The Nervous System

The Nervous System - Notes Notes The Nervous The System...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Notes Notes The Nervous The System Chapter 35 Section 2 Notes Notes The Nervous The System Chapter 35 Section 2 Lecture Outline – The Nervous System PowerPoint Notes textbook questions Keys Keys Nervous System = Communication Nervous Function: Receives Stimuli Interprets information Causes a response -Controls and coordinates bodily functions -Responds to -Responds stimuli (inside or outside the body) What is the basic functional unit of the nervous system? the Neuron! What does the neuron do? Carries messages throughout the body How does it carry the messages? By conducting electrical signals What are these signals called? Nerve impulses! What does a neuron look like? What Neuron Anatomy Neuron Cell Body Three parts to a Three NEURON: NEURON: 1. Cell body: Large, central portion of the neuron where all organelle are located located What is its job? Interpret incoming Interpret signals signals Neuron Anatomy Neuron 2. Dendrites: 2. Dendrites Short, highly Short, branched fibers branched what is its job? Carries impulses Carries toward the cell body toward Referred to as the Referred afferent process afferent Dendrites Neuron Anatomy Neuron 3. Axon: 3. Axon Long, slightly branched fiber Long, What is its job? Carry impulses away from the cell body Referred to as the efferent process Neuron Anatomy Neuron Three parts of the Axon: A. Axon hillock: A. Axon = site of initiation of an action potential site (point where axon and cell body meet) (point B. Axon fiber: B. Axon = the main portion of the axon the C. Axon terminal: C. Axon = branched end of the axon branched = point of communication with other cells point The Axon The Axon Hillock fiber Axon Terminals Neuron Anatomy Neuron Additional Parts of a Neuron Structure of a Typical Neuron Dendrite Axon terminal Cell body Nodes of Ranvier Axon Nucleus Myelin sheath Neuron anatomy Neuron What do you remember? 1 dendrites 6 Myelin sheath 2 nucleus 3 Cell body 5 axon Nodes of Ranvier4 Direction of impulse Axon 7 terminals 3 Types of Neurons Types I. Sensory Neurons: Receive incoming stimuli Five types of sensory neurons: 1. 2. 3. 4. 5. Thermo-receptors Mechano-receptors Chemo-receptors Photo-receptors Pain-receptors Thermo-receptors Thermo-receptors Location: Skin Hypothalamus Body Core Function: Sensation of hot and Sensation cold cold Detects change in Detects body core temp. body Mechano-receptors Mechano-receptors Location: Skin Skeletal muscle Inner ear Function: Touch Pressure Muscle movement Motion Sound Chemo-receptors Chemo-receptors Location: Nose Tongue (taste buds) Blood vessels Function: Smell Taste Detects levels of CO2 in blood in Photo-receptors Photo-receptors Location: Eyes Function: Allow vision thru detection of light Pain-receptors Pain-receptors Location: Everywhere, except Everywhere, the brain the Function: Sensation of pain Detects chemicals Detects released by damaged cells cells Three Types of Neurons Three II. Motor Neurons: II. Motor Carry impulses to muscles and glands Cause a response to some stimuli III. Interneurons: III. Interneurons Connect sensory and motor neurons Allow for quick response (reflex action) Three types of neurons Three Neurons Neurons What is grey matter? Collective cell bodies and Collective dendrites of all neurons dendrites What is white matter? Myelinated nerve fibers Axons of all neurons Can be approximately one meter in length White matter Gray matter What is a Nerve? What Bundle of axons held together by held connective tissue. connective What color is a nerve? White! Why? Because axons Because are white matter and they compose and nerves How are nerves held together? How Connective tissue What is this connective What tissue called? tissue Neuroglial cells (nerve glue) Approximately half of the Approximately volume of the brain is composed of neuroglial cells of Most brain tumors develop in mesoglial Most cells – NOT neurons cells What do neuroglial cells do? What Support the axons Insulate the electrical impulses Like electrical tape insulates Like electric wires this prevents “leaking” electric of electric signals An example of a neuroglial cell An Schwann cell This wraps around the axon in multiple layers It is composed of a fatty material called… Myelin Regular breaks in the myelin sheath are called… Node of Ranvier Impulse speed Impulse Some neurons are fast, good conductors Some of impulses of Other neurons are slow, poor