Anatomy Chapter 13

the nervous system

components of neurons

perikaryon, neurofilaments/neurotubules, neurofibrils, nissl bodies, axon hillocks, axoplasm, collaterals, telodendria, axon terminals, axoplasmic transport

nervous system characteristics

• controls and adjusts the activity of the body

• provides swift but brief responses

two anatomical divisions of the nervous system

central nervous system (CNS) and peripheral nervous system (PNS)

the nervous system consists of _____________________

all the nervous tissue in the body

components of the CNS

the brain and spinal cord

central nervous system (CNS) functions

1) integrating, processing, and coordinating sensory input and motor output

2) acting as the seat of intelligence, memory, learning, and emotion 

CNS receives information from the _______ division and commands with the _______ division

afferent, efferent

cerebrospinal fluid (CSF)

clear, watery fluid that fills the central canal and ventricles, surrounding the CNS

components of the peripheral nervous system (PNS) 

all of the peripheral nerves and nervous tissue outside the CNS

PNS function

provides sensory information to the CNS and carries motor commands away from the CNS

divisions of the PNS

afferent division and efferent division

afferent division of the PNS

carries sensory information to the CNS; begins at receptors that monitor specific characteristics of the environment

the __________ of a receptor carries information to the CNS

stimulation

receptor examples

sensory process, specialized cells or clusters of cells, or complex sense organs 

example of a complex sense organ that acts as a receptor

the eye

efferent division of the PNS

carries motor commands from the CNS to muscles and glands; begins inside the CNS and ends at the effector 

effector 

a peripheral gland or muscle cell innervated by a motor neuron

examples of effectors

muscle cells, gland cells, other cells specialized to perform specific functions

subdivisions of the afferent division of the PNS

somatic and visceral sensory receptors

somatic sensory receptors of the afferent division

monitor skeletal muscles, joints, skin, and from the visceral sensory receptors

visceral sensory receptors of the afferent division

monitor other internal structures, such as smooth muscle, cardiac muscle, glands, and respiratory and digestive organs

special sensory receptors of the afferent division

monitor smell, taste, vision, balance, and hearing

subdivisions of the efferent division of the PNS

somatic and autonomic nervous systems

somatic nervous system (SNS) 

controls skeletal muscle contraction

autonomic nervous system (ANS)

regulates smooth muscle, cardiac muscle, and glandular activity

divisions of the ANS

parasympathetic and sympathetic divisions

activities of the somatic nervous system may be under ____________________ control

voluntary or involuntary

example of voluntary control of the SNS

voluntary contractions of the skeletal muscles

example of involuntary control of the SNS

immediately withdrawing your hand from a hot stove even before noticing the pain

examples of involuntary control of the ANS

heartbeat, digestive processes, and instinctive responses to threatening situations

concept check 13.1: what are the two subdivisions of the nervous system?

the central and peripheral nervous systems

two types of cells contained in the nervous system

neurons and neuroglia

neurons

nerve cells that are responsible for the transfer and processing of information in the nervous system

neuroglia

cells that support and protect neurons

components of neurons

cell body, axon, dendrites, perikaryon, dendritic spines, axon terminals

perikaryon

cytoplasm that surrounds the nucleus in the cell body of a neuron

dendrites

sensory processes of a neuron

dendritic spines

fine processes of dendrites that receive information from other neurons

percent of dendritic spines making up the total surface area of the neuron

80-90%

axon

elongated extension of a neuron that conducts an action potential away from the cell body and toward the synaptic terminals 

axon terminals

site of neuron communication with another cell

approximate ratio of neuroglia to neurons

5:1

are neuroglia smaller or larger than neurons?

smaller

can neuroglia divide?

yes, neuroglia can divide

concept check 13.2: what are the two distinct cell types found within nervous tissue?

neurons and neuroglia

four types of neuroglia in the CNS

astrocytes, oligodendrocytes, microglia, and ependymal cells

two types of neuroglia in the PNS

satellite cells and Schwann cells

function of neuroglia in the CNS

surround CNS neurons and hold them in place, isolate neurons from each other, supply oxygen ad nutrients to neurons, destroy pathogens, and remove dead or damaged neurons

factors that distinguish neuroglia cells from each other

size, intracellular organization, the presence of specific cytoplasmic processes, and staining properties