Physiology ๐ซ Flashcards
what are combined somatic sensations?
Both superficial & Deep
- stereognosis
- Vibration senses
Test for crude touch
Cotton wool test
Pathway for pressure sensation
Dorsal column medial leminscal system
A side information: Minimal distance in lips is 2 mm
where are receptors for vibration sense present?
They are present in subcutaneous tissue in the muscle fibers
what are types of pain?
- Cutaneous
- Deep
- Visceral
Definition of cutaneous pain
- Pain sensation results from stimulation of pain receptors in skin
Test for cutaneous pain
Pin prick test
Definition of Deep pain
- Pain sensation results from stimulation of pain receptors in deep structures
- Like tendon, muscle, joint, ligament & Periosteum
Test for Deep pain
- squeeze or pinch the muscle of calf or biceps and ask the patient to report as soon as sensation becomes painful.
Definition of Visceral pain
- then sensation results from stimulation of pain receptors in viscera
Type of Pacinian corpuscle receptors
(mechano-receptors present in the skin, deep tissues involved in the sensations of touch, pressure and vibrations).
Compare between Rapidly adapting receptors & Slowly adapting receptors in terms of:
- Definition
- Example
- Other name
- Physiological significance
Classification of sensation
General:
- Arises from widely distributed receptors all over the body.
Special:
- vision
- taste
- smell
- hearing
- Sense of equilibrium.
Emotional:
- fear
- anxiety
- sadness
Com pare between Somatic sensation, Visceral sensation & Sensation organ in terms of:
- Arise from
- Crried by
- Examples
what is the definition of Touch sensation?
- It is a sense or feeling produced by application of light mechanical pressure to the skin
what happens if the intensity of touch increases?
if the intensity of the stimulus is increased, it is changing into pressure sense
what are the types of touch?
a) Fine touch.
b) Crude touch.
Definition of Crude touch
A type of touch sensation which is poorly localized
Stimulus in case of Crude touch
Diffuses ill defined object, Touching the skin with a piece of cotton or the touch of clothes.
Receptors of Crude touch
- Free nerve endings & hair end organs or follicle receptors โlocated in the hair folliclesโ
Afferents of Crude touch
- A-ฮด nerve fibers โ5-30 meter/secondโ.
- C fibers โ0.5-2 meter/secondโ.
Pathways of Crude touch
Pathway from the body:
- Ventro spino thalamic tract by A delta fibers
- Spino reticular tract by C fibers
Pathway from the face:
- Trigeminal pathway
whose transmission is faster, crude or fine touch?
The transmission of crude-touch is much slower than fine touch
Spatial arrangment of Crude touch
the spatial arrangement of the fibers in the pathway is poor
Does Crude touch inform the CNS accurately?
the impulses not inform the C.N.S accurately about the size & site of the crude-touch stimulus
Definition of Fine touch
It is a type of touch which informs us accurately about the shape, form and site of the tactile stimulus.
Stimulus of Fine touch
Well localized object to the skin as tip of pencil, head of a pin, teeth of comb
Receprors of Fine touch
- Meissnerโs corpuscles (rapidly adapting).
- Merkelโs discs (slowly adapting)
Afferents of Fine touch
A-beta rapidly conducting nerve fibers (30-70 meters/second).
Pathway of Fine touch
Fine touch impulses are transmitted by A-beta nerve fibers which travel through the Dorsal column โ medial lemniscal system (Gracil & Cuneate tracts).
Types of Fine touch
1-Tactile localization
2-Tactile discrimination
3-Stereognosis
4-Texture of materials
Definition of Pressure sensation
It is a sensation produced by the application of heavy mechanical stimuli to the skin (which can cause deformation of the different skin layers).
Receptors of Pressure sensation
a) Rapidly adapting receptors (Pacinian corpuscles).
b) Slowly adapting receptors (Ruffini multi-branched nerve endings); present in the deeper layers of the skin and responsible for the continuous information of the C.N.S about the pressure stimuli which play a role in the orientation of body position.
