Introduction to the CNS

Question 1

What is the difference between human and animal brain topology?

Answer 1

The human brain is rotated 90 degrees relative to animal brain, so that caudal is no longer posterior and is instead perpendicular to rostral towards the end of brainstem.

Question 2

What are the parts of the brain?

Answer 2

1. Forebrain (telencephalon)
2. Midbrain (mesencephalon)
3. Hindbrain (rhombencephalon)

Question 3

What are the different parts of the forebrain?

Answer 3

1. Telencephalon: Thalamus & hypothalamus.
2. Diencephalon: Cerebral cortex & deep nuclei.

Question 4

What are the different parts of the hindbrain?

Answer 4

1. Cerebellum
2. Pons
3. Medulla

Question 5

What are the different parts of the brainstem?

Answer 5

1. Midbrain
2. Pons
3. Medulla

Question 6

What is the corpus callosum?

Answer 6

Thick bundle of axons running between and connecting the 2 cerebral hemispheres.

Question 7

What are the functions of the brain?

Answer 7

1. Sensory: Detection of the external environment.
2. Motor: Response to the external environment.
3. Association:
   - Association of different sensory information to build more representative image of external environment.
   - Association of sensory information with past experience to make better prediction of appropriate response.

Question 8

What are the sensory modalities?

Answer 8

1. Vision
2. Hearing
3. Somatosensation
4. Proprioception
5. Taste & olfaction

Question 9

What are the characteristics of sensory stimuli that need to be detected by sensory organs?

Answer 9

1. Modality of stimulus: Usually by type of receptor activated (labelled line).
2. Intensity of stimulus
3. Location
4. Duration: Usually intrinsic property of stimulus itself (I.e. When it starts and ends).

Question 10

What techniques may be applied to study the brain and CNS?

Answer 10

1. Observation (non-invasive): Using imaging techniques such as fMRI and x-ray to correlate structures with functions.
2. Stimulation (invasive): Using electrodes to stimulate parts of the brain (e.g. during surgery) and oberving consequences.
3. Recording (invasive/non-invasive): Using EEG or electrodes to record direct electrical activity of neurones in the CNS on different stimulation in order to determine function.
4. Lesions (invasive/non-invasive): Studying the functional losses of patients with lesions in specific areas of the brain.
5. Experimental interference (invasive): Using specific experimental techniques in animal models to interfere with CNS function such as:
   - Purposely destroying parts of the brain.
   - Using pharmacological substances that disrupt CNS function.
   - Genetic alterations that compromise development of parts of the brain.

Question 11

What embryological structure do all CNS structures derive?

Answer 11

Neural tube

Question 12

Which neuronal characteristics in the CNS determine function?

Answer 12

1. Morphology: Arrangement of neurones and connections within the CNS.
2. Timing & patterns: The timing and pattern of neuronal APs is also fundamental to CNS signalling.
3. Synaptic transmission: Type of NT used and structure of synapse determines properties of synpase, which is also fundamental to CNS function.

Question 13

Which neurotransmitters mediate CNS synaptic transmission?

Answer 13

Excitatory:

• Glutamate

Inhibitory:

• GABA
• Glycine

Question 14

What are the types of association?

Answer 14

• Unimodal: Association involving only one sensory cortex.
• Multinodal: Association