Neurophysiology Flashcards
1
Q
The nervous system consists of two major divisions: ____ and _____.
A
Central Nervous System (CNS) and the Peripheral Nervous System.
2
Q
Function of the Nervous System
A
- Control and communicate activities of the body.
- Regulate all bodily activities
- Interpret and commands activities of the body
3
Q
The functions are overlapping and follow the order: (3)
A
- Sensory (Input of information) 2. Integration (Process and Translate)
- Motor Output (Effect Activity)
4
Q
• Consists of the brain and spinal cord
• Occupies the dorsal cavity
- Integrative and control center
- Brain and Spinal Cord
A
CNS
5
Q
A complex set of brain structures that lies on both sides of the thalamus, right under the cerebrum.
- It supports a variety of functions, including emotion, behavior, motivation, long-term memory, and olfaction.
A
Limbic System
6
Q
It comprises multiple subcortical nuclei, of varied origin, in the brains of vertebrates, which are situated at the base of the forebrain. It is strongly interconnected with the cerebral cortex, thalamus, and brainstem, as well as several other brain areas.
- It is associated with a variety of functions including: control of voluntary motor movements, procedural learning, routine behaviors or “habits” such as bruxism, eye movements, cognition and emotion.
A
Basal Nuclei
7
Q
A region in the brainstem that is involved in multiple tasks such as regulating the sleep-wake cycle and filtering incoming stimuli to discriminate irrelevant background stimuli.
- It is essential for governing some of the basic functions of higher organisms, and is one of the phylogenetically oldest portions of the brain.
A
Reticular Formation Centre
8
Q
A brain structure located in the mesencephalon (midbrain) that plays an important role in reward, addiction, and movement.
A
Substantia Nigra
9
Q
the crossing of the fibers of the corticospinal tracts from one side of the central nervous system to the other near the junction of the medulla and the spinal cord
A
Decussation of Pyramids
10
Q
A set of connected nuclei in the brains of vertebrates that is responsible for regulating arousal and sleep-wake transitions. As its name implies, its most influential component is the reticular formation.
A
Reticular Activation System (RAS)
11
Q
An area of motor cortex lying within the frontal lobe of the brain just anterior to the primary motor cortex. It occupies part of Brodmann’s area
- The functions are diverse and not fully understood. It projects directly to the spinal cord and therefore may play a role in the direct control of behavior, with a relative emphasis on the trunk muscles of the body. It may also play a role in planning movement, in the spatial guidance of movement, in the sensory guidance of movement, in understanding the actions of others, and in using abstract rules to perform specific tasks
A
Pre-motor Cortex
12
Q
It belongs to the limbic system and plays important roles in the consolidation of information from short-term memory to long-term memory and spatial navigation. Humans and other mammals have two of these, one in each side of the brain. It is located under the cerebral cortex.
A
Hippocampus
13
Q
• Is composed of nerves and ganglia
• Functional, the ____ is divided into sensory and motor divisions and each of these divisions is sub-sectioned into somatic and visceral divisions.
- Communication lines between CNS and the rest of the body
A
PNS
14
Q
- Somatic and visceral sensory fibers
- Conducts impulses from receptors to CNS
A
Sensory (afferent) division
15
Q
- Motor nerve fibers
- Conducts impulses from the CNS to effectors (muscles and glands)
A
Motor (efferent) division
16
Q
- Visceral motor (involuntary)
- Conducts impulses from the CNS to cardiac muscles, smooth muscles, glands
A
ANS - Autonomic Nervous System
17
Q
- Somatic motor (voluntary)
- Conducts impulses from the CNS to the skeletal muscles
A
SNS - Somatic Nervous System
18
Q
Mobilizes body systems during activity. Fight or flight.
A
Sympathetic Division
19
Q
Conserves energy and promotes housekeeping functions during rest.
A
Parasympathetic Division
20
Q
Sensory (Afferent) Division: (2 subdivisions)
A
- Somatic sensory division
2. Visceral sensory division
21
Q
Division that carries signals mainly from the viscera of the thoracic and abdominal cavities (organs such as the heart, lungs, stomach and urinary bladder) to the CNS.
