Telencephalon and Diencephalon

Question 1

describe the folding of the neural tube

Answer 1

• prosencephalon (forebrain)
• mesencephalon (midbrain)
• rhombencephalon (hindbrain)
• developed from the back forward

Question 2

what are the derivatives of the prosencephalon?

Answer 2

forebrain

• telencephalon: cerebral hemispheres, surrounds the lateral ventricles
• diencephalon: epithalamus (pineal), thalamus, hypothalamus, optic cup/nerves, surrounds the 3rd ventricle

Question 3

describe the ventricles of the brain

Answer 3

• R and L lateral ventricles, third ventricle, fourth ventricle
• connected by foramina
• filled with CSF, contains choroid plexus (produces CSF, is located in every ventricle)

Question 4

describe ventricle development and association to key brain regions

Answer 4

Question 5

what is CSF?

Answer 5

• continuously produced in the ventricles
• high in sodium, low in potassium (these create chemical gradients)
• no protein (the presence of protein is usually indicative that there is a problem)

Question 6

what are the 3 main purposes of CSF?

Answer 6

• buoyancy
• protection (positive pressure, cushion)
• chemical stability (high sodium, nutrients, etc.)

Question 7

describe the volume of CSF

Answer 7

• total adult volume is ~100-150ml
• replaced about 4 times each day (~500ml daily)

Question 8

describe the flow of CSF

Answer 8

Question 9

what are meninges?

Answer 9

• a system of membranes which envelops the centeral nervous system
• 3 layers - dura mater, arachnoid mater, pia mater
• protect organs from rubbing against bones of the skull and spine

Question 10

describe the meningeal layers

Answer 10

dura mater - dura

leptomeninges (layers and a space):

• arachnoid - a barrier
• subarachnoid space - CSF
• pia - vessels run in this layer and penetrate the cortex

Question 11

what is obstructive hydrocephalus?

Answer 11

• obstruction of the CSF flow that causes buildup of CSF in ventricles
• can be reversed with the use of a splint

Question 12

which two main arteries supply blood to the brain?

Answer 12

• internal carotid artery
• vertebral arteries

Question 13

name the branches of the internal carotid artery and vertebral arteries that supply the brain

Answer 13

Question 14

describe vertebrobasilar and carotid circulation

Answer 14

Question 15

find the posterior cerebral a., basilar a., internal carotid a., anterior spinal a., and vertebral a.

Answer 15

Question 16

which arteries supply each colored area of this brain?

Answer 16

• yellow - anterior cerebral artery
• red - middle cerebral artery
• blue - posterior cerebral artery

Question 17

what is the blood brain barrier?

Answer 17

• composed of high-density cells connected by tight junction that restrict passage of substances from the bloodstream
• it allows diffusion of small hydrophobic molecules (O2, CO2, hormones)
• cells actively transport metabolic products such as glucose across the barrier with specific proteins

Question 18

describe characteristics of an epidural hematoma

Answer 18

• between skull and dura mater
• dura peels off skull, space fills with arterial blood
• compresses brain
• usually a result of a skull fracture and torn middle meningial artery

Question 19

describe characteristics of a subdural hematoma

Answer 19

• occurs below the dura mater in the subdural space
• dura still attached to skull
• venous blood fills subdural space and compresses brain
• result of a torn bridging cerebral vein

Question 20

what is a subarachnoid hemorrhage?

Answer 20

• commonly occur as a result of rupture of an a. in the circle of willis
• between arachnoid mater and pia mater; subarachnoid space

Question 21

what is the telencephalon? what are its 4 main divisions?

Answer 21

• cerebral cortex
• frontal lobe, parietal lobe, temporal lobe, occipital lobe

Question 22

what 2 structures are inside the telencephalon?

Answer 22

basal ganglia and limbic system

Question 23

what are Brodmann’s areas?

Answer 23

regions of the cerebral cortex that are defined by a number

Question 24

what is a commissure?

Answer 24

reciprocal connections

Question 25

what is a chiasma?

Answer 25

crossing and/or intersection of two tracts

Question 26

what is decussation?

