fns Flashcards
(206 cards)
1
Q
What are the three overlapping functions of the nervous system?
A
Sensory input, integration, and motor output.
2
Q
what is sensory input
A
The gathering of information by sensory receptors about changes inside and outside the body.
3
Q
What is integration in the nervous system?
A
Processing and interpreting sensory input and deciding what action to take.
4
Q
What is motor output?
A
Activation of muscles and glands to cause a response
5
Q
In the driving example, what is the sensory input, integration, and motor output?
A
Sensory input: seeing the red light; Integration: deciding to stop; Motor output: pressing the brake.
6
Q
What are the two main parts of the nervous system?
A
central nervous system (CNS) and peripheral nervous system (PNS).
7
Q
What structures are included in the central nervous system (CNS)?
A
Brain and spinal cord.
8
Q
What does the CNS do?
A
It interprets sensory input and dictates motor output
9
Q
What is the peripheral nervous system (PNS)?
A
the part of the nervous system outside the CNS, made of nerves and ganglia.
10
Q
What are spinal nerves and cranial nerves?
A
Spinal nerves carry impulses to and from the spinal cord; cranial nerves carry impulses to and from the brain.
11
Q
What are the two functional subdivisions of the PNS?
A
Sensory (afferent) division and motor (efferent) division
12
Q
What does the sensory (afferent) division do?
A
Carries impulses to the CNS from sensory receptors.
13
Q
What do somatic sensory fibers carry information from?
A
skin, skeletal muscles, and joints.
14
Q
What do visceral sensory fibers carry information from?
A
Visceral organs
14
Q
What does the motor (efferent) division do?
A
carries impulses from the CNS to muscles and glands to cause a response.
14
Q
What does the somatic nervous system control?
A
Voluntary movements of skeletal muscles.
14
Q
What are the two parts of the motor division?
A
Somatic nervous system and autonomic nervous system (ANS).
15
Q
What does the autonomic nervous system (ANS) control?
A
Involuntary functions like heart pumping and digestion.
16
Q
What are the two subdivisions of the autonomic nervous system?
A
Sympathetic division and parasympathetic division.
17
Q
How do the sympathetic and parasympathetic divisions interact?
A
They usually work in opposition: one stimulates, the other inhibits.
18
Q
What are the two main types of cells in nervous tissue?
A
Neuroglia (supporting cells) and neurons (excitable nerve cells).
19
Q
What do neuroglia (glial cells) do?
A
Support, protect, and wrap neurons
20
Q
What is the function of neurons?
A
To respond to stimuli and transmit electrical signals.
21
Q
What are neuroglia (glial cells)?
A
Smaller cells that associate closely with neurons, supporting and protecting them.
22
How many types of neuroglia are there, and how are they distributed?
Six types: four in the CNS and two in the PNS.
22
What are the four types of CNS neuroglia?
Astrocytes, microglial cells, ependymal cells, and oligodendrocytes.
23
What are the two types of PNS neuroglia?
Satellite cells and Schwann cells.
24
Which glial cell is the most abundant in the CNS?
Astrocytes.
25
What are the main functions of astrocytes?
Support neurons, anchor them to blood vessels, help with nutrient exchange, clean up potassium ions and neurotransmitters, guide young neurons, and assist in synapse formation.
26
How do astrocytes communicate with each other?
Through calcium waves and chemical messengers via gap junctions
27
What is the main role of microglial cells?
Monitor neuron health and act as macrophages by phagocytizing debris and invading microorganisms.
28
Why are microglial cells important in the CNS?
Because immune cells have limited access to the CNS.
29
What do ependymal cells do?
Line the brain and spinal cord cavities, form a barrier between cerebrospinal fluid and tissue fluid, and help circulate cerebrospinal fluid with their cilia.
30
What is the main function of oligodendrocytes?
Form myelin sheaths around CNS nerve fibers.
31
What do satellite cells do?
Surround neuron cell bodies in the PNS and perform similar functions to astrocytes.
32
What do Schwann cells do?
Surround PNS nerve fibers, form myelin sheaths around thicker fibers, and aid in nerve regeneration.
33
Which PNS glial cell is vital for nerve fiber regeneration?
Schwann cells.
34
How are Schwann cells similar to oligodendrocytes?
