Lecture 22

Question 1

What do neurons consist of?

Answer 1

Every neuron consists of a cell body (containing the nucleus) with usually one long axon and several shorter, branching dendrites.

Question 2

What is the fundamental task of a neurons?

Answer 2

The fundamental task of a neuron, or nerve cell, is to recieve, integrate, conduct and transmit signals.

Question 3

How long can axons be?

Answer 3

Axons can range in length from less than 1mm to more than 1m in length.

Question 4

What are some features of axons?

Answer 4

They have dendrites, cell body (nucleus), axon, and terminal branches of axon.

Question 5

Neurons are ___________?

Answer 5

Neurons are discrete cells.

Question 6

Neurons decide to do what?

Answer 6

Neurons decide to transmit information or not.

Question 8

What is the role of dendrites?

Answer 8

Dendrites receive information from other neurons, pressure and heat.

Question 8

What is in the cell body?

Answer 8

The cell body contains the nucleus and all of the information in the genome.

Question 9

What is the role of the axon?

Answer 9

The axon sends information to another neuron or a muscle.

Question 10

what do neurons undergo changes in?

Answer 10

Neurons undergo changes in membrane potential.

Question 11

What is membrane potential?

Answer 11

Membrane potential is the difference in the concentrations of ions on opposite sides of a membrane.

Question 12

What is the typical potential of a membrane?

Answer 12

Cell membranes are normally in the range of -70mV to -40mV.

Question 13

When does depolarization occur?

Answer 13

Depolarization occurs if the interior voltage becomes less negative (-70mV to -60mV)

Question 14

When does hyperpolarization occur?

Answer 14

Hyperpolarization occurs if the interior voltage becomes more negative (-70mV to -80mV)

Question 15

What do cells read?

Answer 15

Cells read the change in voltage and use it as an intracellular signal.

Question 16

What is resting potential?

Answer 16

When a neuron is not active, its membrane potential is called resting potential.

Question 17

What are excitatory signals?

Answer 17

Excitatory signals open (Na cation channels) which depolarizes the membrane

Question 18

What are inhibitory signals?

Answer 18

Inhibitory signals open either Cl channels or K+ channels, which suppresses firing and hyperpolarizes the membrane.

Question 19

What does membrane potential do?

Answer 19

Membrane potential propagates through the membrane.

Question 20

What is the role of VGSC in the nervous system?

Answer 20

Voltage-gated Na+ channels transmit signals in a wave through the nervous system.

Question 21

What happens when voltage difference is high?

Answer 21

Voltage difference is high = channels are tightly closed

Question 22

What happens when voltage difference is low?

Answer 22

Voltage difference is low = channels open and allow sodium ions to pass.

Question 23

VGSC does what altogether?

Answer 23

VGSC starts the depolarization phase and depolarizes the membrane.

Question 24

What does repolarization require?

Answer 24

Depolarization of the membrane requires opening of additional channels => these are the delayed K+ channels.

Question 25

Why else do K+ channels open?

Answer 25

These channels also open in response to membrane depolarization (that is, they are also voltage-gated), but have slower kinetics.

Question 26

What is the role of the K+ channels?

Answer 26

The voltage gated K+ channel ends the depolarization phase.

Question 27

What gives rise to an action potential?

Answer 27

The changes in the Na channels, K channels and current flows give rise to a traveling action potential.

Question 28

How do electrical signals propagate?

Answer 28

Electrical signals propagate through the neuron until it reaches the synapse.

Question 29

What are synapses?

Answer 29

Neuronal signals are transmitted from cell to cell at specialized sites of contact known as synapses.

Question 30

Chemical synapses?

Answer 30

Chemical synapses have neurotransmitters and receptors for signalling, release into the synaptic cleft and are fairly common. They are also slow compared to other types.

Question 31

Electrical synapses?

Answer 31

Electrical synapses have gap junctions and are in physical contact. They have no neurotransmitters and are faster than chemical synapses

Question 32

What is a neurotransmitter?

Answer 32

A neurotransmitter is a small signal molecule secreted by the presynaptic nerve cell at a chemical synapse to relay the signal to the postsynaptic cell.

Question 33

Neurotransmitters are....?

Answer 33

Neurotransmitters are composed of diverse molecule types

Question 34

What occurs when an action potential arrives at the presynaptic site?

Answer 34

When an action potential arrives at thre presynaptic site, the depolarization of the membrane opens VGCCs that are clustered in the presynaptic membrane.

Question 35

What does Ca2+ influx cause?

Answer 35

Ca2+ influx triggers the release into the cleft of small signal molecules known as neurotransmitters that are stored in the membrane-enclosed synaptic vesicles and released by exocytosis.

Question 36

Neurotransmitters diffuse rapidly where?

Answer 36

The neurotransmitter diffuses rapidly across the synaptic cleft and provokes an electrical change in the postsynaptic cell by binding to and opening ligand-gated ion channels.

Question 37

how do we measure increases in intracellular Ca2+

Answer 37

Fluorescent calcium sensors are commonly used to measure increase in intracellular Ca2+ in neurosn as a proxy for neuronal activity

Question 38

What is the neuromuscuar junction?

Answer 38

The neuromuscular junction is the specialized chemical synapse between a motor neuron and a muscle cell

Question 39

What is the acetylcholine receptor?

Answer 39

Teh acetylcholine receptor is a ligand-gated ion channel that opens transiently by acetylcholine released from the motoneuron.

Question 40

What does action potential activate?

Answer 40

When the incoming action potential activates a Ca2+ channel in the T-tubule membrane, it triggers the opening of a Ca2+ release channel in the closely associated sarcoplasmic reticulum membrane.

Question 41

Sequence of events at muscle cells and calcium channels?

Answer 41

1. Ach is released, binds to receptors , and opens sodium ion channels, leading to an action potential in sarcolemma. 2. Action potential travels along the T-tubules.

Question 42

What is optogenetics?

Answer 42

Optogenetics is a biological technique to control the activity of neurons or other cell types with light. - This is achieved by expression of light sensitive ion channels in neurons.

Question 43

What are photosensitive ion channels?

Answer 43

Channel rhodopsin are photosensitive ion channels that open in response to light.