Chapter 26: Cerebrum

Question 1

Intro

Answer 1

cerebral systems help with:

• perception
• moving voluntary motor execution
• using language and nonverbal communication
• using visual information
• making decisions
• managing emotions
• remembering
• using mind-body interactions

Question 2

Diencephalon

Answer 2

everything involved with the thalamus- a little behind the midpoint because they are part of the sensory pathway (the final synapse for everything going up to the cortex)

Question 3

Thalamus

Answer 3

• -Selective filter for cerebral cortex
• -Directs attention to “important”:
• relay nuclei (to cortex)- relays information from the sensory system, basal ganglia, and cerebellum
• Association nuclei- Thalamus has some loops with the cortex
• Nonspecific nuclei- help with consciousness, arousal, and attention (reticular formation plays with thalamus for arousal)

Question 4

Thalamic lesions

Answer 4

• Loss of contralateral sensation (especially proprioception)
• Thalamic pain (neuropathic) syndrome possible. (very troubling for the patient, pain is abnormally active from thalamus to the cortex, no pain stimulus but they perceive pain)
• usually the CVA is next door to the thalamus in the internal capsule
• rostral to the brainstem the pattern is opposite everything.

Question 5

Pushers syndrome (lateropulsion)

Answer 5

if the patient has damage on one side of the brain (right) I lose input from the left inner ear, If I lose input from left inner ear I lose the pull of gravity, don’t feel the pull of gravity from left inner ear, so I feel like gravity is pulling me harder on my right (like tipped over to my right), so the patient tries to sit self back up and correct pull of gravity, since not actually being pulled gravity they tip themselves over to their left side due to an inappropriate push against a perceived gravity pull.

Treatment- visual system and cognitive appreciation

• vertical piece of tape on shirt and then one on the mirror and try to line the tape pieces up with one another to help them identify what straight up and down is
• keep a visual anchor either vertical or horizontal anchor

Question 6

Thalamus job

Answer 6

Homeostasis- we most often associate it with modulation of the autonomic system (visceral homeostasis, BP, Body temp, HR, etc)

• Because it is part of the primal brain it participates in eating, reproduction, defense (does it for the survival of the species)
• expression of emotion- Spinoemotional pain pathway )projected into the hypothalamus and cortex to signal threats into homeostasis)
• helps keep the sleep/wake cycle

Question 7

Hypothalamus and pituitary

Answer 7

• Directly secretes Beta-endorphin precursor
• Promotes cortisol release from adrenal (HPA axis)

Beta endorphin precursor of opiate compound that is important in pain relief (level 4 of antinociception matrix)

-If chronically active it is bad, promotes cortisol release (what we release to threats to homeostasis), HPA axis what it promotes cortisol release through the pituitary through adrenal glands (response to stress)

Hypothalamus pituitary adrenal=HPA axis

Question 8

Pituitary tumors (bitemporal hemianopsia)

Answer 8

will cut visual tracts if damage optic chiasm- leads to bitemporal hemianopsia (tunnel vision)

Question 9

Subcortical white matter- internal capsule

Answer 9

Projection fibers- internal capsule

• white matter bundles go 3 directs (up and down, side to side, and forward/backwards), lets say the fibers that go up and down are called projection fibers (project body into the brain and the brain into the body) the most common projection bundle is called the internal capsule (connects the head to the rest of the body).
• Internal capsule has a body map organization

Question 10

Subcortical white matter- commissural fibers (corpus callosum)

Answer 10

fiber bundle that goes side to side- commissural fibers- connects left and right hemispheres- most prominent example of side to side is the corpus callosum (longitudinal fissure)

Question 11

Subcortical white matter- Association fibers (short, long)

Answer 11

Association fibers go forward/backwards- associate one lobe with another.

Ventral visual stream- association fibers projecting from the occipital lobe to the temporal lobe

Dorsal visual stream- Association fibers projecting from the occipital lobe to the parietal to the frontal lobe.

Question 12

Damage to the internal capsule

Answer 12

• Decreased voluntary control of movement
• Decreased postural control
• Decreased somatosensation
• Possible homonymous hemianopsia (could knock off the optic tract)

Question 13

Basal ganglia

Answer 13

-two more eggs at base of the brain sit a bit forward of midline
-Know the 4 things the Basal Ganglia does:
in what muscles, in what sequence, in what synergies, and how strong

-Damage to the basal ganglia will lead to trouble in one of the 4 things above.

Question 14

Basal ganglia motor loop

Answer 14

• Selects muscles to activate (deactivate)
• creates muscle synergies
• sequences movements
• regulates muscle force

Question 15

Pyramidal cell

Answer 15

cells located in layer 5- cells of the corticospinal tract (cell body kind of looks like a pyramid, known as the pyramidal cell and the pyramidal tract)

Question 16

mapping of the cerebral cortex

Answer 16

-cortex mapping will help predict signs and symptoms when broken.

• Frontal lobe- executive function and motor control (pre-frontal is executive function)
• Parietal lobe- somatosensation to distinguish sensation form body from sight and from sound
• Temporal- auditory- especially hearing
• Occipital lobe- vision.

Question 17

Brodman’s areas

Answer 17

what stimuli would create a response in what areas. Micro electrode on outside of the brain and turn it up until a part of the body starts to move and mark it as having affiliation with that part of the body.

Question 18

process of the cerebral cortex

Answer 18

• I have the idea to move (starting point)
• I have the motor plan to move
• I send the plan signal to the body to move
• I feel and see and hear what happened when I move
• I interpret those sensations, evaluate all the info
• And I think to move the same or different next time to move again.

