L1 (Neuroscience) General Structure of the CNS

Question 1

What are the CNS and PNS made up of?

Answer 1

CNS = brain + spinal cord, PNS = nerves + ganglia

Question 2

What structures make up the brain stem?

Answer 2

Midbrain, pons and medulla

Question 3

What does white & grey matter consist of?

Answer 3

White = axons + glia, grey = cell bodies (neural somata) + glia

Question 4

What is the basic gross structure of the cerebrum?

Answer 4

Two hemisphere split by a longitudinal fissure, surface is the cortex. Cortex has ridges (gyri/gyrus) and grooves (sulci/sulcus)

Question 5

What are the lobes of the cerebral cortex and what is there functional significance?

Answer 5

4 lobes; Frontal, parietal, temporal and occipital. Boundaries between lobes are not generally functionally significant. Boundaries between frontal & parietal lobes (central sulcus) and temporal and occipital lobes do respect function

Question 6

What is Brodmann’s Map (Areas) and what is its significance?

Answer 6

Mapping of cortex based on minute cellular differences - 52 areas. Areas often overlap with function (functionally significant) but not always

Question 7

Describe the cellular structure of the cerebral cortex

Answer 7

Superficial layer of grey matter (~1cm thick) covers the core white matter, wrapping around gyri and sulci. There are many neurons and they are in a layered structure (6 layers), with each layer containing different types of neurons (includes pyramidal and interneurons). The left and right cortices/hemispheres are linked at the corpus callosum

Question 8

What is the basic function of the cerebellum?

Answer 8

Key element in motor control, compares what you want to do with what you are doing - refines execution of motor program. Contains more than half the neurons of the brain

Question 9

What parts of the brain develop from the forebrain, midbrain & hindbrain?

Answer 9

The hindbrain = lower brainstem and cerebellum
The midbrain = the most rostral part of the brainstem
The forebrain = (region just rostral to the midbrain) forms the diencephalon which is surrounded by the telencephalon. Diencephalon + telencephalon = the cerebrum (All cerebral cortex is telencephalic)

Question 10

What makes up the diencephalon?

Answer 10

Thalamus & hypothalamus

Question 11

What is the telencephalon?

Answer 11

Cortex of the cerebrum

Question 12

What is the Basal Ganglia?

Answer 12

Group of interconnected sub-cortical nuclei (predominately found in the telencephalon but some between midbrain & hypothalamus) that are arranged around the thalamus.

• Corpus striatum (caudate & putamen)
• Globus pallidus
• Substantia Nigra
• Subthalamic nucleus

Question 13

What is the function of the basal ganglia?

Answer 13

Important in motor control - selects & initiates voluntary movements –> sends information to the cortex

Question 14

What are diseases of the basal ganglia?

Answer 14

Sends information to the motor cortex - therefore motor disorders. Parkinson’s & Huntington’s Disease

Question 15

What is the function of the thalamus?

Answer 15

Major sensory relay to cortex –> allows you to perceive

Question 16

Where is the thalamus found?

Answer 16

Part of the diencephalon with the hypothalamus. Sits in the middle of the brain

Question 17

What are the 3 pathways of thalamic sub-nuceli?

Answer 17

1. Sensory information –> specific areas of cortex
2. Non-sensory info from cortex & basal ganglia –> areas of cortex
3. Project globally to cortex –> arousal & sleep

Question 18

What is the function of the hypothalamus?

Answer 18

Central command centre for regulating homeostatic functions (i.e. temperature, blood volume, pH…)

Controls the pituitary gland (sits below it)

Question 19

What does the brainstem control?

Answer 19

• Facial muscles
• Sensation from head and face
• Cardiorespiratory control
• Arousal, sleep/wake cycle

Question 20

Describe the anatomy of the spinal cord?

Answer 20

Core of grey matter, surrounded by white matter (opposite to cortex)
Grey matter has ventral (anterior) and dorsal (posterior) horns that are separated by an intermediate zone.

Question 21

What are the functions of the dorsal and ventral horns of the spinal cord?

Answer 21

Dorsal (posterior) - sensory input

Ventral (anterior) - motor output

Question 22

What are the divisions of the spinal cord?

Answer 22

Cervical, thoracic, lumbar and sacral

The amount of white matter varies depending on the region

Question 23

At what spinal level does the spinal cord end?

Answer 23

L1/L2
The vertebral column continues and the lower spinal nerves continue through the column, exiting at their respective intervertebral foramen

Question 24

What is the typical organisation of a spinal nerve?

Answer 24

• Each spinal nerve formed by ventral and dorsal roots
• Sensory axons form dorsal root, motor axons from the ventral horn
• Ventral root motor neuron cell bodies are in the ventral horn
• Dorsal root ganglia contains sensory neuron cell bodies and axons project into dorsal horn

Question 25

What is the dorsal root ganglion & its structure?

Answer 25

• Sensory neurone cell bodies, located between vertebra, before dorsal root
• Part of the PNS
• DRG neurons have branching axons
• One axon in peripheral nerve - detects stimulus (afferent fibre)
• One axon runs in dorsal root to the dorsal horn

Question 26

What are the ventricles of the brain?

Answer 26

2 x lateral and a 3rd 4th ventricle and cerebral aquaduct

Question 27

What is the purpose of the ventricular system?

Answer 27

• Contains CSF fluid and circulates it through the brain (flows out at 4th ventricle into the central canal of the spinal cord)
• CSF fluid important for buoyancy of the brain and shock absorption

Question 28

What produces the CSF?

Answer 28

• Choroid plexus which is present within the ventricles

- Constantly being produced

Question 29

What are the layers of the meninges?

Answer 29

• Dura (thickest, outer)
• Arachnoid (fibrous, middle)
• Pia (thinnest, innermost)

Question 30

What is an important pharmacological property affecting the ability of drugs to cross the blood brain barrier?

Answer 30

Lipid solubility - increased lipid solubility allows drugs to cross the BBB