Chapter 12. Nervous system: Nervous tissue
________________ of our neurons are interneurons
99%
The synapse is located __________ the presynaptic neuron and postsynaptic neuron
Between
The nervous system is composed of the ________________, spinal cord, nerves, and ganglia
Brain
Which of the following segments of a neuron contain large numbers of voltage-gated potassium channels and voltage-gated sodium channels?
Conductive segment Initial segment
The somatic sensory division detects stimuli that are ____________ detected
Consciously
_____________ occurs in an unmyelinated axon
Continuous conduction
Which terms are used for the structural classification of nerves
Cranial and spinal
Events of synaptic transmission from earliest to latest
1. Action potential reaches synaptic knob 2. Voltage-gated calcium channels open 3. Calcium enters the synaptic knob 4. Calcium triggers exocytosis of vesicles 5. Neurotransmitter diffuses across synaptic cleft 6. Neurotransmitter binds to postsynaptic receptors
Events of an EPSP in order
Excitatory neurotransmitter binds to chemically gated cation channel More Na+ enters the postsynaptic cell than K+ leaves The inside of the cell becomes more positive The local current of Na+ becomes weaker as it moves towards the axon hillock
A myelinated axon has a ___________ conduction velocity than a unmyelinated axon
Faster
Which of the following ions have leak channels on the plasma membrane
K+, Na+
____________ cells wander through the CNS and replicate in response to an infection
Microglial
Which of the following is used for fast axons transpoet
Microtubules, motor proteins & ATP
________________ nerves contain both sensory and motor neurons
Mixed
The _________ consists of all axons that transmit a nerve impulse from the CNS to a muscle or glad
Motor nervous system
__________ neurons are most common
Multipolar
Which of the following pumps can you find in the plasma membrane?
Na+, K+, Ca2+
In the ___________ there are a lot of ion channels and very little myelin
Neurofibril node
The period following an action potential in which an action can be initiated with a larger stimulus is known as the _________ ________ period
Relative refractory
A nerve impulse that "jumps" from node to node is called __________ conduction
Saltatory
__________ help regulate fluid composition including the exchange of nutrients and waste in the nervous system
Satellite cells
The somatic _____________ division of the nervous system receives information from the eyes, ears and skin
Sensory
______________ are found in mixed nerves
Sensory and motor axons
Extracellular
Sodium
An action potential cannot be initiated during the absolute refractory period because _____________
Sodium channels are inactivated, and thus can not open
Which are two divisions of the sensory nervous system
Somatic and visceral division
Receptors detects changes in the external or internal environment. These changes are called
Stimuli
The junction between an axon and another cell is called a _______________
Synapse
A flow of electrical current called a(n) __________ ____________ is generated within the initial segment of a neuron
action potential
A substance synthesized at the cell body must undergo _____ transport to reach the synaptic knobs.
