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Neurology > Cells and tissue of the nervous system > Flashcards

Cells and tissue of the nervous system Flashcards

1
Q

What are the divisions of the nervous system?

A

CNS (brain and spinal cord) –> PNS (spinal and cranial nerves) –> sensory (afferent) and motor (efferent)

Motor (efferent) –> somatic (voluntary) and autonomic (involuntary)

Autonomic (involuntary) –> sympathetic and parasympathetic

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2
Q

What are the 2 main cell types?

A

1) Neurons: structural and functional unit; excitable cells; impulses carried as AP’s
2) Glial cells: non-excitable supporting cells that are much smaller than neurons

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3
Q

In which direction do impulses travel down a neuron?

A

From cell body to synaptic terminal.

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4
Q

What happens long term if a neuron is damaged?

A

Axons can grow back if they are damaged - lots of ER in the cytoplasm so can make new proteins etc.

However, if the neuronal cell body in the spinal cord is damaged this is irreversible.

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5
Q

What are the 2 main forms of neurons?

A

Sensory (dorsal) or motor (ventral).

Sensory neurones have their cell bodies outside of the CNS in the dorsal root ganglion of the spinal cord.

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6
Q

What is the function of the myelin sheath in axons?

A

To increase conduction speed in axons by saltatory conduction - ion flow only occurs at the nodes of Ranvier which are the spaces between the myelin cells. Neurons can be myelinated or non-myelinated.

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7
Q

Which cells form the myelin sheath in the CNS and PNS?

A

Oligodendrocytes in the CNS.

Schwann cells in the PNS.

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8
Q

How do Schwann cells myelinate axons in the PNS?

A

They wrap themselves around axons to form a mesaxon - the cytoplasm of the
Schwann cell gets extruded and only the cell membrane remains.

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9
Q

What is in the white and grey matter of the CNS?

A

White matter - myelinated axons.

Grey matter - cell bodies.

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10
Q

What is seen in axons in MS?

A

Patchy loss/scarring of the myelin sheath (demyelination). This leads to abnormal nerve conduction across affected axons.

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11
Q

What are the 2 types of multipolar neurons??

A

1) Motor neurones

2) Interneurones (transmits impulses between other neurons, especially as part of a reflex arc)

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12
Q

What are the 2 types of bipolar neurons?

A

1) Olfactory mucosa

2) Retinal nerve fibres

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13
Q

Which neurons are pseudounipolar?

A

Sensory neurons - one branch runs to the periphery and one to the spinal cord (the axon has split in 2).

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14
Q

Where are the cell bodies of motor neurones?

A

The ventral horn of the spinal cord.

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15
Q

In the PNS, where do white and grey matter go?

A

White matter - myelinated axons form nerves.

Grey matter - cell bodies form ganglia

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16
Q

In the CNS, where do white and grey matter go?

A

Collections of myelinated axons form white matter (diffuse) or tracts (bundles of axons carrying specific info in the white matter).

Cell bodies and non-myelinated axons form grey matter (diffuse) or nuclei (localised)

17
Q

What happens when cutaneous receptors in the skin sense pain?

A

A pseudounipolar sensory neuron travels through the dorsal root ganglion and ascends via white fibre tracts to the brain where it reaches a collection of neuronal cell bodies (nucleus).

18
Q

How many types of glial cells are there?

A

6 different types - astrocytes are the most common.

19
Q

What does the diencephalon contain?

A

Thalamus, hypothalamus and pituitary gland (posterior).

20
Q

Describe neural tube formation.

A

The top layer of the embryo (surface ectoderm) has thickened by day 18 - this is the neural plate) This thickens further, folds over and becomes the neural tube.

Neural tube divides into 3 primary vesicles in weeks 4, then into secondary vesicles in week 5. These develop into the adult brain.

21
Q

What happens to the forebrain?

A

There are 2 secondary vesicles formed:

  • Telencephalon which becomes the cerebrum
  • Diencephalon which the eyes develop from (optic cups at either side)
22
Q

Which structures come from the hindbrain?

A

Cerebellum and brainstem.

23
Q

Where do the ventricles of the adult brain arise from?

A

The neural tube has a cavity which persists in the adult brain. This cavity becomes a series of interconnected ventricles.

24
Q

What do the ventricles contain?

A

CSF

25
Q

Where are the lateral ventricles?

A

These are C-shaped cavities that lie in the cerebral hemispheres.

26
Q

Which structure connects the lateral ventricles to the 3rd ventricle?

A

The interventricular foramen of Munro.

27
Q

Where does the 3rd ventricle lie?

A

Within the diencephalon.

28
Q

What is the cerebral aqueduct?

A

Connects the 3rd ventricle with the 4th ventricle.

29
Q

Where does the 4th ventricle lie?

A

In the hindbrain. It is diamond-shaped.

30
Q

What are the 3 meninges?

A

1) Dura mater - outermost layer; tough, fibrous and has dural folds
2) Arachnoid mater - middle layer
3) Pia mater - innermost layer; vascularised and dips into the folds of the brain

31
Q

What does the subarachnoid space contain?

A

CSF

32
Q

What is the subdural space?

A

A potential space between the dura and arachnoid mater - they can be separated in trauma and blood can collect here (subdural haematoma).

33
Q

Where is CSF produced?

A

The choroid plexus of the ventricles (mainly lateral ventricles as they are the biggest).

34
Q

How is CSF reabsorbed into the venous circulation?

A

Via arachnoid granulations which are present in the dural sinuses of the brain.

35
Q

How are drugs delivered to the CNS?

A

They need to cross the BBB - need to be lipid soluble or use a suitable vector.

36
Q

What is the function of the BBB?

A

Maintains homeostasis in the brain parenchyma to protect the brain from harmful AA’s/ions that are present in the blood stream.

37
Q

What makes up the BBB?

A

Endothelium - tight junction

Thick basal lamina

Foot processes of astrocytes

38
Q

Where is the BBB absent?

A

In a few circumventricular organs - parts of the hypothalamus and posterior pituitary.

Neurology (23 decks)

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