Chapter 7 Assessment: The Nervous System

Which type of neuroglia supports the metabolic needs of the blood-brain barrier?

Astrocytes -help form the blood brain barrier that acts as a filter to keep damaging substances from entering brain tissue

T or F: After the passage of the action potential, the sodium-potassium pump helps to reestablish the resting membrane potential.

TRUE

T or F: Threshold is the minimum current required for the cell membrane to generate an action potential.

TRUE

What structures are involved in electrical synapses?

gap junctions

Depolarization occurs because __________. multiple q's

more Na+ diffuse into the cell than K+ diffuse out of it sodium ions diffusing into the cell through ligand-gated channels is greater than potassium ions diffuse out of it

Which of the following statements about the resting membrane potential is TRUE?

the exterior of the cell has a net positive charge and the interior has a net negative charge

Which of the following is/are a location of nicotinic ACh receptors?

-autonomic ganglia -specific regions of the brain -skeletal muscle all of them

If you could modify an axon so that it transmits impulses faster than before, which of the following modifications should you make?

-decrease the diameter of the axon -increases the diameter of the axon -increase the myelination of the axon -decrease the body temperature in the body within its homeostatic range -increase the temperature in the body within its homeostatic range -increase the amount of voltage gated channels within the Schwann cells

Which of the following describes the role of astrocytes in the formation and function of the blood-brain barrier?

-induce tight junctions between capillary endothelial cells -produce carrier proteins and ion channels -produce enzymes to destroy toxic substances

Which of the following is/are a characteristic of GABA as a neurotransmitter?

-it is inhibitory -it opens Cl- channels into the cell -it helps control voluntary movement ALL of them

Characteristics of Myelinated axons

-myelinated axons transmit nerve impulses via continuous conduction -myelinated nerve impulses in the same manner as unmyelinated axons -myelinated axons utilize fewer voltage-gated channels than unmyelinated axons of the same length and diameter -myelinated axons are more energy efficient than unmyelinated axons -myelinated axons would be unaffected by diseases that attack the CNS

If astrocytes were damaged or lost, how would this impact CNS function?

-the composition of cerebral spinal fluid would be very similar to blood plasma

Characteristics of Oligodendrocytes

-they are a type of neuroglia found in the PNS -they would be affected a demyelinating disease of the PNS -they surround multiple axons in the CNS at the same time -they contribute to the white matter of the brain

Presynaptic neuron: Postsynaptic neuron:

Action potentials conducted by axon Terminal Boutons: 1. opens voltage-gated Ca2+ channels 2. release of excitatory neurotransmitter Dendrites and Cell Bodies: 3. opens chemically ligand- gated channels 4. inward diffusion of Na+ causes depolarization 5. localized decremental conduction of EPSP Axon Initial Segment: 6. opens voltage-gated Na+ and then K+ channels Axon: 7. conduction of action potential

Hyperpolarization that leads to postsynaptic inhibition is a/an ________.

IPSP

What type of cells produce the myelin sheath in the central nervous system (CNS)?

Oligodendrocytes

T or F: If the postsynaptic membrane potential reaches threshold level, an action potential will be produced.

TRUE

T or F: Once threshold is reached on the postsynaptic membrane, an action potential is generated and propagated over the postsynaptic cell membrane.

TRUE

T or F: The sodium-potassium ATPase pump is involved in establishing the resting membrane potential.

TRUE

T or F: The area between the presynaptic nerve cell and the postsynaptic muscle cell is termed the synaptic cleft.

TRUE

A recently depolarized area of a cell membrane cannot generate an action potential because of the ______________.

absolute refactory period

A neuron that has just propagated an action potential is quickly stimulated again with an even greater EPSP, but no response occurs. This neuron must have been in the __________when the second stimulus arrived.

absolute refractory period

The neurotransmitter at the neuromuscular junction is ___________.

acetylcholine

Acetylcholine diffuses across the synaptic cleft and ________.

bind to ACh receptors that open ligand-gated sodium channels

What structure(s) are present exclusively within the myelin sheath of the PNS?

both neurilemma and sheath of Schwann cell are correct

The arrival of the action potential at the presynaptic terminal causes ________.

calcium to enter the presynaptic terminal through voltage-gated calcium channels

What is the function of acetylcholinesterase?

catalyzes hydrolysis of ACh to remove it from the synaptic cleft.

An action potential __________.

causes the inside of the neuron cell membrane to become positively charged in reference to the outside.

