sensory information to the CNS and carries motor commands from the cns to the peripheral tissues and systems
PNS is divided into what two divisions?
afferent-carries sensory info to CNS
efferent-carries motor commands to muscles and glands
visceral sensory receptors
monitor other internal tissues such as smooth muscle, cardiac muscle and glands
what two types of neural tissue are there?
Neurons(impulse conduction) and neuroglia(supporting cells, can divide unlike neurons, common source of tumors)
general characteristics of neuroglial cells
smaller than neurons
more numerous than neurons
most found in brain and spinal cord
source of tumors
controlling interstitial environment
maintaining the blood-brain barrier
performing repairs in damaged neural tissue
guiding neuron development
smallest of glial cells, work as phagocytic cells in the CNS engulfing cellular debris, waste products and pathogens
regulate exchange of nutrients and waste products between the neuron cell body and the extracellular fluid
every peripheral axon whether unmyelinated or myelinated is coverd with Schwann cells; Supporting cells of the peripheral nervous system responsible for the formation of myelin.
thick outermost coil of myelin sheath- bulging of Scwann cell contains nucleus and cytoplasm
specifically what cells help maintain the blood-brain barrier?
astrocytes help maintain the blood-brain barrier
what is the name of the membranous coating formed around axons by oligodendrocytes?
myelin is what oligodendrocytes produce
identify the cells in the peripheral nervous system that form a covering around axons
in the PNS, schwann cells form a myelin covering around axons
small neurons; cannot distinguish axons from dendrites; only found in CNS; functions are poorly understood
One dendrite and one axon; Receive limited inputs (special sense organs), rare, axons are not myelenated
located in the periphery of the pody, where it conveys sensory impulses; characterized by a single process that divides into two, and a cell body located in a sensory ganglia
have multiple dendrites and a single axon; most common type of neuron in CNS; all motor neurons that control skeletal muscles are this type
pseudounipolar neurons with their cell bodies located outside the CNS in peripheral sensory ganglia; form the afferent division of the PNS-deliver info to the CNS
visceral sensory neurons
transmit info about internal conditions and the status of other organ systems
Changes that occur in the axon distal to the site of axonal damage; the axon swells up and becomes irregular; eventually, the axon and the terminals are broken down into fragments that are phagocytosed by adjacent macrophages and Schwann cells.
an electrical impulse developed after the threshhold level has been reached, the membrane permeability to sodium and potassium ions changes