Lecture Exam 1 - Chapter 12 Study Guide Flashcards
1
Q
Know the 3 major functions of the nervous system
A
1) Sensory via sensory (afferent) neurons
2) Integrative
3) Motor via motor (efferent) neurons
2
Q
What is the meaning of the term afferent?
A
carrying impulses from receptors to or toward the central nervous system.
E.G Sensory neurons
3
Q
What is the meaning of the term efferent?
A
carrying impulses from the central nervous system to the effector (the tissue/organ that responds to the signals)
E.G. Motor Neurons
4
Q
What are the components of the Central Nervous System?
A
The Brain and Spinal Cord
5
Q
What are the components of the Peripheral Nervous System?
A
Cranial nerves and their branches
spinal nerves and their branches
ganglia
sensory receptors
6
Q
Define Term: Ganglia
A
small bundles of neuron cell bodies located outside brain and spinal cord
7
Q
Define Term: Sensory Receptors
A
dendrites of sensory neurons
8
Q
Know the subdivisions of the PNS
A
The Somatic Nervous System and the Autonomic Nervous System (also the enteric nervous system, which is, i believe part of the autonomic nervous system)
9
Q
What is the SNS?
A
The Somatic Nervous System – part of the peripheral nervous system that is under voluntary control
10
Q
What is the ANS?
A
The Autonomic Nervous System - part of the peripheral nervous system that is under involuntary control.
11
Q
What are the two branches of the ANS?
A
Sympathetic division (“fight or flight”) and parasympathetic division (“rest and digest”).
usually effectors receive nerves from both divisions and the two have opposing actions (i.e. sympathetic neurons increase heart rate and parasympathetic neurons decrease heart rate)
12
Q
What is the ENS?
A
The Enteric Nervous System – involved in regulating the digestive system
13
Q
Define: Neuron
A
electrically excitable nerve cells
14
Q
Define: Neuroglial cell
A
supportive, protective cells of the nervous system
15
Q
Define: electrical excitability
A
Ability to respond to a stimulus and convert it into an action potential
16
Q
Define: Stimulus
A
any change in the environment that is strong enough to initiate an action potential
17
Q
Define: Action Potential (nerve impulse)
A
a electrical signal that travels along the surface of the membrane of a neuron
18
Q
Know the difference between fast axonal transport and slow axonal transport
A
Slow axonal transport - conveys axoplasm (cytoplasm of neuron) in one direction only - from cell body to axon terminals. Speed = 1-5mm/day
Fast axonal transport - moves materials in both directions along the surface of microtubules. Speed = 200-400 mm/day. Uses specialized proteins that function as “motors” to move structural proteins (Kinesin)
19
Q
Name the functional classification of Neurons
A
Sensory, Motor, and Interneurons
20
Q
Name the function and location (CNS or PNS) of the neuroglia: Astrocyte
A
CNS. Provide support and protection – forms the blood brain barrier by wrapping processes around blood capillaries.
21
Q
Name the function and location (CNS or PNS) of the neuroglia: Ependymal cell
A
CNS. Line the ventricles of brain and central canal of spinal cord. Produce cerebrospinal fluid and assisting in maintaining circulation of the fluid.
22
Q
Name the function and location (CNS or PNS) of the neuroglia: Microglia
A
CNS. Function as phagocytes, destroying unwelcome materials.
23
Q
Name the function and location (CNS or PNS) of the neuroglia: Oligodendrocyte
A
CNS. Form a myelin sheath around axons in the CNS.
24
Q
Name the function and location (CNS or PNS) of the neuroglia: Satellite Cell
A
PNS. surround the cell bodies of neurons in ganglia – provide structural suppost and faciliate exchange of substances between the neurons and the extracellular environment.
25
Name the function and location (CNS or PNS) of the neuroglia: Schwann Cell
PNS. encircle PNS axons and form a myelin sheath around the axons.
26
Define Term: Myelin Sheath
axons are covered by a lipid and protein layer generated from the oligodendrocytes or Schwann cells.
27
Define Term: Unmyelinated
when axons do not have a myelin sheath
28
Define Term: Demyelinated
when axons have lost their myelin sheath
29
Define Term: Node of Ranvier
Periodic gap in the insulating sheath (myelin) on the axon of certain neurons that serves to facilitate the rapid conduction of nerve impulses.
