Physio Exam 2 Sensory Physiology

Photoreceptors

Detect light via rods and cones in retina

Chemoreceptors

Detect chemical changes in environment such as:

• Olfactory receptors

• Taste receptors

• Osmoreceptors (found in wall of large blood vessels such as aorta)

• Carotid body O2 receptors

Nociceptors

Detect extremes of temperature and pain (ex: substance P and glutamate)

Baroreceptors

Blood receptor that detects changes in blood pressure

1. Type A (fastest)

2. Type B

3. Type C (C is slowest and for pain)

pain fiber types

1. Sensory receptors in peripheral organs like skin (light touch, vibration, pain) activated by environmental stimuli (epithelilal cells, primary afferent neurons etc)

2. After stimulation of sensory receptors in peripheral → activation of 1st group of afferent neurons → neurons travel from peripheral to either dorsal horn of spinal cord/brain stem or in spinal cord ganglia for synapse w/ 2nd group fo neurons (primary afferent neurons in relay nuclei)

3. 2nd group of axon neurons cross the midline and travels to contralateral thalamus (ex: from left hand to right thalamus)

4. Then synapse with 3rd group of neurons in contralateral thalamus relay nuclei

5. 3rd group goes to cerebral cortex and synapse with 4th group of (motor) neurons → motor neurons take rxn to peripheral organ

General sensory pathway

1. Sensory receptors in ____like skin (light touch, vibration, pain) activated by environmental stimuli (epithelilal/auditory hair cells, primary afferent neurons etc)

2. After stimulation of sensory receptors in peripheral → activation of 1st group of ___neurons → neurons travel from peripheral to either___ of spinal cord/brain stem or in ___ ganglia for synapse w/ 2nd group for neurons (primary afferent neurons in relay nuclei)

3. 2nd group of axon neurons cross the midline and travels to ___ (ex: from left hand to right thalamus)

4. Then synapse with 3rd group of neurons in ___

5. 3rd group goes to ____ and synapse with 4th group of ____ neurons → ___neurons take rxn to peripheral organ

processes fine touch pressure, two point discrimination, and vibration

• course: primary afferent neurons have cell bodies in dorsal root and their axons ascend ipsilaterally to the nucleus gracillis and nucleus cuneatus of the medulla

  • 2nd order neurons cross the midline from the medulla and go to the contralateral thalamus and synapse w/ 3rd order neurons

  • 3rd order neurons ascend to the somatosensory cortex and synapse w/ 4th order neurons

Dorsal column sensory system

processes fine ___

• course: primary afferent neurons have cell bodies in ___ and their axons ascend ___to the nucleus ____ and nucleus ____ of the ___

  • 2nd order neurons cross the midline from the ____ and go to the ____and synapse w/ 3rd order neurons

  • 3rd order neurons ascend to the ____ and synapse w/ 4th order neurons

processes temp, pain, and light touch

• course: made of a group of fibers that enter the spinal cord and terminate in the dorsal horn

  • 2nd order neurons cross the midline and go to the anterolateral quadrant of the spinal cord and second to the contralateral thalamus and synapse w/ 3rd order neurons

  • 3rd order neurons ascend to the somatosensory cortex and synapse w/ 4th order neurons

Anterolateral sensory system

processes ___

• course: made of a group of fibers that enter the ___ and terminate in the ___

  • 2nd order neurons cross the ____ and go to the ____ of the spinal cord and second to the ____ and synapse w/ 3rd order neurons

  • 3rd order neurons ascend to the ____ and synapse w/ 4th order neurons

Problems with left side of brain due to contralateral thalmus

Head trauma occurred on right side due to car accident. What sensory disorder can occur?

They have pain in retrosternal area, radiation to left shoulder, left arm, left forearm, and last two fingers (fourth and fifth) and submandibular pain

Referred pain for myocardial infarction thats a result of hypoxia (leads to cell death in heart)

Can cause epigastric line pain especially on right/right backside (pain could also be from right kidney problems because pain is similar; to find difference you have to look at amount of urine, color of urine, etc.)

Referred pain for liver/gallbladder

Anterior: Sweet

Lateral: Sour

Anterolateral: Salty

Posterior: Bitter

Taste bud regions

Salty: NaCl

• ion channels lets Na enter taste cells → depolarization → voltage-regulated Ca gates open → cells flood w/ ions → neurotransmitter release

Sour: Hydrogen acidic comporund

• has 3 different receptor proteins working

• 1st one is what allows H to flow directly into the cell

Bitter: G-protein coupled receptors GPCR’s in taste cell walls

• releases the gustducin protein

Sweet: GCPR’s

Compounds needed for different tastes

Bell palsy

Paralyzed facial nerve & has 5 branches (viral infection can affect chorda tympani branch of facial nerve and affect taste

Ageusia

You may lose your sense of taste if the facial nerve is damaged.

