Peripheral Nervous System and Related Concepts

These flashcards cover key terms and concepts related to the Peripheral Nervous System and sensory pathways, aiding in understanding and memorization for the exam.

Peripheral Nervous System (PNS)

All neural structures outside the brain and spinal cord.

Central Nervous System (CNS)

Consists of the brain and spinal cord.

Mechanoreceptors

Receptors that respond to mechanical pressure or distortion.

Thermoreceptors

Receptors that detect changes in temperature.

Photoreceptors

Receptors that respond to light.

Chemoreceptors

Receptors that respond to chemical stimuli.

Nocioreceptors

Receptors that respond to potentially damaging stimuli, causing pain.

Exteroreceptors

Receptors that respond to stimuli from outside the body.

Interoreceptors

Receptors that respond to stimuli from within the body.

Proprioreceptors

Receptors that provide information about body position and movement.

Somatosensory System

Receives input from receptors and processes sensory information.

Endoneurium

Delicate connective tissue surrounding individual nerve fibers.

Fascicle

A group of nerve fibers bundled together.

Perineurium

Connective tissue wrapping surrounding a fascicle.

Epineurium

Fibrous sheath surrounding the entire nerve.

Sensory Nerves

Nerves that carry sensory information to the CNS.

Motor Nerves

Nerves that carry motor commands from the CNS to muscles.

Mixed Nerves

Nerves that contain both sensory and motor fibers.

Cranial Nerves

Twelve pairs of nerves that arise directly from the brain.

Spinal Nerves

Nerves that emerge from the spinal cord; there are 31 pairs.

Plexus

A network of intersecting nerves.

Dermatome

An area of skin innervated by the cutaneous branches of a single spinal nerve.

Motor Endings

Structures that innervate skeletal and visceral muscles.

Reflex Arc

A neural pathway that mediates a reflex action.

Integration Center

The central processing area in a reflex arc where sensory input is processed.

Cranial Nerve I (Olfactory)

Responsible for the sense of smell.

Cranial Nerve II (Optic)

Responsible for vision.

Cranial Nerve III (Oculomotor)

Controls most extrinsic eye muscles, eyelid movement, and pupil constriction.

Cranial Nerve IV (Trochlear)

Controls the superior oblique muscle, allowing for downward and outward eye movement.

Cranial Nerve V (Trigeminal)

Provides sensory innervation to the face and controls muscles for mastication (chewing).

Cranial Nerve VI (Abducens)

Controls the lateral rectus muscle, responsible for abducting the eye (moving it laterally).

Cranial Nerve VII (Facial)

Controls muscles of facial expression, taste sensation from the anterior two-thirds of the tongue, and stimulates lacrimal and salivary glands.

Cranial Nerve VIII (Vestibulocochlear)

Responsible for hearing and balance.

Cranial Nerve IX (Glossopharyngeal)

Involved in taste sensation from the posterior one-third of the tongue, swallowing, and the carotid sinus reflex regulating blood pressure.

Cranial Nerve X (Vagus)

Plays a major role in parasympathetic control of visceral organs, swallowing, and speech.

Cranial Nerve XI (Accessory)

Controls muscles in the neck and shoulder (sternocleidomastoid and trapezius) for head and shoulder movement.

Cranial Nerve XII (Hypoglossal)

Responsible for controlling tongue movements, crucial for speech and swallowing.

Dermatome C2

Innervates the posterior head and superior neck.

Dermatome C3

Innervates the lateral neck and supraclavicular area.

Dermatome C4

Innervates the superior shoulder and lower neck region.

Dermatome C5

Innervates the deltoid region and lateral aspect of the arm.

Dermatome C6

Innervates the lateral forearm, thumb, and index finger.

Dermatome C7

Innervates the middle finger and posterior aspect of the arm and forearm.

Dermatome C8

Innervates the medial aspect of the forearm, ring, and little fingers.

Dermatome T1

Innervates the medial aspect of the arm and forearm up to the axilla.

Dermatome T2

Innervates the axilla and upper medial arm/chest.

