Meninges and the Cerebral Hemispheres

Question 1

cerebral hemispheres

Answer 1

bilaterally paired, anatomically symmetrical, functionally asymmetrical

Question 2

diencephalon

Answer 2

grey matter buried within the cerebral hemispheres

- includes the paired thalami, hypothalamus, epithalamus

Question 3

brainstem

Answer 3

includes midbrain, pons, and the medulla

- contains vital autonomic centres, cranial nerve nuclei, white matter tracts

Question 4

cerebellum

Answer 4

bilaterally paired cerebellar hemispheres, separated fro, the cerebral hems by the transverse fissure

Question 5

brain

Answer 5

cereb hems, diencephalon, brainstem, cerebellum

Question 6

cerebral cortex

Answer 6

layer of grey matter (neuronal cell bodies), highly folded in sulci (sulk in a corner, hide) and gyri (bumps)
- deep sulci called fissures

Question 7

Landmark sulci of the brain

Answer 7

• central sulcus between frontal and parietal lobe
• parietooccipital fissure between occip and parietal&temp lobe
• lateral fissure between temp lobe and frontal&parietal lobe

Question 8

Dura mater has two layers

Answer 8

periosteal layer which is bound to bone and meningeal layer which folds inward between the cerebral hemispheres (forms dural reflection)

Question 9

subarachnoid space contains

Answer 9

CSF and blood vessels

Question 10

Dural reflections

Answer 10

meninges form rigid folds in major fissures:

• falx cerebri - between cereb hemispheres
• tentorium cerebelli - separates the cerebral hemisphere above and cerebellum below (roof above cerebellum)
• diaphragma sellae - stabilizes position of the pituitary gland in the base of the skull

Question 11

Dural venous sinus characteristics

Answer 11

• called sinuses because they don’t have traditional structure of a vein (still contain venous blood tho)
• contain/drain venous blood from the brain into right and left internal jugular veins
• in the margins of dural reflections (aka between periosteal and meningeal layers of dura)
• all sinuses are continuous bc all the venous blood goes to the jugular vein

Question 12

Cerebral venous drainage

Answer 12

cerebral vein pierces through the meningeal layer and drains blood into the dural sinuses

Question 13

Dural venous sinuses

Answer 13

• superior saggital sinus, inferior saggital sinus (assoc. with falx cerebri)
• straight sinus, confluence of sinuses (assoc. with tentorium cereb)
• transverse sinus
• sigmoid sinus to jugular foramen
• cavernous sinus (receives ophthalmic veins from orbit)
• superior and inferior petrosal sinus

Question 14

Neural tube

Answer 14

hollow, fluid-filled tube, forms the nervous system

Question 15

neural canal

Answer 15

forms the ventricular spaces of CNS, contains CSF, produced by the choroid plexus (modified blood vessels) within the ventricles

Question 16

blood-CSF barrier

Answer 16

tight junctions between ependymal cells of choroid plexus forms the barrier

Question 17

vasogenic edema

Answer 17

results from breakdown of the BBB (increased permeability of brain capillaries)
- results in increased intracranial pressure and can act like a space occupying lesion (aka a tumour)

Question 18

what can cause BBB breakdown

Answer 18

tumours, arteriovenous malformations, inflammation

(2° to stroke, MS, etc)

Question 19

ventricular spaces are assoc. with…

Answer 19

subdivisions of the nervous system

• cerebral hemispheres (lateral ventricles)
• diencephalon (third ventricle)
• midbrain (cerebral aqueduct)
• pons, medulla, cerebellum (fourth ventricle)
• spinal cord (central canal)

Question 20

Fourth ventricle is continuous with…

Answer 20

the subarachnoid space through the median aperture and the lateral apparatus

Question 21

circulation of CSF

Answer 21

CSF produced by choroid plexus continuously (500 mL a day but total volume in the ventricles is only 150 mL)

• CSF circulates through the ventricles, enters subarachnoid space via median and lateral apertures of fourth ventricle and circulates there.
• eventually drains through saggital sinus

Question 22

How is CSF returned to venous blood

Answer 22

via arachnoid granulations in dural venous sinuses and also along the sheaths of cranial and spinal nerves to surrounding lymphatics

Question 23

hydrocephalus

Answer 23

enlarged ventricles (most common point of blockage is the cerebral aqueduct, which will block everything but the fourth ventricle)

Question 24

cerebral cortex is ____ matter and beneath is the subcortical _____ matter

Answer 24

grey

white

Question 25

subcortical white matter

Answer 25

- carries afferent information toward neuronal cell bodies of cerebral cortex - carries efferent information away from neuronal cell bodies of cerebral cortex - may be association, commissural, or projection fibres have grey matter structures buried within (basal ganglia, and the diencephalon which is thalamus, hypothal., and epithal.)

