Neuroanatomy and Muscular System: Key Concepts and Definitions

Anterior muscle compartment

Produces flexion

Posterior muscle compartment

Produces extension

Biceps brachii

Flexes elbow and supinates forearm; inserts on radius

Brachialis

Primary elbow flexor; inserts on ulna

Brachioradialis

Flexes elbow in neutral position

Triceps brachii

Extends elbow; inserts on olecranon

Forearm anterior compartment

Flexes wrist and fingers; pronation

Forearm posterior compartment

Extends wrist and fingers; supination

Flexor retinaculum

Holds flexor tendons at wrist

Extensor retinaculum

Holds extensor tendons at wrist

Quadriceps femoris

Prime mover of knee extension

Sartorius

Flexes thigh and knee

Hamstrings

Extend thigh and flex knee

Adductor muscles

Adduct the thigh

Central nervous system (CNS)

Brain and spinal cord

Peripheral nervous system (PNS)

Nerves and ganglia

Neuron

Excitable cell that conducts electrical signals

Glial cells

Support, protect, and insulate neurons

Neuron excitability

Ability to respond to stimulus

Neuron conductivity

Ability to transmit electrical signals

Dendrites

Receive incoming signals

Axon

Conducts signal away from cell body

Synapse

Junction between neurons or effector

Multipolar neuron

One axon, many dendrites

Bipolar neuron

One axon, one dendrite

Unipolar neuron

Single process; sensory

Anaxonic neuron

No axon; local processing

Afferent neuron

Carries sensory information to CNS

Efferent neuron

Carries motor information from CNS

Astrocytes

Maintain BBB and support neurons

Oligodendrocytes

Myelinate axons in CNS

Schwann cells

Myelinate axons in PNS

Microglia

Immune defense in CNS

Myelin sheath

Insulates axon and speeds conduction

Nodes of Ranvier

Gaps in myelin where action potentials occur

Axon regeneration in PNS

Possible if neurilemma intact

Axon regeneration in CNS

Very limited

Resting membrane potential

-70 mV

Sodium-potassium pump

Maintains ion gradients using ATP

Depolarization

Membrane becomes less negative

Repolarization

Return to resting potential

Hyperpolarization

Membrane becomes more negative

Graded potential

Local, variable strength signal

Action potential

All-or-none signal along axon

Threshold

-55 mV

All-or-none law

Action potential either occurs fully or not at all

Spatial summation

Multiple inputs from different neurons

Temporal summation

Rapid repeated input from same neuron

Voltage-gated sodium channels

Open during depolarization

Voltage-gated potassium channels

Open during repolarization

Cerebrum

Conscious thought and voluntary movement

Diencephalon

Thalamus and hypothalamus

Brainstem

Midbrain, pons, medulla

Cerebellum

Coordinates movement and balance

Gray matter

Neuron cell bodies

White matter

Myelinated axons

Dura mater

Tough outer meninx

Arachnoid mater

Middle meninx

Pia mater

Thin inner meninx

Cerebrospinal fluid (CSF)

Cushions and nourishes CNS

Choroid plexus

Produces CSF

Arachnoid villi

Reabsorb CSF

Frontal lobe

Motor control, planning, personality

Parietal lobe

Sensory processing

Temporal lobe

Hearing and memory

Occipital lobe

Vision

Insula

Taste and emotion

Thalamus

Sensory relay station (except smell)

Hypothalamus

Autonomic and endocrine control

Pyramidal decussation

Crossing of motor fibers in medulla

Midbrain

Visual and auditory reflexes

Pons

Regulates breathing rhythm

Medulla oblongata

Heart rate, breathing, blood pressure

Spinal cord

Connects brain to PNS

Conus medullaris

End of spinal cord

Posterior horn

Sensory nuclei

Anterior horn

Motor nuclei

Lateral horn

Autonomic nuclei

Ascending pathways

Carry sensory information to brain

Descending pathways

Carry motor commands from brain

Posterior funiculus pathway

Fine touch, vibration, proprioception

Spinothalamic pathway

Pain and temperature

Spinocerebellar pathway

Proprioception to cerebellum

Corticospinal tract

Voluntary motor control

Cervical plexus

Neck and diaphragm (C1-C4)

Brachial plexus

Upper limb (C5-T1)

Lumbar plexus

Anterior thigh (L1-L4)

Sacral plexus

Posterior leg and foot (L4-S4)

Monosynaptic reflex

One synapse (stretch reflex)

Polysynaptic reflex

Multiple synapses (withdrawal reflex)

Sensory receptor

Detects stimulus and converts it to nerve signal

Mechanoreceptor

Responds to touch or pressure

Chemoreceptor

Responds to chemicals

Photoreceptor

Responds to light

Nociceptor

Pain receptor

Olfaction

Sense of smell; bypasses thalamus

Gustation

Sense of taste

Facial nerve (CN VII)

Taste anterior tongue

Glossopharyngeal nerve (CN IX)

Taste posterior tongue

Rods

Vision in dim light