Dermatome T3

Innervates the upper anterior chest below T2.

Dermatome T4

Innervates the nipple line area.

Dermatome T5

Innervates the chest region directly below the nipple line.

Dermatome T6

Innervates the chest region at the level of the xiphoid process.

Dermatome T7

Innervates the mid-thoracic region, above the epigastrium.

Dermatome T8

Innervates the upper epigastric region.

Dermatome T9

Innervates the mid-epigastric region.

Dermatome T10

Innervates the skin around the umbilicus (navel).

Dermatome T11

Innervates the region between the umbilicus and groin.

Dermatome T12

Innervates the suprapubic or inguinal region.

Dermatome L1

Innervates the groin and upper medial thigh.

Dermatome L2

Innervates the anterior and medial thigh.

Dermatome L3

Innervates the anterior thigh, knee, and medial leg.

Dermatome L4

Innervates the medial leg, ankle, and great toe.

Dermatome L5

Innervates the lateral leg, dorsum of the foot, and toes 2-4.

Dermatome S1

Innervates the lateral foot, little toe, posterior calf, and posterior thigh.

Dermatome S2

Innervates the posterior thigh and popliteal fossa.

Dermatome S3

Innervates the medial gluteal fold and perianal area.

Dermatome S4-S5

Innervates the perianal region and saddle area.

Free nerve endings

Unencapsulated dendrites found in the skin, epithelia, and connective tissues, primarily detecting pain, temperature, and crude touch. They are the simplest type of sensory receptor.

Tactile discs (Merkel cells)

Mechanoreceptors located in the basal layer of the epidermis, sensitive to light touch and pressure. They adapt slowly, providing information on sustained pressure and touch.

Hair follicle receptors

Mechanoreceptors wrapped around hair follicles, detecting hair movement and light touch. They are rapidly adapting.

Tactile (Meissner's) corpuscles

Encapsulated mechanoreceptors located in the dermal papillae, especially in sensitive, hairless skin (e.g., fingertips, palms, soles). They detect light touch and low-frequency vibration and are rapidly adapting.

Lamellar (Pacinian) corpuscles

Large, encapsulated mechanoreceptors located deep in the dermis and subcutaneous tissue, as well as in other deep tissues. They detect deep pressure, stretch, and high-frequency vibration and are rapidly adapting.

Bulbous (Ruffini's) corpuscles

Encapsulated mechanoreceptors located deep in the dermis and subcutaneous tissue. They are sensitive to deep continuous pressure and stretch (e.g., joint rotation) and are slowly adapting.

Muscle spindles

Proprioreceptors located within skeletal muscles, detecting changes in muscle length and the rate of change of length. They play a crucial role in the stretch reflex.

(Golgi) tendon organs

Proprioreceptors located in the tendons, near the musculotendinous junction. They detect changes in muscle tension and force of contraction, helping to prevent excessive muscle stretch and injury.

Joint kinesthetic receptors

A collective term for mechanoreceptors, Pacinian corpuscles, Ruffini's endings, and free nerve endings located in joint capsules. They provide information about joint position and movement.

Receptor Level (Sensory Integration)

The first level of integration where sensory receptors detect stimuli and convert them into nerve impulses (transduction). The receptor must be specific to the stimulus, and the stimulus must be applied within the receptor's receptive field.

Circuit Level (Sensory Integration)

The second level of integration where ascending pathways transmit sensory impulses from the first-order neurons (receptors) to appropriate regions of the CNS (spinal cord and brainstem), then to the thalamus via second-order neurons, and finally to the somatosensory cortex via third-order neurons.

Perceptual Level (Sensory Integration)

The highest level of integration where the cerebral cortex interprets the sensory input, leading to conscious awareness of the sensation. This involves activities like perceptual detection, magnitude estimation, spatial discrimination, feature abstraction, and quality discrimination.

Sensation

The conscious awareness of changes in the internal and external environment. It is the raw input from sensory receptors.

Perception

The conscious interpretation of sensations, giving meaning to the stimuli. It is how the brain organizes and interprets sensory information.