Biology P4 random notes

[zeebujha]

can anyone tell me the role of synapses for section B type questions. Because i dont think i have enough points to fill up all that space they give

do you mean the need for the synapse such as summation, one directional impulse etc. If that is the case then we share the same boat. Am not very sure about that section either!

exactly. Right now, a detailed answer can really help

okay, I will try to get back with the answer as soon as I can

 

[ivorydale]

thankuu

 

[bionology]

Synapses
In the nervous system, a synapse is a junction that permits a neuron to pass an electrical or chemical signal to another cell . Synapses are essential to neuronal function: neurons are cells that are specialized to pass signals to individual target cells, and synapses are the means by which they do so.
When an action potential arrives, the Calcium channels open and a surge of Ca ions are transported in. The calcium ions causes the vesicles containg ACH to travel and fuses along with the presynaptic membrane (where the Ca channels are present)
Then by the process of exocytosis, the vesicles containg ACH empty the ACH into the synaptic cleft (space between pre and post synaptic membrane)
The ACH binds to the post synaptic membrane and causes the Na channels to open, Na ions rushes in and the depolarisation of the membrane (hence action potential generated) the process take 0.5ms
1. Synapses ensure 1 way transmission (as ACH vesicles are in pre and Receptors are on post synaptic membrane)
2. They ensure a wide range of responses ( interconnection of many nerve pathways)
3. Involved with the memory (may generate a new synapse)

 

[bionology]

draw this diagram as well, No more detail is needed in the question. Be sure you use appropriate language (scientific)

 

[bionology]

labels
1. The circle wit small bead is the vesicle containing ACH
2. The beans shaped on yellow part is the Ca channels
3. pink ones are receptors
4.yellow part is the axon terminal
5. space between the two is synaptic cleft
6.the green one is dendrite

 

[beso2011]

GUYZZZZZZZZZZZZZZZz very very very very importnat this year WHAT ARE Photons ??? PHOTONS

 

[zeebujha]

Synapses
In the nervous system, a synapse is a junction that permits a neuron to pass an electrical or chemical signal to another cell . Synapses are essential to neuronal function: neurons are cells that are specialized to pass signals to individual target cells, and synapses are the means by which they do so.
When an action potential arrives, the Calcium channels open and a surge of Ca ions are transported in. The calcium ions causes the vesicles containg ACH to travel and fuses along with the presynaptic membrane (where the Ca channels are present)
Then by the process of exocytosis, the vesicles containg ACH empty the ACH into the synaptic cleft (space between pre and post synaptic membrane)
The ACH binds to the post synaptic membrane and causes the Na channels to open, Na ions rushes in and the depolarisation of the membrane (hence action potential generated) the process take 0.5ms
1. Synapses ensure 1 way transmission (as ACH vesicles are in pre and Receptors are on post synaptic membrane)
2. They ensure a wide range of responses ( interconnection of many nerve pathways)
3. Involved with the memory (may generate a new synapse)

EXPLANATION REQUIRED FOR THE ADVANTAGES!!!!!!!!!!

 

[brighton93]

Hey guys !!! i really really need help with the local circuits thing in the transmission of action potentials =(
could you explain pleaseeeeeeeeeeeeeeeeeeee... i freak out every time i see a question about that in the past papers !!!!

 

[beacon_of_light]

GUYZZZZZZZZZZZZZZZz very very very very importnat this year WHAT ARE Photons ??? PHOTONS

photons in biology? Which chapter are you talking abt?

 

[zeebujha]

GUYZZZZZZZZZZZZZZZz very very very very importnat this year WHAT ARE Photons ??? PHOTONS

The only chapter where I think we might come across photons is Photosynthesis. But we don't need to mention photons there either. Mention of energy of light, frequency and wavelength is adequate

 

[bionology]

i guess talking about light photons in the cyclic and the non cyclic processes

 

[bionology]

This is what the examin wants, you do not need to get into PhD details, you are awarded marks accordingly, and for the way you write your answer. These points with a little elaboration would score you full

. ensure one-way transmission
. receptor (proteins) only in postsynaptic, membrane / neurone
. vesicles only in presynaptic neurone
. ref. adaptation ;
. increased range of actions ;
. due to interconnection of many nerve pathways ;
. ref. inhibitory synapses ;
. involved in memory / learning ;
. due to new synapses being formed ;
. e.g. summation / discrimination\

 

[ivorydale]

This is what the examin wants, you do not need to get into PhD details, you are awarded marks accordingly, and for the way you write your answer. These points with a little elaboration would score you full

