Weber Chapter 25: Neuro Structure and Function

Central Nervous System (CNS)

brain and spinal cord

Peripheral Nervous System (PNS)

cranial and spinal nerves

Meninges

3 connective tissue layers covering CNS

Subarachnoid space

contains cerebrospinal fluid (CSF) which cushions, nourishes, and removes waste from CNS

Upper motor neurons

influence lower motor neurons (mostly in PNS)

Lower motor neurons

stimulate muscles and glands

Cerebrum

Right & left hemispheres connected by corpus callosum; each hemisphere controls opposite side of body

Gray matter (cerebral cortex)

higher functions like memory, perception, communication, voluntary movement

Frontal lobe

Voluntary movement, speech (Broca area), emotions, intellect, reasoning, judgment

Parietal lobe

Touch, pain, temperature, shapes, two-point discrimination

Occipital lobe

Visual processing, reading

Temporal lobe

Auditory processing, language comprehension (Wernicke area)

Thalamus

directs sensory impulses to cerebral cortex

Hypothalamus

regulates water balance, appetite, vital signs, sleep, pain perception, emotions

Midbrain

ear and eye reflex relay

Pons

links cerebellum to cerebrum; reflexes

Medulla oblongata

controls heart rate, BP, respiratory function

Cerebellum

Coordinates voluntary movements, maintains equilibrium and muscle tone

Spinal Cord

Extends from medulla oblongata to L1 vertebra

Gray matter (H-shaped)

inside, processes reflexes

White matter

outside, contains ascending (sensory) and descending (motor) tracts

Stretch reflex

1 sensory neuron → 1 motor neuron → 1 synapse (e.g., knee jerk)

Complex reflexes

involve 3+ neurons

Spinothalamic tract

pain, temperature, crude/light touch

Posterior columns

position, vibration, fine touch

Pyramidal (corticospinal) tract

voluntary skilled movements

Extrapyramidal tract

muscle tone, body control

Cranial nerves

12 pairs

Spinal nerves

31 pairs (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal)

Somatic fibers

voluntary skeletal muscles

Autonomic fibers

involuntary smooth muscles, heart, glands

Sympathetic Nervous System

T1-L2; increases HR, dilates pupils, bronchi; decreases digestion

Parasympathetic Nervous System

craniosacral (CN III, VII, IX, X, S1-S4); restores normal body functions

Posterior columns

Position, vibration, fine touch

Extrapyramidal

Muscle tone, body control

Cranial nerves

12 pairs

Spinal nerves

31 pairs (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal)

Somatic fibers

Voluntary skeletal muscles

Autonomic fibers

Involuntary smooth muscles, heart, glands

Olfactory nerve (I)

Sensory, smell

Optic nerve (II)

Sensory, vision

Oculomotor nerve (III)

Motor, eye movement, pupil constriction, eyelid elevation

Trochlear nerve (IV)

Motor, eye movement (inferomedial)

Trigeminal nerve (V)

Sensory/Motor, face sensation; chewing

Abducens nerve (VI)

Motor, lateral eye movement

Facial nerve (VII)

Sensory/Motor, taste (anterior 2/3 tongue), facial expression, tears, saliva

Vestibulocochlear nerve (VIII)

Sensory, hearing, balance

Glossopharyngeal nerve (IX)

Sensory/Motor, taste (posterior 1/3 tongue), swallowing, salivation

Vagus nerve (X)

Sensory/Motor, sensation from throat, heart, lungs, GI; swallowing, talking, digestion

Spinal accessory nerve (XI)

Motor, neck muscles, shoulder movement

Hypoglossal nerve (XII)

Motor, tongue movement, speech, swallowing

Sensory nerves

Afferent, dorsal root

Motor nerves

Efferent, ventral root

Dermatome

Area of skin supplied by a single spinal nerve

Homeostasis

Maintains homeostasis, involuntary control