Neurophysiology

Question 1

Name 3 gated ion channels

Answer 1

1. Ligand (chemically) gated
2. Voltage gated
3. Mechanically gated

Question 2

Give an example of a active transport pump

Answer 2

Sodium/potassium pump (3 Na for every 2 K, each cycle consumes 1 ATP)

Question 3

What is a major ion in intracellular fluid

Answer 3

K (potassium)

Question 4

Define membrane potential

Answer 4

Difference in electrical potential between the cytosol and extracellular fluid

Question 5

Define equilibrium potential

Answer 5

There is an equal movement of that specific ion in both directions

Question 6

What is the resting membrane potential of a neuron

Answer 6

-70mV (high permeability to K and low permeability to Na)

Question 7

Name two types of excitable cells

Answer 7

Neurons and muscle cells

Question 8

Define action potential

Answer 8

Rapid and brief reversal of the cell membrane potential that propagates quickly along cell membranes of excitable tissues

Question 9

Define the ‘all or nothing principle’

Answer 9

If the stimulus is strong enough to start an action potential, the shape of each action potential is independent of the strength of the stimulus

Question 10

What is meant by stimulus

Answer 10

A variable stimuli (mechanical, chemical or electrical) that causes the opening of Na+ gated channels

Question 11

Define refractory period and its two phases

Answer 11

Period during which a new action potential cannot be generated
1. Absolute
2. Relative

Question 12

Action potential travels ___ from stimulus

Answer 12

Away

Question 13

What are two factors influencing conduction speed

Answer 13

1. Axonal diameter
2. Myelination

Question 14

What are the node of ranvier

Answer 14

1-2um gaps in the myelin sheath where voltage gated channels are concentrated (crucial for action potential propagation)

Question 15

What is the result of hypokalaemia

Answer 15

Cells are hyperpolarized (less K+ inside the cell) causing cells to become less excitable and muscle weakness

Question 16

What is the action of lidocane

Answer 16

It blocks voltage gated Na+ channels and thus prevents the conduction of action potentials

Question 17

Define synapse

Answer 17

The junction between two neurons or between a neuron and a target cell

Question 18

What are the two types of synpases

Answer 18

1. Electrical
2. Chemical

Question 19

What is the purpose of a gap junction

Answer 19

Provides cytoplasmic continuity of 2 neurons for the free movement of ions

Question 20

What is the most frequent type of synapse in the mammalian nervous system

Answer 20

Chemical synapse

Question 21

Neurotransmitters can be ___ or ___

Answer 21

Excitatory OR inhibitory

Question 22

Define excitatory post-synaptic potential (EPSP)

Answer 22

Transient and local depolarization of the post synaptic cells caused by an excitatory neurotransmitter

Question 23

What is evoked post-synaptic potential

Answer 23

A transient change in post-synaptic membrane potential following binding of a neurotransmitter

Question 24

Define inhibitory post-synaptic potential (IPSP)

Answer 24

Transient and local hyperpolarization of the post-synaptic cell caused by an inhibitory neurotransmitter

Question 25

What are 2 types of neurotransmitter receptors

Answer 25

1. Ionotropic (direct gating) 2. Metabotropic (indirect gating)

Question 26

What happens when a neurotransmitter binds to a metabotropic receptor

Answer 26

It triggers a second messenger cascade to open/close other ion channels (i.e., it activates a G protein)

Question 27

What is the overall effect of ionotropic receptors

Answer 27

Classic neurotransmission

Question 28

What is the overall effect of metabotropic receptors

Answer 28

Neuromodulation

Question 29

Name 3 neurotransmitters that cause EPSPs and their receptor type

Answer 29

1. Glutamate (ionotropic and metabotropic) 2. Acetylcholine (ionotropic and metabotropic - can be inhibitory depending on receptor) 3. Noradrenaline (metabotropic - can be inhibitory depending on receptor)

Question 30

Name 2 neurotransmitters that cause IPSPs and their receptor type

Answer 30

1. GABA (ionotropic and metabotropic) 2. Glycine (ionotropic)

Question 31

Explain the summation principle

Answer 31

Each neuron has about 1000 synaptic inputs, and the summation of all these inputs at the axonal hillock will determine whether and action potential is fired

Question 32

Define a seizure

Answer 32

The excessive and synchronous discharge of a group of neurons

Question 33

Define neuromuscular junction

Answer 33

Chemical synapse between a motor neuron and a muscle fiber (aka myocyte)

Question 34

What is the difference between the end-plate synaptic region and the extrasynaptic region

Answer 34

The end plate region has the ligand-gated channels where the neurotransmitter binds and starts the action potential The extrasynaptic region is where there are voltage gated Na+ and K+ channels to propagate the action potential and cause muscle contraction

Question 35

What is the one transmitter at the neuromuscular junction

Answer 35

Ach

Question 36

Define the stretch reflex

Answer 36

Contraction of a muscle in response to its stretching