Laboratory 1 - Rat Brain

Question 1

The brain is located _____ to the spinal cord.

Answer 1

Rostrally.

Question 11

Below is a picture of a rat brain. List the major visible structures (there are five), in order, from anterior to posterior.

Answer 11

Olfactory bulb; two hemispheres of forebrain; pineal gland; cerebellum; brainstem.

Question 12

What plane would a cross-sectioned rat spinal cord be cut in?

Answer 12

Coronal

(as it is horizontal with respect to the brain)

Question 13

What plane would a cross-sectioned human spinal cord be cut in?

Answer 13

Horizontal

(as it sits vertically with respect to the brain)

Question 14

How does the frontal lobe differ in the rat brain compared to its human counterpart?

Answer 14

• Greatly reduced size in proportion to other brain structures.
• Reduced gyration of cortex.

Question 15

How do the areas associated with the temporal lobe in humans differ in the rat brain?

Answer 15

• Much enlarged olfactory bulb.

Question 16

What is the most obvious difference between the cerebellum in the rat and in the human brain?

Answer 16

• The rat cerebellum is proportionally much larger.

Question 17

Comment upon differences in the brainstem between rats and humans.

Answer 17

• The rat brainstem proceeds horizontally away from the brain, rather than vertically.

Question 18

What is unique about the pineal gland of the rat, in comparison to the human brain?

Answer 18

The pineal gland is exposed dorsally between the two hemispheres of the cerebrum.

Question 19

Are there any obvious lobar subdivisions in the rat forebrain?

Answer 19

No (aside from the hemispheres).

Question 20

What is the largest cranial nerve visible on the rat? Which number is it?

Answer 20

The fifth cranial nerve - the trigeminal nerve.

Question 21

What does the trigeminal nerve do? Why is it so important to the rat?

Answer 21

Carries sensory and motor input, critical to survival. Hence large size.

Question 22

Name the 12 cranial nerves in sequence.

Answer 22

1. Olfactory
2. Optic
3. Oculomotor
4. Trochlear
5. Trigeminal
6. Abducens
7. Facial
8. Vestibulocochlear
9. Glossopharyngeal
10. Vagus
11. (Spinal) Accessory
12. Hypoglossal

Question 23

The cerebral acqueducts ensure distribution of cerebrospinal fluid throughout the brain.

Which structure is responsible for supplying the midbrain and brainstem?

Answer 23

The Fourth Ventricle.

Question 24

The spinal cord exists to transmit signals to the extremities. What is the significance of the ventral and dorsal nerve roots?

Answer 24

They are separated transmission conduits for sensory and motor information.

Question 25

What does the gracile fasciculus carry?

Answer 25

Ascending information from the lower limbs.

Question 26

Imagine a horizontal cross-section of spinal cord at around the level of C8. Located imediately lateral to the most medial axon bundle at the dorsal cord is another significant white matter tract.

Considering the level of the spinal cord and location of the tract, what is it most likely to be?

Answer 26

The cuneate fasciculus, carrying information from the upper limbs to the brain.

Question 27

What may be broadly said about the rat midbrain structures in comparison to humans?

Answer 27

They are proportionally larger.

Question 28

Does the thalamus occupy a greater proportion of the brain in humans or in rats?

Answer 28

In rats.

Question 29

What important brainstem structure acts as a relay centre between the cortex and the cerebellum?

Answer 29

The pons.

Question 30

A critical lower brainstem structure is involved primarily in the regulation of autonomic functions.

Given that this structure recieves cranial nerves VII-XII, what is it likely to be?

Answer 30

The medulla oblongata.

Question 31

The corpora quadrigemina are key structural features of the midbrain.

What are the subcomponents that comprise this group? What are their functions?

Answer 31

• The superior colliculi: visual stimulus reflex.
• The inferior colliculi: aural stimulus reflex.

Question 32

The periacqueductal grey region is a collection of grey matter surrounding the fourth ventricle at the midbrain.

What is the function of this area?

Answer 32

Descending modulation and regulation of pain (it releases opiates to inhibit nociception).

Question 33

Name the structure located inferiorly to the thalamus that is involved in regulation of the autonomic nervous system and hormonal control of the pituitary gland.

Answer 33

The hypothalamus.

Question 34

Name the structure(s), located at the level of the lateral ventricles, that converge inferiorly into the internal capsule.

Answer 34

The corona radiata.

Question 35

In mammals, the hippocampus is a critical forebrain structure involved in what function(s)?

Answer 35

Memory consolidation and spatial navigation.

Question 36

50% of rat CNS neurons are located in the cerebellum. What does this mean for the density of neurons in the brain?

Answer 36

There is a much greater density of neurons in the cerebellum compared to the rest of the brain.

Question 37

The cerebellum has ten distinct functional lobes.

What broad structural feature separates these lobes? What other key purpose does it serve?

Answer 37

Cerebellar foldings.

Also increases surface area for neuron density.

Question 38

The vermis is a medially-located structure of the cerebellum that connects the two cerebellar hemispheres.

What important function does it serve?

Answer 38

The vermis recieves incoming proprioceptive information from the periphery via the spinal cord as well as outging motor signal information from the brain.

It compares the two inputs to create a sense of egocentric space.

Question 39

The cerebellar hemispheres may be divided into two broad functional structures. What are these and what are their functions?

Answer 39

• Cerebellar cortex: evaluates incoming messages from forebrain; finetuning of movement
• Deep cerebellar nuclei: sends outgoing signals to muscles

Question 40

What “wool-like” hindbrain structure is involved in the vestibulo-ocular reflex system (the coordination of eye movement with head movement)?

Answer 40

The flocculus.

Question 41

Name the midbrain structure involved in control of vomiting and related autonomic functions.

Answer 41

The Area Postrema.

Question 42

A structure often referred to as the “midbrain nucleus of the auditory pathway” is part of what larger system?

What is the broad function of this system?

Answer 42

The tectal system.

It junctions direct behavioural responses towards points in egocentric space; that is, it is responsible for “aiming” the visual and auditory stimulus reflexes.

Question 43

The dorsal horn of the spinal cord handles sensory information.

What is the corresponding structure for motor information?

Answer 43

The ventral horn.

Question 44

What is the main functional distinction between the dorsal and ventral columns?

Question 45

The descending trigeminal nerve does not, in fact, descend from the brain to the periphery.

Why is it named “descending” and what is its function?

Answer 45

The descending trigeminal descends FROM the face to the brain, carrying deep, crude touch, pain and temperature sensation.

Question 46

Alzheimer’s disease is associated with damage to what brain structure?

Answer 46

The hippocampus.

Question 47

Parkinson’s disease is associated with the degeneration of neurons in what structure?

What specialized role do these neurons normally serve?

Answer 47

The substantia nigra pars compacta.

The degenerating neurons are dopaminergic.