Nervous Physiology Flashcards by belle perez

neurons enclosed within skull

Brain

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connects to brain and enclosed
within spinal cavity

Spinal cord

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bundles of many axons of neurons

Nerves

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(12 pairs) emerge from brain

Cranial nerves

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(31 pairs) emerge from spinal cord

Spinal nerves

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groups of neuron cell bodies located outside of brain and spinal cord

Ganglia

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networks in digestive tract

Enteric plexuses

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monitor changes in internal
or external environments

Sensory receptors

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Carry information into brain and spinal cord

Sensory receptors and sensory nerves

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information processing

Integration

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awareness of sensory input

Perception

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Analyzing and storing information to help lead to appropriate responses

Integration

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efferent nerves
signals to muscles and glands

motor activity

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Central Nervous System (CNS)

Brain and spinal cord

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Peripheral Nervous System (PNS)

Nerves
- Cranial Nerves
- Spinal Nerves
Ganglia
Enteric Plexuses
Sensory receptors

All nervous system structures outside of the CNS

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Can respond to stimuli and convert stimuli to electrical signals (nerve impulses) that travel along neurons

Neurons

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support, nourish and protect neurons

Neuroglia cells

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critical for homeostasis of interstitial fluid around neurons

Neuroglia

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nucleus, cytoplasm with typical organelles

Cell body

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highly branched structures that carry impulses to the cell body

Dendrites

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conducts away from cell body toward another neuron, muscle or gland

Axon

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Emerges at cone-shaped ________ hillock

axon

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contain synaptic vesicles
that can release neurotransmitters

Axon terminals

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Have several or many dendrites and one axon

Most common type in brain and spinal cord

Multipolar

(motoneuron)

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Have one dendrite and one axon

Bipolar (interneuron)

Have fused dendrite and axon

Unipolar (sensory)

convey impulses into CNS (brain or spinal cord)

Sensory (afferent)

Convey impulses from brain or spinal cord out through the PNS to effectors (muscles or glands)

Motor (efferent)

Most are within the CNS Transmit impulses between neurons

Interneurons (association neurons)

Cells smaller but much more numerous than neurons

Neuroglia

Can multiply and divide and fill in brain areas

Neuroglia

brain tumors derived from neuroglia

Gliomas

Do not conduct nerve impulses

Neuroglia

help form blood brain barrier

Astrocytes

produce myelin in CNS

Oligodendrocytes

protect CNS cells from disease

Microglia

form CSF in ventricles

Ependymal cells

produce myelin around PNS

schwann

help to regenerate PNS axons

schwann

support neurons in PNS ganglia

satellite cells

Axons covered with a myelin sheath

Myelination

gaps in the myelin important for rapid signal conduction

Nodes of Ranvier

diseases destroy myelin such as

Multiple sclerosis Tay-Sachs

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

primarily myelinated axons

White matter

cell bodies, dendrites, unmyelinated axons, axon terminals, neuroglia

Gray matter

white matter (tracts) surround centrally located gray matter “H” of “butterfly”

Spinal cord

gray matter in thin cortex surrounds white matter (tracts)

Brain

Axons and dendrite in the _______ can be repaired if cell body is intact and Schwann cells functional. These form a regeneration tube and grow axons or dendrites if scar tissue does not fill the tube

Regeneration of PNS neurons

Very limited even if cell body is intact inhibited by neuroglia and by lack of fetal growth- stimulators

Regeneration of CNS neurons

Peripheral nervous system (PNS) divisions

Somatic (SNS) Autonomic nervous systems (ANS) Enteric nervous system (ENS)

Sensory neurons from head, body wall, limbs, special sense organs voluntary

Somatic (SNS)

Sensory neurons from viscera involuntary

Autonomic

Autonomic nervous system subdivisions

Sympathetic Parasympathetic

fight-or-flight rest-and-digest

brain of the gut

Enteric nervous system (ENS)

Sensory neurons monitor chemical changes and stretching of GI wall involuntary

Enteric nervous system

nerve impulses

Action potential

Action potential requires

membrane potential ion channels

channels under ion channels

Leakage channels Gated channels

a charge difference across cell membrane (polarization)

membrane potential

allow ions to move by diffusion from high to low concentration

Ion channels

allow ions to leak through membrane; there are more for K+ than for Na+

Leakage channels

Open and close on command Respond to changes in membrane so can generate and conduct action potentials

Gated channels

Typically –70 mV

Resting Membrane Potential

T or F Resting Membrane Potential: Inside of membrane more negative than outside

True

Inside (more negative) because cytosol has

Many negative ions: amino acids and phosphates K+ that easily leaks out through many K+ channels

Outside (more positive) because interstitial fluid has

Few negative ions Na+ that does not leak out of cell: few Na+ channels Membrane “pumps” that quickly pump out Na+ that does leak (diffuse) into cell

Series of events that activate cell membrane in neuron or muscle fiber

Action Potential

Na+ channels open → as more Na+ enters cell, membrane potential rises and becomes positive (–70→0→+ 30 mv)

Depolarizing phase

K+ channels open→as more K+ leave cell, membrane potential is returned to resting value (+ 30→0→–70 mv)

Repolarizing phase

Typically depolarization and repolarization take place in about

1 millisecond (1/1000 sec)

- Levels of ions back to normal by action of Na+/K+ pump - Refractory period (brief): even with adequate stimulus, cell cannot be activated

Action Potential Recovery

If a stimulus is strong enough to cause depolarization to threshold level, the impulse will travel the entire length of the neuron at a constant and maximum strength.

Action Potential All-or-none principle

Each section triggers the next locally as even more Na+ channels are opened (like row of dominos)

Nerve impulse conduction (propagation)

In unmyelinated fibers; slower form of conduction

Continuous conduction

In myelinated fibers; faster as impulses “leap” between nodes of Ranvier

Saltatory conduction

Types of conduction

Continuous conduction Saltatory conduction

Factors that increase rate of conduction

Myelin, large diameter and warm nerve fibers

neuron-neuron

Synapse

neuron-muscle fiber

Neuromuscular junction

neuroglandular junction

neuron-gland

Components of synapse

Sending neuron Space between neurons Receiving neuron

presynaptic neuron (releases neurotransmitter)

Sending neuron

Receiving neuron

postsynaptic neuron

Space between neurons

synaptic cleft

T or F Action potential arrives at presynaptic neuron’s end bulb

Neurotransmitters: Acetylcholine (ACh): common in PNS

Stimulatory (on skeletal muscles) Inhibitory (on cardiac muscle)

Neurotransmitters: Amino acids

Glutamate, aspartate, gamma aminobutyric acid (GABA), glycine

Neurotransmitters: Modified amino acids

Norepinephrine (NE), dopamine (DA), serotonin

One-way transmission only because ❑ Only presynaptic cells release NT ❑ Only postsynaptic cells have receptors for NT binding

Synaptic Transmission

Opens voltage gated Ca2+ channels→Ca2+ flows into presynaptic cytosol Increased Ca2+ concentration→exocytosis of synaptic vesicles

Synaptic Transmission

serves as chemical trigger (stimulus) of ion channels

neurotransmitter

cell membrane may be depolarized or hyperpolarized

presynaptic membrane