Answer 26

cross-over of independent tracts at the same site (form an X)

Question 27

what are "crossing fibers"?

Answer 27

ill-defined fibers whose principal direction may not be defined

Question 28

what is a fascicle?

Answer 28

a bundle

Question 29

what is a fasciculus?

Answer 29

a bundle of fibers

Question 30

describe the diencephalon

Answer 30

* surrounds the third ventricle * major divisions: epithalamus, thalamus, hypothalamus, "sub thalamus"

Question 31

describe the epithalamus

Answer 31

* pineal (serotonin/sleep) * habenula (negative feedback to reward) * posterior commissure - pupillary light reflex

Question 32

describe the thalamus

Answer 32

* major "relay" nuclei * on either side of 3rd ventricle

Question 33

describe the hypothalamus

Answer 33

* endocrine/physiological stasis * surrounds the anterior portion of the third ventricle

Question 34

label these portions of the hypothalamus

Answer 34

Question 35

what are the 4 subregions of the hypothalamus?

Answer 35

* preoptic area * suprachiasmotic (anterior) region * tuberal (middle) region * mammillary (posterior) region

Question 36

what does the hypothalamus control?

Answer 36

* autonomic * endocrine * emotional * somatic

Question 37

describe the basal ganglia

Answer 37

* sits on top of (dorsal to) the diencephalon * extrapyramidal motor system * modulates the initiation, termination, and amplitude of intentional movements

Question 38

describe the two main components of the modulatory cortical loop

Answer 38

* basal ganglia afferents - robust input from almost all parts of the cortex * basal ganglia efferents - ventral thalamic relay to cortex; others - superior colliculus, forebrain, limbic * somatic motor loop: somatomotor control; occulomotor loop (eye movements), frontal loop (cognitive functions), and limbic loop (emotional and visceral functions

Question 39

what are the 5 major nuclei of the basal ganglia?

Answer 39

* caudate nucleus * putamen * globus pallidus * subthalamic nucleus * substantia nigra

Question 40

what forms the striatum?

Answer 40

the caudate and the putamen

Question 41

what forms the lentiform nucleus?

Answer 41

putamen and globus pallidus

Question 42

what are the two subdivisions of the substantia nigra?

Answer 42

* pars compacta * pars reticulata

Question 43

describe the blood supply to the basal ganglia

Answer 43

* branches of the anterior and middle cerebral artery (remember these come from the internal carotid artery)

Question 44

what is hyperkinesia?

Answer 44

excessive abnormal movements, often with increasing dementia example: Huntington's disease * chorea * hemiballism

Question 45

describe Huntington's disease

Answer 45

* type of hyperkinesia * cause: genetic * loss of striatal projection neurons * anatomy: striatal atrophy atrophy of putamen: chorea atrophy of caudate: dementia

Question 46

what is chorea?

Answer 46

involuntary, quick, jerky, irregular movements: * major chorea * minor chorea (Sydenham's chorea): associated with rheumatic fever

Question 47

what is hemiballism?

Answer 47

* repetitive, but constantly varying, large amplitude involuntary movements of the proximal parts of the limbs * decrease activity of the subthalamic nucleus

Question 48

describe hypokinesia

Answer 48

overall decreased bodily movements example: Parkinson's disease

Question 49

describe Parkinson's disease

Answer 49

* hypokinesia * cause: genetic/environmental/idiopathic loss of substantia nigra dopamanergic projection neurons to the striatum * symptoms: bradykinesia, rigidity, tremor at rest

Question 50

what is the circuit of Papez?

Answer 50

part of the limbic system

Question 51

what is wernicke-korsakoff syndrome?

Answer 51

* limbic amnesia * cause: vit B1 deficiency and alcoholism * site: mammillo-thalamic tract disruption (no damage to hippocampus) * symptoms: inability to form new memories loss of memory, can be severe hallucinations confabulation (make up stories)

Question 52

describe alzheimer's disease

Answer 52

* limbic amnesia * bilateral medial temporal lobe damage * common hippocampal deficits: amnestic/inability to form new memory reduced motivation troubles navigating familiar places general cognitive impairment (often mild)