A
Visceral sensory division
22
Q
Division that carries signals from receptors in the skin, muscles, bones and joints to the CNS
A
Somatic sensory division
23
Q
Carries signals from the CNS mainly to muscles and gland (Effectors)
A
Motor (Efferent) Division
24
Q
2 subdivisions of motor (efferent) division
A
- Somatic motor division
2. Visceral motor division
25
Motor division that carries signals to skeletal muscles (the signs cause voluntary and involuntary muscle contraction).
Somatic motor division
26
Motor division that carries signal to gland cardiac muscle and smooth muscle. The functions are involuntary controlled and the system operates at the unconscious level. The AUTOMONIC NERVOUS SYSTEM (ANS) is a part of this division.
Visceral motor division
27
Two types of neural tissue.
neuroglia and neurons
28
Neuroglia outnumber neurons by a ratio of ____
10:1
29
Neuroglia number about _____ minimum, in a young person
10 000 million
30
Function of Neuroglia (4)
* Uptake of released neurotransmitters, e.g., uptake of GABA
* Development & Maintenance of the nervous system, e.g., multiple and an occupy areas from which neurons are lost. (Brain Tumours arise from glia cells since neurons do not undergo mitosis.)
* Provide mechanical support for neurons and prevent electrical interference between neuron by insulating neuron axons
* Form the blood brain barrier. Blood-Brain barrier is a concept based on the observation that certain chemicals transported in the blood which can get to soft tissue such as liver and kidney are prevented from reaching brain tissue.
31
Neuroglia (Glial Cells) in the CNS (4)
1. Oligodendrocytes
2. Ependymal cells
3. Microglia
4. Astrocytes
32
Neuroglia (Glial Cells) in the CNS
| - form myelin in the brain and spinal cord that cover thicker neuron fibres
Oligodendrocytes
33
Neuroglia (Glial Cells) in the CNS
- line cavities of the brain and spinal cord; secrete and stir cerebrospinal fluid (CSF) to promote circulation of the CSF.
Ependymal cells
34
Neuroglia (Glial Cells) in the CNS
| - the scavenger neuroglia; phagocytes that destroy microorganisms, foreign bodies and dead neural tissue.
Microglia
35
Neuroglia (Glial Cells) in the CNS
- most abundant neuroglia; cling to neurons and their synaptic ending; cover blood capillaries; brace and anchor neuron into position; control environment around neurons; influence neuron function and participate in information process in the brain; nourish neurons; act to form blood-brain-barrier; form scar tissue to replace damage neural tissue.
Astrocytes
36
Neuroglia in the PNS (2)
1. Schwann cells
| 2. Satellite cells
37
Neuroglia in the PNS
- wrap around the larger axons of nerve fibres; assist in the regeneration of damage nerve fibre; aid conduction of action potential.
Schwann cells
38
Neuroglia in the PNS
| - surround cell bodies of neurons located in ganglion (in PNS).
Satellite cells
39
Myelin lipid (whitish, fatty) layer that surround long and large diameter nerve fibres; it forms a _____.
myelin sheath
40
The myelin sheath is formed by spiralling layer of plasma membrane of an _____ or ______.
Oligodendrocyte or Schwann cells
41
Myelin sheath is associated only with the axons of a _____.
nerve fibre
42
_____ of nervous system begins in the 14th of foetal development and ends in late adolescence.
Myelination
43
In both PNS and CNS nerve fibres are much longer than a single glial cell; hence several glial cells are required to cover a fibre. The myelin sheath, therefore appear on the fibre in segments, hence the __________.
Nodes of Ranvier
44
Myelin protects and insulate ____.
fibres
45
Myelin increase the speed transmission of _____.
nerve impulses
46
__________ are found in the CNS and PNS. In both PNS and CNS small-diameter axons are unmyelinated.
Unmyelinated nerve fibres
47
In the PNS on Schwann cell may surround _____ small nerve fibres.