Hypogeusia

Decreased taste sensitivity

Hypergeusia

Increased taste sensitivity

Sore tongue

caused by some form of trauma, like biting your tongue or eating piping-hot or highly acidic food or drink

• causes include diabetes, anemia, vitamin deficiency, certain skin disorders, bruxism (grinding teeth), improperly fitted teeth

Glossodynia

A condition characterized by a burning sensation on the tongue

Benign migratory glossitis (geographic tongue)

irregular/inflamed patches on the tongue surface w/ white borders → swollen, red, and sore tongue

• unknown cause

Tumor on tongue

Cause inflammation of tongue and can be benign or malignant

1. After stimulation of chemoreceptors in nasal cavity leads to stimulation of first group of neurons (mitral cells) which take the information about sensory or odor to olfactory bulb

2. Olfactory bulb neurons depolarize by activation of sodium channels then the first group of neurons have synapse with second group of neurons and travel to the olfactory tract and from there they travel to center of olfactory (location of olfactory center is at base of olfactory tract)

Chemoreceptor stimulation

1. After stimulation of ___ in nasal cavity leads to stimulation of first group of neurons ___ which take the information about sensory or odor to olfactory ___

2. Olfactory bulb neurons ____ by activation of ____channels then the first group of neurons have synapse with second group of neurons and travel to the olfactory ____ and from there they travel to center of ____ (location of olfactory center is at ____of olfactory _____)

molecules bind to olfactory receptors in the nasal cavity, base of receptors is connected to the 1st group of neurons → takes info to bulb → bulb has synapse w/ 2nd group of neurons (mitral cells) → mitral cells travel to olfactory tract and goes to the cortex

Olfactory system:

molecules bind to olfactory receptors in the ___, ___ of receptors is connected to the 1st group of neurons → takes info to ___→ ___has synapse w/ 2nd group of neurons (____) →___ travel to olfactory ___and goes to the ___

Anosmia

Lack of olfaction, or a loss of the sense of smell

• Caused by: neurological/psychologic issues, damage to the olfactory tract (such as head trauma), psychological or damage to sensory receptor

Phantosmia

Phenomenon of smelling odors that aren't really present

• psychologic

Dysosmia

When things smell differently than they should

• pregnancy bc of hormonal changes

Sclera, choroid and retina

Layers of eye

Sclera

tough white fibrous connective tissue that protection the eye from external trauma and maintains/supports shape of it

• continues ventrally w/ the transparent cornea

  • behind the cornea is the ant. chamber, pupil, and lens

Choroid

middle thin vascular layer of eye between the retina and sclera

• gives oxygen and nourishment to the outer layers of the retina

• nonreflective pigments for lightshieldings and to prevent light scattering

Canal of Schlemm

Foramen opening that the intraocular fluid passes through and releases into venous system

Glaucoma

Caused by obstruction of Canal of Schlemm (could be genetic, tumor, trauma, infection, etc.) as a result of accumulation of intraoccular fluid which ultimately closes the canal

• untreated w/o surgery→ blindness bc of optic n. compression

Layer 1: Pigment cells

• absorb stray light and prevent scatter

Layer 2: Photoreceptor (rods and cones)

Layer 3: Bipolar cells

• photoreceptors synapse on bipolar cells

• bipollar cells synapse on ganglion cells

Layer 4: Horizontal cells

Layer 5: Amacrine cells for circuits with the bipolar cells

Layer 6: Ganglion cells and axons from ganglion cells form optic nerve

• overall outpull cells of retina

Layers of Retina

Area 17, 18 and 19 (primary visual area) in occipital lobe

Where does visual stimuli finally end up in brain?

Can destroy retina, optic nerve and lens

Excess fluid in anterior and posterior chamber

Optic disc

"Blind spot" because there are no rods or cones (lacks photoreceptor) → not senstitive to light signals

• where the optic nerve leaves the eye and takes impulses to the brain

• Rods are very sensitive to light and dont see color

  • why we only see grey shades in a darkened room

• Cones detect wavelength of light which detects colors

  • lack of cones sensitive to red, blue, and green → deficiences in color vision/color blindess

Rods vs. Cones

1. light goes through ext. structures

2. light focuses on pigment cells (1st layer)

