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midbrain, pons medulla
pons, medulla, cerebellum
superior colliculus (visual & visual reflexes); inferior colliculus (hearing & auditory reflexes). Cerebral peduncles- white matter fiber tracts descending from cortex thru midbrain (corticospinal tracts)
basilar pons- provides bridges to cerebellum; tegmental pons- continuation of tegmentum from medulla to midbrain. Bridges to & from cerebellum contain many fibers called cerebellar peduncles.
“the bulb” has ridges that contain ascending & descending tracts. Lateral bulge called olive- the major nucleus in medulla. Ventral ridges (pyramids) contain corticospinal tract, a major descending motor tract (pyramidal tract)
cerebellar cortex made of gray matter; internal white matter called arbor vitae. 2 cerebellar hemispheres. Smooth coordination of muscle activity; sequential, complex movements; balance/vestibular system functions; postural stability & fixation; new motor learning
- Landmarks (beginning, ending, segments): continuation of brainstem. Begins at foramen magnum where CNS leaves skull. Terminates at conus medullaris at level of 1st or 2nd lumbar vertebrae. Other nerves trail down (cauda equina- descending peripheral nerves)
- Reflex arc: sensation travels up spinal nerve to spinal cord. Within spinal cord, connects via intercalated neuron to outgoing (motor) neuron. Motor nerve travels back out to limb & creates movement
major systems in nervous system
- Peripheral vs central: PNS- somatic & autonomic nervous system.
- Sensory-somatic: sensory organs for external stimuli. Autonomic:
- Sympathetic (fight or flight): accelerated heart rate, increased blood pressure, redistribute blood to core, dilate pupils.
- Parasympathetic (calming): slowed heart rate, decreased blood pressure, redistribute blood to periphery, constrict pupils
peripheral nervous system
- Ventral/motor/efferent: connected to muscles at myoneural junction & stimulate contraction.
- dorsal/sensory/afferent: carries info for a particular section of skin called dermatome
- Dura mater (tough mother)- most external covering just beneath skull. 2 layers- outer layer follows & is attached to skull; inner layer protrudes into long fissure b/w cerebral hemispheres (falx cerebri) & into space b/w cerebrum & the cerebellum (forming tentorium cerebelli) gaps where 2 layers separate are called venous sinuses.
- Arachnoid (spider) mater- web-like middle covering. Outer membrane adheres to inner surface of dura mater.
- Pia mater (pious mother)- thin, adheres to surface of brain & spinal cord.
- Entire surface of central nervous system is bathed by a clear colorless fluid (CSF). Produced by choroid plexus. Functions: buffering, buoyancy, excretion of waste products, endocrine median for brain
- Lateral ventricle: one in each hemisphere; connects to 3rd ventricle thru foramen of monro.
- Third ventricle: located b/w the 2 thalami. Connects to cerebral aqueduct in midbrain.
- Fourth ventricle: located b/w pons & cerebellum. Connects to central canal of spinal cord.
- Disorders: hydrocephalus, meningitis, subdural hematoma
arteries & veins
- Arteries- from heart/lungs to organs/muscles; carry oxygenated blood.
- Veins- to heart/lungs from organs/muscles; carry deoxygenated blood
major arteries, circle of willis, sinuses
- External carotid artery (ECA)- facial muscles; oral, nasal, orbital cavities.
- Internal carotid artery (ICA)- joins circle of willis; branches into anterior & middle cerebral arteries
- Vertebral arteries arise from subclavian artery; join to form basilar artery
- Circle of willis- equalizes blood flow b/w the 2 hemispheres; allows blood to continue to flow to all areas even if one vessel is blocked.
- Dural sinuses- sup. & inferior sagittal sinuses; straight sinus; transverse sinuses; sigmoid sinus.
blood brain barrier
Physiological mechanism that alters the permeability of brain capillaries, so that some substances are prevented from entering brain tissue, while other substances are allowed to enter freely. All molecules cannot pass thru; protects brain from disease; limits effect of many drugs on brain.
vascular pathology in CNS
- Strokes- ischemic (blocking); hemorrahig (bleeding)
- Arteriovenous malformation (AVM)- abnormal connection b/w veins & arteries
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- Olfactory I (sensory)- smell; olfactory bulb
- Optic II (sensory)- vision; optic tract
- Oculomotor III (motor)- eye movement; midbrain
- Trochlear IV (motor)- eye movement; midbrain
- Trigeminal V (both)- facial, controls jaw movement & chewing; pons [ophthalmic nerve, maxillary nerve, mandibular nerve]
- Abducens VI (motor)- eye movement; pons
- Facial VII (both)- taste, facial expressions; pons
- Vestibulocochlear VIII (sensory)- balance, hearing; pons
- Glossopharyngeal IX (both)- taste, swallowing; medulla
- Vagus X (both)- swallowing; medulla
- Accessory XI (motor)- neck muscles; medulla
- Hypoglossal XII (motor)- tongue movement; medulla
cranial nerves associated with
- speech- trigeminal, hypoglossal
- taste- facial, glossopharyngeal
- swallowing- glossopharyngeal, vagus
- sensation in head area
somatosensory & special sensory systems
- Somatosensory- pain, temp, touch, proprioception
- Special- vision, hearing, taste, smell, balance
typical somatosensory system are organized
- 1st order- transmits info from extremity (receptor) to CNS
- 2nd order- axon crosses midline & travels to contralateral thalamus
- 3rd order- travels from thalamus to ipsilateral somatosensory cortex
associated with free nerve endings or not
- Free nerve ending- touch/pressure, cold/warm, pain (thermal, mechanical, polymodal)
- Merkel- steady pressure/ texture
- Meissner corpuscle- flutter/ stroking
- Pacinian corpuscle- vibration
- Ruffini ending- stretch
- Anterolateral system: lateral spinothalamic (pain, temp); anterior spinothalamic (diffuse, light touch) [no 3rd order]
- Dorsal column-medial lemniscal system: fine touch (2pt discrim), pressure, proprioception; fasciculus gracilis (lower body), fasciculuc cuneatus (upper body) [contralateral]
- Spinocerebellar system: unconscious proprioceptive info to cerebellum; 2 order neurons, does not project to cortex
how sensation from head to face is handled
- Face: V- pain, temp, touch to face. VII- proprioception to face.
- Tongue: V- touch to anterior 2/3. IX- touch to posterior 1/3
- Palate: IX- sensory to soft palate
- Pharynx: IX- sensory to lateral & posterior pharyngeal walls; X- sensory to lower 2/3 of pharynx
- Larynx: X- sensory to most of laryngeal muscles
- Taste: transducer- taste bud. Facial, glossopharyngeal, vagus. Pathway: 1st order- unipolar; 2nd order- in brainstem, projects to thalamus. 3rd order- somatosensory. No decussation; totally ipsiplateral
- Smell: olfactory. Transducers: bipolar cells in epithelial lining; peripheral process has chemoreceptors. Pathway: no 3rd order, no decussation, ipsilateral
- Vision: receptors- rods & cones. Optic. Pathway: 2nd order (ganglion cell) neurons form optic nerve
- Auditory: receptor- ear. Vestibucochlear.
central vs peripheral & auditory brainstem vs auditory forebrain
- Peripheral- ear is receptor for sound- concerts air pressure waves into nerve impulses; VIII conducts nerve impulses to CNS.
- Central- auditory brainstem; auditory forebrain
- Forebrain- includes diencephalon & cerebral
auditory brainstem response (ABR)
tests the integrity of the auditory circuits of a person's brainstem