anterograde
What must happen in order for a chemical signal to change the membrane potential of a neuron
There must be a change in ion flow across the membrane. There must be a change in the number of open ion channels
Vesicles involved in retrograde transport are moving ___________ the cell body
Toward
True or false: In saltatory conduction, Na+ only flows across the axon membrane at the neurofibril nodes
True
True or false: the flow of potassium ions through leak channels makes the membrane potential more negative
True
True or false: the nervous system serves as the body's primary communication and control system
True
______________ neurons have a single, short neuron process that emerges from the cell body and branches like a T
Unipolar
______________ is what underlies the absolute refractory period
Inactivation of sodium channels
Chloride-based IPSP from earliest to latest
Inhibitory neurotransmitter binds to postsynaptic chemically gated chloride channels Chloride moves from outside the cell to the inside The inside of the postsynaptic cell becomes more negative The local chloride current becomes weaker as it moves away from the neurotransmitter binding site
The "I" in IPSP stands for ____________, meaning that the potential makes the inside of the postsynaptic cell more _____________
Inhibitory, negative
The sensory division of the nervous system is responsible for ___________
Input
______________ are also called association neurons
Interneurons
____________ there would be no net movement of K+ ions through an open K+ leak channel
When the electrical gradient and chemical gradient balance each other
The plasma membrane of an axon is called the ___________
axolemma
A fascicle is a bundle of ____________
axons
A soma is another name for the _______
cell body
The brain and spinal cord are part of the _________
central nervous system
The ependymal cells help produce __________
cerebrospinal fluid
Synapses are classified as
chemical synapses and electrical synapses
The peripheral nervous system is made of the spinal nerves, ganglia, and __________ nerves
cranial
_____________ nerves extend from the brain, while __________ nerves extend from the spinal cord
cranial and spinal
Motor neurons are classified as ___________ neurons
efferent
The electrochemical gradient is formed from a combination of the __________ gradient and the __________ gradient
electrical and chemical
An individual axon is wrapped in a connective tissue covering called the __________
endoneurium
An entire nerve is surrounded by a connective tissue covering called the _________
epineurium
Neurons are classified _________ depending on the direction the nerve impulse travels
functionally
Neuron cell bodies in the peripheral nervous system are found clustered in ___________
ganglia
A ___________ ________ is a temporary change in membrane potential which lasts only as long as the stimulus that causes it and can vary in size
graded potential
Glial cells are found ___________
in both the central and peripheral nervous system
The autonomic nervous system is _________________
involuntary
The myelin sheath is made of a high percentage of ____________
lipids
Nervous tissue is composed of glial cells and ______
neurons
____________ are large cells that ensheath many different axons
oligodendrocytes
The motor nervous system is responsible for ____________
output
During the _________ ________ an axon is either incapable of generating an action potential, or requires a larger than normal stimulus
refractory period
Which of the following are considered types of effectors
skeletal muscle, glands, cardiac muscle
Neurons integrate multiple synaptic inputs by the process of ___________Awww
summation
Which of the following are true of neurolemmocytes?
they create the myelin sheath in the PNS, they are also called Schwann cells
Dendrites transfer information ___________ the cell body
toward
A unipolar neuron has one extension. A bipolar neuron has __________ extensions
two
Sensory information from the visceral sensory division is ____________ sensed
unconsciously
most afferent neurons are classified functionally as __________
unipolar
Slow axonal transport results from the flow of ______________
Axoplasm
The term __________ means "to bring to"
Afferent
Sensory _________ neurons carry information ________ the central nervous system
Afferent/toward
The nerve impulse causes __________ in the number of calcium ions that enter the synaptic knob
An increase
Substances can be moved in fast axonal transport (in)
Anterograde and retrograde directions
The functions of astrocytes are to _____________
Assist neuronal development Help form the blood brain barrier Regulate the composition of interstitial fluid Form structural support Occupy the space of dying neurons
_______________ correctly describes the role of K+ leak on the resting membrane potential
At potassium flows out of a cell the inside of the cell becomes more negative
The flow of sodium ions through sodium channels is best describes as ____________
From outside the cell to inside
A(n) ____________ results in a swelling, or enlarged portion, along the length of the nerve, which is often large enough to be observed with the naked eye
Ganglion
___________ occurs when the inside of a cell becomes more negative than the resting membrane potential
Hyperpolarization
A toxin which interferes with the activity of neurons is called a ____________
Neurotoxin
______________ are chemicals released from synaptic knobs and bind to receptors on postsynaptic membranes
Neurotransmitter
Which of the following would be likely to cause depolarization of a neuron
Opening of a chemically gated sodium channel, opening of a voltage gated sodium channel
Intracellular
Organic ions
A nerve is part of the ____________ nervous system
Peripheral
Neurolemmocytes create the myelin sheath in the __________ nervous system
Peripheral
When sodium ions flow into a cell through a leak channel they make the membrane potential more
Positive
The sequential opening of voltage-gates sodium channels is followed by the sequential opening of voltage-gated ____________ channels
Potassium
A ___________ transmits an impulse through its axon toward the synapse
Presynaptic neuron
The neurons in the retina of the eye are _____________
bipolar