CH. 9: Nervous System

The substance ________________ (ACh) is released at some synapses in the spinal cord and at neuromuscular junctions.

acetylcholine

Nerve impulses are also called what?

action potentials

Norepinephrine, dopamine, and serotonin are called __________, which may play a role in sleep, motor function, mood, and pleasure recognition.

amines

Each axon in a nerve in surrounded by a thin wrapping of fibrous connective tissue called the _________________. Groups of these wrapped axons are called ____________. Each of these are then surrounded by a thin fibrous _______________. A tough, fibrous sheath called the __________________ covers the whole nerve.

endoneurium, fascicles, perineurium, epineurium

Two morphine like neurotransmitters called endorphins and _______________ are released and inhibit pain impulses.

enkephalins

A _______ is a group of peripheral nerve fibers (axons) bundled together like strands of a cable.

nerve

The outer wrapped layer of a schwann cell is called the ________________.

neurilemma (pg. 177)

Reflex arcs allow impulse conduction in only _____ direction(s).

one

The _________ _____________ of a postsynaptic neuron has protein molecules embedded in it that serve as receptors to which neurotransmitter molecules bind. This binding can initiate an _________.

plasma membrane, impulse

The membrane of a resting neuron had a slight __________ charge on the outside and a ___________ charge within. A state called _______________. This occurs because there is normally an excess of sodium ions (______) on outside of the membrane

positive, negative, polarization, Na+

A synapse is the place where impulses are transmitted from one neuron, called the _____________ _________, to another neuron, called the ____________ ________.

presynaptic neuron, postsynaptic neuron

Impulse conduction normally starts in __________. These are the beginnings of dendrites of sensory neurons.

receptors

A basic type of neuron pathway, called a ________ ____, is important to nervous system functioning. The simplest kind is a _____-________ ____ because it contains only two types of neurons: _________ and ________ neurons.

reflex arc, two neuron arc, sensory, motor

The depolarized section of the neuron's membrane immediately recovers, a process called __________________. The impulse/action potential cannot go backward during this recovery, so the impulse continues in one direction across the neuron's surface.

repolarization

Three-neuron arcs consists of three kind of neurons. What are they?

sensory, motor, and interneurons

When a nerve impulse arrives at the synaptic knob, neurotransmitter molecules are released from the vesicles into the __________ ______.

synaptic cleft

A ___________ ______ is a tiny bulge at the end of a terminal branch of a presynaptic neuron's axon. Each contains contains many small sacs or vesicles containing a very small quantity of a chemical compound called a ___________________.

synaptic knob, neurotransmitter

What is the subdivision of the PNS?

the autonomic nervous system (ANS) which consists of structures that regulate the body's automatic/involuntary functions.

Bundles of axons in the CNS called ________, are myelinated and thus form the _______ _________ of the brain and spinal cord. Brain and spinal cord tissue composed of cell bodies of unmyelinated axons and dendrites are called ______ ________.

tracts, white matter, gray matter

A three-neuron arc reaction is called a ______________ ________. Ex: pulling your hand away from a hot/sharp object

withdrawal reflex

The six steps of the knee jerk two-neuron arc are include the stretch receptor, sensory neuron, dorsal root ganglion, synapse, motor neuron, and effector. Explain these in more detail.

1. stretch receptors nerve sense a stimulus and an impulse is generated 2. Impulse travels along length of sensory neuron dendrite 3. Impulse reaches cell body in the dorsal root ganglion located near the spinal cord, then ends at the dendrites of another neuron 4. Nerve impulse stops at this gap (synapse) and chemical signals are sent across 5. A new impulse is triggered and travels through the dendrites, cell body, and axon of the motor neuron (back to site of stimulus). 6. The motor neuron then forms a synapse with an effector to in this case causes a muscle contraction that jerks the knee.

Because there are no __________ cells in the CNS, axons in the brain and spinal cord have no neurilemma, which plays an essential role in the regeneration of cut/injured axons.

Schwann

What are the three types of central glia and what are their functions?

Astrocytes attach neurons to blood vessels and how them close to each other. Their branches also form a two-layer structure called the blood-brain barrier (BBB). Microglia are small and usually remain stationary unless there is disease/inflammation of the brain when they grow and act as phagocytes. Oligodendrocytes (image) help hold nerve fibers together and produce the fatty myelin sheath that envelops nerve fibers in the brain and spinal cord. They wrap around multiple axons.

If a traveling impulse encounters a section of a membrane covered with insulating myelin, what does it do? What kind of impulse travel is this?

It jumps over to get to the next gap. Saltatory conduction

What are the two major type of cells found in nervous tissue and what do they do?

Neurons & Glia. Neurons are nerve cells that conduct impulses and glia (tiny dots) are support cells that support neurons.

What is a myelinated fiber?

Neurons with myelin-wrapped axons

____________________ are chemicals by which neurons communicate

Neurotransmitters

Give an example of a peripheral glia

Schwann cells. They also from myelin sheaths but only in the PNS. Also, these cells wrap entirely around one single axon.

What are the three types of neurons and what do they do?

Sensory, or afferent neurons carry impulses to the spinal cord and brain. Motor, or efferent neurons carry impulses away from brain and spinal cord to muscle or glandular (gland) tissue. Interneurons conduct impulses from sensory to motor neurons, sometimes called central or connecting neurons.

What are the two principal divisions of the nervous system as a whole, and what is contained in each division?

The central nervous system contains the brain and spinal cord and the peripheral nervous system contains the nerves that extend throughout the body.

In a three-neuron arc, what difference does the interneuron make?

The end of the sensory neuron's axon first synapses with an interneuron before chemical signals are sent across a second synapse to the motor neuron.

What is the structure of a neuron and what does each part do?

cell body (main part), branching dendrite projections that receive impulses and carry them to the cell body, and one elongated axon projection which carries impulses away from the cell body.

The syntactic _____ is the space between the synaptic knob and the plasma membrane of a postsynaptic neuron. It is filled with extracellular _________ that holds the synaptic structure in place.

clef, matrix

The myelin sheath affects nerve ______________ _______.

conduction speed

When a section of the neuron's membrane in stimulated , its Na+ channels suddenly open, and Na+ ions rush inward, the inside becoming temporarily positive, and the outside negative, a process called ___________________.

depolarization

What are the nodes of Ranvier?

gaps in the myelin sheath

All interneurons lie entirely within the what of the brain and spinal cord?

gray matter

Nerve __________ do not continually race along every nerve cell's surface. They first must be initiated by a stimulus.

impulses