Physiology Quiz 2 (1/2)

Question 0

Types of synapses

Answer 0

Electrical

Chemical

Question 1

Synapse

Answer 1

Site at which an impulse is transmitted from one cell to another

Question 2

Ephaptic communication

Answer 2

Two excitable cells communicating by direct passage of electrical current between them (aka electrical synapses)

Question 3

Chemical synapses

Answer 3

A spike at the presynaptic membrane causes a release of neurotransmitter which attaches to receptors on the post synaptic membrane and causes depolarization

Question 4

Characteristics of chemical synapses

Answer 4

Synaptic delay of .5-1 msec
Transmission is unidirectional
Pharmacological agents can interfere.

Question 5

Characteristics of electrical synapses

Answer 5

No synaptic delay
Transmission is bidirectional
Pharmacological interference will not occur

Question 6

Neuromuscular junction

Answer 6

Chemical synapse between a motor nerve and muscle cell(s)

Question 7

Benzodiazepines*

Answer 7

Eg. Valium
Anti-anxiety for Pre-surgery
Blocks synaptic transmission*
Overuse can lead to too much transmission along nerve*

Question 8

What happens when the spike arrives at the alpha motor nerve ending?

Answer 8

1. Sudden large increase in calcium conductance at the presynaptic ending
   - calcium diffuses inward
   - attaches to enzymes, activating them
2. Activated enzymes cause the vesicles containing neurotransmitter to release into cleft
   - Ach is neurotransmitter in neuromuscular junctions
3. Ach diffuses across cleft
4. Ach attaches to cholinergic receptor on post synaptic membrane
5. Causes end plate potential (EPP)
6. Potentials will sum and when threshold is reached, the cell fires an action potential

Question 9

Synaptic delay due to…

Answer 9

Time it takes for chemicals to get across synapse

Question 10

Neurotransmitter at neuromuscular junction

Answer 10

Acetylcholine (Ach)

Question 11

Two types of cholinergic receptors

Answer 11

Nicotinic

Muscarinic

Question 12

Nicotinic receptors

Answer 12

Found on muscle, attach to nicotine or Ach

Question 13

Muscarinic receptors

Answer 13

Found on organ tissue (ie. cardiac tissue)

Question 14

Atropine

Answer 14

Used to block poisons

Used in surgical settings to interfere with fluid production in lungs

Question 15

Nicotinic cholinergic type receptors

Answer 15

Cholinergic receptors on muscle

Question 16

Characteristics of nicotinic cholinergic receptors

Answer 16

Can attach to Ach

Can attach to nicotine

Question 17

End plate potentials (EPP)

Answer 17

Depolarizations of the postsynaptic membrane surface that are conduced electronically.

• large numbers of EPPs will occur when the nerve fires a spike
• Hesse must sum to cause a spike in the muscle membrane

Question 18

What happens every time an alpha motor nerve cell fires?

Answer 18

An excess of Ach is released

Question 19

Is it important to terminate the action of Ach at the neuromuscular junction?

Answer 19

Yes- for normal activity, muscles need to contract and relax

Eg. Lungs-muscles need to both contact and relax in order for you to breathe

Question 20

How termination of Ach is achieved

Answer 20

Broken down by acetylcholinesterase or by less specific cholinesterases

Question 21

Where is Ach-ase located?

Answer 21

On surface of postsynaptic membrane

Question 22

Where are cholinesterases located?

Answer 22

In extra cellular fluid in synaptic cleft

Question 23

What happens to Ach when it is attached to a receptor and the EPP is initiated?

Answer 23

It detaches

Question 24

Three possibilities for Ach molecule after it detaches from postsynaptic membrane

Answer 24

1. Attaches to another receptor 2. Attaches to acetylcholinesterase on the membrane and is destroyed 3. Attaches to a cholinesterase in the synaptic cleft and is destroyed

Question 25

Is an Ach molecule more likely to attach to another receptor or to an esterase as it detaches?

Answer 25

More likely to attach to another receptor (1500 receptors/square micron) than an esterase (2600 esterases/square micron) but as it attaches and detaches, it will eventually run into an esterase

Question 26

What is Ach broken down into?

Answer 26

Acetyl CoA + choline

Question 27

What I acetylcholinesterase CoA used for?

Answer 27

Metabolism

Question 28

What is choline used for?

Answer 28

Actively transported back into nerve terminal and utilized again to manufacture Ach

Question 29

When Ach is manufactured in the cell body, how does it travel to the nerve terminal?

Answer 29

Antegrade axoplasmic transport by microtubules

Question 30

Succinylcholine

Answer 30

Attaches to nicotinic cholinergic receptors and initially activates then blocks (does not detach from site) Used for: Relaxing muscles during surgery or when using a breathing machine (ventilator). It is also used to induce anesthesia or when a tube must be inserted in the windpipe.

Question 31

Tubocurarine

Answer 31

This attaches to nicotinic cholinergic receptors and blocks them. (No muscle rigidity, just relaxes) Used for: a diagnosis agent for myasthenia gravis, and also to facilitate the intubation after induction of anesthesia in surgical procedure

Question 32

Alpha-neurotoxins

Answer 32

Block nicotinic cholinergic | preventing synaptic acetylcholine (ACh) from opening the ion channel.

Question 33

Loss of inner action of motor end plate

Answer 33

Can happen in trauma where nerve is cut Can also happen when the nerve has undergone mechanical or toxic insult sufficient to stop the motor nerve from functioning

Question 34

What happens when the motor nerve input to the motor end plate is lost?

Answer 34

Skeletal muscle develops high sensitivity to Ach - thought to be due to a spread of receptors beyond the motor end plate - cause unknown

Question 35

Fasciculations

Answer 35

Low level uncoordinated contractions "quivering" of skeletal muscle

Question 36

mEPPs

Answer 36

(Miniature end plate potentials) small depolarizations that occur at the end plates without any activation of the alpha motor neuron - thought due to spontaneous release of Ach - some evidence that they are the tonic influence that nerves exert upon muscle to maintain it in a healthy state. - another idea-they are releasing a chemical compound (probably a combo of both)

Question 37

Botulism

Answer 37

Caused by ingesting food contaminated with spores of clostridium botulinum which attacks and destroys cholinergic nerve terminals creating acute denervation of motor end plates of muscle. - respiration stops - used in Botox injections

Question 38

Myasthenia gravis

Answer 38

Autoimmune process which destroys nicotinic cholinergic receptors - most common in females - facial muscles fatigue when eating is usually first complaint - long process, patient eventually dies

Question 39

Treatment for myasthenia gravis

Answer 39

Give anti-cholinesterase drugs | -increases concentration of Ach for more activation of receptors

Question 40

Osteophytes

Answer 40

Inappropriate growth of bone to stabilize joints

Question 41

How does compression affect axoplasmic transport?

Answer 41

Slows it down