Bio 201 – Human Anatomy and Physiology 1 Chapter 10

Flashcards about the nervous system

Functions of the Nervous System

Master regulatory system, Sends and receives information, Sensory input, Integration and processing, Motor output, Maintains homeostasis, Act as center for thought, learning, and memory

Neurons (nerve cells)

Respond quickly to changes/stimuli and Conduct electrical impulses via neurotransmitters

Neuroglia

Protect, support, insulate, and nourish neurons, Do not conduct electrical impulses like neurons

Central Nervous System (CNS)

Brain and spinal cord

Peripheral Nervous System (PNS)

Cranial and spinal nerves; Connects CNS to other parts of body

Sensory Division

Sensory receptors perform sensory function (detect changes); Receptors convert information into impulses; Impulses conducted along peripheral nerves to CNS for integration

Motor Division

Neurons that transmit impulses from CNS to effectors → perform motor functions; Effectors are muscles or glands outside nervous system

Somatic Nervous System

Transmits voluntary commands to skeletal muscles

Autonomic Nervous System

Transmits involuntary commands to viscera

Signs and symptoms of Migraines

Pounding head, nausea, aura (shimmering images in visual field), light or sound sensitivity

Environmental Triggers of Migraines

Bright light, certain foods, lack of sleep, stress, high altitude, stormy weather, excess caffeine or alcohol

Triptans

Drugs that may stop migraine attack

Treatments to lower frequency of chronic migraine attacks

Drugs that bind a neurotransmitter that causes dilation and inflammation of blood vessels associated with migraine, Antidepressants, anticonvulsants, high blood pressure drugs

Cell body (soma or perikaryon)

Contains nucleus, cytoplasm, organelles, neurofilaments, chromatophilic substance (Nissl bodies)

Dendrites

Branched receptive surfaces

Axon

Transmits impulses and releases neurotransmitters to another neuron or effector

Axon hillock

Cone-shaped area of cell body from which axon arises

Collaterals

Branches from axon

Axon terminal

Specialized endings of extensions form axon

Synaptic knob

Rounded ending of a synaptic terminal

Schwann Cells

Neuroglia of the PSN that wrap around some axons in layers

Myelin

Mixture of fats and proteins that fill layers made by Schwann cell membranes

Myelin sheath

A wrapped coating around some PNS axons, composed of layers of Schwann cell membranes and myelin, acts as electrical insulator

Nodes of Ranvier

Gaps in myelin sheath between Schwann cells

Myelinated axons

Coated by myelin sheath; Increase conduction speed for electrical impulses

Unmyelinated axons

Encased by Schwann cell cytoplasm in PNS, no wrapped coating of myelin around axons

Multiple Sclerosis

destruction of myelin sheaths in CNS by an immune response

Multipolar Neurons

Many processes extend from cell body (many dendrites, 1 axon); Most neurons of CNS, some in autonomic nervous system (99% of all neurons)

Bipolar Neurons

Two processes extend from cell body (1 dendrite, 1 axon); Not that common; Found in sensory structures (eyes, ears, nose)

Unipolar (Pseudounipolar) Neurons

One process that extends from cell body; Two branches that function as 1 axon (peripheral and central processes); Cell bodies are mainly found in ganglia of PNS

Sensory (afferent) Neurons

Carry impulses from periphery to CNS (brain or spinal cord)

Interneuron (association or internuncial)

Link neurons in CNS; Relay information from one part of CNS to another

Motor (efferent) Neurons

Carry impulses from CNS to effectors (muscle or glands)

Astrocytes

Connect neurons to blood vessels, exchanging nutrients and growth factors; Form scar tissue; Aid metabolism of certain substances; Regulate ion concentrations (such as K+); Part of blood brain barrier

Oligodendrocytes

Myelinate CNS axons; Provide structural support

Microglia

Phagocytic cells; Provide structural support

Ependyma or ependymal cells

Line central anal of spinal cord and ventricles of brain; Cover choroid plexuses; Help regulate composition of cerebrospinal fluid; Ciliated cuboidal or columnar cells

Schwann cells

Produce myelin sheath found on some peripheral axons; Speed up nerve impulse transmission

Satellite cells

Support clusters of neuron cell bodies (ganglia); Nourish and balance ionic concentrations

Membrane potential

Charge inside a cell

Resting membrane potential

Charge inside cell when it is inactive; About -70 mV

Action Potential

Sequence of electrical events in an excitable cell, involving changes in membrane potential, first positive and then negative, to return to resting potential

Local potential change

Change in membrane potential that occurs only in the area of stimulation

Threshold stimulus

Excitatory stimulus that causes enough Na+ ions to flow into cell that it reaches the threshold potential of -55 mV

Depolarization

Change from negative to positive charge inside cell, making both sides of membrane positive

Repolarization

Return to resting potential after action potential; occurs as K+ channels open and K+ ions rush out of the cell → polarity returns

Hyperpolarization

Slight overshoot at end of repolarization, potential drops below -70 mV for a moment before returning to -70 mV

Absolute refractory period

Time when threshold stimulus cannot generate another action potential; Voltage-gated Na+ channels are briefly unresponsive

Relative refractory period

Time when only high-intensity stimulus can generate another action potential; Repolarization is not compete and membrane is re-establishing resting potential

Saltatory conduction

Action potentials jump from node to node down the axon

Synapse

Site at which neurons transmit a nerve impulse to another neuron

Synaptic Transmission

Process by which presynaptic neuron sends impulse to postsynaptic neuron

Synaptic potentials

Local potentials that result from changes in chemically gated ion channels

Excitatory postsynaptic potential (EPSP)

Membrane change in which neurotransmitter opens Na+ channels; Depolarizes membrane of postsynaptic neuron as Na+ enters axon; Action potential in postsynaptic neuron becomes more likely

Inhibitory postsynaptic potential (IPSP)

Membrane change in which neurotransmitter opens K+ channels (or Cl– channels); Hyperpolarizes membrane of postsynaptic neuron as K+ leaves axon; Action potential of postsynaptic neuron becomes less likely

Neuromodulators

Substances that alter a neurons response to a neurotransmitter or block the release of a neurotransmitter

Enkephalins and Beta endorphin

Relieve pain sensations

Substance P

Found in neurons that conduct pain impulses

Neuronal Pools

Groups of interneurons that make synaptic connections with each other; Located completely within the CNS

Facilitation

Repeated impulses on an excitatory presynaptic neuron may cause that neuron to release more neurotransmitter in response to a single impulse; Increases likelihood that postsynaptic cell will reach threshold

Convergence

One neuron receives input from several neurons

Divergence

One neuron sends impulses to several neurons via axonal branches

Antagonist

Drug that binds to receptor and blocks neurotransmitter binding

Agonist

Drug that activates receptor causing action potential or aiding in binding of neurotransmitter