NA and NP (2) - brainstem, cerebellum, cerebrum

Question 1

What is the brain stem?

Answer 1

Consists of the midbrain, pons and medulla oblongata

controls automatic behaviours necessary to survival

pathway between higher and lower neural centres - bringing sensory info or providing motor responses)

associated with 10 of the cranial nerves

Question 2

What is the midbrain?

Answer 2

Contains 2 cerebral peduncles that contain large pyramidal tracts (sends motor output to the target muscles)

A hollow cerebral aqueduct runs through it

Has periaqueductal gray matter involved in pain suppresion

Corpora quadrigemina;
- superior colliculi = visul reflex centres when you are visually following something
- inferior colliculi = auditory relay (startle reflex from hearing a loud abrupt noise)

Question 3

What is the substantia nigra? where is it located?

Answer 3

Located in the midbrain, linked to basal nuclei

A band like nucelous with high melanin content - a precursor of dopamine and communicates with basal nuclei via dopamine)

Question 4

What are red nuclei? Where are they found?

Answer 4

Found in the midbrain

A rich vascular supply of iron pigment in neuron cell bodies; relays nuclei for descending pathways for limb flexion (outgoing motor output)

Question 5

What are the pons? What are the cranial nerves associated with them?

Answer 5

Mainly conduction tracts (AKA bridges)

Cranial nerves 5 (trigeminal), 6 (abducens), 7 (facial)

Other pons nuclei are part of reticular formation and respiration

Question 6

difference between huntingtons disease and parkinsons?

Answer 6

Huntingtons = too much movement in the basal nuclei
- May be unable to control emotions (gate is left open and flooding occurs)

Parkinsons = too little movement in the basal nuclei
- Difficulty walking or writing and loss of facial expression

Question 7

What is the medulla oblongata? Which cranial nerves are associated with this?

Answer 7

Connection from the pons to the spinal cord

Decussation of pyramids = crossing over of neural info which allows for contralateral communication

Inferior olivary nuclei relay sensory info via muscles/joints to cerebellum

Cranial nerves 8(vestibulocochlear), 9 (glossopharyngeal), 10 (vagus), 12 (hypoglossus)

Crucial role in autonomic reflex centres and homeostasis
- cardiovascular centre; cardiac and vasomotor
- respiratory centre; rate and depth or breathing
- others; vomiting, hiccuping, swallowing, coughing, sneezing

Question 8

What is the cerebellum? Important functions? Notable regions?

Answer 8

Influences the timing and patters of skeletal muscle contration
- often repetitive movements that do not need conscious focus
- processes input from cerebral motor cortex, brainstem and sensory receptors
- displays bilateral symmetry; connected by vermis a fine transverse fissure -> folia
- each hemisphere has 3 regions; anterior posterior, flocculonodular

Note cerebellum does not directly send info to motor neurons

Medial parts; trunk and girdle
Intermediate; distal limbs and skills movements
Lateral; planning movements
Flocculonodular; input from equilibrium sensors - balance and eye movement

Question 9

What are the functions and important regions of the cerbellar peduncles?

Answer 9

Connects the cerebellum to brainstem - fibers entering and leaving are ipsilateral (same side) -> unlike the cerebral cortex which is contralateral

a) Superior (outgoing) - connects the cerebellum and midbrain; fibers originate from neurons deep in cerebellar nuclei to then project to cerebral motor cortex
- carries the instructions from cerebellum via the midbrain

b) Middle (incoming) - connects the pons and cerebellum; one way communication from pons to cerebellum not other way around
- informs the cerebellum of voluntary motor activities

c) Inferior (incoming) - connect the medulla and cerebellum; sensory info to cerebellum from muscle proprioceptios and vestibular nuclei (body positioning and homeostasis)

Question 10

What are the steps of cerebellar processing?

Answer 10

1) Frontal motor cortex notifies intent to initiate activity and sends info to cerebellum

2) Cerebellum receives info

3) Cerebellar cortex recieves info and determines best way to cooordinate force, direction and extent of muscle contraction

4) Via the superior peduncles the cerebellum dispatches the blueprint for coordination to cerebral motor cortex

Question 11

What are functional brain systems

Answer 11

a network of neurons that work together but span large distances within the brain

Question 12

Describe the limbic system and its functions

Answer 12

The medial aspect of each cerebral hemisphere and diencephalon

AKA the emotional-visceral brain; amygdala (anger/fear/danger), hippocampus (emotions/memories), anterior cingulate gyrus (gestures/resolving conflicts when frustrated/body language)

Forms links between emotions and memories and odours

Question 13

What is reticular formation, two main functions from which system contained within it?

