The nervous system Flashcards
1
Q
Where is the nervous system found?
A
Only in multicellular animals.
2
Q
What are the main cells of the nervous system called?
A
Neurons.
3
Q
Can neurons divide and reproduce like other cells?
A
No, neurons are highly differentiated and cannot divide or reproduce.
4
Q
What does it mean that neurons are “electrically excitable”?
A
They respond to stimuli by changing their membrane voltage.
5
Q
How do neurons communicate with other cells?
A
Through specialized structures called synapses.
6
Q
What is the main role of the nervous system?
A
To coordinate sensory information from the body or environment with appropriate actions in the body.
7
Q
cell body
A
where organelles are located
8
Q
dendrites
A
that receive signals from other neurones
9
Q
axon
A
transmits signals other neurones
10
Q
synapse
A
allow information to pass onto the next cell
11
Q
organisation of the Nervous system
A
Central nervous system
- brain
- spinal cord
peripheral nervous system
- cranial nerves
- spinal nerves
- ganglia
12
Q
Organisation of the Central nervous system
A
- The CNS has white (bundles of axons) and grey (cell bodies) matter
- In brain white matter is in the centre
- In spinal cord, the grey matter is in the centre
- Both also have cavities that are filled with CSF – cerebrospinal fluid that carries nutrients and waste.
13
Q
What are the three major regions of the vertebrate brain?
A
Forebrain, Midbrain, and Hindbrain.
14
Q
What is the main function of the forebrain?
A
Regulates sleep, olfactory inputs, learning, and complex processing.
15
Q
What does the midbrain do?
A
Coordinates sensory input.
16
Q
What is the role of the hindbrain?
A
Coordinates involuntary activities like breathing and heartbeat.
17
Q
What are the main parts of the cerebrum?
A
Forebrain thalamus hypothalamus.
18
Q
What is the main function of the cerebrum?
A
Information processing (learning emotion memory perception voluntary movement).
19
Q
What connects the left and right cerebral hemispheres?
A
Corpus callosum.
20
Q
What brain region is considered the oldest evolutionary part?
A
Brainstem (midbrain pons medulla oblongata).
21
Q
What are the functions of the brainstem?
A
Basic autonomic survival behaviours transfer of information between PNS and CNS.
22
Q
What do the pons and medulla oblongata control?
A
Breathing heart & blood vessel activity digestion swallowing vomiting.
23
Q
Which brain region contains about half of the body’s neurons?
A
Cerebellum.
24
Q
What does the cerebellum do?
A
Coordinates movement & balance motor skills learning language and memory.
25
PNS - sensory system
- made of "afferent" neurons
- relays information from the body or the environment to the CNS
26
PNS - integrative system
- made of "interneurons"
- connect CNS and PNS
- most abundant neurons in the body
27
Sensory neurones
- activated by sensory input from the environment (heat, pain etc)
- most sensory neurones are pseudo-unipolar, which means they have only one axon split into two branches
28
What is the function of sensory receptors?
To detect external stimuli.
29
What do mechanoreceptors detect?
Physical force such as pressure or stretch.
30
What do thermoreceptors respond to?
Temperature changes.
31
What do chemoreceptors detect?
Dissolved chemicals.
32
What do nociceptors detect?
Pain.
33
What do proprioceptors detect?
Positional information about the body.
34
interneurons
* Interneurons connect motor and sensory neurons, and transfer signals between them = form circuits.
