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biology > nervous conditions and muscles > Flashcards

nervous conditions and muscles Flashcards

1
Q

What is the cell body

A

Contains all the usual organelles
Large amounts of RER for protein synthesis and neurotransmitter production

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2
Q

What is a dendron

A

Divides into branches
Carries nerve impulses to cell body

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3
Q

What is an axon

A

Carry nerve impulses away from the body

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4
Q

What is a schwan cell

A

Surrounds the axon providing electrical insulation
Carry out phagocytosis
Nerve regeneration

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5
Q

What is the myelin sheath

A

Covering an axon made up of the membrane of a schwan cell
Rich in the lipid myelin

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6
Q

What is the node of ranveir

A

Between schwan cells where there is no myelin sheath

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7
Q

What is the direction of flow along a neurone

A

From dendrite to axon

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8
Q

Why does the cell body of a neurone have lots of RER Golgi body and mitrochondria

A

ATP for moving neurone transmitter vesicle down to synaptic knob

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9
Q

What’s the difference between a sensory neurone and motor neurone

A

Sensory - cell body above axon
Motor - cell body in between axon

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10
Q

Differences between nervous and endocrine system

A

Nervous
Uses impulses
Very rapid
Travels to spesific parts of the body
Localised
Short lived

Endocrine
Hormones
Transmissions in the blood plasma
Slow
Travels around the body but targets cells
Wide spread
Long lasting
Slow

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11
Q

Describe the resting potential

A

3 NA+ are actively pumped out of axon and 2 K+ into axon by sodium potassium pump so more NA+ in the tissue fluid and more K+ in the cytoplasm creating an electrochemical gradient

Due to the gradient NA+ diffuses in and K+ out

Most of the voltage gated sodium channels are closed but potassium ones are open so K+ diffuses out faster than sodium moving in

Tissue fluid becomes possitively polarised and cytoplasm becomes negatively polarised causing some k+ diffuses back into cytoplasm

Equilibrium is reached

Electrochemical gradient is balanced and resting potential is established

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12
Q

Describe the action potential

A

NA+ channels are open and sodium moves in by facilitated diffusion
If enough NA+ enters the threshold is reached and more gated channels open

Depolarisation

Action potential - at 40mv NA+ shut and K+ open
Proton motive force makes K+ leave

Hyperpolarisation - all channels close but too many potassium leave so cell overshoots resting potential

Sodium potassium pump moves NA+ out and K+ in reestablishing resting potential

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13
Q

Describe action potential passage in the myelinated neurones

A

A stimuli to threshold causes sodium channels to open. Sodium ions diffuse down the concentration gradient to enter the axon. Action potential reached. The axon membrane is depolarised.
The first action potential causes the opening of the sodium voltage gated channel further along the axon. This is positive feedback. It causes a new action potential and depolarisation.
Behind this region the sodium voltage gates closed and potassium opened

Action potential is regenerated for the 3rd time and the 1st area is returning to its resting potential

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14
Q

What is saltatory conduction

A

Jumping of action potentials between nodes along the axon

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15
Q

What is the refractory period

A

Minimum intervals between action potential and therefore between impulses

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16
Q

What is depolarisation

A

Temporary reversal of charges across the cell membrane of a neurone that occurs what a nerve impulse is transmitted

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17
Q

Structure of a myelinated neurone

A

Axon is wrapped in a lipid rich layer fatty sheath called myelin
Myelin is made from schwan cells
No action potential is generated in the myelin so it only happens at the node of ranveir

18
Q

What is the all or nothing principle

A

What a nerve is stimulated at the synapse Some NA+ ion channels open - NA+ ions diffuse in

If it is below threshold - no action potential
If it is above threshold - rapid opening of NA+ channels so action potential made

19
Q

How does temperature change speed of propagation

A

Higher temp gives ions more kinetic energy so they diffuse quicker

20
Q

How does myelination effect speed of propagation

A

Action potential travels faster in myelin because it only occurs at the node of ranveir so they jump myelinated area

21
Q

How does size effect speed of propagation

A

Width of the axon - larger diameter leads to quicker transmission

22
Q

What is the refractory period

A

Once an action potential has been created there is a period is afterwards when further inward movement of sodium ions us prevented because sodium voltage gated channels are closed
No action potential can be generated

23
Q

What is the purpose of the refractory period

A

Ensuring action potential is only propagated in 1 direction ( they can only move forward)

