M06 test a + P

Peripheral Nervous System

Includes sensory receptors, peripheral nerves, associated ganglia, and motor endings.

Two main divisions of the PNS

Sensory (afferent) and Motor (efferent).

Sensory division

Carries impulses toward the CNS.

Motor division

Carries impulses away from the CNS.

Two divisions of the motor system

Somatic (voluntary skeletal muscles) and Autonomic (involuntary smooth/cardiac muscle and glands).

Neuron cell bodies of the PNS

Found in the CNS or in ganglia outside the CNS.

Types of sensory receptors

Mechanoreceptors, thermoreceptors, photoreceptors, chemoreceptors, and nociceptors.

Receptors classified by location

Exteroceptors, interoceptors, and proprioceptors.

Three levels of sensory integration

Receptor level, circuit level, and perceptual level.

Receptor adaptation

A change in sensitivity during constant stimulation where receptor response decreases.

Phasic receptors

Fast-adapting receptors that signal changes such as touch or pressure.

Tonic receptors

Slow-adapting receptors such as nociceptors and proprioceptors.

Pain perception's purpose

Warns of actual or potential tissue damage.

Substances triggering nociceptors during injury

Histamine, potassium, ATP, acids, and bradykinin.

Referred pain

Pain felt in an area different from its origin due to shared nerve pathways.

Connective tissue layers surrounding a nerve

Endoneurium, perineurium, and epineurium.

Mixed nerve

A nerve containing both sensory and motor fibers.

Ganglion

A cluster of neuron cell bodies in the PNS.

Difference between tracts and nerves

Tracts are in the CNS; nerves are in the PNS.

Peripheral nerves regeneration

Peripheral nerves can regenerate because Schwann cells promote regeneration; CNS oligodendrocytes inhibit it.

Pairs of cranial nerves

12 pairs.

Cranial nerve controlling smell

CN I Olfactory nerve.

Cranial nerve controlling vision

CN II Optic nerve.

Cranial nerve controlling most eye movements and pupil constriction

CN III Oculomotor nerve.

Cranial nerve controlling the superior oblique muscle

CN IV Trochlear nerve.

Cranial nerve providing facial sensation and mastication

CN V Trigeminal nerve.

Cranial nerve moving the lateral rectus muscle of the eye

CN VI Abducens nerve.

Cranial nerve controlling facial expression and taste on anterior tongue

CN VII Facial nerve.

Cranial nerve controlling hearing and balance

CN VIII Vestibulocochlear nerve.

Cranial nerve controlling swallowing and taste on posterior tongue

CN IX Glossopharyngeal nerve.

Cranial nerve controlling heart, lungs, and digestive organs

CN X Vagus nerve.

Cranial nerve controlling the trapezius and sternocleidomastoid muscles

CN XI Accessory nerve.

Cranial nerve controlling tongue movements for speech and swallowing

CN XII Hypoglossal nerve.

Condition resulting from facial nerve paralysis

Bell's Palsy.

Phrase 'mixed nerves' in cranial nerve classification

They carry both sensory and motor fibers.

Pairs of spinal nerves

31 pairs.

Spinal nerve groups

8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal.

Ventral roots

Contain motor (efferent) fibers from ventral horn neurons.

Dorsal roots

Contain sensory (afferent) fibers from dorsal root ganglia.

Spinal nerve

A short mixed nerve formed by dorsal and ventral roots.

Ramus

A branch of a spinal nerve (dorsal or ventral).

Dorsal ramus innervation

Muscles and skin of the back.

Ventral ramus innervation

Muscles and skin of the limbs and anterior body wall.

Rami communicantes

Small branches connecting spinal nerves to sympathetic ganglia.

Nerve plexus

A network of intersecting nerves.

Four main nerve plexuses

Cervical, brachial, lumbar, and sacral.

Phrenic nerve

The nerve that arises from the cervical plexus and innervates the diaphragm (C3-C5).

Five major nerves of the brachial plexus

Axillary, musculocutaneous, median, ulnar, and radial.

Major nerve of the lumbar plexus

Femoral nerve.

Major nerve of the sacral plexus

Sciatic nerve.

Dermatome

A region of skin innervated by a single spinal nerve.

Reflex

A rapid, automatic, predictable response to a stimulus.

Five components of a reflex arc

Receptor, sensory neuron, integration center, motor neuron, effector.

Somatic reflexes

Reflexes that activate skeletal muscles.

Autonomic reflexes

Reflexes that activate smooth or cardiac muscle and glands.

Stretch reflex

A monosynaptic, ipsilateral reflex that resists muscle stretch.

Reciprocal inhibition

The relaxation of antagonist muscles during a stretch reflex.

Patellar reflex

An example of a stretch reflex.

Flexor (withdrawal) reflex

A polysynaptic, ipsilateral reflex withdrawing a body part from pain.

Crossed-extensor reflex

A reflex causing extension of the opposite limb for balance.

Positive plantar response in adults

Extension and abduction of toes indicating corticospinal damage (Babinski sign).

Normal plantar reflex in adults

Toe flexion (negative Babinski).

Cremasteric reflex

Stroking the inner thigh causes elevation of the ipsilateral testis.

Autonomic Nervous System (ANS)

Controls involuntary activity of smooth muscle, cardiac muscle, and glands.

Two divisions of the ANS

Sympathetic and Parasympathetic.

Another name for the ANS

Involuntary or general visceral motor system.

Neurons in an autonomic pathway

Two: preganglionic and postganglionic.

Location of preganglionic neuron cell body

In the CNS.

Location of postganglionic neuron cell body

In an autonomic ganglion outside the CNS.

Neurotransmitters used by the ANS

Acetylcholine (ACh) and Norepinephrine (NE).

Role of the parasympathetic division

Rest and digest; conserves energy and promotes digestion.

Role of the sympathetic division

Fight or flight; mobilizes the body during activity.

Origin of parasympathetic fibers

Craniosacral regions (brainstem and sacral spinal cord).

Origin of sympathetic fibers

Thoracolumbar regions (T1-L2).

Location of sympathetic ganglia

Near the spinal cord (paravertebral chain).

Location of parasympathetic ganglia

Near or within target organs.

Neurotransmitter released by preganglionic neurons in both divisions

Acetylcholine (ACh).

Neurotransmitter released by most sympathetic postganglionic neurons

Norepinephrine (NE).

Cholinergic fibers

Nerves that release ACh.

Adrenergic fibers

Nerves that release NE.

Nicotinic and muscarinic receptors

Two types of cholinergic receptors that bind ACh.

Alpha and beta receptors

Adrenergic receptors that bind norepinephrine.

Sympathetic tone

Continuous partial constriction of blood vessels by sympathetic fibers.

Parasympathetic tone

Resting influence that slows the heart and promotes digestion.

Cooperative effects in the ANS

Parasympathetic causes erection; sympathetic causes ejaculation or vaginal contraction.

Controlled only by the sympathetic system

Adrenal medulla, sweat glands, arrector pili muscles, kidneys, and most blood vessels.

Main control center for the ANS

The hypothalamus.

Common ANS disorders

Hypertension, Raynaud's disease, and autonomic dysreflexia.

Difference between localized and diffuse effects in the ANS

Parasympathetic effects are localized and short; sympathetic effects are widespread and longer lasting.