Nervous Coordination And Muscles Flashcards

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1
Q

Describe the cell body

A
  • includes usual cell organelles, nucleus, lots of rough endoplasmic reticulum
  • associated with the production of proteins and neurotransmitters
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2
Q

Describe dendrons

A

Extensions if the cell body which subdivide into smaller branched fibres= dendrites ,that carry nerve impulses towards the cell body

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3
Q

Describe the axon

A

A single long fibre that carries nerve impulse away from the cell body

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4
Q

Describe schwann cells

A

Surround the axon
Protects axon
Provides electrical insulation
Also carries out phagocytosis
Plays a part in nerve regeneration
Wrap around axons many times= layers

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5
Q

Describe the myelin sheath

A

Forms a covering to the axon
Is made up of membranes of the schwann cells
Rich in the lipid myelin
Neurones with a myelin sheath= myelinated neurones

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6
Q

Describe the nodes of ranvier

A

Constrictions between adjacent schwann cells where there is no myelin sheath
Constrictions are 2-3um long
Occur every 1-3mm in humans

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7
Q

Describe sensory neurones

A

Transmit nerve impulses from a receptor to CNS or an intermediate neurone
Their cell body usually appears to be an extension of the axon

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8
Q

Describe intermediate neurones

A

Lots of dendrites both sides, in order to propagate an impulse between 2 neurones

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9
Q

Compare the endocrine and nervous system

A

Endocrine:
> uses hormones
> transmission is by neurones
> transmission is very rapid
> involves chemicals that travel to specific parts of the body
> response is localised
>response is rapid
> response is short lived
>effect usually temporary & reversible

Nervous system:
< wired and uses nerve impulses
< transmission is by the blood stream
< transmission is usually relatively low
< response is widespread
< response is long lasting
< response is slow
< effect may be permanent & irreversible

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10
Q

Give an example of the nervous system

A

Reflex action : eg.withdrawal of half from unpleasant stimulus

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11
Q

Give an example if the endocrine system

A

Control of blood glucose concentration

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12
Q

Describe the process of resting potential

A
  1. Three Na+ are actively pumped out of the axon and two K+ are actively pumped into the axon by the Na+/K+ pump
  2. As a result,there are more Na+ in the tissue fluid than the cytoplasm,and there are more K+ in the cytoplasm than in the tissue fluid- an electrochemical gradient is formed
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13
Q

Describe the action potential

A
  1. At the resting potential,voltage gated Na+ channels are shut. Some of th voltage gated K+ channels are open, but most are closed
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14
Q

Describe the passage of action potential in unmyelinated neurones

A

Eg: autonomic nervous system
1. The resting potential
At resting potential the concentration of sodium ions out of the axon membrane is very high. The concentration of potassium ions inside the axon is lower (but higher than the potassium outside the axon). The outside of the axon is positive in relation to the inside. The axon membrane is polarised
2. Initiation of the 1st action potential

  1. Stimulus if the next action potential
  2. Repolarisation of the axon
  3. Returning to resting potential
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15
Q

Describe the passage of an action potential in myelinated neurones

A

Structure: the axon is wrapped in a lipid rich layer fatty sheath = myelin
The myelin sheath is made from highly specialised cells= schwann cells
The myelin sheath acts as an electrical insulator which prevents the passage of ions into and out of the axon
Therefore no action potential can occur in the area of myelination and can only occur at the nodes of ranvier.
They effectively jump from node to node along the nerve fibre
This method of action potential propagation is saltatory conduction

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16
Q

What is the all or nothing principle

A

When a nerve is stimulated at the synapse –> some Na+ ion channels open –> Na+ ions diffuse in

17
Q

If below threshold what happens

A

No action potential

18
Q

If above threshold what happens

A

Rapid opening of Na+ ion channels –> action potential

19
Q

Speed of nerve impulse

A

Once an action potential has been initiated at the start of the axon, the subsequent action potentials do not decrease in size. However the speed of propagation can vary and this depends on three properties of the axon

20
Q

Describe the sequence of events which allows information to pass from one neurone to the next neurone across the cholinergic synapse

A
  1. Impulses cause calcium ions channels to open and calcium ions diffuse into the synaptic knob
  2. Vesicles move towards and fuse with the presynaptic neurone
  3. Acetylcholine is released via exocytosis
  4. Acetylcholine diffuses across the synaptic cleft
  5. Acetylcholine binds with receptors on sodium ion channels in the post synaptic membrane
  6. Sodium ion channels open and sodium ions diffuse into the post synaptic neurone
  7. Depolarisation of postsynaptic neurone
  8. If above threshold,an action potential is produced
21
Q

What is temporal summation

A

One neurone releases neurotransmitter repeatedly over a short period of time to add up to enough to exceed threshold value

22
Q

What is spatial summation

A

Many different neurones connective trigger a new action potential by combining the neurotransmitter they released to exceed threshold value

23
Q

Why summation

A

Avoids the nervous system being overloaded
Synapses acts as barriers
Effect of a stimulus can be magnified
Eg: rod cells –> bipolar neurone-> ganglion cell-> synaptic nerve

24
Q

Describe the first way of inhibition (potassium ions)

A

Presynaptic neurone releases a type of neurotransmitter that causes opening of potassium protein channels on post synaptic neurone.
Opening of potassium channels –> diffusion of potassium ion out postsynaptic cell body
- greater potential difference across the membrane
-sodium ions diffusing in are not enough for post synaptic membrane to reach threshold

Outward diffusion of potassium ions ‘cancels out’ inward diffusion of sodium ions

25
Q

Descrive the second way of inhibition (chloride ions )

A

Presynaptic neurone releases a type of neurotransmitter that binds yo chloride ions protein channels on postsynaptic neurone

26
Q

Describe the skeletal muscle structure

A

Skeletal muscles act in antagonistic pairs against an incompressible Skelton
They are stimulated to contract by action potentials

27
Q

What is the myofibril structure

A

Myofibirils appear striped because of the way that actin and myosin protein filaments are arranged within them

28
Q

What is a sacromere

A

Actin and myosin filaments arranged