Chapter 39: Neurons and Synapses

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Question: What are the functions of the nervous system? Answer:

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Detects changes in the external and internal environment.

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Center of mental activity.

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Coordinates with the endocrine system to maintain homeostasis.

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Responds to sensory information by issuing motor responses.

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Body’s communication system.

2.

Question: What is the central nervous system (CNS)? Answer: The Brain and the spinal cord, and is the integration center.

3.

Question: What is the peripheral nervous system (PNS)? Answer: All neuronal tissue outside the CNS, including cranial and spinal nerves.

4.

Question: Describe the pathway of information processing in the nervous system. Answer: Stimulus-sensory receptors-afferent neurons (sensory)-integration center (CNS)-efferent neurons (motor)-effector (muscles and glands).

5.

Question: What is a neuron? Answer: Electrically excitable cell that transmits impulses.

6.

Question: What is the role of dendrites? Answer: Receive neuronal impulses and transmit them to the cell body.

7.

Question: What is the role of axons? Answer: Conduct neuronal impulses away from the cell body.

8.

Question: What are neuroglia (glial cells)? Answer: Non-neuronal cells having supportive functions.

9.

Question: List the types of neuroglia cells. Answer: Astrocytes, Oligodendrocytes, Schwann cells, Microglia, Ependymal cells, and Satellite cells.

10.

Question: What is the function of afferent (sensory) neurons? Answer: Carry sensory information towards the CNS.

11.

Question: What is the function of efferent (motor) neurons? Answer: Carry the response signals from the brain to responsive networks.

12.

Question: What is the function of interneurons? Answer: Integrate the neural messages.

13.

Question: What is a synapse? Answer: Neurons connect and communicate with other neurons or effector cells.

14.

Question: What is a neuromuscular junction (NMJ)? Answer: Synapse between a neuron and a muscle.

15.

Question: What happens to the action potential at the synapse? Answer: Action potential (electric current) is converted into a chemical signal (in the form of neurotransmitters) at the synapse.

16.

Question: What are the two types of synapses? Answer: Electrical and Chemical.

17.

Question: Describe electrical synapses. Answer: Ions flow from one cell to another via gap junctions and plasma membranes are in direct contact, allowing rapid signal conduction.

18.

Question: Describe chemical synapses. Answer: Presynaptic and postsynaptic neurons are separated by a synaptic cleft; neurotransmitter release upon arrival of an action potential.

19.

Question: What is membrane potential? Answer: Electrical potential in the cell’s interior.

20.

Question: What contributes to the membrane potential? Answer: Difference in the ionic concentration between the cytosol and the ECF.

21.

Question: What is resting membrane potential? Answer: Membrane potential of an unstimulated resting cell.

22.

Question: What is the resting membrane potential of a neuron? Answer: -70mV (negative inside).

23.

Question: How do cells respond to stimuli? Answer: By changing the resting membrane potential.

24.

Question: What are passive ion channels? Answer: Leaky channels that are always open.

25.

Question: What are active ion channels? Answer: Gated channels that open or close in response to specific stimuli.

26.

Question: What are chemically-gated or ligand-gated channels? Answer: Respond to binding to a ligand.

27.

Question: What are voltage-gated channels? Answer: Respond to changes to voltage or potential difference.

28.

Question: What are mechanically-gated channels? Answer: Respond to changes in mechanical pressure or vibration.

29.

Question: What is a graded potential? Answer: A temporary and localized change in the resting membrane potential.

30.

Question: What is an action potential? Answer: A propagated electrical potential along the surface of the axon.

31.

Question: What is the threshold potential? Answer: The membrane potential at which an action potential begins.

32.

Question: What are neurotransmitters? Answer: Endogenous chemicals that allow neurons to communicate with each other throughout the body.

33.

Question: What is the principal excitatory neurotransmitter in the brain? Answer: Glutamate.

34.

Question: What are the major inhibitory neurotransmitters? Answer: Gamma-aminobutyric acid (GABA) and glycine.