3. light passes from pigment cells to rods

4. rods absorbs signals → rhodopsin act. → conversion of 11cis retinal to all-trans retinal (PHOTOISOMERIZATION) → act. of metorhodpsin II → act. of g protein → act. of phosphodiesterase → decrease in intracellular energy (cGMP) → Na+ channels close → rod hyperpolarizatioin (b/c of inhibition of inhibitory neurotransmitters → Na+ cant get in) → no inhibitory neurotransmitters → rod signals pass through remaining layers → optic n. recieves signals and sends to CNS

photoreception of rods:

1. light goes through ___

2. light focuses on ___

3. light passes from ____ to ____

4. ___ absorbs signals → ___act. → conversion of 11cis retinal to all-trans retinal (____) → act. of ___ → act. of ____ → act. of ____→ decrease in ____ → ___ close → rod ___(b/c of ____of inhibitory neurotransmitters → Na+ cant get in) → no ____ → rod signals pass through ____ → ____. recieves signals and sends to ____

light signals from the nasal field focus on the temporal portion of that retina/eye → travels to optic chiasm → travels to ipsilateral optic tract/n. → synapse w/ next group of neurons at hte lateral geniculate nucleus of the thalamus → group of neurons travel to the occipital lobe of brain (primary visual area 17, 18 and 19) via the geniculocarine tract

Optic pathway in nasal field

light signals from temporal field focus on the nasal portion of that retina/eye → travels to optic chiasm and cross it → travels to the contralateral optic tract/n. → synapse w/ next group of neurons at hte lateral geniculate nucleus of the thalamus → group of neurons travel to the occipital lobe of brain (primary visual area 17, 18 and 19) via the geniculocarine tract

Optic pathway in temporal field

complete blindness of left eye (affects both fields)

left optic nerve cut causes

blindness in left nasal field

lateral left part of optic nerve cut causes

blindness in left and right temporal fields

optic chiasm is cut causes

blindness of left nasal and right temporal fields

left optic tract is cut causes

left geniculo-calcarine tract cut causes

partial (50%) blindness of left nasal and right temporal fields affects

• because it receives signals from many diff. fibers/neurons

Color blindness/color vision deficiency

inability to perceive differences between some or all colors that other ppl can normally distringuish bc of cones damage

• mostly genetic

• can happen bc of eye/nerve/brain damage or chemical exposure

Night blindness (nyctalopia)

Deficiency of Vitamin A which is necessary for the regeneration of rhodopsin

• can exist from birth

• can be result of injury or malnutrition

• most common cause: retinitis pigmentosa - rod cells gradually lose ability to respond to light

Visual agnosia

Inability of brain to make sense/use of normal stimuli. (cannot recognize faces or objects)

Emmetropia

Normal vision. Light focuses on the retina

Hyperopia

Farsighted.

• Light focuses behind the retina

• Corrected with convex lens

Myopia

Nearsighted.

• Light focuses in front of the retina

• corrected w/ biconcave lens

Astigmatism

Curvature of the lens is not uniform

• corrected w/ cylindric lens

• can be result of age

External/outer ear

composed of auricle, ear canal/auditory tube, tympanic membrane/ear drum surface

Middle ear

Found behind tympanic membrane and has three bones (ossicles) called malleus/hammer (connected to tympanic membrane), incus/anvil and stapes/stirrup (connected to oval window)

• also has the easutachian tube opening

• has connection to the meningeal layer of brain

• air-filled

Found behind the oval window w/ 3 parts:

• Cochlea (for hearing)

• Vestibular system w/ 3 semicircular canals (maintains body equilibrium)

• membraneous labryinth series of ducts

  • perilymph outside of the ducts

  • endolymph inside of the ducts

Inner ear

Organ of Corti

hearing receptor organ found on the basilar membrane in the scala media and vibrates bc of sound waves causing the bending of cillia, depolarization of hair cells and firing of cochlear nerves (CN VIII)

Scala media

Contains hair cells (cilia). At the base of these is a membrane called basilar membrane and a sensory cochlear afferent fiber which detects any change in hair cells as a signal and takes it to CNS. On top of hair cells is the tectorial membrane. Contains endolymph

Scala tympani and scala vestibule

Parts of the organ of Corti that contain perilymph

1. Sound waves travel through the air and are converted into pressure waves into fluid pressure(perilymph and endolymph)

2. Sound waves pushes back tympanic membrane → vibration or movement of ossicles

3. stapes (connected to the oval window) pushes back the oval window → circulation of perilymph in scala vestibule then scala tympani (connected to the round window)

4. perilymph reaches the oval window → vibration of basilar membrane → vibration of cilia hair cells (hair cells bend) on top of membrane against tectorial membrane → depolarization where K+ stays inside the cells → Ca2+ channels open → increase in intracellular Ca2+ -.

