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Nervous System (Senses (Receptors: stimulus type (Mechanoreceptors…
Nervous System
Senses
Receptors: stimulus origin
Exteroceptors
Stimulus origin is the environment; external
Interoceptors
Stimulus origin is internal organs; internal
Proprioceptors
Stimulus origin is muscle & their tendons, ligaments, joints; self
Receptors: stimulus type
Thermoreceptors
Receptors sensitive to temperature; cold & warmth receptors
Photoreceptors
Receptors sensitive to light
Chemoreceptors
Receptors sensitive to chemicals
Mechanoreceptors
Receptors sensitive to touch, pressure, vibration, stretch
Baroreceptors
Mechanoreceptors sensitive to blood pressure
Eye
Components
Fibrous layer
Sclera
Structure: dense C.T.; white
Function: anchor for extrinsic eye muscles; protective; gives shape
Cornea
Structure: transparent
Function: allows light into the eye; focuses light
Vascular layer
Choroid
Structure: black
Function: nourishes other layers; absorbs light; prevents light scattering
Ciliary body
Structure: muscle continuous with choroid
Function: changes the shape of the lens
Inner layer
Retina
photoreceptors; axons converge to form the optic nerve
Rods
Most abundant; sensitive to light & dark
Cones
Color vision; best in bright light
Optic disc
Blind spot; no photoreceptors
Macula lutea
Exactly opposite pupil; where there is the clearest vision
Fovea centralis
Within macula lutea
Lens
Location: posterior to cornea
Function: important in focusing light on retina
Iris
Location: anterior to lens, posterior to cornea; colored part of eye
Function: intrinsic muscle for dilation or constriction of pupil
Pupil
Location: center of iris
Function: hole that allows light to enter eye
Visual pathway
Cornea (focus light)
Lens (focus light)
Retina (photoreceptors)
Optic nerve (CN II)
Optic chiasm
Optic tract
Midbrain
Thalamus
Primary visual cortex (occipital lobe)
Olfaction
Components
Olfactory epithelium
Location: roof of nasal cavity
Structure: pseudostratified columnar epithelium w/ olfactory sensory neurons
Olfactory receptors
Olfactory nerve
Olfactory bulb
Olfactory tract
Limbic region (emotional brain)
Primary olfactory cortex (temporal lobe)
Pathway
Olfactory receptors
Olfactory nerve
Olfactory bulb
Olfactory tract
Brain
Gustation
Components
Taste buds (receptors)
Tongue, inner cheeks, pharynx, palate, epiglottis
Cranial nerves that transmit taste to brain
Facial nerve (CN VII)
Glossopharyngeal nerve (CN IX)
Vagus nerve (CN X)
Pathway
Receptor cells (taste buds)
Cranial nerves
Medulla oblongata
Thalamus
Primary gustatory cortex
Ear
Components
Outer ear
Auricle (pinna)
Gathers and tunnels sound waves; amplification
Middle ear
Tympanic membrane
Vibrates; transmits vibrations
Auditory ossicles
Transmits vibrations to cochlea (fluid filled space)
Vestibulocochlear nerve (CN VIII)
Cochlear nerve (hearing); vestibular nerve (equilibrium)
Transmits information from inner ear to the brain
Cochlear branch of CN VIII pathway
Cochlear nerve
Medulla oblongata
Pons
Midbrain
Thalamus
Primary auditory cortex (temporal lobe)
Organization
CNS
Structures
Brain
Spinal Cord
Functions
Receiving, processing, & responding to sensory input
PNS
Structures
Cranial nerves (brain)
Spinal nerves (spinal cord)
Ganglia (cluster of neuron cell bodies)
Functions
Gathers sensory info from receptors & passes it on to CNS
Motor (efferent)
Signals traveling away from CNS (output)
Somatic motor
Motor innervation mostly to skin, body wall (torso/trunk), skeletal muscles; (everything except ventral cavity contents)
Autonomic (visceral) motor
Motor innervation mostly to ventral cavity contents/organs; smooth muscle, cardiac muscle, glands
Sensory (afferent)
Signals traveling toward CNS
Somatic sensory
Touch, pain, pressure, vibration, temperature, & proprioception from skin, body wall, & limbs; **hearing, equilibrium, vision
Autonomic (visceral) sensory
Stretch, pain, temperature, chemical changes, & irritation in viscera; nausea & hunger; **taste & smell
Neurons
Major components
Cell body
Nucleus + nucleolus
Chromatophilic substance (rough ER & free ribosomes)
Dendrites (branches, transmit signal to body)
Axon Hillock (where axon becomes cell body)
Axon (long projection going away from body)
Axon Collaterals (axon branches)
Terminal Arborization (branching @ axon terminal)
Terminal boutons (axon terminals)
Nodes of ranvier (between myelin, some axons)
Myelin sheath (insulation on some axons)
Structural types
Multipolar
Many dendrites
Most abundant type
Bipolar
Two processes: single dendrite & axon
Unipolar/pseudounipolar
No dendrites, single axon
Functional types
Motor (efferent)
Multipolar
Motor (output) function
Sensory (afferent)
Unipolar
Sensory (input) function
Interneurons (association)
Multipolar
Association between neurons in CNS only
Anatomy
Nerve components (neurons=nerve cells)
Axon (nerve fiber); long projection of neuron
Myelin sheath (insulation coating around some axons)
Endoneurium (loose C.T. surrounds myelin sheath/individual axons)
Fascicle (bundle of axons)
Perineurium (fibrous C.T. surrounds each fascicle)
Epineurium (tough fibrous C.T. around each nerve)
Glial cells
CNS
Astrocytes
Location: most abundant, processes contact axons & capillaries
Function: help maintain proper chemical environment
Microglia
Location: throughout brain & spinal cord
Function: phagocytes, destroy invading microbes & damaged/dying nervous tissue
Ependymal cells
Location: in ventricles of brain
Function: simple cuboidal/columnar epi. w/ cilia to help circulate C.S.F. in ventricles
Oligodendrocytes
Location: target multiple pieces of different axons in CNS
Function: create myelination in the CNS (insulator, speeds up travel of signals)
PNS
Satellite cells
Location: surrounding neuron cell bodies in ganglia (neuron cell body clusters)
Function: supportive; help to regulate what goes into/out of neuron cell bodies
Schwann cells
Location: target one piece of each axon in PNS
Function: create myelination in the CNS (insulator, speeds up travel of signals)