1/27/26 part 2 - Nervous Tissue part a (cont.)

functional classification of neurons

1. sensory neurons

2. motor commands

3. interneurons

sensory neurons

• have sensory receptors

• rely on receptor dendrites at terminals

• afferent neurons, forming the afferent division of the PNS

• cell bodies are located in the peripheral sensory ganglia, and their processes (afferent fibers) connect sensory receptors and the CNS

• two types: somatic or visceral

ganglion

a collection of neuron cell bodies in the PNS

afferent

flow in

efferent

flow out

sensory receptors

either the terminal ends of specialized sensory neurons or cells connected to sensory neurons

• categorized into 3 groups

interoreceptors

monitor the digestive, respiratory, cardiovascular, urinary, and reproductive systems and provide sensations of digestion (stretch), deep pressure, and pain

exteroreceptors

provide information about the external environment in the form of touch, temperature, or pressure sensations and the more complex senses of taste, smell, sight, and hearing

proprioreceptors

monitor the position and movement of skeletal muscles and joints.

• feel and maintain balance

somatic sensory neuron

monitor the outside world and our position within it

visceral sensory neuron

monitor internal conditions and the status of other organ systems

motor neurons

• efferent neurons, forming the efferent division of the PNS

• two efferent systems: somatic (skeletal muscle) nervous system and the autonomic (visceral) nervous system

• carry instructions from the CNS to peripheral effectors in a peripheral tissue, organ, or organ system

efferent fibers

axons of motor neurons traveling away from the CNS to the peripheral

interneurons

processes the commands, sends to the motor neuron

• aka association neurons, located between sensory and motor neurons.

• most are located within the brain and spinal cord (CNS), some in the autonomic ganglia

• most abundant type of neurons

• integration of information

• distributes sensory information and coordinates motor activity

neuroglia

• also called glia cells

• the type of cells that hold nerve cells in place and help them work properly

• separate and protect neurons, provide a supportive framework for nervous tissue, act as phagocytes, and help regulate the composition of the intersitial fluid

• are abundant and diverse; make up about half the volume of the nervous system

types of neuroglia in the CNS

1. astrocytes

2. ependymal cells

3. oligodendrocytes

4. microglia

types of neuroglia in the PNS

1. satellite cells

2. schwann cells