Nervous Tissue: Introduction, Neurons, and Neuroglia

afferent function

receive and transmit information (sensory input)

integrative function

process information

efferent function

respond to information (motor output)

central nervous system

brain and spinal cord; processes and integrates information

peripheral nervous system

all other parts of the nervous system that branch off of CNS; connects CNS to rest of body

somatic sensory

division of the PNS; consciously perceived from receptors in skin, muscles, bones (think skeletal muscles)

visceral sensory

division of the PNS; unconsciously perceived from receptors in viscera (e.g., heart, stomach, bladder)

motor somatic

division of the PNS; controls skeletal muscles (voluntary) (somatic motor neurons)

motor visceral

aka autonomic nervous system; controls involuntary muscles and glands; sympathetic and parasympathetic systems

sympathetic

fight or flight; motor visceral division of PNS

parasympathetic

rest and digest; motor visceral division of PNS

afferent

towards CNS

efferent

away from CNS

neurons

primary/functional cells of the nervous system; receive, process, respond

neuroglia

supportive cells of the nervous system; aka “glial cells”; provide support to neurons

soma

cell body, aka neurosoma, nucleus, mitochondria, extensive rough ER (produce neurotransmitter peptides), and other organelles

dendrites

receive signals from other neurons, send signals to soma

axon

aka nerve fiber, sends signals to another neuron/muscle/etc., begins at axon hillock, terminals at distal end contain neurotransmitters

sensory neurons

afferent, PNS, send signals from receptors to interneurons in CNS, receptors receive info from external or internal environment

interneurons

integrative, CNS, process and integrate info from afferent neurons

motor neurons

efferent, PNS, send signals to muscles and glands (effectors) to carry out specific actions

neuroglia

support cells, 1 trillion neurons in nervous system vs. 10 trillion of these, 6 types with a variety of roles (4 in CNS and 2 in PNS)

astrocyte, oligodendrocyte, ependymal cell, microglia

CNS glia

satellite cell and schwann cell

PNS glia

astrocytes

most abundant and functionally diverse glial cell in CNS, star-like shape, connect blood vessels and neurons, supportive framework, create BBB, repair damaged nerve cells, regulate tissue fluid composition

oligodendrocytes

CNS glia; extensions wrap around portions of axons, forms myelin sheath

ependymal cells

CNS glia; line fluid-filled cavities, produce CSF, cilia help circulate CSF, look like epithelial cells

microglia

CNS glia; smallest glial cell, mobile, important in immune defense

satellite cells

surround soma of PNS neurons, regulate chemical environment of soma

schwann cells

PNS glia; form myelin sheath around peripheral axons, one cell is completely wrapped around axon in contrast to CNS glia counterpart, aid in regeneration of damaged nerve fibers

myelin sheath

spiral layers of plasma membranes wrapped around nerve fibers, increases conduction speed in axon, improves regeneration of damaged axons, produced by oligodendrocytes in CNS and schwann cells in PNS

myelination

production of myelin sheath

saltatory conduction

occurs in a myelinated axon, AP only happens at Nodes of Ranvier

continuous conduction

occurs in unmyelinated axons, AP happens every step of the way down the axon

PNS

can CNS or PNS nerve fibers regenerate

regeneration

can only occur in a peripheral nerve fiber if neurosoma is intact and some myelin remains