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Foundation in Biology - Term 1 Part 1 > 4 - Nervous System > Flashcards

4 - Nervous System Flashcards

1
Q

In what type of animals is the nervous system found in?

A

Multicellular animals

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2
Q

Describe the cells found in the nervous system (& their features)

A
  • Nerve cells or ‘neurones’
  • Highly differentiated (can’t divide & reproduce) & specialised cells
  • Electrically excitable cells (change in membrane voltage required for cell response)
  • Use synapses to communicate with other cells
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3
Q

What does the nervous system do?

A

Coordinate sensory info from the body or the environment w/ the resulting actions from diff. parts of the body

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4
Q

Name the 3 parts of a neurone

A
  • Cell body
  • Dendrites
  • Axon
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5
Q

What is found in the cell body of a neurone?

A

Organelles

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6
Q

Describe the function of dendrites

A

Receive signals from other neurones

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7
Q

Describe the function of an axon

A

transmits signals to other neurones

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8
Q

Describe the function of a synapse

A

Allows info to pass onto next cell

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9
Q

Name the two types of nervous system

A
  • Central Nervous System (CNS)

- Peripheral Nervous System (PNS)

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10
Q

Name the main parts of the CNS

A
  • Brain

- Spinal cord

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11
Q

Name the main parts of the PNS

A
  • Cranial nerves
  • Spinal nerves
  • Ganglia
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12
Q

Describe how the CNS is organised

A
  • The CNS is composed of white & grey matter
  • White matter -> centre of the brain
  • Grey matter -> centre of spinal cord
  • Both also have cavities that are filled with CSF
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13
Q

What is white matter?

A

Bundles of axons

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14
Q

What is grey matter?

A

Cell bodies (w/ nuclei)

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15
Q

What does CSF stand for? Give its function

A

CSF = Cerebrospinal fluid

It carries nutrients & waste (also removes waste)

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16
Q

Name the three regions of the vertebrate brain

A
  • Forebrain
  • Midbrain
  • Hindbrain
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17
Q

Describe the function of the forebrain

A

Regulates sleep, olfactory inputs, learning & complex processing

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18
Q

Describe the function of the midbrain

A

Coordinates sensory input - sends signals to the forebrain to act on the stimuli that the midbrain has detected

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19
Q

Describe the function of the hindbrain

A

Coordinates involuntary activities

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20
Q

Explain the importance of the sensory system

A

Detects stimuli (e.g temp, pain) & relays info from the body or the environment to the CNS

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21
Q

Explain the importance of the integrative system

A

Connects CNS & PNS

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22
Q

Name the type of neurones that make up the sensory system

A

‘Afferent’ neurones

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23
Q

Name the type of neurones that make up the integrative system

A

‘Interneurones’ (most abundant neurones in the body)

