Nervous System Function of the Nervous System Receive sensory - - PowerPoint PPT Presentation

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Nervous System Function of the Nervous System Receive sensory - - PowerPoint PPT Presentation

Jul 11, 2023 867 likes •1.33k views

Nervous System Function of the Nervous System Receive sensory information, interpret it, and send out appropriate commands to form a response Composed of neurons (functional unit of the nervous system) Nervous System Endocrine System

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Nervous System

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Function of the Nervous System

  • Receive sensory information, interpret it, and

send out appropriate commands to form a response

  • Composed of neurons (functional unit of the

nervous system)

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Nervous System Endocrine System

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Divisions of the Nervous System

  • Central Nervous System

(CNS) – processes, interprets and stores information, composed of the brain and spinal cord

  • Peripheral Nervous System

(PNS) – peripheral nerves that carry signals to and from the CNS

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Divisions of the Nervous System

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Structure of a Neuron

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Schwann Cells and Myelin

  • Schwann cells are supporting cells that

produce myelin (lipid insulator)

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Types of Neurons

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Three Types of Neurons

  • Sensory Neurons – Convey signals to the CNS

from sensory receptors

  • Interneurons – Located within the CNS,

integrate data and then relay signals to other neurons

  • Motor Neurons – Convey signals from the CNS

to effector cells

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Reflex Arc

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Reflex Arc (Neural Circuit)

Stimulus (External

  • r Internal)

Sensory Receptor Cell (5 Types) Interneuron (Brain and Spinal Cord) Motor Neuron (Efferent) Sensory Neuron (Afferent) Response (Behavior, Secretion) Effector (Muscle, Gland)

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The Synapse

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The Synapse

  • Site of communication between an axon (or

synaptic) terminal of one neuron and another cell

  • Transmission of information between neurons
  • ccurs across synapses
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Molecular Mechanism of Synaptic Function How Cone Snails Paralyze Fish When Cone Snails Attack

Watch the following three videos

  • n synaptic function:
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What do you already know about action potentials?

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Nerve Impulse Animation Watch the following video:

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Membrane Potential

  • Neurons, like most cells, have an electrical

charge difference (membrane potential)

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Resting Potential

  • At rest, the membrane potential is -70mV

(resting potential) - maintained by the Na+/K+ pump

  • At rest, the neuron is said to be “polarized”
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Threshold (“All or None”)

  • A neuron remains at rest until it receives a

stimulus strong enough for the membrane to reach a voltage of ~ -55 mV (threshold)

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Action Potential (Nerve Impulse)

  • An action potential is the rapid reversal of

electrical charge of the neuron membrane (depolarized)

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Steps of an Action Potential

  • 1. Stimulus causes Na+ gated ion channels to
  • pen and Na + rushes into the cell (initiation of

action potential and depolarization)

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Steps of an Action Potential

  • 2. As Na + gated channels close, K + gated

channels open allowing K + to rush out of the cell (repolarization)

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Steps of an Action Potential

  • 3. Na + /K + pump restores resting potential by

pumping Na + ions back out of the neuron and K + ions into the neuron (refractory period)

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How Nerves Work Animation Crossing the Divide: Neurotransmitters and the Synapse Watch the following two videos:

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Release of Neurotransmitters

  • As the action potential reaches the axon

terminal, it causes Ca2+ gated channels to

  • pen allowing Ca2+ ions to rush into the cell
  • Causes synaptic vesicles to fuse with the

membrane and release neurotransmitters into the synaptic cleft

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Release of Neurotransmitters

  • Neurotransmitters (ligand):

– bind to receptors on the postsynaptic cell – cause ion channels to open – Initiate an action potential by changing the membrane potential (depolarization

  • Esterases: enzymes that breaks down and

recycles neurotransmitters in the synaptic cleft

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Neurotransmitters

  • Chemical messengers that transmit nerve

impulses (or action potentials) across the synapse

  • Neurotransmitters can be stimulatory

(excitatory) or inhibitory

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Neurotransmitters Stimulatory Inhibitory

Acetylcholine Epinephrine GABA Serotonin

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Acetylcholine

  • Stimulatory neurotransmitter released at the

neuromuscular junction

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GABA

  • Inhibitory neurotransmitter released between

neurons

  • Motor control, vision, regulates anxiety
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A little bit more about the nervous system…..

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Evolution of Nervous Systems

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Brain Evolution in Vertebrates

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Vertebrate Brain

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