Chapter 12 Flashcards
1
Q
Nerve
A
A bundle of hundreds to thousands of axons plus associated connective tissue and blood vessels that lies outside the brain and spinal cord
2
Q
How many pairs of cranial nerves emerge from the brain?
A
Twelve
3
Q
How many pairs of spinal nerves emerge from the spinal cord?
A
31
4
Q
Sensory receptor
A
Structure of the nervous system that monitors changes in the external or internal environment
5
Q
What divisions is the PNS system divided into
A
Sensory division and motor division
6
Q
Sensory or afferent division
A
Conveys input into the CNS from sensory receptors in the body provides the CNS with sensory information about the somatic senses and special senses
7
Q
Motor or Efferent division
A
Conveys output from the CNS two effectors further subdivided into somatic nervous system and autonomic nervous system
8
Q
Somatic nervous system
A
Conveys output from the CNS to skeletal muscles only because it can be consciously controlled the action of this part of the PNS is voluntary
9
Q
Autonomic nervous system
A
Conveys output from the CNS to smooth muscle cardiac muscle and glands not normally under conscious control the action of the ANS is involuntary
10
Q
What are the two main branches of the autonomic nervous system?
A
Sympathetic nervous system and parasympathetic nervous system And enteric nervous system
11
Q
Parasympathetic nervous system
A
Rest and digest activities
12
Q
Sympathetic nervous system
A
Supports exercise or emergency action “fight or flight” response is
13
Q
Enteric nervous system
A
Confined to the wall of the G.I. tract helps regulate the activity of the smooth muscles and glands of the G.I. tract
14
Q
What are the three basic functions of the nervous system?
A
- Sensory
- integrative
- motor
15
Q
Sensory function
A
Sensory receptors detect internal stimuli examples blood pressure or external stimuli the information is not carried into the brain and spinal cord
16
Q
Integrative function
A
The nervous system processes sensory information by analyzing it and making decisions for appropriate responses an activity known as integration
17
Q
Motor function
A
After sensory information is integrated if the nervous system may all it an appropriate motor response by activating effectors (muscle and glands) through cranial and spinal nerves
18
Q
Electrical excitability
A
The ability to respond to a stimulus and convert it into an action potential
19
Q
Action potential
A
An electrical signal that propagates along the surface of the membrane of a neuron
20
Q
What’s the cell body of the neuron known as
A
Perikaryon or soma
21
Q
What’s the term for free ribosomes in clusters of rough endoplasmic reticulum of the neuron?
A
Nissl bodies
22
Q
Neurofibrils
A
Composed of bundles of intermediate filaments that provide the cell shape and support
23
Q
Microtubules
A
System moving materials between the cell body and axon
24
Q
Lipofuscin
A
A pigment that occurs as clumps of yellowish brown granules in the cytoplasm a product of neuronal lysosome is that accumulates as a neuron ages
25
Ganglion
Collection of neuron cell bodies outside the CNS
26
Nerve fiber
General term for any neuronal process that emerges from the cell body of a neuron most have two kinds of processes dendrites and axons
27
Dendrites
Receiving or input portions of a neuron contain numerous receptor sites for binding chemical messengers from other cells usually short tapering in highly branched
28
Axon
Propagates nerve impulses towards another neuron, a muscle fibre, or a gland cell. an axon is a long, thin, cylindrical projection that often joins to the cell body at a cone shaped elevation called the axon hillock
29
Axon hillock
Cone shaped elevation on the axon
30
Initial segment
Part of the axon closest to the axon hillock
31
Trigger zone
Junction of the axon hillock and initial segment where nerve impulses arise
32
Axoplasm
Cytoplasm of axon
33
Axolemma
Plasma membrane of the neuron
34
Axon collaterals
Side branches on length of an axon
35
Axon terminal
Branch off the axon end
36
Synapse
Site of communication between two Neurons or between a neuron and an effectorcell
37
Synaptic bulbs and varicosities
The swelling at the tips of the axon terminal which contain many tiny sacs called synaptic vesicles that store neurotransmitters
38
What stores neurotransmitters?
