The Nervous System

Functions of the Nervous System Respond to internal and external stimuli Transmit nerve impulses to and away from CNS Interpret nerve impulses at the cerebral cortex Assimilate experiences in memory and learning Initiate glandular secretions and muscle contraction Program instinctual behavior

Divided into…  Central Nervous System (CNS)  Peripheral Nervous System (PNS)

Central Nervous System (CNS) Composed of: Brain Spinal Cord

Peripheral Nervous System (PNS) Composed of: Cranial Nerves (from the brain) Spinal Nerves (from the spinal cord) Ganglia (clusters of cell bodies of neurons) Plexuses (networks of nerves)

Autonomic Nervous System (ANS) Functional division of nervous system Structures in the brain are the control centers of the ANS Nerves are the pathways for conduction of these nerve impulses Functions to automatically speed up or slow down body activities

Neurons Nerve cells found in both CNS and PNS

Parts of a neuron Cell Body Similar to other types of cells Contains a nucleus Dendrites Extensions that project from the cell body Short and branching Receive signals from other neurons Transmit impulses to the cell body Axon Covered in a myelin sheath (like insulation on a wire) Myelin is produced by Schwann cells Transmit impulses away from the cell body

Types of Neurons Sensory Neurons: transmit impulses to the CNS Somatic sensory: carry impulses from receptors in the skin, bones, muscles, and joints Visceral sensory: carry impulses from the visceral organs Motor Neurons: transmit impulses away from the CNS Association neurons (interneurons): conduct impulses from sensory to motor neurons

CNS: The Brain Five Regions Brain RegionStructures TelencephalonCerebrum DiencephalonThalamus, Hypothalamus, Pituitary Gland MesencephalonSuperior & Inferior colliculus, Cerebral peduncles MetencephalonCerebellum and Pons MyelencephalonMedulla oblongata

Cerebrum (Telencephalon) Two hemispheres Connected by the corpus collosum Five lobes Frontal, Parietal, Temporal, Occipital, Insular Responsible for higher functions Perception of sensory impulses, instigation of voluntary movement, memory, thought, and reasoning Cortex (outer surface) has elevated fields (gyri/gyrus) and grooves (sulci/sulcus)

5 Lobes Frontal Lobe: voluntary control of skeletal muscles; personality; intellectual process; verbal communication Parietal Lobe: cutaneous and muscular sensations; understanding and utterance of speech Temporal Lobe: interpretation of auditory sensations; auditory and visual memory Occipital Lobe: integration of movements in focusing the eye; correlation of visual images with previous experiences; conscious seeing Insular: memory; integration of other cerebral activities

Diencephalon Thalamus: a relay center for all sensory impulses to the cerebral cortex, except for smell Hypothalamus: cardiovascular regulation, body temperature regulation, water and electrolyte balance, gastrointestinal activity and hunger, sleeping and wakefulness, sexual response, emotions, and control of endocrine functions through stimulation of the anterior pituitary Pituitary Gland: has endocrine functions

Mesencephalon (Midbrain) Short section of the brain stem Contains: Superior colliculi (visual reflexes) Inferior colliculi (auditory reflexes) Cerebral peduncles (coordinates reflexes)

Metencephalon Pons Relays impulses from one region of the brain to another Many cranial nerves originate here Involved with regulating respiratory rate Cerebellum Consists of two hemispheres Involuntary coordination of skeletal-muscle contractions within muscles, tendons, joints, and sensory organs

Mylencephalon Medulla oblongata Connects to spinal cord Makes up much of the brain stem Controls autonomic functions (heart rate, contraction of blood vessels, rate and depth of breathing)

CNS: The Spinal Cord Extends through the vertebral canal of the vertebral column Conducts nerve impulses to and from the brain

PNS: Cranial Nerves Innervate structures of the head, neck, and trunk Identified by Roman numerals in order of appearance from front to back 12 cranial nerves

PNS: Spinal Nerves 31 pairs 8 cervical 12 thoracic 5 lumbar 5 sacral 1 cocccygeal After exiting the vertebral column, they split, combine, and split again forming a plexus (there are 4) Cervical plexus Brachial plexus Lumbar plexus Sacral plexus