Nervous System – Brain & cranial nerves

1. بسم الله الرحمن الرحيم Dr. Othman Al-Shboul Department of Physiology Nervous System – Brain & cranial nerves

2. “Relay station” and synaptic integrating center for preliminary processing of all sensory input on its way to the cortex The Thalamus • It screens out insignificant signals and routes the important sensory impulses to appropriate areas of the somatosensory cortex (e.g., attention to stimuli of interest)

3. Important link between the autonomic nervous system and the endocrine system via the pituitary gland Contains many nuclei and centers that regulate body temperature, hunger, thirst,fatigue, sleep, and circadian cycles The Hypothalamus

4. Masses of gray matter (neuron cell bodies) located deep within the cerebral white matter The Basal Nuclei • Functions: • Fine tuning muscle tone; inhibiting muscle tone throughout the body • Propermuscle tone is normally maintained by a balance of excitatory and inhibitory inputs to the neurons that innervate skeletal muscles)

5. Improper function: Parkinson's disease • Deficiency of dopamine, an important neurotransmitter in the basal nuclei • Signs and symptoms: • Increased muscle tone, or rigidity • Involuntary, useless, & unwanted movements, such as resting tremors (e.g., hands rhythmically shaking) • Slowness in initiating and carrying out different motor behaviors The Basal Nuclei

6. Cerebellum • Attached to the back of the upper portion of the brain stem, Lies underneath the occipital lobe of the cortex • Does not initiate movement, but contributes to coordination, precision, and accurate timing. • Fine tuning muscle tone; • Enhancing muscle tone throughout the body • Damage to the cerebellum does not cause paralysis, but instead produces disorders in fine movement, equilibrium & posture (intention tremor; • oscillating to-and-fro movements of a limb as it approaches its intended • destination)

7. Brain Stem • The brain stem is a vital link between the spinal cord and higher brain regions • Main functions: • The majority of the 12 pairs of cranial nerves arise from the brain stem • “Centers,” that control heart and blood vessel function, respiration, and many digestive activities. Important for brain arousal (being awake & alert)

9. Cranial Nerve I: Olfactory • Arises from the olfactory epithelium • Carrying afferent impulses for the sense of smell

10. Cranial Nerve II: Optic • Arises from the retina of the eye • Carrying afferent impulses for vision

11. Cranial Nerve III: Oculomotor • Functions: • Eye movement: motor innervation of extrinsic eye muscles (Superior rectus, Inferior rectus, Medial rectus, Inferior oblique) • Raising the eyelid • Constricting the iris • Controlling lens shape

12. Cranial Nerve IV: Trochlear • Function: Eye movement • motor innervation of extrinsic eye muscles (Superior oblique)

13. Cranial Nerve V: Trigeminal • Composed of three divisions • Ophthalmic (V1) • Maxillary (V2) • Mandibular (V3)  motor innervation for muscles of mastication •  brings sensations from the face

14. Cranial Nerve VI: Abducens • Function: Eye movement • motor innervation of extrinsic eye muscles (Lateral rectus)

15. Cranial Nerve VII: Facial • Motor innervation of muscles of facial expression • Innervation of lacrimal and salivary glands (submandibular and sublingual glands) • Sensory function is taste from taste buds of anterior two-thirds of the tongue

16. Cranial Nerve VIII: Vestibulocochlear • Fibers arise from the hearing and equilibrium apparatus of the inner ear • Two divisions – cochlear (hearing) and vestibular (balance) • Function: sensory – equilibrium and hearing

17. Cranial Nerve IX: Glossopharyngeal • Runs to the throat • Motor – innervates part of the tongue and pharynx, (also parotid salivary gland) • Sensory – fibers conduct taste and general sensory impulses from the posterior third of the tongueand pharynx

18. Cranial Nerve X: Vagus • The only cranial nerve that extends beyond the head and neck • Motor fibers to the heart, lungs, and visceral organs • Taste sensation

19. Cranial Nerve XI: Accessory • Motor innervation for the larynx, pharynx, and soft palate • Innervates the trapezius and sternocleidomastoid, which move the head and neck

20. Cranial Nerve XII: Hypoglossal • Innervates both extrinsic and intrinsic muscles of the tongue, which contribute to swallowing and speech • If damaged, difficulties in speech and swallowing; inability to protrude the tongue

21. Cranial Nerves

22. The END