5. release of stimulatory glutamate neurotransmitter into synaptic cleft and stimulation of sensory afferent fibers (post-synaptic)

6. Stimulation of afferent fiber/cochlear nerve and the nerve takes info to the CNS

Auditory transduction in organ of Corti:

1. Sound waves travel through the air and are converted into ___ into fluid_____ (perilymph and endolymph)

2. Sound waves pushes back ____ → vibration or movement of ____

3. ____(connected to the oval window) pushes back the ____ → circulation of perilymph in ____ then _____ (connected to the ____)

4. perilymph reaches the ____ → vibration of ____ → vibration of cilia hair cells (hair cells ____) on top of membrane against ____ membrane → depolarization where K+ stays ____ → ____ channels open → increase in intracellular ____ -.

5. release of stimulatory ____neurotransmitter into synaptic cleft and _____of sensory afferent fibers (post-synaptic)

6. Stimulation of afferent fiber/cochlear nerve and the nerve takes info to the CNS

Prevents potassium conductance causing hyperpolarization

Bending of hair cells (cilia) in one direction inside the cochlea

Causes depolarization

Bending of hair cells in different directions inside the cochlea

Temporal lobe, superior temporal gyrus, Area 41 and 42 for T1 and T2

Main center for auditory

a4 hair cells bend and the first group of neurons is stimulated, sound waves reach the CNS

1. hair cells info of the organ of corti are transmitted to the afferent cochlear nerves

2. 1st group of neurons travel to and have synapse at the basal ganglia

3. 2nd group of neurons travel to and have synapse at V and D cochlear nuclei of medulla oblongata → some axons cross contralaterlly to the lateral lemnisuc (primary auditory tract), others remain ipsilateral

4. passes through the pons and have synapse at inf. colliculus of the midbrain

5. then travels to and has synapse at the medial geniculate of the thalamus

6. finally travel to the primary auditory area in the superior temporal gyrus (area 41 and 42)

Auditory pathways

a4 hair cells bend and the first group of neurons is stimulated, sound waves reach the CNS

1. hair cells info of the organ of corti are transmitted to the ____

2. 1st group of neurons travel to and have synapse at the ____

3. 2nd group of neurons travel to and have synapse at ___ of the ____ → some axons cross ____ to the ____ (primary auditory ___), others remain ipsilateral

4. passes through the ____and have synapse at ____ of the ___

5. then travels to and has synapse at the ____ of the ____

6. finally travel to the primary auditory area in the ____ (area ___and ___)

Big hairs are kinocilium, smaller are stereocilia and are covred by jelly-like substance called cupula

Hair cells of semicircular canals

Angular rotation (turning right and left)

• i.e when you drive, you shift left/right, and your head turns as a result

What do semicircular canals detect?

Linear acceleration (walking, accelerating in a car, etc.)

• i.e when you fall down, the statoconia also falls back → sterocillia moves towards kinocillium (depol of hair cells) → potassium stays inside hair cells and calcium enters → stimulatory neurotransmiterr released → stimulation of 1st group of neurons for vestibular n. → synapse w/ next group at vestibular ganglion

• when vestibular n. takes info to CNS → motor system is activated and eq is achieved

  • statoconia goes back to position but sterocillia move away from kinocillium aka hyperpolarization

What do the utricles and saccule detect?

1. Because of the changing of position that loses the equilibrium, statoconia which covers jelly substance falls back because it is heavier than the hair cells

2. This movement stimulates the hair cells and sensory nerve connected to the base of hair cell (sensory nerve is same as vestibular nerve)

3. Afferent fiber of vestibular nerve takes info to CNS and then stimulates different centers in CNS such a motor, upper limb and lower limb and efferent fiber

4. Takes signals again to the vestibular system.

5. Statoconia comes back to resting position and meanwhile, the body corrects the position by using the upper limbs and lower limbs.

What happens when a person is walking and suddenly falls down?

1. Person turns head to right side

2. The endolymph goes to the opposite direction (left side)

3. Pushes the cupula to the opposite side (left side)

• stimulation of hair cells → depolarization of hair cells → releasing of stimulatory neurotransmitter → stimulation of sensory nerve (vestibular nerve) → Vestibular nerve takes info to CNS

4 head stops rotation → endolymph moves to the same direction as head movement

• cupula goes to same direction until movementof endolymph stops and cupula goes back to normal position

What happens if a person turns their head to the right side?

5

How many pathways occur for the vestibular system?

