Chapter 6 Perception Transform meaningless sensations into meaningful perceptions.
Sensations & Perceptions - Mans€¦ · Sensations & Perceptions Sensation-is an awareness of...
Transcript of Sensations & Perceptions - Mans€¦ · Sensations & Perceptions Sensation-is an awareness of...
Sensations & PerceptionsSensationSensation - is an awareness of sensory stimuli (external
& internal) in the brainPerception Perception - meaningful interpretation by the brain
(conscious understanding of sensory data)
Receptors• Definition of Sensory Receptors -
- Modified Structures (Free nerve ending or epithelial cells ) that detect changes in external & internal environment & send impulses to the brain.
Types of Receptors1) Receptors for special sense:1) Receptors for special sense:2) Receptors for 2) Receptors for cutanuouscutanuous sensation sensation
((ExtroceptorsExtroceptors) :) :3) Receptors for deep sensation 3) Receptors for deep sensation ((ProprioceptorsProprioceptors))4)Receptors for visceral sensation 4)Receptors for visceral sensation
((visceroceptorsvisceroceptors) :) :--5) Chemo5) Chemo--receptors: respond to changes in the receptors: respond to changes in the
concentration of solutes in Solvents concentration of solutes in Solvents 6)6) OsmoOsmo--receptors:receptors: of hypothalamus which of hypothalamus which
monitors blood osmotic pressuremonitors blood osmotic pressure
Receptors1) Receptors for special sense:Receptors for special sense:• A- Eye → vision → Retina (Rods & Cons).• B- Ear → (Hair cells).
*Hearing → Organ of Corti*Head position & movement→
1-crista ampullaris
2-maculae uterculi & sacculi
• C- Smell → olfactory epithelium. • D- Taste → Taste buds
2) Receptors for Receptors for cutanuouscutanuous sensation sensation ((ExtroceptorsExtroceptors) :) :--• A- Pain (Nocireceptors) → free nerve endings.• B- Temperature (thermoreceptors)
- free nerve endings- Hot sensation Ruffini corpuscles- Cold sensation Krause end bulbs
• C- Touch (Mechanoreceptors) : –Epidermal - Merkel's complex
Dermal - Papillary Layer -Miessner's corpuscles
- Reticular Layer--Free nerve endings (plexus of Bonnet )
-Paccinian corpuscles
-Ruffini corpuscles
-Krause end bulbs
RUFFINI CORPUSCLESite: Deep in dermis and hypodermis(numerous in the sole )
Shape : an Elongated corpuscle.Structure: It has a thin C.T. capsule.
Its Axial core contains Axially arranged collagen fibers whose displacement stimulates the nerve endings. The nerve fiber is Myelinated & penetrates the corpuscle side to give numerous non – myelinatedbranches which end between the collagenous fibers .
Function – Touch_
Sensation
KRAUSE END BULB• Site: Connective tissue of conjunctiva,• tongue and dermis of external genitalia• Shape: Round corpuscle• Structure: It has very poor C.T. capsule. Its nerve
fiber is Myelinated & penetrates the corpuscle side to give numerous non – myelinated branches that end by bulbous terminations.
Function – Touch_
&
Merkel’s ComplexSite:
In the basal cell layer of epidermis.LM:1- Merkel’s cell It is a modified
epidermal cell in the basal layer. This cells is slightly larger than the neighboring cells.
2-A sensory nerve fiber reaches the epidermis, it loses its myelin sheath and neurolemma. The naked nerve penetrates the basement membrane to terminate as a “ terminal disc”around “Merkel’s cell”
Function Touch sensation
MEISSNER 'S CORPUSCLESiteSite: In dermal papillae (numerous in fingers, soles, lips, external
genitalia , nipples and eyelids Shape & SizeShape & Size: an Oval corpuscle wide, with long axis
perpendicular to the surfaceStructureStructure: It has a thick C.T. capsule .
Its Axial core is formed of Transversally arranged modified Schwann cells and some inter – cellular collagenous fibers.
The nerve fiberThe nerve fiber is Myelinated & penetrates the corpuscle base giving 2 – 9 non – myelinated spirally running branches that end between the collagenous fibers.
