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135 Cards in this Set

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  • Back
Afferent nerves
input to the CNS
(sensory nerves)
Efferent nerves
output from the CNS
(motor nerves)
Functional unit of the CNS
synapse (also known as a gap junction between two nerve cells where elec current passes)
advantages of the synapse
-ensure one way transmission
- modulate degree of excitation or inhibitation
Disadvantages of the synapse
- can transmit only at a rate of 0.5 - 1 KHz
- vulnerable to fatigue adn environmental influences
EPSP
-excitatory event that depolarizes post synaptic cell
This even is increased by gNA in and gK out
EPSP -
This event is decreased by gK out and gCl in
EPSP
This event is increased by Cl in and K out
IPSP
lateral inhibition
acts to sharpen the focus; enables a pinpoint are of stimulation to be identified
Increases S/N ratio
Interneurons
can inhibit or reduce input into higher order nerves
What are the effects of inhbiting interneurons on the Zones
Zone of facilitation and discharge are reduced
Zone of firing (discharge)
field where AP's occur in the post synaptic nerve
Zone of facilitation
the field where the post synaptic nerve is depolarized, but not above threshold (cant fire)
What does increased intensity do to subliminal fringe (zone of facilitation) and zone of discharge (firing)
it increases the size of both
What is an annulus of lesser activity (annulus of inhibition)
area that surrounds the area of stimulation (bug on arm example)
What causes annulus of inhibition around the bug (EPSP or IPSP)
smaller EPSP on adjacent nerves
How do feedback circuits work
compare desired action to an internal value (set point)
Ex. Fever
Negative Feedback
prevents over expression of the action; reacts in opposite direction of the perturbation ( reduces output or reduces speed of process)
Positive Feedback
reacts in the same direction as the pertubation (positive), increases output
what is a feed forward
initiate an action based on past memory,instinct, or anticipation (batter hitting ball)
feedback that is usually pathological and spirals to uncontrollable levels
positve feedback
Two types of sensory receptors
Phasic and Tonic
Tonic receptor
-maintains a specific rate of firing
- shows little fatigue
- no adaptation
Phasic receptor
-rate of discharge falls off with time
-can adapt
- Mechanical adaptation
- Ionic adaptaion
Mechanical adaptation of phasic receptor
stimulus strenght becomes less with time b/c stimulus energy is mechanically spread throughout receptor (big cap on receptor)
Ionic adaptation of phasic receptor
inc gK and Na inactivation decrease receptor potential below threshold
Labeled Line Principle
a nerve circuit from a specific receptor mediates ONLY that sensation (nerve from a warm receptor only feels warmth even if stimulated by pressure)
What is data transmission in nerves limited by
absolute refractory period
Data transmission in nerves is limited due to abs refractory period, then how can you increase data flow
-altered firing patterns (taste and smell)
- increased stimuli (stimuli coding)
Stimulus coding
Circuitry reduces stimuli to a certain number of AP's. For ex., if the environmental stimulus strength is 10, the receptor and CNS code it into 1 AP. then it might code stimulus strength of 1000 into 2 AP's.
Perception of stimulus strength
is not equal to actual stimulus strength
Weber Fechner Law - for extreme hi and lo stimuli
Perceived strength = stimulus strength + constant
Power Law - for normal range of stimuli
Logarithmic scale
What does Power law and Weber Law attempt to quantate
initial rapid rise in perception and plateau
Which nerves are most and least sensitive to pressure
Most Sensitive - A fibers
Least sensitive - C fibers
Which fibers have myelination
A fibers (heavy)
B fibers (light)
Which fibers are most sensitive to hypoxia
Most sensitive - B fibers
Least sensitive - c fibers
Which fibers are most sensitive to anesthetic
Most sensitive - C fibers
Least sensitive - A fibers
Due to myelination and larger area of A fibers
List the phasic mechanorecptors
Meissners Corpuscle (rapid acting)
List the tonic mechnoreceptors
Hair follicles, Rufinis Corpuscle, Merkels Receptors, Tactile discs (all are slow acting, tonic)
Mechanoreceptor associated with two point discrimination
Meissners corpuscle
Nociception
unpleasant sensation (pain)
Types of Nociceptors
Heat, Cold, Chemical, Mechanical
Heat Pain channels in the spinal cord
TRPV1
TRPV2
TRPV3
TREK 1
Chemical Pain channels in the spinal cord
TRPV1
ASIC
DRASIC
