Nervous Tissue

four types of glia cells in the CNS: astrocytes

1. astrocytes most abundant - ends of astrocytes processes cover and wrap around capillaries in the brain - together these form the blood brain barrier -protects brain from toxins such as waste products, drugs, and alcohol in the blood but allows nutrients to pass through - sometimes is detrimental when it prevents the entry of certain antibiotics or chemotherapeutic drugs

dysautonomia

1. autonomic motor component does not function properly. inculdes fainting (syncope), slow or fast heart rate, gastrointestinal issues, thermoregulatory issues, visual blurring, and seizures

neurons

1. basic stuctural unit of nervous system and conduct impulses from one part of the body to another - high metabolic rate and must have a continuous supply of oxygen and nutrients - extreme longevity and often survie from initial development in the womb to old age - after fetal development ability to divide (mitosis) is lost, except possibly in certain areas in the brain

Nerves

1. cable-like bundle of parallel axons -nerves visble to eye

neuron structure

1. cell body serves as the neurons control center an dis responsible for receiving integrating, sending nerve impulses 2. dendrites are cytoplasmic projections branch off cell body and conduct nerve impulses TOWARD the cell body 3. axon is a longer cytoplasmic projection transmits nerve impulses AWAY from cell body -all neurons have only one axon

ependymal cells

1. cells that line the internal cavities (ventricles) of the brain and the central canal of the spinal cord - ependymal cells and nearby blood capillaries together form a netwrok called the choroid plexus - choroid plexus produce cerbrospinal fluid

Structural organization: central and peripheral nervous systems

1. central nervous system (CNS) includes the brain and spinal cord -brain is protected and enclosed within the skull, while the spinal cord is housed and protected within the veterbral canal 2. peripheral nervous system (PNS) includes cranial nerves that arise from the brain, the spinal nerves that arise from spinal cord and ganglia ( clusters of neuron cell bodies located outside the CNS

two types of glial cells in PNS: Satalite cells

1. flattened cells arranged around neuronal cell bodies in ganglia and help regulate the movement of nutrients and waste products between neurons and their environment

oligodendrocytes

1. large cells with slender cytoplasmic processes that ensheathe portions of axons by repeatedly wrapping around an axon like electrical tape wrapped around a wire (myelin sheath)

Development of the nervous system

1. nervous tissue development begins in the embryo during the third week of development 2. neural groove apperars in the developing tissue and by the end of the third week the sids of this groove come together and fuse along the midline to form a neural tube -opening near future head and near future buttocks -if openings do not close human will have a neural tube defect

Cytology of nervous tissue: two distinct cell types from nervous tissue

1. neurons - excitable cells that initiate and transmit nerve impulses 2. glial cells - nonexcitable cells that support and protect the neurons

glial cells

1. occur within the CNS & PNS 2. smaller and capable of mitosis 3. do not transmit impulses, but they do assist neurons by nourishing them, proctecting them, and by providing a supporting framework 4. roughly half the volume of the nervous system

schwann cells

1. or (neurolemmocytes) are responsible for myelinating PNS axons

motor efferent division

1. responsible for transmitting motor impulses from the CNS to muscles or glands 2. efferent means conducting outward or away from the center of activity (transmitted from the CNS) 3. contains both CNS and PNS components

Sensory (afferent) division

1. revieving sensory information from receptors and transmitting this information to the CNS 2. afferent (inflowing) or (towards the center of activity) transmitted to the CNS 3. sensory division contains both PNS and CNS compnents

functional classification of neurons

1. sensory (afferent) neurons transmit nerve impulses from sensory receptors to the CNS -cell bodies of sensory neurons are located outside the CNS and housed in structures called ganglia 2. motor (efferent) neurons transmit nerve impulses from the CNS to muscles or glands 3. interneurons lie entirely within the CNS and facilitate communication between sensory and motor neurons -99% of all our nerurons are interneurons

nerves are a componet of the peripheral nervous system

1. sensory nerves convey sensory information to the central nervous system and all the axons are conducting impulses in the same direction 2. motor nerves convey motor impulses from the central nervous system to the muscles and glands, axons are conducting impulses in the same direction 3. mixed nerves carry both types of information and some axons are transmitting impulses in one direction, while other axons are transmitting impuleses in the opposite direction

motor division two compartments

1. somatic motor compartment conducts nerve impulses from the CNS to the skeletal muscles, causing them to contract. Voluntary 2. autonomic motor component innervates internal organs and regulates smooth muscle, cardiac muscle and glands. Involuntary.

sensory division two components

1. somatic sensory - general somatic senses, touch, pain, pressure, vibration, temperature, and proprioception. These functions are considered voluntary 2. visceral sensory -transmit nerve impulses from blood vessels and viscera to the CNS. primary include temperature and stretch. Said to be involuntary. however you may be aware of visceral sensations

autonomic motor component two groups

1. sympathetic division - speeds up body activites 2. parasympathetic division -slows down body activites

neural tube forms central nervous system

1. the cranial part of the neural tube expands to form the brain 2. caudal part expands to form the spinal cord

Functional organization: sensory and motor nervous systems

1. together CNS, PNS perform several functions 2. collect info with the help of receptors which are specialized nerve endings that detect changes in the internal or external enviroment and pass them on to the CNS as sensory input 3. process and evaluate sensory input so the CNS can determine the respone 4. CNS, after processing and evaluation, then responds by sending nerve impulses via motor neurons in the PNS to effectors (muscles or glands)

microglial

1. wandering phagocytic cells and remove cellular debris throghout the CNS