Vestibulo-spinal pathway

After stimulation of hair cells and vestibular nerve stimulation, the path through vestibular ganglion they have synapse to next group of neurons and they travel to vestibular nuclei. After synapse they come back to spinal cord

Function of vestibulo-spinal pathway

Facilitates extensor msucles of upper and lower limb while INHIBITING flexor muscles

Flocculonodular pathway

Some fibers travel to the vestibular nuclei and after synapse, they travel/reach the lower lobe of cerebellum (lobe is called flocculonodular lobe)

Function of flocculonodular pathway

Maintain general movement equilibrium

Medial-longitudinal pathway

Some fibers travel to vestibular ganglion and synapse, then travel to midbrain and inside the midbrain we have the nuclei of some cranial nerves (CN 3, 4, 6).

Function of medial-longitudinal pathway

Controls the movement of the eyes

Rubro-spinal pathway

The signals travel to the vestibular nucleus (ganglion) then to vestibular nuclei in brainstem then reach red nucleus in midbrain then after synapse it comes back to spinal cord.

Function of Rubro-spinal pathway

Facilitates flexor muscles and INHIBITS extensor muscle

Reticulo-spinal pathway

Comes to vestibular nuclei and after synapse then reaches reticular nucleus in pons. After synapse inside reticular nucleus it comes back to spinal cord.

Function of Reticulo-spinal pathway

Function: This tract reaches motor center of spinal cord (ventral horn) and it activates alpha and gamma motor neurons

Alpha vs gamma motor neurons

Alpha innervates the skeletal muscle fibers and causes contractions while Gamma innervates the skeletal muscle fibers (sensory branch)

Nystagmus

Abnormal movement of eye that causes eyes to rapidly snap back and move again when the limit of eye movements is reached during rotation of the head that causes the eyes to move slowly in the opposite direction to maintain visual fixation

• can be pathologic congenital problem,

• can be neurological (damaged CN III, IV, and VI)

• can be physiologic (ballerina after spinning)

1. HP or hypotension

2. Hypoglycemia

3. Hypercholesterolemia

4. Damage to vestibular system of inner ear (maintains equilibrium)

5. Any damage or trauma to vestibular pathway such as cerebellum

Vertigo can be caused by

sensory systems

made of specialized epithelial cells/neurons that transduce envionmentla signas into neural signlas

what are environmental signals that can be detected

mechanical force, light, sounds, chemicals, and temperature

respond to mechanical stimulus

• pacinian corpuscles

• joint receptors

• stretch receptors in muscle

• hair cells in auditory and vestibular system

• baroreceptors in carotid sinus

mechanoreceptors

• mechanoreceptors

• photoreceptors

• chemoreceptors

• extremes of temperature and pain

what are the types of sensory transducers

A-alpha fiber

large alpha-motorneurons

• fastest CV

A-beta fiber

carry touch and pressure

• medium CV

A-gamma fiber

gamma-motoneurons to muscle spindles (intrafusal fibers): muscle tone and reflex

• medium CV

A-delta fiber

carries touch, pressure, temperature, and pain

• medium CV

B fiber

preganglioninc autonomic fibers

• medium CV

C fibers

postganglioninc autonomic fibers that carry slow pain

• slowest CV

receptive field

area of the body that changes the firing rate of a sensory neuron when stimulated

• if firing rate is increased → excitatory receptive field

• if firing rate is decreased → inhibitory receptive field

steps in sensory transduction

1. stimulus arrives at sensory receptor

• i.e photon of light on retina or molecule of NaCl on tongue

2. sensory receptor ion channels open → flow of inward current → receptor depolarization

3. receptor/generator potential - change in membrane potential made by the stimulus

adaptation of sensory receptors

1. slowly adapting/tonic receptors (muscle spindles, pressure, slow pain) → respond reptitively to a prolonged stimulus

2. rapid adapting/phasic receptors (pacinian corpucle, light touch) → decline in action potential frequency w/ time in response to a constant stimulus

somatosensory system

proccesses info abt touch, pain and temp

• pathways: dorsal column and anterolateral

• types: mechanoreceptors (for touch), thermoreceptors and nociceptors

thalamic … contralateral

destruction of the ___ nuclei results in loss of sensation on the ___ of the body

a delta pain fibers

rapid onset/offset → fast localized pain

c pain fibers

poorly localized slow pain like aching, burning, throbbing

referred pain

pain of visceral origin is referred to sites on the skin and follows the dermatome rule

• sites are innervated by nerves that come from the same segment of the spinal cord

• origin of nerves from the same area and travel to different organs

two-point threshold

if each point touches the receptive filds of different sensory neurons, if both caliper points touch field of one sensory neuron, only one point will be touch

• each tip touches at a time bc far apart → 2 different nerves

• each tip tocuhes at a time bc their close together → one axon terminal