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24
Q

Describe the function & features of sensory neurones

A
  • Activated by sensory input from the environment (e.g heat, pain etc.)
  • Most are pseudo-unipolar (only have one axon split into two branches)
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25
What are sensory receptors?
The specialised part of sensory neurones that allow external stimuli to be detected
26
Name the 5 types of sensory receptors
- Mechanoreceptors - Thermoreceptors - Chemoreceptors - Nociceptors - Proprioceptors
27
Give the stimulus for mechanoreceptors
Physical force
28
Give the stimulus for thermoreceptors
Temperature
29
Give the stimulus for chemoreceptors
Dissolved chemicals
30
Give the stimulus for nociceptors
Pain
31
Give the stimulus for proprioceptors
Positional info (adapt to positioning of the body)
32
Describe the the function of interneurones
- They connect motor & sensory neurones and transfer signals btw. them - They can also communicate w/ each other & form circuits
33
Where are interneurones in most animals found?
CNS
34
What is the main feature of neurones that transmit? (interneurones)
Highly branched axons
35
What is the main feature of neurones that receive? (interneurones)
Highly branched dendrites
36
Name the two systems that make up the PNS
- Somatic (motor) | - Autonomic
37
Describe the function of the PNS
- Relays info from the CNS to the body | - Controls skeletal muscles & gland secretion
38
Name the neurones that make up the somatic systems
Afferent sensory neurones & efferent motor neurones | efferent - 'exit' the nervous system
39
What does the somatic system do?
Controls voluntary actions i.e. skeletal muscles
40
What does the autonomic nervous system do?
Controls involuntary actions
41
Name the 3 divisions of the autonomic nervous system
- Sympathetic - Parasympathetic - Enteric
42
What response is produced by the sympathetic division?
'fight or flight' (involuntary)
43
What response is produced by the parasympathetic division?
'rest & digest' (involuntary)
44
What is the function of the enteric nervous system?
Controlling the gut smooth muscles & secreting of the associated organs (e.g. pancreas)
45
Give an example of what response the sympathetic division can produce in the body
- Increase heart rate | - Breakdown glycogen
46
Give an example of what response the parasympathetic division can produce in the body
- Decrease heart rate | - Synthesise glycogen
47
Describe the functions of motor neurones
- Part of the CNS and connect muscles, glands & organs throughout body - Transmit impulses from spinal cord to skeletal muscles to control movement
48
Where do the lower motor neurones travel to & from?
Travel from spinal cord to muscle
49
Where do the upper motor neurones travel to & from?
Travel btw. the brain & spinal cord
50
What is the main structural feature of motor neurones?
They are multipolar - one axon & several dendrites
51
Name other supporting cells found in the brain
- Glial cells (or neuroglia) - Astrocytes (macroglia) - Microglia - Oligodendrocytes - Schwann cells - Ependymal cells
52
Describe the function of glial cells
- Involved in feeding, insulating & protecting the neurones | - Can also divide & reproduce
53
How many types of glial cell are there?
5
54
How can the size of glial cells compare to neurones?
Glial cells are smaller than neurones (10 glial cells = 1 neurone)
55
Describe the function of astrocytes (macroglia)
- Feed & support neurones - Build the blood/brain barrier - Remove dead synapses
56
Describe the function of microglia
Remove endogenous dead tissue (tissue originating from the body) & foreign bodies by phagocytosis
57
Describe the function of oligodendrocytes
Build the insulating axon myelin sheath in the CNS
58
Describe the function of Schwann cells
Build the axon myelin sheath in the PNS
59
Describe the function of ependymal cells
- Line the ventricles of the brain & central canal of the spinal cord - Participate in the production of the cerebrospinal fluid - Can differentiate into new neurones (but do not divide)
60
Ependymal cells can make an unlimited amount of neurones through neurone regeneration. True or false?
False. There is a limited amount of neurone regeneration (once these cells used up, no more)
61
What is the myelin sheath?
It is a lipid-rich substance surrounding the axons - act as insulation
62
Name the parts that make up the myelin sheath
- Oligodendrocytes (casing) & Schwann cells (extensions) | - Myelin (wraps nerve in segments)
63
What are the Nodes of Ranvier?
Gaps/parts of the axon that are not wrapped in myelin sheath
64
Why are mitochondria spread along the axon?
So there is even distribution of energy
65
Explain the importance of the myelin sheath
- Increases speed at which electrical impulses travel along the axon by forcing them to 'jump' from one Node of Ranvier to another - 'Fueling station' for the axon after generation of electrical impulses (Also coordinates transport of cytoskeletal proteins & organelles)
66
How can knowledge of the myelin sheath help with diagnosis of certain diseases?
Demyelination (loss of myelin) is a hallmark of multiple sclerosis & other neurodegenerative diseases
67
How do cells detect signals?
Using the protein receptors on their surfaces - receptor cell then decides how to interpret the signal
68
A single cell may be sending and receiving multiple signals at once. True or false?
True
69
Describe the distribution of ions in cells at resting potential
Inside cell - higher K+ conc. | Outside cell - higher Na+ conc.
70
How is resting potential maintained?
- The gradient is maintained by sodium-potassium pump (which uses ATP to maintain this gradient) - These conc. gradients are a form of chemical energy
71
How does a neurone generate a signal?
1. Signal is received by receptor cell 2. The triggering event leads receptor cell converts signal's energy into an electrical signal - this is done by letting positively charged ions flow into cell body & depolarising cell membrane 3. As positive ions flow into the 'negative' cell, the diff. btw. the interior & exterior of the cell & thus the cells polarity decreases 4. If cell body gets positive enough that it can trigger the voltage-gated Na+ channels found in the axon, then the action potential will be sent
72
What is the function of the voltage-gated ion channels?
