Touch and Feel lecture exam

What occurs during the Reception (Stimulation) step of sensation?

Receptors detect a stimulus and generate a receptor potential. Structures involved: sensory receptors (free or encapsulated nerve endings); located throughout the body.

What is a receptor potential?

A graded electrical response generated in a sensory receptor by a stimulus; it may lead to an action potential if threshold is reached.

What is adaptation in sensory receptors?

Decrease in receptor sensitivity over time during constant stimulation. Fast-adapting receptors stop responding quickly; slow-adapting continue firing.

What occurs during sensory transduction?

Conversion of a stimulus (e.g., light, pressure) into an electrical signal (graded potential).

What occurs during transmission in sensation?

Action potentials are propagated along sensory neurons to the CNS.

What occurs during perception in sensation?

The brain interprets sensory signals, leading to conscious awareness of the stimulus. Structures: cerebral cortex (varies by sense).

Compare encapsulated vs. free nerve endings.

Encapsulated: dendrites wrapped in connective tissue (e.g., Meissner’s corpuscles); detect pressure/touch. Free: bare dendrites (e.g., nociceptors); detect pain, temp.

Compare rapidly and slowly adapting receptors.

Rapid: respond quickly, stop firing with constant stimulus (e.g., Meissner’s). Slow: continue firing (e.g., Merkel cells, Ruffini endings).

What are exteroceptors?

Receptors that detect external stimuli (touch, pressure, temperature, vision); found in skin and sense organs.

What are interoceptors?

Detect internal stimuli (e.g., blood pressure, chemical changes); found in blood vessels, organs.

What do mechanoreceptors detect?

Mechanical stimuli like touch, pressure, vibration, stretch.

What do thermoreceptors detect?

Temperature changes.

What do chemoreceptors detect?

Chemical stimuli (e.g., taste, smell, CO₂ levels in blood).

What do photoreceptors detect?

Light (e.g., rods and cones in retina).

What do nociceptors detect?

Pain from tissue damage or extreme stimuli.

What are Merkel cell fibers (tactile discs)? Include location, function, and adaptation speed.

Located in the epidermis (especially fingertips); detect light touch and shape/texture; slowly adapting.

What are Tactile (Meissner’s) corpuscles?

Found in dermal papillae (fingertips, lips); detect fine touch and vibration; rapidly adapting.

What are Ruffini endings?

Located in dermis and joints; detect stretch and sustained pressure; slowly adapting.

What are Lamellated (Pacinian) corpuscles?

Found deep in dermis and hypodermis; detect deep pressure and high-frequency vibration; rapidly adapting.

What are Hair follicle receptors (Root hair plexus)?

Wrap around hair follicles; detect hair movement; rapidly adapting.

What are proprioceptors and what do they detect?

Found in muscles, tendons, joints; detect body position, movement, and stretch; include muscle spindles and Golgi tendon organs.

What are the two types of thermoreceptors, and where are they located?

• Cold receptors: located in superficial dermis; detect 10–40°C.

• Warm receptors: located in deeper dermis; detect 32–48°C.

Why can some temperatures cause pain?

Extreme temperatures activate nociceptors, leading to the sensation of pain.

What are muscle spindles and their function?

Located in skeletal muscles; detect muscle stretch; involved in stretch reflex to prevent overstretching.

What are Golgi tendon organs and their function?

Located in tendons; detect tension; inhibit excessive contraction to prevent tendon injury.

What is referred pain?

Pain perceived in an area different from its origin due to shared sensory pathways.

What is a dermatome, and how is it related to referred pain?

A dermatome is an area of skin innervated by a single spinal nerve. Referred pain often follows these patterns.

How is phantom limb pain related to the brain?

Caused by activity in the primary somatosensory cortex, which still receives input from the missing limb's pathway.

Differentiate between acute and chronic pain.

• Acute: sudden, sharp, short-term pain.

• Chronic: persistent, long-lasting pain often beyond healing.

What is pain adaptation, and how do receptor and central adaptation differ?

• Receptor adaptation: reduced response by nociceptors (rare).

• Central adaptation: CNS adjusts perception of pain.

• Nociceptors do not adapt significantly.

What are the effects of endorphins and enkephalins?

Natural opioid neurotransmitters; bind to opioid receptors in the CNS to inhibit pain signals and create analgesia.

What is a receptive field of a sensory receptor?

The area monitored by a single receptor. Smaller fields = more precise localization (e.g., fingertips).

Differentiate papillae, taste buds, and gustatory cells.

• Papillae: Surface projections on tongue.

• Taste buds: Sensory structures on papillae.

• Gustatory cells: Taste receptor cells inside taste buds.

What are the functions of basal cells, supporting cells, and gustatory cells?

• Basal cells: Regenerate gustatory cells.

• Supporting cells: Maintain structure.

• Gustatory cells: Detect tastants and send signals.

Define tastant.

A chemical that stimulates gustatory receptors, producing taste sensation.

Describe regeneration of gustatory cells and the effect of aging.

