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Anatomy > Anatomy - Nervous system > Flashcards

Anatomy - Nervous system Flashcards

1
Q

What is the study of the nervous system called

A

Neuroscience

Neurobiology

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2
Q

What is the function of the nervous system

A

Homeostasis and coordination. It employs electrical impulses and chemical means to send messages very quickly from cell to cell

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3
Q

How many neurons are there in the body

A

10^12

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4
Q

nervous system vs endocrine system

A

The nervous system communicates by means of electrical impulses and neurotransmitters while the endocrine system communicates by means of hormones.

The nervous system releases neurotransmitters at synapses at specific target cells while the endocrine system releases hormones into the bloodstream for general distribution throughout body.

The nervous system usually has relatively local, specific effects while the endocrine system sometimes has very general, widespread effects.

The nervous system reacts quickly to stimuli, usually within 1-10 msec while reacts mores slowly to stimuli, often taking seconds to days.

The nervous system stops quickly when stimulus stops while the endocrine system may continue responding long after stimulus stops.

The nervous system adapts relatively quickly to continual stimulation while the endocrine system adapts relatively slowly; may respond for days to weeks

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5
Q

How are the endocrine system and the nervous system related

A

They are both involved in homeostasis and coordination but operate in different ways

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6
Q

What are the major subdivisions of the nervous system

A

Central nervous system (CNS)

Peripheral nervous system (PNS)

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7
Q

What does the Central nervous system include and how is it protected

A

The brain and spinal cord which are protected by the cranium and the vertebral column

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8
Q

What is the peripheral nervous system

A

Everything other than the brain and spinal cord so the nerves and their associated ganglia.

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9
Q

What types of nerves are there

A

The spinal nerves, which emanate from the spinal column.

The cranial brain, which emanate directly from the brain. (There are 12 pares of cranial nerves).

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10
Q

What is a neuron

A

An electrically excitable cell that we find in the nervous system, they have projections called axons.

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11
Q

What is a nerve

A

A bundle of nerve fibres, axons, unwrapped in fibrous connective tissue.

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12
Q

What is ganglion

A

A knot-like swelling in a nerve where the cell bodies of neurons are concentrated (e.g. dorsal root ganglia)

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13
Q

What is the central nervous system divided into

A

Brain and Spinal cord

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14
Q

What further subdivisions is the peripheral nervous system divided into

A

Sensory division (afferent) and motor division (efferent)

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15
Q

Sensory or affarent division

A

carries sensory signals from receptors to the CNS.

The somatic sensory division carries signals from receptors in the skin, muscle bone and joints. And the visceral sensory division carries signals from viscera of the thorax and abdominal cavities (e.g. heart, lungs and stomach)

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16
Q

Motor or efferent division

A

carries signals from the CNS to the glands and muscle cells (effectors).

The somatic motor division carries signals to the skeletal muscle for voluntary contractions and involuntary somatic reflexes. The visceral (autonomic system) motor division carries signals to the glands, cardiac muscle, smooth muscle for involuntary visceral reflexes.

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17
Q

What are the subdivisions of the Autonomic nervous system

A

The sympathetic and the parasypathetic division

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18
Q

sympathetic division

A

tends to arouse the body for action, so its excitatory (increase heart and respiratory rates), but it also inhibits digestion.

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19
Q

parasympathetic division

A

tends to be inhibitory, so it has a calming effect ( slows down the heart rate), but it stimulates digestion.

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20
Q

What are the three properties of neurons

A

Excitability (irritability) - all cells are excitable, they respond to stimuli, but neurons have developed this to the highest degree.

Conductivity (electrically conductive) - stimuli produce electrical signals in neurons that are conducted to other cells at distant locations.

Secretion (they are secretory) - electrical signals at the end of nerve fibres cause the release of chemical neurotransmitters at synaptic knobs.

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21
Q

What types of neurons is there

A

Sensory (afferent)(PNS)
Motor (efferent)(PNS)
Interneurons (association or relay neurons)(CNS)

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22
Q

Sensory neurons

A

detect signals and carry then towards the central nervous system.