Function Function light Touch
• The nerve fibers end around the connective tissue sheaths at the bases of the hair follicles, some fibers enter the outer root sheath to end around tactile cells.
•• Function Function light Touch
3) Receptors for deep sensationReceptors for deep sensation• A- Proprioceptors
-Tactile localization -Tactile discrimination- stereognosis,- deep pressure -vibration
• B- Kinesthesia ( motion sensation) - Paccinian corpuscle - muscle spindles - Tendon spindles - joint receptors.
Site:Site: 1 ) deep in dermis & hypodermis ( numerous in fingers , external genitalia and breast )
• 2 ) sites subjected to pressure e.g. inter – muscular septa , joint capsules, inter – osseous membranes , wall of urinary bladder and mesentery.
Shape : Shape : Oval corpuscle.Structure:Structure: A thin C.T. capsule separated from the corpuscle
by a sub – capsular space. Its Axial core is formed of 20 – 80 concentric layers of
flat modified Schwann cells joined together by desmosomesand separated by inter – cellular spaces containing collagenous fibers and tissue fluid , thus , in L . S .it exhibits an ONION like appearance.
The nerve fiberThe nerve fiber is Myelinated & penetrates the corpuscle at one pole to become non myelinated, then runs to the nearby of the opposite pole to terminate by an expanded terminal .
PACCINIAN CORPUSCLEPACCINIAN CORPUSCLE
PACCINIAN CORPUSCLEPACCINIAN CORPUSCLEFunction• A- Proprioceptors
-Tactile localization -Tactile discrimination- stereognosis,- deep pressure -vibration
B- Kinesthesia ( motion sensation)C- Deep touch
MUSCLE SPINDLE• Site:• 1) between the striated muscle fibers
specially near their insertion .• 2) numerous in small muscles doing fine
work e.g. Hand muscles.• Size:- 3– 5 m .m × 0.2 m.m.• Shape:- fusiform.• Structure:-• 1) Capsule:- stretchable connective
tissue .• 2) Intrafusal muscle fibres :-• (2 – 12) in number.• -Nuclear bag and Nuclear chain fibers
bathed in tissue fluid. • Each fiber is formed of a non - contractile
central part and contractile two poles.
MUSCLE SPINDLE
contains a chain of nuclei
contains a bag of nuclei
not expandedexpandedCentral Part
NumerousFewerNo
Thinner shorterThicker & longerSize
Nuclear chain fibers
Nuclear bag fibers
MUSCLE SPINDLE• 3) Innervations:-• Afferents:1ry (annulo – spiral ) ending → thick myelinated
fiber end around the central part.2 ry ( flower spray) ending → thin myelinated
fibers end around the sides of the 1ry afferents.
*The bags have only 1ry endings while the chains have 1ry & 2ry endings.
• Efferent:- fibers (fine fibers from anterior horn) supply the contractile poles of the intrafusal muscle fibers → more stretch and more firing of AFFERENT fibers.
•• Function:Function:-- a stretch receptor for kinesthesia a stretch receptor for kinesthesia and reflex control of muscle tone, and reflex control of muscle tone, movement and posturemovement and posture..
annulo – spiral ) ending
flower spray) ending
Efferent - fibers
• They differ from the muscle spindle in:• 1) No efferent fibers.• 2) Contain collagenous intrafusal fibers
enclosing the terminal ramifications of the afferent nerve. When the tendon becomes tense → compression of nerve fibers between the intrafusal collagenous fibers → impulse firing.
• They help in kinesthesia i.e. perception of movement & position of various parts of the body.
• Site: in the joint capsule and synovialmembrane.
• Type: - Ruffini and- pacinian corpuscles
4)4)Receptors for visceral sensation Receptors for visceral sensation ((visceroceptorsvisceroceptors) :) :--
toto transmit autonomic sensation transmit autonomic sensation from the stomach, U. bladder, from the stomach, U. bladder, ……. . etc etc ……Via the autonomic nervous Via the autonomic nervous system to the system to the C.N.S. C.N.S.
Q.1• In the following diagram of the Skin, identify
the structures labelled by the letters A-E?
Q. 2• What are the kinds of sensation which
affected by Diabetes Mellitus?