- They open & close in response to stimuli | - This allows movement of ions & therefore changes membrane
73
Why are ion channels in neurones 'voltage-gated ion channels'?
They open & close when the membrane potential is at a certain level (Don't need ATP - respond to change in potential diff. when reaches a certain level)
74
Why does depolarisation occur?
Depolarisation happens as a result of a nerve impulse causing Na+ to into the cell
75
What happens at the peak action potential?
K+ channels open & the cell becomes hyperpolarised
76
What is the threshold in nerve cells?
-55V
77
What happens if sodium ions influx?
- More Na+ channels open as they are voltage gated - This temporarily changes the membrane potential significantly - Once initiated an AP (action potential) has a magnitude independent of the strength of the stimulus (AP are an all or none response)
78
What has to be present in order for an action potential to be generated?
A large enough stimulus
79
How is the action potential distributed?
- AP has a constant magnitude & regenerates the same potential in areas of the membrane next to it (adjacent) - Therefore, AP can spread for along axons/dendrites for long distance communication
80
What is the refractory period?
After an AP been generated there is a lag phase where no more APs can be generated
81
Why does the refractory period occur?
- It is due to inactivation of voltage-gated Na+ channels | - This ensures all AP are the same & sets the max. frequency at which impulses can occur (recovery time)
82
If the stimulus is strong, what does this mean about the frequency of the AP?
Strong stimulus = more frequent AP | Small stimulus = less frequent AP
83
All action potentials are the same size (constant magnitude). True or false?
True
84
How does the AP travel? (hint: chain reaction)
- Na+ inflow in the rising AP creates current that depolarises the adjacent region - This process is repeated until the end of the axon/dendrite (synapse) (Magnitude will be equal at every location) - The zone immediately behind the AP is in the refractory period so APs can't go backward
85
Explain what is meant by saltatory conduction & why it occurs
- In myelinated axons, the myelin means voltage-gated Na+ channels are restricted to gaps btw. the myelin called Nodes of Ranvier - Therefore, myelin increases AP conduction speed (This process is known as saltatory conduction)
86
Describe electrical synapses
Electrical synapses have gap junctions & electrical current flows directly from pre to post-synaptic neurone
87
Describe chemical synapses
Chemical synapses release chemical neurotransmitter from the presynaptic neurone to the post synaptic cell
88
Are electrical or chemical synapses more numerous?
Chemical synapses are by far the most numerous
89
What happens at the synapse?
- Neurotransmitters often bind to ligand-gated ion channels (vesicle fuses w/ membrane & releases neurotransmitters) - This opens channels that allow specific ions across the postsynaptic neurone
90
What are the two outcomes of neurotransmitters binding to the ion channels at the synapse?
Excitatory postsynaptic potential (EPSP) - K+ & Na+ acts to bring membrane potential to threshold Inhibitory postsynaptic potential (IPSP) - Cl- acts to do the opposite
91
Describe the post synaptic response
- The cell body receives inputs from hundreds of dendrites (& therefore synapses) - Some inhibitory & some excitatory - The cell body integrates all of these signals to allow the decision to transmit an AP
92
What does the neurotransmitter molecule do?
It can bind to diff. types of receptors that can excite or inhibit the postsynaptic cell
93
Name the 3 methods that neurotransmitter signalling is terminated
- Simple diffusion away from the membrane - Recapture by the presynaptic neurone (allows recycling) - Enzymatic hydrolysis
94
How many neurotransmitters are there approx.?
Over 100
95
What is the most common neurotransmitter?
Acetylcholine (ACh)
96
There are 2 major types of ACh receptors w/ different roles. True or false?
True
97
The ligand-gated ion channel ACh receptor at the neuromuscular junction triggers...
The ligand-gated ion channel ACh receptor at the neuromuscular junction triggers... ion-channel opening & an EPSP
98
Name at least 2 common amino acids that act as neurotransmitters
- Glutamate - GABA (Gamma-aminobutyric acid) - Aspartate - Glycine
99
Give at least one feature of glutamate
- The most common neurotransmitter w/ ionic & metabotropic (initiates metabolic changes) receptors - Key role in memory - Contributes to death of neurones after injury (e.g. stroke) through a process called excitotoxicity
100
Give at least one feature of GABA
- Metabolite of glutamate | - Mostly linked to inhibitory synapses
101
Name at least 2 biogenetic amines that act as neurotransmitters
- Noradrenaline - Dopamine (both originate from amino acid tyrosine) - Serotonin (originates from tryptophan)
102
Give one feature of noradrenaline
It acts as an excitatory neurotransmitter in the PNS
103
Give at least one feature of dopamine
Is mostly confined in the CNS
104
Give at least one feature of serotonin
- Enhances mood, cognition, learning & memory | - Involves in numerous physiological processes such as sleeping, eating, digestion & vasoconstriction
105
Name one of the toxins that affect neurotransmitter systems
- Tetanus | - Botulinum
106
How are depression & mood disorders often treated?
Using compounds that increase conc. of the biogenic amines
107
How does valium reduce anxiety?
It binds to GABA receptor (increasing inhibitory signalling)
108
What is Alzheimer's disease?
A neurodegenerative disease causing loss of neurones in the brain
109
How does Alzheimer's work?
- Starts in the hippocampus & spreads in a predictable pattern to other regions of the brain - Affects 1st the memory and ability to perform tasks & movements, followed by decline of behavioural, social & verbal skills (Enlarged ventricles in the brain is a tell-tale sign)
110
What is Parkinson's disease?
- Neurodegenerative disease | - Caused by neuronal loss in an area of the midbrain (substantia nigra)
111
How does Parkinson's disease work?
- Causes movement disorder and is characterised by tremors & muscular rigidity - Eventually leads to dopamine reduction (Also, proteins aggregate into Lewy bodies in neurones)

Foundation in Biology - Term 1 Part 1 (8 decks)

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