Chapter 9 – The Nervous System: Spinal Cord & Spinal Nerves

Vocabulary flashcards covering major terms related to neuronal structure, function, spinal cord anatomy, nerve physiology, reflexes, autonomic pathways, and clinical conditions from Chapter 9.

Central nervous system (CNS)

The brain and spinal cord; acts as the body’s primary control and integration center.

Peripheral nervous system (PNS)

All nervous tissue outside the CNS; includes cranial and spinal nerves.

Somatic nervous system

Division of the PNS that provides voluntary control of skeletal muscles.

Autonomic nervous system (ANS)

Involuntary motor division of the PNS that regulates glands, smooth muscle, and cardiac muscle.

Sympathetic nervous system

ANS division that produces the fight-or-flight stress response.

Parasympathetic nervous system

ANS division that promotes rest-and-digest (SLUDD) functions and conserves energy.

Neuron

The functional nerve cell that transmits electrical impulses.

Cell body (soma)

Portion of a neuron containing the nucleus and most organelles.

Dendrite

Branchlike neuron process that carries impulses toward the cell body.

Axon

Long neuron process that carries impulses away from the cell body.

Myelin sheath

Fatty insulating covering around many axons that speeds impulse conduction.

Schwann cell

PNS glial cell that forms myelin and the neurilemma around peripheral axons.

Oligodendrocyte

CNS glial cell that forms myelin sheaths around central axons.

Node of Ranvier

Gap between adjacent myelin segments where action potentials occur.

White matter

CNS tissue composed mainly of myelinated axons.

Gray matter

CNS tissue made of neuron cell bodies and unmyelinated fibers.

Sensory (afferent) neuron

Neuron that carries impulses from receptors toward the CNS.

Motor (efferent) neuron

Neuron that carries impulses from the CNS to muscles or glands.

Interneuron

Neuron located within the CNS that connects sensory and motor pathways.

Nerve

Bundle of axons (fibers) in the PNS surrounded by connective tissue.

Tract

Bundle of axons located within the CNS.

Endoneurium

Delicate connective tissue surrounding each individual nerve fiber.

Perineurium

Connective tissue wrapping that surrounds a fascicle (axon bundle) in a nerve.

Epineurium

Outermost connective tissue layer enclosing an entire nerve.

Ganglion

Collection of neuron cell bodies located outside the CNS.

Plexus

Network of intersecting spinal nerves that redistribute fibers to peripheral nerves.

Dermatome

Skin region supplied by a single spinal nerve.

Action potential

Rapid, self-propagating change in membrane potential used to transmit a nerve impulse.

Resting membrane potential

−70 mV charge difference across a neuron membrane when unstimulated.

Depolarization

Phase of an action potential when the membrane potential becomes less negative.

Repolarization

Return of the membrane potential toward resting levels after depolarization.

Hyperpolarization

Membrane potential becomes more negative than the resting level.

Saltatory conduction

Jumping of action potentials between Nodes of Ranvier on a myelinated axon.

Synapse

Junction where a neuron communicates with another cell via neurotransmitters.

Neurotransmitter

Chemical messenger that carries signals across a synaptic cleft.

Acetylcholine (ACh)

Primary cholinergic neurotransmitter; released at neuromuscular junctions and many ANS synapses.

Norepinephrine (NE)

Adrenergic neurotransmitter released by most sympathetic postganglionic neurons.

Nicotinic cholinergic receptor

ACh-binding receptor on skeletal muscle cells and all ANS ganglionic neurons.

Muscarinic cholinergic receptor

ACh-binding receptor on parasympathetic target organs and all postganglionic ANS neurons.

Adrenergic receptor

Receptor that binds epinephrine or norepinephrine on sympathetic target cells.

Reflex arc

Pathway from receptor to effector producing an automatic response.

Stretch reflex

Simple reflex that contracts a muscle in response to being stretched (e.g., knee-jerk).

Withdrawal reflex

Protective reflex that pulls a body part away from painful stimuli.

Cerebrospinal fluid (CSF)

Clear fluid that cushions the CNS; fills the ventricles and central canal.

Lumbar puncture

Procedure that removes CSF from the subarachnoid space for analysis.

Epidural

Injection of anesthetic into the epidural space around the spinal cord.

Multiple sclerosis (MS)

Autoimmune demyelinating disease of CNS neurons leading to sensory and motor deficits.

Neuropathy

Any disorder or disease affecting peripheral nerves.

Carpal tunnel syndrome

Mononeuropathy caused by compression of the median nerve in the wrist.

Phrenic nerve

Cervical plexus nerve that innervates the diaphragm and controls breathing.