Chapter 1 Flashcards by Chris Weber

Structures that make up the Central Nervous System

Brain
Spinal Cord

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How many neurons does the brain have?

100 Billion

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How many neurons does the spinal cord have?

100 Million

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Number of cranial nerves

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Number of spinal nerves

31 pairs

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Specialized cells that monitor change in the internal and external enviroment

Sensory Receptors

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Small masses of nervous tissue consisting of neuronal cell bodies that are located outside the brain and spinal cord

Ganglia

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Extensive network of nerves that are located in the walls of the GI tract that help regulate the digestion system

Enteric Plexus

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Name the tasks that the Nervous System carries out

Smell
Touch
Temperature
Speech
Memory
Body movement
Operation of the internal organs

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Three basic functions of the Nervous System

Sensory Function
Integrative Function
Motor Function

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Detect internal and external stimuli and carry information into brain and spinal cord via cranial and spinal nerves

Sensory function afferent

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The ‘Information Processing’. Consist of Perception and Analyzing/Storing information to help lead to appropriate responses

Integrative Function

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Once integration occurs the brain may elicit motor response to muscles or glands (effectors) via cranial and spinal nerves

Motor Function (Efferent)

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Two cells that nervous tissue consists of

Neurons and Neuroglia

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Provide most of the unique functions of the nervous system

Neurons

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Function is to provide support, nourishment, and protection

Neuroglia

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The parts of a Neuron

Cell Body

Dendrites

Axon

Axon Terminals

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Highly branched structures that carry impulses to the cell body

Dendrites

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Conducts away from the cell body toward another neuron, muscle, or gland

Axon

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Contain synaptic vesicles that can release neurotransmitters

Axon Terminals

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Structure Class:

Have several or many dendrites and one axon

Most common type in brain and spinal

Multipolar

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Structure Class:

One Dendrite and one axon

Found in the retina of eye and inner ear

Bipolar

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Structure Class:

Fused dendrite and axon

Sensory neurons of spinal nerves

Unipolar

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Functional Classes of Neurons

Sensory

Motor

Interneurons

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Convey impulses into CNS

Sensory

Convey impulses from brain or spinal cord out through the PNS to effectors (Muscles or Glands)

Motor

Located within the CNS Transmit impulses between neurons, such as between sensory and motor neurons

Interneurons (association neurons)

Support, nourish, and protect neurons Critical for homeostasis of interstitial fluid and neurons _Cells smaller but much more numerous than neurons_ **Make up half the volume of the CNS**

Neuroglia

Functions of Neuroglia

1. Do NOT generate or conduct nerve impulses 2. Support, nourish and protect neurons 3. In case of injury or disease, neuroglia can multiply to fill in space formerly occupied by neurons

Neuroglia that forms the blood brain barrier

Astrocytes

Neuroglia that produce myelin in CNS

Oligodendrocytes

Neuroglia that protects CNS cells from disease

Microglia

Neuroglia that forms CSF in ventricles

Ependymal cells

Neuroglia that produce myelin around PNS neurons

Schwann cells

Neuroglia that produces myelin around PNS neurons

Schwann cells

Neuroglia that supports neurons in the PNS ganglia

Satellite cells

Insulates the axon and speeds up the nerve impulse

Myelin

Gaps in myelin along the axon

Nodes of Ranvier

Diseases that destroy myelin sheaths

* Multiple Sclerosis * Tay-Sachs

What increases from birth to maturity?

Myelin

Cluster of cell bodies in PNS

Ganglion

Cluster of cell bodies in CNS

Nucleus

Bundle of axons in PNS

Nerve

Bundle of axons in CNS

Tract

White matter mostly consists of what?

Myelinated axons

What makes up Gray Matter?

1. Cell Bodies 2. Dendrites 3. Unmyelinated Axons 4. Axon Terminals 5. Neuroglia

Locations of gray and white matter in the Spinal Cord

White matter surrounds centrally located gray matter “H” or “Butterfly”

Location of gray and white matter in the Brain

Gray matter in a thin cortex surrounds white matter (tracts)

When can an axon and dendrite in the PNS be repaired?

Cell body is intact & Schwann cells are functional

Regeneration of CNS neurons

VERY limited even if the cell body is intact Inhibited by neuroglia and by lack of fetal growth-stimulator cues

What allows communication between neurons?