An action potential generates local currents that tend to __________ the membrane immediately adjacent to the action potential.

depolarize

At the neuromuscular junction, acetylcholine __________.

diffuses across the synaptic cleft and bonds to acetylcholine receptors on the postsynaptic muscle fibers

The muscarinic ACh receptors are formed from only a single subunit and do not contain _________________ like the __________ ACh receptors. Rather, binding of ACh to the muscarinic receptor activates a complex of proteins in the cell membrane known as _____________, because their activity is influenced by GDP and GTP, guanosine nucleotides. There are three G-protein subunits: alpha, beta and gamma. Binding of ACh causes the ___________ subunit to dissociate from the other two, which form the _______________ complex. Either the alpha subunit or the ______________________ complex then diffuses through the membrane until it binds to an ion channel and causes it to open or close.

ion channels nicotinic G-proteins alpha beta, gamma beta, gamma

What is the effect of the neurotransmitter at the neuromuscular junction?

it causes ligand gated sodium channels in the muscle fibers to increase their permeability to sodium, which depolarizes the postsynaptic membrane

What is the purpose of acetylcholinesterase on the postsynaptic membrane ________.

it is an enyzyme that breaks down ACh into acetic acid and choline

Acetylcholine has which effect on the postsynaptic neuron?

ligand gated sodium ion channels open and sodium diffuses inward

An adult male has difficulty moving his hand after a head injury that resulted in damage to neurons in his brain. The damage is likely permanent because __________.

neurons on the CNS lack Schwann cells, which play a major role in axon regeneration

Replarization occurs because __________.

potassium ions continue to diffuse out of the cell after the inactivation gates of the voltage-gated sodium ion channels begin to close

The increase in calcium ion concentration causes ________.

release of acetylcholine from the synaptic vesicles into the synaptic cleft

The convergence of many presynaptic terminals onto one postsynaptic neuron is called ________.

spatial summation

Which of the following occurs when an action potential arrives at the presynaptic terminal?

synaptic vessels fuse with the plasma membrane and release acetylcholine

Successive EPSPs from a presynaptic terminal to a postsynaptic neuron is called ________.

temporal summation

When threshold is reached in a neuron, depolarization occurs with the same amplitude of potential change. This is known as ________.

the All-or-None principle

Hyperpolarization, or after potential occurs because __________.

the increased potassium ion permeability lasts slightly longer than the time required to bring the membrane potential back to its resting level

Match neurotransmitter with its action: 1. Painkillers 2. Appetite Stimulant 3. Inhibits NT release; may aid memory and learning 4. Blood vessel dilation, relax other smooth muscles 5. promotes odor adaption 6. dilation of cerebral blood vessels

1. Endogenous opioids 2. Neuropeptide Y 3. Endocannabinoids 4. Nitric oxide 5. carbon monoxide 6. ATP

Events in order regarding production, release and inactivation of monoamine transmitters

1. Monoamine produced and stored in synaptic vesicles 2. Action potentials open gated Ca2+ channels, leading to release of neurotransmitter 3. Neurotransmitters enter synaptic cleft 4. Reuptake of most neurotransmitter from synaptic cleft 5. Inactivation of most neurotransmitter by MAO

Number the events of neurotransmitter release from the synaptic terminal in the correct order.

1. action potential reaches axon terminal 2. voltage-gated Ca2+ channels open 3. extracellular Ca2+ enters terminal and binds to sensor protein (protagamin) in the cytoplasm 4. Ca2+ protein complex stimulates fusion of the docked synaptic vesicle with the plasma membrane 5. Exocytosis of neurotransmitter into synaptic cleft

T or F: EPSPs and IPSPs cannot act upon a postsynaptic neuron at the same time, according to the all-or-none principle.

FALSE

T or F: Receptors that bind the neurotransmitter on the postsynaptic cell membrane are voltage-gated.

FALSE

T or F: The sodium-potassium pump uses bulk transport to move the sodium and potassium ions.

FALSE

T or F All neurotransmitters are made from amino acids

FALSE Many neurotransmitters are found in other systems of the body, particularly the digestive system and may have other types of regulatory functions when not released by neurons.

T or F: IPSPs cause hyperpolarization of a postsynaptic membrane. One way to accomplish this task would be to either open sodium channels or potassium channels.

FALSE Opening of sodium channels would lead to depolarization of a postsynaptic membrane, or an EPSP. Opening of potassium channels would cause an IPSP to occur, as potassium is more concentrated inside the cell, and would flow outward.

T or F: Action potentials travel faster on thin, myelinated axons than on thick, myelinated axons.

FALSE axons travel faster on thick myelinated axons

The binding of ACh to the muscarinic receptor indirectly affects the permeability of _____ channels. This can produce ___________________ in some organs if channels are opened, and ________________ in others if channels are closed. For example, in the heart it is the beta-gamma complex that binds to the K+ channels of heart muscle and causes them to open. This leads to K+ diffusion _____ of the cell and the cell becomes ___________________ resulting in a decrease in heart rate. In contrast, in smooth muscle of the stomach the alpha subunit binds to K+ channels causing them to close. This reduces the outward diffusion of K+ and the cell becomes _________________ resulting in smooth muscle contraction.

K+ hyperpolarization depolarization out hyperpolarized depolarized

When a neurotransmitter binds to a nicotinic receptor, the ion channel opens and ________.

Na+ diffuses into and K+ diffuses out of the cell simultaneously

During depolarization, which of the following statements about voltage-gated ion channels is TRUE?

Na+ gates open before K+ gates

The absolute refractory period causes action potential propagation to ___________.

occur in one direction

An action potential arriving at the presynaptic terminal causes __________.

voltage-gated calcium ion channels to open, and calcium ions to diffuse into the cell