nervous system Flashcards
(145 cards)
1
Q
Includes all neural tissue in the body (brain, spinal cord, and track ways that the nerves are going to pass along)
A
Nervous System
2
Q
Neural tissue contains two kinds of cells..
A
- Neurons “nerve cells”
- Neuroglia (glial cells)
3
Q
-Cells that send and receive signals
-performs All communication, information processing, and control functions of the nervous system
(conduction of electrical signal, which is how body functions)
cellular level
A
Neurons
4
Q
-Cells that support, maintain and protect neurons
-cleans up debri
-Half the volume of the nervous system
-Many types of ____ in CNS and PNS
-preserve, Physical and biochemical structure of neural tissue
*a ton, for every neuron theres 100 glial cellls
-are essential to:
Survival and function of neurons
(makes up tissue itself)
A
Neuroglia (glial cells)
5
Q
-Brain and spinal cord (CNS)
-Sensory receptors of sense organs (eyes, ears, tongue etc.) “that are clustered or concentrated in diff. areas”
- nerves (bundls of axon frm neuron connect evryw)
connect nervous system w/ other systes
A
Organs of the Nervous System
6
Q
what are these
- Central nervous system (CNS)
- Peripheral nervous system (PNS)
A
Anatomical Divisions of the Nervous System
7
Q
- Consists of the spinal cord and brain, major nerves associated w/ cns
- Contains neural tissue, connective tissues, and blood vessels
- analyze/ makes responses
- is an anatomicical division
A
The Central Nervous System (CNS)
8
Q
- Sensory(upstream) data coming from everywhere, from inside and outside body
- Motor(dwnstream) commands control activities of peripheral organs (e.g., skeletal muscles)
- Higher functions of brain intelligence, memory, learning, emotion
- mainly have info. processing/ COORDINATION, bringing info back & forth
- has neural connections allowing you to coordinate
A
Functions of the Central Nervous System are to process and coordinate…
9
Q
- Includes all neural tissue outside the CNS
- Information moving back n forth
- is an anatomical division
A
The Peripheral Nervous System (PNS)
10
Q
- Deliver sensory information upstream to the CNS
- Carry motor commands downstream to peripheral tissues (glands, muscles, organs and overall systems
A
Functions of The Peripheral Nervous System (PNS)
11
Q
- Bundles of axons from neurons that connect everywhere with connective tissues and blood vessels that make up nerves
- axons from diff. neurons going in the same direction until the travel together
- Carry sensory information upstream and motor commands downstream
- connect the nervous system with other systems
A
Nerves (also called peripheral nerves)
12
Q
connect to brain, to spinal cord, carry sensory info
A
Cranial nerves
13
Q
attach to spinal cord, to peripheral nerves, carry sensory info
A
Spinal nerves
14
Q
- Carries sensory information
- From PNS sensory receptors to CNS
- bringing too you
- Ex) if I touch this table top, the sensory division is taking info about texture, temp, and other info from fingertips upstream….
