Ch13-17 Anatomy Notes

Central nervous system (CNS)

Includes brain and spinal cord; integrates, processes, and coordinates sensory input and motor output; seat of intelligence, memory, learning, and emotion

Peripheral nervous system (PNS)

All nervous tissue outside CNS; provides sensory information to CNS and carries motor commands from CNS to effectors

Somatic nervous system (SNS)

Efferent division controlling voluntary skeletal muscle contractions

Autonomic nervous system (ANS)

Efferent division controlling involuntary activity of smooth muscle, cardiac muscle, glands, and adipose tissue

Sympathetic division

ANS subdivision (thoracolumbar) most active during stress, exertion, or emergency; “fight or flight”

Parasympathetic division

ANS subdivision (craniosacral) most active at rest; promotes “rest and digest” functions

Neuron

Basic functional unit of nervous system; nerve cell with soma, dendrites, axon, and axon terminals that conducts action potentials

Neuroglia

Supporting cells in CNS and PNS that protect, support, and nourish neurons

Astrocytes

CNS neuroglia that form blood brain barrier, regulate interstitial fluid, and anchor neurons

Oligodendrocytes

CNS neuroglia that form myelin sheaths around CNS axons, creating internodes and nodes

Schwann cells

PNS neuroglia that myelinate segments of peripheral axons or shield groups of unmyelinated axons

Action potential

Rapid, propagated change in membrane potential along the axon that represents a nerve impulse

Chemical synapse

Synapse where neurotransmitter is released from presynaptic vesicles, crosses cleft, and binds receptors on postsynaptic cell

Electrical synapse

Synapse with direct cell

Spinal cord

Cylindrical CNS structure with 31 segments, enlargements, conus medullaris, filum terminale, and cauda equina that conducts information to and from brain

Spinal meninges

Three connective tissue layers (dura mater, arachnoid mater, pia mater) surrounding spinal cord for protection, stability, and shock absorption

Dura mater

Tough, fibrous outer meningeal layer that stabilizes spinal cord and forms epidural space and coccygeal ligament

Arachnoid mater

Middle meningeal layer with subarachnoid space containing cerebrospinal fluid and arachnoid trabeculae

Pia mater

Delicate inner meningeal layer firmly bound to brain and spinal cord surface; contains blood vessels and forms denticulate ligaments

Gray matter

Spinal cord region containing neuron cell bodies and glial cells; organized into posterior, lateral, and anterior horns around central canal

White matter

Spinal cord region containing myelinated and unmyelinated axons organized into posterior, lateral, and anterior columns carrying tracts

Spinal nerve

Mixed peripheral nerve formed by union of dorsal (sensory) and ventral (motor) roots; one pair per spinal segment

Rami communicantes

White (preganglionic) and gray (postganglionic) branches connecting spinal nerve to sympathetic ganglion

Dermatome

A region of skin innervated by sensory fibers of a specific pair of spinal nerves

Nerve plexus

Interwoven network of ventral rami (cervical, brachial, lumbar, sacral) innervating neck, upper limb, pelvic girdle, and lower limb

Cervical plexus

Plexus from ventral rami C1–C4 that innervates neck muscles, diaphragm (phrenic nerve), and skin of head, neck, and chest

Brachial plexus

Plexus from ventral rami C5–T1 that innervates pectoral girdle and upper limb through major nerves such as radial, ulnar, median, and musculocutaneous

Lumbar plexus

Plexus from ventral rami T12–L4 that innervates pelvic girdle and part of lower limb (femoral, obturator, lateral femoral cutaneous, genitofemoral nerves)

Sacral plexus

Plexus from ventral rami L4–S4 that innervates gluteal region, posterior thigh, leg, and foot (sciatic, superior and inferior gluteal, pudendal nerves)

Ascending tract

Sensory pathway carrying information toward the brain (posterior column, spinothalamic, spinocerebellar)

Posterior column tracts

Gracile fasciculus and cuneate fasciculus carrying fine touch, vibration, pressure, and proprioception sensations to cerebral cortex

Spinothalamic tracts

Lateral tract carrying pain and temperature and anterior tract carrying crude touch and pressure to primary sensory cortex

Spinocerebellar tracts

Posterior and anterior tracts carrying proprioceptive information to the cerebellum for coordination

Descending tract

Motor pathway carrying commands from brain to spinal cord and peripheral effectors (corticospinal and subconscious tracts)

Upper motor neuron

CNS neuron whose cell body lies in brainstem or cortex and modulates activity of a lower motor neuron

Lower motor neuron

Motor neuron in brainstem or spinal cord whose axon innervates skeletal muscle fibers

Brain

Major CNS organ including cerebrum, cerebellum, diencephalon, midbrain, pons, and medulla oblongata, responsible for higher functions and vital control

Medulla oblongata

Inferior brainstem region continuous with spinal cord; relays information and contains autonomic nuclei for cardiovascular and respiratory control

Pons

Brainstem bulge superior to medulla with cranial nerve nuclei, respiratory centers, and relay nuclei to cerebellum via cerebellar peduncles

Mesencephalon (midbrain)

Brainstem region with superior and inferior colliculi, red nucleus, and substantia nigra involved in visual and auditory reflexes, muscle tone, and alertness

Diencephalon

Brain region containing thalamus (sensory relay), hypothalamus (autonomic and endocrine control, emotions), and epithalamus (pineal gland)

Cerebellum

Posterior brain region that coordinates complex somatic motor patterns and fine

Cerebrum

Largest brain region with paired hemispheres, gyri, and sulci; responsible for conscious thought, intellectual functions, memory, and voluntary control of skeletal muscles

Ventricular system

Set of four CSF

Cerebrospinal fluid (CSF)

Clear fluid produced by choroid plexus that cushions CNS, supports brain, and transports nutrients and wastes

Choroid plexus

Network of capillaries and specialized ependymal cells in ventricles that produces CSF and helps maintain its composition

Blood brain barrier (BBB)

System of tight endothelial junctions plus astrocyte regulation that restricts movement of substances from blood into CNS interstitial fluid

Sympathetic chain ganglia

Paired ganglia on either side of vertebral column whose postganglionic fibers innervate body wall, limbs, head, neck, and thoracic viscera

Collateral ganglia

Unpaired prevertebral ganglia receiving splanchnic nerves and sending postganglionic fibers to abdominopelvic organs

Adrenal medulla

Inner region of adrenal gland acting as modified sympathetic ganglion that secretes epinephrine and norepinephrine into blood

Visceral reflex

Polysynaptic autonomic reflex arc using preganglionic and postganglionic neurons to produce automatic responses in visceral organs

Long visceral reflex

Visceral reflex in which sensory information travels to CNS and motor output returns via ANS pathways

Short visceral reflex

Visceral reflex in which sensory neurons synapse directly on ganglionic neurons and motor output bypasses CNS

Nicotinic receptor

Type of acetylcholine receptor on all autonomic ganglionic neurons; activation is always excitatory

Muscarinic receptor

Type of acetylcholine receptor on parasympathetic target cells; responses can be excitatory or inhibitory depending on the cell

Dual innervation

Condition in which most visceral organs receive both sympathetic and parasympathetic fibers that often produce opposing (antagonistic) effects