NURS 163 Chapter Notes - Chapter 10: Intervertebral Foramina, Prefrontal Cortex, Dorsal Root Of Spinal Nerve
PNS study guide 10 answers:
1. Difference between sensation & perception:
1. Sensation: awareness of stimulus (conscious or subconscious)
2. Perception: conscious interpretation of stimulus
2. Sensory receptors classified by type of stimulus:
1. Mechanoreceptors: detect mechanical pressure, stretching
a. EX: BP, stomach distention, vibration, proprioception (body position)
2. Thermoreceptors: detect changes in temperature
a. Location: free nerve endings
3. Nocireceptors: respond to stimuli potentially cause mechanical/chemical
damage (pain)
a. Location: in all tissues (except brain)
b. Most abundant in ET (skin, mucus) & CT (ligaments, periosteum, etc.)
4. Photoreceptors: detect light energy
a. Location: retina
5. Chemoreceptors: respond to chemical changes of solution
a. EX: smell, taste, regulate body fluid homeostasis
3. Sensory receptors classified by location:
1. Exteroceptors: at/near body surface
a. Receive external stimuli
b. EX: touch, pressure, temperature, pain, special senses
2. Interoceptors: walls of viscera & BV
a. Receive stimuli from w/in the body (viscera/BV)
b. EX: chemical change, tissue stretch/distention, thermoreceptors
3. Proprioceptors: in skeletal muscle, tendons, joints, ligaments, & CT covering
bones/muscles
a. Receive stimuli about: position, muscle tension, joint angle/
movement/speed
4-7. Simple receptors:
1. Free dendritic endings:
a. Location: almost everywhere, especially ET & CT
b. Unmyelinated process w/ knoblike endings extending into tissue
c. Respond to: pain, temperature, pressure
d. Specialized types:
i. Merkel (tactile) discs:
1. Light touch receptors
2. Location: epidermis: fingertips, pals, lips, genitalia
ii. Hair follicle receptors:
1. Location: plexus around hair follicle
2. Light touch receptors (from hair bending)
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2. Encapsulated dendritic endings:
a. Location: enclosed in CT capsule
b. Mostly mechanoreceptors
c. Various types:
i. Meissner’s tatile orpusles: (analogous to root hair plexus)
1. Location: dermal papillae of hairless skin
2. EX: tongue, genitalia, nipples
3. Light touch receptors
ii. Krause’s end uls:
1. Mechanoreceptors
2. Location: lamina propria of mucus membranes
iii. Pacinian (lamellar) corpuscles:
1. Single dendrite, in many layers Schwann, in CT capsule
2. Mechanoreceptor responding to deep pressure/stretch
3. Rapidly adapting (only respond @ onset then stop sending
signals about repeated stimuli)
iv. Ruffini’s orpusles
1. Highly branched dendritic endings in flattened capsule
2. Location: dermis, subQ, tendon, ligament, joint capsule
3. Respond to deep & continuous pressure
4. Slow adaptation w/ continuous input → brain: position &
coordination
v. Muscle Spindles
1. Location: all skeletal muscles
2. Proprioceptors in skeletal muscles
3. High muscle spindle concentration = fine motor activity
vi. Golgi tendon organs (GTOs)
1. Location: where skeletal muscle & tendon join
2. Proprioceptors of tendons
vii. Joint Kinesthetic receptors:
1. Proprioceptors for articular capsule stretch
2. Provide info about joint position & motion
8. Four main physiologic activities leading to sensation:
1) Stimulation:
a. Change in environment = activate receptor
b. Receptor specificity: certain receptors receive only certain stimuli
2) Transduction:
a. Sense receptor/organ converts stimulus energy → electrical energy (by
change in membrane potential in dendritic endings)
3) Impulse generation & propagation:
a. Threshold stimulus= sensory neuron propagates AP → CNS
b. Stimulus strength= high AP frequency (not high AP strength)
4) Integration:
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a. In specific CNS regions
b. Information interpreted
9-11. Transduction energy conversion process:
1) Stimulus = graded potential in receptor cell
a. (Usually) receptor potential =Na+ influx =depolarization
b. (Photoreceptors receptor potential =hyperpolarization)
2) Depends on location on 1st order sesor euro…
a. Receptor part of 1st order sensory neuron:
i. Graded potential: generator potential
ii. Ion channel= generator potential @ sensory ending → threshold
iii. =Activates voltage gated channels = AP!
1. NO NT release across synapse!
b. Receptor separate from 1st order sensory neuron:
i. Graded potetial: reeptor potetial
ii. Ion channel =receptor potential
iii. =Open voltage gated channel =NT release
iv. Ca2+ influx =more NT release
v. NT across synapse → 1st order neuron
vi. =1st order neuron → threshold
12-13. Receptive field: area the receptor monitors
A. Receptive field size depends on density of receptors
a. EX: densely packed receptors =smaller receptive field per receptor
B. Small receptive field= high acuity, discrimination
14. Discriminative sensation techniques testing sensory cortex:
1) 2-point discrimination: 2 prongs paperclip on skin, how close can 2 prongs get
until stimulus felt as just 1 prong?
2) Stereognosis: patient identifies object placed in their hand without looking
3) Graphesthesia: dra uer o patiet’s had, hae the idetif
4) Monofilament: (LEAP) assesses otto of feet’s sesitiit
15. Sensory adaption:
A. Decreased sensitivity over time to long-lasting, unchanging stimulus
B. Perception of stimulus decreased although stimulus remains
C. Decreased frequency of receptor/generator potential
D. Occurs @sensory level -or- CNS
16. Phasic vs. tonic receptors:
1) Phasic: fast-adapting receptors
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Document Summary
Reflex vs. reflex arc: reflex: rapid, automatic response to specific stimulus, reflex arc: neural pathway/circuit that produces reflex, serial processing. Stimulus: change in environment causing organism to react. Transduction: process by which sensory receptors produce neural impulses after receiving stimulus. Alpha motor fiber: innervates the extrafusal fibers of a muscle spindle. Gamma motor fiber: innervates the intrafusal fibers of a muscle spindle (only in contracting regions) Intrafusal fiber: modified skeletal muscle fibers w/in the muscle spindle w/ low levels of actin/myosin meaning it can only contract at ends of muscle spindles when innervated by gamma motor neurons. Extrafusal fiber: (cid:272)o(cid:374)tra(cid:272)tile fi(cid:271)ers o(cid:374) the (cid:373)us(cid:272)les spi(cid:374)dle"s e(cid:454)terior i(cid:374)(cid:374)er(cid:448)ated (cid:271)(cid:455) alpha motor neurons. Ganglion: collection of nerve cell bodies outside the cns. Nucleus: collection of nerve cell bodies inside the cns. Somite: bulges of mesoderm that form on either side of the neural tube. Endoneurium: delicate, loose ct enclosing neurons axons/schwann cells. Perineurium: coarser ct binding groups of nerve fibers into fascicles.