Question 26

Sensory input in the cerebral cortex

Answer 26

- all sensory modalities reach cerebral cortex, most after a relay to the thalamus Each modality has an area dedicated to its: - perception, 1° sensory cortex (visual, somatosensory, auditory) - interpretation, called an association cortex - multimodal association cortices integrate

Question 27

1° motor cortex

Answer 27

precentral gyrus - control of voluntary skilled movement - somatotopic representation of the contralateral half of the body - area is proportional to precision of movement not size of body part

Question 28

Motor cortex is somatotopic: order of body parts from lateral fissue to median fissure

Answer 28

pharynx, tongue, lips and jaw, face, eyelid and eyeball, neck, thumb, index, middle, ring, little finger, hand, wrist, forearm, elbow, arm, shoulder, trunk, hip, knee ankle, toes (all in the median fissure)

Question 29

Premotor cortex

Answer 29

supplementary motor area - adjacent portions of frontal lobe - function in programming of preparation for movement and control of posture

Question 30

1° somatosensory cortex

Answer 30

postcentral gyrus (like a headband across the brain, after central gyrus) - PERCEPTION of somatosensation - somatotopic representation of the contralat. half of the body (sensory homunculus)

Question 31

Somatosensory association cortex

Answer 31

INTERPRETATION of somatosensation | - conscious awareness of the contralateral half of the body

Question 32

1° Auditory cortex is organized...

Answer 32

tonotopically (map of cochlear duct)

Question 33

most people are ____ hemisphere dominant

Answer 33

left

Question 34

auditory association cortex

Answer 34

in the temporal lobes in the dominant hemisphere - it's next to Wernicke's area in the non dominant hemisphere - corresponding area interprets prosody (cadence of speech)

Question 35

fluent aphasia

Answer 35

Lesion of wernicke's area - has problem understanding incoming speech and also will not understand what's coming out of their mouth, so they will speak fluently but incoherently

Question 36

motor speech area

Answer 36

portions of the frontal lobe - in the dominant hemisphere (usually left), we have Broca's area which functions in the motor aspects of speech - corresponding area in the non-dominant hemisphere controls prosody

Question 37

Non fluent aphasia

Answer 37

Lesion of Broca's area - person will be VERY frustrated because they can understand you perfectly and themselves but they will not be able to speak

Question 38

1° gustatory cortex

Answer 38

inferior part of the postcentral gyrus and insula | - conscious perception of taste

Question 39

1° olfactory cortex

Answer 39

in the temporal lobe | - conscious perception of smell

Question 40

multimodal association cortices

Answer 40

prefrontal cortex - integrates info from various assoc. cortices - higher intellectual functions (reasoning, prediction, emotion) inferior portion of the parietal lobe - interface between somatosensory, visual, and auditory assoc. cortices

Question 41

structures of the basal nuclei/ganglia

Answer 41

includes the: - caudate - putamen - globus pallidus or pallidum - substantia nigra and subthalamus

Question 42

functions of the basal ganglia

Answer 42

- refine normal voluntary movement | - not directly connected to the spinal cord so it doesn't directly control movement

Question 43

diseases of the basal ganglia cause:

Answer 43

hypokinesis without paralysis, hyperkinesis (tremors), altered posture and muscle tone, altered cognition, behavioural disturbances, Parkinsonism

Question 44

Diencephalon

Answer 44

consists of the thalamus, hypothalamus, and the epithalamus

Question 45

Functional organization of the Thalamic nuclei

Answer 45

sensory nuclei, motor nuclei, limbic nuclei (emotions, mood), association nuclei (integrates sens. info and connects with assoc. cortices), intrinsic&diffuse-projecting nuclei (influences arousal levels)

Question 46

Sensory nuclei of thalamus

Answer 46

- vision (LGN) - hearing (MGN) - somatic sensation, conscious proprioception, taste (ventral posterior)

Question 47

Motor nuclei of thalamus

Answer 47

- associated with basal nuclei and cerebellum | - movement planning and control (ventral anterior and ventral lateral)

Question 48

hypothalamus

Answer 48

- maintains homeostasis via neural and hormonal means in response to interoceptive and limbic input - regulates reproductive, autonomic and instinctive functions, food and water intake, circadian rhythms, emotional aspects of behaviour.

Question 49

epithalamus

Answer 49

includes the pineal gland (secretes melatonin, functions in circadian rhythm and onset of puberty).