Chapter 2 (from the slides) Flashcards
(78 cards)
1
Q
What is the structure of the neuron?
A
- contains the soma, dendrites, axon, synapse, and terminal buttons
2
Q
What is the soma?
A
- the cell body
- contains the nucleus and much of the machinery that provides life processes to the cell
3
Q
What are the dendrites?
A
- the input structures.
- serve as important recipients of the messages between neurons
4
Q
What is the synapse?
A
messages that pass from neuron to neuron are transmitted across the synapse, a junction between the terminal buttons
5
Q
What is the axon?
A
- long, slender tube, often covered by a myelin sheath and carries info from the cell boy to the terminal buttons
- basic message that it carries is the action potential
6
Q
What is the terminal button?
A
the bud at the end of the branch of an axon; forms synapses with another neuron, and sends information to that neuron
7
Q
What is an action potential?
A
- a brief electrical/chemical event that starts at the end of the axon next to the cell body and travels toward the terminal button
8
Q
What is a neurotransmitter?
A
- a chemical that is released by the terminal button; has an excititory or inhibitory effect on another neuron
9
Q
What is the synaptic connection between neurons?
A
- generally, signals travel in a single direct at the synapse, from the the terminal button to the dendrites.
- keep in mind that there are exceptions.
10
Q
What is the unipolar axon classification?
A
- one stalk that splits into two branches
- usually sensory related to touch and proprioception
11
Q
What is the bipolar axon classification?
A
- one axon, one dendritic tree
- usually non-touch sensory
12
Q
What is the mltipolar axon classification?
A
- one axon, and many dendritic branches
13
Q
What is a nerve?
A
- it is a bundle of neurons
14
Q
What is the function of a neuron?
A
- it carries messages from the environment to he brain
15
Q
What are sensory neurons?
A
- neurons that carry messages toward the brain
16
Q
What are motor neurons?
A
- neurons that carry messages to the muscles
17
Q
What are interneurons?
A
- connect neurons (local & relay)
18
Q
What is contained in the internal structure of the neuron?
A
- nucleus, mitochondria, cytoplasm, endoplasmic reticulum, ribosomes, golgi apparatus, microtubles
19
Q
What is the nucleus?
A
- structure in the central region of the cell, containing the nucleolous
20
Q
What is the nucleolus?
A
- a structure that produces ribosomes
21
Q
What is a ribosome?
A
- a cytoplasmic structure, made of protein, serves as the site of production of proteins translated from mRNA
22
Q
What are chromosomes?
A
- strand of DNA that carries genetic information
23
Q
What is a gene?
A
- functional unit of the chromosome, which directs synthesis of one or more proteins.
24
Q
What is mitochondria?
A
- manufactures energy
- produces ATP
25
What does the goli apparatus do?
- does molecule assembly and packaging
26
What is cytoplasm?
- liquid in the cell that hold of the neuron structures
27
What is the function inside the axon?
- fast axoplasmic transport along microtubles
| - kinesin molecules walk away from soma; dynein walks towards the soma
28
What is the function outside of the cell?
- signal transmission via action potential
29
What are glia cells?
- "glue".
| - provides physical support & insulation, control nutrient flow, and are involved in phagocytosis
30
What are astrocytes?
- provide physical support, remove debris, and transport nutrients to neurons
31
What are micrglia?
- involved in phagocytosis and brain immune function
32
What are oligodendrocytes?
p provide physical support and from the myelin sheath around axons in the CNS
- white fatty packaging (CNS)
33
What are Schwann cells?
- form myelin for PNS axons & guide healing
| - Axon can heal in the peripheral nervous system
34
What are the nodes of ranvier?
- exposed part of the axon that is not covered by myelin sheath
35
What is the blood brain barrier?
- it is only selectively permeable.
| - its primary function is to maintain the integrity of neuronal transmission
36
Where is the blood brain barrier produced?
- produced by the cells in the walls of the brains capillaries
37
Where is the blood brain barrier more permeable at?
- more permeable at the postrema area
38
What is post trema?
- this is part of the brain that controls vomiting
| - toxins and poisons can be released
39
Why does the blood brain barrier exist?
- Transmission of messages from place to place in the brain depends on a delicate balance between substances within neurons and those in the extracellular fluid that surrounds them
- makes it easier to regular the composition of this fluid
40
What is the process of electrochemical conduction?
- dendrites receive chemical message from adjoining cells
- chemical messengers activate receptors on the dendritic membrane
- receptor activation opens an ion channels, which can alter membrane potential
- action potential can result, and is propagated down the membrane
- action potential causes release of transmitter from axon terminals
41
What is potential?
- stored up source of energy - electrical energy
42
What is action potential?
- the message that is conducted down the axon that consists of a brief change in the membrane potential from negative to positive back to negative
43
How does action potential occur?
- a rapid reversal of the membrane potential charge provide basis for conduction along an axon
- the threshold of excitation must be reached in order for this process to occur
44
What is threshold of excitation?
- value of membrane potential that must be reached to produce action potential
45
More action potential explained.
- a brief increase in the permeability of the membrane to NA+ (allowing them to rush in the cell) is immediately followed by a transient increase in the permeability of the membrane to K+ (allowing them to rush out)
- permeability i create by a protein molecule that proides an opening that permits ions to enter and leave cells
- these molecules provide ion channels
46
What occurs in hyperpolarization?
- the membrane potential quickly returns to normal, but first it overshoots the resting potential
- more polarized than usual
47
What are other qualities of action potential?
