Chapter 14 - Brain & Cranial Nerves Flashcards
Development of brain
Three to four-week embryo:
forebrain (prosencephalon)
midbrain (mesencephalon)
hindbrain (rhombencephalon)
**Development of Brain **
5-week embryo
telencephalon (cerebrum)
diencephalon (thalamus, hypothalamus & epithalamus)
mesencephalon (midbrain)
metencephalon (**pons & **cerebellum)
myelencephalon (medulla oblongata).
Forebrain
Midbrain
Hindbrain
**Forebrain - **Cerebrum & Diecephalon (3)
**Midbrain **& cebral aqueduct
**Hindbrain - **pons & cerebellum + medulla
Brain stem
consists of?
continuation of spinal cord
consists of medulla oblongato, pons & midbrain
second largest part of the brain.
posterior to brain stem
Cerebellum
Diencephalon
superior to brain stem
gives rise to thalamus, hypothalamus & epithalamus
largest part of brain
cerebrum
cranial meninges
**dura mater - **2 layers (perieosteal & meningeal)
arachnoid mater
pia mater
(3) extensions of the dura mater separate parts of the brain:
**1) falx cerebri - **seperate the 2 cerebral hemispheres
**2) falx cerebelli - **seperate the 2 cerebellar hemispheres
**3) tentorium cerebelli - **seperate cerebrum from cerebellum
Extensions of the Dura Mater: Brain Blood Flow and the Blood-Brain Barrier
Brain receives approximately _____% of the total blood supply.
Internal __ & __ arteries carry blood to brain.
Internal _____veins return blood from the brain.
Blood-brain barrier (BBB) protects brain from?
20%
internal **carotid & vertebral **arteries - blood to brain
internal **jugular **veins return blood from brain
harmful substances.
Cerebrospinal Fluid (CSF)
clear, colourless fluid that protects CNS from chemical & physical injuries, absorbs shock, helps transport nutrients & wastes from blood & nervous tissue
circulates through cavities in brain (**ventricles) & spinal cord (central canal) **& in subarachnoid space
Ventricles
(3) & cerebral aqueduct
CSF-filled cavities within the brain.
** 1 lateral ventricles - **in each hemisphere seperated byb septum pellucidum
**third ventricle - **along midline superior to hypothalamus
**cerebral aqueduct - **midbrain
fourth ventricle - between brain stem & cerebellum
CSF formation & circulation
formed in **choroid plexuses **of **lateral ventricles → **interventricular foramina → third ventricle → cerebral aqueduct (midbrain)→ 4rth ventricle → median aperture/lateral apertures (2) → subarachnoid space →central canal
Choroid plexus
networks of capillaries in the walls of the
ventricles.
Ventricles are lined by __ cells
ependymal
plasma is drawn from **choroid plexuses **through ependymal cells into ventricles to produce CSF
CSF is reabsorbed into blood by?
arachnoid villi - extensions of arachnoid that project into dural venous sinuses (sugerior sagittal sinnus)
Brain Stem (medulla, pons & midbrain) and Reticular Formation
Medulla Oblongata
continous with superior spinal cord
white matter tract contains all sensory & motor tracts between spinal cord & other parts of brain
white matter bulges on anterior - **pyramids **formed by large corticospinal tracts that pass from cerebrum to spinal cord
- common site of decussation of tracts - crossing over
**Centers of the Medulla Oblongata **
Vital centers:
**cardiovascular **
**respiratory **
also includes centers for vomiting, swallowing, sneezing, coughing and **hiccupping. **
houses 5 pairs of cranial nerves (VIII-XII)
portion of 3rd ventricle found here
**Midbrain (mesencephalon) **
Extends from the pons to the **diencephalon. **
Part of the ventricle found here- **cerebral aqueduct - **connects 3rd & 4rth ventricle
anterior part contains **cerebral peduncles **
posterior part - **tectum **
superior colliculli, inferior colliculi & substantia nigra
**Cerebral Peduncles - **paired bundles of axons in anterior part of midbrain
consists of?
**Tectum **
axons of the corticospinal, corticopontine and
corticobulbar tracts.
Tectum- situated posteriorly and contains 4 rounded elevations: 2
superior ones called superior colliculi and 2 inferior ones called inferior colliculi
Midbrain:
Substantia Nigra
large area with dark pigments. Help control subconscious muscle activities.
Loss of neurons here is associated with Parkinson disease.
Redc Nucleus of Midbrain
: Help control voluntary movements of the limbs
Midbrain contains cranial nerves….
III-IV
Reticular Formation
Extends from upper part of spinal cord, throughout brain stem & into
lower part of diencephalon.
Part of the reticular formation called the **Reticular activating System (RAS) **consists of?
consists of sensory axons that project to the cerebral cortex
S helps maintain consciousness.
**Cerebellum **
vermis
**anterior & posterior **lobes
**flocculonodular **lobe
cerebellar cortex
arbor vitae
2nd largest part of brain
central constricted area = vermis
anterior and posterior lobes control subconscious aspects of skeletal movement.
