senses and perception Flashcards
a stimulus is converted to an electrical AP by which receptors?
specific sensory receptors
which pathways transmit sensory tactile information?
specific sensory pathways
which receptors respond to mechanical stimuli (touch)?
mechanoreceptors
which receptors respond to thermal stimuli (hot, cold)?
thermoreceptors
which receptors respond to noxious stimuli (pain)?
nociceptors
which receptors respond to chemical stimuli (taste, smell)?
chemoreceptors
which receptors respond to light stimuli (sight, vision)?
photoreceptors
which receptors respond to sound (hearing)?
mechanoreceptors
which receptors respond to limb position (spacial awareness)?
proprioreceptors
which receptors respond to blood pressure?
baroreceptors
what is a receptive field?
the distribution of sensory receptor nerve endings of a single neuron
give examples of areas of the body with small receptive fields
- tongue
- tips of fingers
give examples of areas of the body with large receptive fields
- shoulders
what is the relationship between size of receptor field and size of the area of therein designated to that part of the body?
areas with small overlapping receptor fields have larger regions of the brain (cortical representation)
define 2 point discrimination
ability to discern 2 separate mechanical stimuli
what is the relationship between the size of the 2 point discrimination and the size of the receptive field?
small 2 pt discrimination = area with small receptive fields = area with large cortical representation
when would someone perceive 2 points?
when stimuli is applied to 2 non overlapping receptor fields
if you activate 3 overlapping receptive fields, how many points will the individual perceive?
2
describe the transduction of stimuli to an electrical impulse
- stimulus
- change in receptor membrane permeability
- influx of cations
- depolarisation
- AP
how does the activation of a mechanoreceptor open an ion channel?
force applied to a receptor pulls cytoskeletal elements under the cell membrane opening channels
how does the activation of a chemoreceptor open an ion channel?
G protein cascade - binding of protein distant to receptor stimulates chain of events that open pore
how is the quality of the stimulus coded?
by type of receptor
how is the intensity of the stimulus coded?
- AP frequency
- number of activated neurons
in terms of measuring the duration of a stimulus, receptors can be classified into two groups, what are the?
- slowly adapting receptors
- rapidly adapting receptors
the distorted representation of proportion of the human brain dedicated to processing motor function is called?
sensory homunculus
what are receptors?
peripheral endings of sensory neurons
where are all sensory nerves collected?
dorsal root ganglion
give examples of cutaneous and subcutaneous mechanoreceptors and what they respond to
- meissners corpuscle (light touch)
- merkel disc (pressure)
- hair follicle receptor (hair deflection)
- pacinian corpuscle (vibration/pressure)
- muffins ending (pressure/hear)
where does the brachial plexus innervate?
- axillary (arm pit)
- musculocutaneous (bicep)
- radial (posterior upper limb)
- ulnar (elbow)
- median (upper arm)
bundles of axons are called what?
fascicle
each individual fascicule is surrounded by its own connective tissue, what is this known as?
perineurium
the connective tissue surrounding bundles of fascicule is called?
epineurium
motor neurons are composed of which type of fibre?
A alpha
rank the different types of nerve fibres from largest diameter to smallest
- A alpha
- A beta
- A delta
- c fibre
rank the different types of nerve fibres from fastest to slowest
- A alpha
- A beta
- A delta
- c fibre
what info do A alpha fibres carry?
proprioception (muscle)
what info do A beta fibres carry?
mechanoreception (skin)
what info do A delta carry?
pain and temp
what info do C fibres carry?
pain, temp and itch
sensory axons enter the CNS via what?
dorsal root
where are cell bodies of sensory axons located?
dorsal root ganglion
motor axons exit the CNS via what?
ventral root
at what level of the spinal cord id the dorsal root ganglia?
C2
which 2 branches of the trigeminal nerve have only a sensory function?
ophthalmic and maxillary
which branch of the trigeminal nerve has a motor function?
mandibular
sense nerves innervating the face arise from what nerve?
trigeminal
sense nerves innervating everywhere other than the face arise from what nerve?
spinal nerves
what is the name of the sensory pathway of the central nervous system that conveys sensations of fine touch, vibration, two-point discrimination, and proprioception from the skin and joints
dorsal column-medial leminiscal pathway
which type of nerve fibres are found in the dorsal column-leminiscal pathway?
A delta fibres
in the dorsal column-leminiscal pathway which neuron crosses over to the other side?
2nd order neuron
where are the 1st order neurons of the dorsal column-leminiscal pathway located?
dorsal root ganglia
in the dorsal column-leminiscal pathway, where do the first order neurons make axons with the second order neurons?
gracile nucleus and the cuneate nucleus in the lower medulla
in the dorsal column-leminiscal pathway, where do 2nd order neurons send their axons to?
thalamus
what is the name of the sensory pathway that carries info about discriminative touch and proprioception in the oral cavity?
dorsal/posterior trigeminothalmic tract
1st order neurons of the dorsal/posterior trigeminothalmic tract enter the medulla and synapse with 2nd order neurons where?
principal nucleus
where do 2nd order neurons of the dorsal/posterior trigeminothalmic tract synapse with 3rd oder neurons?
thalamus
in the dorsal/posterior trigeminothalmic tract, where do 3rd order sensory neurons terminate?
somatosensory cortex
1st order neurons of the dorsal/posterior trigeminothalmic tract travel along what ?
trigeminal ganglion
in the dorsal/posterior trigeminothalmic tract which neuron crosses over to the other side?
2nd order
where do 3rd order neurons of the dorsal/posterior trigeminothalamic tract in the thalamus ascend to?
sensory cortex
a sensory pathway from the skin to the thalamus then from the thalamus to the somatosensory cortex, carrying information about pain and temperature is known as?
spinothalamic pathway
the dorsal column-medial leminiscal pathway and the dorsal trigeminothalamic tract cross over to the other side at which region?
brainstem
the spinothalamic pathway crosses over to the other side where?
level of spinal cord
in the spinothalamic pathway, where does the 1st order neuron synapse with the second order neuron?
spinal cord
the neurons of the spinothalamic pathway are of two types, what are these?
A delta and C fibres
in the spinothalamic pathway, where does the 2nd order neuron synapse with the 3rd order neuron?
thalamus
where do 3rd order neurons of the spinothalamic tract in the thalamus ascend to?
somatosensory cortex
which sensory pathway carries info about crude touch, pain and temp from head, face and oral cavity?
anterior/ventral trigeminothalamic tract
1st order neurons from the anterior and posterior trigeminothalamic tract arise from where?
trigeminal ganglion
in the anterior spinothalamic tract, 1st order neurons enter the pons and synapse with 2nd order neurons, where do they synapse?
principal nucleus
in the anterior spinothalamic tract, 2nd oder neurons cross the midline and terminate where?
thalamus
the ability to recognise objects by feel alone is known as?
stereognosis
