Biol 22: chqplter 7

Three different types of neurons

- Pseudounipolar neurons, which are sensory, have one process that splits. - Bipolar neurons, found in the retina and cochlea, have two processes. -Multipolar neurons, which are motor neurons and interneurons, have many dendrites and one axon

Place the events of the action potential in order chronologically.

- threshold is reached - Na+ channels are fully open and Na+ enter the call - Na+ channels inactivated - K+ channels fully open and K+ leave the cell - K+ channels inactivated

There are two types of neuroglia in the peripheral nervous system:

1. Schwann cells, which form myelin sheaths around peripheral axons; and 2. satellite cells, which support neuron cell bodies within the ganglia of the PNS.

There are four types of neuroglia in the central nervous system

1. oligodendrocytes, which form myelin sheaths around axons of the CNS; 2. microglia, which migrate through the CNS and phagocytose foreign and degenerated material; 3. astrocytes, which help to regulate the external environment of neurons in the CNS; and 4. ependymal cells, which are epithelial cells that line the ventricles (cavities) of the brain and the central canal of the spinal cord.

myelin sheath

A layer of fatty tissue segmentally encasing the fibers of many neurons; enables vastly greater transmission speed of neural impulses as the impulse hops from one node to the next.

What is dopamine?

A monoamine neurotransmitter.

Serotonin

A neurotransmitter that affects hunger,sleep, arousal, and mood.

A propagated change in the membrane potential of a neuron due to the opening and closing of voltage gated channels is called a(n)

Action potential

Function of Schwann Cells (PNS)

Also called neurolemmocytes, produce the myelin sheaths around the myelinated axons of the peripheral nervous system; surround all PNS axons (myelinated and nonmyelinated) to form a neurilemmal sheath

Which of the following are functional classifications of neurons?

Autonomic motor neurons Efferent neurons Sensory neurons

The highly selective barrier to diffusion that the specialized capillaries of the brain create is known as

Blood- brain barrier

What type of neuron is found entirely in the CNS?

Both interneuron and association neuron are correct.

The blood-brain barrier is a feature of the

Brain capillaries

What are the three main parts of a neuron? What are their functions?

Cell body: is known as the soma, as it represents the center of the nerve cell that carries genetic information, and contains the nucleus, and some specialized organelles, as well as maintaining the structure of the nerve cell, and providing it with the energy needed to carry out various activities. Axon: each neuron contains one axon, and the axon is characterized by being long, tail-like, and attached to the cell body in a specialized cross section called the axon hillock, and it is worth noting that many axons are surrounded by a fatty substance It's called myelin, which conducts electrical signals. Dendrites: They are branches of the cell body, working to receive electrical signals from the axons of other neurons. Neurons contain groups of tree appendages known as dendritic trees. As for their number, this varies according to their function; For example, Purkinje cells - a type of neuron found in the cerebellum - contain a group of well-developed dendrites that allow thousands of nerve signals to be received.

Endogenous opioids

Chemicals produced by the body that reduce pain, enhance positive mood, and suppress appetite.

Hyperpolarization of the postsynaptic membrane in response to glycine or GABA is produced by the opening of

Cl- channels

What is the convergence of neural pathways?

Convergence occurs when a number of axons synapse on a single neuron

Function of Astrocytes(CNS)

Cover capillaries of the CNS and induce the blood-brain barrier; interact metabolically with neurons and modify the extracellular environment of neurons

Function of Oligodendrocytes ( CNS)

Form myelin sheaths around central axons, producing "white matter" of the CNS

function of ependymal cells (CNS)

Form the epithelial lining of brain cavities (ventricles) and the central canal of the spinal cord; cover tufts of capillaries to form choroid plexuses—structures that produce cerebrospinal fluid

Cells that are electrically coupled and joined together share

Gap junctions

Nodes of Ranvier

Gaps in the myelin sheath to which voltage-gated sodium channels are confined.

Which of the following amino acids acts as the major excitatory neurotransmitter in the central nervous system?

