A&P Chapter 14 Cont- The Brain and Cranial Nerves

Consists of the Limbic System, Cerebrum & Cranial Nerves.

What are the 3 functions of the Limbic System?

• establishes the emotional states

• connects the cortex to the autnomic brainstem

• memory storage + retrieval

What are the 6 general components of the limbic system?

• Limbic lobe

• Hippocampus

• Amygdala

• Fornix

• Anterior nuclei of the thalamus

• Hypothalamus

Where is the limbic lobe located?

Central hemisphere next to thr diencephalon

What composes the Limbic lobe?

• Cingulate gyrus

• Dentate gyrus

• Parahippocampal gyrus

Hippocampus

The brains memory organizer. Especially important for learning + long term memory

Amygdala

the brains emotional alarm. Interacts w sensory info + can help regulate automatic body responses associated w emotions

Fornix

connection pathway ~ white matter tract that connects the hippocampus to the hypothalamus. Think of it as a communication cable.

Hypothalamus

can alert alertness, excitment, lethargy and sleep via efdects on the reticular formation.

Largest part of the brain

The cerebrum

Functions of Cerebrum

Main center for conscious thought, interpreting information, language, and voluntary movement.

Anterior thalamic nuclei

compoenent of limbic system

3 compoenents of limbic SYSTEM

• fornix

• anterior nuclei of thalamus

• hypothalamus

Structure of the cerebrum

• cerebral cortex

• Gyri

• Sulci

• Longitudinal cerebral fissure

Each hemisphere of the cerebrum is divided into regions called

Lobes

What structure divides the frontal lobe from the parietal lobe?

Central sulcus

What is the central sulcus bordered by?

• the precentral gyrus of the frontal lobe

• postcentral gyrus of the parietal lobe

What seperates the frontal lobe from the temporal lobe?

Lateral sulcus

What structure lies meidal to the lateral sulcus

Insula

What seperates the parietal lobe from the occipital lobe?

Parieto-occipito sulcus

Cerebral cortex

outer layer of cerebral hemispheres

Gyri

rounded elevations that increase the surface area available for cortical neurons.

Sulci

shallow grooves between gyri

What seperates the cerebral hemisperes

longitudinal cerebral fissure

What composes the white matter of the cerebrum

• association fibers

• commisural fibers

• projection fibers

What are association fibers and what are the 2 types

• connect regions within same hemisphere

• Arcuate fibers and Longitudinal fibers

Arcuate fibers

Interconnect gyri within a lobe

Longitudinial fasciculi

interconnect the frontal lobe to other lobes in the same hemisphere

Commissural fibers and 2 types

Carry information BETWEEN hemispheres

• corpus callosum

• anterior commuissure

Projection fibers and a type

link the cerebral cortex w other parts of the nervous system

Internal capsule

Internal capsule

• all ascending and descending projection fibers

Basal nuclei

deep gray matter masses that help adjust + modify voluntary movement

Types of basal nuclei

• caudate nucleus

• lentiform nucleus (Putemen, globus pallidus)

Motor areas of the cortex

• Primary motor cortex a(precentral gyrus; voluntary skeletal muscle movement)

• pyramidal cells (neurons of primary motor cortex)

Sensory areas of the cortex

• Primary somatosensory cortex (Postcentral gyrus; recieves somatosensory information for touch, pressure, pain, vibration, and temperature)

Special sensory coticles

• visual cortex

• auditory cortex

• olfactory cortex

• gustatory cortex

Association areas

interpret sensory info or coordinates responses to it.

Association areas include:

• somatosensory association cortex

• visual association area

• auditory association area

Difference between the cortex’s and their respective association areas?

Cortex recieves while association INTERPRETS

Premotor cortex

coordinates LEARNED movements + creayes appropriate movement PATTERNS (frontal lobe)

Prefrontal cortex

integrates info from sensorty association areas and performs abstract intellectual functions such as predicting the consequences of possible responses.

Wernickes Area

language comprehension associated with the left cerebral hemisphere

Brocas area

Helps with speech production (also left hemisphere)

Damage to Brocas or Wernickes area can result in

• Aphasia (inability to speak or read)\

• Dyslexia (inability to comprehend or use written words)

Hemispheric Lateralization

functional differences between the left and right cerebral hemispheres.

