Great to see so many of you at the revision session today.
I have listed some MCQs for you to answer in this shared forum and discuss.
Have fun::
1. Which of the following is an element of the peripheral nervous system?
a. Receptors
b. Cervical plexus
c. Ganglia
d. Trigeminal nerve
e. All of the above
a. Receptors
b. Cervical plexus
c. Ganglia
d. Trigeminal nerve
e. All of the above
2. The colloquialism "gray matter" refers to somebody using his intellect or reasoning ability. In reality, what is gray matter?
a. Meninges
b. Myelinated nerve fibers
c. Cell bodies
d. Nodes of Ranvier
e. Neurofilaments
a. Meninges
b. Myelinated nerve fibers
c. Cell bodies
d. Nodes of Ranvier
e. Neurofilaments
3. All of the following are properties of neurons, except:
a. High metabolic rate
b. Longevity
c. Specialized for conduction
d. High mitotic rate
e. Limited ability for oxygen deprivation
a. High metabolic rate
b. Longevity
c. Specialized for conduction
d. High mitotic rate
e. Limited ability for oxygen deprivation
4. The action potential of a nerve cell:
a) results from a large increase in the membrane permeability to sodium ions.
b) can summate one with another.
c) may vary considerably in amplitude.
d) becomes larger as stimulus strength increases.
5. The velocity of action potential propagation:
a) is independent of an axon’s diameter.
b) depends on the thickness of the myelin around the axon.
c) will be unaffected if the axon becomes demyelinated.
d) is fastest in unmyelinated axons.
6. In a neuron, neurotransmitters are stored in
a) the cell body
b) vesicles within dendrites
c) the cytoplasm of the nucleus
d) vesicles within axon terminal
7. Which of the following actions would be considered a parasympathetic response?
A) increase in heart rate
B) decrease in digestion
C) increase in salivation
D) decrease in salivation
Short Answer:
1. Outline your understanding of a voltage gated channel.
2. What is a receptor? Which type of receptors are found in the human body?
3. What role do the association neurons play in the CNS?
Multiple choice questions:
ReplyDeleteQ1 a, Q2 c, Q3 d, Q4 a, Q5 d, Q6 d, and Q7 c.
Not too sure about them all but hope someone can point out where I made mistakes.
Will attempt short answers at a later stage.
Yes I like your answers Mirela, so i guess I will have a go at answering some of the short answer questions. Feel free to correct me if I am wrong, but to my understanding the voltage gated channel works in response to the potential of the membrane. That means they open or close in response to the electrical charge inside the cell.
ReplyDeleteReceptors are responsible for detecting changes, which are usually transmitted as an impulse. These changes include things such as temperature, pressure or even orientation (if you know what I mean by that ). Receptors are then classified by what stimuli (or change) they are able to detect. The name of the receptor kinda gives away its function. For example:
*thermoreceptors= respond to changes in temperature
*photoreceptors= respond to light (photons)
*chemoreceptor= respond to chemicals
*mechanoreceptor= respond to pressure
*nociceptors= respond to stimuli which are related to pain ( i always remember this one by looking at the noci part and thinking ‘no see I’. Just think you have fallen down and someone has come up to you to see if you are okay and you respond by saying. ‘no, see I fell down and I am in pain’. That works for me but it may not help you)
Oh wait I forgot about the little neurons... If they are association neurons the question is, what do they associate with? I think they associate with the sensory and motor neurons. I cannot help but think of them as the boss. They listen to what the sensory neuron has to say ‘motor is not doing any work’ (stimuli). They take on this complaint (stimuli), and then tell the motor neurons to get back to work and this brings about a response which activates the machinery (muscles or glands etc.)
ReplyDeleteI don’t plan on writing it like that in an exam, but I thought I would just share how my brain thinks about all this neurology lol
well i know im probably just re-writing what Elise has written but its good revision so here goes..
ReplyDeleteUNDERSTANDING OF VOLTAGE GATED CHANNEL:
They open and close in response to a membrane potential, so activitated by a change in electric potential (stimulus) An example of this is a sodium channel:
-A stimulus (as mentioned before) causes the sodium gates to open slightly, and sodium starts to trickle into the cell..