Action potentials (nerve impulses)

What are the requirements for Action Potentials?

1. Resting Membrane Potential 2. Ion Channels

A charge difference across cell membrane (polarization)

Resting Membrane Potential

Allows ions to move by diffusion from high to low concentration

Ion Channels

What allows ions to open and close on command

Gate Channels

Triggers resting membrane to become more permeable to Na+ Causes enough Na+ to enter the cell to reach -55 mv (from -70 mv) If threshold is reached, an action happens

Initial Event (STIMULUS)

Voltage gated Na+ channels open - More Na+ enters Membrane rises and becomes positive (+30)

Depolarizing Phase

Voltage gated K+ channels open - as more K+ leave cell, membrane potential is returned to resting value (+30 to 0 back down to -70 mv)

Repolarizing Phase

What is it called when nerve impulses travel from where they arise (axon hillock), along the axon on the axon terminal?

Propagation

Unmyelinated axons, currents flow across adjacent portions of the plasma membrane

Continuous conduction

In myelinated axons, Nodes of Ranvier allow impulses to “leap” from a node to the next

Saltatory Conduction

Allows neurons to communicate with other neurons or effectors

Synapses

Synaptic transmission is triggered by what?

Action Potential (Nerve Impulse)

Components of Synapse

1. Presynaptic neuron 2. Synaptic cleft 3. Postsynaptic neuron

Sending neuron, releases neurotransmitter

Presynaptic neuron

Space between neurons

Synaptic cleft

Receiving neuron, has receptors that bind to neurotransmitter

Postsynaptic neuron

Action potentials can only travel in one direction from dendrite to axon

One-way transmission

Action potential arrives at presynaptic neuron's end bulk Opens voltage Gated Ca2+ channels Ca2+ flows in presynaptic cytosol Increased Ca2+ concentration causes exocytosis of synaptic vesicles Neurotransmitter (NT) released into cleft NT diffuse across cleft and bind to receptors on the postsynaptic cell membrane NT acts as chemical trigger, opening ion channels which changes the voltage across the postsynaptic cell membrane Postsynaptic cell membrane may be depolarized or hyperpolarized, depending on which ions were admitted If threshold reached (-55 mv) then postsynaptic AP results and nerve impulse is triggered

Synaptic Transmission

How is a NT removed from a cleft?

1. Diffusion 2. Destruction by enzymes 3. Transport back into presynaptic cell (recycling)

Acetylcholine, Amino Acids, Modified Amino Acids, Neuropeptides, and Nitric Oxide

Neurotransmitters

Parasympathetic nervous system uses what neurotransmitter?

Acetylcholine (Ach)

Stimulatory Acetylcholine are found where?

Skeletal Muscles

Inhibitory Acetylcholine are found where?

Cardiac muscle

1. Glutamate 2. Aspartate 3. Gamma Aminobutyric Acid (GABA) Are examples of what?

Amino Acids

1. Norepinephrine (NE) 2. Dopamine (DA) 3. Serotonin

Modified Amino Acids

What nervous system provides thoughts, emotions, and memories?

CNS

Cranial nerves and spinal nerves are a part of what nervous system?

PNS

ALL nervous tissue outside the central nervous system (Brain and Spinal Cord)

Peripheral Nervous System

Subdivisions of the PNS

1. Somatic Nervous System (SNS) 2. Autonomic Nervous System (ANS) 3. Enteric Nervous System (ENS)

Sensory: Convey info from head, body wall, and limbs and from receptors for special senses (vision, hearing, taste, smell) to CNS Motor: Conduct impulses from CNS to skeletal muscles (voluntary control)

Somatic Nervous System

Sensory: Convey information from receptors in visceral organs (stomach and lungs) to CNS Motor: Conduct impulses from CNS to smooth muscles, cardiac muscles, and glands (involuntary control)

Autonomic Nervous System

“Fight or fight”

Sympathetic (ANS)

"Rest and Digest"

Parasympathetic (ANS)

Brain of the Gut

Enteric Nervous System

Sensory: Monitor chemical changes in GI tract, stretching of walls Motor: Regulate contractions, acid secretion, endocrine cell secretions Involuntary Control

Enteric Nervous System

Chapter 1 Flashcards

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