Tactile and position Flashcards
general VS somatic VS visceral sensations:
- general: arise from receptors distributed throughout the body, classified into:
- somatic: (soma = body), detect
touch, pain, pressure, temperature, and tension on the skin and skeletal muscles - viscera: referring to the viscera, the
internal organs of the body, specifically those within the chest (as the heart or lungs) or abdomen (as the liver, pancreas or intestines), detect blood pressure, temperature, pH & [O2] in blood, osmolarity of body
fluids.
special VS organic sensations:
- special: ensations of taste,
smell, hearing, equilibrium, and sight, only in special sense organs in the head region (a phenomenon known as (“cephalisation”) - organic: related to biological drives and emotions, e.g. thirst, hunger and sexual desire
def of sensations and types:
- def: sensations arise from somatic structures of all the body i.e. skin and deep tissues e.g. sk ms
- types: 1. Mechanoreceptive sensations: 2 types; Tactile e.g. touch, pressure, and vibration sensations.
Proprioceptive sensations e.g. sense of position and movement.
2. Pain sensation.
3. Thermal sensation; cold and warm
Steps of sensations:
- Stimulus – acts on a sensory
receptor. - Transduction – stimulus
causes an action potential in
sensory neuron. - Conduction – info. about
stimulus ascends by sensory
neurons via. Afferent path to
brain. - Perception – “awareness” and
evaluation of stimuli by the
brain
sensory stimuli = 4 major properties:
- Modality
- Location
- Intensity
- Duration
Modality of stimulus:
- Chemoreceptors a) chemoreceptors can detect ionic, glucose, oxygen, and carbon dioxide concentrations in the blood and tissue fluids. b) in special sensation, chemoreceptors are responsible for the senses of taste ( in oral cavity) and smell (in nasal cavity).
- Nociceptors a) detect pain or tissue damage due to excessive mechanical, electrical, thermal, or chemical forces. b) in somatic sensations, nociceptors can be found in the skin and many
visceral organs detecting tissue damages. - Thermoreceptors a) detect temperature changes. b) in somatic
sensations, certain thermoreceptors detect cold temperatures in the skin and some visceral organs, while other thermoreceptors detect high temperatures only. - Mechanoreceptors a) detect mechanical forces. b) proprioceptors
detect muscle tension. c) in special sensations, mechanoreceptors
in the inner ear detect the senses of hearing and equilibrium. - Photoreceptors a) detect light intensity. b) photoreceptors in the
eye detect light and colors of visual images.
location of stimulus:
- Receptive field- the area of the
skin surface over which stimulation
results in a significant change in
the rate of action potential. - Fingers and lips have a much
higher number of skin receptors
(small receptive filed) than the skin
on the back (large receptive field).
(le truc de plus c’est grand moins it has de receptors) = 2 point discrimination (slide 13)
Intensity of stimulus:
- Intensity is coded by number of receptors activated and frequency of AP coming from receptors.
- AP frequencies determine the
intensity of the stimuli, NOT the
amplitudes of AP.
(* Amplitudes of AP remain the same for the same type of receptors.)
- AP frequencies determine the
Duration of stimulus:
- Duration is coded by duration of APs in sensory neurons
- Sustained stimulation leads to sensory adaptation.
- Sensory adaptation: (le truc de smell goes away overtime)!! reduction in sensitivity in the presence of a constant stimulus caused by a decreased
frequencies of APs per second, thus lead to a decreased perception of sensation., e.g. smell and temperature.
Sensory adaptation:
- Phasic receptors → Rapidly adapting
receptors: APs decrease rapidly in the
presence of a constant stimulus. - Tonic receptors → Slow adapting or not adapting receptors: APs decrease slowly or do not decrease in the presence of a constant stimulus.
- Pain, vision, & proprioception receptors are slow adapting
Touch sensations:
- def: Feeling produced by application of light mechanical pressure to the skin
- 2 types: 1.Crude touch, 2.Fine touch
Fine touch: (def+ receptors + pathway)
Highly localized touch sensation produced by application of sharp object to the skin e.g. a tip of a pencil or a head of a pin or teeth of a comb
- receptors: Meissner’s corpuscule, Merkel’s disc
- pathway: dorsal column medial lemniscal pathway or gracile and cuneate tracts Fine Touch
Crude touch: (def + receptors + pathway)
Poorly localized touch sensation produced by touching the skin with diffuse ill-defined object e.g. a piece of
cotton or the touch of clothes.
- Receptors:
Free nerve endings (S)
Hair end organs (R)
- pathway: The anterolateral
spinothalamic tract
Pressure senses: (def + receptors + pathways)
a feeling produced by the application of heavy mechanical stimuli to the skin
- receptors: * Pacinian’s corpuscles (rapid adapt), * Ruffini’s ending (slow)
- pathway: dorsal column medial lemniscal pathway
Vibration senses: (def + receptors + pathways)
feeling of rhythmic pressure changes produced by the rapid repetitive stimulation of certain mechanoreceptors (tested by use of tuning fork)
- receptors: *Pacinian (R)
*Meissner’s corpuscles (R)
- pathway: Dorsal column medial lemniscal pathway
(slide 24)
Proprioceptive sensations: (def + receptors + pathway)
feeling of body movement and position, including motion of the arms and legs, resulting from stimuli received by stimulation of
proprioceptors in the muscles, tendons, joints, and inner ear
- receptors: a) Muscle spindle (slow adapting), b) Golgi tendon organ (slow adapting)
- pathway: Dorsal column medial lemniscal system or Gracile and Cuneate tract (slide 26 !!!)
pathways for transmission of sensory information:
Almost all sensory information enters
the spinal cord through the dorsal roots of the spinal nerves
the spinal nerves.
- Two pathways for sensory
transmission: dorsal column-medial lemniscal pathway and anterior spinothalamic tract
(slide 27)
dorsal column medial lemniscal pathway:
❖Conveys nerve impulses for
fine touch, pressure, vibration,
weight discrimination, two-
points discrimination, proprioception from the limbs, trunk, neck, and posterior head to the postcentral gyrus of the cerebral cortex (slide 28)
Anterolateral spinothalamic tract:
Conveys nerve impulses for
pain, thermal sensations,
crude touch, tickle and itch,
sexual sensations from the
limbs, trunk, neck, and
posterior head to the
postcentral gyrus of the
cerebral cortex (slide 29)
