8. Lectures 18, 19 Flashcards
What are the 3 important differences between the sympathetic and parasympathetic divisions of the ANS?
(Also study both of them on slide 3 lecture 18)
- Location of preganglionic neuron in CNS
- Location/organization if autonomic ganglia
- Neurotransmitter/receptor system at the synapse
Slides 3-5 lecture 18
What are the 4 cranial nerves parasympathetic fibers originating in brain distribute to?
- Oculomotor Nerve (CN III)
- The Facial Nerve (CN VII)
- The Glossopharyngeal Nerve (CN IX)
- The Vagus Nerve (CN X)
Vague nerve has a lot of innervation (splits and goes to multiple sections in body)
Slide 6 lecture 18
What are the 3 dates of the preganglionic sympathetic axon?
- It synapses within that segmental paracertebral ganglion (sympathetic chain)
- It travels up or down the sympathetic chain to synapse within a neighbouring paravertebral ganglion
- It enters the splanchnic nerve to synapse within one of the ganglia of the prevertebral plexus
Slide 7 lecture 18
What is the breakdown of the pathways of parasympathetic and sympathetic systems?
(Preganglion, postganglion, neurotransmitters)
Slide 8 lecture 18
Parasympathetic
Longer preganglionic fiber, releases ACh at N2 receptor at ganglion
Short post ganglionic fiber that releases acetylcholine at muscarinic acetylcholine receptor
Sympathetic
Short preganglionic fiber, releases ACh at N2 receptor at ganglion
Long post ganglionic fiber that releases norepinephrine at α and β adrenergic receptors
Which preganglionic and post ganglionic fibers have myelination?
Parasympathetic
Preganglionic- myelination
Postganglionic- myelination
Sympathetic
Preganglionic- myelination
Postganglionic- no myelination
What are the effects of parasympathetic and sympathetic pathways on main organs such as; Heart Lungs Eye Adrenal medulla
Parasympathetic
Heart- decreases rate, decrease force of contraction
Lungs- construction of bronchioles (airways), mucus secretion
Eye- construction of pupil, adjust vision for near sight
Adrenal medulla- none
Sympathetic
Heart- increases rate and force of contraction
Lungs- dilation of bronchioles, inhibition of mucus secretion
Eye- dilation of pupil, adjust vision for far sight
Adrenal medulla- stimulation of epinephrine and norepinephrine secretion
What is the adrenal medulla pathway?
Chromaffin cells have nicotinic ACh receptors
These chromaffin cells reside near blood vessels and release epinephrine into bloodstream
Epinephrine enhances the ability of the sympathetic division to broadcast its output through the body
Adrenal medulla is activated as part of sympathetic response
Slides 11-13 lecture 18
What are autonomic varicosities?
Axons of postganglionic neurons make multiple points if contact (varicosities) with their targets
Like octopus suction cups on tentacle but on smooth muscle in GI tract
What are the 3 contributors to contraction of smooth muscle?
ATP (nonclassic transmitter) and norepinephrine are co released Neuropeptide Y (NPY) contributes to contraction
All increase Ca2+, all cause contraction
ATP produces rapid contraction
NE produces moderately fast response
NYP produces slowest response
Slide 15 lecture 18
What 3 things contribute to dilation of smooth muscle?
Co-release of ACh, nitric oxide (NO), and VIP (vasoactive intestinal polypeptide) all decrease Ca2+ and cause dilation of smooth muscle
Slide 16 lecture 18
How is M-current inhibited by muscarinic Rs?
Happens in fight or flight (sympathetic)
Burst of ACh release during fight or flight activated ionotropic and metabotropic receptor
Membrane potential depolarizes
Slide 17 lecture 18
What is sensory transduction?
Sensory receptors concert environmental energy into neural signals
Sensation begins with sensory receptors that interface with the world, these receptors use energy from the environment to trigger electrochemical signals that can be transmitted to the brain
Slide 9 lecture 18
What are sensory modalities?
Seeing Hearing Touching Smelling Tasting
Pain
Balance
Body position
Movement
What is afferent versus efferent information?
