The Central Nervous System Components Brain and spinal

The Central Nervous System

Components: - Brain and spinal cord - Bone: skull/vertebral column - Membranes and fluid

Meninges: membranes that surround the CNS Three Layers: 1. Dura Mater: outer layer next to bone and continues in vertebral column 2. Arachnoid mater: middle layer; covers brain/spinal cord 3. Pia mater: inner layer that covers nervous tissue. FX: nourishmenst of nerve

Meningitis: inflammation of meninges that is caused by bacteria/virus - Mainly infects children - May cause: - Loss of vision/hearing - Paralysis - Mental Retardation

Cerebral Spinal Fluid (CSF): clear, watery substance that brings nutrients and protection to neurons - Fills the subarachnoid space - 500 ml secreted daily/absorbed by blood - Absorbs forces which may damage brain

Spinal Cord: - 31 segments (vertebrae) - Each segment has a pair of spinal nerves - Branch out into body (PNS) - Central canal filled with CSF

White vs. Gray Matter White Matter: neuron tissue with myelinated axons Gray Matter: neuron tissue with unmyelinated axons

Spinal Cord Functions 1. Conduct nerve impulse along nerve tracts Two Nerve Tracts: A. Ascending: sensory to brain B. Descending: motor impulse to organ/gland 2. Center for spinal reflexes

Reflexes: quick, involuntary, predictable reactions - does not involve the brain - Reflex arc: sensory neuron interneuron motor neuron Ex. Knee-jerk reaction, pain reaction

The Brain Primary Functions: 1. Interprets sensory information 2. Issues motor commands to skeletal muscles 3. Carries higher mental functions (memory/reasoning) 4. Coordinates muscle movements 5. Centers/pathways for regulatory visceral activities

Brain Organization: 1. Cerebrum (frontal, parietal, temporal, occipital lobes) 2. Cerebellum 3. Brain Stem – connect brain to spinal stem - Diencephalon Midbrain Pons Medulla oblongata

Cerebrum: - Largest part of the brain - Divided into two primary lobes: -right and left cerebral hemispheres Corpus Callosum: nerve fibers for connections and communications between hemispheres

Cerebrum Surface Features: 1. Sulcus: shallow grooves 2. Fissure: deep grooves 3. Gyrus: elevated ridges

Cerebral Cortex: outside of the cerebrum - Gray matter, 2 -5 mm, white matter beneath FX: 1. Motor areas (voluntary): 2. Sensory areas (interpretation) 3. Association areas (conscious behavior)

1. Primary Motor Areas: in the frontal lobe - Located in the Postcentral and Pre-central gyrus - Brocc’s: controls muscle action of mouth, tongue, larynx - Pgs: 410 -414

2. Association Areas: higher info processes - Control memory, reasoning, verbalizing, judgment, emotion, concentration, planning, problem solving

Cerebral Lobes and Their FX: Sensory Function Voluntary muscle Frontal: Parietal: Temporal: Occipital: Motor Function Temp. , touch, pressure, pain Assoc. Function Concentration, planning, judgment, problem solving Understand speech; words to express thought hearing Remembering visuals; music vision Combining visual images

Basal Ganglia 1. Serve as a relay station for motor impulses 2. Coordinates motor activities 3. Passes impulses from brain stem to spinal cord 4. Secretes dopamine - Gray matter deep in cerebrum

Ventricles (409) - Interconnecting cavities deep in cerebral hemispheres and brain stem - Continuous with central canal of spinal cord - Filled with CSF - Creates bouancy for the brain

Brain Stem: - Region of brain that connects the cerebrum to spinal cord Four Parts: 1. Pons 2. Diencephalon 3. Mid brain 4. Medulla oblongata

Diencephalon: 3 parts 1. Thalamus – relay station for incoming sensory inputs 2. Hypothalamus – maintains homeostasis 3. Limbic System: produces emotions and modifies behavior; fear, anger, pleasure, sorrow

Pons: “bridge” - Regulates breathing rhythm - Relays impulses from cerebrum to spinal cord - 3 cranial nerves from pons

Medulla Oblongata FX: 1. Control hear rate 2. Vasometer center (dilates/constricts blood vessels) 3. Regulates breathing with pons

Reticular Formation: FX: consciousness by interconnecting several portions of the brain

Sleep: suspension of voluntary body functions and consciousness (partial) Two Types: determined by electro encephalogram (EEG)

1. Non Rapid Eye Movement (NREM) - Waves are slower; longer wavelength - 4 stages (I – IV) - “light” sleep to “deep” sleep

2. Rapid Eye Movement (REM) - “Paradoxical Sleep” - Most important type of sleep - Allows the portions of the brain to rest - Higher oxygen consumption in brain than when awake - Dreaming occurs - Increased body temp. , heart rate, respiratory and blood pressure - Muscle inhibition - 90 minutes after sleep begins

Sleep Importance: - 1/3 of our lives is spent asleep Lack of REM leads to depression and other disorders Brain works through days events/emotions Dream: “frustrated desires and attempts to fulfill one’s wishes” – Freud Alcohol suppresses REM Sleep requirements change as we age (16 hrs to 7 hrs as adults) Adults are light sleepers Daily mediation/prayer increases REM

The Peripheral Nervous System Two Branches 1. Somatic NS (voluntary nerves) 2. Autonomic NS (involuntary ) Two Nerve Types 1. Cranial Nerves (brain) 2. Spinal Nerves (spinal cord)