121 terms

Ch. 12 Neural Tissue

2 kinds of cells in Nerve tissue:
neurons, neuroglia
Cells that send and receive signals:
Neurons, also the function unit of nerve cells.
cells that support and protect neurons
2 Divisions of Nervous System:
CNS- brain & spinal cord, used to process and coordinate act. in the body; PNS- all neural tissue outside CNS
Functions of CNS:
Used to process & coordinate activities in the body
Functions of PNS:
Deliver sensory information to the CNS, and gets message back of what to do.
Cranial nerves connect to the:
brain (12 cranial nerves)
Spinal nerves attach to the:
spinal cord (31 spinal nerves)
Functional Divisions of PNS:
afferent, efferent
(TO) Carries sensory information from PNS sensory receptors TO CNS
The primary function(s) of the nervous system include:
providing sensation to the internal & external environments, integrating sensory info, & regulating and controlling peripheral structures & systems
Neurons are responsible for:
information transfer and processing in the nervous system
The region of a neuron with voltage-gated sodium channels is the:
axon hillock
Neurons are classified on the basis of their structure as:
motor, sensory, association
The two major cell populations of neural tissue are:
neurons and neuroglia
CNS glial cell that removes debris, wastes, and pathogens by phagocytosis:
The white matter of the CNS represents a region dominated by the presence of:
Depolarization of the membrane will shift the membrane potential toward:
0 mV
What is the term given to describe a shift in transmembrane potential from -70 mV to -90 mV?
If resting membrane potential is -70 mV and the threshold is -60 mV, a membrane potential of -62 mV will:
not produce an action potential
At the site of an action potential, the membrane contains:
an excess of positive ions inside and an excess of negative ions outside
A node along the axon represents an area where there is
an absence of myelin
Nerve cell bodies in the PNS are clustered together in masses called:
The most important factors that determine the rate of action potential conduction are:
the presence or absence of a myelin sheath and the diameter of the axon
At an electrical synapse, the presynaptic and postsynaptic membranes are locked together at:
gap junctions
Exocytosis and the release of acetylcholine into the synaptic cleft is triggered by:
calcium ions flooding into the axoplasm
Inhibitory or hyperpolarizing CNS neurotransmitters include:
dopamine and serotonin
An excitatory postsynaptic potential (EPSP) is:
a depolarization produced by the arrival of a neurotransmitter
An inhibitory postsynaptic potential (IPSP) is a:
transient hyperpolarization of the postsynaptic membrane
Sensory neurons are responsible for carrying impulses:
to the CNS
Interneurons, or associated neurons, differ from sensory and motor neurons because of their:
exclusive location in the brain and spinal cord
Efferent pathways consist of axons that carry impulses:
away from the CNS
Graded potentials that develop on the postsynaptic membrane in response to a neurotransmitter are:
postsynaptic potentials
The addition of stimuli occurring in rapid succession is:
temporal summation
When sensory information is relayed from one processing center to another in the brain, the pattern is called
serial processing
Interneurons are responsible for:
analysis of sensory inputs and coordination of motor outputs
Sensory (ascending) pathways distribute information
from peripheral receptors to processing centers in the brain
Schwann cells are glial cells responsible for:
producing a complete neurilemma around peripheral axons
When a barrier prevents the movement of opposite charges toward one another, a(n)
potential difference exists
The sodium-potassium pump's activity is needed after:
every action potential to restore resting potential
All-or-nothing principle:
A given stimulus either triggers a typical action potential or does not produce one at all
During the relative refractory period, a larger-than-normal depolarizing stimulus can:
bring the membrane to threshold and initiate a second action potential
Saltatory conduction conducts impulses along an axon
five to seven times faster than continuous conduction
In type C fibers action potentials are conducted at speeds of approximately
2 mph
The larger the diameter of the axon, the
faster the rate of transmission
dipping toe in cold water, pulling back.. The sensory neurons responsible for this is:
The main functional difference between the autonomic nervous system and the somatic nervous system is that the activities of the ANS are
primarily involuntary or under "automatic" control
Reverberation in neural circuits refers to collateral axons that:
use positive feedback to simulate presynaptic neurons
What is happening during a "runners high"?
Endorphins are blocking the transmission of substance P, a neurotransmitter that sends information about pain to the CNS
The most excitatory neurotransmitter in the brain and functions in learning and memory:
What are the two major ions that are involved in generating an action potential?
sodium and potassium. These ions determine the gradient that drives the depolarization of the membrane.
What do we call the difference in charge between the inside of the nerve cell membrane and the outside?
the membrane potential. The difference in charge between the inside and outside of the membrane gives the membrane its responsive nature.
What is the first thing needed to start an action potential?
a stimulus. In order for an action potential to be produced, there has to be a stimulus great enough to start the cascade effect down the axon.
What ion initiates the formation of vesicles filled with acetylcholine?
calcium. As the axon potential arrives at the synaptic terminal, calcium channels open and with calcium influx, the formation of vesicles begins.
When the membrane potential is disturbed, which ion enters the cell?
sodium. When the stimulus causes a disruption in the cell membrane, sodium rushes into the cell.
What do we call the change in the sodium and potassium ions caused by a stimulus?
depolarization. When sodium rushes in, it causes a change in the membrane potential that starts the message down the axon.
When there is no stimulus to the nerve cell, is the cell said to be..
at rest. Homeostasis refers to the body's maintenance of a stable internal environment.
How is potassium recaptured after depolarization?
sodium-potassium pumps. The pumps are responsible for reclaiming the ions so the cell can respond again.
The space between nerve cells is called the
What is the ion responsible for initiating the formation of acetylcholine?
