Chapter 10 physiology exam 3

• Monitor the internal and external environment (Heat, Cold, Pain, Pressure, Light, Sound...)
• Transmit signals from periphery to CNS for processing
• Critical for homeostasis

• PAIN
• respond to tissue damage

respond to light

Respond to mechanical energy

(touch, pressure, vibration)

respond to temperature changes

respond to changes in chemical concentration

• pain receptors that depolarize when tissues are damaged
• stimuli can include heat, cold, pressure or chemicals

response of sensors to constant stimulation

• Exhibit little adaptation
• Maintain constant firing rate as long as stimulus is applied

Exhibit sensory adaptation

Firing rate of receptor (#of action potentials) decreases with constant stimulus

• Stimulation
• Transduction
• Conduction
• Perception

• Awareness of environmental change by CNS
• Evaluation of nature and magnitude of stimulus

Relay information through a sensory pathway to the specific CNS region

• Application of stimulus
• (if the stimulus isn't strong enuff the nerve will not fire)
• once the nerve starts firing the stronger the stimulus the more rapid the firing
• The receptor is turning that stimulus into an AP that's called transduction

Turns the stimulus into a nerve impulse

• senses located over wide areas of the body
• information usually conducted to the spinal cord first (then possibly the brain)

example: tactile

• changes detected only by specialized sense organs in the head
• Information conducted directly to the brain
• relay info through cranial nerves

vision, hearing, smell...

• sensory receptors in muscles, tendons and joints
• Detect stretch in  the muscles, limb movements, position of body parts

Ex: spindle fibers, Golgi tendon organs

sensory receptors present in the skin

• touch and pressure
• heat and cold
• pain

• the minimum distance at which 2 points of touch can be perceived as separate
• measure the distance between receptive fields
• Some parts of the body have a higher number of receptors

may be myelinated or unmyelinated

• Sudden, sharp pain is transmitted by myelinated neurons
• Dull, persistent pain is transmitted by unmyelinated neurons

Nociceptors may be activated by chemical released by damaged tissues

• Detection of chemical concentrations in the oral cavity
• taste cells  depolarize when stimulated and release neurotransmitter to associated sensory neurons
• Information is relayed by cranial nerves VII facial and IX glossopharyngeal to the postcentral gyrus for perception

• sensors that help maintain body position and limb position
• which helps with balance, muscle memory coordination

allows you to feel your way around a pitch black room

• salty: high sodium
• Sour: high hydrogen, acidic
• Sweet: various organic molecules
• Bitter: toxins, quinine Alkaline
• Umami: glutamate, amino acid

• saltines and sour: depolarization of taste cell driven by direct flow of Na+ or H+ into the cell through ion channels
• Sweetness, bitterness and Umami: Binding of molecules to receptor proteins activates 2nd messenger pathways leading to depolarization

• the odorants bind to receptor proteins on the cilia
• AP travel to olfactory bulb

houses structures for senses of equilibrium and hearing

sound waves are turned into vibrations and then the vibrations are turned into AP

outer ear funnels and collects sound waves into the ear canal waves strike the tympanic membrane.

• made up of 2 distinct regions
• Cochlea anterior - Hearing
• Vestibular Appratus, posterior - equlibrium

• when a person's body is spinning, eye movements are toward the opposite direction of the spin to maintain a fixationpoint
• when the body comes to a stop, the cupula is bent by fluid inertia and eye movements are still affected
• The jerky eye movement produced is called Nystagmus
• Nystagmus can cause loss of equilibrium called vertigo

• fluid filled compartments in the inner ear
• Semi-circular canals distinguish the rotation of the head
• Otolith Organs distinguish the linear movement of head and orientation relative to gravity
• Sensory relay through VIII vestibulcochlear to the cerebellum and medulla oblongata

Equlibrium

linear movements of head and orientation relative to gravity

distinguishes the rotation of the head

• VIII vestibulocochlear
• to the cerebellum and medulla oblongata

stereocilia

bending stereocilia alters membrane potential

• bending towards the Kinocilium opens the ion channels, depolarizing the membrane
• Bending away from the kinocilium closes the ion channels, hyperpolarizing membranes

sound waves are not conducted from the outer ear to the inner ear

• may be de to wax, damage to the eardrum
• impairs hearing of all sound frequencies
• can be helped with hearing aids

nerve impulses are not conducted from the cochlea to the auditory cortex

• may be due to damaged hair cells from loud noises
• may only impair hearing to particular sound frequencies
• may be helped by cochlear implants
• AGE RELATED HEARING IMPAIRMENT

• transparent, lets light pass into the eye
• fixed convex lens (bends light inward)

thin ring of pigmented muscle in front of lens

• opening at center of the iris
• muscles alter pupil size, thus the amount of light passing into the eye

• Dilation opens the pupil to let in more light (Sympathetic)
• Constriction closes pupil in bright light (Parasympathetic)

• changing lens shape to focus light from objects at different distances on the retina
• Achieved by contracting ciliary body to different degrees

• Nearsightedness, distant object brought into focus in front of the retina
• eyeball is too long
• Abnormally high convexedness to cornea or lens
• Corrected with Concave Lenses

• farsightedness
• close object brought into focus behind the retina
• Shortened eyeball
• corrected with convex lens

• oblong shape to cornea or lens (not perfectly symmetrical curve)
• Different parts refract light to different degrees

Corrected with uneven lens that compensates for asymmetry

point where light from the center of the visual field is focused

High density of cone cells

Where optic nerve joins the eye

NO PHOTORECEPTORS

BLIND SPOT

more numerous than cones

• cannot distinguish different colors
• many rods converge onto single ganglion cells

• HIGHLY SENSITIVE TO LIGHT (low light levels detected)
• LOW VISUAL ACUITY (image not as sharp)

• Found mainly in Fovea Centralis
• Can distinguish among colors
• few cones cells converge on single ganglion cell

• LOW LIGHT SENSITIVITY (need more light to see with cones)
• HIGH ACUITY (image is sharper)

Retinal undergoes a photochemical change when struck by light

• Each one has 1 or 3 different opsins
• responds to different wavelengths of light
• Blue (S), Green (M), Red(L)
• enable color discrimination