30
Define Term: Neurolemma
The cell membrane of neurons
31
State two purposes of myelination
1) to electrically insulate the axons of neurons
| 2) to increase speed of nerve impulse conduction
32
What cells produce the myelin sheath?
Oligodendrocytes in the CNS and Schwann cells in the PNS.
33
Name the structural classification of Neurons
Multipolar, Bipolar, and Unipolar
34
Where is the gray matter located in a) the brain and b) the spinal cord?
gray matter in located in the outer layer in the brain and in the inner layer in the spinal cord
35
What is the composition of gray and why matter?
White matter = mostly myelinated axons
| Gray matter = mostly neuronal cell bodies and unmyelinated axons
36
Define: Graded Potential
electical signals in neurons - for short distance communication only
37
Define: Graded Potential
electical signals in neurons - for short distance communication only
Vary in size. Occur as a result of ligand-gated or mechanically-gated channels opening.
38
Define: Action Potential
electrical signals in neurons - allow for long and short distance communication
Do not vary in size. Occur rapidly in two phases: 1) depolarization phase - negative membrane potential becomes less negative until it reaches zero) and 2) repolarizing phase - membrane potential restored to resting state of -70mV
39
What are the four types of ion channels in nerve impulse production and conduction?
1. Leakage channels - randomly switch between opened and closed
2. Voltage-gated channels - open in response to change in membrane potential (voltage)
3. Ligand-gated channels - opens and closes in response to a chemical signal (a ligand binding to a specific receptor)
4. Mechanically gated channels - open in response to a mechanical stimulus such as vibration (a sound wave) or pressure (touch receptors in skin)
40
Define: Membrane potential
there is a difference in distribution of positively charged and negatively charged ions across the membrane -- this causes an electrical gradient called the membrane potential.
41
Define: electrochemical gradient
Both concentration gradients and membrane potentials are set up as a result of selective transport across the membrane. The combined influence of concentration gradient and membrane potential on movement of an ion is referred to as its electrochemical gradient.
42
Define: Resting membrane potential
small build up of negative ions inside cell membrane and small build up of positive ions outside membrane.
Na+ and Cl- ion concentrate high outside cell. K+ and PO4- concentration high inside cell, PO4- not free to leave because attached to other molecules.
Resting potential for neurons averaged -70mV (the minus meaning that the inside of the membrane is negative compared to the outside of the membrane)
43
What is the issue in multiple sclerosis
Myelin sheaths are destroyed
44
What is the resting membrane potential of a neuron?
around -70mV
45
What does it mean for the resting potential to be -?
a negative restig potential means that the inside of the membrane is negative compared to the outside of the membrane.
46
Know the differences between the properties of graded potentials and action potentials. Refer to table 12.2 on page 472. Origin. Types of Channels. Conduction. Amplitude. Duration. Polarity. Refractory Period.
Origin --
Graded Potentials: Arise mainly in dendrites and cell body
Action Potentials: Arise at trigger zones and propagate along the axon
Types of Channels --
Graded Potentials: Ligand-gated or mechanically gated ion channels
Action Potentials: Voltage-gated channels for NA+ and K+
Conduction:
Graded Potentials: Decremental (not propagated); permit communication over short distances
Action Potentials: Propagate and thus permit communication over longer distances
Amplitude (size):
Graded Potentials: Depending on the strength of the stimulus, varies from less than 1 mV to more than 50 mV
Action Potentials: All or none. typically about 100 mV
Duration:
Graded Potentials: Typically longer, ranging from several msec to several min
Action Potentials: shorter, ranging from 0.5 to 2 msec
Polarity:
Graded Potentials: May be hyperpolarizing (inhibitory to generation of an action potential) ro depolarizing (excitatory to generation of an action potential)
Action Potentials: Always consists of depolarizing phase followed by repolarizing phase and return to resting membrane potential.
Refractory Period:
Graded Potential: Not present, thus summation can occur
Action Potentials: present, thus summation cannot occur
47
Define: Depolarization
In the depolarization phase, negative membrane potential becomes less negative until it reaches zero
48
Define: Hyperpolarization
when a reponse makes the membrane more negative inside.
