Nervous System

I.The Human Body A.Cells - Basic unit of structure and function. B.Tissues - Group of cells that perform a single function (e.g. epithelial, connective, nervous, muscle) C.Organs - Different types of tissues that work together to perform a closely related function (e.g. eye, liver, lungs) Organ Systems D.Organ Systems - Group of organs that perform closely related function (e.g. circulatory, respiratory, digestive) 2

II.Homeostasis A.Definition: Homeostasis is the process by which organisms keep internal conditions relatively constant despite changes in their external environments. B.Requires the integration of all organ systems at the same time C.Nervous system in conjunction with the endocrine system (hormones) is responsible for this integration 3

Room temperature increases Thermostat senses temperature change and switches on heating system Thermostat senses temperature change and switches off heating system Room temperature decreases Section 35-1 Examples of Feedback Inhibition Negative Feedback Example of Homeostasis (Fig. 35-4, p.895) 1.Negative feedback – your body’s response results in decreasing the effect of the stimulus, (e.g. body temperature). The effect is a relatively steady state is maintained. 4

II.Homeostasis 2.Positive feedback – your body’s response results in an increase in the effect of the stimulus, (e.g. the flight-fight response). The effect is that the controlled variable is moved farther from the set point. 5

III.Nervous System A.The nervous system controls and coordinates functions throughout the body and responds to internal and external stimuli. It is one of your bodies communication systems. B.General Functions of the Nervous System: 1.Sensory input – vision, hearing, balance, smell, taste, and touch 2.Motor output – muscle contraction and movement 3.Memory and integration of information 6

IV.Organization of the NS A.Central N.S. 1. Brain 2. Spinal Cord B. Peripheral N.S. 1. Somatic N.S. 2. Autonomic N.S. a. Sympathetic b. Parasympathetic

V.Neurons (Nerve Cells) A.Specialized cells for carrying electrochemical signals called impulses (Fig. 35-5; pg. 897) B.3 Types of Neurons: 1.Sensory – carry impulses from the sense organs to the spinal cord and brain 2.Interneurons – Connect sensory and motor neurons and carry impulses between them 3.Motor – carry impulses from brain and spinal cord to muscles and glands 8

V.Neurons (Nerve Cells) C.Anatomy of a Neuron 1.Cell Body a.Largest part of the neuron b.Contains the nucleus and most of the cytoplasm c.Metabolic activity takes place in the cell body Cell Body 9

V.Neurons (Nerve Cells) 2.Dendrites - Carry impulses from the environment or other neurons to the cell body 10

V.Neurons (Nerve Cells) 3.Axon a.Long fiber that carries impulses away from the cell body b.Ends in axon terminals that contain vesicles for neurotransmitters 11

V.Neurons (Nerve Cells) 4.Myelin Sheath a.Insulates the axon b.Allows impulse to jump from node to node, thus increasing its speed. 12

Nervous Tissue (Neurons ) yellow Which part of the neuron is yellow? Which parts are blue? 13

VI.The Nerve Impulse (How a nerve cell carries a signal) A.The resting neuron. 1.At rest, the outside of the cell has a net positive charge, & the inside has a net negative charge. This charge difference is called the resting potential. (-70mVolts). 14

15 Resting Membrane Potential

VI.The Nerve Impulse 2.The charge difference is created by active transport of the sodium-potassium pump. 3.The sodium-potassium pump moves sodium (Na+) outside the cell, & potassium (K+) inside the cell. Fig

VI.The Nerve Impulse 4.Leakage of K+ ions from the inside of the cell to the outside of the cell creates the net charge difference, so the outside is more positive compared to the inside.  Think of an impulse as the flow of electrical current through a wire 17

VI.The Nerve Impulse B.The moving impulse. 1.An impulse begins when a neuron is stimulated by another neuron or by the environment. 2.The Impulse travels rapidly down the axon away from the cell body & toward the axon terminals. The signal strength does not diminish with distance. 18

VI.The Nerve Impulse 3.The impulse begins by a sudden reversal of membrane potential (electrical charge). Sodium (Na+) channels open & the flood of sodium ions makes the inside positive. _ + + _ 19

VI.The Nerve Impulse 4.As the impulse passes, potassium channel gates open & potassium (K+) flows out which restores the resting potential (charge difference) 5.This reversal of charges, from positive to negative & back again is called a nerve impulse, or an action potential. + _ + _ 20

