Lecture Notes: Senses, page 1 of 8

(slide 1) Lecture Notes: Senses I)(slide 2) Introduction: Sensory Receptors

A) ___

1) Function of receptive membrane and the stimulus (irritability) 2) Awareness of changes in the internal and/or external environment at the cellular level

B) ___ 1) Conscious interpretation of stimulus 2) Cerebrum—higher thought processes

C) (slide 2) Sensory Receptors: specialized cells

1) Receptive Membrane a) Respond to specific stimulus b) Generate an action potential

2) Stimulus a) Energy (light, temperature, pressure, stretch) b) Chemical/molecular: taste, smell, pain

D) (slide 4) Types of Sensory Receptors

1) ___

a) Respond to molecules dissolved in aqueous solution b) Example:

(1) taste—dissolved in saliva (2) Smell—dissolved in fluids of mucous membranes (3) pH H+ in blood plasma (4) CO2 in blood plasma

2) ___ a) pain receptors—respond to chemicals released from damaged cells

3) (slide 5) _ a) respond to mechanical force—pressure, vibration, stretch b) stretch: lungs inflate, BV wall stretch (BP) c) _

muscles, tendons, ligaments—joints, provide information about position based on stretch

d) _ stereocilia sway, direction of sway provides information regarding hearing and equilibrium

4) (slide 6) _ a) respond to changes in temperature

5) _ a) respond to different wavelengths (colors) of light b) rod: respond to dim light/black and white c) cones: respond to bright/color (red, green, blue)

Lecture Notes: Senses, page 2 of 8

E) (slide 7) ___

1) ___

2) monitors external environment

3) location: dermis

4) free nerve endings: pain, temperature

5) Light touch: Meissner’s corpuscles and Merkel’s discs

6) Deep Pressure: Pacinian corpuscles

7) Referred pain:

internal pain receptors respond to a stimulus but it is interpreted as skin pain a) example:

myocardial infarction and left arm pain

F) (slide 8) _ 1) degree of stretch / relaxation providing information on movement and position 2) allow us to maintain balance and posture 3) maintain muscle tone

II)(slide 9) Vision

A) Anatomy of the Eye 1) General

a) Hollow ball b) 1 inch diameter c) About ½ cerebral cortex involved in visual processing

2) 3 layers a) (outer) Avascular or Fibrous layer b) (middle) Vascular Layer c) (Inner) Neural Layer

Lecture Notes: Senses, page 3 of 8

3) (slide 10-11) Avascular or Fibrous Layer

a) ___ (1) structure: tough fibrous CT with

extrinsic eye muscles (movement)

(2) Function: (a) Protects internal structures (b) Holds shape (c) Anchors in orbit

b) (slide 12) ___

(1) structure: Transparent fibrous CT, avascular with lots of nerve endings (blink, pain, tears)

(2) function: allows light through (3) Can be transplanted and avoid

rejection

c) (slide 13) __ (1) structure: transparent mucous membrane covers anterior surface (2) Function: lubricant—keeps eye moist and rinses

4) (slide 14) Vascular Layer

a) __ (1) structure:

(a) Dark pigmented layer (melanocytes) (b) Posterior wall

(2) Function: absorbs light, prevents refraction/scattering

b) (slide 15) __ (1) structure:

(a) Colored (b) ‘Doughnut’ (c) Pupil (d) Smooth muscle

(2) Function: (a) __ (b) allows more light to enter in dim light (c) ___ (d) allows less light to enter when bright

Lecture Notes: Senses, page 4 of 8

c) (slide 16)__ (1) structure:

(a) Circular arrangement of smooth muscle (b) Suspensory ligaments connect to lens