1-12
48
Regions of the CNS containing dense collection of myelinated fibres are referred to as _____ matter.
white matter
49
Grey matter contains mostly cell bodies and ______.
unmyelinated fibre
50
Disorders of Myelin (2)
1. Multiple sclerosis
| 2. Tay-Sach disease
51
PROPERTY OF NEURON (3)
1. Excitability 2. Conductivity
3. Secretion
52
All cells are excitable when stimulated by environmental stimuli.
Excitability
53
product electrical signal (action potential) that can travel to another cell.
Conductivity
54
secrete a chemical (neurotransmitter) that aid in the transmission of the electrical signal.
Secretion
55
FUNCTIONAL CLASSES OF NEURON (3)
1. Sensory (Afferent) Neurons
2. Interneurons (association neurons)
3. Motor (Efferent) Neurons
56
• neurons that detect stimuli such as light, heat, pressure; transmit information about stimuli to CNS; conducts to
Sensory (Afferent) Neurons
57
• neurons that lie entirely with the CNS; receive information from many neurons;
- process, integrate, store, retrieve information; make decisions.
- make up over 90% of all the body’s neurons.
Interneurons (association neurons)
58
Neurons that send information mostly to muscles and glands; conduct action potential away from the CNS.
Motor (Efferent) Neurons
59
NEURON STRUCTURE (4)
1. Anaxonic
2. Unipolar
3. Bipolar Neurons
4. Multipolar neurons.
60
Neurons that have multiple dendrite but no axon; communicate through their dendrite; do not produce action potential; found in the brain, retina and adrenal medulla.
Anaxonic neurons
61
Neurons that carry sensory information to the Spinal cord from the periphery; have branching dendrites in the skin; cell bodies dorsal ganglion.
Unipolar Neurons
62
Rare neurons that found in some sense organs (e.g., retina of eye and olfactory mucosa)
Bipolar Neurons
63
Most common type of neuron in the body (over 99% of all neurons).
Multipolar neurons
64
Within the axon material is transported via ______ of the cytoskeleton.
microtubules
65
The motors that carry the materials are _____.
proteins (transport proteins)
66
Transport proteins have ____ and ____ and carry material on their
cilia and flagella
67
There is a two-way conduction within the neuron axons: (2)
1) Anterograde transport
| 2) Retrograde transport
68
Transport that involves the movement of material such as proteins and chemicals made in the soma (cell body) to the axon membrane (e.g., protein for membrane repair) and axon terminals (e.g., acetylcholine, amino acids, glucose).
Anterograde transport
69
Transport that involves the movement of substances from the axonal terminal to the soma for recycling and disposal. Substance transported by this means include Herpes virus, polio virus, and tetanus toxin.
Retrograde transport
70
The potential energy generated by charged particles such as electrons and ions.
- is measured in volts (1 mV = 0.001V)
- is the difference in potential energy between two point in an electric field.
Voltage
71
The flow of charged particle (electron, ion) from one point in an electric field to another. It is measured in ampere (A); 1mA = 0.001A
Current
72
The hindrance of flow to current flow through a material.
Resistance
73
Resistance in a conductor is measured in ____.
ohms
74
If the resistance is high in a material the material is called an ______;
insulator
75
Tif the resistance is low, the substance is called a ____.
conductor
76
Voltage across a plasma membrane
Membrane Potential
77
The state of a plasma membrane of an un-stimulated cell membrane. The inside of the cell membrane is relatively negative (compared to the outside) because more protein is inside than outside the cell. (Protein carries a negative charge.) The outside is more positive because of high Na+ conc’n. and the inability of Na+ to diffuse easily across the membrane. In the polarized state, the number of K+ moving out of the cell equals the number of K+ moving inside the cell.
Polarized
78
The voltage across a plasma membrane that is un-stimulated (polarized). It is caused mainly by differences in intracellular and extracellular ions.
Resting Membrane Potential (RMP)
79
RMP results from the combination of (3)
1. Diffusion of ion down concentration gradient
| 2. Selective permeability of the plasma membrane; 3. The attraction of cations and anions to each other.