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23
Q

Motor nuerons

A

carry signals away from the central nervous system to muscle and glands.

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24
Q

Interneurons

A

connect sensory and motor neurons, they process store and retrieve information and make decisions.

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25
Q

What is the main type of neuron

A

Interneurons 90 %

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26
Q

soma
neurosoma
perikaryion

A

It is 5 to 135 micro meters in diameter. It is the cell body.

27
Q

The cytoskeleton of the neuron

A

The cytoskeleton includes microtubules and neurofibrils (actin) and it lacks centriols because neurons are non-mitotic (after adolescence)

28
Q

What are nissl bodies

A

Nissl bodies are concentrated areas of endoplasmic reticulum and ribosomes, which specialise in protein synthesis.

29
Q

About dendrites

A

Dendrites receive signals. At the end of these are post-synaptic membranes; the dendrites converge into the soma.

30
Q

About axon hillocks

A

hillocks is the region in which the soma converges to give rise to axons.

31
Q

The axon nerve fibre

A

is 1-20 micro metres in diameter and a few millimetres to 1 meter in length. They allow rapid conduction of nerve signals. The axon can have collateral axons and they have terminal arborisations ending in synaptic knobs.

32
Q

How is the neuron’s cytoplasm called

A

axoplasm

33
Q

How is the neuron’s membrane called

A

axolemma

34
Q

What are Schwann cells

A

They are regions of the axons in PNS that are electrically insulated by myelin sheaths. They increase the conductivity of the cell.

35
Q

What are the nodes of Ranvier

A

They are the spaces between the Schwann cells, also called internodes.

36
Q

What are the support cells called and how many are there

A

Neuroglia

50 x 10^12

37
Q

What are the four types of neuroglia in the central nervous system

A

Oligodendrocytes
Ependymal cells
Microglia
Astrocytes

38
Q

What are the two types of neuroglia in the peripheral nervous system

A

Schwann cells

Satellites cells

39
Q

What is the function oligodendrocytes

A

They form myelin in brain and spinal cord, they are equivalent to Schwann cells in the central nervous system

40
Q

What is the function of Ependymal cells

A

They line cavities of brain and spinal cord; they secrete and circulate cerebrospinal fluid-

41
Q

What is the function of Microglia

A

Phagocytise and destroy microorganisms, foreign matter, and dead nervous tissue

42
Q

What is the function of Astrocytes

A

They cover the brain surface and non-synaptic regions of neurons.

They form a supportive framework in the central nervous system.

They induce the formation of blood-brain barrier.

They nourish neurons.

They produce growth factors that stimulate neurons.

They communicate electrically with neurons and may influence synaptic signaling.

They remove potassium and some neurotransmitters from the extracellular fluid of the brain and spinal cord-

They help to regulate the composition of the extracellular fluid.

They scar tissue to replace damaged nervous tissue.

43
Q

What is the function of Schwann cells

A

Form neurilemma around all the peripheral nervous fibers and myelin around most of them; and they aid in regeneration of damaged nerve fibers.

44
Q

What is the function of the Satellites cells

A

They surround somas of neurons in the ganglia; they provide electrical insulation and regulate the chemical environment of neurons.

45
Q

What does myelination do

A

It provides insulation along axons. Increase nerve conduction speed by, approximately, an order of magnitude (a factor of 10).

A 2-4 micrometers in diameter unmyelinated fibre can conduct an electrical signal with a speed of half a meter to two metres per seconds, but a myelinated, 3 to 15 metres per second.

46
Q

What cells myelinate the PNS cells and how

A

Schwann cells

spiral outwards

47
Q

What cells myelinate the CPS cells and how

A

Oligodendrocytes

spiral inwards

48
Q

What is the membrane potential

A

It is the potential difference between the intercellular fluid (ICF) and extracellular fluid (ECF).

49
Q

What is the resting membrane potential

A

It is the potential difference at the rest state of a cell. fir electrically active cells it is non-zero and negative.

50
Q

What is the typical resting membrane potential of neurons

A

-70mV

51
Q

How is the resting membrane potential originated

A

The membrane is most permeable to potassium.