Left cerebral hemisphere

• reading, writing, math

• speech and language

• decision making

Right cerebral hemisphere

• Sensory info

• recognition of faces and voices

fMRI and PET scans can:

visualize brain acitivty

EEG

records electrical activity using electrodes placed on scalp or brain

Beta waves

alert, active thinking

Alpha waves

awake, relaxed

Theta

Drowsiness + lighter sleep

Delta

deep sleep

Brain synchronization

Synch between the hemispheres involves a thalamic “pacemaker” mechanism

What are abnormal synchs associated with

seizures

Optic Nerve I

Olfactory

I. Olfactory Primary function

Special sensory - smell

I. Olfactory nerve pathway

Olfactory epithelium → cribriform foramina → olfactory bulbs

CN II

Optic Nerve

Optic nerve function

Special sensory - vision

Optic Nerve pathway

Retina → optic canal → optic tract → lateral geniculate body

Optic nerve III

Oculomotor nerve

III. Oculomotor nerve function

Motor - eye movement, pupil related function

Oculomotor nerve pathway

Midbrain → superior orbital fissure → most extrinsic eye muscles

CN IV

Trochlear Nerve

IV. Trochlear Nerve function

Motor - eye movement

Trochlear Nerve pathway

Midbrain → superior orbital fissure → superior oblique

CN V

Trigeminal nerve

V. Trigeminal Nerve function

Mixed - facial sensation and chewing

V. Trigeminal Nerve Pathway

Opthalamic, maxillary, mandibular divisions

CN VI

Abducens Nerve

CN VI Abducens Function

Motor- moving eyes away from nose

Abducens Nerve Pathway

Pons → superior orbital fissure → lateral rectus

CN VII

Facial Nerve

VII Facial Nerve Function

Mixed - facial motor functions and 2/3 of tongue anterior taste

VII Facial Nerves Pathway

Pons → internal acoustic meatus; major facial branches

CN VIII

Vestibulocochlear Nerve

CN VIII Vestibulocochlear Nerve Function

Special sensory - balance and hearing.

CN VIII Vestibulocochlear Nerve Pathway

Internal Ear → internal acoustic meatus → pons/medulla nuclei

CN IX

Glossopharyngeal Nerve

IX. Glossopharyngeal Nerves Function

Mixed- head/neck sensory and motor

CN IX Glossopharyngeal Nerve Pathway

Medulla → posterior tongue/pharynx and related targets

CN X

Vagus Nerve

CN X Vagus Nerve Function

Mixed - widespread visceral sensory/motor

CN X Vagus Nerve Pathway

Medulla → jugular foramen → thoracic/abdominopelvic viscera

CN XI

Accessory Nerves

CN XI Accessory Nerves Function

Motor - neck and upper back

CN XI Accessory Nerve Pathway

Spinal cord/medulla → jugular foramen → sternocleidomastoid/trapezius

CN XII

Hypoglossal

CN XII Hypoglassal Function

Motor - tongue movement

CN XII Hypoglossal Pathway

Medulla → hypoglossal canal → tongue muscles

Cranial reflexes are _______ responses, involoving sensory and motor fibers of cranial nerves

Autonomic

Are cranial reflexes monosynaptic, postsynaptic or both?

Can be either or

What are cranial reflexes useful for?

Assessing cranial nerves and brain regions.

Corneal reflex

corneal contact → CN V afferent → facial motor nucleus → CN VII efferent → blinking

Tympanic reflex:

loud sound → CN VIII afferent → inferior colliculus → CN VII efferent → reduced ossicles

Auditory reflexes:

sudden loud sound → CN VIII → brainstem/spinal motor nuclei → eye/head movements.

Vestibulo-ocular reflex:

head rotation → CN VIII → eye-movement motor nuclei → CN III, IV, VI → eyes move opposite the head to stabilize vision

Pupillary reflex:

CN II → superior colliculus → CN III → Pupil constriction

Consensual light reflex:

light in one eye produces pupil constriction in both eyes