-if the cell reaches threshold (negative 60), sodium gates will open wider and sodium 'floods' in, bringing the inside of the axon to postive 30..
-at this point sodium gates close and potassium gates open..potassium pours out of cell allowing neuron to become polarised again
-Then sodium potassium pump actively starts to transport sodium out and potassium back into neuron
The action potential continues because as the sodium comes into the cell it diffuses to other areas within the axon (this continues down length of axon)occurs more quickly in myelinated axons!
I dont know if that is right or not? because I have that example but then when its put into simplistic terms which is 'voltage gated channel is closed when intracellular environment in negative (sodium cannot enter) and opens when intracellular environment is positive (sodium can enter)'. It doesnt make sense because it says if cell reaches negative 60 or threshold gates open wide.. but in that definition when the inside of the cell is negative the gate should be closed. Anyway if you could just make sense of this for me? No doubt its a silly question!!
WHAT IS A RECEPTOR? WHICH TYPE OF RECEPTORS ARE FOUND IN THE HUMAN BODY?
Its important to remember that survival depends upon first sensing something (such as change in internal and external environment) and then interpretting the stimulus. Ok so a receptor is a structure specialised to respond to stimuli, and an activation of a sensory receptor results in depolarisaton which triggers impulses to the CNS. A receptor is classified by the stimulus type and by the location of the receptor. So there are 5 main receptors classified by their stimulus type:
-mechanoreceptors
-thermoreceptors
-Photoreceptors
-Chemoreceptors
The two that best apply to the oral cavity are mechanoreceptors as they respond to touch, pressure, vibraton,stretch and itch (PDL). Secondly the nociceptors which are sensitive to pain (PDL AND PULP).
Receptor cell by location (3types):
- exteroceptors: respond to stimulus outside the body (found near body surface)
-interoceptors: respond to stimulus inside the body, sens to chemical change, stretch and temp
-Propioceptors: 'muscles constantly advises brain of ones movements' so obviously found in skeletal muscles etc. (think of the elephant standing on the little beach ball, has amazing and unrealistic proprioception)
WHAT ROLE DO ASSOCIATION NEURONS PLAY IN CNS?
The association neurons (intergration neurons) are 'the middle men' between the sensory and motor neurons. They are fully responsible for making sense of the information being brought in by the sensory neuron and then have to decide if and what action is needed and then pass on that message to the motor neurons to be taken to an effector for a response.
I dont know if any of this is right? but was good way to write some 'sort of' answers down. Any clarification would be great :)
If I am understanding this correctly outside of the neuron is +ve and inside is -ve. So as sodium slowly enters the cell it makes it a little less -ve (perhaps thats were this -60 comes into play). Because it is not as -ve as before (it now has more +ve ions) the sodium gates open wide and eventually becomes +vely charged.
ReplyDeleteWith the MCQ
ReplyDeleteQ1 I answered a) but now the more I think about it the more I think it amy be e).
Also just realised I answered d) to Q5 but that is wrong. However not sure if correct answer is a) or b). Any ideas?
Hi guys.. I have just come back from overseas. I will read through all your posts thoroughly and get back to you by the end of this week. In the meantime please continue this excellent work that I see here!!!
ReplyDeleteSophie
Hey mirella with that theory I think you may be spot on, after thinking about it that definately makes sense.. so maybe the 'negative 60' is really starting to turn positive in comparison to how negative it usually is! Also I was thinking that does the chemically gated channel allow the sodium to trickle in first, as the neurotransmitter attached to the receptor stimulates the gate to open, then this change in membrane potential allows the voltage gate to open! Not sure if that makes sense but just a possiblity I was thinking of last night, Ill have a look at your multiple choice aswell and see what I think... Thanks for your help :)! and thanks sophie!!!
ReplyDeleteI think it makes sense for the chemically gated channel to open first to allow in sodium... otherwise how else is it going to get more positive?? Once the gate has been open sodium rushes in and the depolarisation begins. Now sodium wants to join the party for two reasons 1) cause og the negativity and 2) becasue there isnt very mainy sodium ions inside the cell (ions move from high concentration to a low concentration)... Is this something like what you were thinking???
ReplyDeletelets break down question one. Receptors are def apart of the PNS. The cervical plexus i think has something to with the spinal nerves (if i remember correctly) so since it is a nerve it must branch away from the CNS and be apart of the PNS??