80
____+ has the largest influence on RMP
K+
81
RMP for neurons is approximately ____ mV (inside negative)
-70 mV
82
When the RMP is changed so that the inside of the cell become less negative, the membrane is said to be _____.
depolarized
83
______ are openings in large proteins often with subunits whose amino acids chains twist backward and forward across the plasma membrane.
Ion Channels
84
Types of channel include: (4)
a) Chemical-gated (ligand-gated) channels
b) Voltage-gated channel
c) Mechanically-gated channel
d) Non-gated/ Leakage channel
85
Type of Channel
- part of the protein molecule forms a gate that opens or closes in response to certain chemical. The gate opens only when specific chemical binds e.g., neurotransmitter.
Chemical-gated (ligand-gated) channels
86
Type of Channel
| - opens and closes in response to changes in membrane potential
Voltage-gated channel
87
Type of Channel
| - opens and closes when physical action is apply (e.g., when sensory receptor for pressure, touch are deformed)
Mechanically-gated channel
88
Type of Channel
– these channels are always open but channel is selective as to which ion passes through (e.g. K+ channels allow only K+ to pass through.
Non-gated/ Leakage channel
89
When gated ion channels are open the ions diffuse quickly through the gate (down their concentration gradient). The ion flow constitutes an electric current which is called an _______.
impulse or action
90
______ are proteins that active to moving certain substance into or out of cell; they tend to move substance from low concentration to high concentration (i.e., up concentration gradient).
Membrane pumps
91
_______ is an enzyme that hydrolyses ATP (ATP ADP + P + energy to pump).
- This pump, in each cycle of action, moves 3 Na+ from inside the cell to the extracellular fluid and simultaneously, brings 2K+ into the intracellular fluid by using 1 molecule ATP for energy.
- Notice that this pump stabilizes the resting membrane potential by maintain the ion concentration gradient across the membrane.
Na+/K+ pump (Na+/K+ ATP-ase)
92
A rapid voltage change in which a plasma membrane briefly reverses electrical polarity.
ACTION POTENTIAL (AP)
93
All functional body cells generally exhibit a resting membrane potential (RMP) but muscle and nerve cells are able to alter the cross membrane potential by _____
depolarization
94
The shift in potential difference from positive to negative (outside the cell membrane) is called an _______.
action potential (AP.)
95
A state in which the plasma membrane becomes more positive than the resting membrane potential
Depolarization
96
An increase in membrane potential in which the membrane becomes more negative than the resting membrane potential.
Hyperpolarisation
97
Action potential (AP) in neurons has amplitude of about ___ mV and last for 1ms.
110 mV
98
The generation of AP is the result of a stimulus by a _______(e.g., light, heat, electrical energy or mechanical force). The stimulus causes the membrane to become permeable to Na+ leading to depolarization of the membrane. (This is an example of a positive feedback system while the Na+ that crosses the membrane cause more Na+ to enter the cell , until Na+ inside = Na+ outside the cell.) Following depolarization, K+ leaves the cell making the inside less positive, in an effort to restore the RMP.
form of energy
99
Restoration of the RMP is brought about by the outward diffusion of ___+.
K+
100
_____ occurs following repolarisation. K+ diffusion out of the cell dominates repolarisation. Generally, so much K+ diffuse out of the cell that the membrane potential to fall below the RMP, a condition called _______.
Hyperpolarisation
101
Following hyperpolarisation, the Na+/K+ pump resorts the cross membrane ion conc’n. by pumping __+ out __+ into the cell
Na+ out K+ in
102
AP obeys the _____ law. That is, they are not graded responses; they either full-size or absent depending on the stimulus. AP produced by any neuron has a constant size of 110mV and last for 1 ms. amplitude and duration do not vary with frequency of stimulation. If the stimulus depolarizes the neuron to the threshold, the neuron fires to its fullest level. If the threshold is not reached the neuron will not fire.
all-or-none law
103
True or False
| The last potential at the end of a fibre is as strong as the first AP.
True
104
True or False
| AP goes to completion; it cannot be stopped once started.
