Integrating center for homeostasis, movement and almost all other body functions.
How does the Nervous System function as sensation?
Monitors changes/events occurring in and outside the body. Such changes are known as stimuli and the cells that monitor them are receptors.
How does the Nervous System function as integration?
The parallel processing and interpretation of sensory information to determine the appropriate response
How does the Nervous System function as reaction?
The activation of muscles or glands (typically via the release of neurotransmitters)
What kind of response does the Nervous System have?
The NS is a fast-acting system whose effects do not always work and are transient
What are the two big initial divisions of the Nervous System?
Central NS and Peripheral NS
What makes up the Central Nervous System and what are their functions?
The brain and spinal cord. It is the center of integration and control
What are the parts of the Peripheral Nervous System and what are their functions?
31 spinal nerves (carry info to and from the spinal cord) and 12 cranial nerves (carry info to and from the brain)
What are the two divisions of the Peripheral Nervous System?
Sensory and Motor
What is the function of sensory neurons?
Afferent division. Conducts impulses from receptors to the CNS. Informs the CNS of the state of the body interior and exterior. Made up of sensory nerve fibers.
What is the function of motor neurons?
Efferent division. Conducts impulses from CNS to effectors (muscles/glands). Made up of motor nerve fibers.
What is the function of Interneurons?
They lie within the brain and spinal cord. They form links with other neurons and relay information from one part of the brain or spinal cord to another.
What are the two sub-divisions of the motor division?
Somatic NS and Autonomic NS
What is the Somatic Nervous System and its function?
VOLUNTARY (generally) Somatic nerve fibers that conduct impulses from the CNS to skeletal muscles
What is the Autonomic Nervous System?
INVOLUNTARY (generally) Conducts impulses from the CNS to smooth muscle, cardiac muscle and glands
What are the two divisions of the Autonomic Nervous System?
Sympathetic NS and Parasympathetic NS. They are antagonistic and balancing both systems keeps us in a state of dynamic balance.
What is the Sympathetic Nervous System?
"Fight or Flight"
What is the Parasympathetic Nervous System?
"Rest and Digest"
What is Nervous Tissue made of?
Highly cellular. Two cell types are neurons (functional, signal conducting cells) and Neuroglia (supporting)
What are the four types of neuroglia found in the CNS?
Astrocytes, Microglia, ependymal cells and oligodendrocytes
What are Astrocytes and their fuctions?
Found in the CNS, star shaped, guide the migration of developing neurons. Act as K+ and NT buffers, involved in the formation of the blood brain barrier, function in nutrient transfer
What are Microglia and their functions?
Found in the CNS, specialized immune cells that act as the macrophages of the CNS.
What are Ependymal Cells and their functions?
Low columnar epithelial-esque cells that line the ventricles of the brain and the central canal of the spinal cord. Some are ciliated which facilitates movement of cerebrospinal fluid
What are Oligodendrocytes and their functions?
Produce the myelin sheath which provides the electrical insulation for certain neurons in the CNS.
What are the two types of glia in the PNS?
Satellite Cells and Schwann Cells
What are Satellite Cells and their functions?
Surround clusters of neuronal cell bodies in the PNS. Function unknown
What are Schwann Cells and their functions?
Form myelin sheath around the larger nerve fibers in the PNS. Vital to neuronal regeneration.
What are Neurons?
The functional and structural unit of the NS. Specialized to conduct info from one part of the body to another. Many, many different types but most have structural and funtional similarities.
What are the part of a Neuron?
Cell body (Soma), slender processes (axons/dendrites), an input region (dendrites/soma), a conducting component (axon), a secretory region (axon terminal)
What is a Nissl Body?
The very active/developed Rough ER of a neuron
What are clusters of cell bodies in the CNS known as?
What are clusters of cell bodies in the PNS known as?
What are Neuronal Processes?