ReplyDeleteThe ganglia is a collection of neuron cell bodies outside of the CNS so they must have something to do with PNS. The trigeminal nerve is a mixed nerve, and this one must have something to with the PNS as well.... So i think all of the above is the correct answer....
Now for question five, i find that a and b are so similar.. but we could try break it down again.. so i remember reading that the larger the axons diameter, the faster it conducts the impulses. So here a) sounds correct.. But then would a thicker myelin sheath increase the diatmeter of the axon? and we know that the presence of the sheath prevents the charge from leaving the axon... Now I am confused lol... so what do you guys think?
sorry for all the comments... but i just did a bit of a google search and discoverd that the cervical plexus are spinal nerves and most of them are responsible for supplying nerves to the skin and neck. They detect sensory impulses from the skin, neck, back of head and ear area. So that means it is part of the PNS..
ReplyDeleteok so with the channels this is how i see it...
ReplyDeletefrom neuron to neuron, or from neuron to to dendrite the channel would be the chemically gated channel as the neurotransmitter released over the synaptic cleft which then attaches to receptor on on adjacent neuron/dendrite..which is the stimuli for the chemically gated channel.. then after this occurs and sodium is allowed in, it reaches threshold and then the voltage gated channels open wider! also i get how it repolarises now, and mikaelas steps to neuro make sense.. it took me a while but i get it now!
OMG team. This is the best trail of thinking I have ever read!!!! I am amazed at your innate understanding of this very difficult concept now. I love the way you have all brainstormed this together!! And yes, the answer to question 1 is e as you have all workshopped. Now the debate still remains with question 5. Would anyone like to have another go at this one? I think breaking it down will be of an enormous help.
ReplyDeleteSophie
So what type of axons would contain the myelin sheath? It’s usually those axons which are long or large in diameter. Sooo the question is would these axons still be able to conduct the action potential just as fast as those with the myelin sheath??
ReplyDeleteI also remember reading in the text book that a Schwann cell can surround an axon in the PNS without even going through the coiling process. These fibres are classified as being unmyelinated.
a) does have the word 'independent' in its answer, and I don’t think that the velocity of the action potential depends just on the axons diameter, it also depends on the presence of the myelin sheath. I think b) might be the better answer because the Schwann cell which goes through the coiling process provides a much thicker sheet of myelin. Hopefully this makes sense, and it’s too far off from the true answer
* not too far from the true answer sorry is what i meant...
ReplyDeleteI think that B is the correct answer! I heard it from one of the youtube videos that I watched from one of the powerpoints! Also Elise if you read this could I have your help with something one of the embryology questions on the work sheet is 'Which of the two types of bone formation – endochondral or membrane ossification – applies to the formation of the facial skeleton. Describe how this occurs and facial bone formation begins in the pre-natal period'..... Ive had a lot of trouble wrapping my head around the two. I think the answer is intramembranous ossification: meckle cartilage forms from each side of arch and dissapears as the bony mandible forms from ossification lateral to and in close association with the cartilage etc...
ReplyDeletecan you help me make more sense of that? :) thanks
Sorry liv, I can’t help you a lot because I am having trouble with the exact same thing. So lets put our heads together and try work this out.
ReplyDeleteSo far this is all I have:
'intramembranous ossification is formation of osteoid (bone matrix) between two dense connective tissue sheets. During intramembranous ossification, mesenchymal cells differentiate into osteoblasts to form the osteoid' (thats straight out of the text book). This then becomes bone once it has been calcified.
So I was thinking that perhaps bone formation was in response to other tissue development which encourages the mesenchymal cells to turn into osteoblastss. Other than that I don’t really understand it either...
Tomorrow morning when my brains nice and fresh I will try have another think.
This is how I answered that question
ReplyDeleteBone has two main embryonic origins: cartilage replacing bone (endochondrial ossification) and membrane bone (membranous ossification).
Frist to form (around week 5) is cartilage (from mesenchyme underlying the brain) to form cranial base
Meckels cartilage develops from first branchial arch and to form mandible making mandible the only facial bone derived from endochondrial ossification.
The intermembranous ossification starts in week 9 and creates all other facial bones.
Do we need any more in depth answers?