Week 4 Flashcards
Describe the 3 main types of somatic sensations:
Tactile, pain, proprioception
What somatic sensations are tactile and what kind of stimulus are tactile sensations
Light touch, deep pressure, temp, vibration, and tickle
Mechanical stimulus
Pain sensations are mediated by
nociceptors
Awareness of the position of your body: muscle, legnth, velocity of stretch, and muscle tension
Proprioception
What is the spinal reflex pathway (pain) and what level does it occur?
only at spinal cord level, activated by nociceptor, unconscious protective response
The spinal reflex pathway causes a primary sensory neuron to synapse with an interneuron that synapses to a motor neuron to cause…
reflex in skeletal muscle
What is the ascending pathway to the brain (pain)
Conscious awareness of pain sensations
First order pain neuron neurotransmitters in the ascending pathway to the brain are…
glutamate and neuropeptide P
What in the ascending pathway to the brain bind to 2nd order neuron and allow for signal transmission
glutamate and neuropeptide P
itch, pain, temperature, tickle; chemically gated- what nerve ending
Free nerve endings
slowly adapting, touch and pressure
Merkel disc
rapidly adapting, touch and low frequency vibration
Meissner corpuscle
slowly adapting, stretch and pressure
Ruffini corpuscle
rapidly adapting, high frequency vibration
Hair root plexus
mechanically gated, rapidly adapts, vibration
pacinian corpuscle
What are the two different modality-specific ascending somatosensory pathways
Dorsal column and anterolateral
receptors for touch, pressure, vibration, and proprioception (peripheral sensory receptors in spinal cord) in what somatosensory pathway
dorsal column
receptors for pain, temperature, itch, and tickle in what somatosensory pathway
anterolateral
Crossover occurs where in the…
Anterolateral vs. Dorsal Column
Ant: spinal cord, right away
DC: medulla
In the DC pathway, the 1st order neurons travel into spinal cord then into medulla where they
synapse with second order neurons then crossover
Describe how it is possible for us to differentiate between stimuli of different modalities in the same body part (i.e. fingertip). Consider this at the level of 1) the sensory receptors and 2) the neurons onto which they synapse in the ascending sensory systems.
Due to higher density and size of receptive fields and only 1 neuron synapses with a secondary neuron in ASS.
Explain how one might determine the location of a spinal cord injury based on the modality of sensation that is lost and the region of the body (both the side of the body and body part) where sensation is lost….
Touch, proprioception, and vibration would all be affected on the __
Pain, temperature, itch, tickle would all be affected on the__
- same side that the injury occurred, because they do not cross the midline in the spinal cord (travel up affected side)
- the opposite side that the injury occurred, because they cross the midline in the spinal cord (travel up unaffected side)
When endogenous opioids bind opioid receptors what are the 2 effects
- the release of substance P is blocked
- IPSP
In the endogenous analgesia system, incoming pain signals can be modified by
descending axons
endogenous analgesia system begins in the __, goes to the __, and ends in the __
midbrain (gray matter), medulla, spinal cord
Three type of neuropeptides released to create inhibition
enkephalins, endorphins, dynorphins
Signal starts in gray matter of midbrain and travels into the medulla, where it enters the spinal cord and synapses with an ___ in endogenous analgesic system
Inhibitory interneuron
Describe the homunculus and explain the significance of the size of the region of the somatosensory cortex devoted to a particular body part
The body “map” is maintained throughout the entire sensory pathway, amount of space in cortex is proportional to the sensitivity of that part
lots of receptors to detect fine touch in the __
hands
few receptors because no fine touch is needed in the __
thigh
The somatic division of the PNS sends signals to __, what kind of movement? Neurotransmitters involved?
skeletal muscles, voluntary, release of AcH
The autonomic division of the PNS sends signals to __, what kind of movement?
smooth muscle, cardiac muscle, and glands; involuntary
Explain the factors that contribute to stimulus localization and two-point discrimination; consider factors in the periphery (e.g. in the skin), and at the various levels of the somatosensory pathways.
Convergence of primary neurons on secondary neuron and size of the receptive field
Explain why two-point discrimination is better in some areas of the body surface than others, e.g., lips, fingertips versus back of the neck.
The larger the surface area (receptive field)= the less sensitive the area is
Explain the different cues the brain uses to compute depth perception
Where image falls on retina; relative size; visual field; lighting
an object closer to you falls on 2 different sides of your retina [when focusing on a distant object]; therefore the eyes are telling the brain the object is in 2 different places; brain knows this isn’t possible and assumes that the object is closer
Binocular disparity
Give two reasons why we are unaware of our blind spots during normal visual experiences.
1) Eyes are constantly moving, so the blind spot is constantly changing
2) Blind spot perceived different in eyes
Somatic division of PNS releases __ vs autonomic division of PNS releases ___
ach, norepi or ach
Cholinergic or adrenergic- Somatic? Autonomic?
Somatic= cholinergic
Autonomic= cholinergic or adrenergic
One neuron pathway for what PNS division
somatic- CNS to effector
Two neuron pathway for what PNS division
autonomic
Autonomic PNS is excitatory or inhibitory
excitatory or inhibitory
Somatic PNS is excitatory or inhbitory
excitatory
innervations of effectors is cholinergic in parasympathetic or sympathetic
Parasympathetic
innervation of most effectors is adrenergic in parasympathetic or sympathetic
Sympathetic
most sweat glands is cholinergic in sympathetic or parasympathetic
sympathetic
In the parasympathetic NS Pre and postganglionic neurons releases
AcH
In the sympathetic NS Pre and postganglionic neurons releases
Pre- ach
Post- norepinephrine
In Parasympathetic NS: Origin of preganglionic neuron
Origin of postganglionic neuron=
Origin of preganglionic neuron= brain stem and S2-4
Origin of postganglionic neuron= terminal ganglion
In sympathetic NS: Origin of preganglionic neuron
Origin of postganglionic neuron=
Origin of preganglionic neuron= thoracic and upper lumbar spinal cord (T1-2)
Origin of postganglionic neuron= sympathetic trunk ganglion, collateral ganglion, or adrenal medulla
Sympathetic NS: pre axon vs post axon length
Pre are short, and post are long
Parasympathetic NS: pre axon vs post axon length
pre are long, post are short
The density of sensory neurons signaling touch in fingertips is __ and receptive fields are __ than other parts
Higher, smaller
Amount of space in the somatosensory cortex devoted to each body part is…
Proportional to the density of receptors in that part
Sympathetic effectors preganglionic neuron vs postganglionic neuron
Pre: cholingeric
Post: adrenergic