49
Define: Repolarization
in the repolarization phase, membrane potential is restored to resting state of -70mB
50
Define: Refractory period
during the absolute refractory period - even a very strong stimulus cannot initiate another potential
during the relative refractory preiod - a second action potential can be intiated by only by a very strong stimulus
51
Know the phrases in generation of an action potential
1) Resting membrane potential: Voltage-gated Na+ channels are in the resting state and voltage-gated K+ channels are closed
2) Stimulus causes depolarization to threshold
3) Voltage-gated Na+ channel activation gates are open (top of action potential) -- absolute refractory period
4) Voltage-gated K+ channels are open; Na+ channels are inactivating -- absolute refractory period
5) Voltage-gated K+ channels are still open; Na+ channels are in the resting state - relative refractory period
52
What does tetrodotoxin from pufferfish do?
blocs action potentials by inserting in voltage-gated sodium channels preventing them from opening
53
Define: Continuous conduction
in unmyelinated neurons, ions flow through voltage-gated channels along the membrane.
54
Define: Saltatory conduction
in myelinated neurons, the signal jumps from one node of ranvier to the next where the ion channels are present -- much faser than continuous conduction.
55
Define: Chemical synapse
the pre-synaptic and post-synaptic neurons do not touch. In response to a nerve impulse a neurotransmitter is released from the pre-synaptic neuron ad binds to receptors on the post-synaptic neuron. This opens ion channels.
56
Define: presynaptic Neuron
neuron sending the message
57
Define: Post-synaptic neuron
neuron receiving the signal
58
Define: Synaptic end bulb
bulb-shaped structres on the tips of some axon terminals, contain synaptic vesicles
59
Define: Synaptic cleft
space between pre- and post-synaptic neurons, full of interstitial fluid.
60
Define: Neurotransmitter
chemical signal released by neurons. Many types of neurotransmitters.
61
Define: Excitatory post-synaptic potential
A single postsynaptic neuron receives input from many pre-synpatic neurons, some of which release excitatory neurotransmitters and some of which release inhibitory neurotransmitters:
If the total excitatory effects are greater than the total inhibitory effects, but less than the threshold level of stimulation, the result is an Excitatory Post-Synaptic Potential that does not reach threshold. Following an EPSP, subsequent stimuli can more easily generate a nerve impulse through summation because the neuron is partially depolarized.
62
Define: Inhibitory post-synaptic potential
A single postsynaptic neuron receives input from many pre-synpatic neurons, some of which release excitatory neurotransmitters and some of which release inhibitory neurotransmitters:
If the total inhibitory effects are greater than the excitatory effects, the membrane hyperpolarizes (IPSP). The result is inhibition of the postsynaptic neuron and an inability to generate a nerve impulse.
63
Name three mechanisms for removal of a neurotrasmitter from the synaptic cleft
1. Diffusion -- some of the neurotransmitter diffuse away from the synaptic cleft
2. Enzymatic degradation - enzyme breaks down neurotransmitter
3. Uptake by cells - many neurotransmitters are actively transported by into the cell that released them (reuptake) or into neuroglia (uptake)
64
How does an axon diameter influence propagation of nerve impulses?
the larger diameter axons propagate action potentials faster than smaller ones due to their larger surface areas
65
What are the differences between A, B, and C fibers?
A fibers - largest diameter (5-20 micrometers) and myelinated. Conduct impulses at rate of 12-130m/sec. Sensory fibers for touch, pressure, and thermal sensations are A fibers.
B fibers - medium diameter (2-3 micrometers), also myelinated. Conduct impulses at 15m/sec. All motor fibers from brain to ganglia are B fibers.
C fibers - small diameter unmyelinated axons. Conduct at speeds of 0.5-2m/sec. Many sensory pain impulses conducted via C fibers. Some autonomic motor fibers from ganglia to organs are C fibers.
66
About how many different neurotransmitters are thought to exist?
about 100
67
Know the major classes of neurotransmitters as discussedin lecture
1) small molecules such as acetylcholine, amino acids, and gamma amino butyric acid (GABA)
2) Biogenic amines such as norepinephrine, epinephrine, dopamine, and serotonin
3) Neuropeptides, ATP, and other purines, nitric oxide
68
Why can the same neurotransmitter sometimes be excitatory and sometimes be inhibitory?
