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ANSC*2340 Nervous System
sympathetic, parasympathetic, autonomic, neurons, synaptic transmission
53
Anatomy
Undergraduate 2
03/06/2014

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Term
What are the functions of the nervous system (5)?
Definition
-sensory
-integration
-motor functions
-regulate glandular secretions
-maintain appropriate state of consciouness
Term
What is required for the nervous system to function?
Definition
rapid transmission of information from one site in the body to another by electrochemical impulse
Term
What are the two main classes of cells in the nervous system?
Definition
neuroglial (glial) cells
neurons
Term
How does myelin affect information transfer?
Definition
speeds of propagation of the electrical impulse
Term
Which class of cells is involved in transmission of information/impulses?
Definition
neurons
Term
What are the functions of neuroglial cells? (6)
Definition
-form myelin (sheath around axon)
-provide nutrients & oxygen
-anchor neurons
-destroy pathogens
-remove dead neurons
-protect nervous system
Term
What is the function of neurons?
Definition
-develop & propagate action potentials to carry information throughout the CNS
-
Term
From where do cardiac cells gain their action potential?
Definition
they can generate their own AP
Term
What is the term for the central body of the neuron?
Definition
soma / perikaryon
Term
What are dendrites?
Definition
-multibranched projections from the soma
-receive impulses from other neurons & transmit the info to the soma
Term
What are axons?
Definition
-single unbranched projections from the soma
-conducts impulse from the soma to another neuron or cell
Term
What is the length of an axon?
Definition
ranges from less than 1mm to greater than 1m
Term
How many axons project from each neuron?
Definition
1
Term
Which contains a high proportion of myelinated axons, white matter or grey matter?
Definition
white matter
Term
What is the term for specialized glial cells found inside the brain & spinal cord?
Definition
oligodendrocytes
Term
What is the term for specialized glial cells found outside the brain & spinal cord?
Definition
schwann cells
Term
What is the term for the gaps found between adjacent glial cells?
Definition
nodes of Ranvier
Term
Is the speed of transmission greater for myelinated or unmyelinated cells?
Definition
myelinated
Term
What is the function of the nodes of Ranvier?
Definition
work with myelin sheaths to speed up transmission of impulses
Term
What axis/regions of the body is the central nervous system concerned with?
Definition
-brain & spinal cord
-central (cranial-caudal) axis of the body
Term
What PNS nerves originate from the brain? The spinal cord?
Definition
cranial nerves
spinal nerves
Term
What type of nerves are afferent nerves, and in which direction to they carry information?
Definition
sensory nerves (information from sensory receptors)
carry impulses towards CNS
Term
What type of nerves are efferent nerves, and in which direction to they carry information?
Definition
motor nerves (cause skeletal contractions)
carry impulses away from CNS
Term
Is somatic NS function voluntary or involuntary?
Definition
voluntary
Term
True or False

Impulses controlled by the ANS travel to skeletal muscle
Definition
False
Involuntary nerve function is found in smooth muscle, cardiac muscle, endocrine glands etc.
Term
What are some functions of the Autonomic Nervous System?
Definition
-contract intestines
-increase heart rate in response to threat
-stimulate secretion of digestive juices
Term
Describe the polarization of a resting neuron
Definition
-Na/K pump transports Na+ outside the cell, and K+ inside against [%] gradient
-generates a difference in electrical charge across the membrane
Term
What is the resting membrane potential?
Definition
-70mV
Term
Does an unstimulated neuron have a greater [K+] on the inside or outside of the membrane?
Definition
inside
Term
Describe what happens when a neuron receives an impulse from an adjoining neuron
Definition
-Na channels in the membrane open
-Na+ passively diffuse to the inside of the cell
-RMP becomes positive
-Na channels close, K+ channels open
-K+ flows out of cell
Term
Why do Na+ ions diffuse into the cell passively once the sodium channels are opened?
Definition
-travel down a concentration gradient
-resting mmb potential is -70mV inside the cell, Na+ are attracted to it
Term
An neuron's action potential is...
Definition
the change in electrical charge aacross the membrane from negative to positive
Term
What is depolarization?
Definition
opening of Na channels and influx of Na into the neuron cell
Term
Why do K+ ions travel outside of the neuron cell after the potassium channels have opened?
Definition
-inflow of Na+ creates positive charge
-like charges repel, K+ moves out
Term
What is repolarization?
Definition
opening of potassium channels and outflow of K+ from the neuron cell
Term
Describe the concentration of K and Na between the end of repolarization and the establishment of RMP
Definition
high K outside, high Na inside
Term
True or False

The 'strength' of depolarization depends on the strength of the stimulus received
Definition
False

As long as the stimulus is above the threshold minimum, depolarization will occur, always at 'maximum strength'
Term
What is the refractory period?
Definition
-when a 2nd stimulus arrive at the time Na channels or K channels are open ("in action") the neuron is insensitive to this new stimulus
Term
What is an absolute refractory period, when does it occur?
Definition
no depolarization under any circumstances
-during Na influx or early stages of K outflow
Term
What is a relative refractory period, when does it occur?
Definition
we see depolarization
-occurs if a larger than normal stimulus arrives at the tail end of repolarization
Term
What is saltatory conduction?
Definition
-myelin sheath prevents flow of Na+ across the membrane, depolarization is limited to the Nodes of Ranvier, skipping from one node to another
-speeds up conduction of the action potential along the neuron
Term
What causes Multiple Sclerosis?
Definition
damage to the myelin sheath, slows rate of conduction and results in loss of normal muscle control
Term
How does an AP travel to the next neuron/target cells after it has traveled the length of an entire axon?
Definition
synaptic transmission
Term
Describe synaptic transmission
Definition
-AP reaches presynaptic neuron
-at presynaptic knob, Ca2+ channels open
-Ca2+ flows in, neurotransmitter fuses with cell membrane
-synaptic cleft secretes neurotransmitter
-postsynaptic neuron receives neurotransmitter via diffusion
Term
What is a synapse?
Definition
junction between a neuron and another neuron, or a neuron and a target cell
Term
What is a the physical gap between a neuron and a receptor cell?
Definition
synaptic cleft
Term
What is a presynaptic neuron?
Definition
the neuron that brings the AP to the synapse & releases a neurotransmitter
Term
What is a postsynaptic neuron?
Definition
the neuron that receives the neurotransmitter from the synapse
Term
What is the knob at the end of the presynaptic neuron?
Definition
presynaptic knob
Term
What is the function of a neurotransmitter
Definition
to stimulate depolarization of the membrane across a synaptic cleft
Term
True or False

Membranes on the postsynaptic neuron bind to all forms of neurotransmitters
Definition
False

They usually bind a specific neurotransmitter
Term
[image]
Definition
[image]
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