Nervous System
3 Functions of the Nervous System (SIM) 1. Sensory input—gathering information monitor changes inside and outside the body changes = stimuli sensory receptors responsible for input 2. Integration decide if and what action is needed 3. Motor Output a response activates muscles or glands (effectors)
Functions of the Nervous System Figure 7.1
Organization and Structural Classification of the Nervous System 2 Main Divisions Central nervous system (CNS) Brain Spinal cord 2. Peripheral nervous system (PNS) Spinal nerves (to and from spinal cord) Cranial nerves (to and from brain)
Organization of the Nervous System
Functional Classification of the Peripheral Nervous System Sensory (afferent) division carry information to the central nervous system Keep the body informed of internal and external environment Motor (efferent) division carry impulses away from the central nervous system Cause some sort of effect
Functional Classification of Neurons Interneurons (association neurons) Found in neural pathways in the central nervous system Connect sensory and motor neurons Receptors Specialized dendritic endings Simple: cutaneous receptors (pain, touch) Complex: special sense organs (eye, nose)
Functional Classification of the Peripheral Nervous System Two Subdivisions of the Motor (Efferent) Division Somatic nervous system = voluntary Skeletal muscles (except reflexes) Autonomic nervous system = involuntary smooth muscle, cardiac muscle, glands
Functional Classification of the Peripheral Nervous System Two subdivisions of the Autonomic nervous system 1. Sympathetic Concerned with processes involving expending energy. Active during times of extreme stress, emotion, and exercise. Parasympathetic Concerned with conservation of energy Can dominate sympathetic system.
Nervous Tissue: 2 Main Types of Cells 1. Neurons carry messages (impulses) 2. Supporting cells or neuroglia
Nervous Tissue Neurons: specialized to transmit messages -structures may differ, but all neurons have: PARTS: 1. Cell body contains transparent nucleus large conspicuous nucleolus metabolic center of the cell
Nervous Tissue: Neurons Figure 7.4
Nervous Tissue Neurons 2 Types of Processes fibers that extend from the cell body Dendrites—conduct impulses toward the cell body Axons—conduct impulses away from the cell body
Myelin: whitish, fatty material that covers nerve fibers to speed up nerve impulses Schwann cells: surround axons and form myelin sheath Myelin sheath: tight coil of wrapped membranes Nodes of Ranvier: gaps between Schwann cells
Axon Terminals- axon ends contain vesicles with neurotransmitters do not touch dendrite of next neuron OR muscle Synaptic cleft—gap between adjacent neurons Synapse—junction between nerves
Neurons Figure 7.4 Site of protein synthesis Provides support and shape Figure 7.4
Figure 7.6
6 Types of Support Cells 1. Astrocytes (CNS) star-shaped cells Most abundant of the glial cells Mainly function between neurons and capillaries Bridging the two Communication between the two Barrier between the two Control the chemical environment of the brain (taking in extra K+ or neurotransmitters)
Nervous Tissue: Support Cells 2. Microglia (CNS) Spiderlike phagocytes (phago- eat) Dispose of debris (dead brain cells and bacteria)
Nervous Tissue: Support Cells 3. Ependymal cells (CNS) Line cavities of the brain and spinal cord Ciliated cuboidal epithelial cells Circulate cerebrospinal fluid Help in production of cerebrospinal fluid
Nervous Tissue: Support Cells 4. Oligodendrocytes (CNS) Wrap around nerve fibers in the central nervous system Produce myelin sheaths in CNS 5. Schwann cells (PNS) Form myelin sheath in the PNS
Nervous Tissue: Support Cells 6. Satellite cells (PNS) Protect neuron cell bodies by providing cushion
Regions of a Typical Neuron
Vocabulary Tract- bundles of nerve fibers running through the CNS. Nerves-bundles of nerve fibers running through the PNS White matter- Consists of dense collections of myelinated fibers Gray matter- Consists of mostly unmyelinated fibers and cell bodies