Synaptic vesicles
39
Slow axinal transport
Convey’s axoplasm in One Direction only from the cell body toward the axon terminals supplies new exoplasm to developing or regenerating axons and replenishes exoplasm and growing and mature axons
40
Fast axonal transport
Capable of moving materials a distance of 200 to 400 mm per day uses proteins that function as motors to move materials along the surfaces of microtubules of the neuron cytoskeleton can move material in both directions away from and towards the cell body
41
Fast axonal transport - Anterograde
Occurs in a forward direction moves organelles in synaptic vesicles from the cell body to the axon terminals
42
Fast axonal transport - retrograde
Occurs backward direction moves membrane vessicles and other cellular material from the axon terminals to the cell body to be degraded or recycled as well as substances that enter the neuron at the axon terminals
43
Multipolar neurons
Have several dendrites in one axon
44
Bipolar neurons
One main dendrite and one axon
45
Unipolar neurons
Have den droids and one axon that are fused together to form a continuous process that emerges from the cell body also called pseudo unipolar neurons
46
Purkinje cells
Found in the cerebellum
47
Pyramidal cells
Found in the cerebral cortex of the brain
48
Sensory neurons or afferent neurons
Contain sensory receptors at their distal ends or are located just after sensory receptors the sensory neuron forms an action potential in its axon then the action potential is conveyed into the CNS through cranial or spinal nerves; most are unipolar
49
Motor neurons or efferent neurons
Convey action potentials away from the CNS to effectors in the periphery through cranial or spinal nerves; most are multi polar in structure
50
Interneurons or association neurons
Mainly located within the CNS between sensory and motor neurons interneurons integrate incoming sensory information from sensory neurons and then elicit a motor response by activating the appropriate motor neuron; most are multi polar and structure
51
Neuroglia
 “Glue” that holds nervous tissue together, smaller than neurons, do not propagate or generate action potentials, are able to multiply and divide
52
What are the CNS neuroglia?
Astrocytes, oligodendrocytes, microglia, and ependymal cells
53
Peripheral nervous system neuroglia?
Schwann cells and satellite cells
54
Astrocytes
Star shaped cells have many processes and are the largest and most numerous of the neuroglia two types protoplasmic and fibrous
55
Protoplasmic astrocytes
How many short branching processes are found in gray matter
56
Fibrous astrocytes
located mainly in white matter
57
What are the functions of astrocytes?
1. Contain microfilaments like give them strength which enables them to support Neurons
2. Processes of astrocytes wrapped around blood capillaries isolate neurons of the CNS from various potential harmful substances in blood by secreting chemicals that maintain unique selective permeability, The endothelial cells create a blood brain barrier
3. In embryo astrocytes agree chemicals that appear to regulate growth migration in interconnection of neurons in the brain
4. Help maintain appropriate chemical environment for the generation of nerve impulses
5. Play a role in learning and memory by influencing the formation of neural synapses
58
Oligodendrocytes
Resemble astracites but are smaller in contain fewer processes these processes form and maintain the myelin sheath around CNS axons. Can myelinate several axons
59
Myelin sheath
Multilayered lipid and protein covering around some axons that insulates them and increases the speed of nerve impulse conduction
60
Microglial cells or microglia
Small cells with slender processes that give off numerous spine like projections function as phagocytes
61
Ependymal cells
Cuboidal to calmer cells arranged in a single layer that possesses microvilli and cilia these cells line the ventricles of the brain and central canal of the spinal cord. functionally produce, possibly monitor, and assist in the circulation of cerebral spinal fluid and form the blood-cerebrospinal fluid barrier
62
Schwann cells
Located in the PNS
Myelinates only a single axon
But can enclose as many as 20 or more unmyelinated axons. Participate in axon regeneration
63
Satellite cells
Flat cells surround the cell bodies of neurons of PNS ganglia, regulate the exchanges of materials between neuronal’s cell bodies and interstitial fluid
64
Neurolemma
Outer nucleated cytoplasmic layer of the Schwan cell which encloses the myelin sheath found only around axons in the PNS, aids regeneration by forming a regeneration tube that guides stimulates regrowth of the axon
65
Nodes of Ranvier
Gaps in the myelin sheath each Schwan cell wraps one axon segment between two nodes
66
Tract
Bundle of axons that is located in the CNS that interconnect neurons in the spinal cord and brain
67
White matter
Composed primarily of myelinated axons
68
Gray matter
Contains neuronal cell bodies, dendrites, unmyelinated axons, axon terminals, and neuroglia. The nissl bodies impart a gray colour and there’s little to no myelin in these areas
69
What are the two types of electrical signals used to communicate between neurons?
1. Graded potential’s
2. Action potentials
70
Grated potentials
Used for short distance communication
71
Action potentials
communication over long distances within the body‘s
72
What are the four types of ion channels?
1. Leaky channels
2. Ligand- gated channels
3. Mechanically-gated channels
4. Voltage-gated channels
73
Leak channels
Randomly alternate between opening clothes positions
74
Ligand gated channel
Opens and closes in response to the binding of a ligand stimulus wide variety of chemical ligands including neurotransmitters, hormones, and particular ions
75
Mechanically gated channel
Opens or closes in response to mechanical stimulation in the form of vibration, touch, pressure, or tissue stretching; the force distorts the channel from its resting position opening the gate
76
Voltage gated channel
Opens in response to a change in membrane potential; voltage gated channels participate in the generation and conduction of action potential’s in the axons of all types of neurons
77
why does resting membrane potential exist?
