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What type of response does the nervous system provide to stimulli?
swift but brief
What type of response does the endocrine system provide to stimuli?
adjusts metabolic operations and directs long-term changes
What are the organs of the nervous system?
brain, spinal cord, sensory receptors, nerves
What do receptors do?
detect changes or respond to stimuli
What do effectors do?
respond to efferent signals
What comprises the central nervous system?
brain and spinal cord
What comprises the peripheral nervous system?
all neural tissue outside the CNS; nerves, sensory receptors
What are the functions of the CNS?
process and coordinate; analyze data, motor commands, higher functions of the brain
What are the higher functions of the brain?
intelligence, memory, learning, emotion
What are the functions of the nerves of the PNS?
delivery sensory information to CNS, carry motor commands to peripheral tissues and systems
What are the functions of the receptors of the PNS?
detect changes or respond to stimuli
What are the functional divisions of the PNS?
afferent and efferent
What does the afferent division of the PNS do?
carries sensory information to CNS
What does the efferent division of the PNS do?
carries motor commands from CNS to PNS to muscles and glands
What are the two parts of the efferent division of the PNS?
somatic nervous system and autonomic nervous system
What does the somatic nervous system do?
controls skeletal muscle contractions
What does the autonomic nervous system do?
controls subconscious actions, contractions of smooth and cardiac muscle, and glandular secretions
What are the divisions of the ANS?
sympathetic and parasympathetic
What are the two cell types of neural tissue?
neuron and neuroglia or glial cells
What are neurons?
the basic functional unit of the nervous system
What are neuroglia or glial cells?
supporting cells of the nervous system
Classification of anaxonic neurons
no anatomic clues to distinguish dendrites from axons
Classification of bipolar neurons
two distinct processes: one dendritic process and one axon with the cell body between them
Classification of unipolar neurons
fused dendrites and axon, cell body to one side
Classification of multipolar neurons
multiple dendrites, one axon
What are the three functional classifications of neurons?
sensory neurons, motor neurons, interneurons
Are sensory neurons afferent or efferent?
afferent
Are motor neurons afferent or efferent?
efferent
What do sensory neurons do?
carry information to the CNS
What is a ganglion?
collection of neuron cell bodies in the PNS
What do somatic sensory neurons do?
monitor external environment
What do visceral sensory neurons do?
monitor internal environment
What are the types of sensory receptors?
interoceptors, exteroceptors, proprioceptors
What do exteroceptors do?
sense external environment
What do proprioceptors do?
sense the position and movement of skeletal muscles and joints
What do interoceptors do?
monitor internal organ activity and sense taste, deep pressure, and pain
What do motor neurons do?
carry instructions from CNS to peripheral effectors
What do somatic motor neurons do?
innervate skeletal muscles
What do visceral motor neurons do?
innervate all PNS effectors other than skeletal muscles
What are interneurons responsible for?
analyzing sensory information and coordinating motor outputs; also involved in memory, planning, and learning in humans
What portion of the volume of the nervous system in made up of neuroglia?
half the volume
What are the four types of neuroglia in the CNS?
ependymal cells, microglia, astrocytes, oligodendrocytes
Where are ependymal cells found?
lining the central canal of the spinal cord and ventricles of the brain
What do ependymal cells do?
secrete cerebrospinal fluid (CSF)
What do microglia do?
they are the "wandering police force"
Where are astrocytes found?
lining CNS capillaries
What do astrocytes do?
maintain blood brain barrier
What does the blood brain barrier do?
separates the capillaries in the brain from the nervous tissue
What is the purpose of the blood brain barrier?
prevents many drugs, proteins, ions, and other molecules from readily passing from the blood into the brain
What do oligodendrocytes do?
myelinate axons in the CNS
What makes up white matter of CNS?
regions dominated by myelinated axons
What makes up gray matter of CNS?
cell bodies and unmyelinated fibers
What are the types of neuroglia in the PNS?
satellite cells and Schwann cells
What do neurons do?
perform all communication, information processing, and control functions of the nervous system
What do neuroglia do?
preserve physical and biochemical structure of neural tissue and are essential to survival and function of neurons
What are the five main membrane processes in neural activities?
resting potential, graded potential, action potential, synaptic activity, information processing
What is the general resting membrane potential?
-70mV
What is RMP determined by?
membrane permeability to K+ and Na+
What is equilibrium potential?
the transmembrane potential at which there is no net movement of a particular ion across the cell membrane
What causes a rise or fall in transmembrane potential?
temporary changes in membrane permeability
What happens as a result of change in transmembrane potential?
opening or closing of specific membrane channels
True or false: passive channels are always open
true
What causes active channels to open or close?
specific stimuli
What are the three states of an active channel?
closed but capable of opening, 2. open (activated), 3. closed and incapable of opening (inactivated)
What are the three classes of gated channels?
chemically regulated, voltage regulated, mechanically regulated
What opens chemically regulated channels?
the presence of specific chemicals at a binding site
Where are chemically regulated channels found?
on neuron cell body and dendrites
What opens voltage regulated channels?
specific changes in transmembrane potential
Where are voltage regulated channels found?
neural axons, skeletal muscle sarcolemma, cardiac muscle
What opens mechanically regulated channels?
membrane distortion
Where are mechanically regulated channels found?
sensory receptors (touch, pressure, vibration)
What are graded potentials?
Short-lived, localized changes in membrane potential
What happens during excitation of graded potential?
A stimulus triggers the opening of Na+ channels and membrane potential moves toward zero (depolarization)
What happens during inhibition of graded potential?
A stimulus triggers opening of K+ channels and membrane potential increases (hyperpolarization)
What happens during repolarization of graded potential?
RMP is restored to normal by channels and ion pumps
What is an action potential?
the change in electrical potential associated with the passage of an impulse along the membrane of a muscle cell or nerve cell.
What initiates an action potential?
a stimulus that reaches threshold (-60 to -55mV)
What is the first step in the generation of action potentials?
Depolarization to threshold
What is the second step in the generation of action potentials?
activation of voltage regulated Na+ channels --> depolarization
What is the third step in the generation of action potentials?
inactivation of Na+ channels, activation of K+ channels --> repolarization
What is the fourth step in the generation of action potentials?
return to normal permeability
What are the types of refractory periods?
absolute and relative
What is the absolute refractory period?
brief period during which a local area of a neuron's membrane resists re-stimulation, will not respond to any stimulus
What is the relative refractory period?
time during which the membrane is repolarized and restoring the resting membrane potential, will only respond to a very strong stimulus
What is the propagation of an action potential?
the movement of an action potential generated in axon hillock along entire length of axon
What are the two methods of propagating action potential?
continuous and saltatory
Where does continuous propagation occur?
unmyelinated axons
Where does saltatory propagation occur?
myelinated axons
What is the speed of continuous propagation?
slow: 1m/s
What is the speed of saltatory propagation?
rapid
What occurs during continuous propagation?
local current depolarizes the next segment; cycle repeats
What occurs during saltatory propagation?
action potential appears to leap from node to node, skipping the intervening membrane surface
How does information travel within the nervous system?
as propagated electrical signals (action potentials)
What is the most important information within the nervous system carried by?
large diameter myelinated axons
What is a synapse?
area where a neuron communicates with another cell
What does a presynaptic cell do?
sends signal
What does a postsynaptic cell do?
receives signal
What are the two types of synapses?
electrical and chemical
True or false: cells are in direct contact for a chemical synapse
false
What are neurotransmitters?
chemical messengers that cross the synaptic gaps between neurons
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