Both form myelin sheaths around nerve fibers.
35
What are the three special characteristics of neurons besides excitability?
Extreme longevity, amitotic (cannot divide), and high metabolic rate.
35
What are neurons (nerve cells)?
Structural units of the nervous system that conduct nerve impulses.
36
Can neurons divide and be replaced if destroyed?
No, neurons are generally amitotic, but there are exceptions like stem cells in the olfactory epithelium and hippocampus.
37
Why do neurons require a constant supply of oxygen and glucose?
Because of their exceptionally high metabolic rate; they can't survive long without oxygen.
38
What are the two main parts of a neuron?
The cell body and one or more processes.
39
What are other names for the neuron cell body?
Perikaryon or soma.
40
What important role does the plasma membrane of the neuron cell body play?
Acts as part of the receptive region that receives signals from other neurons
41
What is the major biosynthetic and metabolic center of a neuron?
The neuron cell body.
42
What organelles are abundant in neuron cell bodies for making proteins?
Rough ER (chromatophilic substance/Nissl bodies), free ribosomes, and Golgi apparatus.
43
What is chromatophilic substance?
Another name for the rough endoplasmic reticulum in neurons; it stains darkly with basic dyes.
44
What cytoskeletal elements maintain a neuron's shape?
Microtubules and neurofibrils (bundles of neurofilaments).
45
What pigments can be found in neuron cell bodies?
Melanin, a red iron-containing pigment, and lipofuscin.
46
What is lipofuscin and why is it called the "aging pigment"?
A golden-brown pigment from lysosomal activity that accumulates with age.
47
Where are most neuron cell bodies located?
In the central nervous system (CNS).
48
What are clusters of neuron cell bodies called in the CNS and PNS?
CNS: nuclei; PNS: ganglia.
49
What part of the neuron extends from the cell body?
Armlike processes (dendrites and axons).
50
What are the two types of neuron processes?
Dendrites and axons.
50
What does the CNS contain compared to the PNS?
CNS: neuron cell bodies and processes; PNS: mainly neuron processes.
50
Describe dendrites of motor neurons.
Short, tapering, diffusely branching extensions close to the cell body.
51
What are dendritic spines?
Thorny appendages on dendrites that represent synapses with other neurons.
52
What type of electrical signal do dendrites convey?
Graded potentials (short-distance signals).
53
Where does an axon originate from on the neuron?
The axon hillock.
54
What is a long axon called?
A nerve fiber
55
What are bundles of axons called in the CNS and PNS?
CNS: tracts; PNS: nerves.
56
What are axon branches called along its length?
Axon collaterals.
57
What are the knoblike endings of axon terminals called?
Axon terminals.
58
What is the function of the axon?
conducting region that generates and transmits nerve impulses away from the cell body.
59
What is released at axon terminals?
Neurotransmitters
60
Why do axons depend on the cell body?
Because axons lack rough ER and a Golgi apparatus needed for protein synthesis and packaging.
61
What happens if an axon is cut or severely damaged?
It quickly decays.
62
What is anterograde movement in axonal transport?
Movement away from the cell body, carrying mitochondria, cytoskeletal elements, and membrane components.
63
What is retrograde movement in axonal transport?
Movement toward the cell body, carrying organelles and signal molecules.
64
What proteins drive axonal transport?
Motor proteins like kinesin (anterograde) and dynein (retrograde).
65
Which diseases use retrograde axonal transport to reach the neuron cell body?
Polio, rabies, herpes simplex virus, and tetanus toxin.
66
How could retrograde transport be used therapeutically?
To deliver viruses containing corrected genes or microRNA for genetic disease treatment.
67
What is the myelin sheath made of?
whitish, fatty (protein-lipoid) substance.
68
What are the functions of the myelin sheath?
protects and electrically insulates axons; increases nerve impulse transmission speed.
69
Are dendrites myelinated?
No, dendrites are always nonmyelinated
70
What cells form the myelin sheath in the PNS?
Schwann cells.
70
What is the outer collar of perinuclear cytoplasm?
the Schwann cell cytoplasm and nucleus squeezed outside the myelin sheath.
70
What are gaps between adjacent Schwann cells called?
Nodes of Ranvier.
71
What cells form the myelin sheath in the CNS?