A
Afferent division
15
Q
- Carries motor commands
- From CNS to PNS muscles and glands
- carries away
- motor command division downstream
- unconsious
- motor, downstream
A
Efferent division
16
Q
- Recieve info, Detect changes or respond to stimuli
- Neurons and specialized cells
- Complex sensory organs/glands (e.g., eyes, ears)
- (negative feeb back/ positive feedback
A
Receptors
17
Q
Respond to efferent signals
Cells and organs
do stuff, cause effect
muscle causing change, “touch somthin hot, pull back”
A
Effectors
18
Q
- body nervous system
- Controls voluntary and involuntary (reflexes) muscle skeletal contractions
- The efferent division
A
Somatic nervous system (SNS)
19
Q
- Controls subconscious actions, (involuntary) contractions of smooth muscle and cardiac muscle, and glandular secretions
- Sympathetic division has a stimulating effect (hyping up, big effects on brain, increasing heart rate, anaxiety level)
- Parasympathetic division has a relaxing effect (hyping dwn, low heart rates, rest and digest )
- The efferent division
A
Autonomic nervous system (ANS)
20
Q
Large nucleus and nucleolus Perikaryon (cytoplasm) Mitochondria (produce ATP) RER and ribosomes (produce neurotransmitters) soma
A
Cell body
21
Q
- Common in the CNS
- Cell body (soma)
- Short, branched dendrites
- Long, single axon
A
The multipolar neuron
22
Q
Dense areas of Rough ER and ribosomes
Make neural tissue appear gray (gray matter)
A
Nissl bodies
23
Q
bundles of neurofilaments that provide support for dendrites and axon
A
Neurofibrils
24
Q
Highly branched spines Many fine processes Receive information from other neurons 80–90% of neuron surface area tree branches, recieving multiple info, sends to axon
A
Dendrites
25
Is long
| Carries electrical signal (action potential) to target structure is critical to function
The axon
26
Cytoplasm of axon
| Contains neurofibrils, neurotubules, enzymes, organelles
Axoplasm
27
Specialized cell membrane
| Covers the axoplasm
Axolemma
28
Thick section of cell body
| Attaches to initial segment
Axon hillock
29
Attaches to axon hillock
Initial segment
30
Branches of a single axon
Collaterals
31
Fine extensions of distal axon
telodendria
32
tips of telodendria
Synaptic terminals
33
Area where a neuron communicates with another cell
synapse
34
Neuron that sends message
Presynaptic cell
35
Cell that receives message
Postsynaptic cell
36
The small gap that separates the presynaptic membrane and the postsynaptic membrane
The synaptic cleft
37
Is expanded area of axon of presynaptic neuron
| Contains synaptic vesicles of neurotransmitters
The synaptic terminal
38
```
1-Are chemical messengers
2-Are released at presynaptic membrane
3-Affect receptors of postsynaptic membrane
4-Are broken down by enzymes
5-Are reassembled at synaptic terminal
(cycle)
```
Neurotransmitters
39
neurotubules within the axon
Transport raw materials
Between cell body and synaptic terminal
Powered by mitochondria, kinesin, and dynein
Axoplasmic transport
40
Found in brain and sense organs
Small
All cell processes look alike
Anaxonic neurons
41
Found in special sensory organs (sight, smell, hearing)
Are small
One dendrite, one axon
Bipolar neurons
42
```
Found in sensory neurons of PNS
Also called pseudounipolar neurons
Have very long axons
Fused dendrites and axon
Cell body to one side
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Unipolar neurons
43
Common in the CNS
Include all skeletal muscle motor neurons
Have very long axons
Multiple dendrites, one axon
Multipolar neurons
44
Afferent neurons of PNS
Sensory neurons
45
Association neurons
Interneurons
46
Efferent neurons of PNS
- are voluntary
- travels downhill from the CNS to the muscles
Motor neurons
47
- travels upstream from the apanages and the nerve endings up into the CNS
- Monitor internal environment (visceral sensory -neurons)
- Monitor effects of external environment (somatic sensory neurons)
Functions of Sensory Neurons
48
Unipolar
Cell bodies grouped in sensory ganglia
Processes (afferent fibers) extend from sensory receptors to CNS
Structures of Sensory Neurons
49
- Monitor internal systems (digestive, respiratory, cardiovascular, urinary, reproductive)
- Internal senses (taste, deep pressure, pain)
Interoceptors
50
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External senses (touch, temperature, pressure)
Distance senses (sight, smell, hearing)
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Exteroceptors
51
