Chapter 7 HW - Nerves
Place the events in the correct order on the figure.
1. ACh binds to receptor 2. G-protein subunit dissociates 3. G-protein binds to K+ causing it to open
Match the 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 adaptation 6. Dilation of cerebral blood vessels
1. Endogenous opioids 2. Neuropeptide Y 3. Endocannabinoids 4. Nitirc oxide 5. Carbon monoxide 6. ATP
Place the events in the correct order regarding the production, release, and inactivation of monoamine neurotransmitters, beginning with the production of monoamine.
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
Which type of neuroglia supports the metabolic needs of the blood-brain barrier?
Astrocytes
Which of the following is/are a location of nicotinic ACh receptors?
Autonomic ganglia Specific regions of the brain Skeletal muscle
What structure(s) are present exclusively within the myelin sheath of the PNS?
Both neurilemma and sheath of Schwann are correct
Drag each label to the dock indicating the direction indicated at resting membrane potential (RMP).
Extracellular fluid: sodium leaks towards, ATPase pumps move K+ towards, during RMP the Na+ gradient is towards the Intracellular fluid: potassium leaks towards, ATPase pumps move sodium towards, during RMP the potassium gradient is towards the
What structures are involved in electrical synapses?
Gap junctions
Hyperpolarization that leads to postsynaptic inhibition is a/an ________.
IPSP
Check all that apply. If you could modify an axon so that it transmits impulses faster than before, which of the following modifications should you make?
Increase the diameter of the axon Increase the myelination of the axon Increase the temperature in the body
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
What is the function of acetylcholinesterase?
It catalyzes hydrolysis of ACh to remove it from the synaptic cleft.
How does glycine act to control skeletal movements?
It inhibits the antagonist's action by causing IPSPs.
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 skeletal muscle movements
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
Check all that apply as characteristics of myelinated 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.
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
What type of cells produce the myelin sheath in the central nervous system (CNS)?
Oligodendrocytes
Drag each label to the type of paralysis that would occur from each of the conditions.
Prevents muscle relaxation: tetanus (inhibition of vesicle movement in the synaptic terminal), botulinim (blocks inhibitory synapses), nerve gas (AChE inhibitor) Prevents muscle contraction: myasthenia gravis (blocks ACh receptors), saxitoxin (block voltage-gated sodium channels), tetrodotoxin (prevents action potential generation_
Which of the following occurs when an action potential arrives at the presynaptic terminal?
Synaptic vessels migrate to the plasma membrane and release acetylcholine.
Check all that apply. 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. Toxic substances could easily build up in the brain.
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.
Check all that apply as characteristics of oligodendrocytes.
They can surround multiple axons in the CNS at the same time. They contribute to the "white matter" of the brain.
A neuron that has just propagated an action potential is quickly stimulated again, but no response occurs. This neuron must have been in the __________when the second stimulus arrived.
absolute refractory period
A recently depolarized area of a cell membrane cannot generate an action potential because of the ______________.
absolute refractory period
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
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
Acetylcholine has which effect on the postsynaptic neuron?
ligand-gated sodium ion channels open and sodium diffuses inward
The suppression of neurotransmitter release from presynaptic terminals by retrograde release of endocannabinoids is called ________.
long-term depression
Depolarization occurs because __________.
more Na+ diffuses into the cell than K+ diffuses out of it
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 in the CNS lack Schwann cells, which play a major role in axon regeneration
Dopaminergic neurons of the mesolimbic dopamine system originate in the midbrain and terminate in the ________.
nucleus accumbens
The absolute refractory period causes action potential propagation to ___________.
occur in one direction
Repolarization 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
Degeneration of dopaminergic neurons of the nigrostriatal dopamine system may cause __________.
severe motor problems
The convergence of many presynaptic terminals onto one postsynaptic neuron is called ________.
spatial summation
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
Assume all of the presynaptic synapses identified produce EPSPs. If two of these synapses fired simultaneously, which synaptic combination brings the initial segment closest to threshold based on spatial summation? Click on the appropriate synapses.
the two closest to the axon hillock
An action potential arriving at the presynaptic terminal causes __________.
voltage-gated calcium ion channels to open, and calcium ions to diffuse into the cell