Glutamic acid

Tract

Grouping of axons that interconnect regions of the CNS

Ganglion

Grouping of neuron cell bodies located outside the CNS

Nucleus

Grouping of neuron cell bodies within the CNS

Postsynaptic inhibition is produced by depolarization of the postsynaptic membrane. hyperpolarization of the postsynaptic membrane. axoaxonic synapses. long-term potentiation.

Hyperolarization of the postsynaptic membrane

When sodium enters an axon, the inside of the axon becomes

Less negative

What gaseous neurotransmitter is produced from L-arginine by nitric oxide synthetase?

NO

Which of these is not a characteristic of action potentials? They are produced by voltage-regulated gates. They are conducted without decrement. Na+ and K+ gates open at the same time. The membrane potential reverses polarity during depolarization.

Na+ and K+ gates open at the same time.

Peripheral nervous system (PNS)

Nerves, ganglia, and nerve plexuses (outside of the CNS)

Saltatory conduction proceeds between

Node of ravier

Function of Microglia (CNS)

Phagocytose pathogens and cellular debris in the CNS

—————— receptors designated P1 for ATP binding and P2 for adenosine binding are found in neurons and glial cells.

Purinergic

———— neurotransmitters, such as endocannabinoids, are released from a postsynaptic neuron (sometimes from the dendrites of that neuron) and diffuse back to effect the presynaptic neuron.

Retrograde

The myelin sheaths of PNS neurons are produced by

Schwann cells

The supporting cells that form myelin sheaths in the peripheral nervous system are

Schwann cells

Which of these neurons are pseudounipolar? Sensory neurons Somatic motor neurons Neurons in the retina Autonomic motor neurons

Sensory neurons

Autonomic neurons can subdivided into:

Sympathetic- fight or flight responses (body under stress) Parasympathetic- rest and digest (body is relaxed)

The terminal boutons of the presynaptic neuron are separated from the dendrites of the postsynaptic neuron by a space called the

Synaptic cleft

Axonal transport

The transportation of materials from the neuronal cell body to distant regions in the dendrites and axons, and from the axon terminals back to the cell body.

Which of these is not a characteristic of synaptic potentials? They are all-or-none in amplitude. They decrease in amplitude with distance. They are produced in dendrites and cell bodies. They are graded in amplitude. They are produced by chemically regulated gates.

They are all-or-none in amplitude.

Why was the saline drained from the nerve chamber before the nerve was stimulated?

To prevent the current from passing through the saline rather than between the nerve and electrodes.

Choose the statement that correctly describes the structure or function of dendrites

Transmit graded electrochemical impulses toward the cell body

Norepinephrine is

a catecholamine used in sympathetic regulation of smooth and cardiac muscle. a neurotransmitter in the CNS that regulates mood and behavior.a catecholamine used in sympathetic regulation of smooth and cardiac muscle.

What enzyme is responsible for the inactivation of acetylcholine at the synaptic cleft?

acetylcholinesterase

neurilemma

additional external myelin sheath that is formed by Schwann cells and found only on axons in the peripheral nervous system

An action potential begins as

an increase in charge sufficient to achieve threshold

Endogenous opioids:

are released in response to exposure to a stressor block the transmission of pain

The myelin sheaths of CNS neurons are produced by

b. oligodendrocytes

Nitric oxide (NO):

causes the release of secondary messengers in the PNS and CNS acts as a smooth muscle relaxant acts as a neurotransmitter

Neuroglia

cells that support and protect neurons

What is a neuron classified as if it uses acetylcholine as its neurotransmitter?

cholinergic

Neurons in the central nervous system that use acetylcholine as a neurotransmitter can be classified as

cholinergic neurons

Myelin Sheath in PNS

concentric layers of schwann cell plasma membrane around axon

Central nervous system (CNS)

consists of the brain and spinal cord

Conduction of action potentials in a myelinated axon is

continues without decrement called saltatory conduction is faster than in an unmyelinated axon

What is another name for an EPSP (excitatory postsynaptic potential) that is generated at the neuromuscular junction?

end plate potential

At the neuromuscular junction, the excitatory postsynaptic potential produced by acetylcholine in skeletal muscle fibers are also called

end-plate potentials.

