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