6. sensory pathophysiopharmacology

touch, smell, hearing, vision, taste

dorsal column up to somatic sensory area of cerebral cortex

ability to know where touch is

# of receptors

superficial slowly adapting - markets receptors - pressure

superficial rapidly adapting - meissner receptors - feather

deep slowly adapting - Ruffini's corpuscles - skin stretch

deep rapidly adapting - vibrations

semi circular ear canals - balance

muscle spindles - position in space

has 1 for each dimensional plane

When your head moves around, the liquid inside the semicircular canals sloshes around and moves the tiny hairs that line each canal.

They run parallel to the extrafusal muscle fibers and act as receptors that provide information on muscle length and the rate of change in muscle length.

sensory cells translating chemical electromagnetic and mechanical stimuli into action potentials that our nervous system can make sense of

chemoreceptors

mitral cell picks up info from olfactory neuron -> olfactory tract -> olfactory cortex -> limbic system

emotional pathway triggers memories if smell is associated w/things:

danger -> triggers fight or flight

taste is 80 percent smell

as u chew food air is forced up nose so olfactory receptor cells are processing info at the same time as taste receptors

salty

sweet

sour

bitter

umami

all taste registers in all parts

taste receptors on tongue (epithelial cells)

gustatory or basal cells

sometimes referred to as pitch, is the number of times per second that a sound pressure wave repeats itself.

the relative strength of sound waves (transmitted vibrations), which we perceive as loudness or volume

SOUND WAVES enter the ear canal and cause the eardrum to vibrate. VIBRATIONS pass through 3 connected bones in the middle ear. This motion SETS FLUID MOVING in the inner ear. Moving fluid bends thousands of delicate hair-like cells which convert the vibrations into NERVE IMPULSES.

The otolith organs allow us to sense the direction and speed of linear acceleration and the position (tilt) of the head. The semicircular canals allow us to sense the direction and speed of angular acceleration.

when the body, the inner ear, and the eyes send conflicting signals to the brain -> doesn't know if you are stationary or moving

The number of waves which pass through a given point in one second

associated with our experience of brightness or intensity of color,with larger amplitudes appearing brighter.

the receptors in the retina responsible for your sense of sight

rods: vision at low light, low spatial acuity

cones: vision at higher light, color vision, high spatial acuity

1- photon of light hits photoreceptors on cones and/or rods

2- photoreceptors activate cellular mechanism causing opening/closure of Na+ channels

3- changes in voltage travels through bipolar cells and converge on ganglion cells

4- ganglion cells translate voltage changes into AP

5- AP relayed to cortex via CN II

1. sound waves amplified by auditory canal produce tympanic membrane vibrations

2. tympanic vibrations are mechanically amplified by malleus + incus + stapes

3. vibrations pushing oval window produce inner ear fluid motion

4. fluid motion pulls ion channels open on hair cells

5. ion influx produces action potentials relayed via CN VIII

eyelids: control light + anti particles protection

lacrimal glands: lubrication + wash out pathogens

conjunctivae: protective lining

fibrous: sclera + cornea

vascular: choroid + iris + pupil

inner: retina

red green blue

scotoma

strabismus

cataract

glaucoma

AMD

LISTEN TO ME

haemophilus influenzae

all kids receive analgesic

antibiotics not always necessary but amoxicillin best option

< 6 months: always antibacterial therapy

6 - 12 months: observe if illness not severe

> 2 years: antibacterial if severe, observe rest

breastfeed for first 6 months

decrease tobacco smoke exposure + pacifier use after 6 months

vaccination vs S pneumoniae + influenza

3+ cases/6months or 4+ cases/year

tympanostomy tubes -> good

influenza prevention + Tx -> benefits only in flu season

prophylactic antibacterial -> not recommended, small benefits

pain -> analgesic

PO antibiotics -> only severe + immunocompromised/diabetic

Topical antibiotics -> best efficacy:toxic

optimal ear hygiene

drying external auditory canal

avoiding earplugs

avoid removing ear wax

avoid inserting things

Iris: regulates the amount of light that enters your eye (controls pupil)

Pupil: the circular opening in the centre of the iris through which light passes into the lens of the eye.

Cornea: the transparent circular part of the front of the eyeball. It refracts the light entering the eye onto the lens.

Lens: a transparent structure situated behind your pupil, helps to refract incoming light and focus it onto the retina.

Choroid: the middle layer of the eye between the retina and the sclera, absorbs excess light so preventing blurring of vision.

Ciliary body: the part of the eye that connects the choroid to the iris.

Retina: a light sensitive layer that lines the interior of the eye (rods + cones)

Macula: a yellow spot on the retina at the back of the eye which surrounds the fovea.

