1/26: Nervous System Overview & Action Potentials Flashcards by Anita Maxwynn

What is one of the two major control systems of the body mediating systemic homeostatic processes?

Nervous system

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What does the nervous system do?

Muscle contraction
Integration of blood oxygen, carbon dioxide, and pH levels via respiratory activity
Regulation of volumes and pressures in the circulation via cardiovascular and urinary function
Digestive system motility and secretion

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What does the NS work along with to maintain systemic homeostasis?

Endocrine system

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What system is a quick fix to homeostatic disturbances?

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What system is a slower long-term maintenance?

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What is the functional unit in the NS?

Neurons

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What are neuroglia?

Support cells for neurons

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The NS uses a combination of ______ and ________ signals to communicate information around the body

Chemical; electrical

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What are receptors in the NS?

Special sensory receptors (sensations of smell, taste, vision, balance, and hearing)
Visceral sensory receptors (monitor internal organs, including those of cardiovascular, respiratory, digestive, urinary, and reproductive systems)
Somatic sensory receptors (monitor skeletal muscles, joints, skin surface; provide position sense and touch, pressure, pain, and temperature sensations)

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What makes up the afferent division of the NS?

Central nervous system (brain and spinal cord)

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What makes up the efferent division of the NS?

Peripheral nervous system

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What can the peripheral NS be further divided into?

Somatic and autonomic nervous system

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What can autonomic be further divided into?

Parasympathetic and sympathetic divisions

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What does the somatic nervous system control?

Skeletal muscle

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What does the parasympathetic and sympethetic division control?

smooth muscle
cardiac muscle
glands

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What are the two types of effector responses in the NS?

Local
Systemic

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What are the three main parts of a neuron?

Dendrites (info enters)
Cell body
Axon (info exits)

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What is the function of the axon hillock?

First portion of the axon

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What are Nissl bodies?

In the cell body (clusters of ribosomes) produce protein and causes cell body to appear gray

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Many neurons have axons that are ________

Myelinated

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________ are formed by neuroglia cells

Internodes

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What are oligodendrocytes?

Form myelin for axons in CNS

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What are schwann cells?

Form myelin for axons in PNS

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Inernodes are separated by small segments of axon not covered in myelin which is known as ________

Nodes of ranvier

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What is the function of the myelin covering?

Speed up the rate of nerve impulse conduction (saltatory conduction)

What are bipolar neurons?

Central cell body with dendrites on one side and axon on the other

What is a pseudounipolar neuron?

Dendrites are continuous with axon Cell body is pushed to one side

What is a multipolar neuron?

Multiple dendrites attached to the cell body

What are the three types of neurons?

1. Sensory neurons 2. Motor nuerons 3. Interneurons

What are the structure of sensory neurons?

Pseudounipolar neurons, bipolar

What is the relation of sensory neurons with the PNS?

Afferent division of PNS Dendrites/cell body in PNS

What is the relation of sensory neurons to the CNS?

Carry sensory information from reflex receptor to CNS Axons typically myelinated and extend into CNS

What is the structure of motor neurons?

Multipolar neurons

What is the relation of motor neurons with the PNS?

Efferent PNS Axons typically myelinated, extend into PNS and synapse with effectors

What is the relation of motor neurons with the CNS?

Carry moto commands from CNS to EFFECTORS Dendrites/cell body in CNS

What is the structure of interneurons?

Multipolar, anaxonic

Where are interneurons found?

Only in the CNS

What is the function of interneurons?

Carry information from one neuron to another Integration

Are interneurons myelinated?

May or may not be

What are the two types of electrical signals in neurons?

1. Action potentials 2. Graded potentials

What is the strength and size of an action potential?

Always the same (depolarization followed by repolarization) with no change in strength or size as they travel along the membane

Is an action potential all or none?

Yes

What are action potentials triggerd by?

At axon hillock when threshold potential is reached (Vm at which AP triggered; typically around -50mV)

Where does an action potential propogate?

Along cell membrane of axon from axon hillock toward axon terminal

What is the speed of an action potential?

Relatively fast changes in membrane potential

What is a graded potential?

Small changes in membrane potential of variable strength/amplitude

Where do graded potential travel?

A short distance along membrane and lose strength as they travel

What is the duration of graded potentials compared to action potentials?

Longer than APs

What are examples of graded potentials?

EPSPs and IPSPs Receptor potentials, end plate potentials

What are EPSPs?

Excitatory postsynaptic potentials (depolarizations); moves Vm towards threshold potential; increases likelihood of AP

What are IPSPs?

Inhibitory postsynaptic potentials (hyperpolarizations); moves Vm away from threshold; decreases likelihood of AP

What are receptor potentials?

Reflex receptors; excitatory

What are end plate potentials?

Skeletal muscles; excitatory

What is depolarization?

Vm becomes more positive (less negative) (EPSPs) *1 on the chart

What is repolarization?

Vm returns to resting value *2 on the chart

What is hyperpolarization?

Vm becomes more negative than resting (IPSPs)

Which ion channels if opened, cause an EPSP?

Increase Na+ in, increase Ca+ in

Which ion channels if opened cause an IPSP?

Increase K+ out, increase Cl- in

What is happening at A, B, and C?

A. Resting membrane potential B. EPSP depolarizes membrane C. EPSP reaches threshold and causes voltage-gated Na+ channel to open - transition from graded potential to action potential (axon hillock)

What is happening at D and E?

D. Depolarization; Na+ moves into the cell through open voltage gated Na+ channe;s (activated via positive feedback) E. VG Na+ channels close and slow voltage-gated K+ channels open

What is happening at F, G, H, and A?

F. repolarization; K+ moves outside of the cell through open VG K+ channels G. Hyperpolarization; VG K+ channels still open H. Voltage gated K+ channels close A. Resting membrane potential

What are the two gates that facilitate the Na+ channel?

1. Activation gate 2. Inactivation gate

What is the activation gate?

Closed at resting Vm, quickly opens at threshold depolarization

What is the inactivation gate?

Open at resting Vm, slowly closes at threshold depolarization

What is resting mV for the voltage-gated Na+ channel?

-70mV