A&P - Chapter 12. - Nervous Tissue

three functional classes of neurons

Sensory neurons, motor neurons, and interneurons.

universal properties of neurons

1. excitability - response to stimuli

2. conductivity - ability to transmit signals to other cells

3. secretion - secretion of a neurotransmitter from an axon terminals to stimulate the next gap

sensory neurons

• afferent (arriving to CNS)

• specialized to detect stimuli such as light, heat, pressure chemicals to transmit information to the central nervous system (CNS) for processing.

interneurons

• account for 90% of neurons

• receive signals from many other neurons and carry out the integrative functions of the nervous system

• connect the incoming sensory and the outgoing motor pathways

motor neurons

• efferent (exiting the CNS)

• sends signals predominantly to muscle and gland cells

cell body (soma)

control center of the neuron with centrally located nucleus with a large nucleolus

neurofibrils

• apart of neuron’s cytoskeleton

• bundles of actin filaments that help maintain the cell’s shape and extends to the axon and dendrites

axon hillock

• area on the cell body where the axon originates

• referred to as the “trigger zone” due to high concentration of voltage-gated sodium channels

• “decision-making” point for whether an action potential will be generated

neurons

structural and functions units of nervous tissue (highly cellular, little extracellular space)

• amitotic

• excitability, conductivity, secretion

• 3d shape with a body called soma and two types of processes

axon (nerve fiber)

• long, non-branching tail like extensions on neuron (one or none)

• specialized for rapid conduction of nerve signals to points away from the cell body

• CONDUCTIVITY

axon terminal

the end of an axon where neurotransmitters are released

synapse

the junction between neurons where information is transmitted from one neuron to the next

multipolar neurons

• most common type

• neurons with one axon and multiple dendrites

• includes most neurons of the brain and spinal cord

bipolar neurons

neurons with one neuron and one dendrite

ex. certain neurons of the retina

unipolar neurons

neuron with only a single process leading away from the cell body

• found in the sensory ganglia of the spinal and cranial nerves

• pseudounipolar

neuroglia

supporting cells that help neurons complete their function for communication

• 6 types of glial cells

what are the glial cells found in the CNS named?

1. oligodendrocyte

2. microglia

3. ependymal cell

4. astrocyte

what are the glial cells found in the PNS named?

• schwann cells

• satellite cells

oligodendrocytes

forms the myelin sheath in the CNS

myelin sheath

insulating layer made up of protein and lipids that wraps around axons and speeds up signal conduction

ependymal cells

• produce, circulate, and protect cerebrospinal fluid

• lines the cavities of the brain and spinal cord

microglia

small macrophages that phagocytize dead tissue, microorganisms, and other foreign matter in the CNS

• aid in synaptic remodeling (changing the connections between neurons)

astrocytes

• most abundant glial cells

• cover brain surface and nonsynaptic region

• forms supportive framework in the CNS

• forms the blood-brain barrier

• regulates blood flow in the brain tissue to meet changing needs of O2 and nutrients

• promote formation of synapses

schwann cells

• produces myelin sheath to envelopes axons of the PNS

• assist in the regeneration of damaged axons

satellite cells

surround the nerve cell bodies in ganglia of the PNS

• provide insulation around the body

• regulate the chemical environment of the neurons

node of ranvier

gaps between segments of myelin sheath

internodal segments

myelin-covered segments of an axon

what factors make conduction of nerve signals faster?

• large surface areas of axon

• myelination