HUBS1416 Topic 4 Lecture Peripheral Nervous System-1.pdf

School of Biomedical Science and Pharmacy College of Health, Medicine & Wellbeing The peripheral nervous system Advanced Human Bioscience HUBS1416 School of Biomedical Science and Pharmacy College of Health, Medicine & Wellbeing  Lecture Overview Part 1: Cranial nerves Part 2: Sp...

School of Biomedical Science and Pharmacy College of Health, Medicine & Wellbeing The peripheral nervous system Advanced Human Bioscience HUBS1416 School of Biomedical Science and Pharmacy College of Health, Medicine & Wellbeing  Lecture Overview Part 1: Cranial nerves Part 2: Special senses Part 3: Spinal nerves and general senses The nervous system can be divided into: Central and Peripheral Brain + Spinal cord Cranial nerves + Spinal nerves Including their branches The 12 pairs of cranial nerves Trochlear nerve (IV) Oculomotor nerve (III) Olfactory nerve (I) Trigeminal nerve (V) Optic nerve (II) Facial nerve (VII) Auditory (Vestibulocochlear) nerve (VIII) Abducens nerve (VI) Glossopharyngeal nerve (IX) Vagus nerve (X) Hypoglossal nerve (XII) Accessory nerve (XI) To tongue muscles sensory To sternocleidomastoid motor and trapezius muscles  Cranial nerve functions I Olfactory S Smell II Optic S Vision III Occulomotor M Eye movements, pupil constriction, raising eyelids IV Trochlear M Eye movements (Superior oblique muscle) V Trigeminal S&M Sensation to head & face, incl. gums and teeth. Movement of muscles of mastication VI Abducens M Eye movements (Lateral rectus muscle) VII Facial S&M Taste from anterior 2/3 of the tongue, Movement of muscles of facial expression VIII Auditory S Hearing, balance (Vestibulocochlear) IX Glossopharyngeal S&M Taste from posterior 1/3 of the tongue, Swallowing, salivary secretion X Vagus S&M Sensory & motor autonomic supply to most organs XI Accessory M Movement of neck muscles, voluntary swallowing & vocal cords XII Hypoglossal M Tongue movements Mnemonics to remember your cranial nerve names & numbers Oliver’s optimum occupation is tropical trigonometry – absolutely fascinating & awesome but glosses vaguely over accidental hypoglycaemia More (possibly easier ones) in the lectorial  The sensory information we are able to detect courtesy of our cranial nerves Cranial nerve Sensation I Olfactory (purely sensory) Sense of smell II Optic (purely sensory) Vision V Trigeminal (mixed) Pain and touch to head, face, teeth & gums VII Facial (mixed motor & sensory) Taste (front of tongue) VIII Auditory (purely sensory) Hearing and balance IX Glossopharyngeal (mixed) Taste (back of tongue) X Vagus (mixed) School of BiomedicalAutonomic Science and Pharmacy sensory Slide 9 Faculty of Health  The movements we are able to do courtesy of our cranial nerves Movement Cranial nerve Eye movements III, IV & VI Facial expressions VII Swallowing IX Contraction of gut, glands, etc. X Movement of neck & shoulders XI Tongue movements XII Slide 10 The special senses all make use of our cranial nerves CN VIII CN VIII CN VII & IX CN II CN I Smell (olfaction) l A chemical sense l What is the purpose of a sense of smell? l How many different smells can we detect? l Does our sense of smell develop with age? The organ of olfaction The olfactory receptors Olfactory nerve (CN I) Olfactory Volatile Olfactory cells substances bulb being smelt Vision l Humans rely heavily on their visual senses during normal function l We have extremely high acuity colour vision l Binocular vision gives us depth perception also l Our movement detection and low light vision is not as good as other mammals  The organ of vision The visual receptors Cornea Iris Lens Optic Rods Cones Aqueous nerve (for low light vision & (for colour vision) Retina movement detection) humour (CN II) Taste l Another chemical sense – different receptors on the tongue are specially attuned to a particular taste l What is the purpose of the sense of taste? l How many different tastes can we detect? Image from :The receptors and cells for mammalian taste, Chandrashekar.J, Hoon.M.A, Ryba.N. J. P. & Zuker.C.S. Nature 444, 288-294( 2006) Taste receptor cells Papillae What do the tastes tell us about the food? l Sweet – energy content l Salty – important electrolyte content l Umami (savoury) – amino acid content l Sour & Bitter – Potentially poisonous The organs of hearing & balance Semi-circular canals & otolith organs (balance) Ossicles Auditory nerve (CN VIII) Cochlea (hearing) Eustachian tube Ear drum (Tympanum) The receptors for hearing & balance Our senses of hearing and balance rely on specialised hair cells Hairs (cilia) project from the top of the cells, movements of the hairs provide the sensory signal moved by sound waves – hearing moved by head movements – balance (equilibrium) Image: Getty images  How does this organ signal head position? Hairs Otoliths Gel Head level Head tipped forward  Spinal nerves (31 pairs) Cervical plexus Cervical nerves (8 pairs) Brachial plexus Thoracic nerves (12 pairs) Lumbar plexus Lumbar nerves (5 pairs) Sacral nerves (5 pairs) Coccygeal nerves (1 pair) The spinal nerves emerge in pairs from the spinal cord between each vertebra Spinal cord Spinal nerve roots The cervical spinal nerves exit over the top of their corresponding vertebra, but the thoracic, lumbar and sacral exit under theirs  The spinal nerves branch to supply every region of the body, but the region each one supplies is strictly organised The region supplied by a particular spinal nerve and its branches is the segment of the body corresponding to the vertebral level at which the spinal nerve emerged This gives us predictable “maps” of which parts will be supplied by which spinal nerves – the dermatome and myotome maps  The Dermatomes Areas of the skin supplied by the sensory nerve fibres in each spinal nerve  The Myotomes The skeletal muscles supplied by the motor nerve fibres in each spinal nerve Sensory functions carried by the afferent neurons travelling in spinal nerves l Touch l Nociception (Pain) l Vibration l Thermoception l Proprioception l Muscle length l Joint position Touch l Touch receptors in the skin detect not only the presence of something against the skin, but also its form and texture l Density of touch receptors varies with the area – very high on fingertips and face but lower on the back Pain (Nociception) Signals actual or impending tissue damage Release of mediators from the damaged tissue stimulate or sensitise the free nerve endings that are pain receptors Proprioception l Sense of body position l Provided by two types of receptors: muscle spindles and Golgi tendon organs l Allows us to monitor movements and position without needing to look at ourselves  Muscle spindles detect changes in muscle length Sensory information also relayed to brain Muscle spindle senses stretch of muscle Muscle contracts in response to stretch Image modified from: Chris Macivor. Golgi tendon organs detect degree of “pull” on tendons Sensory information also relayed to brain Tendon organ senses stretch of tendon due to strong muscle contraction Muscle relaxes in response to excessive pull on tendon