Oligodendrocytes.
72
How are nonmyelinated fibers in the PNS associated with Schwann cells?
A single Schwann cell partially encloses many axons without coiling.
73
How many axons can one oligodendrocyte myelinate?
Up to 60 axons.
74
Do CNS myelin sheaths have an outer collar of perinuclear cytoplasm?
no
75
How are neurons structurally classified?
By the number of processes extending from the cell body.
76
What are the three structural types of neurons?
Multipolar, bipolar, and unipolar.
77
What is the most common type of neuron in humans?
Multipolar neurons.
78
Where are bipolar neurons found?
In special sense organs (e.g., retina, olfactory mucosa).
79
Where are unipolar neurons mainly found?
In ganglia in the PNS.
80
What type of neurons are most unipolar neurons?
Sensory neurons.
81
In unipolar neurons, what is the peripheral process associated with?
Sensory receptors.
82
What is the functional classification of neurons based on?
The direction nerve impulses travel relative to the CNS.
83
What are the three functional classes of neurons?
Sensory (afferent), motor (efferent), and interneurons.
84
What do sensory neurons do?
Transmit impulses from sensory receptors toward the CNS.
85
What do motor neurons do?
Carry impulses away from the CNS to muscles and glands.
85
Are sensory neurons mostly unipolar or multipolar?
Mostly unipolar.
86
Are motor neurons multipolar or unipolar?
multipolar
86
What do interneurons do?
Connect sensory and motor neurons and perform integration within the CNS.
87
What type of neuron makes up over 99% of neurons in the body?
Interneurons.
88
What unique ability do neurons have compared to most other cells?
They can rapidly change their membrane potential.
89
What is the human body's overall electrical charge?
it is electrically neutral.
90
What is voltage?
The measure of potential energy generated by separated electrical charges.
90
What is current?
The flow of electrical charge from one point to another.
90
What is resistance?
The hindrance to charge flow provided by the material through which current must pass.
91
In the body, what reflects electrical currents?
The flow of ions across cellular membranes.
91
According to Ohm’s law, what is the relationship between current and voltage?
Current is directly proportional to voltage.
92
How is current related to resistance?
Current is inversely related to resistance.
93
What provides the resistance to current flow in a neuron?
The plasma membrane.
94
What are leakage channels?
Ion channels that are always open.
95
What are chemically gated channels?
Channels that open when a specific chemical binds.
96
What are voltage-gated channels?
Channels that open and close in response to changes in membrane potential.
97
What determines the direction ions move across a membrane?
The electrochemical gradient.
97
What are mechanically gated channels?
Channels that open in response to physical deformation.
98
What is the resting membrane potential of a typical neuron?
-70mV
99
Why is the inside of the resting neuron negatively charged?
Because potassium (K⁺) leaks out more easily than sodium (Na⁺) leaks in.
100
What role does the sodium-potassium pump play in neurons?
It maintains the concentration gradients of Na⁺ and K⁺ across the membrane.
101
What two factors generate the resting membrane potential?
Ionic composition differences and membrane permeability differences.
102
What are graded potentials?
Incoming signals operating over short distances with variable strength.
103
what are action potentials?
long-distance signals of axons that always have the same strength
104
What is depolarization?
A decrease in membrane potential, making the inside less negative.
105
What is hyperpolarization?
An increase in membrane potential, making the inside more negative.
106
How does depolarization affect nerve impulse probability?
It increases the probability.
107
How does hyperpolarization affect nerve impulse probability?
It decreases the probability.
108
Why are graded potentials called “graded”?
Because their magnitude varies directly with stimulus strength.
108
What happens to the magnitude of a graded potential as it spreads?
It decreases with distance—graded potentials are decremental.
108
What triggers a graded potential?
A stimulus that opens gated ion channels in a neuron's membrane.
108
What two types of changes can graded potentials cause in membrane potential?
Depolarizations or hyperpolarizations.
108
What are graded potentials?
Short-lived, localized changes in membrane potential, typically in dendrites or the cell body.
109
What is a receptor (or generator) potential?
A graded potential produced when a sensory receptor is excited by a stimulus like light, pressure, or chemicals.
110
What is a postsynaptic potential?
A graded potential produced when a neurotransmitter released by another neuron binds to receptors on the postsynaptic membrane.