* Can also connect with each other
* Neurons that transmit = highly branched axons
* Neurons that receive = highly branched dendrites
35
PNS - somatic and autonomic systems
- made of "efferent" motor neurons
- relays information from the CNS to the body
- controls skeletal muscles and gland
36
motor neurons
* Cell body in CNS, axons connect to muscles, glands and organs
* Transmit impulses from spinal cord to skeletal muscles to control movement
* Upper motor neurons: travel between the brain and spinal cord
* Lower motor neurons: travel from spinal cord to muscle
* Multipolar (one axon and several dendrites)
37
PNS - autonomic nervous system
- controls involuntary actions
- sympathetic division - fight or flight: involuntary response
- parasympathetic division - rest and digest involuntary response
38
PNS - enteric nervous system
controls the gut smooth muscles and the secretion of the associated organs
39
PNS - somatic or motor system
- controls voluntary actions i.e. skeletal muscles
- cranial nerves: linked to brainstem
- spinal nerves: linked spinal cord
40
glial cells/ neuroglia
* Involved in feeding, insulating and protecting the neurons
* Smaller than the neurons (10 glial cells / 1neuron)
* Can divide and reproduce
41
Astrocytes
feed and support neurons, build the blood/ brain barrier, remove dead synapses
42
microglia
Remove by phagocytosis endogenous dead tissue and foreign bodies
43
oligodendrocytes
Build the insulating axon myelin sheath in the CNS
44
Schwann cells
Build the axon myelin sheath in the PNS
45
Ependymal cells
- line the ventricles of the brain and the central canal of the spinal cord.
- Participate in the production of the cerebrospinal fluid.
- Can differentiate into new neurons but do not divide
46
the myelin sheath
* Lipid-rich substance surrounding the axons to insulate them
* Casing made of oligodendrocytes and Schwann cells extensions
* Myelin wraps the nerve in segments, with gaps called Nodes of Ranvier
* Myelin increases the speed at which electrical impulses
travel along the axon by forcing them to “jump” from one
node of Ranvier to another.
* “Fuelling station” for the axon after the generation of electrical impulses
* Coordinates the transport of cytoskeletal proteins and organelles
* Similar structure found in some invertebrates (shrimps, annelid worms)
47
cell signalling
* Cell signalling = cells communicating with one another
* A single cell may be sending and receiving multiple signals at once
* Cells mostly “detect” signals by protein receptors on their surfaces
* The receptor cell then decides how to interpret the signal
48
1- resting potential
* Potassium accumulates inside the cell, while sodium and chloride concentration are higher outside the cell
* Negative gradient = form of chemical energy
Value = - 70 mV
* Gradient maintained by a sodium-potassium pump (using ATP as energy source)
49
2 - depolarisation
* A signal is received by a receptor cell.
* The receptor cell converts the signal into an electrical signal by letting Na+ flow into the cell body.
* Depolarisation of the cell membrane.
* The gradient between the interior and exterior of the cell decreases → the cell’s polarity, decreases → Potential increases
50
3 - voltage gated ion channels
* When the cell body gets positive enough and reaches -55mV the voltage-gated sodium channels open
* Na+ enters the cell, depolarisation accelerates until it reaches its peak at 40mV
51
4 - repolarisation
- At the peak action potential, K+ channels open
- The gradient increases again
- The membrane potential goes down again and repolarises and reaches a value below -70mV
- The cell becomes hyperpolarized
52
5 - hyperpolarisation
* The membrane potential reaches a value below resting potential
* The cell becomes hyperpolarised
* Membrane potential returns to the resting potential
53
6 - refractory period
* Lag phase where no more APs can be generated
* Inactivation of voltage-gated sodium channels and no new signal can be generated during that time.
* Sets the maximum frequency at which impulses can occur
54
7 - AP transmission
* The sodium inflow in the rising AP phase creates a current that depolarises the adjacent
region
* This process is repeated until the synapse
* Magnitude will be the same at every location
* One way direction due to the refractory period behind the AP
55
generation of action potential
* Once initiated, AP has a magnitude independent of the strength of the stimulus = “all or none” response
* the same potential is generated in adjacent areas of the membrane and spreads along axons/dendrites.
56
frequency of AP
- The information about the strength of the signal is encoded in frequency not amplitude
- AP has a constant magnitude but a neuron can produce hundreds of APs a second
* Strong stimulus = more frequent AP
* Small stimulus = less frequent AP
57
saltatory conduction
* In myelinated axons, the myelin means voltage-gated sodium channels are restricted to gaps between the myelin called nodes of Ranvier.