Lifespan ≈ 10–14 days; regenerated by basal cells. Regeneration slows with age → reduced taste.

What cranial nerves are involved in taste?

• Facial (VII): Anterior 2/3 of tongue.

• Glossopharyngeal (IX): Posterior 1/3 of tongue.

• Vagus (X): Throat/epiglottis.

Trace the gustatory pathway from tastant to perception.

Tastant → Gustatory cell → Cranial nerve → Medulla → Thalamus → Gustatory cortex (insula).

What is the role of saliva in taste?

Dissolves tastants so they can bind to gustatory receptors.

What are the 5 primary tastes and their stimuli?

• Sweet (sugars)

• Salty (Na⁺)

• Sour (H⁺)

• Bitter (alkaloids)

• Umami (glutamate)

What are the roles of basal cells, supporting cells, and olfactory neurons?

• Basal cells: Replace olfactory neurons.

• Supporting cells: Structure and detox.

• Olfactory neurons: Detect odorants.

Define odorant.

A chemical that binds to olfactory receptors, producing smell.

Describe olfactory neuron regeneration and aging effects.

• Lifespan ≈ 30–60 days.

• Regenerated by basal cells.

• Declines with age → hyposmia (reduced smell) or anosmia (loss of smell).

Which cranial nerve is responsible for smell?

Olfactory nerve (I)

Trace the olfactory pathway from odorant to perception.

Odorant → Olfactory receptor → Olfactory nerve → Olfactory bulb → Olfactory tract → Cerebral cortex (temporal lobe, limbic system).

What is the role of mucus in smell detection?

Traps and dissolves odorants so they can bind to receptors.

How does smell affect taste?

Smell contributes ~80% of flavor perception; loss of smell greatly reduces taste.

What are the three major parts of the ear?

• Outer ear: Pinna, lobule, external auditory canal

• Middle ear: Tympanic membrane, auditory ossicles (malleus, incus, stapes), auditory tube

• Inner ear: Cochlea, vestibule, semicircular canals, spiral organ

Which ear structures are involved in audition?

Tympanic membrane, ossicles, cochlea, spiral organ (Organ of Corti)

Which ear structures are involved in equilibrium?

Vestibule, semicircular canals, hair cells (maculae and cristae)

Compare endolymph and perilymph in the inner ear.

• Endolymph: Found in membranous labyrinth; high K⁺, important for depolarization.

• Perilymph: Found between bony and membranous labyrinths; similar to extracellular fluid.

What cranial nerve is responsible for hearing and balance?

Vestibulocochlear nerve (VIII)

How do amplitude and frequency affect sound?

• Amplitude: Loudness

• Frequency: Pitch

Trace the path of a sound wave to perception.

Sound → External auditory canal → Tympanic membrane → Ossicles → Oval window → Cochlea (perilymph pressure waves) → Basilar membrane → Hair cells → Vestibulocochlear nerve → Medulla → Midbrain → Thalamus → Auditory cortex (temporal lobe)

What is the role of the Organ of Corti?

Located in cochlea; contains hair cells that transduce vibrations into neural signals.

What are the 3 sources of input for balance?

• Vision

• Proprioception

• Vestibular system (inner ear)

Differentiate between equilibrium and vestibular sensation.

• Equilibrium: Overall sense of balance.

• Vestibular sensation: Specific input from inner ear to detect movement.

What’s the difference between static and dynamic equilibrium?

• Static: Detects head position (utricle & saccule in vestibule).

• Dynamic: Detects motion (semicircular canals).

Where are hair cells for static and dynamic equilibrium located?

• Static: Utricle and saccule (maculae)

• Dynamic: Semicircular ducts (crista ampullaris)

What are otolithic membranes and otoliths?

• Otolithic membrane: Gel layer covering maculae.

• Otoliths: Calcium crystals adding weight; shift with gravity to stimulate hair cells.

Describe the physiology of static equilibrium.

Head tilts → otoliths move → otolithic membrane bends hair cells → sends signal to brain about position.

Describe the physiology of dynamic equilibrium (linear and rotational).Describe the physiology of dynamic equilibrium (linear and rotational).

• Linear: Detected in utricle/saccule during straight movement.

• Rotational: Detected by semicircular canals; fluid movement bends hair cells in ampullae.

Compare hair cells in hearing vs. equilibrium.

• Both use stereocilia.

• Hearing: located in cochlea, detect sound waves.

• Equilibrium: in vestibule & semicircular canals, detect motion.

What are the 3 tunics (layers) of the eye and their components?

• Fibrous layer: Sclera, cornea

• Vascular layer: Choroid, ciliary body, iris

• Neural layer: Retina (photoreceptors, macula lutea, fovea centralis, optic disc)

What is the function of the lens, suspensory ligaments, and pupil?

• Lens: Focuses light

• Suspensory ligaments: Hold lens in place

• Pupil: Controls amount of light entering

Differentiate the anterior cavity vs. posterior cavity and chambers.

