Final A&P Exam 2 Deck

Central Nervous System (CNS)

Brain and spinal cord; acts as integrative and control center.

Peripheral Nervous System (PNS)

Cranial and spinal nerves; communication lines between CNS and body.

Sensory (Afferent) Division

Conducts impulses from sensory receptors to the CNS.

Motor (Efferent) Division

Transmits impulses from the CNS to effector organs (muscles and glands).

Somatic Nervous System

Voluntary motor control of skeletal muscles.

Autonomic Nervous System (ANS)

Involuntary motor control of smooth muscle, cardiac muscle, and glands.

Sympathetic Division

Branch of ANS that mobilizes body systems during stress ("fight-or-flight").

Parasympathetic Division

Branch of ANS that conserves energy and promotes "rest-and-digest" functions.

Neuron

Structural unit of the nervous system that conducts electrical impulses.

Soma (Cell Body)

Biosynthetic center of a neuron containing the nucleus and organelles.

Dendrites

Receptive inputs of a neuron that convey graded potentials toward the cell body.

Axon

Conducting region of a neuron that generates and transmits action potentials away from soma.

Axon Hillock

Cone-shaped region of soma where the axon originates and action potentials start.

Axon Terminal

Secretory region at axon ends that release neurotransmitters into synaptic clefts.

Nucleus (CNS)

A cluster of neuron cell bodies inside the central nervous system.

Ganglion

A cluster of neuron cell bodies inside the peripheral nervous system.

Tract

A bundle of neuron axons located inside the central nervous system.

Nerve

A bundle of neuron axons located inside the peripheral nervous system.

Schwann Cells

Glial cells that form myelin sheaths around PNS axons.

Oligodendrocytes

Glial cells that form myelin sheaths around CNS axons.

Myelin Sheath Gap (Node of Ranvier)

Unmyelinated gap along an axon between adjacent myelinating cells.

Astrocytes

Most abundant CNS glia; wrap capillaries to form blood-brain barrier and regulate chemical environment.

Microglia

CNS glial cells acting as specialized macrophages to clear debris and pathogens.

Ependymal Cells

Ciliated CNS glial cells lining ventricles to produce and circulate cerebrospinal fluid.

Multipolar Neuron

Neuron with 1 axon and multiple dendrites; most common CNS type.

Bipolar Neuron

Neuron with 1 axon and 1 dendrite; rare, found in special senses (retina, olfactory).

Unipolar Neuron

Neuron with a single process dividing T-like; found in sensory ganglia of PNS.

Resting Membrane Potential (RMP)

Baseline electrical potential across a resting neuron membrane, typically -70 mV.

Na+/K+ ATPase Pump

Active transporter moving 3 Na+ out and 2 K+ in per ATP to maintain resting gradients.

Leakage Channels

Non-gated channels always open for passive ion diffusion down gradients.

Chemically Gated Channels

Ion channels opening when a specific neurotransmitter binds to a receptor.

Voltage-Gated Channels

Ion channels opening or closing in response to changes in membrane potential.

Depolarization

Membrane potential becomes less negative (moves toward zero / positive).

Repolarization

Membrane potential returns to negative resting state after depolarization.

Hyperpolarization

Membrane potential becomes more negative than the resting state (-70 mV).

Graded Potential

Local, short-distance signal on dendrites/soma whose magnitude decays over distance.

Action Potential

Long-distance, non-decaying electrical signal generated along an axon following all-or-none rule.

Threshold Potential

Critical voltage (-55 to -50 mV) required to trigger an action potential.

Absolute Refractory Period

Time during AP when Na+ channels are inactivated; no new AP can fire.

Relative Refractory Period

Time following AP when Na+ channels reset but K+ channels open; exceptional stimulus needed.

Chemical Synapse

Junction where presynaptic neuron releases neurotransmitter to bind postsynaptic receptors.

Voltage-Gated Ca2+ Channels

Channels in axon terminal that open upon AP arrival to trigger exocytosis of neurotransmitters.

Temporal Summation

Rapidly repeated firing from a single presynaptic neuron adding up EPSPs.

Spatial Summation

Simultaneous firing from multiple presynaptic neurons summing EPSPs at axon hillock.

EPSP (Excitatory Postsynaptic Potential)

Local depolarization of postsynaptic membrane bringing potential closer to threshold.

IPSP (Inhibitory Postsynaptic Potential)

Local hyperpolarization of postsynaptic membrane moving potential further from threshold.

Acetylcholine (ACh)

Neurotransmitter active at NMJ, ANS ganglia, and parasympathetic target organs.

GABA

Primary inhibitory neurotransmitter in the central nervous system.

Glutamate

Primary excitatory neurotransmitter in the central nervous system.

Substance P

Neuropeptide that mediates pain signals in the nervous system.

