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1 - Ch. 8


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Peri Ner. Sys.
The nervous system is subdivided into 2 groups:
Brain & spinal cord

receives & processes info from sensory organs and the viscera to determine the state of the external environment (sensory info) & int. envir. (visceral info).

integrates info & makes decisions on appropriate actions, then sends instructions to certain organs instructing them to perform appropriate actions.

site of learning memory, emotions, thoughts, language, & etc.
Peripheral Nervous system
consists of neurons that provide communication btwn the CNS and organs throughout the body.

somatic nervous system

autonomic nervous system
Effector organs
perform function in the response to commands from the neurons.

muscles or glands
A neuron capable of transmitting messages to an effector organ or receiving information from a sensory organ is said to ____________ that organ.
somatic nervous system
consists of motor neurons, which regulate skeletal muscle contractions.
autonomic nervous system
consists of neurons that regulate the function of int. organs and other structures (sweat glands or blood vessels) that are NOT under voluntary control.

subdivides into parasympathetic and sympathetic
enteric nervous system
consists of intricate network of neurons in the gastrointestinal tract that can function independently of the rest of the nervous system but communicates w/ the ANS.
functional unit
the neuron is the smallest unit of a tissue that can carry out the function of that tissue.
Are "excitable cells" that communicate by transmitting electrical impulses.
Excitable cells
cells capable of producing large, rapid electrical signals called action potentials.
action potentials
repid large changes in the membrane potentails during which the inside of the cell becomes positively charged relative to the outside.
Glial cells
constitute 90% of the cells in the nervous system, provide various types of support to the neurons, including and metabolic support.
neural processes
cell body
contains the cell nucleus and most of the cell's organelles

carries out most functions that other cells perform (protein syn. and cell metabolism)

mature neurons DO NOT undergo cell division.
undiffereniated cells
In a few areas of the adult brain new neurons can develop from ___________ _____.
A cytoplasmic process that extends from a neuron's cell body. Neurons typically have many dendrites, which are usually shorter and thicker than axons and highly branched.

receive signals from other neurons at the synapse.
At a _________, a presynaptic neuron releases a chemical messenger called a neurotransmitter that usually communicates with the dendrites or cell body of a postsynaptic neuron or other cell.
nerve fiber

job is to send info

cell only has 1, but these branch and send signals to more than 1 destination.
branches of axon are called ___________

branching varies with every cell and depends on the amount of communication with other cells.
job is to receive info
axon hillock
axon originates here from the cell body

initiation of action potentials in most neurons
axon terminal
distal end of the axon

specialize in the release of the neurotransmitter upon arrival of action potential.

released neurotransmitter molecules carry a signal to a postsynaptic cell, usually to a dendrite or the cell body of another neuron or to the cells of an effector organ.
Leak channels
nongated channel

found ini the plasma membrane throughout the neuron

always open and are responsible for the resting membrane potential.
Ligand-gated channels
open or close in response to the binding of a chemical messenger to a specific receptor in the plasma membrane.

located in dendrites and cell body

receive comm. from presynaptic neurons in the form of neurotransmitters.
Voltage-gated channels
open or close in response to changes in membrane potential.

can be K+ channels and sodium channels, these are found in the axon and axon hillock.

necessary for initiation and propagation of action potentials.

Ca++ channels are found in axon terminals; open in response to the arrival of an action potential at the axon terminals. When open travels through the cytosol of the axon terminals and triggers the release of neurotransmitters.
Voltage-gated Ca++ channels
are found in axon terminals

open in response to the arrival of an action potential at the axon terminals.

When open travels through the cytosol of the axon terminals and triggers the release of neurotransmitters.
Bipolar neurons
generally sensory neurons w/ 2 projections: axon and a dendrite coming off the cell body.

function in smell and vision

subclass called pseudo-unipolar neurons
pseudo-unipolar neurons
located outside the CNS in a ganglion
peripheral axon
The dendrite is called _________ _____, because it originates in the periphery w/sensory receptors & function as an axon in that it transmits action potentials.
central axon
The axon process is called the ________ _____ because it ends in the CNS, where it forms a synapse w/ other neurons.
Multipolar neurons
the most common neuron

have multiple projections from the cell body

1 is an axon

the others are dendrites.
Efferent neurons
transmit info from the CNS to effector organs

include motor neurons extending to skeletal muscle and neurons of the ANS.

the axon leaves the CNS and becomes part of the peripheral nervous system as it travels to the effector organ it innervates.
efferent neurons
afferent neurons
What are the 3 types of functional classifications of neurons?
Afferent neurons
transmit either sensory info from sensory receptors or visceral receptors to the CNS for further processing.

most are pseudo-unipolar neurons

the endings of peripheral axons are located peripheral organs (sensory or visceral), where they are modified into sensory receptors or receive comm. from separate sensory receptor cells.

central axon terminates in the CNS, where it releases a neurotransmitter to comm. w/ other neurons.
99% of neurons in the body

Located in CNS

perform all the functions of the CNS, including processing sensory info from afferent neurons, sending out commands to effector organs through efferent neurons, and carrying out complex function of the brain such as thought, memory, and emotions.
Neurons are aligned in such a way that cell bodies and dendrites of _________ cells tend to be grouped together, and axons of _________ cells tend to be grouped together.
pathways, tracts, or commisures
In the CNS, cell bodies of neurons are often grouped into _______, and the axons travel together in bundles called _________, _______, OR ___________.

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