The Central Nervous System

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

Meninges: membranes that surround the CNS Three Layers: Dura Mater: outer layer next to bone and continues in vertebral column 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 Conduct nerve impulse along nerve tracts Two Nerve Tracts: Ascending: sensory to brain 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: Interprets sensory information Issues motor commands to skeletal muscles Carries higher mental functions (memory/reasoning) Coordinates muscle movements Centers/pathways for regulatory visceral activities

Brain Organization: Cerebrum (frontal, parietal, temporal, occipital lobes) Cerebellum 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: Sulcus: shallow grooves Fissure: deep grooves Gyrus: elevated ridges

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

1. Primary Motor Areas: in the frontal lobe Located in the Post-central 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 Motor Function Assoc. Function Voluntary muscle Frontal: Concentration, planning, judgment, problem solving Parietal: Temp., touch, pressure, pain Understand speech; words to express thought Temporal: hearing Remembering visuals; music Combining visual images Occipital: vision

Basal Ganglia Serve as a relay station for motor impulses Coordinates motor activities Passes impulses from brain stem to spinal cord 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: Pons Diencephalon Mid brain Medulla oblongata

Diencephalon: 3 parts Thalamus – relay station for incoming sensory inputs Hypothalamus – maintains homeostasis 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: Control hear rate Vasometer center (dilates/constricts blood vessels) 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 Somatic NS (voluntary nerves) Autonomic NS (involuntary ) Two Nerve Types Cranial Nerves (brain) Spinal Nerves (spinal cord)

Cranial Nerves: 12 pairs All originate from brain stem (except 1st pair) Designated by number and function (p. 469)

1. Olfactory Nerve (smell)

2. Optic Nerve (sight)

3. Oculomotor Nerve (eye muscle)

4. Trochlear Nerve (eye muscle)

5. Trigeminal Nerve (mouth)

6. Abducens Nerve (eye muscle)

7. Facial Nerve (facial muscle) – 5 branches (pg 471)

8. Vestibulocochlear Nerve (auditory)

9. Glossopharangeal Nerve (tongue/pharynx)

10. Vagus Nerve (neck and chest)

11. Accessory Nerve (soft palate, pharynx)

12. Hypoglossal Nerve (tongue, speaking, chewing/swallowing)

Spinal Nerves: - 31 pairs from spinal cord Each contains 1000s of nerve fibers Named after the vertebral column

Spinal Nerves C: 8 T: 12 L: 5 S: 5 Co: 1 Total: 31

-Very short Nerves - Divided into dorsal root, ventral root, dorsal ramus, and ventral ramus

Cauda Equina: “horse tail” - the end of the spinal cord Between L1 and L2 Many nerve roots and rootlets

Dermatomes - Area of skin that has sensory nerve fibers from a particular nerve