CNS - Lecture 2 Flashcards
What is modality of sensory input, give some examples
how a stimulus is sensed or perceived by our sensory organs.
eg. vision, sense of touch, hearing, movement
explain the relationship between sensory inputs and control
You can only control what you sense: without knowing the state of what you are controlling, you cannot control it
When a stimulus is processed, what determines which modality of stimulus it will respond to?
the structure of the sensory receptor
different modalities are processed…
in different parts of the brain
what is the adequate stimulus
the modality activating a given receptor
5 types of sensory endings in human skin (acronym)
MMFPR
- meissner’s corpuscles
- merkel’s corpuscles
- free nerve endings
- pacinian corpuscles
- ruffini corpuscles
meissner’s (tactile) corpuscles function
respond to light touch on the skin.
what is merkel’s corpuscles?
receptors that respond to touch
what do free nerve endings respond to
sensory receptors that respond to pain
Pacinian (lamellated) corpuscles structure and function
- contains slippery layers (lamellae) that slide over each other
- respond vigorously to vibration; distribute and amplify mechanical deformation
Ruffini corpuscles function
respond to skin stretch; also function as thermoreceptors
Types of ruffini corpuscles and their responses
warm type: increase firing rate as temperature rises
cold type: increase firing rate as temperature falls
describe type A sensory receptors and transmission
- specialized endings of afferent axons
- project directly to the spinal cord
describe type B sensory receptors and it’s transmission
- comprise first-order receptor cells responding to stimuli
- synaptically activate second-order cells close by, whose axons transmit information to the nervous system
first order cell characteristics and role
- generally small
- act as an intermediary between stimulus (stimulus energy) and second-order cells
what cells release neurotransmitters
first-order cells
what is the outcome of neurotransmitter release
activation of second-order cells
second order cells location and role
- close to the first-order cells in the sensory pathway
- receive signals from the first-order cells and transmit this information to higher brain centers.
The sensory axon resides and transmits information via
the dorsal root ganglion
process of the central branch of a sensory axon
enters the spinal cord and synapses onto a neuron cell body to transmit information to higher centers
where do sensory neuron axons terminate
enters the CNS and terminates in branches that make synaptic contact with neurons within the CNS
somatosensory receptors function and types
- cover the surface of the body and signal a variety of sensory modalities
- mechanoreceptors, thermoreceptors, nociceptors, proprioceptors and vestibular receptors
mechanoreceptors sense
local tissue deformation in skin and viscera
thermoreceptors sense
temperature in skin and brain
nociceptors sense
pain due to tissue damage
proprioceptors sense
movement & force in muscles and joints
vestibular receptors
respond to head acceleration and tilt
what is the basic mechanism of information transfer in both vertebrates and invertebrates
sensory receptors signal stimuli with action potentials
what nerve cell development happened in vertebrates but not invertebrates
development of the myelin sheath around nerve axons that increases conduction speed
T/F muscle spindle primary endings and golgi tendon are slow compared to postganglionic fibers, nociceptors and warmth receptors
False - Muscle spindle primary endings and Golgi tendon are the fastest and the autonomic postganglionic fibers, nociceptors and warmth receptors are the slowest
sensory stimulus processing intensity principle
as the stimulus intensity increases, the membrane potential at the initial segment of the sensory receptor’s afferent axon increases until action potentials are generated
explain what recruitment is
as stimulus intensity increases, the number of sensory receptors that are activated increases
explain what happens during stimulus-response
with a mechanoreceptor, membrane distortion causes tiny pores to open
Na enters the cell making the inside less negative
what is receptor potential and what triggers it
- the change in voltage at the initial segment
- triggered by membrane distortion in mechanorecpetors
explain the idea of frequency coding
the bigger the stimulus, the more the membrane channels in the sensory ending are distorted = more action potentials/sec (AP/s)
explain population code
the bigger the stimulus, the more sensory neurons are recruited into activity = more AP/s
explain temporal pattern code
the variability of firing rate (bursts vs steady firing) - may mediate certain types of sensation
sensory stimulus processing duration principle
some receptors that adapt very rapidly to stimuli while others adapt very slowly to stimuli
slowly adapting (tonic) receptors response and examples
- generate AP’s throughout the duration of the stimulus
- merkel’s corpuscles, free neuron endings, ruffini corpuscles
rapidly adapting receptors response and examples
- response only briefly each time the stimulus changes
- pacinian corpuscles and meissner’s corpuscles
