ap test review

Afferent(sensory)

Somatic sensory: skin, skeletal muscles, joints

▪ Visceral sensory: organs, internal environment

Efferent(Motor)

Somatic motor: voluntary → skeletal muscle

▪ Visceral motor: involuntary → smooth muscle, cardiac muscle, glands

Cervical enlargement:

upper limb innervation

Lumbar enlargement:

lower limbs, pelvis

Conus medullaris:

tapered end (L1–L2)

Cauda equina

bundle of spinal nerves below L2

Filum terminale:

pia extension anchoring cord to coccyx

Posterior (dorsal) horn:

sensory processing

Anterior (ventral) horn:

motor neuron cell bodies

Lateral horn:

visceral motor neurons (T1–L2, S2–S4)

Dorsal root:

sensory input → dorsal horn

Dorsal root ganglion:

sensory neuron cell bodies (pseudounipolar)

Ventral root:

motor output from anterior horn

Spinal nerve:

mixed sensory + motor

Anterior median fissure:

deep groove, ventral side

Posterior median sulcus:

shallow groove, dorsal side

Musculocutaneous:

anterior arm (biceps)

Axillary:

deltoid, shoulder sensation

Median:

forearm flexors, carpal tunnel

Radial:

posterior arm/forearm (extension)

Ulnar:

intrinsic hand muscles (“funny bone”)

Femoral nerve:

quadriceps, anterior thigh

Obturator nerve:

medial thigh adductors

Sciatic nerve:

largest nerve → tibial + common fibular

Pudendal nerve:

external genitalia, perineum

Reflex Arc Components (5 Steps)

1. Receptor: detects stimulus

2. Sensory neuron: sends signal to CNS

3. Integration center: one or more synapses

4. Motor neuron: carries command to effector

5. Effector: muscle or gland responds

Innate reflexes

genetically determined (withdrawal, blinking, patellar)

Acquired reflexes:

learned reflexes (driving, conditioned responses)

Spinal reflex:

processed in spinal cord

Cranial reflex:

processed in brainstem

Somatic reflex:

skeletal muscle

Autonomic reflex:

smooth/cardiac muscle, glands

Monosynaptic reflex:

1 synapse (patellar reflex)

Polysynaptic reflex:

multiple synapses (withdrawal, crossed extensor)

Normal adult:

toes curl (plantar flexion)

Abnormal adult:

toes fan → indicates corticospinal tract damage

▪ Normal in infants (due to incomplete myelination)

Somatosensory System detects

o Touch, pressure, vibration

o Temperature

o Pain

o Proprioception

o Itch

Merkel cells:

Slow adapting; small receptive fields

▪ Fine detail, edges, shapes

▪ High spatial resolution

Meissner corpuscles:

Rapid adapting; small receptive fields

▪ Light touch, flutter, low-frequency vibration

▪ Grip control

Pacinian corpuscles:

Rapid adapting; large receptive fields

▪ Deep pressure, high-frequency vibration

▪ Onion-like capsule → rapid adaptation

Ruffini endings:

Slow adapting; large receptive fields

▪ Skin stretch, finger position, hand shape

▪ Important for proprioception

Hair follicle receptors:

Rapid adapting

▪ Detect hair movement & light touch

Thermoreceptors

Free nerve endings

o Cold receptors: peak ~25°C

o Warm receptors: peak ~45°C

o Extreme temps activate nociceptors

Mechanical:

strong pressure, cutting

Thermal:

extreme heat >45°C or extreme cold

Polymodal:

mechanical + thermal + chemical

Silent (visceral):

activated only in inflammation

Muscle Spindles

Detect muscle stretch/length

▪ Initiate stretch reflex

▪ Maintain tone & posture

Golgi Tendon Organs (GTOs)

Detect muscle tension

▪ Prevent damage

Joint Receptors

Detect joint angle extremes, pressure, acceleration

Cerebrum –

conscious thought, memory, voluntary movement

Diencephalon –

thalamus, hypothalamus, epithalamus

Brainstem –

midbrain, pons, medulla

Cerebellum –

coordination, balance

Aa sensory fiber

Largest

Thick myelin fastest

Proprioception (muscle, spindles, GTOs)

Ab sensory fiber

Large

Myelinated

2nd fasted

Touch, vibration, pressure

Aδ Sensory fiber

Small

Thin myelin

3rd fastest

Fast, sharp pain; cold

C fibers sensory

Smallest

None myelin

Slowest

Slow, dull pain; warmth; itch

Gyri (cerebrum)

Folds

Sulci (cerebrum)

Shallow groves

Fissures (cerebrum)

Deep groves

Wernicke’s area →

language comprehension

Hippocampus →

memory formation

Central sulcus

Separates frontal & parietal lobes

Thalamus

Sensory relay center

Hypothalamus

Homeostasis master regulator

Superior colliculi →

visual reflexes

Inferior colliculi →

auditory reflexes

Cerebral peduncles →

motor tracts

Substantia nigra →

dopamine (degeneration → Parkinson’s)

Olfactory

Sensory

Smell

Anosmia, reduced taste

Optic

Sensory

Vision

Visual field loss, blindness, afferent pupillary defect

Oculomotor

Motor and parasympathetic

Eye movement; eyelid elevation; pupil constriction; lens accommodation

Damage: ptosis “down and out” eye, dilated pupil

Trochlear

Motor

Depress and abducts eye

Vertical diplopia; worse going downstairs; head tilt

Trigeminal

Both

Facial sensation; corneal reflect (afferent); chewing

Loss of facial sensation; jaw deviation

Abducens

Both

Abducts eye

Eye deviates medially; cannot abduct; diplopia

Facial

Both and parasympathetic

Facial expression; taste (ant. 2/3); lacrimation; salivation; stapedius control

Bell’s palsy; hyperacusis; dry eye/mouth; loss of taste

Vestibulocochlear

Sensory

Hearing; balance

Vertigo; nystagmus; sensorineural hearing loss

Glossopharyngeal

Both and parasympathetic

Taste (post. 1/3); swallowing; baroreception; parotid gland secretion

Loss of gag reflex (afferent); dysphagia; ↓ salivation

Vagus

Both and parasympathetic

Parasympathetics to viscera; swallowing; speech; visceral sensation

Dysphagia; dysphonia; tachycardia; loss of gag reflex (efferent)

Accessory

Motor

Head rotation; shoulder elevation

Shoulder droop; weak head turn

Hypoglossal

Motor

Tongue movement

Tongue deviates toward lesion; dysarthria

Amygdala

Fear, emotion, threat detection

Hippocampus

Memory consolidation

Cingulate gurus

Motivation, emotion, attention

Alpha

Relaxed

Beta

Alert, problem solving

Thera

Children, light sleep

Delta

Deep sleep