If there was only potassium in the intra-cellular fluid at the start, this would diffuse out down to a concentration gradient.

Non-diffusable anions in intracellular fluid attracts potassium back.

At equilibrium, the potassium is 40 times more concentrated in the intracellular fluid than extracellular fluid; this gives a RMP of -90mV.

Sodium is twelve times more concentrated in ECP than ICF, this diffuses down the concentration gradient into the cell and reduces negative charge in ICF, which gives a resting membrane potential of -67mV.

Therefore, potassium leaks out and sodium leaks in.

A Na-K pump consumes one ATP to pump 3 na out and 2 Na in, which contributes -3mV to the RMP.

this accounts for 70 percent of the energy requirements of the nervous system.

The net effect fives a resting membrane potential of -70 mV.

52
Q

How is the local membrane potential triggered

A

Chemical messengers neurotransmitters impinge on the receptors in the dendrites of the neuron which leads to the opening (or closing) of the ion channels. (on the unbound state it is closed and in the bound state it is open.

53
Q

How does depolarisation happens

A

The sodium ions flow into the cell causing the membrane potential to become less negative, so an increase in the local transmembrane voltage happens.
This is excitatory.

54
Q

How does repolarization happens

A

When potassium ions, which are concentrated inside the cell, flow out of the membrane, it leads to a decrease in the transmembrane voltage.
This is inhibitory.

55
Q

What has to happen for an action potential to take place

A

The current that travels to the soma needs to reach a threshold value.

56
Q

What are the events of the action potential

A

The sodium ions arrive at the axon hillock and cause a depolarisation.

The membrane potential rises above -55 mV, the threshold value.

The voltage-regulated sodium gates open quickly and sodium flows into the cell to cause a rapid depolarisation, meanwhile potassium gates also open, but slower.

At 0 mV, sodium gates close, and at 35 mV the maximum depolarisation is reached.

Now potassium gates are fully opened and moves out of the cell to cause repolarization.

More potassium leaves than sodium enters so hyperpolarization occurs.

Membrane potential is restored to resting membrane potential.

57
Q

What is the refractory period

A

It is a period of resistance to stimulation. During absolute refractory period that section of the neuron cannot have another action potential happening and uring the relative refractory period, the membrane is hyperpolarized so it would take higher excitatory input to trigger another action potential.

58
Q

How does the signal travels along the axon

A

The signal travels unidirectionally along the axon by diffusing sodium ions into the next part of the neuron causing it to reach threshold and triggering an action potential. Backwards the neuron will still be in the refractory period so the action potential won’t be triggered again in this direction and the signal will travel forwards.

59
Q

Myelinated axonal conduction

A

In the internodes the action potential cannot happen because the Myelin sheath is isolating the axon in Schwann cells. Therefore, the action potential travels only at the nodes of Ranvier in what is called saltatory conduction. By missing out on big chunks of axonal length, the speed of conduction is faster, so myelinated neurons have a higher conduction.

60
Q

What else affects the conductivity of axons

A

The thicker the more conductive.

61
Q

How does synaptic transmission happen

A

When the electrical signal reaches the terminal arborisations and synaptic knobs, it triggered the influx of calcium by opening voltage-gated calcium channels and the calcium causes the exocytosis of neurotransmitter vesicles.

These then then bind with pre-synaptic the membrane and release the neurotransmitter into the synaptic cleft, to then impinge on the receptors in the post-synaptic membrane.

62
Q

How many types of neurotransmitters are there in the body

A

More than 100

63
Q

First example of how neurotransmitters act

A

The neurotransmitter binds to sodium channels, sodium flows into the post synaptic cell causing the depolarisation of the cell; if it binds to potassium ligand-gated channels, potassium flows out causing repolarization.

64
Q

Seconds example of how neurotransmitter act

A

The neurotransmitter can use noradrenaline, which when bind to its receptor, it dissociates into two parts. the G-protein bit binds to an adenylate cyclase enzyme which converts ATP to cyclic AMP when activated. When the concentration of cyclic AMP goes up inside the cell it causes whatever effect.

Anatomy (10 decks)

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