Answer 13

The central core of the medulla oblongata, pons and midbrain

Reticular activating system (RAS);
1) Maintains arousal of the brain by letting enough info in so we are conscious and aware or surroundings
2) Filtering incoming signals so we aren’t overwhelmed

Question 14

How many spinal nerves are there ?

Answer 14

31 pairs of spinal nerves

Question 15

What is the cauda equina?

Answer 15

AKA horses tail, a looser arrangement of neurons - a collection of nerve roots at the inferior end of the vertebral canal

Question 16

What two structures hold the spinal nerves in place?

Answer 16

1) Denticulate ligaments = pia mater shelving

2) Filium terminale (pia mater covered conus extension)

Question 17

Explain the organization of butterfly wings in the spinal nerves

Answer 17

Contains paired anterior (ventral) and posterior (dorsal) horns

Horns connected by gray commissure

Anterior = motor output
Posterior = arriving info

Smaller lateral horns are associated with the thoracic and superior lumbar regions

Question 18

What are dorsal root ganglion?

Answer 18

afferent fibers from peripheral sensory receptions form the dorsal roots

• have cells bodies of associated sensory neurons; axons travel to higher cord or brain centres and synapse with interneurons in posterior horns at the level entered
• spinal cord = fused dorsal and ventral roots Note it is a part of the PNS

Question 19

What are some characteristics of white matter in the brain?

Answer 19

• Are ascending, descending and transverse commissural tracts which gives direction of fibers

1) Most pathways cross over one side of the CNS to the other (decussation)
2) Most consist of a chain of 2 or 3 neurons
3) Most exhibit somatotopy - mapping occurs
4) All pathways and tracts are paired

Question 20

What are the main protection structures of the CNS?

Answer 20

Bones, blood-brain barrier (BBB), meninges, CSF

Question 21

What are meninges ?

Answer 21

3 CT membranes that cover and protect the CNS, protect blood vessels and enclose venous sinuses, contain CSF and form partitions with the skull

Question 22

What is dura mater?

Answer 22

• tough 2 layers around the brain with an outer periosteal layer and an inner meningeal layer
• spinal cord only has the meningeal layer
• around the brain the 2 layers fuse except at the enclosement of the dural sinuses

Question 23

What are dural septa?

Answer 23

• partitions and anchors falx cerebri -> a longitudinal fissure
• falx cerebri runs alon the vermis between the left and right sides of the cerebellum
• tentorium cerebelli = a transverse fissure that forms a separations between the cerebral hemispheres and parts of the cerebellum

essentially where there are prominent divisions between cerebellum, hemispheres…

Question 24

What is arachnoid mater?

Answer 24

• loose covering separated from dura mater by the subdural space
• subarachnoid space between arachnoid mater and pia mater is filled with CSF and contains largest blood vessels for brain
• role of arachnoid granuklations (villi) in accumulation of CSF (so that CSF can be reabsorbed)

Question 25

What is pia mater?

Answer 25

Delicate CT and tiny blood vessels, the only meninx that clings tightly to the brain and follows convolutions (hills or valleys)

Question 26

What are the 2 infections associated with meninges?

Answer 26

Meningitis = infection associated with meninges
Encephalitis = results in untreated meningitis

Question 27

What is CSF? What is its source? Total CSF capacity in the body?

Answer 27

A liquid cushion to give buoyancy to CNS tissue - has protective and nutritive roles

• similar to blood plasma but has less proteins (made as a filtrate of plasma)

Source = choroid plexuses in roof of ventricles, also have a role in cleaning CSF
- clusters of permeable capillaries enclosed by layer of ependymal cells joined by tight junctions and have ion pumps that can modify the filtrate

Total capacity = 150 mL; is replaced every 8 hours (approx.)

Question 28

What is hydrocephalus? Who would be more likely to experience it?

Answer 28

AKA water on the brain

When you make CSF faster than replacing it

More common or typical to see in infants whose brain is not as developped and sturdy as adults

Question 29

What is the role of the blood brain barrier?

Answer 29

Protecting the internal environment of the CSF
- Because some hormones act as NTs and some ions can increase the rate of neuronal firing, BBB exists to block these signals

Question 30

What are the 3 layers of BBB?

Answer 30

1) Continuous epithelium of capillary wall - very impermeable tight junctions

2) Thick basal lamina surrounding external face of capillary - contains enzymes that destroy epinephrine and norepinephrine so they dont act on neurones

3) Bulbous feet of astrocytes and smooth muscle like cells (pericytes) - maintain endothelial cells and stimulate formation of very tight junctions
- foot processes take fluid and filters what is allowed in

Question 31

What is allowed into the BBB? (list a few)

Answer 31

Glucose, essential amino acidsm some electrolytes, fats, fatty acids, oxygen, carbon dioxide, fat soluble molecules