conductors Other of impulses of What distinguishes these two types? Diameter of the axon 2. Myelination Fastest axons have a large diameter and are Fastest myelinated. How much faster? myelinated. Up to 100 times faster! (Reflexes are this type) 1. The Nerve Impulse The How are messages (impulses) carried by the nervous system? As electrical and chemical As signals. signals. How does the impulse develop? Charged particles (ions) move Charged across the cell membrane across A neuron is ready to transmit an impulse when it neuron is in the resting state. is Resting membrane potential is -70 mV Resting Membrane Potential Resting The inside of the cell has The a negative charge as compared to the outside of the cell membrane. of How does this charge How difference develop? difference There are more Na+ (sodium) ions outside and fewer K+ (potassium) and ions inside. ions The Nerve Impulse The How does the impulse begin? The neuron is stimulated by another The neuron or by stimuli from the environment. neuron The Nerve Impulse The If the stimulus is If strong enough, it reaches threshold level. level. This stimulates an This impulse. impulse. If the stimulus is not If strong enough, no impulse occurs (all-orimpulse none principal) The Nerve Impulse The What happens if threshold is reached? An action potential (nerve impulse) begins What is an action potential? Rapid reversal of membrane potential in Rapid response to a stimulus response How does this happen? Sodium channels open allowing Na+ to flood into the cell. The membrane potential rises to +30 mV (rising The phase) as inside of cell becomes more positive phase) The Nerve Impulse The Please, please, tell us what happens next… When the membrane potential reaches +30 mV, When the sodium channels close. the Potassium channels open and K+ flows out of the cell. the This causes the membrane potential to become more potential negative again (falling phase). (falling The Nerve Impulse The Na+ channels close 2 K+ channels open, K+ begins to leave cell K+ leaves cell 0 Threshold of excitation Membrane potential (mV) +50 -70 1 Na+ channels open, Na+ enters cell K+ channels close 3 Excess K+ outside diffuses away The Nerve Impulse The The Nerve Impulse The Action potential -55 zatio n D ep olari 0 ation Repolariz Voltage (mV) +40 Failed initiations Threshold Resting state -70 Stimulus 0 1 Refractory period 2 3 Time (ms) 4 5 The Nerve Impulse The What happens when the action potential What passes down the axon? passes The resting potential is restored via the The sodium/potassium pump. sodium/potassium Now the membrane is ready to transmit Now another impulse. another K+ extracellular fluid Na+ ATP cytoplasm ADP The Nerve Impulse The An action potential only moves in one direction down the An axon. axon. From axon hillock, thru axon fiber to the axon terminal. The action potential is regenerated at each Node of The Ranvier down the length of the axon. Ranvier The Nerve Impulse The What happens when the impulse reaches the What axon terminal? axon It must pass thru the synapse. What is a synapse? It is the gap between two It neurons, or between a neuron neurons, and organ (effector). Why is there a gap? So the neurons don’t short each other out!! The Synapse The How do neurons pass the impulse across the How synapse? synapse? Using chemicals called neurotransmitters What do neurotransmitters do? Stimulate the dendrites of other neurons or Stimulate membranes of other cells. membranes If a dendrite is stimulated, it sends its message If to the cell body and the message is passed on to If a muscle or gland is stimulated, a reaction If occurs in that organ. occurs The Synapse The The Synapse The Model of the Synapse synaptic vesicles Axon of presynaptic cell Glycoprotein (ligands) neurotransmitters receptors for neurotransmitters synaptic cleft receptors for glycoprotein The Synapse The Neuron Smear: Identification: Note distinctive shape of neuron, with long Identification: processes (dendrites and/or axons, 5) extending out from main cell body. Features to Know: Features The large, irregularly shaped cell body (3) contains a The darker nucleus (2), which contains an even darker-staining nucleolus (1). There are also numerous supporting There glial cells, though only their small dark nuclei (4) are easily seen. Neuron Nerve Myelin sheath ...
View Full Document

This note was uploaded on 11/09/2011 for the course BIO 110 taught by Professor Harmon during the Winter '11 term at BYU.

Ask a homework question - tutors are online