Nervous System

Nervous System

General FunctionsRecognizes and coordinates the bodys response to changes in its internal and external environments.Sensory input vision, hearing, balance, smell, taste, and touchMotor output muscle contraction and movementMemory and integration of information1Neurons (Nerve Cells)A. Neurons are specialized cells that carry electrical signals called impulses1. 3 Types of Neurons:a. Sensory carry impulses from the sense organs to the spinal cord and brainb. Motor carry impulses from brain and spinal cord to muscles and glandsc. Interneurons Connect sensory and motor neurons and carry impulses between them

2Neurons can protect themselves against infection with HIV, new research has demonstrated. They owe their hardiness to a protein called FEZ-1, made uniquely by neurons, and which appears to lock out the virus1. Cell Bodya. Largest part of the neuronb. Contains the nucleus and most of the cytoplasmc. Metabolic activity takes place in the cell body

Cell Body Anatomy of a Neuron Draw Fig. 35-5; pg. 897 3DendritesCarry impulses from the environment or from other neurons to the cell body

Dendrites4Dendron is Greek for treeAxonLong fiber that carries impulses away from the cell bodyEnds in small swellings called axon terminals

Axon5Sciatic nerve axon is ~ 1 meter longMyelin SheathInsulates the axon; leaves small gaps where the axon is exposedAllows impulse to jump from gap to gap, thus increasing its speed

6Produced by supporting cells called Schwann cells. Made mostly of lipids, which is why they are poor conductors

Nervous Tissue (Neurons)

Which part of the neuron is yellow?Which parts are blue?7The Nerve ImpulseA. The resting neuron1. At rest, the outside of the cell has a net positive charge, and the inside has a net negative charge. This charge difference is called the resting potential (-70mVolts).

8-70mV is about 5% of voltage in AA battery2. This charge difference is due to active transport by the sodium-potassium pump. 3. The sodium-potassium pump moves sodium (Na+) outside the cell, and potassium (K+) inside the cell.

DRAW FIG 35-6, pg. 8989

An impulse begins when a neuron is stimulated by another neuron or by the environment.Sodium pores open on the membrane and sodium ions flood into the neuron.The internal charge goes from -70 mVolts to +30 mVolts.This is called the action potential.

B. The nerve impulse begins

++____++105. The influx of sodium stimulates the opening of potassium pores and (K+) flows out. 6. This restores the resting potential to normal.

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+___+7. But now all of the sodium is inside and the potassium is outside. How does the cell go back to its original condition?The sodium/potassium pump kicks in.11Large concentration gradient for diffusion of K+ out of the cell. Membrane has high permeability to K+, so there will be a net flux off K+ out of the cell. When K+ exits the cell it transfers + charge from the inside of the cell out

++____++8. The depolarization on one segment starts a domino effect down the neuron.+__+

+_+_12The larger the diameter of the axon, the faster the transmission speed. Thin axons have transmission speeds of several cm/sec, but large axons such as in squid have transmission speeds of 100m/sec

A Nerve Impulse (Action Potential)

DRAW FIG 35-7, pg. 89913Nerve Impulse Pathway (Action Potential)

14The Synapse (Draw Fig. 35-8, pg. 900)Def: The gap between the axon of one neuron and the dendrites or cell body of the next neuron.When the impulse reaches the end of the axon, chemicals called neurotransmitters are released and carry the impulse to the next neuron.

VesicleAxonAxon terminalSynaptic cleftNeurotransmitterReceptorDendrite of adjacent neuronDirection of Impulse15Synaptic pruning is just one of many changes thought to be going on inside teenagers' brains. For example, a 2005 study found that teenagers can't multi-task < http://www.livescience.com/health/050517_teen_thought.html> as well as adults because their brains are still learning how to process multiple pieces of information at once they way adults can. In addition to changes that affect how they think, teenagers' brains also undergo developments that affect how they feel. For example, during adolescence people begin to empathize more with others, and take into account how their actions will affect not just themselves, but people around them. A 2006 study found that the teenage medial prefrontal cortex, the part of the brain associated withhigher-level thinking, empathy, and guilt, is underused compared to adults. But as adolescents mature, they begin to use this region more when making decisions, indicating that they increasingly consider others when makingchoices. Synaptic Transmission

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Organization of the NS

Central NS1. Brain2. Spinal CordB. Peripheral NS1. Somatic NS2. Autonomic NSa. Sympatheticb. Parasympathetic17The Brain (Draw Fig. 35-9,p. 901)Cerebrum Largest region; folds and grooves increase surface areaControls voluntary activities and all higher brain functions (intelligence, learning and judgment)Right and left hemispheres are connected by corpus callosum

Cerebrum

Corpus callosum18Brain weighs ~3lbs. Most evolved of all organisms because of cerebrum. Outermost layer is cerebral cortex. Only 5mm thick, but occupies over 80% of total brain mass bc of folds and grooves. Porpoises cerebral cortex is second only to humans. Corpus callosum is how the left and right lobes communicate. Often cut to treat epilepsy. Left lobe is for right side of body and vise-versa.B. CerebellumCenter for balance and coordination of voluntary muscle movements.