flocculonodular lobe - equilibrium & balance
cerebellar cortex - gray matter in form of parallel folds called folia
**arbor vitae - **tracts of white matter
**Cerebellar peduncles **
3 pairs - **superior, middle & inferior **
attach cerebellum to brain stem
functions:** coordinate movements, regulate posture & balance**
Thalamus
**intermediate mass **joins right & left sides of thalamus
(7) major nuclei: anterior, medial, lateral, ventral, intralaminar, midline, reticular
major relay station for most impulse reaching primary sensory areas
transmits info from cerebellum & basal nuclei to primary motor area
Hypothalamus
inferior to **thalamus **
consists of **mammillary body, median eminence, infundibulum, and # of nuclei. **
Functions of the Hypothalamus
Control of the ANS
production of hormones
regulation of emotion & behavioral patterns, eating & drinking, body temp, circadian rhythms
Epithalamus
small region superior to **thalamus **
consists of **pineal gland **that secretes **melatonin **which induces sleep
Cerebrum
seat of intelligence
**cerebral cortex - **gray matter
**Gyri **
**Sulci **
longitudinal fissure
cerebral hemispheres
Cerebrum
**Gyri **
**Sulci **
longitudinal fissure
cerebral hemispheres
**Gyri **- folds of cortical region
**Sulci - **shallow grooves between folds
**longitudinal fissure - **seperates cerebrum into right & left halves (contains falx cerebri)
**cerebral hemispheres- **connected internally by **corpus callosum **
Lobes of the cerebrum (4)
frontal
parietal
temporal
occipital
**Cerebral white matter **consists of ?
myelinated axons in (3) types of tracts
1) **association **
**2) commissural **
**3) projection **
myelinated axons in (3) tracts of cerebral white matter
1) **association - **axons conduct nerve impulses between **gyri **in same hemisphere
2) **commissural - **axons conduct nerve impulses to corresponding gyri in opposite hemisphere
3 groups - corpus callosum, anterior & posterior commissure
3) **projection - **axons conduct nerve impulses from cerebrum to lower CNS (thalamus, brain stem & spinal cord)
Basal Nuclei
(3) nuclei (masses of gray matter) deep within each cerebral hemisphere
**LENTIFORM NUCLEUS: **
***globus pallidus - **lateral to thalamus *
**putamen - **closer to cerebral cortex
**CAUDATE NUCLEUS **
corpus striatum = caudate + lentiform
Basal Nuclei
functions
Help initiate and terminate movements, suppress unwanted movements & regulate muscle tone.
Limbic system
A ring of structures on inner border of cerebrum and floor of diencephalon
- emotional brain - governs emotional aspects of behavior*
- also involved in olfaction & memory*
Components of the **limbic system **
**Limbic lobe - **cingulate, parahippocampal gyrus & hippocampus
dentate gyrus
**amygdala **
**septal nuclei **
mammillary bodies
**anterior & medial nucleus **
**olfactory bulbs **
Functional Organization of the Cerebral Cortex: **Sensory Areas **
**(5) **
Primary somatosensory area-
Primary visual area-
Primary auditory area-
Primary gustatory area-
Primary olfactory area-
**Cerebrum **
central sulcus
precentral gyrus
postcentral gyrus
**central sulcus **- seperates frontal & parietal lobes
**precentral gyrus - frontal: **primary motor area
**postcentral gyrus - parietal: **primary somatosensory area
- Primary somatosensory area- ___ gyrus.
- Primary visual area- ____________lobe.
- Primary auditory area- ____________lobe.
- Primary gustatory area- base of the __ gyrus.
- Primary olfactory area- ____________lobe
- postcentral gyrus
- occipital
- temporal
- **postcentral **gyrus
- temporal
Functional Organization of Cerebral Cortex: **Motor Areas **
**primary motor area - **precentral gyrus
**Broca’s speech area - **left cerebral hemisphere *(speech production) *
Functional Organization of the Cerebral Cortex: **Association **Areas
- *Somatosensory association area**- behind 1° somatosensory area.
- *Visual association area**- occipital lobe.
- *Auditory association area-** temporal lobe.
- Wernick’s area**- left temporal & parietal lobes (speech comprehension)*
- Prefrontal cortex-** anterior portion of frontal lobe.
Cranial Nerves
12 pairs
sensory, motor & mixed
name & roman numberic number to identify
Olfactory (I) Nerve
Sensory nerve.
Sense of smell.
Olfactory cells converge to become **olfactory nerve **that end in olfactory bulb.
Optic (II) Nerve
sensory
**vision **
**ganglion cells **in retina join to form **optic nerve **
Oculomotor (III) Nerve
motor cranial
originates in **midbrain **
supply extrinsic eye muscles to control movement of eye & upper eyelid
Trochlear (IV) Nerve
motor cranial nerve
**smallest **
originate in midbrain
controls movement of eyeball
Trigeminal (V) nerve
largest cranial nerve
**mixed **
(3) branches: **ophthalmic, maxillary & mandibular **
deal with sensation of touch, pain & temperature.
**motor axons **supply muscles of mastication
Abducens (VI) Nerve
motor cranial
originates in pons
cause abduction of the eyeball (lateral rotation)
Facial (VII) Nerve
mixed cranial
sensory portion - from taste buds of anterior 2/3 of tongue
**motor - **arises from pons & deal with facial expression
Vestibulocochlear (VIII) Nerve
sensory cranial
originates in inner ear
**vestibular branch - **impulses for equilibrium
**cochlear branch - **impulses for hearing
Glossopharyngeal (IX) Nerve
mixed cranial
**sensory: **taste buds of posterior 1/3 of tongue
**motor: **arise from medulla & deals with release of saliva
Vagus (X) Nerve
mixed cranial
distributed from **head & neck **into thorax & abdomen
**sensory: **sensations - proprioception & stretching
**motor - **arise from medulla & supply muscles of pharynx, larynx & soft palate that are involved swallowing & vocalization
Accessory (XI) Nerve
Motor cranial nerve.
Divided into cranial accessory and spinal accessory nerves.
Supplies **sternocleidomastoid & trapezius **muscles to coordinate head movements.
Hypoglossal (XII) Nerve
motor cranial
conduct nerve impulses for speech & swallowing
