Structure and Function of the Nervous System Flashcards
1
Q
What are the elementary building blocks of the brain?
A
Neurons
2
Q
What are the main cell types in the nervous system?
A
Neurons and glial cells
3
Q
Which are the key structural elements of a neuron?
A
- They consist of a cell soma (body), axon, and dendrites
- Communicate with other neurons and cells at specialized structures called synapses, where chemical and electrical signals can be conveyed between neurons.
4
Q
How does an action potential occur?
A
- -70mV
- Threshold @ -55mV
- When neurotransmitters bind on the postsynaptic neuron’s receptors, it can cause depolarisation
- Repeated depolarisation eventually reaches the Threshold @ -55mV - Depolarisation (rising phase)
- When threshold is reached, a large number of sodium channels open and allow Na+ ions into the cell
- Causes massive depolarisation of the neuron (becomes 0 and then positive)
- The influx of positive ions creases the electrical signal known as the ACTION POTENTIAL - Peak, where Na+ channels close and K+ channels open
- K+ ions will flow out of the cell - Repolarisation (falling phase)
- Caused due to the loss of K+ ions - Hyperpolarisation
- Overshoots the resting potential
- Phase known as refractory period where it is very hard for neuron to be fired again - Resting potential
- After refractory period
5
Q
How does synaptic transmission work?
A
- As the action potential depolarises the terminal membrane, it causes voltage-gated Ca2+ channels to open WHICH causes Ca2+ to flow into the cell
- Ca2+ causes vesicles (containing neurotransmitters) to bind with cell membrane of presynaptic neuron
- Neurotransmitter is released by exocytosis into the synaptic cleft, and diffuses across the cleft
- Transmitters binds with the receptor molecules in the postsynaptic neuron’s membrane
6
Q
What are the two main subdivisions of the nervous system?
A
- Central Nervous System (CNS)
- Brain and spinal cord - Peripheral Nervous System
- Sensory and motor nerves, and associated nerve cell ganglia (groups of neuronal cell bodies)
- Located outside of the CNS
- Made up of the somatic and autonomic systems
- Somatic: neurons bringing messages from the senses to the CNS and vice versa
- Autonomic: neurons that control the heart, intestines and other organs
7
Q
What is the difference between grey and white matter?
A
- White matter is composed of myelinated axons
- Gray matter is composed primarily of neurons
8
Q
Which are the four main lobes of cortex?
A
- Frontal lobe
- Parietal lobe
- Temporal lobe
- Occipital lobe
9
Q
What are the main subdivisions of the frontal cortex?
A
- Motor cortex
- Dorsolateral prefrontal cortex
- Ventrolateral prefrontal cortex
- Orbitofrontal cortex
10
Q
What is topographical representation?
A
Illustrates the topographical correspondence between cortical regions and body surfaces with respect to somatosensory and motor processes
11
Q
What are glial cells’ function?
A
Provide structural support and insulation for neurons
12
Q
Oligodendrocytes
A
- Produce myelin around the axons of neurons
- Central nervous system
- Myelinate axons in the brain and spinal cord
13
Q
Schwann cells
A
- Produce myelin around the axons of neurons
- Peripheral nervous system
- Myelinate axons in the periphery of the body
14
Q
Soma
A
The soma (cell body) contains the chromosomes
15
Q
Axons
A
- Information flows from the dendrites through the cell body to the axon
- Information is summed at the axon hillock
16
Q
Dendrites
A
- Branching fibers that form the information-receiving pole of the nerve cell
- Surface is lined with synaptic receptors
- Some have dendritic spines (larger surface area, more info it can receive)
17
Q
Membrane potential
A
The voltage across the neuronal membrane at any moment
18
Q
Resting potential
A
The difference in voltage between the inside and outside of a neuron
(approx. resting potential is -70mV)
19
Q
Equilibrium potential
A
When there is no net flow of ions in or out, the membrane is said to have reached its equilibrium potential
20
Q
Presynaptic terminal
A
- The point from which an axon releases chemicals into the synapse
- Releases neurotransmitters when action potentials depolarise its axon terminal
- This release of neurotransmitter is mediated by calcium ions
21
Q
Postsynaptic terminal
A
- The point of an axon receiving chemicals
- Neurotransmitters bind to receptors on the membrane of postsynaptic neuron
22
Q
Purpose of neuronal membrane
A
To control the exchange of chemicals between the inside and outside of cell
23
Q
Explain selective permeability
A
- A cell membrane will allow some ions (incl. water, oxygen and CO2) to pass through more readily than others (uncharged ions can pass through via simple diffusion)
- Ions that cannot flow freely may cross through specialised protein channels
- Without SP, the sodium-potassium pump would be far less effective in creating a conc. gradient (K+ inside; Na+ outside)
24
Q
Ion channels
A
- Pore-forming proteins created from an amino acid chain
- Channels differ in selectivity
- Channels move across the lipid bilayer
- Channels can be altered or modulated based on cellular needs
25
Ligand
A molecule that binds to a protein (ex. of a protein: an ion channel)
26
Ion pumps
- Works to maintain the concentration gradient
- In the case of the sodium-potassium pump, it repeatedly transports three sodium ions out of the cell while drawing two potassium ions to it
27
What is the difference between concentration gradients and electrical gradients?
- Conc. gradients: move ions to areas of lowest concentration
- Elec. gradient: move ions to areas having opposite electrical charges
28
Why is a neuron 'charged'?
- Neurons are like batteries
- They separate electrical charges, creating potential energy that can be tapped into when needed
- The plasma membrane of a neuron is the barrier that separates ions
- Negative charge inside; Positive charge outside
29
What is the all-or-none law?
- The all-or-none law states that a neuron will produce either an action potential of maximal strength or none at all
- The decision to send an action potential occurs at the axon hillock
30
Why is there an overshoot (action potentials)?
- To allow for a refractory period where the neuron cannot be fired for a split second
31
Why don't action potentials remain depolarised?
- The inactivation of the Na+ channels means that no sodium will pass through
- No sodium means no depolarisation, which subsequently means no action potential
32
Depolarisation
- The electrical potential change that results in the propagation of an action
- Due to the depletion of K+ ions
- Neurons will produce an action potential only if the depolarisation exceeds the threshold of excitation (about 15mV from resting potential)
33
Saltatory conduction
- The process of action potentials moving from node to node along a myelinated axon
- Increases the speed of action potential and decreases the energy expenditure of the neuron
34
What are the two factors affecting the speed of an action potential?
- Diameter of the axon
- Whether the axon is myelinated
35
Neurotransmitter
Any substance, such as acetylcholine or dopamine, responsible for sending nerve signals across a synapse between two neurons
36
How does transmitter release affect the membrane potential?
- The binding of neurotransmitters to the postsynaptic membrane receptors change the membrane potential
- The postsynaptic potentials can either be excitatory (depolarising the membrane) or inhibitory (hyperpolarising the membrane)
- Ex. Transmitter release causes membrane potential to be more positive (depolarise) and it peaks at excitatory postsynaptic potential
