Nervous System Transmission of signals for communication and for coordination of body systems

Organization of Body Systems CellTissue Organ Organ System Central Nervous System Brain Neuron Nerve

Structure of a Neuron Cell Body Dendrites Axon of another neuron Axon Myelin Sheath Dendrites of another neuron

Transmission of Nerve Impulse Along a Neuron Involves a change in charge across the neuron’s membrane, caused by the movement of ionsInvolves a change in charge across the neuron’s membrane, caused by the movement of ions Action Potential = rapid depolarization and repolarization of membraneAction Potential = rapid depolarization and repolarization of membrane

Electrical Events During An Action Potential Recorded Potential (millivolts) Time (milliseconds) Resting Potential Extracellular Fluid (uncharged) Threshold IPSP EPSP Action Potential Action Potential depolarization repolarization polarized

Org - Resting Potential Depends on Ionic Gradients K+K+K+K+ K+K+K+K+ K+K+K+K+ K+K+K+K+ K+K+K+K+ K+K+K+K+ K+K+K+K+ Na + Cl - Inside: Potassium ions are pumped into cell Large organic molecules cannot pass through membrane Outside: Sodium ions are pumped out Chloride ions found in extra- cellular fluid Net negative charge inside neuron

An Unstimulated Neuron at Resting Potential (Extracellular Fluid) (Neuronal Cytoplasm, negatively charged) (Neuronal Membrane) ( N e u r o n a l M e m b r a n e ) Org - Na + Org - K+K+K+K+ K+K+K+K+ K+K+K+K+ K+K+K+K+ K+K+K+K+ Cl - Na + Potassium Channel Sodium Channel (closed)

Org - Na + Org - K+K+K+K+ K+K+K+K+ Cl - Na + K+K+K+K+ K+K+K+K+ K+K+K+K+ K+K+K+K+ Cl - Action Potential Org - K+K+K+K+ K+K+K+K+ K+K+K+K+ Cl - Na + K+K+K+K+ (Extracellular Fluid) (Neuronal Cytoplasm, positively charged) ( (negatively charged) (negatively charged) Depolarization due to influx of sodium Repolarization due to efflux of potassium

Propagation of an Action Potential

Intensity of Nerve Signals Gentle Touch Moderate Pressure Strong Pressure Fires slowly Silent Fires more rapidly Silent Fires even faster Fires slowly

Transmission of Nerve Impulses Between Neurons Signal is carried by neurotransmitters that diffuse across the space between neuronsSignal is carried by neurotransmitters that diffuse across the space between neurons –Synapse: junction between neurons –Synaptic cleft: space between neurons Neurotransmitters bind to receptors on next neuron, opening ion channelsNeurotransmitters bind to receptors on next neuron, opening ion channels synapse

Structure and Operation of the Synapse 1An action potential is initiated 2Action potential reaches synaptic terminal 3Synaptic vesicles release neurotransmitter 4Receptor binds neurotransmitter & opens ion channel 5Action Potential can be triggered in post-synaptic cell

Transmission of Nerve Impulses Between Neurons Neurotransmitters can be Stimulatory: initiate action potential eg. Acetylcholine Inhibitory: prevent action potential eg. Dopamine

Neurotransmitters carry signals to muscle cells to stimulate contraction.

Applying Your Knowledge Which one is responsible for A.Transmission of a nerve impulse across a synapse? B.Depolarization of a neuron’s membrane? C.Transmission of a nerve impulse along an axon? D.Repolarization of a neuron’s membrane? 1.Potassium Ions (K+) 2.Neurotransmitters 3.Sodium Ions (Na+)

Types of Neurons Receives information from environment Generates a response Carries signal between sensory and motor neurons

Pain-Withdrawal Reflex 1.Pain receptor stimulated 2.Signal transmitted by sensory neuron 4.Motor neuron stimulates muscle 3.Signal transmitted within spinal cord 5.Effector causes withdrawal

Nervous System Organization Central Nervous System Peripheral Nervous System Brain Spinal Cord Motor Neurons Sensory Neurons Sympathetic Division (stress or activity) Parasympathetic Division (maintenance) Somatic Nervous System (voluntary) Autonomic Nervous System (involuntary)

The Autonomic Nervous System

The Human Brain Cerebral Cortex: movement, senses, thinking Cerebellum Pons Medulla Spinal Cord Pineal Gland Thalamus Corpus Callosum Skull Meninges Hypothalamus Pituitary muscle coordination breathing, heart rate, blood pressure

The Cerebral Cortex Frontal Lobe Higher Intellectual Functions Primary Motor Area Premotor Area Speech Motor Area leg trunk arm hand face tongue Parietal Lobe Primary Sensory Area Sensory Association Area Occipital Lobe Primary Visual Area Visual Association Area Temporal Lobe Memory Primary Auditory Area Language Comprehension & Formation

Limbic System and Thalamus Cerebral Cortex Thalamus HypothalamusAmygdala Hippocampus relay center emotions, drives, behaviors

Maintaining Homeostasis Negative Feedback: A change that initiates a series of events to counteract the change and restore the original state Negative Feedback: A change that initiates a series of events to counteract the change and restore the original state

Applying Your Knowledge Which one A.Is responsible for increasing breathing rate when you start running? B.Includes the spinal cord? C.Controls muscle movement? 1.Central Nervous System 2.Somatic Nervous System 3.Autonomic Nervous System