Cerebellum19Latin for little brain, Hand eye coordination is here. It contains more nerve cells (neurons) than all the rest of the brain combined, it is a more rapidly acting mechanism than any other part of the brain, and therefore it can process quickly whatever information it receives from other parts of the brain. Third, it receives an enormous amount of information from the highest level of the human brain (the cerebral cortex), which is connected to the human cerebellum by approximately 40 million nerve fibers. Brain StemRelays information between brain and spinal cordComprised of the pons and medulla oblongataWork together to control involuntary processes like breathing, heart rate, blood pressure, digestion, and swallowing

PonsMedulla oblongata20Medulla oblongata: lowest part of the brain,

ThalamusRelay station for all sensory input to the cerebrum. HypothalamusHomeostatic center that controls endocrine system (hormones), body temperature, thirst, hunger, fatigue, etc.

HypothalamusThalamus21Thalamus is integration center. Sorts out sensory info. Hypothalamus weighs only a few grams, but is very important as link between endocrine and nervous systems.Spinal cordTwo main functions: Reflex centerCarries info to and from brain to body

22ReflexesA. Reflexes are automatic responses to stimuliB. Controlled by 5-part reflex arc:1. Sensory receptor reacts to stimulus (heat on finger)2. Impulse is carried to the spinal cord by a sensory neuron3. In the spinal cord, the impulse is transferred to a motor neuron4. Motor neuron conducts a nerve impulse to an effector (arm muscles)5. Effector responds to the impulses by contracting (hand gets pulled away from the heat)

23Peripheral Nervous SystemReceives information from the environment and relays to and from CNS and sensory, motor and gland cells

24Two divisions: Sensory and MotorMotor is divided into:Somatic NS (voluntary) responds to external stimuli.Regulates activities that are under conscious control (e.g. picking your nose)Some reflex controlAutonomic (involuntary) NS respond to internal stimuli; two divisions:Sympathetic energy consumption (increase HR)Parasympathetic energy consumption (decrease HR)Both help maintain homeostasis by having opposing effects

25Parasympathetic center controls things like digestion and slowing heart to conserve energy. Sympathetic center controls accelerating HR, increasing metabolism, thus increasing energy consumptionAutonomic Nervous System

The Senses5 General Sensory Receptors: pain, thermo-, mechano-, chemo- and photoreceptors.Where do you think these different types of receptors are found and what is their function?Pain everywhere but brainThermo temp; skin and hypothalamusMechano pressure, motion and sound; skin, muscles, and earsChemo chemicals; nose and tonguePhoto light; eyes

27pain-everywhere but brain, respond to chemicals released by damaged cellsthermo-skin, body core, hypothalamus, detect variations in tempmechano-skin, skeletal muscles, inner ear, sensitive to pressure, touch, stretching of muslces, sound, motionchemo-nose, taste buds, photo-eyesNervous System DisordersBells Palsy unexplained episode of facial weakness or paralysisDementia - damaged brain cells caused by injury or disease (Alzheimers); memory loss, confusion and personality changeMigraine Headaches caused by a drop in serotonin levels? (triggered by stress, hormones, certain foods)Multiple sclerosis (MS) myelin sheaths deteriorate resulting in progressive loss of coordinationParkinsons uncontrollable shaking caused by damage to dopamine transmitters; no cureTay-Sachs fatal genetic lipid storage disorder where fat builds up on brain tissues and neurons during the first few months of life causing mental and physical deterioration

28Drugs and the Nervous SystemStimulants1. Accelerate HR, BP, and breathing rate2. Increases the release of neurotransmitters; leads to release of energy and feeling of well-being3. When effect wears off, brains supply is depleted leaving the user depressed and fatigueda. Caffeine prevents binding of adenosineb. Cocaine sudden release of dopaminec. Methamphetamines same effect as cocaine

29Endorphins help overcome pain; Dopamine is release when a basic need (hunger/thirst) is met; serotonin gives feeling of wellbeing. Adenosine binds to receptors and makes you drowsy. Caffeine binds to adenosine receptors and blocks the drowsy feelings

DepressantsSlow down HR, lower BP and breathing rate, relax muscles and relieves anxietyAlcohol physical and mental impairment, depression, liver damageMarijuana more lung damage than cigarettes; memory loss, reduced levels of testosterone in malesSleeping Pills

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