Fovea: forms a small indentation at the centre of the macula and is the area with the greatest concentration of cone cells. When the eye is directed at an object, the part of the image that is focused on the fovea is the image most accurately registered by the brain.

Optic disc: the visible portion of the optic nerve, also found on the retina, also known as the 'blind spot’.

Optic nerve: leaves the eye at the optic disc and transfers all the visual information to the brain.

Sclera: the white part of the eye, a tough covering with which the cornea forms the external protective coat of the eye.

infection spreads to skull base, risk of meningitis and CN damage, rare fatal complication

elderly diabetic, immunocompromised

immediate referral to specialist

proper ear cleaning + drugs (ear drops + antibiotics)

10% of otitis externa

proper ear cleaning + acetic solution, if severe oral antifungals

most common/leading cause of blindness

characterized by increased resistance to drainage in the trabecular meshwork, even though the drainage angle between the cornea and iris remains open.

intraocular pressure (IOP) not always elevated

no Sx until significant optic nerve damage

TX: decreased IOP can stop progression/no cure

very rare/emergency situation

occurs when the iris bulges. The bulging iris partially or completely blocks the drainage angle. As a result, fluid can't circulate through the eye and pressure increases.

loss of vision within 48h

IOP rises rapidly

Tx: decreases IOP + corrective surgery

beta-blockers: decreased aqueous humor formation -> good for closed angle

prostaglandin analogs: increased aqueous humor formation -> less efficient for closed angle

alpha-adrenergic agonists: decreased aqueous humor formation

topical administration for all drugs

beta-blockers + prostaglandin analogs = most effective for acute decreased IOP

prostaglandin analogs = preferred -> less toxicity

alpha2-agonist brimonidine: best for long term decreases IOP -> can delay optic nerve damage

initiate therapy when diseases progresses from dry to wet ARMD -> decreases risk of advanced ARMD development, possible to partially restore lost vision

both travel via the anterolateral column

complex somatic + emotional experienced -> associated w/actual or perceived tissue damage

cognition, history, motivations...

gate control theory (GCT):

A-delta + C fibres (nociceptors) -> open the gate (substantia gelatinosa)

descending CNS pathways + non-nociceptor A-beta fibers -> partial or complete closing (ex: rubbing site of injury decreases pain sensation)

1- afferent pathways: PNS pain neurons -> spinal gate -> anterolateral tract -> CNS

2- interceptive centers: brainstem + cerebral cortex

3- descending efferent pathways: CNS neurons -> spinal gate (dorsal horn)

1- pain transduction

2- pain transmission

3- pain perception

4- descending pain modulation

harmful stimuli activates nociceptors (free nerve endings) -> increases AP

A-fibers -> rapid severe mechanical pain (high myelination)

C-fibers -> slow dull mechanothermal pain

1- PNS -> spinal cord interneuron: 1st order neuronal = A + C fibers

2- interneuron -> thalamus via anterolateral tract: 2nd order neurons = stimulatory or inhibitory

3- thalamus -> pain interpretation centers: 3rd order neurons

1- sensory-discriminative

location: somatosensory cortex

purpose: character, location, intensity...

2- affective-motivational

location: reticular formation + limbic system + prefrontal

purpose: conditioning/avoidance + emotional response to pain

3- cognitive-evaluative

location: cerebral cortex

purpose: modulation and analysis, compare pains, decrease it

open gate: feeling of pain increases

closed gate: feeling of pain decreases

excitatory (open gate): glutamate on AMPA + NMDA receptors

inhibitory (closed): GABA, glycine, serotonin, opioids, endorphins

excessive glu stimulation -> feels pain when it is not painful (no injury)

inflammatory mediators -> decrease pain threshold = pain sensation increases with actual injury

descending modulation from cortex: powerful inhibition of afferent pain signals

diffuse noxious inhibitory controls (DNICs): non noxious stimuli elsewhere decreases attention to major pain (ex: acupuncture)

expectancy related activation: placebo + nocebo effect

pain threshold: usually constant

pain tolerance: variable (past exposure, motivations, drugs...)

pain is felt somewhere that is not site of nociception origin

organs borrow nociceptors

direct injury to CNS or PNS nociceptive neurons

CNS: brain or SC trauma -> think strokes, hemiagnosia = hyperalgesia/allodynia of one half of body

PNS: peripheral nerve trauma, phantom limb pain, possibly due to scar tissue + absence of inhibitory signals

heat production + conservation via activation of HPT axis:

T4 -> increase metabolism + adrenal glands -> increase cellular work (shivering) + vasoconstriction

heat loss via shut down of HPT axis:

decreased T4 -> decrease metabolism + vasodilation + sweat

temporary reset to higher temp in response to pathogens