Monitor position and movement (skeletal muscles and joints)
Proprioceptors
52
Two major efferent systems
Somatic nervous system (SNS)
| Autonomic (visceral) nervous system (ANS)
53
Includes all ____ motor neurons that innervate skeletal muscles
Somatic nervous system (SNS)
54
Visceral motor neurons innervate all other peripheral effectors
Smooth muscle, cardiac muscle, glands, adipose tissue
Autonomic (visceral) nervous system (ANS)
55
Signals from CNS motor neurons to visceral effectors pass synapses at autonomic ganglia dividing axons into:
Preganglionic fibers
| Postganglionic fibers
56
```
Most are located in brain, spinal cord, and autonomic ganglia
Between sensory and motor neurons
Are responsible for:
Distribution of sensory information
Coordination of motor activity
Are involved in higher functions
Memory, planning, learning
```
Interneurons
57
Cells with highly branched processes; contact neuroglia directly
Ependymal cells
58
Large cell bodies with many processes
Astrocytes
59
Smaller cell bodies with fewer processes
Oligodendrocytes
60
Smallest and least numerous neuroglia with many fine-branched processes
Microglia
61
Form epithelium called ependyma
Line central canal of spinal cord and ventricles of brain
Secrete cerebrospinal fluid (CSF)
Have cilia or microvilli that circulate CSF
Monitor CSF
Contain stem cells for repair
Ependymal cells
62
Maintain blood–brain barrier (isolates CNS)
Create three-dimensional framework for CNS
Repair damaged neural tissue
Guide neuron development
Control interstitial environment
Astrocytes
63
Increases speed of action potentials
___ insulates myelinated axons
Makes nerves appear whit
Myelination
64
myelinated segments of axon
Internodes
65
Gaps between internodes
| Where axons may branch
Nodes (also called nodes of Ranvier)
66
Regions of CNS with many myelinated nerves
White matter
| Myelination
67
Unmyelinated areas of CNS
Gray matter
| Myelination
68
Migrate through neural tissue
| Clean up cellular debris, waste products, and pathogens
Microglia
69
Masses of neuron cell bodies
Surrounded by neuroglia
Found in the PNS
Ganglia
70
Also called amphicytes
Surround ganglia
Regulate environment around neuron
Satellite cells
71
Also called neurilemma cells
Form myelin sheath (neurilemma) around peripheral axons
One Schwann cell sheaths one segment of axon
Many Schwann cells sheath entire axon
Schwann cells
72
Axon distal to injury degenerates
Wallerian degeneration
73
Form path for new growth
| Wrap new axon in myelin
Schwann cells
74
Limited by chemicals released by astrocytes that:
Block growth
| Produce scar tissue
75
Neurofilaments and neurotubules in place of microfilaments and microtubules (neurofibrils)
Cytoskeleton
76
All plasma (cell) membranes produce electrical signals by
ion movements
77
is particularly important to neurons
Transmembrane potential
78
1. Resting potential
2. Graded potential
3. Action potential
4. Synaptic activity
5. Information processing
Five Main Membrane Processes in Neural Activities
79
Response (integration of stimuli) of postsynaptic cell
Information processing
80
- Releases neurotransmitters at presynaptic membrane
| - Produces graded potentials in postsynaptic membrane
Synaptic activity
81
- Is an electrical impulse
- Produced by graded potential
- Propagates along surface of axon to synapse
Action potential
82
- Temporary, localized change in resting potential
- Caused by stimulus
- Also called local potentials
- Changes in transmembrane potential, That cannot spread far from site of stimulation
- Any stimulus that opens a gated channel
Graded potential
83
-The transmembrane potential of resting cell
Resting potential
84
Three important concepts:
-The extracellular fluid (ECF) and intracellular fluid (cytosol) differ greatly in ionic composition
Concentration gradient of ions (Na+, K+)
-Cells have selectively permeable membranes
-Membrane permeability varies by ion
The Transmembrane Potential
85
Concentration gradient of ions (Na+, K+)
Chemical gradients
| Na+, K+
86
Separates charges of positive and negative ions
| Result in potential difference
Electrical gradients
87
Movement of charges to eliminate potential difference
Electrical current
88
The amount of current a membrane restricts
Resistance
89
-The transmembrane potential at which there is no net movement of a particular ion across the cell membrane
Examples:
K+ = –90 mV
Na+ = +66 mV
Equilibrium Potential
90
- Is powered by ATP
- Carries 3 Na+ out and 2 K+ in
- Balances passive forces of diffusion
