8.2: Structures and Processes of the Nervous System Flashcards
1
Q
What are the 2 systems of the PNS and how are they different?
A
- Somatic System: Voluntary actions
- Autonomic System: Involuntary actions
2
Q
What does the somatic system consist of and do?
A
- Sensory receptors in the head and extremities
- Nerves that carry sensory information to the CNS
- Nerves that carry information from the CNS to skeletal muscles
3
Q
What does the autonomic system do?
A
- Controls glandular secretions
- Functions cardiac muscles
4
Q
What are the 2 main types of cells in the nervous system?
A
- Neurons
- Glial Cells
5
Q
What do neurons do?
A
- Conducts electrochemical signals
- Respond to physical and chemical stimuli
- Releases chemicals that regulate body processes
6
Q
What do glial cells do?
A
- Nourish neurons
- Remove their wastes
- Protect against infections
7
Q
What are the four common features of a neuron?
A
- Dendrites
- Cell Body
- Axon
- Branching Ends
8
Q
What do dendrites do?
A
- Receive nerve impulses from other neurons or sensory receptors
- Relay impulses to the cell body
9
Q
What does the cell body do?
A
- Contains a nucleus
- Receives input from the dendrites
- If the input is large enough, it is transmitted to the axon, where an impulse is initiated
10
Q
What does the axon do?
A
- Receives and processes input from the cell body
- Conducts input away from the cell body
11
Q
Where is the myelin sheath located and what does it do?
A
- Encloses some axons of neurons
- Protects the neurons
- Speeds the rate of nerve impulse transmission
12
Q
What is the role of the nervous system?
A
- Equipped to sense and responds to continuous changes in the internal and external environment
- Performs the function of regulating body structures and process to maintain homeostasis despite various fluctuations
13
Q
What does the afferent system do?
A
Receives and transmits input to the CNS by afferent neurons. Carries impulses impulses from sensory receptors to the CNS
14
Q
What does the efferent system do?
A
Transports input from the CNS to muscles and glands
15
Q
Is the afferent system motor or sensory?
A
Sensory
16
Q
Which system is subdivided into the parasympathetic and sympathetic systems?
A
The autonomic system
17
Q
Which system is subdivided into the autonomic and somatic systems?
A
The efferent system
18
Q
What do Schwann cells create?
A
Creates myelin
19
Q
What do myelin sheath cells do?
A
Protect the neuron and speed up nerve impulse transmission
20
Q
Where are the nodes of Ranvier?
A
In between the Schwann cells, on the axon
21
Q
What do the nodes of Ranvier do?
A
Speed up the rate of electrical impulse transmission
22
Q
What are the 4 factors of nerve signalling?
A
- Reception
- Transmission
- Integration
- Response
23
Q
Explain reception in neural signalling
A
Detection of stimulus, performed by neurons and specialized sensory receptors
24
Q
Explain transmission in neural signalling
A
Movement of a message along the neuron to and effector (muscles or glands)
25
Explain integration in neural signalling
Sorting and interpretation of multiple neural messages and determination of an appropriate response
26
Explain response in neural signalling
Output or action
27
What is a reflex arc?
A connection of neurons which responds to a stimulus
28
What is the charge on the inside of the cell in a resting neuron?
Contains anions, so the charge is negative
29
What are the 3 factors that maintains resting membrane potential?
1. Large negatively charged neurons in intracellular fluid
2. Plasma membrane has ion-specific channels that allow the passive movement of ions across the membrane
3. Na/K Transport Pump
30
What is the charge on the outside of a cell in a resting neuron?
Contains cations, so the charge is positive
31
Explain the first factor of the resting membrane potential
Neurons are too large to move through the membrane
32
Explain the second factor of the resting membrane potential
- K channels are usually open during resting potential (-70mV)
- Na is unable to move as easily
- This causes the charge inside the cell to become more negative, relative to the outside, which is positive
33
Explain the third factor of the resting membrane potential
- Na/K pump releases 3 molecules of Na, while 2 molecules of K comes in
- Uses ATP in hydrolysis
- Higher Na concentration outside the cell, higher K concentration inside the cell
34
What is the resting potential of an unstimulated neuron?
70mV
35
Explain the 1st step of an action potential
Triggered when threshold potential is reached
36
Explain the 2nd step of an action potential
When membrane potential reaches threshold potential, voltage-gated sodium channels open, making it permeable to sodium ions. The Na ions outside the cell move down their concentration gradient to an axon. In a millisecond or less, enough positively charged Na ions cross the membrane to a small area in the axon, making the potential difference 40mV
37
Explain the 3rd step of an action potential
The change in potential difference causes the Na channels to close, opening the K channels. The K ions move down their concentration gradient to the outside of the axon and carries a positive charge out. The membrane potential depolarizes, making the potential difference -90mV, causing the K channels to close
38
Explain the 4th step of an action potential
The NaK channel and the small amount of naturally occurring diffusion repolarizes the membrane to its original membrane potential of -70mV
39
Explain the 5th step of an action potential
A few milliseconds after the action potential occurs, the membrane cannot be stimulated and Na channels are temporarily inactive. This is called the refractory period.
40
Explain the myelinated neuron
The action potentials generate only at the nodes of Ranvier
41
What is the main difference between myelinated and unmyelinated neurons? How does it work?
Myelinated- Impulse performs a saltatory condition, where the impulse jumps or leaps
Unmyelinated- Impulse is continuous and does not perform saltatory condition, making the impulse transmission slower
42
How does the Na/K pump work?
- NaK pump uses ATP from hydrolysis to pump 3 Na ions out and 2 K ions in
43
What does acetylcholine do?
- Aids in muscle contraction, memory formation, and learning
44
What is the difference between excitatory and inhibitory neurotransmitters?
Excitatory: Speeds up nerve transmission by depolarizing the postsynaptic membrane
Inhibitory: Slows down nerve transmission by hyperpolarizing the postsynaptic membrane
45
Explain the pre-synaptic neuron
- When an action potential reaches the end of a presynaptic neuron, the impulse causes intracellular sacs that contain neurotransmitters to fuse with the membrane of the axon
- Synaptic vessels release their contents into the synaptic cleft by exocytosis
- Neurotransmitters diffuse across the synapse in a few milliseconds to reach the dendrites of the post-synaptic neuron/cell membrane of the effector
46
Explain the post-synaptic neuron
- Triggers nerve impulse in the next nerve cell
- Chemical signals open ion-gated channels
47
What is a neurotransmitter?
- Chemicals released from vesicles through exocytosis into the synaptic cleft
- Binds to receptors by on neurons, or effectors
48
What is the role of epinephrine?
- Fight or flight response
49
What is the role of serotonin?
- Aids in sleep, mood, attention, and learning
- Inadequate amounts of serotonin is linked to depression
50
What is the role of dopamine?
- Affects sleep, mood, attention, and learning
- Inadequate amounts is linked to Parkinson's
- Excessive amounts is related to schizophrenia
51
What is the role of endorphins?
- Creates a sense of euphoria
52
What are examples of weak points in our nervous system?
- Stimulants: Caffeine, nicotine
- Gases: Carbon monoxide
- Hallucinogens: LSD
- Depressants: Meth
- SSRIs: Prozac
- Poisons