Which type of cell lines the ventricles of the brain and help produce cerebrospinal fluid?

ependymal cells

A collection of neuron cell bodies located outside the CNS is called

ganglion

Degeneration of spinal motor neurons in adults may be due to a lack of ____________ factor.

glial-derived neurotrophic (GDNF)

A drug that inactivates acetylcholinesterase

increases the ability of ACh to stimulate muscle contraction

Depolarization of an axon is produced by

inward diffusion of Na+

Norepinephrine

is a catecholamine is a monoamine is a neurotransmitter

Postsynaptic inhibition:

is caused by IPSPs or inhibitory postsynaptic potentials occurs when neurotransmitters like GABA hyperpolarize the neuron

Acetylcholine (ACh):

is inhibitory is a neurotransmitter is excitatory

A synapse is _

junction between a sending neuron and a receiving neuron

Which type of cell of the CNS is phagocytic?

microglia

Regulatory molecules derived from amino acids are called

monoamines

Retrograde transport

movement of materials from synaptic knobs to cell body

Which are structural classifications of neurons?

multipolar, unipolar, bipolar

Axonal regeneration in the CNS is inhibited by

myelin-associated inhibitors

The term "white matter" refers to

neural tissue especially of the brain and spinal cord that consists largely of myelinated nerve fibers bundled into tracts

Sensory/afferent neurons

neurons that carry incoming information from the sensory receptors to the brain and spinal cord

Motor/efferent neurons

neurons that carry outgoing information from the brain and spinal cord to the muscles and glands

Saltatory conduction proceeds between

nodes of Ranvier

The myelin sheaths of CNS neurons are produced by

oligodendrocytes

The smallest response recorded, with a stimulus around 0.3 volts, was produced because

only a few axons were brought to threshold, so only these few axons produced an action potential

Changes in the permeability of the membrane are due to:

opening and closing of ion channels

Repolarization of an axon during an action potential is produced by

outward diffusion of K+

Which of the following may be attributed to the effects of endogenous opioids?

pain relief exercise euphoria

After the initial increase in membrane potential to a positive voltage, the membrane potential returns to resting levels because

potassium moves out of the cell

function of satellite cells (PNS)

protect neuron cell bodies

Monoamines

regulatory molecules derived from amino acids. Dopamine, norepinephrine (noradrenalin), and epinephrine (adrenalin) are derived from the amino acid tyrosine and placed in a subfamily of monoamines called catecholamines.

The conduction of action potentials in a myelinated nerve fiber is

saltatory, without decrement, and faster than in an unmyelinated fiber

Cells supporting neuron cell bodies in ganglia are termed

satellite cells

During an action potential, the inside of the cell Initially goes from negative to positive. This membrane depolarization, in which the inside of the cell becomes positive, is produced by:

sodium moving into the cell

2 types of motor neurons:

somatic : responsible for reflexes and the voluntary control of skeletal muscles and autonomic: axons are sent to involuntary effectors such as smooth muscle, cardiac muscle, and glands

During this experiment, action potentials were produced in the frog sciatic nerve by electrical stimuli that

stimulated the electrodes placed on the nerve

What is the functional connection between a neuron and an effector cell called?

synapse

When a presynaptic neuron is experimentally stimulated at a high frequency, the excitability of the synapse is enhanced over time. This change represents the concept of:

synaptic plasticity

As the strength of a depolarizing stimulus to an axon is increased,

the frequency with which action potentials are produced increases

saltatory conduction

the jumping of action potentials from node to node

The measurements are called compound action potentials because

the measured response correlates to how many axons are being stimulated

Myelin Sheaths in the CNS

the myelin sheaths of the CNS are formed by oligodendrocytes

During the action potential, voltage-gated channels open so that:

the sodium channels are fully open before the potassium channels

Acetylcholine (ACh)

used as an excitatory neurotransmitter by some neurons in the CNS and by somatic motor neurons at the neuromuscular junction. At autonomic nerve endings, ACh may be either excitatory or inhibitory, depending on the organ involved.