* Therefore Myelin increases AP conduction speed
* This process is known as saltatory conduction
58
chemical synapses
releases chemical neurotransmitter from the presynaptic neuron to the post synaptic cell. by far the most common
59
electrical synapses
have gap junctions and electrical current flows directly from pre- to post-synaptic neuron
60
post synaptic response
* The cell body receives inputs from hundreds of dendrites. Some inhibitory and some excitatory
* The cell body sums up these signals
61
the synapse
* Neurotransmitters bind to receptors
* Receptors are often ligand-gated ion channels which modify ion gradient in the
receptor cell
62
Excitatory postsynaptic potential (EPSP)
K+ and Na+ acts to bring membrane potential to threshold
63
Inhibitory postsynaptic potential (IPSP)
Cl- act to do the opposite (bring membrane potential to threshold)
64
neurotransmitters
* A neurotransmitter molecule can bind to different types of receptors that can excite or inhibit the postsynaptic cell
* Neurotransmitter signalling is terminated by several methods:
* Simple diffusion away from the membrane
* Recapture by the presynaptic neurone
(allows recycling)
* Enzymatic hydrolysis
* Over 100 types in 5 categories
* Acetylcholine (ACh) is the most common in vertebrates
* Multitude of roles, usually excitatory, in CNS and PNS
* 2 major types of ACh receptors with different roles
➢The ligand-gated ion channel ACh receptor at the
neuromuscular junction triggers ion-channel opening and an EPSP
➢The metabotropic ACh found in organs like the heart opens K+ channels (hyperpolarisation) and reducing the rate of contraction
65
multiple sclerosis
progressive destruction of the myelin sheath by the immune system
66
Ataxia
several types, in brain, CNS or PNS, usually following physical damage
67
Huntington's disease
genetic disease, mutated protein toxic to nerve cells
68
motor neuron disease
rare, dementia
69
multiple system atrophy
symptoms similar to Parkinson’s disease, accumulation of protein a-synuclein
70
progressive supranuclear palsy
accumulation of protein Tau
71
Parkinson's disease
* Neurodegenerative disease
* Caused by neuronal loss in an area of the midbrain, the substantia nigra.
* Causes movement disorder and is characterised by tremors and muscular rigidity
* Proteins aggregate into Lewy bodies in neurons
* Eventually leads to dopamine reduction
72
MEG3
non-coding RNA strongly up- regulated in Alzheimer's human neurons and sufficient to induce a process called necroptosis leading to the loss of neurons in the brain
73
Alzheimer's disease
* Neurodegenerative disease, causing loss of neurons in the brain
* Starts in the hippocampus and spreads in a predictable pattern to other regions of the brains
* 70% of cases of dementia
* Affects first memory and ability to perform task and movements, followed by decline of behavioural, social and verbal skills
74
Curare, botulinum toxins
block ACh transmission
75
Diazepam
reduces anxiety by binding to the GABA receptor (increasing inhibitory
signalling)
76
How are depression and other mood disorders commonly treated, and what is an example of a medication used?
- They are often treated with compounds that increase the concentration of monoamines (such as serotonin, norepinephrine, and dopamine) in the brain.
- Example: Fluoxetine (Prozac) – a Selective Serotonin Reuptake Inhibitor (SSRI) that increases serotonin levels by blocking its reabsorption.
77
glutamate - amino acid neurotransmitters
* the most abundant neurotransmitter
* excitatory
* key role in memory
* contributes to the death of neurones after injury (e.g. stroke) : excitotoxicity
78
Gamma - aminobutyric acid - amino acid neurotransmitters
* metabolite of glutamate
* Inhibitory in adult brain
79
Noradrenaline and Dopamine (from tyrosine) - monoamine neurotransmitters
* Noradrenaline acts as an excitatory neurotransmitter in the PNS
* Dopamine is mostly confined to the CNS
80
Serotonin from tryptophan - monoamine neurotransmitters
* Enhances mood, cognition, learning and memory
* Involves in sleeping, eating, digestion and vasoconstriction
* Produced by nerve cells around the gut: enteric nervous system