Armlike extensions emanating from every neuron. Dendrites and Axons. The CNS consists of both cell bodies and processes whereas the bulk of the PNS consists of processes
What are bundles of processes in the CNS called?
What are bundles of processes in the PNS called?
What are dendrites and their functions?
thin, branched processes whose main function is to receive incoming signals. They increase surface area to increase ability to communicate with other neurons. Convey info towards soma through graded potentials.
What is an axon and its function?
A single process designed to convey info away from the cell body. Originates from a special region called the axon hillock. Transmits action potentials from the cell body toward the end of the axon where they cause NT release.
What is an Axon Terminal?
A specialized ending of the fine extensions of an axon. The axon terminal ends with synaptic bulbs.
What part of the neuron must be stimulated in order for an action potential to self-propagate along the axon?
What is the Axolemma?
Axon plasma membrane
What surrounds an Axon and what is its function?
Myelin sheath, a wrapping made of lipids that protects the axon and electrically isolates it. Increases the rate of action potential.
What are nodes of Ranvier?
Interspersed along the axon are gaps where there is no myelin.
What is the neurilemma?
In the PNS the exterior of the Schwann cell surrounding the axon
How does communication work?
Begins with the stimulation of a neuron, once stimulated it will communicate info about the event. Sensory neurons (afferent neurons) send info to neurons in the brain and spinal cord. There, association neurons (interneurons) integrate the info and send commands to motor neurons (efferent neurons) which synapse with muscles or glands.
What two ways do neurons conduct information?
1. From one end of a neuron to the other and 2. Across the minute space (synapse) separating neurons (accomplished electrically via action potentials or via neurotransmitters)
What is graded potential?
A slight difference in charge across the membrane of a cell.
What will happen if the graded potential change is suprathreshold?
An action potential will be initiated in the axon hillock and it will travel down the axon to the synaptic knob where it will cause neuro transmitter exocytosis.
What will happen if the graded potential change is subthreshold?
No action potential will ensue and nothing will happen
What is the rising phase of an Action Potential?
is Vm reaches threshold, Na+ channels open and Na+ influx ensues, depolarizing the cell and causing the Vm to increase.
What is the falling phase of Action Potential?
Eventually, the Na+ channel will have inactivated and the K+ channels will be open. Now, K+ effluxes and repolarization occurs.
What are the two gates on a Na+ Channel?
The activation gate (closed when at rest) and the inactivation gate (open when at rest)
What is the function of the activation gate, when is it activated and what happens?
At resting membrane potential the activation gate closes the channel. Depolarizing stimulus arrives at the channel. The activation gate opens and Na+ enters the cell.
What is the function of the inactivation gate, when is it activated and what happens?
When the action potential is met the inactivation gate closes and no more Na+ enters the cell. During repolarization caused by K+ leaving the cell the two gates reset.
What is the Absolute Refractory Period?
A Na+ channel CANNOT be involved in another action potential until the inactivation gate has been reset.
What is the Relative Refractory Period?
An action potential can be reached but the stimulus would have to be much stronger than usual.
What is Continuous Conduction?
Occurs in unmyelinated axons. The wave of de and re-polarization simply travels from one patch of membrane to the next adjacent patch (like dominoes falling).
What is Saltatory Conduction?
Occurs in myelinated axons. The action potential is regenerated at nodes of Ranvier and is sped up down the axon.
What is an Excitatory Postsynaptic Potential (EPSP)?
A graded depolariztion that brings the neuronal Vm closer to threshold.
What is a Inhibitory Postsynaptic Potential (IPSP)?
Graded hyperpolarizations bring the neuronal Vm farther away from threshold.
What is Temporal Summation?
The same presynaptic neuron stimulates the postsynaptic neuron multiple times in a brief period. The combination of stimulation may be able to cause an action potential.
What is Spatial Summation?
Multiple neurons all stimulate a postsynaptic neuron resulting in a combination of Excitatory Postsynaptic Potential which may yeild an action potential.