Mecahnical pain channels in the spinal cord
MDEG
DRASIC
TREK 1
Cold pain channels in the spinal cord
TRPM8
General sensory receptors versus nocicepters
pain receptors have a higher threshold and increase their firing rate in proportion to stimulus intesity
name the 2 stages of short duration pain- example is how dry ice burn pain expanded
Primary Hyperglesia
Secondary Hyperglesia
Hyperglesia means sensitivity
Primary Hyperglasia
antidromic conduction (away from CNS)
antidromic release of NT that sensitize the area of trauma and increases pain perception
Secondary Hyperglesia
Antidromic release (from CNS) of NT that depolarize nerves in uninvloved areas of trauma bringing them to threshold. Then perception of pain occurs in areas of undamaged tissue
transmitters of secondary hyperglesia in short duration pain
SP and CGRP from primary nerves
transmitter agents released by primary nerves in long duration pain
SP and Glutamate, these transmitters then stimulate AMPA and NMDA in secondary nerves
Long duration pain mechanism (long term hyperglesia)
- AMPA and NMDA receptors on dorsal horn cells are stimulated by GL and SP
- more depolarization occurs as pain increases
Where are taste receptors located
on the cilia of taste cells
What happens when taste receptor receives adequate stimuli
-taste cell releases transmitter agent
- transmitter agent depolarizes primary afferent nerve
- establishes a PARTICULAR pattern of AP's
Rapidly adapting senses
Taste and Smell
What are the components responsible for the enhancement of taste
Complementing and supplementing circuitry such as divergent and convergent circuits (we can smell and taste at same time)
diopter
strength of a lense
Formula for diopter
f^-1
degree of refraction
strength of the lens (diopter)
Increasing diopter number means...
increasing strength and refraction
Refraction or light bending of the cornea
48 Diopters and DOESNT CHANGE
Diopterage (strength or refraction) of the lens
varies from 15-29
which part of the eye adjusts the inital focus to optimal clarity
the lens using it varying diopterage (15-29)
Which part of the eye does the most light bending
cornea
what do rods and cones synapse onto
bipolar cells that synapse on ganglion cells
name the two types of bipolar cells in the eye
on center and off center
Bipolar cells that inhibit the visual pathway
OFF bipolar cells
which cells are stimulated by glutamate to inhibit ganglion
OFF bipolar cells
What cells stimulate the visual pathway
ON bipolar cells
Which cells are inhibited by glutamate, and depolarize in absence of glutamate
On bipolar cells
In the light what happens to cones and rods and glutamate
cones and rods repolarize and glutamate release stops
what seperates the scala vestibuli (top) and the scala typani (bottom)
the scala media
what is the scala vestibuli and scala tympani filled with
perilymph 0 mv
what is the scala media filled with
endolymph - abundance of K that makes it +80 mv compared to perilymph
what seperates the perilymph and endolymph
reticular lamina
what secretes the endolymph
stria terminalis
what is the potential of hair cells referenced to the perilymph
-70 mV
what is the cilia and apical regions of the hair cell embedded in?
what is the bottom bathed in?
top - endolymph
bottom - perilymph
What happens when kinocilia hair cells move
-spring loaded ionic gates open
- inward gK and gCa increased
what happens to hair cells if kinocilium is moved away from teh stereocilia
hair cells are depolarized
what happens to hair calls when kinocilium is moved towards the sterocilia
hair cells are hyperpolarized
tension is decreased and gates shut
Three types of auditory pathologies
-conduction deafness
- presbycuspus
- sensori-neural deafness
Conduction deafness
damage to the auditory canal, tympanum and/or ossicle (sclerosis of ossicle)
Conduction deafness
Air conduction is below normal
Bone conduction is normal
- partially recoverable due to bone conduction, but bone conduction is less efficient than air conduction
Presbycuspis
old age hearing loss
- stiffness of basilar or tectorial membrane
- affects high freqs more
Sensorineural pathologies
- most common form of deafness
- incurred by hair cell death or incapaciation of auditory pathway
Effects of sensoineural pathologies (exposure to loud noise) and ways to fix
- air conduction and bone conduction both below normal
- can be treated by amplifying sound so surviving hair cells are stimulated
- may soon be bale to bypass damaged nerves
vestibular apparatus
detects linear and angular acceleration (vertigo and motion sickness prevention)