- Maintains resting potential (–70 mV)
Sodium–potassium ATPase (exchange pump)
91
- In response to temporary changes in membrane permeability
| - Resulting from opening or closing specific membrane channels
Transmembrane potential rises or falls
92
- Are always open
| - Permeability changes with conditions
Passive Channels (Leak Channels)
93
- Open and close in response to stimuli
| - At resting potential, most gated channels are closed
Active Channels (Gated Channels)
94
1. Closed, but capable of opening
2. Open (activated)
3. Closed, not capable of opening (inactivated)
Three States of Gated Channels
95
1. Chemically gated channels
2. Voltage-gated channels
3. Mechanically gated channels
Three Classes of Gated Channels
96
- Open in presence of specific chemicals (e.g., ACh) at a binding site
- Found on neuron cell body and dendrites
Chemically Gated Channels
97
Synapse between neuron and muscle
Neuromuscular junction
98
Synapse between neuron and gland
Neuroglandular junction
99
-(Na+, K+) The sum of chemical and electrical forces
-Acting on the ion across a plasma membrane
A form of potential energy
Electrochemical Gradient
100
- Respond to changes in transmembrane potential
- Have activation gates (open) and inactivation gates (close)
- Characteristic of excitable membrane
- Found in neural axons, skeletal muscle sarcolemma, cardiac muscle
Voltage-gated Channels
101
- Respond to membrane distortion
| - Found in sensory receptors (touch, pressure, vibration)
Mechanically Gated Channels
102
- Opening sodium channel produces graded potential
- Resting membrane exposed to chemical
- Sodium channel opens
- Sodium ions enter the cell
- Transmembrane potential rises
- Depolarization occurs
The resting state
103
- A shift in transmembrane potential toward 0 mV
- Movement of Na+ through channel
- Produces local current
- Depolarizes nearby plasma membrane (graded potential)
- Change in potential is proportional to stimulus
Depolarization
104
-When the stimulus is removed, transmembrane potential returns to normal
Repolarization
105
- Increasing the negativity of the resting potential
- Result of opening a potassium channel
- Opposite effect of opening a sodium channel
- Positive ions move out, not into cell
Hyperpolarization
106
- Propagated changes in transmembrane potential
- Affect an entire excitable membrane
- Link graded potentials at cell body with motor end plate actions
Action Potentials
107
A graded depolarization of axon hillock large enough (10 to 15 mV) to change resting potential (–70 mV) to threshold level of voltage-gated sodium channels (–60 to –55 mV)
Initial stimulus
108
- If a stimulus exceeds threshold amount
- The action potential is the same
- No matter how large the stimulus
- Action potential is either triggered or not
All-or-none principle
109
Step 1: Depolarization to threshold
Step 2: Activation of Na channels
Step 3: Inactivation of Na channels and activation of K channels
Step 4: Return to normal permeability
Four Steps in the Generation of Action Potentials
110
- The time period
- From beginning of action potential
- To return to resting state
- During which membrane will not respond normally to additional stimuli
The Refractory Period
111
- Sodium channels open or inactivated
| - No action potential possible
Absolute Refractory Period
112
- Membrane potential almost normal
| - Very large stimulus can initiate action potential
Relative Refractory Period
113
Moves action potentials generated in axon hillock
| Along entire length of axon
Propagation
114
- Continuous propagation (unmyelinated axons)
| - Saltatory propagation (myelinated axons)
Two methods of propagating action potentials
115
- Action potential along myelinated axon
- Faster and uses less energy than continuous propagation
- Myelin insulates axon, prevents continuous propagation
- Local current “jumps” from node to node
- Depolarization occurs only at nodes
Saltatory Propagation
116
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Type A fibers
Type B fibers
Type C fibers
These groups are classified by:
Diameter
Myelination
Speed of action potentials
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Three Groups of Axons
117
- Myelinated
- Large diameter
- High speed (140 m/sec)
- Carry rapid information to/from CNS
- For example, position, balance, touch, and motor impulses
Type A Fibers
118
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Myelinated
Medium diameter
Medium speed (18 m/sec)
