Noteworthy Nervous System Part 1 The Basics I

Noteworthy Nervous System Part 1 --The Basics

I. Anatomy Central Nervous System (CNS) --Brain and Spinal Cord Peripheral Nervous System (PNS) --Spinal and Cranial Nerves

Functional Classification 1. Sensory/Afferent Division – convey impulses to the CNS from senses 2. Motor/Efferent Division – carries impulses from CNS to effector organs Somatic Nervous system – voluntary control (skeletal system) Autonomic Nervous system – involuntary (smooth/cardiac muscles and glands)

II. Physiology Monitors changes inside and outside the body (sensory input) Processes and interprets sensory inputmakes decisions (integration/association) Effects a response by activating muscles, glands (motor output)

Examples…. . See a red light (sensory), red means stop (integration/association), put foot on brake (motor). Hear a bell (sensory), means end of class (integration/association), walk out (motor)

Astrocytes Anchor the neurons to blood supply

B. Neuroglia - Supporting Cells in CNS Support, Insulate, Protect Divide

Microglia Dispose of debris (dead brain cells, bacteria Diagram: neurons-blue; astrocytes-red; microglia-green

Ependymal Circulate cerebral fluid - cushion

Oligodendrocytes Fatty, insulating covering (myelin sheath)

Supporting cells of PNS 1. Schwann Cells – form myelin sheaths around nerve fibers of peripheral nervous system 2. Satellite cells – protective, cushioning cells

III. Nervous Tissue A. Neurons Transmit messages Don’t Divide Made up of cell body, nucleus, processes Axons: Take messages away from the cell body Dendrites: Take messages toward the cell body

IV. Neuron Functional Classification **Direction of the nerve impulse relative to the CNS** Sensory: From sense organs to CNS (informers) Association (inter): Connect sensory and motor (may have many of these in the chain) Motor: Impulses from CNS to muscle, glands (doers)

Noteworthy Nervous System Part 2 --Fun Fun Physiology

Irritability Ability to respond to a stimulus and convert it to a nerve impulse

Conductivity Ability to transmit the impulse to other neurons, muscles, or glands

I. Irritability (Electrical) A. When a neuron is at rest, it's condition is called Polarized. Sodium is on the outside of the neuron Potassium is on the inside Sodium and potassium gates are closed Inside of neuron has slight negative charge, outside is slightly positive

I. Irritability (Electrical) B. The neuron receives a stimulus from a sense receptor or neuron: Light: stimulates eye receptors Sound: stimulates ear receptors Pressure: stimulates touch receptors Neurotransmitter: stimulates other neurons or muscles/glands

Irritability (Electrical) • • • The stimulus causes changes in the neuron • The impulse will continue to move down the axon as the sodium channels open up along the neuron until it gets to the end of the neuron. Sodium gates in the membrane open Sodium rushes in to the neuron This phase is called Depolarization If a lot of sodium rushes in it generates and Action Potential

II. D. Conductivity (Chemical) • When the impulse gets to the end of a neuron, there is a gap called a Synapse. • An electrical signal can't cross the gap so a chemical signal is used instead. • This starts the Conductivity part of the message.

II. E Conductivity (Chemical) • When the action potential gets to the end of the neuron, it causes vesicles that contain neurotransmitters to move to the end of the neuron. • When they reach the membrane, they release the neurotransmitters and these chemicals travel across the synapse to the next neuron in the line. • If enough neurotransmitter is released, it will cause the sodium gates to open in the next neuron and the action potential will travel through that one too.

Conductivity (chemical) • At the end of the chain, neurotransmitters will be released to activate a muscle or gland to cause a response.

Repolarization • • To prepare a neuron to receive its next message, it must go through a phase called Repolarization. In this phase, sodium gates close and potassium gates open. This causes potassium to leave the neuron. This happens very quickly as the message travels down the axon.

Repolarization • The sodium-potassium pump then uses ATP to pump the sodium out and the potassium back into the neuron. Now the neuron is ready for its next message.

Noteworthy Nervous System Part 3 --Rockin’ Reactions and Reflexes

I. Reactions Voluntary responses to stimulation from the environment Requires time Visual: . 25 sec Hearing: . 17 sec Touch: . 15 sec

II. Reflexes A. Characteristics: Take place without conscious control (often skip brain) Quick Purposeful and Involuntary Always the same (predictable)

II. Reflexes B. Types 1. Autonomic Reflexes Regulate smooth muscles, heart, and glands EX. Secretion of saliva, change in pupil size (pupillary), digestion, elimination, blood pressure, sweating

II. Reflexes B. Types 2. Somatic Reflexes Regulate skeletal muscles EX. Knee jerk (patellar), Pulling away from hot stove

II. Reflexes C. How They Work 1. Sensory neuron reacts to stimulus 2. Interneuron in brain or spinal cord reacts 3. Motor neuron stimulates effector organ

Bravo! For the Bodacious Brain

What’s 3 lbs, pinkish-gray all over, wrinkled like a walnut, and has the texture of oatmeal?

I. Cerebral Hemispheres Paired (left and right) A. Anatomy Gyri and sulci: elevated ridges and shallow grooves Fissures: deep grooves, separated large regions of the brain Lobes: sections named after the bones near them

A. Anatomy (cont) *CORPUS COLLOSUM Very large nerve tract, connects the two hemispheres, allows the two hemispheres to communicate

B. Functions Interprets sensory information Initiates voluntary muscle movements Stores information (memory) Uses memory for reasoning Emotion consciousness

II. Diencephalon (interbrain) Located between cerebral hemispheres and above the midbrain A. Thalamus: crude recognition of pleasant and unpleasant

B. Hypothalamus “under the thalamus” Regulates body temperature, water balance, metabolism, center for emotion (limbic system) Thirst, appetite, sex, pain, pleasure

B. Hypothalamus (cont) Pituitary: Secretes lots of hormones “master gland” Mammilary bodies: Reflex center for smell (olfaction)

C. Epithalamus Pineal Body Regulates day and night cycles Choroid plexis: Knots of capillaries that make cerebrospinal fluid

III. Brain Stem A. Midbrain Corpora Quadrigemina Reflex center for vision and hearing B. Pons Regulates depth and rate of breathing

III. Brain Stem C. Medulla Oblongata Merges into the spinal cord Controls heart rate, blood pressure, breathing, vomiting All nerve fibers connecting brain and spinal cord go through it

IV. Cerebellum Looks like cauliflower Precise timing for skeletal muscle activity Controls balance and equilibrium

V. Protection…. Meninges A. Dura Mater “tough or hard mother” Double layer, one attached to inner surface of skull Blood vessels

V. Protection…Meninges B. Arachnoid Mater “spider”, looks like spiderwebs Surrounds spinal cord No blood vessels

V. Protection…Meninges C. Pia Mater “gentle mother” Thin blood vessels Nourishes cells of the brain and spinal cord, attaches to surface

V. Protection D. Cerebrospinal fluid Made from blood in the brain (choroid plexus) Watery cushion (about half a cup) Protects from blows and other trauma Glucose, proteins, Na. Cl

Protection E. Blood-brain barrier Capillaries of the brain are least permeable in body Water, glucose, amino acids easily pass through Waste and most drugs not allowed to pass Useless against fats, respiratory gases, fatsoluble molecules like alcohol, nicotine, anesthetics