(2) Function: (a) __ Changes shape of lens to focus

d) (slide 17) ___

(1) structure: Crystallin—clear flexible protein

(2) Function: _

Suspensory ligaments change shape Flat—distant vision, curved—near

(3) eyestrain: ciliary and pupillary muscle fatigue

(4) Normal vision: Snellen eye chart 20/20

e) __ Uneven curvature of the cornea and/or lens

f) __ (1) clear liquid supply nutrients/removes

wastes (2) produced continuously (3) glaucoma--blocked duct ↑pressure�

damage retina

5) (slide 18) Inner Tunic or Neural Layer a) __

(1) Not attached (2) Vitreous humor holds in place (lasts

lifetime) (3) Layered (4) Photoreceptors (fovea centralis—

cones) (5) Bipolar (neuron) cells (6) Ganglion cell axons form optic nerve to

carry AP to cerebrum b) __

(1) Where axons exit eye and no photoreceptors present so no vision possible

Lecture Notes: Senses, page 5 of 8

B) (slide 19)Vision: pathway of light 1) cornea 2) anterior segment/aqueous humor 3) Lens 4) posterior segment/vitreous humor 5) retina (fovea centralis) 6) optic nerve 7) optic chiasma 8) cerebral cortex (both hemispheres) overlap image

III)(slide 20)Hearing & Equilibrium

A) General Anatomy of the Ear

1) Outer ear

a) Structure:

(1) Filled with

(2) Pinna (3) External auditory

canal (4) Ceruminous glands

secrete earwax (traps/protects from dehydration)

b) Function: direct sound to middle ear

2) (slide 21)Middle Ear a) Structure:

(1) _

(2) _ Thin CT membrane separates outer and middle ear and Vibrates in response to sound waves

(3) 3 ossicles amplify sound waves by pounding on oval window

(4) Eustachian tube: connects middle ear to nasopharynx to balance pressure on both sides of the membrane to ensure tympanic membrane can vibrate

Lecture Notes: Senses, page 6 of 8

3) (slide 22) Inner Ear a) _

Moves in response to mechanical energy (sound and movements)

b) Equilibrium and balance—mechanoreceptors/hair

cells located within:

(1) _ (anterior, superior, horizontal)

(2) _

c) Hearing—mechanoreceptors/hair cells located within:

(1) _

B) (slide 23) Hearing:

1) Pathway of sound: a) sound enters auditory canal b) strikes tympanic membrane c) ossicles amplify vibrations and strike oval window d) cochlear fluid (endolymph) moves e) stereocilia on hair swells sway (threshold)

2) (slide 24) High versus low pitch a) hair cells nearest oval window sway�high

3) volume: number of AP generated

4) tone: interpretation based on the distribution of hair cells that are stimulated

Lecture Notes: Senses, page 7 of 8

C) (slide 25) Equilibrium: Sense of balance based on movement of endolymph

1) Dynamic Equilibrium: Semicircular canals a) structure

(1) each canal (anterior, superior, horizontal) provides information regarding a specific direction

(2) Hair cells stereocilia sway in response

b) Function: angular/rotational/movements in 3-directions

c) Motion sickness: continuous fluid movement

2) Static Equilibrium: Vestibule

a) structure: (1) Otolithic membrane covers stereocilia (2) Otoliths: Calcium carbonate stones within

membrane moves with gravity b) function: movement in one direction/gravity

IV)Chemical Senses

A) Taste

1) Structure: a) Taste buds: gustatory cells replaced every 7-10 days b) Papillae c) Adapt (3sec-5 minutes)

2) Function: Taste a) sweet: alcohol, lead salts (paint), sugars b) salt: metal, ions (NaCl, Potassium) c) sour: acids (vinegar) d) bitter: caffeine, nicotine, quinine e) umami: ‘beef’, MSG,

flavor enhancer

Lecture Notes: Senses, page 8 of 8

B) Olfaction (smell) 1) Structure

a) Olfactory cells—hair cells respond to specific molecules dissolve in fluids of mucosa (1) Located within Olfactory epithelium/roof of nasal cavity (2) Direct connection with limbic system (emotions/memories)

2) Flavor: combination of taste & smell