21 – Cerebrum II

Question 1

Lesions of cerebral cortex: signs of lesion to maintenance of consciousness:

Answer 1

-decreased level of consciousness
>lethargy to obtunded/stupor to coma

Question 2

What are some of the subcortical structures?

Answer 2

1. Olfactory system
2. Hippocampus
3. Caudate nucleus
4. Basal ganglia
   *most associated with limbic system

Question 3

Olfactory system:

Answer 3

*CN does not go through thalamus! (ONLY one with direct input)
-cell bodies are outside the CNS and extend neurons and synapse onto piriform lobe
>learning and memory

Question 4

Olfactory system (piriform lobe) gives rise to:

Answer 4

-amygdala
-hippocampus
*strong connection of smells to environment

Question 5

Amygdala:

Answer 5

-‘almond’ shaped-
-nucleus within piriform lobe
-responsible for perception=’fear’ center of the brain
*lesions=perform more risky behaviours

Question 6

Hippocampus:

Answer 6

-‘C-shaped structured (curves laterally and ventrally)
-very large nucleus
-forms memories
-learns new behaviours
Ex. where rabies ends up

Question 7

Caudate nucleus:

Answer 7

-important for initiating voluntary movements
-part of basal ganglia

Question 8

Olfactory system has a direct association with:

Answer 8

-subcortical structures
-humans: certain smells evoke an emotional response (happiness, hunger, nausea, etc.)
-domestic species: *important for survival

Question 9

What are some behaviour signs with a lesion to the cerebral cortex + subcortical structures?

Answer 9

-loss of learned behaviors: not always noted
-increased activity (circling, pacing)
-abnormal behaviours
-tremors

Question 10

What are some of the abnormal behaviours with a lesion to the cerebral cortex + subcortical structures?

Answer 10

-head pressing (more common in large animals)
-inappropriate fear of aggression
-inappropriate innocuous behaviours

Question 11

What are some examples of inappropriate innocuous behaviours?

Answer 11

-chewing
-fly biting
*psychomotor seizures/complex partial seizures

Question 12

Seizures are:

Answer 12

-involuntary, sudden electrochemical disturbance within the brain
>results in temporary changes to mentation/awareness, muscle tone and behaviours
*ALWAYS due to a lesion in the FOREBRAIN

Question 13

What happens to the neurons in the cerebral cortex during a seizure?

Answer 13

-become spontaneously activated
>spreads to nearby cortical areas through white matter tracts
*can connect L and R hemispheres via corpus callosum

Question 14

Degree of seizures can be:

Answer 14

-partial/focal
>partial motor
>complex partial
-full body (grand mal)=generalized

Question 15

Seizures can be dangerous:

Answer 15

-unaware and unable to control their bodies
Ex. biting, thrashing (particular dangerous in large animals)

Question 16

Once a seizure has been initiated:

Answer 16

-not much can be done to stop them
>unless give IV or able to restrain animal to give medications

Question 17

Generalized (grand mal) motor seizures:

Answer 17

-most common type
-loss of consciousness
-become recumbent (lateral) with rigid extended limbs (tonic-clonic=paddling, running movements)
-visceral component
-usually short lasting (depends on underlying cause)
>regain consciousness but often disorientated (post-ictal phase)

Question 18

Clonic:

Answer 18

-repetitive muscle movement

Question 19

Examples of visceral component with generalized motor seizures?

Answer 19

*pre-ictally and during the seizure
-hypersalivation
-urination
-defecation
-dilated pupils

Question 20

What are some neurological causes of seizures?

Answer 20

-inflammation (bacterial, fungal, viral)
-neoplasia
-swelling
-idiopathic seizures (seizure disorder)

Question 21

Idiopathic seizures:

Answer 21

-epilepsy: pattern of repeated seizures in same animal with no known cause
-no identifiable causes (MRI shows no structural abnormalities)

Question 22

What are some non-neurological causes of seizures?

Answer 22

-metabolic
>hypoxia
>hypoglycemia
>hyperthermia
>toxic ingestion (ex. chocolate, Xylitol)
>liver disease

Question 23

What are partial motor seizures?

Answer 23

-abnormal muscle tone in localized region of the body, often involving the FACE
>large portion of motor cortex is dedicated to the face
*don’t lose consciousness and then don’t typically have a post-ictal phase
*usually last longer

Question 24

Complex partial seizures:

Answer 24

-psychomotor seizures (‘temporal lobe seizures’)
>humans will sometimes hear noises
-abnormal activity within behavioural regions of the brain
>aggression, biting behaviour, chasing tail
>coordinated abnormal movement/behaviour