Chapter 7 (Part 2) - The Nervous System

Number the events of neurotransmitter release from the synaptic terminal in the correct order. - exocytosis of neurotransmitter into synaptic cleft - extracellular Ca2+ enters terminal and binds to sensor protein in the cytoplasm - action potential reaches axon terminal - Ca2+ protein complex stimulates fusion of the docked synaptic vesicle with the plasma membrane - voltage-gated Ca2+ channels open

1. Action potential reaches axon terminal 2. voltage-gated Ca2+ channels open 3. extracellular Ca2+ enters terminal and binds to sensor protein 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

Saxitoxin is a neurotoxin sometimes produced by shellfish. Saxitoxin prevents Na+ gated channels from opening. Which of the following would produce the same signs as saxitoxin poisoning?

A chemical that inhibited the formation of ACh in the synaptic knob

Sandra had ptosis (droopy eyelid) which most likely resulted from the Botox. Which of the following is a mechanism that would cause this sign of botulinum toxin exposure?

A chemical that prevents the release of ACh from the presynaptic neuron

Which of the following is/are a characteristic of GABA as a neurotransmitter? It opens Cl- channels into the cell It helps control skeletal muscle movements It is inhibitory All of the choices are correct

All of the choices are correct

Which of the following is/are a location of nicotinic ACh receptors? Autonomic ganglia Skeletal muscle Specific regions of the brain All of the choices are correct

All of the choices are correct.

At resting membrane potential: Sodium leaks towards... ATPase pumps move K+ towards... The NA+ gradient is towards the...

Extracellular Fluid

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

IPSP

At resting membrane potential: Potassium leaks towards... ATPase pumps move NA+ towards... The K+ gradient is towards the...

Intracellular Fluid

How does glycine act to control skeletal movements?

It inhibits the antagonist's action by causing IPSPs.

Complete the sentences describing interaction of muscarinic ACh receptors and K+ channels. 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

_______________ the time between signals sent from the same presynaptic terminal increases the strength of the graded potential. This is an example of ________________ summation.

Reducing; temporal

If demyelination occurs, why don't action potentials occur at regions of the axon that were previously myelinated?

These regions lack the appropriate concentration of voltage-gated sodium channels.

Indicate the summative effect that brings the initial segment closest to threshold.

Two EPSPs in proximity to each other

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

absolute refractory period

Substances that cause facilitation of a neuron ____________________________.

cause the neuron to fire that may not under the same circumstances in the absence of the facilitator

Demyelinating diseases cause a(n) ______________ in the conduction velocity of action potentials.

decrease

Action potentials occur ________________.

in the unmyelinated regions of an axon

When voltage-gated sodium channels are open, sodium flows _____________ the neuron making the inside of the cell more _______________.

into; positive

Complete the sentences describing activity of the muscarinic ACh receptor and G-proteins. 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-protiens; alpha; beta, gamma; beta, gamma

Graded potentials result from the opening of ________________.

ligand-gated channels

The suppression of neurotransmitter release from presynaptic terminals by retrograde release of endocannabinoids is called ________.

long-term depression

Assume in a laboratory you were able to isolate a neuron and remove the Acetylcholine receptors from the postsynaptic membrane. The substance _________________ would no longer cause facilitation of this neuron. nicotine caffeine

nicotine

Dopaminergic neurons of the mesolimbic dopamine system originate in the midbrain and terminate in the ________.

nucleus accumbens

An inhibitory postsynaptic potential results from the opening of ____________________.

potassium and/or chloride channels

Graded potentials are produced within the _______________________ segment of a neuron.

receptive

The following information best describes the _____________ phase of an action potential. - A membrane potential reading of +10 mV - Inactivated voltage-gated sodium channels - Open voltage-gated potassium channels

repolarization

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

temporal summation