35.

Question: Where is Acetylcholine released? Answer: At the neuromuscular junction.

36.

Question: What is an excitatory postsynaptic potential (EPSP)? Answer: Results from neurotransmitter binding causing gated Na+ channels to open and cause depolarization.

37.

Question: What is an inhibitory postsynaptic potential (IPSP)? Answer: Results from neurotransmitter binding to voltage-gated potassium / chloride channels and causing hyperpolarization.

38.

Question: What is temporal summation? Answer: Occurs on a membrane that receives multiple depolarizing stimuli from the same source in rapid succession.

39.

Question: What is spatial summation? Answer: More than 2 stimuli arrive at the same time but at different locations.

Chapter 39 Workshop

40.

Question: Reception Answer: Detection of stimuli by specialized sensory neurons those in eye and skin (Sensory receptors).

41.

Question: Transmission Answer: Is the sending of a message along a neuron, and then to another neuron or to a muscle or gland.

42.

Question: Integration Answer: Neuronal processing of signals from sensory neurons.

43.

Question: Response Answer: Output or action produced by the brain; and activating muscles, and hormone-secreting glands (Effector organs).

44.

Question: The functional unit of the nervous system is the _____ Answer: Neuron.

45.

Question: ____ are densely branched structures that receive stimuli from other nerve cells Answer: Dendrites.

46.

Question: The ___ _____ is the point where the membranes of an axon contacts the membrane of the cell body Answer: Axon hillock.

47.

Question: ____ neurons send signals from the stimuli to brain Answer: Afferent.

48.

Question: ____ neurons carry the response signals from the brain to the responsive networks Answer: Efferent.

49.

Question: ____neurons integrate the neural messages Answer: Interneurons.

50.

Question: What is the largest and most numerous neuroglia in the CNS? What kind of protective structure do they form? Answer: Astrocytes; Blood Brain Barrier (BBB).

51.

Question: What cells line the ventricles within the CNS? What do they produce and circulate? Answer: Ependymal cells; Cerebrospinal Fluid (CSF).

52.

Question: What cells act as the big dogs of the brain and don’t let the pathogens bother the neurons? Answer: Microglia (big dog).

53.

Question: What cells wrap the neurons of the CNS in myelin? Answer: Oligodendrocytes.

54.

Question: What cells wrap the neurons of the PNS in myelin? Answer: Schwann cells.

55.

Question: Satellite cells provide nutrients and structural support for neurons in the PNS Answer: T (True).

56.

Question: Myelination slows neuronal conduction Answer: F (False); Myelination SPEEDS up neural conduction.

57.

Question: The two types of neuroglia in the PNS are the Satellite cells and Oligodendrocytes Answer: F (False); the two types of neuroglia in the PNS are Satellite cells and schwann cells.

58.

Question: Afferent neurons send nerve signals from the brain to the responsive networks Answer: F (False); Efferent neurons take signals from the brain to the responsive networks.

59.

Question: Action potentials leap from one node to the other, this process is called ______ ________ Answer: Saltatory Propagation.

60.

Question: The small segments of uncovered axons between the myelinated sections are called ___ __ _____ Answer: Nodes of Ranvier.

61.

Question: _____ myelinate multiple axons in the CNS, while _____ cell myelinate one axon per cell in the PNS Answer: Oligo’s, Schwann cells.

62.

Question: What is myelin? Answer: A lipid-rich material that surrounds the nerve cell axons to insulate them and increase the rate at which electrical pulses (action potentials) are passed along the axon.

63.

Question: What cells form the blood brain barrier? Answer: Astrocytes.

64.

Question: ____ cells are involved in the production and circulation of cerebrospinal fluid (CSF)? Answer: Ependymal.

65.

Question: _____ matter contains _____, while ____ matter contains myelinated axons Answer: Grey matter contains neuronal cell bodies, while white matter contains myelinated axons.

66.

