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I. Peripheral nervous system: Cranial nerves, spinal nerves and the autonomic nervous system Somatic processes Autonomic processes II. The senses. 6. How many pairs of cranial nerves are associated with the human brain?. A. Eight B. Ten C. Twelve D. Fourteen E. Sixteen.
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I. Peripheral nervous system: Cranial nerves, spinal nerves and the autonomic nervous system Somatic processes Autonomic processes II. The senses
6. How many pairs of cranial nerves are associated with the human brain? • A. Eight • B. Ten • C. Twelve • D. Fourteen • E. Sixteen
Spinal nerves are grouped 31 pairs of mixed nerves 8 pairs of cervical 12 pairs of thoracic 5 pairs of lumbar 5 pairs of sacral 1 pair of coccygeal “serve” different regions of the body Dorsal root- sensory input Ventral root- motor output
Spinal nerves are organized and sorted in plexuses Cervical (neck) and phrenic nerves (diaphragm) C1-4 Brachial (C4-8, T1) upper limbs Lumbosacral (T12-S5) lower abdomen, lower limbs
7. Intercostal nerves would affect the: • A. Neck • B. Legs • C. Ribs • D. Hands • E. Vision
Autonomic system controls visceral functions Sympathetic Parasympathetic May act antagonistically on same organ Sympathetic- “fight or flight” Parasympathetic- “rest and recover” preganglionic, postganglionic fibers
8. Which of these would not happen in the fight or flight response? • A. Increased digestive activity • B. Increased heart rate • C. Increased breathing rate • D. Dilation of pupils • E. Nothing happens
What is sensed? (Chapter 10) Somatic senses-touch, temperature, pressure, pain (mechanical forces) Sound- another mechanical perception Vision- light Chemicals- smell, taste Sensory input is projected by cortex (we know what is being sensed)
With prolonged stimulation, some senses undergo adaptation Not pain receptors!
What causes pain (nocireception)? Tissue damage Oxygen deprivation (due to loss of blood flow) Referred pain is felt in viscera (nerves “serve” a variety of organs) Acute pain fibers are thin and myelinated Chronic pain fibers are unmyelinated Both can be triggered by the same stimulus
Pain is perceived in the thalamus, but interpreted by the cerebral cortex Pain is modulated by enkephalins and serotonin (produced by CNS) and endorphins (hypothalamus, pituitary gland)
9. Which of these is not detected by sensory receptors in the skin? • A. Pain • B. Pressure • C. Heat • D. Cold • E. They are all detected by sensory receptors in the skin.
Special senses Smell Taste- chemoreceptors Hearing- mechanoreceptors Vision- photoreceptors Special sensory organs
Smell- olfactory receptor cells Olfactory bulbs- interpretation in temporal lobes and frontal lobes Olfactory tracts direct impulses to limbic system
Taste- four major sensations sweet, sour, salt, bitter Other sensations- metallic, umami Depends on what type of receptor is engaged Pathway: facial, glossopharyngeal, vagus nerves Interpretive center in parietal lobe
10. Which of the following statements about smell and taste is false? • A. They (smell and taste) are detected by chemoreceptors. • B. The special sensory organs are embedded in cranial bones. • C. They are subject to adaptation. • D. They are detected by spinal nerves.
Hearing and equilibrium Structures Interpretive pathways
Organ of Corti is the hearing structure Hair cells are located there They can be depolarized upon stimulation Release neurotransmitters and stimulate nearby neurons (ultimately to vestibulocochlear nerve) Interpreted at temporal lobe (both of them)
11. The organ of Corti is located in the: • A. External acoustic meatus • B. Cochlea • C. Temporal lobe • D. Tympanic membrane • E. Vestibulocochlear nerve
Equilibrium Static- position of head Vestibule utricle-horizontal movement saccule- vertical Maculae contain otoliths (calcium carbonate) hair cells move against them
Dynamic equilibrium Semicircular canals in labyrinth Each contains a sensory region called crista ampullaris; help perceive movement Input from eyes and positional receptors Nystagmus- eyes continue to move even after spinning stops Vertigo- perception of movement after it has stopped
12. Equilibrium is affected by input from: • A. Eyes • B. Movement of head • C. Skeletal muscles • D. Cerebellum • E. All of the above
Vision eyes (why are they positioned in the head as they are?) lacrimal gland extrinsic muscles (lots of them) eye socket lots of vasculature
Retina Photoreceptors are located there Rods and cones associated with pigmented epithelium (absorbs “excess” light) Overlaid by neurons (see next slide) Rods- degree of light Cones- visual acuity, color Fovea centralis- cones only, no neurons
Disorders of senses Destruction of receptors and/or sensory neurons Temporary (infections, swelling) Hearing: conduction or nerve deafness Vision: shape of eye, plasticity of lens, muscle imbalances, distortion of lens, lack of cones (color blindness)…! Is correction possible?