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Nervous System (Senses (Gustation components & pathway (Papillae…
Nervous System
Senses
Types of receptors based on origin
Interoceptor
Responds to stimuli withing the body
Proprioceptor
A receptor that uses internal stimuli to detect changes in body position (inner ear, tendons, muscles, joints)
Exteroceptor
Receives external stimuli (outside the body)
Types of receptors bases on stimulus type
Photoreceptor
Sensitive to light (responsible for vision)
Chemoreceptor
respond to chemical stimuli. Airborne chemicals, chemicals dissolved in food... (Taste and smell are chemoreceptors)
Thermoreceptor
Detect changes in temperature
Nociceptor
Sensitive to pain
Mechanoreceptor
Responds to mechanical stimuli, like touch or sound (generated by physical sound waves)
Baroreceptor
Responds to changes in pressure (to detect and help regulate blood pressure)
Eye components & visual pathway
Olfaction components & pathway
Olfactory epithelium
Superior to nasal concha, and area covered in olfactory receptors
Nasal Concha
Nasal cavity with concha to increase surface area to warm and humidify air. Air is first drawn into the nasal concha.
Olfactory bulb
Part of the forebrain directly superior to the cribriform plate. Full of bundles of cranial nerves, which extend through the cribri form plate to the olfactory epithelium
Olfactory sensory neurons
Olfactoy epithelium is psuedostratifed columnar epithelium full of sensory neurons for molecules to bind to and send olfactory signals.
Gustation components & pathway
Papillae
peg like projections from tongue mucosa where most taste buds reside.
Fungiform papillae
Small papillae, all over the tongue. Taste buds on apical surface
Foliate papillae
Running across the posterior surface of the tongue. Taste buds on the side wall
Vallate papillae
Arranged in large inverted V's near the back of the tongue
Vagus nerve (X)
Carries taste impulses from epiglottis and lower pharynx
Facial Nerve (VII)
Transmits taste impulses from anterior 2/3rds of the tongue
Glossopharyngeal Nerve (IX)
Carries sensations from posterior third of the tongue and the pharynx
Solitary cortex of medulla oblongata
Part of brains where all 3 gustation nerves transmit information. From there impulses go to the
Thalmus
and ultimately the
Gustatory cortex
Taste buds
Made of two major cell types
Gustatory epithelial cells
have gustatory hair projection through the taste pore to the surface of the epithelium
Basal epithelial cells
Ear components and pathway
Auricle (pinna) gathers and amplifies sound waves
External acoustic meatus, tube running from auricle to ear drum.
Tympanic membrane (ear drum). Takes sound vibrations in the air and transfers those vibrations to auditory ossicles
Nervous System Organization
CNS main structures & functions
Structures: Brain and spinal cord
Function: Receive, process, and respond to sensory input
PNS main structures & functions
Structures: Cranial nerves (connected to, not part of the brain), spinal nerves (connected to not part of the spinal cord), and ganglia
Function: Gather sensory information from receptors and pass along to the CNS for processing
Somatic division
Motor signals associated with VOLUNTARY body movements like skeletal muscle
Autonomic division
Motor signals for INVOLUNTARY body function. Motor innervation of cardiac muscle, smooth muscle, most glands (not sweat)
Signal types
Motor (efferent): Signal output from the CNS
Sensory (afferent) : Signal input to the CNS
Neurons
Major components of a neuron
Nucleolus
Axon
Axon collateral: A branch of axon separating from the main axon
The long tail of a neuron that electrical signals run down
Cell Body
Dendrites
Small processes branching from the cell body to communicate with other cells
Chromatophilic Substance
Dense region of rough endoplasmatic reticulum and free ribosomes. Creates plasma membrane and proteins
Axon terminal. The very end of terminal branches. Release synaptic vesicles to communicate outside the neuron
Myelin Sheath
Plasma membrane of oliodenrocytes and schwann cells to insulate and speed up electrical transmission. Not around every axons.
Axon hillock
Conical shaped space where the axon leaves the cell body
Structural types of neurons
Bipolar
Only in some special sensory organs, like eyes. Have 2 processes, 1 axon, 1 dendrite
Unipolar
Neurons with a single process extending from the cell body. Are found in sensory neurons
Multipolar
Has 3 or more processes. An axon and many dendrites. Found in Autonomic ganglia as well as the CNS. Most abundant type of neuron.
Functional types of neurons
Interneurons
Only in the CNS. Between Neurons, multipolar.
Sensory Neurons (Afferent)
Detect stimuli and input to the CNS. Unipolar
Motor Neurons (Efferent)
Output from CNS. Multipolar
Anatomy of Nervous System
Nerve components
Perineurium
A wrapping of dense irregular connective tissue around many axons already covered in endoneurium
Endoneurium
a wrapping of dense irregular connective tissue around an axon and its schwann cells
Epineurium
Dense irregular connective tissue wrapping many nervous fascicles into one nerve
Axon
Long thread-like part of a neuron electrical signals run down
Schwann Cells
Supporting glial cell in the PNS that myelinates some axons
Fascicle
A bundle of axons. Gets wrapped in epineurium
Glial cells (type, locations, description)
Ependymal cells
Shaped like cuboidal/simple columnar epithelium. Ciliated apical surface with microvilli on the basal surface. Lines the ventricles of the brain and spinal central canal. Keeps cerebrospinal fluid circulating within the ventricles.
Satellite cells
Found in ganglia (cluster of neuron cell bodies), supports neuron cell body and regulates what goes in/out of the neuron
Microglia
Spider shaped (many processes) phagocyte. Destroys invaded microbes and damaged/dying nervous tissue
Oliodendrocytes
Found in CNS, Wraps its plasma membrane around nmerous axons to create myelin sheath around multiple axons. myelin sheath insulates electric current and speeds up the signal transmission
Astrocytes
Most abundant glial cell. Many processes which contact other cells (axons and capillaries).Supportive and help maintain chemical balance for nervous function.
Schwann Cells
Found in PNS, covers 1 part of 1 axons, can wrap its plasma membrane hundreds of times to create thick myelin sheath.
Numerous axons surrounded by a schwann cell are considered non-myelinated