Endorphins

Neuropeptides that act as natural opiates to inhibit pain perception.

Diencephalon

Central core of forebrain containing thalamus, hypothalamus, and epithalamus.

Thalamus

80% of diencephalon; mandatory relay and sorting station for sensory inputs to cortex.

Hypothalamus

Chief visceral control center regulating ANS, temperature, hunger, thirst, and endocrine system.

Suprachiasmatic Nucleus (SCN)

Hypothalamic nucleus acting as master biological clock setting circadian rhythms.

Epithalamus

Dorsal diencephalon containing pineal gland which secretes melatonin.

Pineal Gland

Endocrine gland in epithalamus secreting melatonin to regulate sleep-wake cycles.

Brainstem

Consists of midbrain, pons, and medulla oblongata; controls automatic behaviors.

Midbrain

Brainstem region housing superior/inferior colliculi and substantia nigra.

Superior Colliculi

Midbrain reflex centers coordinating head/eye movement to track visual stimuli.

Inferior Colliculi

Midbrain reflex centers directing auditory startle responses to sudden sounds.

Substantia Nigra

Dopamine-releasing midbrain nucleus involved in motor control.

Pons

Brainstem bridge relaying paths between cerebrum and cerebellum; aids respiratory control.

Medulla Oblongata

Inferior brainstem containing vital cardiac, vasomotor, and respiratory centers.

Pyramidal Decussation

Crossing over of descending motor tracts occurring in the medulla oblongata.

Reticular Activating System (RAS)

Brainstem network maintaining cortical alertness and filtering repetitive sensory input.

Cerebellum

Coordinates smooth, precise skeletal muscle movements, posture, and balance.

Limbic System

Functional brain system mediating emotions, drives, and memory consolidation.

Amygdala

Limbic system structure assessing danger and processing fear responses.

Hippocampus

Limbic system structure essential for long-term memory processing and consolidation.

Primary Motor Cortex

Located in precentral gyrus; controls voluntary skilled muscle movements.

Premotor Cortex

Controls learned, repetitive motor skills and plans complex motor sequences.

Broca's Area

Motor speech area directing muscles involved in speech production.

Primary Somatosensory Cortex

Located in postcentral gyrus; receives sensory input from skin, muscles, and joints.

Somatosensory Association Cortex

Integrates sensory inputs to identify objects by touch/feel alone.

Prefrontal Cortex

Governs intellect, complex learning, personality, judgment, and abstract reasoning.

Wernicke's Area

Brain region responsible for comprehending written and spoken language.

Corpus Callosum

Largest commissural fiber bundle connecting left and right cerebral hemispheres.

Association Fibers

White matter tracts connecting different regions within the same cerebral hemisphere.

Projection Fibers

White matter tracts connecting cerebral cortex to lower brain or spinal cord.

Basal Nuclei

Subcortical gray matter centers regulating movement initiation and inhibition.

Dura Mater

Outermost, toughest double-layered cranial meningeal layer.

Arachnoid Mater

Middle meningeal layer enclosing subarachnoid space filled with CSF.

Pia Mater

Innermost delicate meningeal layer adhering directly to brain and spinal cord tissue.

Choroid Plexus

Capillaries enclosed by ependymal cells in ventricles that produce cerebrospinal fluid.

Arachnoid Granulations

Projections of arachnoid mater reabsorbing CSF into dural venous blood.

Dorsal Horns

Spinal cord gray matter containing interneurons receiving sensory input.

Ventral Horns

Spinal cord gray matter containing somatic motor neuron cell bodies.

Lateral Horns

Spinal cord gray matter in T1-L2 containing sympathetic motor neuron cell bodies.

Dorsal Root Ganglion

Swelling on dorsal spinal root containing sensory neuron cell bodies.

Preganglionic Neuron

First ANS motor neuron with cell body in CNS and lightly myelinated axon.

Postganglionic Neuron

Second ANS motor neuron with cell body in ganglion and unmyelinated axon to effector.

Autonomic Ganglion

Peripheral cluster of cell bodies where preganglionic ANS fibers synapse with postganglionic neurons.

Thoracolumbar Division

Sympathetic division origin site in T1 to L2 spinal cord segments.

Craniosacral Division

Parasympathetic division origin site in brainstem and S2-S4 spinal cord segments.

Sympathetic Trunk Ganglia

Paired ganglia arranged parallel to spinal cord along vertebral column.

Terminal Ganglia

Parasympathetic ganglia located within or very near the wall of target effector organs.

Vagus Nerve (CN X)

Cranial nerve carrying ~90% of all preganglionic parasympathetic fibers.

Cholinergic Fibers

Neurons that release acetylcholine (ACh) as their neurotransmitter.

Adrenergic Fibers

Neurons that release norepinephrine (NE) as their neurotransmitter.