True
105
A short range change in voltage.
- Occurs when a dendrite is stimulated by stimuli such as heat, light, pressure, pain signal from damaged tissue. Stimulation causes voltage regulated Na+ gates to open and allow Na+ into the plasma membrane of nerve cells. Inflow of Na+ leads to neutralization of negative charges and move the membrane voltage towards zero (i.e., causes depolarization to occur). Sodium only travels a short distance along the plasma membrane from the receptor end to the cell body of neurons.
- gets weaker as it travels to the soma
- vary in strength and can be quickly reverse as K+ leaves intracellular fluid
- can cause depolarization or hyperpolarisation.
LOCAL POTENTIAL
106
Virtually all voltage regulated Na+ and K+ channels are closed at the ____.
resting membrane potential (RMP)
107
II. ____ zones of neurons have many voltage regulated gates (more than the soma of neurons).
Trigger zones
108
III. Local potential that spreads through a membrane to reach the trigger zone can cause voltage regulated gates to open, if the signal is ______.
strong enough
109
IV. If local potential causes membrane voltage to rise to the threshold voltage (~ -55mV) the neuron “____”. If the local potential is < -55 mV the neuron _____ (i.e., all-or-none).
fires; does not fire
110
V.Threshold voltage is reached by means of
| 4
1. Na+ gates opening quickly and let in Na+.
2. K+ gates opening slowly to let K+ out.
3. Influx of Na+ causes other Na+ gates to open (Positive Feedback)
4. Influx of positive ions leads to rapid rise in membrane potential
111
VI. When membrane potential reaches 0 mV, _______ start closing. By the time all gates are closed membrane voltage has climbed to + 35 mV to 50 mV (Peak voltage).
Na+ gates
112
VII. At peak voltage all the K+ gates are open and _____ is occurring. K+ gates stay open longer than Na+ gates.
- So efflux of K+ > influx of Na+.
efflux of K+
113
VIII. _____ causes the membrane potential to move towards zero and the RMP (Repolarisation). But since diffusion of K+ levels is greater than influx of Na+ the plasma membrane becomes more negative than the RMP ( i.e., hyper-polarization occurs). By the end of hyper-polarization K+ gates are closed and the cell will respond to a new stimuli.
Diffusion of K+
114
Peak voltage
+ 35 mV to 50 mV
115
During an action potential and a few milliseconds after, the neuron will not respond to stimuli. This period is called the ________.
- This period refers only to a small patch of membrane where the AP has already begun, not to the entire neuron.
refractory period
116
Action potential follows a lit fuse or _____.
domino effect
117
• Na + open in a region, Na+ influx occurs then the Na+ gates close (_______occurs)
depolarization
118
Depolarization in one region causes depolarization in the ____ region and AP spreads along the axon to the axon terminal.
adjacent region
119
• AP does not move backwards because of _____________.
refractory period in previously depolarized region
120
- Signal is slow (~ 2m/s)
| - Signal does not grow weaker as it spreads _____; signal strength stays the same.
forward
121
_____ blocks the movement of ions into the neuron and voltage gates are few in the internodes’ regions.
Myelin
122
Most voltage gates are located in the _____.
Nodes of Ranvier
123
Na+ enter at the nodes causes an AP and diffuse along the _____.
axolemma
124
Myelin weakens signal strength so the sign can only travel ___mm before it become too weak to affect an adjacent node.
1mm
125
When sign from one node reaches an adjacent node it opens Na+ voltage gate at that node and ____ occur.
Na+ influx
126
At each node influx of Na+ occurs followed by an ____, hence signal appear to jump from node to node (SALTATORY CONDUCTION).
AP
127
The propagation of nerve signal that seems to jump from one node to another.
Saltatory conduction
128
Conduction velocity up to ____m/s.
120m/s
129
A ____ is a bundle of nerve fibres (axons) wrapped in fibrous connective tissue.