Question: What is a synapse? Answer: A synapse is where a neuron makes a COMMUNICATING CONNECTION with another neuron or effector.

67.

Question: What is the structure of the synapse? Answer: One side of the synapse = axon terminal of the presynaptic cell (neuron that transmits signal), while the other side of the synapse is the postsynaptic cell (dendrite or effector cell that receives signal).

68.

Question: What are the two types of synapses? Answer: Electrical synapse (DIRECT electrical flow) and the Chemical synapse (chemical NEUROTRANSMITTER).

69.

Question: Which type of synapse makes up the majority of synapses in the mammalian CNS? Answer: The chemical synapse.

70.

Question: Plasma membranes of the presynaptic and and postsynaptic cells are in direct contact Answer: Electrical Synapse.

71.

Question: Presynaptic and postsynaptic cells are separated by a narrow synaptic cleft Answer: Chemical Synapse.

72.

Question: Ions flow through gap junctions, allowing impulses to pass directly to the postsynaptic cell Answer: Electrical Synapse.

73.

Question: When an electrical impulse arrives at an axon terminal, a neurotransmitter is released into the synaptic cleft. Answer: Chemical Synapse.

74.

Question: Found in cardiac muscle, retina of eye, and pulp of tooth Answer: Electrical Synapse.

75.

Question: Allows rapid signal conduction Answer: Electrical Synapse.

76.

Question: Neurotransmitter diffuses across synaptic cleft and binds to a receptor in postsynaptic cell membrane Answer: Chemical Synapse.

77.

Question: Unregulated - either “on” or “off” Answer: Electrical Synapse.

78.

Question: Rare in both adult CNS and PNS Answer: Electrical Synapse.

79.

Question: Channel proteins in plasma membranes form gap junctions Answer: Electrical Synapse.

80.

Question: A synaptic connection between a neuron and muscle cell is known as ______ Answer: Neuromuscular junction (NMJ).

81.

Question: The axon terminals of a presynaptic neuron releases ____ into the synaptic cleft. Within the axon terminal, neurotransmitters are contained in ______ Answer: Neurotransmitters, synaptic vesicles.

82.

Question: Arrival of action potential to a chemical synapse Answer: 1.

83.

Question: Ca2+ removal Answer: 9.

84.

Question: Activation of receptors leads to altered flux of ions in the postsynaptic neuron resulting in the transmission of impulse Answer: 4.

85.

Question: Fusion and release Answer: 8.

86.

Question: Binding of Ca2+ to proteins Answer: 6.

87.

Question: Neurotransmitter molecules released by exocytosis Answer: 2.

88.

Question: Removal of neurotransmitter Answer: 10.

89.

Question: Neurotransmitters diffuse across synaptic cleft and bind to receptor proteins Answer: 3.

90.

Question: Ca2+ increase Answer: 5.

91.

Question: Resting membrane potential of an unstimulated, resting cell is known as the resting membrane potential Answer: True!.

92.

Question: K+ is the main cation in the ECF; Na+ is the main cation in the cytosol Answer: False - K+ is the main cation in the CYTOSOL and Na+ is the main cation in the ECF.

93.

Question: The resting membrane potential of a neuron is typically -60mV Answer: False - 70mV.

94.

Question: Which type of ion channel are leak channels that are always open? Answer: Passive ion channels.

95.

Question: Why are they important? Answer: Establish the normal membrane potential of the cell.

96.

Question: Which type of ion channel open or close in response to specific stimuli? Answer: Active ion channels (gated channels).

97.

Question: What are the three classes of this type of ion channel and name their function? Answer: Ligand- gated: respond to binding to a ligand, Voltage- gated: respond to changes in voltage/ potential differences, Mechanically- gated: respond to changes in mechanical pressure.

98.

Question: Sodium and potassium ion channels Answer: Voltage- gated.

99.

Question: The binding of acetylcholine at a neuromuscular junction Answer: Ligand- gated.

100.

