1.5 Flashcards
Nucleus in CNS it like ___ in PNS.
ganglion
Reticular formation
Weblike
Extends throughout brainstem
Sends signals to entire cerebrum
Reticular formation function
Control of consciousness
Somatic and visceral sensation
Regulation of the respiratory and cardiovascular systems
Control of muscle tone
Posture maintenance
Movement
Brainstem structure
Tectum is dorsal to cerebral aqueduct (roof)
Tegmentum is ventral to cerebral aqueduct (floor)
Nuclei of the brainstem
Cranial nerve nuclei: most are in the brainstem
Other motor and sensory nuclei mediate complex life functions.
Connection points in the brainstem allow decussation, bilateral coordination, and coordination among multiple structures.
Brainstem as connection point: Hearing
- Auditory signal to the brainstem –> arrives at cochlear nucleus
- This connection is ipsilateral - Signal is transmitted to nuclei on both sides of the brainstem
- Each hemisphere receives auditory signals from both ears.
Medulla: location
Cranial end of spinal cord
Contains the distal portion of the 4th ventricle
Medulla: Important structures
Medullary pyramids
Pyramidal decussation
Olive
Medulla: Pyramidal decussation
Motor nerves from the cortex travel to the pyramids and cross at the distal medulla
Right hemisphere damage = left side effect
Medulla: Sensory decussation
Sensory fibers cross rostral to the pyramidal decussation. They form a tract called the medial lemniscus traveling to the sensory cortices
Pons: Location
Between medulla and midbrain
Ventral to cerebellum
Pons: Important Structures
Cerebellar pathways
Ascending and descending motor pathways
Function: bridge
Superior cerebellar peduncles
Form the roof of the 4th ventricle in the pons
Principally carries cerebellar signals to midbrain and thalamus
Middle cerebellar peduncles
Carries signals from pons to cerebellum
Inferior cerebellar peduncles
Connects the cerebellum with the medulla oblongata and spinal cord
Midbrain: Location
Rostral to medulla and pons
Ventral to cerebellum
Structure of midbrain
Ventral: cerebral peduncles
Rostral: tectum
Midbrain: Important Structures
Superior colliculi - visual coordination
Inferior colliculi - auditory localization
Substantia nigra - subconscious control of movement
Which cranial nerves would be spared by brainstem damage?
Olfactory (CN I)
Optic (CN II)
Accessory (CN XI)
Common causes of damage to CNS
Vascular disruption - stroke
Trauma
Pressure from a mass (usually intracranial)
Inflammation/infection
CN I
Olfactory nerve
Sensory
Collection of receptor cells are in the nasal mucosa
SVA: olfactory sense
The olfactory signal travels from the olfactory bulb, along the olfactory tract, to several areas on the ventral surface of the brain.
Test by identifying familiar odor
Olfactory signals
Direct connection to the cerebral cortex
- primary synapse is not the thalamus
Secondary connection to diencephalon, cerebellum
Profound influence on the limbic system
CN II
Optic nerve
Sensory
Covered in visual system
Test: visual fields
Optic nerve visual fields
CN III
Oculomotor nerve
1. Skeletal motor control of EOM (GSE)
- superior rectus
- medial rectus
- inferior rectus
- inferior oblique
2. Skeletal motor control of levator palpebrae (GSE)
3. PSNS (autonomic; rest and digest) to pupil and lens (GVE)
- sphincter puillea - constrict pupil
- ciliary muscle (lens accommodation to change focus)
Test upward, downward, and medial gaze; reaction to light
Motor
CN III, CN IV, CN VI
Extraocular muscles
Just skeletal muscle control of eye
CN V
Trigeminal nerve
Motor: muscles of mastication
Sensory: sensation of the face
Test corneal reflex: face sensation; clench teeth, push down on chin to separate jaws
CN VII
Facial nerve
Motor nerve: muscles of facial expression
Sensory: taste (SVA) anterior 2/3 of tongue
Test: close eyes tight; smile and show teeth; whistle and puff cheeks; identify familiar tastes
CN VIII
Vestibulocochlear nerve
Two divisions, both SSA
Vestibular: balance
Cochlear: hearing
Test: watch ticking; balance and coordination test
CN IX
Glossopharyngeal nerve
Motor: swallow, salivation (parotid gland)
Sensory: taste and general sensation, posterior 1/3 of tongue; gag reflex sensation
Test gag reflex and ability to swallow
CN X
Vagus nerve
Motor:
- PSNS supply to thoracic and abdominal viscera
- phonation
- gag reflex
Sensation: laryngeal area
Test gag reflex, ability to swallow and say “ahh”
CN XI
Spinal accessory nerve
Motor: head rotation and lateral flexion, shoulder raise
Test: resisted shoulder shrug
CN XII
Hypoglossal nerve
Motor: tongue movement
Test tongue protrusion
- if injured, tongue deviates toward injured side
The core of the brainstem contains the reticular formation. List its functions
Control of consciousness
Somatic and visceral sensation
Regulation of respiratory and cardiovascular systems
Control of muscle tone
Posture maintenance
Movement
What happens at the pyramidal (motor) decussation?
Motor nerves from the cortex travel to the pyramids and cross at the distal medulla
What happens at the sensory decussation?
sensory fibers cross rostral (cranial) to the pyramidal decussation
They form a tract called the medial lemniscus traveling to the sensory cortices (plural for cortex).
What are the primary tracts carried by each peduncle?
Ascending sensory and descending motor pathways
Which three cranial nerves are atypical and why?
Optic nerve – outgrowth of brain
Olfactory nerve – sensory pathways
Spinal accessory nerve – partly arises from the cervical spinal cord
CN IV
Trochlear nerve
Motor
Eye movement
Test downward and lateral gaze
CN VI
Abducens
Motor
Eye movement
Test lateral gaze