111
How does current flow during a graded potential?
positive ions move toward more negative areas and negative ions move toward more positive areas, spreading the depolarization.
112
What happens to ions during depolarization inside and outside the cell?
Inside: K⁺ moves away from the depolarized area;
Outside: Na⁺ moves toward the depolarized area.
113
Why do graded potentials decay quickly?
Because most of the charge is lost through leakage channels in the permeable membrane.
114
Why can graded potentials only act over short distances?
Their currents dissipate quickly and decay with distance.
115
What is the role of graded potentials in neural signaling?
They help initiate action potentials, which are long-distance signals.
116
What type of cells can generate action potentials?
Only cells with excitable membranes—neurons and muscle cells
117
What is an action potential (AP)?
: A brief reversal of membrane potential with a change of about 100 mV.
118
How does an action potential differ from a graded potential?
Action potentials do not decay with distance; graded potentials do.
119
What happens during the resting state of an action potential?
All voltage-gated Na⁺ and K⁺ channels are closed; only leakage channels are open.
120
What triggers depolarization in a neuron?
voltage-gated Na⁺ channels open, allowing Na⁺ to enter the cell.
121
What is the threshold for generating an action potential?
Typically a depolarization of 15–20 mV from resting potential.
122
What occurs during repolarization?
Na⁺ channels inactivate, and K⁺ channels open, allowing K⁺ to leave the cell.
123
What causes hyperpolarization?
K⁺ channels remain open longer than necessary, allowing excessive K⁺ efflux.
124
What is the all-or-none phenomenon in action potentials?
an AP either happens completely or not at all once threshold is reached.
125
What ensures the one-way transmission of APs?
the absolute refractory period where Na⁺ channels are inactivated.
126
What is the role of voltage-gated channels in AP generation?
They allow Na⁺ and K⁺ movement that drives the membrane potential changes.
127
What is the difference between absolute and relative refractory periods?
Absolute: no new APs can be generated. Relative: a very strong stimulus can trigger another AP.
128
How does an AP propagate along the axon?
Through local currents that depolarize adjacent membrane segments.
129
What is saltatory conduction?
AP jumps between nodes of Ranvier in myelinated axons, speeding transmission.
130
What is continuous conduction?
Slow AP propagation in nonmyelinated axons as channels activate sequentially.
131
What two main factors influence AP conduction velocity?
Axon diameter and degree of myelination.
132
Which fiber group conducts impulses the fastest?
Group A fibers (large diameter, heavily myelinated, up to 150 m/s).
133
Which fiber group conducts impulses the slowest?
Group C fibers (small diameter, unmyelinated, 1 m/s or less).
134
What happens in multiple sclerosis (MS)?
Myelin sheaths in the CNS are destroyed, impairing impulse conduction.
135
How do local anesthetics affect action potential generation?
They block voltage-gated Na⁺ channels, preventing AP initiation.
136
Why do fingers go numb when exposed to cold?
Cold interrupts blood flow, impairing impulse conduction.
137
What is a synapse?
A junction that mediates information transfer from one neuron to another or to an effector cell.
138
What is the role of the presynaptic neuron?
It conducts impulses toward the synapse and sends the information
139
Can a single neuron be both presynaptic and postsynaptic?
Yes, most neurons function as both.
139
What is the role of the postsynaptic neuron?
It transmits electrical signals away from the synapse and receives the information.
140
How many axon terminals can a single neuron have?
Between 1,000 and 10,000.
141
What is an axodendritic synapse?
A synapse between the axon of one neuron and the dendrites of another.
142
What is an axosomatic synapse?
A synapse between the axon of one neuron and the soma (cell body) of another.
143
Name less common types of synapses.
Axoaxonal, dendrodendritic, and somatodendritic
144
What are the two main types of synapses?
Electrical synapses and chemical synapses.
145
What structure allows electrical synapses to connect neurons?
Gap junctions made of connexons.
146
How do ions travel in electrical synapses?
Directly from one neuron to the next through gap junctions.
147
Are electrical synapses faster or slower than chemical synapses?
faster
148
Where are electrical synapses found in adults?
In brain regions controlling stereotyped movements, like eye movements, and in the hippocampus.
149
Why are electrical synapses more common in embryos?
they help neurons synchronize and connect properly during development.
