W4 Neurotransmission- Action potential and synaptic transmission

Question 1

How does a membrane become more permeable to ions?

Answer 1

Protein channels in the cell membrane will open
e.g. Voltage gated sodium ion channels for Na+

Question 2

What is compound action potential? (lab)

Answer 2

Action potentials are generated in individual axons whereas a compound action potential (CAP) is the sum of action potentials recorded between 2 external electrodes.

Question 3

What is the Somatic nervous system?
(SNS)

What does it consist of?

How does information travel?

Answer 3

The voluntary nervous system.

In this system, information from the periphery travels to the CNS along afferent sensory nerves and responses travel directly to skeletal muscles along effector motor nerves.

Includes Brain, Spinal cord, Neurones, Nerves, Muscle

Question 4

What does the CNS consist of?

Answer 4

The brain and spinal cord.

Question 5

What does the Peripheral nervous system consist of?

Answer 5

Sensory nerves
Nerves from spine to muscles

Question 6

Basic description of a neurone function:

Answer 6

Transmits action potential from dendrite to axon terminal
Many have a lipid sheath called myelin
Neurones form networks

Question 7

What is a synapse

Answer 7

Where 2 neurones connect

Question 8

What is glia?
Where are they found?

Answer 8

A type of cell in the PNS and CNS

Question 9

What is membrane potential (difference) a result of?

Answer 9

Ion gradients
(Ion conc outside vs inside a cell)

Question 10

An action potential is a form of…

Answer 10

Bioelectricity

Question 11

In most cells there are more positive ions….. the cell than…. the cell
So there is a negative potential difference

Answer 11

Outside
Inside
(around -70 mV)

Question 12

What are excitable cells?

Answer 12

Where their membrane potential changes in response to stimuli
e.g. neurons

Question 13

The cell membrane is highly… to ions

Answer 13

impermeable- ions can’t cross it easily
(more on outside)

Question 14

What does the Membrane potential allow?

Answer 14

Electrical signalling and excitability

Question 15

What are the types of transport across cell membranes

Answer 15

Passive diffusion
Facilitated diffusion
Active transport
Osmosis

Question 16

What is transported during passive diffusion?

Answer 16

Ethanol, O2, CO2, weak acids and bases

Question 17

What is transported during passive diffusion?

Answer 17

Ethanol, O2, CO2, weak acids and basesWhat

Question 18

What is transported during passive diffusion?

Answer 18

Ethanol, O2, CO2 (gases), weak acids and bases

Question 19

What is transported during facilitated diffusion?

Answer 19

Ions (Cl-, Ca2+, H2O, polar molecules)

Question 20

What is transported during active transport?

Answer 20

High Ca2+, High Na+, Low K+

Question 21

What does an excitable membrane need?

Answer 21

A negative membrane potential
Ion concentration gradients

Ion channels
- Voltage gated and Ligand gated
(Na+, K+, Ca2+)

Question 22

What are ligand gated channels?

Answer 22

They open when they bind to a certain molecule

Question 23

What is a ligand?

Answer 23

A molecule that binds

Question 24

Neurones brief description:

Answer 24

Highly specialised cells
Transmit information as electrical signals (nerve impulses or action potentials)
AP/signal received from other neurones or receptors
Propagated by axon (begins at axonal hillock)

Question 25

What is the resting membrane potential of a neuron? Maintained by?

Answer 25

-70mV The permeability of the membrane to K+ An energy dependent pump which moves the ions across the membrane.

Question 26

What does an action potential change the membrane potential to?

Answer 26

+30mV - It is depolarised (more positive)

Question 27

What are the meanings of depolarised and repolarised?

Answer 27

Depolarised= Membrane potential becomes more +ve Repolarised= Membrane potential becomes more -ve

Question 28

Action potential detail

Answer 28

* Stimulus = electrical, mechanical or chemical * Axon AP = electrical * Stimulus has to be strong enough to reach threshold potential * Enough depolarisation to open first NaV * Sodium channels in the membrane are sensitive to voltage and open when the THRESHOLD membrane potential is reached * The AP is ALL or Nothing

Question 29

Action Potential is unidirectional:

Answer 29

* When as action potential occurs, Na+ voltage sensitive channels open due to the local change in membrane potential * This causes more Na+ channels to open * Na+ channels behind the action potential become inactive * Therefore the action potential can only move in ONE direction

Question 29

Action Potential is unidirectional:

Answer 29

* When as action potential occurs, Na+ voltage sensitive channels open due to the local change in membrane potential * This causes more Na+ channels to open * Na+ channels behind the action potential become inactive * Therefore the action potential can only move in ONE direction

Question 30

Myelination in CNS vs PNS

Answer 30

CNS- Oligodendrocytes generate myelin PNS- Schwann cells generate myelin

Question 31

How are myelinated neurones more efficient?

Answer 31

Only nodes of Ranvier are exposed so action potential jumps from node to node. Much faster neurotransmission Much more energy efficient Saltatory conduction

Question 32

What is the structure of a synapse?

Answer 32

Pre-synaptic neuron, Synaptic cleft, Post synaptic neurone

Question 33

What happens when an action potential reaches the end of a neurone?

Answer 33

* Impulse dependent release * Membrane depolarisation opens voltage gated calcium channels * Calcium influx triggers vesicles to move to the presynaptic membrane * Vesicles fuse with the membrane and release their content into the synapse

Question 34

Neurotransmission at the synapse:

Answer 34

* AP depolarises terminal (opens voltage gated calcium channels) * Calcium enters cell * Triggers vesicles to move to the presynaptic membrane. Vesicles fuse with the membrane and leading to exocytosis of synaptic vesicles * Neurotransmitter diffuses across cleft * Binds with receptors on the postsynaptic cell * Initiates a response in the postsynaptic cell

Question 35

What are the functions of neurotransmitters? How are they synthesised?

Answer 35

* “A substance that transmits nerve impulses across a synapse (20nm)” : allows the information to flow! * Synthesised endogenously * Available in sufficient quantity in the pre-synaptic neuron to exert an effect on the postsynaptic neuron * If externally administered, it mimics the endogenously-released substance

Question 36

What are the different types of synapses?

Answer 36

* Synapse between two neurones * Sensory receptor and a neurone * Neuromuscular Junctions * Skeletal muscle, e.g. biceps * Smooth muscle, e.g. bronchioles

Question 37

What clinical pharmacologically relevant events occur at synapses? (5)

Answer 37

* Drug action * Action of neurotoxins * Formation of memories * Drug addiction * Neurodegeneration

Question 38

What do post-synaptic effects depend upon?

Answer 38

The transmitter and the receptor it binds to ( Ionotropic/ ligand gated) ( Metabotropic/ GPCR/ G-protein coupled) Some neurotransmitters will bind to both kinds of receptors, e.g. glutamate, GABA * Ionotropic responses are faster * Metabotropic responses can have more diverse effects

Question 39

What are the 2 types of receptors?

Answer 39

Ligand-gated ion channel receptors (fast) G-protein-linked receptors (slower)

Question 40

Receptors: Ligand gated (ionotropic) and GPCRs

Answer 40

* Ligand gated ionotropic receptors fast * Metabotropic (G-protein coupled/ GPCRs) * Metabotropic responses can have more diverse effects

Question 41

Describe Cholinergic neurotransmission in the neuromuscular junction