Brain 3: midbrain and Cerebellum

Question 0

what is cerebral peduncles

Answer 0

anterior of midbrain
paired bundles of axons
axons from
corticospinal tracts - motor area in cerebral cortex to the SC
corticobulbar tracts - motor area in cerebral cortex to medulla
corticopontine tracts - motor area in cerebral cortex to pons

Question 1

What does midbrain contain

Answer 1

Cerebral peduncles
Tectum (superior colliculi and inferior colliculi)
substantia nigra
red nuclei

Question 2

What is tectum

Answer 2

posteior to midbrain
contains 4 rounded elevations:
Superior colliculi: coordinates movements of head, eyes, trunk in response to visual stimuli (tracking movement)
Inferior colliculi: coordinates movements of head, eyes, trunk in response to auditory stimuli
Startle reflex - sudden movements of head, eyes, trunk that occur when surprised by a loud noise

Question 3

Substantia nigra

Answer 3

in Midbrain
Neurons release dopamine and help control subconscious muscle activities
loss of these neurons is associated with Parkinson’s disease

Question 4

Red nuclei

Answer 4

in Midbrain
Invovled in voluntary muscle movements
rich blood supply
iron-containing pigment

Question 5

Nuclei associated with cranial nerves in midbrain

Answer 5

CN III oculomoter nerves

CNIV trochlear nerves

Question 6

what is Reticular formation

Answer 6

Found throughout brain stem
Net like arrangement of grey and white matter
Grey matter - cluster of cell bodies
White matter - small bundles of myelinated axons

Question 7

Reticular activating system (RAS)

Answer 7

RISE AND SHINE
consists of sensory axons that project to the cerebral cortex
can be activated by visual, auditory, mental, pain, touch pressure, proprioceptive stimuli
BUT no smell.
involved in consciousness
active during arousal
helps maintain attention and alertness
prevents sensory overload by filtering out insignificant information so that it does not reach consciousness

Question 8

inactivation of RAS produces

Answer 8

Sleep. A state of partial consciousness from which an individual can be aroused.

Question 9

damage to the RAS results in

Answer 9

Coma: a state of unconsciousness from which an individual cannot be aroused
In the lightest state of coma, people still have brain stem and spinal cord reflexes
in deepest states, those reflexes are lost

Question 10

which drug can affect RAS?

Answer 10

Melatonin by induce sleep

Anesthetics turn off consciousness via the RAS

Question 11

what does RAS do to muscle

Answer 11

Consists of motor axons that connect to the cerebellum and spinal cord to help regulate muscle tone. )the slight degree of involuntary contraction in normal resting skeletal muscle.
Invovled in regulation of heart rate, BP, respiratory rate.

Question 12

cerebellum

Answer 12

Highly folded surface, increasing the surface area of its outer grey matter, allowing for a greater number of neurons

Question 13

how many % of brain mass is the cerebellum

Answer 13

a tenth of brain mass but contains half of the neurons

Question 14

what separates the cerebellum from the cerebrum

Answer 14

Tentorium cerebelli

Transverse fissure

Question 15

3 cerebellar hemispheres

Answer 15

consists of lobes separated by deep and distinct fissures
Anterior lobe and posterior lobe: govern subconscious movement of skeletal muscles
Flocculonodular lobe: Invovled in equibillum

Question 16

cerebellar cortex

Answer 16

superficial layer of cortex
Folia: consists of grey matter in a series of folia
Arbor vitae: deep to the folia (grey matter) are tracts of white matter called arbor vitae

Question 17

Cerebellar nuclei

Answer 17

Nuclei in white matter

Question 18

3 cerebellar peduncles

Answer 18

superior, middle and inferior cerebellar peduncles

Question 19

cerebellum to red nuclei (midbrain) and thalamus

Answer 19

superior cerebellar peduncles

Question 20

largest and axons carry impulses for voluntary movements from pontine nucleus to cerebellum

Answer 20

middle cerebellar peduncles

Question 21

what does inferior cerebellar preduncles do?

Answer 21

1. axons of spinocerebellar tracts that carry sensory information from proprioceptors in trunk and limbs
2. axons from vestibular apparatus of inner ear + from vestibular nuclei of medulla and pons
3. axons from the inferior olivary nucleus of meddula that enter cerebellum and regulate cerebellar neurons
4. axons that extend from the cerebellum to the vestibular nuclei of medulla and pons
5. axons that extend from cerebellum to reticular formation

Question 22

Function of cerebellum

Answer 22

Primary: to evaluate how well movements initiated by the cerebrum are actually carried out

• if not carried out correctly, the cerebellum detects the discrepancy and sends feed back signals to the cerebral cortex
• the feedback signals help correct the errors, smooth the movements and coordinate complex sequences of skeletal muscle contractions
• also regulates balance and posture

Question 23

Ataxia

Answer 23

Loss of ability to coordinate muscle movements
can’t touch the tip of nose, can’t coordinate moments with the proprioceptive info
changed speech pattern due to uncoordinated speech muscles
staggering or abnormal walking gait
alcohol inhibits activity of cerebellum so drunks show signs of ataxia
ataxia can also occur from degenerative disease (MS, Parkinson’s) trauma brain tumors, genetic factors, meds side effects

Question 24

Dysarthria

Answer 24

problem with speech

Question 25

Aphasia

Answer 25

difficulty to find a word trying to say