Afferents of Pressure sensation
as fine touch. (G & C)
Pathway of Pressure sensation
as fine touch. (G & C)
Types of Pressure sensation
Deep pressure sense:
- Discriminate between different weights without lifting them
Muscle tension sense:
- Discriminate between different weights with lifting them
significance of Pressure sensation
- Maintain posture
- Diffrentiate between different weights
Defintion of Vibration sensation
- It is a sensation of rhythmic pressure changes produced by the rapid repetitive stimulation of certain mechanoreceptors.
Stimulus of Vibration sensation
It can be produced by placing the base of vibrating tuning fork on the skin over bony prominence
Receptors of Vibration sensation
i)Meissnerโs corpuscles: can respond to frequencies to frequencies up to 200 cycles/second.
ii)Pacinian corpuscles: can respond to frequencies to frequencies up to 700 cycles/second.
Afferents of Vibration sensation
as fine touch (G &C)
Pathway of Vibration sensation
as fine touch (G &C)
Definition of Proprioceptive sensation
Is a sense that allows us to know the position and movement of every part of the body specially joints and limbs.
Receptors of Proprioceptive sensation
1) Muscle proprioceptors.
2) Joint proprioceptors.
Pathway of Proprioceptive sensation
- At conscious level
- At subconscious level
Types of Proprioceptive sensation
- Sense of position.
- Sense of movement.
- Muscle-tension sense.
- Deep pressure sense.
what are the types of Fine touch?
1-Tactile localization
2-Tactile discrimination
3-Stereognosis
4-Texture of materials
what is the definition of Tactile localization (topognosis)?
- It is the ability of the person with his eyes closed to perceive and determine accurately the site of a single point of fine touch.
Definition of Tactile discrimination (2 point discrimination)
Its the ability of the person or central nervous system to discriminate 2 points of fine touch applied simultaneously to the skin with the personโs eyes closed provided that the distance between them is greater than the minimal distance.
what is Minimal (Threshold) distance?
it is the distance between 2 points of fine touch below it the points are felt as a single point whereas at or above it the 2 points are felt as separate points
what does Minimal (Threshold) distance equal?
It equals 1 mm at tip of tongue, 3 mm at tip of fingers, 70 mm at the back.
where is Tactile discrimination more accurate? and why?
- On the extremities than on the proximal parts due to:
- Greater number of touch receptors, and subsequently a greater number of afferents
- Little convergence of afferents.
- Wide area of cortical representation and so good analysis and interpretation of sensory information.
what is the definition of Stereognosis?
Is the ability of the person with his eyes closed to recognize a familiar object by touching it e.g. recognition of a key, a pen or a coin.
what is the definition of Determination of texture of materials?
- Is the ability of the person with his eyes closed to recognize the nature of an object/textiles e.g. glasses and wood
which type of sense is Sense of position?
static sense
what does sense of position represent?
conscious orientation of the relative position of the different parts of the body to each other.
which type of sense is Sense of movement?
dynamic sense
what does Sense of movement represent?
means conscious orientation of the changes in the relative position of the different parts of the body to each other as regard, onset, termination, direction and the rate or velocity of this change
what are receptors of proprioception?
Compare between pathway of proprioception at conscious & subconscious level in terms of:
- Center
- Function
- Pathway
Definition of Thermal sensation
Is the sensation that enables us to detect temperature change, it includes warm and cold sensation.
Distribution of Cutaneous thermo receptors
- Number of cold receptors is greater than the number of warm receptors by about 3- 10 times.
- They are distributed in a punctuate fashion where, certain areas of skin contain warm receptors only and others contain cold receptors only with thermally insensitive areas in between.
what are the types of thermo-receptors?
- External (peripheral) thermoreceptors
- Internal (central) thermoreceptors
Compare between External (Peripheral) thermo-receptors and internal (Central) thermo-receptors in terms of:
- Types
- Location
- Detect
Compare between Warm & Cold Receptors in terms of:
- Morphology
- Number
- Afferent fiber
- Discharge impulse between
- Maximum discharge
Thermo-receptors at zero degree
all receptors stop discharge and this is one of the methods of anaesthesia.
Thermo-receptors at 45 degrees
the person feels โParadoxical cold sensationโ due to a brisk discharge from the cold receptors โParadoxical cold sensationsโ.