Ensuring that action potentials are discrete impulses (gaps)

Limits the number of action potentials in a given time so there can be gaps so stimuli is detected

24
Q

What is a synapse

A

The place where the axon of one neurone connects with the dendrite of another or with an effector

25
Q

Describe how information crosses a synapse

A

Impulses cause calcium ion channels to open and they diffuse into the synaptic knob
Vesicles move towards and fuse with the presynaptic membrane
Acetylcholine diffuses across synaptic cleft
It binds with receptor on sodium ion channels in the post synaptic membrane
Sodium ion channels open and they diffuse into the postsynaptic neurone
Depolarisation of postsynaptic membrane
If it is above threshold an action potential is produced

26
Q

How doe a synaptic knob reset

A

Calcium ions are removed from the synaptic knob by active transport which uses atp produced in the mitochondria. This makes sure the conc of calcium is always higher outside the membrane
Acetylcholine is removed from receptors by acetylcholineterase which hydrolyses acetylcholine which diffuses back into the synaptic knob
Acetyl and choline are synthesised to make acetylcholine to be used in the vesicles again

27
Q

What is summation

A

Rapid build up of neurotransmitters in the synapse by either:

Temporal summation - single presynaptic neurone releases neurotransmitters many times

Spatial summation - simultaneous stimulation by several presynaptic neurones

28
Q

Why summation

A

Prevents overstimulation
Synapses act as a barrier
Magnifying lots of small stimuli together

29
Q

Describe inhibition

A

Presynaptic neurone releases a neurotransmitter that causes opening of potassium channels, this means potassium diffuses out of the cell body so sodium ions diffusing in aren’t enough to reach threshold

Presynaptic neurone realise neurotransmitter which binds to chloride ions opening the channels so chloride diffuses into the cell body making the inside more negative so sodium ions are not enough to reach threshold

30
Q

Name the parts of the muscle

A

Tendon
Muscle
Bundle of muscle fibre
Connective tissue
Sheath muscle fibre
Myofibril

31
Q

Parts of a skeletal muscle fibre cell

A

Myofibrils, mitrochondria , sarcolemma , sarcoplasmic , nucleus , sarcoplasm

32
Q

What are the advantages of muscle fibres being multinucleated

A

Muscle mainly made of protein
Protein synthesis all the way along
Produces MRNA

33
Q

Describe the myofibril structure

A

Actin thin filament - tropamin , tropmyosin
Myosin thick filament

34
Q

Parts of a single myofibril and how they act on contraction

A

I band - shrinks
A band - stays the same
Z line
H zone - shrinks

35
Q

Why is it good that there are lots of neuromuscular junctions

A

Fibres can contract simultaneously and movement is fatser

36
Q

Structure and role of myosin

A

Heads protrude
Tail wraps around to form a filament

Does the power stroke and contains atp hydrolase

37
Q

Structure and role of actin

A

Long chains of globular proteins which are coiled into a helix
Tropinin is where calcium binds
Tropomiosin - threat wound around an actin

Allows myosin to bind

38
Q

What is the role of calcium ions

A

Changes tropomyosin position and uncovers myosin binding site
Activates myosin atp hydrolase

39
Q

What is the role of atp

A

Release of myosin head from actin binding site - breaking cross bridges

40
Q

What is the role of phosphocreatine

A

Phosphorylase’s atp from adp

41
Q

Describe muscle stimulation

A

Action potential arrives at neuromuscular junction and calcium channels open
Calcium diffuses into the synaptic knob
Vesicles move towards the presynaptic membrane
Acetylcholine is released into the neuromuscular cleft
Acetylcholine diffuses across cleft and binds with receptors in the sarcolema
Sodium channels open and sodium diffuses in
Sarcolema becomes depolarised
If threshold is reached action potentials spread to T tubules which are in contact with the sarcoplasmic reticulum
Calcium ions are released

Calcium binds to troponin causing tropomyosin to move exposing myosin bind site
Myosin head binds to actin forming cross bridges
Power stroke occurs ( myosin head swivels pulling actin over myosin)
ATP binds to myosin head and breaks the cross bridge
ATP hydrolase hydrolyses atp to adp + pi causing myosin head to recock
Myosin head binds to actin
Another power stroke
If calcium is present the process carries on

biology (19 decks)

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