chemical senses.ppt anatomy and physiology

ppt of chemical senses pathway

1. Refraction Of Light
Light rays, on passing obliquely from one
transparent medium to another of a
different optical density, are deflected
from their path

2. In the case of a convex surface such as a lens,
the angle of refraction depends on the degree
of curve.
Each parallel light ray hits the lens at a
different angle depending on its distance
from the center.
The rays entering the curved lens further
from the center are bent at a sharper angle
and those nearer the center are bent less.
At a fixed distance beyond the lens, all the
rays converge on a single point called the
focus .
This optical principle is used by the eye to
focus images on the retina.

3. Refraction Through Convex Lens

4. •Focal length of lens is the distance
from the centre of lens to the point
of focus of light from a distant
object.
•It is a function of
• -Refractive index of the lens
• -Radius of curvature of the lens

5. Refractive Media Of The Eye
•Cornea
•Aqueous humor
•Lens
•Vitreous humor

6. Changes occuring during
accommodation –Near Response
Change in curvature of lens
Constriction of the pupil
increases visual acuity
increases the depth of focus
Convergence of visual axes of the eyeball

7. •The range of object distances over which an eye can bring
objects into focus is defined by 2 points:
• ▪Far Point -the farthest point from the eye at which an
object can be clearly seen.
-For a normal eye, the far point is at∞.
-To focus on an object at the far point, the eye
should be relaxed ("relaxed eye").
• ▪Near Point -the closest point from the eye at which an
object can be clearly seen.
-For a normal eye, the near point is at25cm.
-To focus on an object at the near point, the eye
should be fully accommodated.

8. Near Point-Punctum proximum
•Is the nearest point at which an
object can be clearly seen, with the
eye being fully accommodated.
•7cms at 10 yeas of age
•83cms at 60 years of age

9. ROD-Structure
1.Outer
segment
2.Inner segment
3.Synaptic
terminal-
spherule

10. CONE -Structure
Outer segment –
conical
Inner segment
Synaptic terminal
-Pedicle

11. RODS CONES
Outer segment
Long , cylindrical Short , conical
High sensitivity Low sensitivity
More photopigments(Rhodopsin)Less photopigments
About 40,000 rhodopsinper diskLess per disk
Scotopic vision Photopicvision

12. RODS CONES
120 million per retina6 million per retina
One type of rhodopsinThree types of cones each with
different photopigments
Low acuity High Acuity
Absent in central foveaConcentrated in fovea
Highly convergent
pathways
Slight divergence in pathways
Achromatic-vision in
shades of grey
Chromatic (color vision)

14. Dark adaptation
•The process by which the person is able to see
the objects in dim light.
•Max. Duration: 20 mins
•Causes:
•Increased sensitivity of rods as a result of resynthesis
of rhodopsin
•Dilatation of pupil

15. Light adaptation
•The process in which eyes get adapted to
increased illumination.
•Max. period: 5 mins.
•Causes:
•Reduced sensitivity of rods
•Sensitivity of rods decreases due to breakdown of
rhodopsin.
•Constriction of pupil
•Reduces quantity of light rays entering the eye.

16. Visual pathway
•It is the nervous pathway that transmits
impulses from retina visual center in cerebral
cortex.
•Visual receptors: Rods & cones.
•First order neurons: Bipolar cells in the retina
•Second order neurons: Ganglionic cells in
ganglionic cell layer of retina.
•Third orders neurons: Are in lateral geniculate body.
Fibers reach to visual cortex

17. Course
•Optic nerve
•Optic chaisma
•Optic tract
•Lateral geniculate body
•Optic radiation
•Visual cortex

19. Light Reflex
Pathway

21. Smell -Olfaction

22. Olfactory mucous membrane

26. Terminations of Olfactory
Nerve
1. Pyramidal cells in
Piriform cortex ->
olfactory discrimination
2. Amygdala ->
Emotional aspects
3. Entorhinalcortex -
olfactory memories

28. Function of skin
Protective function:
–Protection from bacteria & toxic substances
Lysozyme
Keratinocyte: secretes cytokines, antimicrobial peptides etc
–Mechanical blow
–Ultraviolet rays: Exposures increases melanin secretion
Sensory function: largest sense organ, contains specialized cutaneous
receptors.
Storage: stores fat, water, chloride, blood & sugar
Synthetic: Vitamin D3
Regulation of body temperature:
Regulation of water & electrolyte balance: Excretion of water & salts
through sweat.
Excretory function: urea, salts & fatty substances.
Absorptive function: fat soluble substance & ointments
Secretory function: Sweat & Sebum

29. Body Temperature
Normal body temp. –37
0
C(98.6
0
F)
–Variation: 35.8
0
C & 37.3
0
C(96.4
0
F & 99.1
0
F)
–Axillary temp: 0.3-0.6
0
C lower than oral temp
–Rectal temp: 0.3-0.6
0
C higher than oral temp

30. Heat Balance
Heat production in the body
–Metabolic activities
–Muscular activities
–Role of hormones: Thyroxine& Adrenaline
–Radiation of heat from the
environment
–Shivering
–Brown fat tissue
Heat loss from the body
–Conduction
–Radiation
–Convection
–Evaporation-insensible
perspiration
–Panting

31. Regulation of body temperature
Regulated by hypothalamus
Two centres regulating body temp.:
–Heat loss centre: pre-optic nucleus of ant hypothalamus
–Heat gain centre: posterior hypothalamic nucleus

32. Mechanism of temp. regulation
When body temp decreases:
–Prevention of heat loss
–Promotion of heat production
When body temp increases:
–Stimulate thermoreceptorspresent in heat loss centre
–Compensation:
Prevention of heat production: by inhibiting mechanisms involved in
heat producion, such as shivering & chemical(metabolic) reactions.
Promotion of heat loss
–By increasing the secretion of sweat
–By inhibiting sympathetic centers in posterior hypothalamus

33. Increased adrenaline
secretion & metabolic rate
Normal body temperature
Increase in body temp.Decrease in body temp.
Stimulation of heat loss
centre(Ant hypothalamus)
Stimulation of heat gain
centre(Post hypothalamus)
Inhibition of sympathetic
activity
Increase in heat
production
No shiveringShiveringIncreases in sympathetic
activity
Cutaneous vasodilatation &
increased sweating
Cutaneous vasoconstriction
& decreased sweating
Increase in heat lossDecrease in heat
production
Decrease in heat loss
Decreased adrenaline
secretion & metabolic rate
Normal body temperature

34. Fever
Elevation of body temperature above the set point is called
hyperthermia, fever or pyrexia.
It is not an illness but body’s response to disease.
Rise in body temp beyond 42
0
C is called hyperthermia
resulting in damage to body tissues
Causes of fever:
–Infection, Hyperthyroidism, Brain lesions, Diabetes insipidusetc
Sign & symptoms:
–Headache, sweating, shivering, muscle pain, dehydration, loss of
appetite, general weakness etc
–Hyperpyrexia: Hallucinations, Irritability, Convulsions, Confusion etc.
Classification:
–Low-grade fever: 38
0
C to 39
0
C
–Moderate-grade fever: 39
0
C to 40
0
C
–High-grade fever: 40
0
C-42
0
C