Thermo-receptors if temperature is less than 10 degrees
- Stimulate cold pain receptors
Thermo-receptors if temperature is more than 45 degrees
Stimulate warm pain receptors
what is the mechanism of stimulation of thermo-receptors?
what is the type of thermo-receptors?
Biphasic but mainly slowly adapting receptors
Adaptation of thermo receptors
Neural pathway of thermal sensation
Definition of Pain Sensation (Nociceptors)
- Unpleasant sensory and emotional experience associated with actual tissue damage.
Physiological significance of Pain Sensation
- Protective sense that direct the person to get rid of injurious stimulus.
what are the characters of pain receptors?
what is the type of pain receptors?
- They are morphologically one type โ free nerve endings.
- They are slowly adapting and even non-adapting receptors.
Specifity of pain receptors
- Highly specific โ respond to tissue damage & classified
according to type of painful stimuli into:
a. Mechanical pain receptorโ to mechanical stimulus.
b. Chemical pain receptorโ to chemical stimuli
c. Thermal pain receptor โ respond to excess temperature โ (<10ยฐC &>45ยฐC)
d. Polymodal pain receptor โ respond to all above painful stimuli.
Threshold of pain receptors
high threshold โ need strong stimulus that cause tissue damage.
Distribution of pain receptors
Widely distributed all over the body:
a. More abundant in the skin.
b. Present in deeper structures (muscles - joints - periosteum).
c. Viscera contains a smaller number of pain receptors and even this few numbers are concentrated in serous membranes e.g. peritoneum, pleura, pericardium & meninges of the brain.
d. Absent from: Liver, lung, brain & bone
when do diseases that affect the viscera start causing pain?
- The diseases affecting the parenchyma of organs, may not produce pain early, but lateral when they invade the serous covering they cause severe pain.
Definition of Pain Threshold
The lowest intensity of injurious agent needed to stimulate the pain receptors and produced pain sensation.
what are the methods of determination of the pain threshold?
- By pricking the skin with a pin.
- By compressing the skin against hard objects.
- Thermal method โmore accurateโโ by applying to skin to a thermostatically controlled metallic rod (Most of individuals begin to feel pain at 45ยฐC and all feel pain at 47 C and this is known as thermal threshold for pain receptors stimulation).
Feeling of pain in different people
- Most people feel pain at similar points but differ in their reaction to pain.
- Pain threshold is not the same in all individuals.
what is pain classified into?
what is the aim of sensory examination?
- To assess the integrity of sensory pathways
- To localize the site of lesion in central nervous system
steps of sensory examination
- First teach the patient about the test (in his own language), then perform the test.
- Should done quickly because patient get tired easily.
- Patient eyes should be closed to eliminate the effect of vision on sensation.
- Every part of the body should be examined systematically, so as not to miss one single dermatome i.e. done dermatomal.
- Compare both sides of the body (similar parts).
- Examine limb by starting distally and move proximally.
- Outline the boundaries of areas of sensory loss.
- In all tests, move from areas of sensory loss to areas of normal sensations since it is easier to the patient to detect when a sensation becomes increased than when it diminishes.
why should Sensory examination be done quickly?
- because patient get tired easily
why should the patient eyes be closed during Sensory examination?
to eliminate the effect of vision on sensation.
why should you move from areas of sensory loss to areas of normal sensation during Sensory examination?
- since it is easier to the patient to detect when a sensation becomes increased than when it diminishes
Steps of cotton wool test
- Ask the patient to close his eye
- Touch the skin with a small piece of cotton wool or soft brush or tissue paper
- Ask him to say yes every time he is touched
- Avoid regularly timed stimuli so that the patient does not anticipate the test
- Examine each dermatome
- Avoid dragging or moving the cotton wool across the skin or tickling the patient because moving the cotton wool will stimulate tickle sensation
- Outline the borders of any abnormal area of sensations
- Compare sensation of touch in a hairy areas and non-hairy areas of the skin
why you should avoid regulary timed stimuli during cotton wool test?
- so that the patient does not anticipate the test
why you should avoid dragging or moving the cotton wool across the skin during cotton wool test?
- because moving the cotton wool will stimulate tickle sensation
Test for tactile localization (Topognosis)
- apply gently head of pin to the skin ( bilateral, dermatomal, distal to proximal).
