The Peripheral Nervous System I

These flashcards cover key concepts related to the Peripheral Nervous System from the lecture notes.

Peripheral Nervous System (PNS)

The part of the nervous system that links the outer world to the central nervous system, encompassing all neural structures outside the brain and spinal cord.

Sensory Receptors

Structures that receive sensory stimuli and convert them into neural impulses for the nervous system.

Mixed Nerves

Nerves that contain both sensory (afferent) and motor (efferent) fibers, transmitting impulses in both directions.

Ganglia

Clusters of neuronal cell bodies located in the peripheral nervous system.

Endoneurium

The delicate connective tissue that surrounds individual axons within a nerve.

Epineurium

The tough fibrous sheath that encases all fascicles in a nerve.

Cranial Nerves

Twelve pairs of nerves that primarily serve the head and neck, some with sensory functions, others with motor functions.

Dermatome

An area of skin that is innervated by a specific spinal nerve.

Phrenic Nerve

A nerve arising from the cervical plexus that innervates the diaphragm, critical for breathing.

Brachial Plexus

A network of nerve fibers that supplies the upper limb, formed by the ventral rami of C5-T1.

Accessory Nerve (XI)

A cranial nerve that innervates sternocleidomastoid and trapezius muscles, enabling head and neck movements.

Hypoglossal Nerve (XII)

A motor nerve responsible for controlling tongue movements, essential for swallowing and speech.

Spinal Nerves

Thirty-one pairs of nerves that originate from the spinal cord, responsible for innervating the rest of the body.

Perineurium

The connective tissue sheath that bundles groups of axons into fascicles within a nerve.

Nerve Plexus

A network of intersecting nerves, typically found in the somatic nervous system, which reorganizes fibers into different peripheral nerves.

Somatic Nervous System (SNS)

The division of the peripheral nervous system that controls voluntary movements of skeletal muscles and transmits sensory information from the skin, muscles, and special senses.

Afferent (Sensory) Fibers

Nerve fibers that transmit impulses from sensory receptors towards the central nervous system.

Efferent (Motor) Fibers

Nerve fibers that transmit impulses from the central nervous system out to muscles and glands.

Autonomic Nervous System (ANS)

The division of the PNS that regulates involuntary bodily functions such as heart rate, digestion, respiration, and sexual arousal.

Sympathetic Division (of ANS)

The 'fight-or-flight' branch of the ANS, responsible for mobilizing the body's resources for stressful situations.

Parasympathetic Division (of ANS)

The 'rest-and-digest' branch of the ANS, responsible for conserving energy and promoting basic bodily functions.

Vagus Nerve (X)

A major cranial nerve extending to the thorax and abdomen, playing a vital role in involuntary functions like heart rate, digestion, and respiration.

Dorsal Root (Spinal Nerve)

The posterior root of a spinal nerve containing afferent (sensory) fibers that carry impulses from sensory receptors to the spinal cord.

Ventral Root (Spinal Nerve)

The anterior root of a spinal nerve containing efferent (motor) fibers that carry impulses from the spinal cord to muscles and glands.

Cervical Plexus

A nerve network formed by ventral rami of C1-C5, innervating muscles and skin of the neck, ear, back of head, and shoulders, and supplying the diaphragm via the phrenic nerve.

Lumbar Plexus

A nerve network formed by ventral rami of L1-L4, supplying the thigh, abdominal wall, and psoas muscle, with major branches including the femoral and obturator nerves.

Sacral Plexus

A nerve network formed by ventral rami of L4-S4, innervating the buttock, posterior thigh, lower leg, foot, and pelvic structures, famously giving rise to the great sciatic nerve.

Reflex Arc

The complete neural pathway involved in a reflex action, consisting of a sensory receptor, afferent neuron, integration center, efferent neuron, and effector organ.

Olfactory Nerve (I)

A purely sensory cranial nerve responsible for the sense of smell.

Optic Nerve (II)

A purely sensory cranial nerve responsible for transmitting visual information from the retina to the brain.

Trigeminal Nerve (V)

A mixed cranial nerve that mediates facial sensation (pain, touch, temperature) and controls muscles of mastication (chewing).

Facial Nerve (VII)

A mixed cranial nerve primarily controlling muscles of facial expression, and also involved in taste sensation from the anterior two-thirds of the tongue and glandular secretions.

Sciatic Nerve

The largest nerve in the human body, originating from the sacral plexus, typically innervating the posterior thigh and the entire lower leg and foot.

Femoral Nerve

A major nerve arising from the lumbar plexus that innervates the anterior muscles of the thigh (e.g., quadriceps femoris) and skin on the anterior thigh and medial leg.

Obturator Nerve

A nerve originating from the lumbar plexus that primarily innervates the adductor muscles of the medial thigh.

Schwann Cells

Neuroglial cells found in the PNS that form the myelin sheath around axons, aiding in faster nerve impulse conduction.

Satellite Cells

Neuroglial cells in the PNS that surround the cell bodies of neurons in ganglia, providing support and regulatary functions.

Proprioceptors

Sensory receptors located in muscles, tendons, and joints that provide information about body position and movement.

Nociceptors

Sensory receptors that detect painful stimuli, responding to actual or potential tissue damage.

Mechanoreceptors

Sensory receptors that respond to mechanical forces such as touch, pressure, vibration, and stretch.

Thermoreceptors

Sensory receptors that are specialized to detect changes in temperature.

Chemoreceptors

Sensory receptors that detect the presence of specific chemicals, involved in taste, smell, and monitoring blood chemistry.