VI.The Nerve Impulse 6.How do things get back to the original condition? The sodium potassium pump kicks in. 7.The minimum level of a stimulus that is required to activate a neuron is called the threshold potential (-50 to -55mV). Fig

A Nerve Impulse (An Action Potential) Fig

Nerve Impulse Pathway (Action Potential) 23 Action Potential

VII.The Synapse A. The location where a neuron can transfer an impulse to another cell is called a synapse. B. A space called a synaptic cleft separates the axon terminal from dendrites of the adjacent cell. C. The terminals contain tiny sacs filled with neurotransmitters. Neurotransmitters are chemicals used by a neuron to transmit an impulse to another cell. 24

Vesicle Axon Axon terminal Synaptic cleft Neurotransmitter Receptor Dendrite of adjacent neuron Direction of Impulse The Synapse (Fig. 35-8) 25

26 Synaptic Transmission

VIII.Spinal cord A. Two main functions: 1.Reflex center 2.Carries info to and from brain to body 27

IX.Reflexes A.Reflexes are automatic responses to stimuli B.Controlled by 5-part reflex arc: 1. Sensory receptor on finger reacts to stimulus (heat) 2. Impulse is carried to the spinal cord by a sensory neuron. 28

IX.Reflexes 3.In the spinal cord, the impulse is transferred to a motor neuron via an interneuron. 4.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) 29

Nervous System Neuron and Reflex Summary Movie 30

X.The Brain A.Cerebrum 1.The Largest region – 80% of total brain weight. 2.Right and left cerebral hemispheres that are connected by corpus callosum (body’s information super highway) 3.Controls voluntary activities and all higher brain functions Cerebrum Corpus Collosum 31

X.The Brain B. Cerebellum - Center for balance and coordination of voluntary muscle movements. Cerebellum 32

X.The Brain C.Pons & Medulla Oblongata 1.Work together to control breathing, heart rate, blood flow and swallowing. Pons Medulla oblongata 33

X.The Brain D.Thalamus - Is a relay station for all sensory input to the brain. E.Hypothalamus - Homeostatic center which controls Endocrine system (hormones), body temperature, thirst, hunger, anger (emotion) and others. Hypothalamus Thalamus 34

Dr. Amen- Lesson from Brain Scans 35

XI.The Senses A.The Senses 5 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? 1.Vision 2.Hearing and Balance 3.Smell and Taste 4.Touch 36

XII.Nervous System Disorders A.Migraine Headaches – caused by change in serotonin levels? (affected by caffeine, estrogen, certain foods) B.Parkinson’s – progressive loss of nerve cell function that results in loss of muscle movement control; caused by damage to dopamine transmitters; no cure C.Tay-Sachs - lack enzymes to breakdown acidic fatty substances that accumulate in tissues and nerve cells in the brain; results in neurological degeneration; child usually dies by age 4 37

XII.Nervous System Disorders D. Dementia - People with dementia may not be able to think well enough to do normal activities, such as getting dressed or eating. They may lose their ability to solve problems or control their emotions. The most common form of dementia is Alzheimer’s disease & the cause is poorly understood. 38 Alzheimer's Disease

XIII.Drugs & The Nervous System A.Stimulants 1.Accelerate HR, BP, and breathing rate 2.Increases the release of neurotransmitters; leads to release of energy and feeling of well-being 3.When effect wears off, brain’s supply is depleted a.Caffeine b.Cocaine c.Methamphetamines 39

XIII.Drugs & The Nervous System B.Depressants - Slow down HR, lower BP and breathing rate, relax muscles and relieves anxiety 1.Alcohol 2.Marijuana 3.Sleeping Pills 40

Nervous System Flow Chart Sympathetic (activities that increase energy consumption- flight or fight) Parasympathetic (Normalizes body functions) 41

C. Peripheral Nervous System (PNS)  Receives information from the environment and relays to and from CNS and sensory, motor and gland cells 42 XIV.Nervous System Organization PNS Overview

 Peripheral Nervous Systems Two divisions: 1.Sensory - Made of sensory neurons that bring info to the CNS 2.Motor - Made of sensory neurons that convey info from the CNS; two subdivisions a.Somatic (voluntary): respond to external stimuli, & do things like dancing. b.Autonomic (involuntary): respond to internal stimuli w/the parasympathetic and sympathetic divisions Sympathetic ↑ energy consumption Parasympathetic ↓ energy consumption 43 Autonomic Overview