Question: Sensory receptor that responds to pressure Answer: Mechanically- gated.

101.

Question: What is the term for shifting a cell’s resting membrane to a more positive level? Answer: Decrease.

102.

Question: What is the temporary period after repolarization where the channels are closed but capable of opening, and until all the potassium ion channels have completely closed, potassium ions are continuously leaving the cell? Answer: Hyperpolarization.

103.

Question: The period during which the neuronal plasma membrane does not respond to additional depolarizing signal from the time an action potential is initiated until the normal resting membrane potential is achieved is called Answer: Refractory period.

104.

Question: Step 1 of Saltatory propagation Answer: An action potential has occurred at the initial segment.

105.

Question: Step 2 of Saltatory propagation Answer: A local current produces a graded depolarization that brings the axolemma at the next node to threshold.

106.

Question: Step 3 of Saltatory propagation Answer: An action potential develops at node 2.

107.

Question: Step 4 of Saltatory propagation Answer: A local current produces a gradient depolarization that brings the axolemma at node 3 to threshold.

108.

Question: The two main types of neurotransmitter receptors are ___________ and ___________ Answer: Ionotropic & Metabotropic receptors.

109.

Question: Postsynaptic potentials can be _________________ or ______________ Answer: Excitatory (EPSP) or Inhibitory (IPSP).

110.

Question: ________________ postsynaptic potential is caused by depolarization of the postsynaptic membrane Answer: Excitatory.

111.

Question: ________________ postsynaptic potential is caused by hyperpolarization of the postsynaptic membrane Answer: Inhibitory.

112.

Question: When chemically gated _____________ channels open in the plasma membrane, the cell is said to be _____________ and results in an _______________ postsynaptic potential Answer: Potassium/ chloride; hyperpolarized; IPSP.

113.

Question: When chemically gated _____________ channels open in the plasma membrane, the cell is said to be _____________ and results in an _______________ postsynaptic potential Answer: Sodium; depolarized; EPSP.

114.

Question: Ionotropic receptors Answer: Are ligand-gated Ion channels.

115.

Question: Metabotropic receptors Answer: Are G-Protein coupled receptors.

116.

Question: Metabotropic receptors Answer: Has delayed but longer lasting changes in membrane potential of postsynaptic cell.

117.

Question: Metabotropic receptors Answer: Triggers an intracellular signalling cascade via a second messenger, cAMP.

118.

Question: The change in membrane potential of the postsynaptic cell lasts after the reuptake of the neurotransmitter Answer: False, it only lasts as long as the neurotransmitter is in the cleft.

119.

Question: Graded potential produced by Ach binding is an IPSP Answer: False, it is an EPSP.

120.

Question: A single EPSP results in an action potential and depolarization of the membrane Answer: False.

121.

Question: What are the steps for activation of metabotropic receptors? Answer: Step 1: Neurotransmitter binds to a G-protein coupled receptor, Step 2: G protein is activated, Step 3: Adenylyl cyclase is activated and uses ATP to make cAMP, Step 4: cAMP activates intracellular enzymes or opens ion channels.

122.

Question: What are the steps of an EPSP generation? Answer: Step 1: An impulse at the presynaptic terminal triggers the release of a neurotransmitter, Step 2: The neurotransmitter binds to an ion channel at the postsynaptic membrane. If Na+ enters, the cell becomes depolarized, Step 3: The change in membrane potential is the EPSP.

123.

Question: Explain what summation is and distinguish between the two types of summations. Answer: Summation is the integration of multiple postsynaptic potentials to add the effect of their graded potentials. A. Temporal Summation: →same space, different Time, B. Spatial Summation: →different Space, same time.

124.

Question: Main excitatory neurotransmitter in mammalian brain Answer: Glutamate.

125.

Question: Main Inhibitory neurotransmitter in mammalian brain Answer: GABA.

126.

Question: Excitatory neuron that is released at the neuromuscular junction and diffuses throughout the brain Answer: Acetylcholine