglionic Neuron) conveys action potentials from ganglion to effector organ

Divisions of the Motor (Efferent) Division 1. Somatic Nervous System (SNS): Voluntary and Involuntary (in reflexes) - Action potentials originate from CNS to regulate skeletal muscles (voluntary control). - One neuron system with the effector organ.

PNS = Peripheral Nervous System ANS = Autonomic Nervous System CNS = Central Nervous System Para = Parasympathetic Nervous System SNS = Somatic Nervous System Sym = Sympathetic Nervous System ENS = Enteric Nervous System (Intestines only)

Divisions of the Nervous System

Sensory (Afferent) Division 1. The sensory division transmits electrical signals (action potentials) from sensory receptors in the body to the CNS. 2. The cell bodies of sensory neurons are located near the spinal cord in ganglia called dorsal root ganglia. 3. Primary Sensory Neurons (or First Order Neurons) are pseudo-unipolar (unipolar) neurons.

Divisions of the Peripheral Nervous System Sensory (Afferent) Division

Central Nervous System 1. Brain (Cerebrum and Cerebellum) 2. Brainstem 3. Spinal Cord Peripheral Nervous System 1. Cranial Nerves (from Brain or Brainstem) - Transmit information to and from the head and neck. Number of pairs of cranial nerves ________. 1. Spinal Nerves (from the spinal cord) - Transmit information to and from the body. Number of pairs of spinal nerves ________. 2. Peripheral Nerves Spinal nerves will enter a plexus (nerve network) contributes to several spinal nerves. Each peripheral nerve contains fibers derived from several spinal nerves. - Transmit information to and from the body.

General Divisions of the Nervous System General Divisions of the Nervous System 1. Central Nervous System 2. Peripheral Nervous System

The input may: 1. Be stored as memory and integrated. 2. Produce an immediate response (reflex). 3. Be ignored (adaptation).

Integrating information The brain and spinal cord are the major organs for processing sensory input and initiating responses.

Events 1. An increase in blood pressure is detected by a baroreceptor through CN IX. 2. This signal is relayed and integrated by the Medulla oblongata. 3. Through CN X, the heart inhibits the pacemaker and thus reduces its cardiac output. 4. Blood pressure is reduced.

Maintaining Homeostasis The nervous system can stimulate or inhibit activities to help maintain homeostasis. Example: Blood Pressure

3 Parts of a Neuron 1. Cell body (Soma) 2. Dendrite 3. Axons (Nerve Fiber) Cell Body (Soma) 1. Contains a single, relatively large, centrally located nucleus. 2. Extensive endoplasmic reticulum (ER) and the Golgi Apparatus for the synthesis and transport of neurotransmitters. 3. Nissl Bodies - Neuronal cell bodies also contain free ribosomes and prominent clusters of rough ER, called Nissl Bodies. These ribosomes are the sites of protein synthesis. Newly synthesized proteins produced by Nissl Bodies are used to replace cellular components, as material for growth of neurons, and regenerated damaged axons in the PNS.

Neurons (or Nerve Cells) 1. Electrically excitable cells of the nervous system. 2. They receive stimuli and transmit action potentials to other neurons or to effector organs. 3. They are organized to form complex networks that perform the functions of the nervous system

Sensory receptors: Endings of the neurons, or separate, specialized cells that detect stimuli (temperature, pain, touch , pressure, light, sound, order, and other stimuli).

Receiving Sensory Input Sensory receptors monitor numerous external and internal stimuli.

Examples of Types: 1. Grapheme-color Synesthesia: Individual letters of the alphabet and numbers are "shaded" or "tinged" with color. 2. Chromesthesia: Association of sounds with color. 3. Auditory-Tactile Synesthesia: Sounds induce sensation in parts of the body.

Synesthesia Note: Although we study each senses as separate units, please keep in mind that senses aren't entirely exclusive in their interpretation and sometimes we have sensory crossing and mixing. In extreme cases, there are conditions of Synesthesia, which is the production of a sense impression relating to one sense or part of the body by stimulation of another sense or part of the body.