. ensure one-way transmission
. receptor (proteins) only in postsynaptic, membrane / neurone
. vesicles only in presynaptic neurone
. ref. adaptation ;
. increased range of actions ;
. due to interconnection of many nerve pathways ;
. ref. inhibitory synapses ;
. involved in memory / learning ;
. due to new synapses being formed ;
. e.g. summation / discrimination\

thnx

 

[zeebujha]

This is what the examin wants, you do not need to get into PhD details, you are awarded marks accordingly, and for the way you write your answer. These points with a little elaboration would score you full

. ensure one-way transmission
. receptor (proteins) only in postsynaptic, membrane / neurone
. vesicles only in presynaptic neurone
. ref. adaptation ;
. increased range of actions ;
. due to interconnection of many nerve pathways ;
. ref. inhibitory synapses ;
. involved in memory / learning ;
. due to new synapses being formed ;
. e.g. summation / discrimination\

what I mean was, I needed explanation for:
adpatation
summation
discrimination

 

[ParanoidAleveler]

Heyy can some1 please explain:

(e) how C4 plants are adapted for high rates of carbon fixation at high temperatures in terms of:
- high optimum temperatures for the enzymes involved
- the spatial separation of initial carbon fixation from the light-dependent stage

 

[bionology]

Summation is the operation of combining a sequence of numbers using addition , (simply relates to the addition of different nerve pathways resulting in a wide range of responses)
adaptations referring to the above point of the presynaptic membrane adaptations

Summing up, it is not some points which have a different concept, they're just telling us how much and how to elaborate the points mentioned
so, nothing to worry about!

 

[NIXORCollege]

Summation
Several presynaptic neurones release neurotransmitter
Cumulative effect reaches a threshold to depolarise postsynaptic membrane
E.g. rod cells when they synapse with relay neurones in the retina
Spatial summation
Several impulses arrive at one neurone via several synapses
Cause sufficient depolarisation / open sufficient sodium ion channels
For threshold to be reached
Temporal summation
Several impulses arrive at same neurone via same synapse
Threshold → action potential

Inhibition
More inhibitory postsynaptic potentials IPSPs than excitatory postsynaptic potentials EPSPs
Reduces membrane potential / makes more negative
Hyperpolarisation of postsynaptic membrane
Cancels effect of action potential when several synapses

The Mechanisms Of Transmission At An Excitatory Synapse

 

[NIXORCollege]

The Mechanisms Of Transmission At An Excitatory Synapse
Nerve impulse reaches synaptic knob/presynaptic membrane/neurone
Depolarisation opens Ca2+ gates / calcium ions enter
Ca2+ causes vesicles containing neurotransmitter to fuse with membrane
Release of neurotransmitter / into synaptic cleft / by exocytosis
Diffuse across synaptic cleft
Neurotransmitter binds to specific receptors in postsynaptic membrane
Sodium channels open / sodium ions enter
Depolarisation of postsynaptic membrane
Threshold causes an action potential along postsynaptic neurone
Neurotransmitter are quickly removed from the postsynaptic membrane
Diffuse out of the synaptic cleft
Taken up by presynaptic membrane by endocytosis
Enzymes break down neurotransmitters into inactive substances

 

[NIXORCollege]

The Agonistic And Antagonistic Effects Of Chemicals On Synaptic Transmission
Agonists/antagonists are similar in shape to neurotransmitter
Fit into specific protein receptors of postsynaptic membrane
Agonists → same effect as neurotransmitter
Anatoxin produced by some algae and mimics effect of acetylcholine
Swallowing H2O contaminated with anatoxin causes continuous salvation in mouth
Antagonists block action of neurotransmitter
Prevent neurotransmitter from binding with their receptor sites
High blood pressure can be treated by drugs called β-blockers
Antagonist of adrenaline-receptors on membrane of muscle cells in heart
Curare blocks action of acetylcholine at the junction of nerves and muscles
Useful as a general muscle relaxant in patients undergoing major surgery

 

[NIXORCollege]

Action Potentials And Nerve Impulses
Change In Membrane Permeability Leading To The Generation Of An Action Potential
Stimulus reaches threshold
Voltage-regulated sodium channels open / influx of Na+ / down electrochemical gradient / +ve feedback
Depolarisation / inside becomes +ve / membrane potential reverses
//Depolarisation opens sodium channels in adjacent membrane
Potassium channels open (slower than Na+ gates) / diffusion of K+ ions out of neurone
Repolarisation
Sodium channels close
Hyperpolarisation due to overshoot in movement of K+out of the cell
//Membrane potential is lower than resting potential
//Interior of the cell becomes -ve \ membrane is more permeable to K+ ions than to Na+ ions
Sodium-potassium pump restores RESTING POTENTIAL