Question 19

Primary sensory areas

Answer 19

Long strip in parietal lobe- post-central gyrus (specifically has somatosensation from body, not eyes or ears) all of conscious somatosensory sensation systems end up here.
-Allows us to feel and establish characteristics of what I feel (its kind of light, its smooth, its roughly cylindrical, has an indentation on the front where my thumb fits). Don’t give it meaning but describe characteristics.

-Damage- lose above and also tactile localization, will also lose conscious (post-central gyrus) vs unconscious (cerebellum) proprioception.

Question 20

Primary sensory areas-auditory

Answer 20

• Primary sensory areas are just little dots, secondary areas are circles around the little dots.
• Primary auditory area- piece of temporal lobe where we hear stuff and determine characteristics of what we hear (its pitch, loudness, quality) right behind the ear.
• Damaged- there will not be one sided deafness because each ear projects bilaterally.
• We need both ears, both temporal lobes, to determine the arrival of where sound comes from in space (will have trouble locating the source of the sounds)

Question 21

Primary sensory areas- visual

Answer 21

At the tip of the occipital lobe- In this area, we begin to characterize what we see (light and dark, the size, shape, and location) start to grossly put things into visual field in terms of size and location.
-Haven’t assigned color and other signs yet.

• If damaged- we will have homonymous hemianopsia- If only one hemisphere is damaged.
• if both sides are damaged there will be a cortical blindness (may have blind sight- may be able to grossly react to objects in the visual field.)

Question 22

Primary sensory areas- vestibular

Answer 22

the inner ear comes to the cortex in the right temporal lobe and that it is right next to the hearing part (balance and equilibrium part comes to consciousness near the hearing part).
-If damaged- we wont know how their head is moving and will not know the pull of gravity (likely to show pushers syndrome)

Question 23

Secondary sensory cortex

Answer 23

Once we have characteristics of what we see, touch, and hear we want to give meaning to it which comes through the secondary sensory areas (perception=gives meaning to something)

Question 24

Agnosia

Answer 24

Inability to recognize objects when using a specific sense, even though discrimination ability with that sense is intact.

-damage to the secondary sensory cortices produces agnosia.

Question 25

Secondary sensory areas

Answer 25

Next door to post-central gyrus is the secondary area for somatosensation

-This area of the parietal lobe is where you give meaning to what you touch (stereognosis)

Question 26

aSecondary sensory areas-visual

Answer 26

Analyzes motion and color and it helps us give meaning to what we see (two visual stream to what we give meaning to what we see)

• Ventral stream- to be able to perceive it- classify it and then give it a name and assign meaning to it
• if damaged we will have a visual agnosia- inability to give meaning to what it is that I see

Dorsal stream-Visual guide movements towards an object of interest.
-If damaged you will have an optic ataxia- will not be able to reach with precision towards and object you see.

Question 27

Secondary sensory areas- Auditory

Answer 27

where we classify what we hear

Two basic processes:

1) Auditory association area decides if this is speech or not speech, if speech it hands it off to another part of the brain to be decoded in Wernicke’s area.
2) If it is not speech it assigns meaning to whatever it is (can distinguish footsteps form a doorbell)

-Auditory agnosia- can tell us the differences between footsteps and a doorbell (only by characteristics) but cannot tell which is which

Question 28

Primary motor cortex

Answer 28

Fontal lobe- pieces of the frontal lobe that help you plan and execute movements.

-In primary motor cortex- pre-central gyrus- (UMNs)- where all of our corticospinal neurons live and have a high degree of control over them (triangles in shape because they are pyramids)

Fractionated movement- any combinations of movement that I want

-Lose motor ability on opposite side of stroke (most obvious loss is in the hand)

Question 29

Dysarthria

Answer 29

Flash of dysarthria is soft and mushy in association

Flaccid- soft and not articulated (LMN)
Spastic- forced, tight, and nasally sounding (UMN)

Question 30

Primary motor cortex- premotor area

Answer 30

• helps with planning core and proximal muscle movements and helps create anticipatory movements of muscles (feed forward)
• If damaged- it leads to a condition called apraxia- a breakdown between concept and performance
• loss of the ability to carry out familiar purposeful movements despite understanding the task and despite having intact motor and sensory systems. (ideational vs ideomotor- ideomotor is more common (stand pivot transfer can describe it perfectly but not able to create the motor plan on demand to go and do it)

Question 31

Primary motor cortex- supplementary motor area

Answer 31

in motor loop with basal ganglia- it helps to sequence movements and to start movements (to get things going)
-If broken we have a condition called perseveration- to continue after the need of the task has passed.

Question 32

Primary motor cortex- Broca’s area

Answer 32

Little square of frontal lobe- is in left hemisphere for 95% of us. the left hemisphere creates the motor plan to say the words we are thinking.
-Job is to create the motor plan to say the words I am saying- sends language commands to the face and the hands (aphasia and apraxia)

-If broken, they can think the words but cannot create the motor plans to get the words out.

Question 33

Inferior frontal gyrus- Primary motor cortex

Answer 33

for 95% of us- the same spot in the right hemisphere creates the paraverbal aspects of speech (pitch, intensity, etc. how the words are delivered).

-Words are perfect but no variation to the melody of what is said. Has a left hemiparesis 95% o the time.

Question 34

ways the brain can get damaged

Answer 34

Stroke, Tumors, Epilepsy