Lab #9: Neuromuscular Junction, Nervous System Histology, & Neurophysiology Flashcards
Neuron
cell of the peripheral nervous system
What is a neuromuscular junction and what is its function?
The NMJ is a specialized structure (synapse) that allows for communication to occur between a cell of the peripheral nervous system (neuron) and a cell/fiber of a skeletal muscle
Where is the NMJ located and how many are there?
At the center of each muscle fiber, and there is only one per muscle fiber
Why is the NMJ located at the center of each muscle fiber?
Because when stimulated to contract, the muscle fiber will shorten uniformly and not disproportionately beginning at either end
What is the NMJ sometimes referred to? Why?
The NMJ is sometimes referred to as the motor end plate because it controls motor signals
What does the NMJ help communicate?
voluntary signals for bodily movement from the brain to the skeletal muscles
What is the synaptic cleft?
A small space that separates the axon terminal and the motor end plate
The human nervous system is the primary defining feature of what __________.
distinguishes humans from other species
Nervous system functions
- communication between various components of the body
- higher cognitive functions (such as learning, reasoning, sense of self, consciousness)
What is the basic functional unit of the nervous system?
the nerve cell, or neuron
Nerve cells are located throughout ______.
the central and peripheral nervous system
Nervous system is anatomically split into 2 classifications:
- The central nervous system (CNS)
- The peripheral nervous system (PNS)
3 basic parts of a neuron
- cell body (soma)
- axon
- dendrite
The neuron cell body is also called the…
soma
Axons may be either _____ or _____.
Myelinated or unmyelinated
What is the function of a myelin sheath?
The myelin sheath, when present, insulates the nerve axon from surrounding tissue, which increases the speed and efficiency of conduction
The distal end of the axon contains a ___.
synapse
Synapse
where neurotransmitter is released and the next cell in the circuit responds to the neurotransmitter
Neurons can be grouped into 3 major categories…
- Pseudounipolar neuron
- Bipolar neuron
- Multipolar neuron
Pseudounipolar neuron
-have one single axon with dendrites at one end and a synapse at the other
Bipolar neuron
-have one long dendritic process and one axon
Multipolar neuron
-have any dendritic processes and one axon
The ______ cells make up the majority of cells in the nervous system
neuroglia or glial cells
Glial cells have various roles that help support the structure and function of neurons. How many types are there? Name them.
1) Astrocytes
2) Microglia
3) Oligodendrocytes
4) Schwann cells
5) Ependymal cells
Astrocytes (type of cell and function)
- glial cell
- star shaped, long projections that wrap around the blood vessels and brain
- important component of the blood-brain barrier, which controls which substances form the blood enter nerve tissue
Microglia (type of cell and function)
- glial cell
- immune system cells that reside in the nervous system and act as phagocytes
Oligodendrocytes (type of cell and function)
- glial cell
- produce myelin in the CNS
Schwann cell (type of cell and function)
- glial cell
- produce myelin in the PNS
Ependymal (type of cell and function)
- glial cell
- form cerebrospinal fluid (CSF) and assist with the flow of CSF through the ventricles and fluid spaces
Nerve cells have 2 essential characteristics that allow them to carry out their functional role in the body: _____ and _____.
excitability and conductivity
Excitability in nerve cells
The ability of a nerve cell to respond to a stimulus (stimuli may be mechanical, chemical, or electrical)
Conductivity in nerve cells
The ability of a cell to carry the excitation response along the length of the nerve cell axon
When a nerve cell is stimulated, channels open in the membrane to allow ____ to flow across the membrane. This results in a ______ ______ that moves along the length of the axon
- ions (charged particles)
- electrochemical current
Depolarization
when the action potential travels down the axon as a wave
When the wave of depolarization reaches the axon, it triggers ________.
the release of synaptic vesicles containing neurotransmitters into the synaptic cleft. Then, the neurotransmitters bind to the postsynaptic neuron (target cell) and activate it.
Resting membrane potential. What is it and why is there a voltage difference?
- electrical state of the nerve at rest
- nerve cell membrane separates intracellular fluid from the extracellular fluid
- voltage difference is due to asymmetric distribution of ions
In resting membrane potential, the extracellular compartment has a high concentration of ____ and a low concentration of ____. The intracellular compartment has a high concentration of ____ and a low concentration of _____.
Extracellular: high Na+ and low K+
Intracellular: high K+ and low Na+
Resting membrane potential is maintained at rest by the sodium-potassium pump (making it a negative environment within the nerve cell). What is that negative value in millivolts?
-70 mV
