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BDS 2: Foundation Basic Sciences > L9 Introduction to the Nervous System > Flashcards

L9 Introduction to the Nervous System Flashcards

1
Q

What does the brain weigh?

A

1.5kg

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2
Q

How many neurons does the brain contain?

A

Approximately 1 billion

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3
Q

How metabolically active is the brain?

A

Highly metabolically active

  • 15% of body’s total blood supply
  • 20% of body’s total oxygen supply
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4
Q

Describe the structure of a typical CNS neuron.

A
  • Soma (cell body) containing a nucleus
  • Dendrites (branched neuronal processes)
  • May have basal and apical dendritic trees
  • One axon
  • Terminal branching axons with axon terminals
  • Synaptic bouton in close contact with post-synaptic dendrite
  • Syanptic cleft between bouton and dendrite
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5
Q

What are the 2 categories of synapses?

A
  • Chemical

- Electrical

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6
Q

Describe a chemical synapse.

A
  • Bouton containing synaptic vesicles
  • Vesicles contain neurotransmitters which diffues across synaptic cleft and bind to receptors on post-synaptic dendritic membrane
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7
Q

What is the difference between excitatory and inhibitory neurotransmitters?

A

Excitatory: cause depolarisation of the post synaptic neuron, increasing likelihood of AP firing from post synaptic neuron e.g. acetylcholine and glutamate

Inhibitory: cause hyperpolarisation of the postsynaptic neuron, making it less likely that an AP will be fired from the post synaptic neuron e.g. GABA and glycine

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8
Q

What is grey matter?

A
  • Found closer to the borders of the brain
  • Grey matter = nuclei
  • Nuclei = a cluster of neuron cell bodies and their dendrites
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9
Q

What is white matter?

A
  • Found closer to the inside of the brain

- White matter = bundles of myelinated axons that form fibre tracts connecting nuclei

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10
Q

Where are grey and white matter found in the spinal cord?

A
  • Gray matter in inner butterfly shaped region (divided into dorsal horn, intermediate zone and ventral horn)
  • White matter surrounds grey matter (is the axons of the neurons in the grey matter)
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11
Q

What are the 3 neuron types?

A
  • Motor
  • Sensory
  • Interneuron
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12
Q

Describe motor neurons.

A
  • Cell body in ventral horn of grey matter
  • Single basal axon which passes through ventral root
  • Ventral root coalesces with dorsal root to give rise to segmenral spinal nerve
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13
Q

Describe sensory neurons.

A
  • Cell body in the dorsal root ganlgion
  • 1 axon projects into segmental spinal nerve makes synaptic connection with target tissue (e.g. skin)
  • 1 axon projects centrally into dorsal horn of grey matter where it synapses with motor or interneuron
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14
Q

Describe interneurons.

A
  • Connects neurons
  • Relays info between sensory and motor neurons
  • Axons project into white matter to make connections with neurons in higher regions of the brain
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15
Q

What are the 2 types of interneuron?

A
  • Local circuit interneurons: short axons which remain in the nucleus and connect with nearby neurons
  • Projection interneurons: send their axons along fibre tracts to other nuclei (can be over a metre long)
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16
Q

What is the other major cell type in the nervous system?

A

Glial cells

17
Q

What are the 3 types of glial cells?

A
  • Oligodendrocytes
  • Astrocytes
  • Microglia
18
Q

Describe oligodendrocytes.

A
  • Myelinating cells
  • Form the myelin sheath
  • Project processes that wrap around the axon

In the peripheral NS, the equivalent cell type is a Schwann cell.

19
Q

Describe astrocytes

A

Large star shaped cells with many processes and roles:

  • Regulate extracellular ion concentrations around neurons (essential to maintaining resting potential)
  • Processes wrap around synapses to regulate neurotransmitter reuptake and degradation
  • Structural support
  • Regulate integrity of blood-brain barrier
  • Neurotrophic support/nutritive role
20
Q

Describe microglia.

A
  • Small glial cells
  • “Immune system of the brain”, equivalent role in the brain as leukocytes in the periphery
  • Release inflammatory cytokines to attack disease organisms and phagocytose damaged cells
  • Inappropriately activated microglia play a role in pathological pain and contribute to the onset of some neurogenerative diseases e.g. Alzheimer’s
21
Q

What are the 2 main neuron types of the peripheral nervous system?

A
  • Peripheral sensory neurons

- Autonomic neurons: neurons of the sympathetic, parasympathetic and enteric nervous systems

22
Q

Describe the anatomy of the peripheral nervous system.

A
  • 30 segmental spinal nerves which project from either side of the spinal cord
  • C1-C8 = cervical nerves
  • T1-T12 = thoracic nerves
  • L1-L5 = lumbar nerves
  • S1-S5 = sacral nerves
23
Q

How are the segmental spinal nerves formed?

A

By the coalescence of the ventral and dorsal roots.

24
Q

What are dermatomes?

A

The areas of skin suplied by the dorsal root ganlgion neuron associated with each segmental spinal nerve (sensory innervation).
Do not have sharp boundaries.

25
Q

What is the corpus callosum?

A

The fibre tract containing axons of neurons in the left or right hemisphere, this is where axons cross from one hemisphere to the other.

26
Q

What are the components of the forebrain?

A
  • Neocortex: largest part, centre of higher order brain functions
  • Thalamus: relay for sensory and motor info between the cortex and lower levels of the nervous system
  • Hypothalamus: autonomic and endocrine control
  • Basal ganglia
27
Q

What are the components of the midbrain?

A
  • Tectum: roof of midbrain, contains nuclei important in visual and auditory reflexes
  • Tegmentum: contains motor nuclei for cranial nerves III and IV, and nuclei for parts of reticular formation
28
Q

What are the components of the hindbrain?

A
  • Pons and medulla: reticular formation and cranial nerve nuclei
  • Cerebellum: control of motor function
29
Q

What is the reticular formation?

A

A complex network of brainstem nuclei and neurons that serve as a major integration and relay center for many vital brain systems to coordinate functions necessary for survival.

30
Q

Describe the basal ganglia.

A 
Controls movement by regulating output from motor and motor areas of the cortex.
Composed of:
- Caudate nucleus
- Putamen
- Globus pallidus
- Subthalamic nucleus
- Subthalamic nigra
31
Q

Provide an overview of the cranial nerves.

A
  • Arise from the brain stem
  • Carry info to and from the brain from the head and visceral organs
  • 12 pairs
  • Special senses, control of muscles of face, control of pharynx and larynx, sensation to the face and some visceral organs
32
Q

What is the major groove through the middle of the cortex called?

A

The central sulcus

33
Q

What are the primary sensory and motor areas of the cortex?

A
  • Primary motor cortex: immediately infront of central sulcus, contains cell bodies of motor neurons, controls muscle contraction
  • Primary sensory cortex: immediately behind central sulcus, first area to recieve somatosensory info
  • Primary visual cortex: at back of occipital lobe, first area to recieve visual info
  • Primary auditory cortex: recieves auditory info

BDS 2: Foundation Basic Sciences (18 decks)

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