Carry intermediate signals
For example, sensory information, peripheral effectors
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Type B Fibers
119
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Unmyelinated
Small diameter
Slow speed (1 m/sec)
Carry slower information
For example, involuntary muscle, gland controls
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Type C Fibers
120
Action potentials (nerve impulses)
Are transmitted from presynaptic neuron
To postsynaptic neuron (or other postsynaptic cell)
Across a synapse
Synaptic Activity
121
```
(0.2–0.5 msec)
occurs between:
Arrival of action potential at synaptic terminal
And effect on postsynaptic membrane
Fewer synapses mean faster response
Reflexes may involve only one synapse
```
Synaptic Delay
122
Direct physical contact between cells
Are locked together at gap junctions (connexons)
Allow ions to pass between cells
Produce continuous local current and action potential propagation
Are found in areas of brain, eye, ciliary ganglia
Electrical Synapses
123
-Are found in most synapses between neurons and all -synapses between neurons and other cells
-Cells not in direct contact
-Action potential may or may not be propagated to postsynaptic cell, depending on:
-Amount of neurotransmitter released
-Sensitivity of postsynaptic cell
Signal transmitted across a gap by chemical neurotransmitters
Chemical Synapses
124
Cause depolarization of postsynaptic membranes
| Promote action potentials
Excitatory neurotransmitters
125
Cause hyperpolarization of postsynaptic membranes
| Suppress action potentials
Inhibitory neurotransmitters
126
Membrane permeability to Na+ and K+ determines
transmembrane potential
127
They are either passive or active
Sodium and Potassium Channels
128
- Occurs when neurotransmitter cannot recycle fast enough to meet demands of intense stimuli
- Synapse inactive until Acetylcholine is replenished
Synaptic Fatigue
129
- The synaptic terminal releases a neurotransmitter that binds to the postsynaptic plasma membrane
- Produces temporary, localized change in permeability or function of postsynaptic cell
- Changes affect cell, depending on nature and number of stimulated receptors
Chemical Synapse
130
- Affect nervous system by stimulating receptors that respond to neurotransmitters
- Can have complex effects on perception, motor control, and emotional states
many drugs
131
-Other chemicals released by synaptic terminals
-Similar in function to neurotransmitters
-Characteristics of neuromodulators
-Effects are long term, slow to appear
-Responses involve multiple steps, intermediary compounds
Affect presynaptic membrane, postsynaptic membrane, or both
Released alone or with a neurotransmitter
Neuromodulators
132
Neuromodulators that bind to receptors and activate enzymes
Neuropeptides
133
Neuromodulators in the CNS
Bind to the same receptors as opium or morphine
Relieve pain
Opioids
134
Endorphins
Enkephalins
Endomorphins
Dynorphins
four classes of Opioids
135
- At the simplest level in individual neurons
- Many dendrites receive neurotransmitter messages simultaneously
- Some excitatory, some inhibitory
- Net effect on axon hillock determines if action potential is produced
Information Processing
136
Graded depolarization of postsynaptic membrane
Excitatory postsynaptic potential (EPSP
137
Graded hyperpolarization of postsynaptic membrane
Inhibitory postsynaptic potential (IPSP)
138
A neuron that receives many IPSPs
Is ____ from producing an action potential
Because the stimulation needed to reach threshold is increased
Inhibition/ inhibited
139
To trigger an action potential
One EPSP is not enough
EPSPs (and IPSPs) combine through summation
summation
140
Multiple times
| Rapid, repeated stimuli at one synapse
Temporal Summation
141
Multiple locations
| Many stimuli, arrive at multiple synapses
Spatial Summation
142
A neuron becomes ______
As EPSPs accumulate
Raising transmembrane potential closer to threshold
Until a small stimulus can trigger action potential
facilitated/Facilitation
143
Can change membrane sensitivity to neurotransmitters
| Shifting balance between EPSPs and IPSPs
Neuromodulators and hormones
144
Action of an axoaxonic synapse at a synaptic terminal that decreases the neurotransmitter released by presynaptic membrane
Presynaptic inhibition
145
Action of an axoaxonic synapse at a synaptic terminal that increases the neurotransmitter released by presynaptic membrane
Presynaptic facilitation