Nerve
130
Nerves originate from the CNS and travel through ___ of the skull and _____. They carry signal to and the CNS to other parts of the body.
foramina; vertebral column
131
____ nerve refers to the fact that the nerve contains both afferent and efferent nerve fibres innervating a number of different muscles and glands.
Mixed nerve
132
Each nerve is wrapped in delicate fibrous connective tissue called ____ and groups of nerve fibres are held together in bundles called _____. The bundles of nerve fibres are all enclosed in an outer fibrous covering called _____.
endoneurium; perineurium; epineurium
133
Speed of conduction on a nerve fibre depends on (2)
1) diameter size and 2) myelination:
134
Since signal conduction occurs at the surface (rather than deep within the axon), the larger the diameter of the fibre the ____ the conduction of the action potential. This implies that the smaller the fibre the ___ the conduction.
Faster; Slower
135
True or False
| Myelinated fibres conduct much faster and farther those unmyelinated fibres
True
136
Conduction speed in a fibre of diameter 2-4 micrometers, unmyelinated:
0.5-2 m/s
137
Conduction speed in a fibre of diameter 2-4 micrometers, myelinated:
3-15m/s
138
Conduction speed in large diameter fibres (up to20 micrometres) is as fast as _____m/s.
120m/s
139
____ fibres used where speed is important, e.g. signal to muscles, sensory input from vision and balance.
Fast fibres
140
____ fibres employed in processing information in which rapid response not required, e.g., secreting stomach acid, dilating the pupil.
Slow fibres
141
At the axonal terminals AP depolarizes the axolemma to cause Ca++ to enter and binds to ____.
vesicles
142
The vesicles with Ca++ migrate to the membrane, binds and empty their content (neurotransmitter) in the _____.
gap
143
Four categories of neurotransmitters are released by neurons: (4)
1. Acetylcholine (Ach)
2. Amino Acids
3. Monoamines
4. Neuropeptides
144
There are two types of synapse:
1. Excitatory synapse and EPSP
| 2. Inhibitory synapse and IPSP
145
At _______ synapse, neurotransmitter binding causes depolarization of the postsynaptic membrane. Binding of the neurotransmitter to chemical gates causes the opening of Na+ and K+ gates and the ions to flow in opposite direction. The net effect is membrane depolarization. If enough neurotransmitter binds to the membrane, so that the membrane threshold voltage is reached, then the neuron fires. Otherwise, it does not fire. Since post-synaptic membrane cannot generate AP (because the membrane have not voltage gate) only a local graded depolarization event called excitatory postsynaptic potential (EPSP) occurs. The function of an EPSP is to help trigger action potential at the axon hillock of the post-synaptic neuron.
If the current that reaches the axon hillock is strong enough to depolarize the axon to its threshold voltage, then voltage gates on the axon open and the neuron fires. Examples of excitatory neurotransmitter are: Ach, NE and E.
Excitatory synapse and EPSP
146
At ______ synapse, neurotransmitter binding inhibits the postsynaptic neurons ability to generate action potential. Most inhibitory neurotransmitters cause Cl- to move into and K+ to move out of the cell thus creates a situation of hyperpolarisation of the membrane. (These neurotransmitters do not affect movement of Na+.) The increase in membrane potential reaches the axon hillock and raises the voltage required to cause the axon to fire. Since a larger than normal depolarization current is required to generate an action potential these synapses are called inhibitory postsynaptic potentials (IPSP).
Example inhibitory neurotransmitters are: GABA and Glycine
Inhibitory synapse and IPSP
147
Neurotransmitter binds to post-synaptic membrane for only a short time (____m). When one molecule leaves another takes its place until all the neurotransmitter in the gap disappears.
(1 m)
148
Neurotransmitter can diffuse into the extracellular fluid and taken up by _____.
astrocytes
149
Neurotransmitter can be re-uptake into pre-synaptic fibre and re-used. Some of the reuptake neurotransmitter can be broken down by ___________.
monoamine oxide (MAO)
150
Neuro- transmitter can be broken down by ______ such as catechol-O-methyltransferase (COMT) and acetylcholinesterase (Ach-ase) and the by- products taken up into the blood.
gap enzymes