Because of a small buildup of negative ions in the cytosol along the inside of the membrane and an equal buildup of positive ions in the extracellular fluid along outside surface of the membrane
78
What’s the typical resting membrane inside a neuron?
-70
79
Polarized
So the exhibit of membrane potential
80
What are the three major factors that arise from the resting membrane potential?
1. Unequal distribution of ions in the ECF and cytosal
2. Inability of most anions to leave the cell
3. Electrogenic nature of the Na + -K + ATPases
81
Graded potential
Small deviation from the resting membrane potential that makes the membrane either more polarized or less polarized
82
Hyperpolarizing graded potential
When the response makes a membrane more polarized (inside more negative)
83
Depolarizing graded potential
And the response makes the membrane less polarized (inside less negative)
84
Decremental conduction
 The flow of current is localized and spreads to adjacent regions along the plasma membrane in either direction from the stimulus source for a short distance and then gradually dies out as the charges are lost across the membrane through leak channels
85
Summation
Process by which graded potentials add together
86
Action potential or impulse
Rapidly occurring events that decrease and reverse the membrane potential and then eventually restore it to resting state. Two phases depolarizing phase and re-polarizing phase
87
Depolarizing phase
The negative membrane potential becomes less negative reaches zero and then becomes positive
88
Re-polarizing phase
The membrane potential is restored to the resting state of -70 MV following three polarizing pay is there may be an after hyperpolarizing phase
89
After-Hyperpolarizing phase
The membrane potential temporary becomes more negative than the resting level
90
Threshold
An action potential occurs in the membrane of an axon when depolarization reaches a certain level called threshold
91
Subthreshold stimulus
An action potential will not occur in response to this it’s a week deep polarization they cannot bring the membrane potential to threshold
92
Super threshold stimulus
Strong enough to deepalize the membrane above threshold has the same amplitude as an action potential caused by a threshold stimulus 
93
What are the two separate gates on a voltage gated Na+?
Activation gate and inactivation gate
94
Refractory period
The period of time after an action potential begins during which an excitable cell cannot generate another action potential in response to a normal threshold stimulus
95
Absolute refractory period
Even a very strong stimulus cannot initiate a second action potential
96
Relative refractory period
The period of time during which is second action potential can be initiated but only by larger than normal stimulus
97
Propagation
When an action potential keeps it strength as it spreads along the membrane
98
What are the two consequences of flow of current across the membrane only at the nodes of Ranvier?
1. Action potentials appear to leap from node to node so it travels much faster
2. opening a smaller number of channels only at the nodes is more energy efficient, using less ATP
99
What are factors that affect the speed of propagation?
1. Amount of myelination
2. Axon diameter
3. Temperature
100
What are the three major classifications of nerve fibers?
1. A fibres
2. B fibres
3. C fibers
101
A fibers
- Largest diameter axons
- have a brief absolute refractory period
- conduct nerve impulses
- the axons of sensory neurons that propagate impulses associated with touch pressure position of joints and some thermal and painless sensations
- axons of motor neurons
102
B fibers
- Myelinated and exhibit saltatory conduction at speeds up to 15 m/s -somewhat longer absolute refractory period
- conduct sensory nerve impulses from the viscera to the brain and spinal cord
- constitute all of the axons of the autonomic motor neurons that extends from the brain and spinal chord to the ANS
103
C fibers
- Smallest diameter axons all on myelinated nerve impulses -propagation along to C fibre ranges from .5 to 2 m/s
- exhibit the longest absolute refractory period conduct some sensory impulses for pain, touch, pressure, heat, and cold from the skin and painless impulses from the viscera
104
Ionotropic receptor
Type of neurotransmitter receptor that contains a neurotransmitter binding site and an ion channel they are components of the same protein
105
Metabotropic receptor
A type of neurotransmitter receptor that contains the neurotransmitter binding site but lacks an ion channel is part of instruction but is coupled to a separate ion channel by type of membrane proteins called a g protein they are not part of the same protein
106
Inhibitory postsynaptic potential
Hyperpolarizing postsynaptic potential
107
Excitatory postsynaptic potential
Depolarizing postsynaptic potential
108
How is the Nero transmitter removed from the synaptic cleft?
1. Diffusion
2. Enzymatic degradation
3. Uptake by cells
109
Spatial summation
Summation of postsynaptic potential’s in response to stimuli that occur at different locations in the membrane of a postsynaptic cell at the same time
110
What determines the effect on the postsynaptic neuron?
The sum of all excitatory and inhibitory effects