Afferent goes from sensory receptor to the brain to be integrated
Efferent moves from brain after integration to effective
Slide 4 lecture 19
What are the 3 major functions of the somatosensory system?
- Proprioception- sense of oneself
Receptors in skeletal muscle, joint capsules, and skin generate conscious awareness of posture and movements - Exteroception- sense of direct interaction with the external world as it impacts the body (touch, pain)
- Interoception- sense of the function of the major organ systems in the body and its internal state
Interoceptors are primarily chemoreceptors (blood gases and pH)
What is the dorsal root ganglion (DRG)?
The cell bodies of neurons that bring sensory information from the skin, muscles, and joints lie in the dorsal root ganglia
Clusters of cells that lie adjacent to spinal cord
Primary sensory neurons of somatosensory system are clustered in the DRGs
DRG neurons are pseudounipolar and contain a peripheral process and a central process that synapses in the spinal cord (CNS)
Slide 6-7 lecture 19
Where is sensory information sent and stored?
Sensory information is sent to the thalamus and culminates in the cortex
Thalamus links sensory receptors and the cerebral cortex for all modalities except olfaction
Thalamus not only conveys sensory input to the cortex but it also acts as a gatekeeper for the information to the cerebral cortex (prevents or enhances the passage of specific information)
What types of modalities use cranial nerves and spinal nerves?
Cranial nerves- vision, taste, hearing
Somatosensory information- use spinal nerves
What is transient receptor potential channels (TRP channels)?
Structure?
What are they modulated by?
Non selective cation channels that may be permeable to Ca2+
Play central roles in sensory transduction pathways such as pain, itch, heat, taste, touch
Contain 4 subunits (tetramers)
Modulated or activated by wife range of stimuli including temperature, pH, mechanical stress, and interaction with chemicals
Slide 11 lecture 18
What are mechanisms receptors?
They sense physical deformation it’s the tissue in which they reside
Direct activation through lipid tension
Direct activation through structural proteins
Indirect activation through membrane structural proteins
Study mechanoreception in the auditory system on slides 14-15 lecture 19
Okay
What do the auditory inner hair cells and outer hair cells do?
Hair cells are mechanoreceptors that are specialized to detect minuscule movement along one particular axis
Involved in vestibular and auditory transduction
Hair cell is epithelial cell
Inner hair cells- transduce sound
Outer hair cells- amplify the signal
What is auditory sensation?
Sensation of hearing depends on the detection of vibration by the hair cells, which depends on mechanosensitive TRP channels
Auditory sensation is at forefront of our conscious experience
It is a versatile process that allows us to detect things in our environment (identify their nature, localize them, communicate with speed)
What is the perilymph?
What is the endolymph?
Perilymph- similar time cerebrospinal fluid, is extracellular fluid high in Na and low in K
Endolymph- bathing the sterovilli, is more like intracellular fluid high in K and low in Na
What are stereovilli?
What are tip links?
Stereovilli are narrower at their base and insert into the apical membrane of the hair cell, where they make a hinge before connecting to a cuticular plate
The ends of stereovilli are interconnected with very fine strands called tip links
What is positive deformation?
Positive deformation Goes towards longer strands High K in endolymph, low K in perilymph Opens apical channels leading to influx K and depolarization Upward frequency of vibration
Negative deformation
Goes toward shorter strands
Closes apical channels and leads to hyoerpolarization
Downward frequency of vibration
Slides 18-19 lecture 19
What is the cochlear amplifier and how does it work?
Depolarization contracts the motor protein presin, this causes outer hair cells to contract (electromotility)
This causes upward movement of basilar membrane
Outer hair cells act as a cochlear amplifier, sensing and rapidly accentuating movements of the basilar membrane
Slide 20 lecture 19
What does contraction of outer hair cells do?
What does elongation of outer hair cells do?
Contract outer hair cells = upward movement of basilar membrane (positive deformation)
Elongate outer hair cells = downward movement of basilar membrane (negative deformation)
Study hearing loss on slides 21-22 lecture 19
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