- this is an "all or none" event: RMP either passes the threshold or not
- Remains the same size without increase or decrease in size of charge
- When the axon splits, AP of the same size is conducted down both axons
48
What is the resting potential?
- this is the electrical charge across the membrane
| - voltage measures -70mV inside with respect ot the outside
49
What is depolarization?
- since the inside of the axon has a negative charge, when a positive charge is applied to the inside of the cell this process occurs
- it takes away some of the negative charge, reducing the membrane potential
50
What is diffusion?
- ion disperse in a medium to an equal distribution of concentration
- when there are no forces or barriers to prevent them from doing so, molecules will diffuse from regions of high concentration to regions of low concentration
51
What is electrostatic pressure?
- ions disperse in a medium to an equal distribution of electrical charges
52
What is intracellular fluid?
- fluid within the cells
| - has higher levels of organic anions (A-) and Potassium ions (K+)
53
What is extracellular fluid?
- fluid outside of the cells
| - Has higher levels of Chloride ions (Cl-) and Sodium ions (Na+)
54
What keeps potassium and chloride levels balanced?
- force of diffusion and electrostatic pressure
55
Are forces balanced with sodium?
- No, both want to go into the cell
| - sodium-potential transporter exchanges NA+ and K+ , pushing 3 sodium ions out for very two potassium ions they push in
56
What does it mean when we say that Na+ and K+ ion channels are voltage dependent?
- they open and close as a function of the membrane potential but their threshold is not the same!
57
What is the function of the sodium-potassium pump?
- address energy of sodium getting inside of the cell
58
Describe the action potential process in regards to Na+ and K+
- Sodium rushes in, potassium comes out a little, sodium channels become refractory and no more sodium enters the cells, more potassium is released and stays at rest, finally, a return of negative polarity occurs
59
What occurs with action potential in a myenilated axon?
- The only place where a myelinated axon comes into contact with the extracellular fluid is at the node of Ranvier, where the axon is naked
- no inward flow Na+ when sodium channels open because there is no extracellular sodium
- • Axon conducts electrical disturbance from the action potential to the next node of Ranvier
- triggers a new action potential at each node
- expend less energy to maintain sodium balance
- action potential is faster in a myelinated axon
60
What is saltatory conduction?
- action potential "jumps" from node to node in this particular case
- speeds of up the AP velocity
61
What is the presynaptic membrane?
- membrane of the terminal button that lies adjacent to the postsynaptic membrane and through which neurotransmitter is released
62
What is the postsynaptic membrane?
- cell membrane opposite terminal button in synapse; membrane of cell that receives messages
63
What is the synaptic cleft?
- space between the pre and postsynaptic membranes
64
What are post-synaptic potentials?
- produced by neuro transmitters
- brief depolarization or hyperpolarzations that increase or decrease he rate of firing of the axon of the postsyanptic neuron
65
What is the binding site?
- when neurotransmitters attach to a particular region of a receptor molecule
66
Where are three places in which synapses occur>
- on the dendrites (axodendritic)
- on the soma (axosomatic)
- on the axons (axoaxonic)
67
What are the two prominent structures in the cytoplasm of the terminal button and what do they do?
- mitochondria: terminal button needs energy to perform
- synaptic vesicles: contains 2 types
- small: contain molecules of the neurotransmitter produced by the golgi apparatus
- microtubles: responsible for transporting material between soma and terminal button
68
How do molecules of the neurotransmitter produce a depolarization or hyperpolarization in the postsynaptic membrane?
- They do so by diffusing across the synaptic cleft and attaching to the binding sits of special protein molecules located in the postsynaptic membrane
69
What happens when binding occurs in depolarization or hyperpolarization?
- Once binding occurs, postsynaptic receptors open neurotransmitter-dependent ion channels, which permit the passage of specific ions into or out of the cell
70
What is direct ion channel opening?
- when a molecule of the appropriate neurotransmitter attaches to it, the ion channel opens
o Formal name for this combination receptor/ ion channel: ionotropic receptor
Sensitive to acetylcholine
Contain sodium channels
When open, sodium enters and depolarizes membrane
71
what is indirect ion channel opening?
- Some receptors do not open ion channels directly but instead start a chain of chemical events
• Metabotropic receptors they involve steps that require that the cell expend metabolic energy
• located close to G protein
• when molecule of neurotransmitter binds with receptor, receptor activates G protein, which when activated, activates an enzyme that stimulates the production of a chemical- second messenger
• molecules of these travel through cytoplasm, attach selves to nearby ion channels, and cause them to open
- these take longer to begin and last longer
72
True or false: PSPS are either excitatory (EPSP) or inhibitory (IPSP).
- True
73
EPSP
- when sodium channels are opened, results in depolarization
Opening NA+ ion channels results in depolarization and an EPSP
Opening Cl- ion channels results in hyperpolarization of a depolarized membrane potential and therefore neutralizes EPSP
Opening Ca++ ion channels results in depolarization and an EPSP
74
IPSP
- Opening K+ ion channels results in hyperpolarization and an IPSP
75
What is neural integration?
- refers to the algebraic summation of PSPs
76
What is the process of neural integration?
- A predominance of EPSPs at the axon will result in an action potential
If the summated PSPs do not drive the axon membrane past threshold, no action potential will occur
Summated PSPs that do result in an action potential, determine the rate of firing
Note: inhibitory PSP does not necessarily translate into neural or behavioral inhibition!
77
What happens when several inhibitory synapses are active at the same time?
- the IPSPs they produce diminish the size of EPSPs and prevent the axon from firing
78
What happens when several excitatory synapses are active at the same time?
- the EPSPs they produce summate as they travel toward the axon, and the axon fires