Hair cells of the vestibular apparatus and their reactions to movement of the head
hairs are similar to hairs of the auditory apparatus
- nerves on one side will display inc firing
- nerves on the opposite side will display dec firing
Purpose of the outer hair cells
-increase inner hair cell sensitivity
- detect presence of sound (not source)
- contain actin and myosin
Inner hair cells
- less than outer hair cells but receive 90% of innervation
- detect sound and responsible for sound discrimination
Nystagmus
-occurs during linear, but mainly angular motion
- eyes move in direction opposite to motion
- this helps fix eyes on an object and orient themselves
what is felt when motion of endolymph ceases after end of motion
vertigo
What are 2 ways to test for vestibular function
Barany Test -
Caloric Test
Barany Test
spin on a chair and ensure eyes are moving in the opp direction to spinning
Caloric test
irrigate ear with hot or cold water, this sets up currents in endolymph
-fast towards warm side
- slow towards cold side
Monosynaptic Reflex
Stimulus: muscle is rapidly stretched
Response: contration
Simplest reflex where there is only one synapse between sensory afferent nerve and motor efferent nerve
Monosynaptic reflex
receptors of the monosynaptic reflex
Intrafusal fibers - nuclear chain and nuclear bag
Location of monosynaptic receptors
located in paralell with the muscle; best way to monitor changes in length
Fibers involved in monosynaptic reflex
1A fibers
Collection of interconnected nuclei in the CNS
basal ganglia
Function of Basal ganglia
- maintain posture
- initiate and maintain repetitive movts (walking, chewing)
During a monosynaptic reflex (myotatic reflex) in the agonist group, what happens to the antagonist group
the motor nerves to the antagonist group are inhibited via interneurons in the cord
Nucleus included in the basal ganglia
Striatum (caudate and putamen), Subthalamic nuclei, globus palidus
Purpose of the striatum nuclei in the basal ganglia
initiates gross intentional movements
Huntingtons chorea
symptons are chorea (snaking movts) and dementia
- lesions in GABA secreting nerves reduces inhibition of Striatum, causing uncontrolled movts
Purpose of the Globus Pallidus nuclei of the basal ganglia
- maintains posture
Lesions in Globus Pallidus
lesions reduce the ability of trunk muscles to maintain posture (usually causes an increase in movts similar to Huntingtons)
Purpose of the Subthalamic Nuclei of the basal ganglia
Inhibition of tone related to balance
lesions in the Subthalamic Nuclei
Dyskinesias showing flailing movts termed hemiballism and ballism (like slipping on ice movements)
Substantia Nigra (in basal ganglia)and Parkinsons
- caused by the interruption of dopamine nerves from the S. nigra to the striatum
symptoms of Parkinsons
-Rigidity (arm can not be held against resistance and drops in increments)
-Resting tremors (not present when pointing or using muscle)
- pill rolling (form of resting tremor)
Treatment for parkinsons
L Dopa
Functions of the Cerebellum
- maintain posture and balance (position)
3 Lobes of the Cerebellum
Posterior, Anterior, Flocculonodular
3 Main divisions of the Cerebellum
vestibulo
spinocerebellum (paleo)
ponto
Vestibulocerebellum
dominated by vestibular input and controls balance and eye movements
Neocerebellum
gets input from the cerebrum, visual, tactile and aural input
Lesions of the Neocerebellum
fine motor skill deficit
decompostion of movement
INTENTION TREMOR -over and undr shooting targer
Paleo(spinal) cerebellum
gets input from spinal cord
Lesions in paleo (spinal) cerebellum
increases antigravity tone in felines, may have multiple integrative fxns in humans
Lesions of the vestibulo or archi cerebellum
ataxia - lack of muscle coordination
Target of many addictive agents
septal area
Septal area = reward center
stimulation of dopamine D3 receptors, which in turn stimulate release of enkaplhins
Center of emotions
limbic system
Drugs affect diff parts of the lymbic system
Opiates, alcohol and barbits?
Cocaine, nicotine?
Ventral Tegemental Area- opiates, alcohol, barbits
N. Accumbens - Cocaine, nicotine
Where does body temperature control take place
hypothalamus
Body responses to heat
cooling - vasodilation and sweat gland activation, increased inspiration rate, decreased TSH
-water conservation by inc ADH
sensors of heat response system
warm detecting nerves and warm venous return to hypothalamus
febrile state
Hypothalmic set point is reset to a higher level
Disease when glucose cant enter cells
Dibetes I and II
(cells act like they are starved, yields inc appetite)