What are the chemicals called that propagate the message across the synapse?
What is the most abundant neurotransmitter in the body
The part of the cell that receives the impulse is called
the dendrite
glial cells that surround cell bodies in the PNS and regulates levels of oxygen and carbon dioxide around ganglionic neurons:
satellite cells
glial cells that can form a myelin sheath around axon fibers in the central nervous system:
The binding of ACh on the axon hillock triggers
the opening of voltage-gated channels.
Synaptic delay is greater at synapses of..
myelinated neurons than at those of unmyelinated neurons.
A chemical synapse at which the neurotransmitter is acetylcholine is called
cholinergic synapse
Receptors of afferent division:
detect changes or respond to stimuli
Effectors of afferent division:
respond to efferent (taking signals away from brain and bringing back to PNS) signals
Somatic nervous system (SNS):
controls skeletal muscle contractions: voluntary and involuntary (reflexes) muscle contractions
Autonomic nervous system (ANS):
controls subconscious actions: contractions of smooth muscle and cardiac muscle and glandular secretions
sympathetic division:
has a stimulating effect (speeds), adrenaline rush
parasympathetic division:
has a relaxing effect (slows), when stuck with needle, get a vegas response due to vegas nerve.
___ perform all of the communication, information processing, and control functions of the nervous system.
multipolar neuron
Common in the CNS:
cell body (soma)
short, branched dendrites
long, single axon (tail)
RER and ribosomes produce..
bundles of neurofilaments that provide support for dendrites and axon
Nissl Bodies:
Dense areas of RER and ribosomes
Make neural tissue appear gray (gray matter, not mylenated; slower)
look like little fingers
Dendritic spines:
many fine processes
receive information from other neurons
80-90% of neuron surface area
The axon
(long tail) Carries electrical signal (action potential) to target, Axon structure is critical to function
Cytoplasm of axon
Contains neurotubules, neurofibrils, enzymes, organelles
Specialized cell membrane
Covers the axoplasm
Axon hillock
where tail attaches to cell body, Thick section of cell body
Attaches to initial segment
Fine extensions of distal axon
Synaptic terminals
Tips of telodendria
(gap in neuron connection)
Area where a neuron communicates with another cell
The synapse steps:
Presynaptic cell, Postsynaptic cell, The synaptic cleft
Presynaptic cell
neuron that sends message
Postsynaptic cell:
cell that receives message
The synaptic cleft:
the small GAP that separates the presynaptic membrane and the postsynaptic membrane
The synaptic knob
Is expanded area of axon of presynaptic neuron, Contains synaptic vesicles of neurotransmitters
are chemical messengers, released at presynaptic membrane, affect receptors of postsynaptic membrane, are broken down by enzymes, are reassembled at synaptic knob
Recycle Neurotransmitters through..
Axoplasmic transport (have to have ATP for it to work)Neurotubules within the axon
Transport raw materials
Between cell body and synaptic knob
Mitochondria is imp. for cell functions with ATP
Neuromuscular junction
Synapse (GAP) between neuron and muscle
Neuroglandular junction
Synapse (GAP) between neuron and gland
Synovial fluid:
reduce friction, Contains slippery proteoglycans secreted by fibroblasts, Functions of synovial fluid lubrication, nutrient distribution, shock absorption
The place where the fixed end attaches to a bone, cartilage, or CT is called..
origin of the muscle.
The site where the movable end attaches to another structure is called..
insertion of the muscle.
The origin is typically proximal to the..
Imaginary part of the pelvis the baby comes through during birth:
pelvic outlet
The four types of muscles identified by different patterns of organization are:
parallel, convergent, pennate, circular
In a convergent muscle the muscle fibers are:
based over a broad area, but all the fibers come together at a common attachment site
Muscles responsible for shrugging shoulders:
Anaxonic neurons:
(ana- without), no tail, Found in brain and sense organs, Small, All cell processes look alike
Bipolar neurons
Found in special sensory organs (sight, smell, hearing); Are small, One dendrite, one axon
Unipolar neurons
cell body is budding off, 2 ends; Found in sensory neurons of PNS, Have very long axons, Fused dendrites and axon, Cell body to one side
Multipolar neurons
Common in the CNS, Include all skeletal muscle motor neurons; Have very long axons, Multiple dendrites, one axon
Three Functional Classifications of Neurons:
sensory, motor, interneurons
Sensory Neurons:
afferent (takes info to CNS) neurons of PNS; Monitor internal environment (visceral sensory neurons), Monitor effects of external environment (somatic sensory neurons
Motor Neurons:
Efferent (brings it back from CNS to PNS) neurons of PNS
assocation neurons
Structures of sensory neurons:
Unipolar, Cell bodies grouped in sensory ganglia, Processes (afferent fibers) extend from sensory receptors to CNS
Three Types of Sensory Receptors:
Interoceptors, Exteroceptors, Proprioceptors
Monitor internal systems (digestive, respiratory, cardiovascular, urinary, reproductive) Internal senses (taste, deep pressure, pain)
(external) External senses (touch, temperature, pressure), Distance senses (sight, smell, hearing)
Monitor position and movement (skeletal muscles and joints) (tells you if ur standing up right, lying down)
Motor Neurons:
Carry instructions from CNS to peripheral effectors via efferent fibers (axons)
Two major efferent systems:
Somatic nervous system (SNS):
includes all somatic motor neurons that innervate skeletal muscles
Autonomic (visceral) nervous system: involuntvary visceral motor neurons innervate all other peripheral effectors, smooth muscle, cardiac muscle, glands, adipose tissue