CNS and PNS

Central Nervous System (CNS)

Includes the brain and spinal cord; processes and coordinates sensory data and motor commands.

Gray Matter

Contains neuron cell bodies; site of processing.

White Matter

Contains myelinated axons; responsible for communication between brain regions.

Meninges

Three protective layers around the CNS: dura mater, arachnoid mater, pia mater.

Cerebrospinal Fluid (CSF)

Clear fluid that cushions the brain and spinal cord; circulates in ventricles and subarachnoid space.

Brain Stem

Made of midbrain, pons, medulla oblongata; controls basic life functions (e.g., breathing, heart rate).

Cerebellum

Coordinates movement and balance; fine-tunes motor activity.

Cerebral Hemispheres

Left: logic, language; Right: spatial skills, emotion, creativity.

Primary Motor Cortex

Controls voluntary muscle movement; located in frontal lobe.

Primary Somatosensory Cortex

Processes touch and proprioceptive input; located in parietal lobe.

Broca’s Area

Motor speech area; damage = difficulty speaking.

Wernicke’s Area

Language comprehension; damage = trouble understanding speech.

Prefrontal Cortex

Involved in decision making, personality, and social behavior.

Thalamus

Relay center for sensory input; involved in memory and alertness.

Hypothalamus

Controls autonomic nervous system and endocrine system; regulates hunger, thirst, temperature.

Limbic System

Processes emotions and memory; includes hippocampus and amygdala.

Reticular Formation

Regulates alertness and consciousness.

Blood-Brain Barrier (BBB)

Selective filter that protects brain from harmful substances in the blood.

Peripheral Nervous System (PNS)

All nerves outside the brain and spinal cord; connects CNS to the rest of the body.

Sensory Receptors

Detect environmental changes (stimuli); send signals to CNS.

Mechanoreceptors

Detect touch, pressure, vibration, and stretch.

Thermoreceptors

Detect changes in temperature.

Photoreceptors

Detect light (e.g., in the retina).

Chemoreceptors

Detect chemicals (e.g., smell, taste, blood pH).

Nociceptors

Detect pain stimuli.

Proprioceptors

Inform brain about body position and movement.

Cranial Nerves

12 pairs; mostly serve head and neck; include sensory, motor, or both functions.

Spinal Nerves

31 pairs; carry motor and sensory information to/from spinal cord.

Nerve Plexus

Network of intersecting spinal nerves; major ones: cervical, brachial, lumbar, sacral.

Reflex

Automatic, rapid response to a stimulus.

Stretch Reflex

Muscle contraction triggered by muscle stretch (e.g., knee jerk).

Tendon Reflex

Prevents damage by relaxing muscle under too much tension.

Dermatomes

Skin areas innervated by a single spinal nerve; used in neuro assessments.

Somatic Reflex

Activates skeletal muscles (voluntary system).

Autonomic Reflex

Activates glands, smooth or cardiac muscle (involuntary system).

PNS Nerve Regeneration

Possible with intact Schwann cells and endoneurium.

CNS Nerve Regeneration

Not possible due to inhibitory factors and scar formation.