150
What is the most common type of synapse in the nervous system?
Chemical synapses.
151
What is released at a chemical synapse?
Neurotransmitters.
152
What separates the presynaptic and postsynaptic membranes at a chemical synapse?
The synaptic cleft.
153
How wide is the synaptic cleft?
Approximately 30 to 50 nanometers.
154
What are the two main parts of a chemical synapse?
The axon terminal with synaptic vesicles and the neurotransmitter receptor region on the postsynaptic membrane.
155
What is the first step in neurotransmission at a chemical synapse?
Arrival of an action potential at the axon terminal.
156
What ion enters the axon terminal upon depolarization?
Calcium ions (Ca²⁺).
157
How many vesicles release neurotransmitters per nerve impulse?
Potentially around 300 vesicles.
158
What triggers the release of neurotransmitters?
influx of Ca²⁺ causes synaptic vesicles to fuse with the membrane and release neurotransmitters by exocytosis.
159
What happens after neurotransmitter release?
Neurotransmitters diffuse across the cleft and bind to receptors on the postsynaptic membrane.
160
What is the result of neurotransmitter binding on the postsynaptic cell?
ion channels open, generating graded potentials.
161
how are neurotransmitter effects terminated?
By reuptake, enzymatic degradation, or diffusion away from the synapse.
162
Give an example of neurotransmitter reuptake.
Norepinephrine is reabsorbed and broken down in the presynaptic terminal.
163
Give an example of enzymatic degradation.
Acetylcholine is broken down by enzymes in the synaptic cleft.
164
What causes synaptic delay?
Time required for neurotransmitter release, diffusion, and receptor binding.
165
What is the rate-limiting step in neural transmission?
Transmission across a chemical synapse.
166
how long does a typical synaptic delay last?
0.3 to 5.0 milliseconds.
167
What type of ion channels are found on postsynaptic membranes at chemical synapses?
Chemically gated ion channels
168
How do chemically gated ion channels differ from voltage-gated ion channels?
Chemically gated channels are relatively insensitive to changes in membrane potential and do not self-amplify.
169
What type of potential do chemically gated channels generate?
Graded potentials.
170
What determines the strength of graded potentials?
The amount of neurotransmitter released and the duration it remains in the synaptic area.
171
What is the effect of neurotransmitter binding at an excitatory synapse?
It depolarizes the postsynaptic membrane, creating an EPSP (excitatory postsynaptic potential).
172
Why don't EPSPs typically generate action potentials directly?
Because postsynaptic membranes lack voltage-gated channels required for AP generation.
172
What is the function of EPSPs?
To help trigger an AP at the axon’s initial segment if the threshold is reached.
172
Why does sodium influx exceed potassium efflux at excitatory synapses?
Because the electrochemical gradient for sodium is steeper than for potassium.
173
What causes an inhibitory postsynaptic potential (IPSP)?
Opening of K⁺ or Cl⁻ channels, leading to hyperpolarization.
173
What are the two types of summation?
Temporal summation and spatial summation.
174
What is summation in the context of postsynaptic potentials?
The additive effect of EPSPs and IPSPs to influence neuron activity.
175
What happens when excitatory input dominates and threshold is reached?
The neuron fires an action potential.
176
What does it mean when a neuron is "facilitated"?
It is depolarized but not to threshold, making it more likely to fire next time.
177
Where are inhibitory synapses most effective?
On the cell body, between excitatory inputs and the axon hillock.
177
What is synaptic potentiation?
Enhanced neurotransmission due to repeated or continuous use of a synapse.
178
What is long-term potentiation (LTP)?
A type of synaptic plasticity related to learning and memory, especially in the hippocampus.
179
What is presynaptic inhibition?
When one neuron inhibits neurotransmitter release from another neuron at an axoaxonal synapse.
180
How does presynaptic inhibition differ from postsynaptic inhibition?
Presynaptic inhibition reduces neurotransmitter release; postsynaptic inhibition hyperpolarizes the membrane.
181
What neurotransmitters are often deficient in depression?
Serotonin, dopamine, and noradrenaline.
182
What mental disorders are associated with increased or altered synaptic transmission?
Schizophrenia, bipolar disorder, substance abuse, and dementia.