• Anterior cavity (aqueous humor): Between cornea and lens

  • Anterior chamber (cornea to iris)

  • Posterior chamber (iris to lens)

• Posterior cavity (vitreous humor): Behind the lens

Front: What is the function of:

• Iris

• Pupil

• Optic disc

• Fovea centralis

• Iris: Eye color, controls pupil size

• Pupil: Regulates light entry

• Optic disc: Blind spot (no photoreceptors)

• Fovea centralis: Point of sharpest vision

What is the visible light spectrum?

Part of the electromagnetic spectrum visible to humans (~400–700 nm)

Define a photon and its role in vision.

A quantum of light; stimulates photoreceptors.

What is refraction, and why is the eye convex?

Refraction = bending of light. A convex shape focuses light on the retina.

What is the focal point, and which eye structures refract light?

• Focal point: Where light converges on retina

• Structures: Cornea (major), aqueous humor, lens, vitreous humor

Differentiate emmetropia and accommodation.

• Emmetropia: Normal distant vision

• Accommodation: Lens adjusts to focus on near objects

How do accommodation, pupillary constriction, and convergence work together for near vision?

• Lens thickens

• Pupils constrict

• Eyes converge inward

What is the near point of accommodation, and how does it change with age?

Closest point that can be focused clearly; increases with age due to loss of lens elasticity.

Define and compare refraction errors:

• Presbyopia

• Hyperopia

• Myopia

• Astigmatism

• Presbyopia: Aging lens, poor near vision

• Hyperopia: Farsightedness (short eye)

• Myopia: Nearsightedness (long eye)

• Astigmatism: Irregular cornea curvature

Name the 5 types of retinal cells and their functions.

• Photoreceptors (rods/cones): Detect light

• Bipolar cells: Transmit signals

• Ganglion cells: Form optic nerve

• Horizontal cells: Integrate input

• Amacrine cells: Modify bipolar-ganglion communication

Compare rods and cones.

• Rods: Dim light, no color, periphery

• Cones: Bright light, color, central vision

What is the difference between rhodopsin and iodopsin?

• Rhodopsin: Rod pigment

• Iodopsin: Cone pigment (RGB-sensitive)

What are the three cone types and what wavelengths do they detect?

Red, green, and blue cones detect long, medium, and short wavelengths respectively.

Describe light vs. dark adaptation.

• Light: Rhodopsin breaks down → temporary glare

• Dark: Rhodopsin regenerates → improved night vision

Trace the pathway of light to perception.

Light → Cornea → Aqueous humor → Lens → Vitreous humor → Retina → Photoreceptors → Bipolar cells → Ganglion cells → Optic nerve → Optic chiasm → Thalamus → Visual cortex (occipital lobe)

Compare monocular, binocular, and stereoscopic vision.

• Monocular: One eye

• Binocular: Both eyes

• Stereoscopic: Depth perception from overlapping fields

What is the consensual pupillary response?

When one pupil constricts in light, the other also constricts due to shared pathways.

How does the brain process images?

Visual cortex reconstructs image, integrates input from both eyes for clarity, depth, and motion.

Compare the somatic and autonomic nervous systems.

• Somatic: Skeletal muscles, voluntary

• Autonomic: Smooth/cardiac muscle & glands, involuntary

Differentiate preganglionic and postganglionic neurons.

• Preganglionic: Cell body in CNS, axon goes to ganglion

• Postganglionic: Cell body in ganglion, axon goes to effector

Compare the sympathetic and parasympathetic divisions.

• Sympathetic: "Fight or flight", thoracolumbar origin

• Parasympathetic: "Rest and digest", craniosacral origin

What are the main ganglia of each ANS division?

• Sympathetic: Sympathetic chain, collateral, adrenal medulla

• Parasympathetic: Terminal ganglia near/within organs

Describe the fibers and neurotransmitters used by each division.

• Sympathetic: Short pre-, long postganglionic; NE & ACh

• Parasympathetic: Long pre-, short postganglionic; ACh

Identify adrenergic receptors and their effects.

• Alpha-1: Vasoconstriction

• Alpha-2: Inhibits NE release

• Beta-1: ↑ Heart rate

• Beta-2: Bronchodilation, vasodilation

Identify cholinergic receptors and their effects.

• Nicotinic: Excitatory; at ganglia and NMJ

• Muscarinic: Excitatory or inhibitory; at effectors

Which cranial nerve provides most parasympathetic innervation?

Vagus nerve (X)

• How do the sympathetic and parasympathetic systems maintain homeostasis?

Through dual innervation — opposing actions balance body function (e.g., heart rate, digestion).

What is autonomic tone?

Baseline level of activity from ANS that adjusts up or down as needed.

Which functions are controlled only by the sympathetic division?

Sweat glands, arrector pili, blood vessels to skin, adrenal medulla

What brain region integrates and controls the ANS?

Hypothalamus

eyes (fight or flight)

Pupils dilate (mydriasis) to improve vision and light intake.

Salivary Glands

Saliva production decreases → dry mouth.

Heart

Heart rate and force of contraction increase (↑ cardiac output).

Respiratory System

Breathing rate increases (↑ respiratory rate).