In some places, the receptors for the neurotransmitter may be on excitatory neurons, and on inhibitory neurons in others.
69
What happens in strychnine poisoning? What neurotransmitter is affected?
In spinal cord, Renshaw cells normally release an inhibitory neurotransmitter (glycine) onto motor neurons that prevents excessive muscle contraction.
Strychnine binds to and blocks glycine receptors in the spinal cord, producing massive tetanic contractions of all skeletal muscles. When the diaphragm contracts and remains contracted, you cannot breath.
70
Define: Integration
The nervous system integrates sensory information by analyzing and storing it, and making decisions about appropriate responses.
71
Define: Summation
If several presynaptic end bulbs release their neurotransmitter at about the same time, the combined effect may generate a nerve impulse due to summation.
Summation may be spatial or temporal.
72
Define: Spatial Summation
Summation of effects of neurotransmitters released from several end bulbs onto one neuron.
73
Define: Temporal Summation
Summation of effect of neurotransmitters released from 2 or more firings of the same end bulb in rapid succession onto a second neuron.
74
Understand the concept of neural circuits (networks). Explain the major features of the four types of neuronal circuits discussed in lecture and your textbook.
Groups of neurons are organized into circuits
(neural networks.) These include simple series,
diverging, converging, reverberating, and parallel
after-discharge circuits (Figure 12.27 a-d).
A neuronal network may contain thousands or even
millions of neurons. Organization of neuronal
networks continually breaking and reforming
(plasticity)
• Diverging -- single cell stimulates many others.
• Converging -- one cell stimulated by many others.
• Reverberating -- impulses from later cells repeatedly stimulate early
cells in the circuit (short-term memory).
• Parallel-after-discharge -- single cell stimulates a group of cells that all
stimulate a common postsynaptic cell (math problems).
75
What is meant by the term plasticity?
Organization of neuronal
networks continually breaking and reforming
(plasticity)
76
How well can CNS neurons regenerate?
CNS no repairs are possible
77
How well can PNS neurons regenerate?
PNS can repair damaged dendrites or axons
78
Explain why CNS neurons do not regenerate well.
Factors preventing neurogenesis in CNS:-
– inhibition by neuroglial cells
– absence of growth stimulating factors
– rapid formation of scar tissue
79
Briefly explain how PNS neurons regenerate
When there is damage to an axon, usually there are changes, called chromatolysis, which occur in the cell body of the affected cell. This causes swelling of the cell body and peaks between 10 and 20 days after injury.
By the third to fifth day, degeneration of the distal portion of the neuronal process and myelin sheath (Wallerian degeneration) occurs. Degenerated sheath removed by macrophages by phagocytosis.
Regeneration follows chromatolysis; synthesis of RNA and protein accelerates, favoring rebuilding of the axon and often taking several months.
80
Define the general characteristics: mutliple sclerosis
Progressive destruction of myelin sheath of
neurons in the CNS.
Usually appears between ages 20-40.
Affects females twice as often as males.
Auto-immune disease (attack by bodies own
immune system).
The term “scleroses” means hardened plaques. In
MS, multiple scleroses degenerate to hardened
plaques.
81
Define the general characteristics: epilepsy
Affects about 1% of world population.
Motor, sensory and psychological seizures
resulting from abnormal electrical discharges in
multiple neuronal circuits.
Many different causes
A number of anti-convulsive drugs now available.
Surgery used in severe cases.
82
Define the general characteristics: Guillain-Barre sydrome
```
A demyelination disorder in which
macrophages strip myelin sheath from PNS
axons.
Causes acute paralysis. May result from
bacterial infection.
Usually reversible.
```
83
Define the general characteristics: neuroblastoma
Tumor of immature nerve cells that occurs
in infants.
Usually in adrenal gland - cells of adrenal
medulla related to sympathetic neurons.
84
Define the general characteristics: neuropathy
a generalized term for any disease that
| effects the nervous system
85
Define the general characteristics: rabies
```
Caused by a highly infectious virus that
reaches the CNS very fast via axonal
transport.
Causes excitement, aggressiveness,
madness, paralysis and death.
Usually transmitted by bite of infected
animal (bats, dogs).
```
