Lab #9: Neuromuscular Junction, Nervous System Histology, & Neurophysiology

Question 1

Neuron

Answer 1

cell of the peripheral nervous system

Question 2

What is a neuromuscular junction and what is its function?

Answer 2

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

Question 3

Where is the NMJ located and how many are there?

Answer 3

At the center of each muscle fiber, and there is only one per muscle fiber

Question 4

Why is the NMJ located at the center of each muscle fiber?

Answer 4

Because when stimulated to contract, the muscle fiber will shorten uniformly and not disproportionately beginning at either end

Question 5

What is the NMJ sometimes referred to? Why?

Answer 5

The NMJ is sometimes referred to as the motor end plate because it controls motor signals

Question 6

What does the NMJ help communicate?

Answer 6

voluntary signals for bodily movement from the brain to the skeletal muscles

Question 7

What is the synaptic cleft?

Answer 7

A small space that separates the axon terminal and the motor end plate

Question 8

The human nervous system is the primary defining feature of what __________.

Answer 8

distinguishes humans from other species

Question 9

Nervous system functions

Answer 9

• communication between various components of the body

- higher cognitive functions (such as learning, reasoning, sense of self, consciousness)

Question 10

What is the basic functional unit of the nervous system?

Answer 10

the nerve cell, or neuron

Question 11

Nerve cells are located throughout ______.

Answer 11

the central and peripheral nervous system

Question 12

Nervous system is anatomically split into 2 classifications:

Answer 12

• The central nervous system (CNS)

- The peripheral nervous system (PNS)

Question 13

3 basic parts of a neuron

Answer 13

• cell body (soma)
• axon
• dendrite

Question 14

The neuron cell body is also called the…

Answer 14

soma

Question 15

Axons may be either _____ or _____.

Answer 15

Myelinated or unmyelinated

Question 16

What is the function of a myelin sheath?

Answer 16

The myelin sheath, when present, insulates the nerve axon from surrounding tissue, which increases the speed and efficiency of conduction

Question 17

The distal end of the axon contains a ___.

Answer 17

synapse

Question 18

Synapse

Answer 18

where neurotransmitter is released and the next cell in the circuit responds to the neurotransmitter

Question 19

Neurons can be grouped into 3 major categories…

Answer 19

• Pseudounipolar neuron
• Bipolar neuron
• Multipolar neuron

Question 20

Pseudounipolar neuron

Answer 20

-have one single axon with dendrites at one end and a synapse at the other

Question 21

Bipolar neuron

Answer 21

-have one long dendritic process and one axon

Question 22

Multipolar neuron

Answer 22

-have any dendritic processes and one axon

Question 23

The ______ cells make up the majority of cells in the nervous system

Answer 23

neuroglia or glial cells

Question 24

Glial cells have various roles that help support the structure and function of neurons. How many types are there? Name them.

Answer 24

1) Astrocytes
2) Microglia
3) Oligodendrocytes
4) Schwann cells
5) Ependymal cells

Question 25

Astrocytes (type of cell and function)

Answer 25

• 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

Question 26

Microglia (type of cell and function)

Answer 26

• glial cell

- immune system cells that reside in the nervous system and act as phagocytes

Question 27

Oligodendrocytes (type of cell and function)

Answer 27

• glial cell

- produce myelin in the CNS

Question 28

Schwann cell (type of cell and function)

Answer 28

• glial cell

- produce myelin in the PNS

Question 29

Ependymal (type of cell and function)

Answer 29

• glial cell

- form cerebrospinal fluid (CSF) and assist with the flow of CSF through the ventricles and fluid spaces

Question 30

Nerve cells have 2 essential characteristics that allow them to carry out their functional role in the body: _____ and _____.

Answer 30

excitability and conductivity

Question 31

Excitability in nerve cells

Answer 31

The ability of a nerve cell to respond to a stimulus (stimuli may be mechanical, chemical, or electrical)

Question 32

Conductivity in nerve cells

Answer 32

The ability of a cell to carry the excitation response along the length of the nerve cell axon

Question 33

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

Answer 33

• ions (charged particles)

- electrochemical current

Question 34

Depolarization

Answer 34

when the action potential travels down the axon as a wave

Question 35

When the wave of depolarization reaches the axon, it triggers ________.

Answer 35

the release of synaptic vesicles containing neurotransmitters into the synaptic cleft. Then, the neurotransmitters bind to the postsynaptic neuron (target cell) and activate it.

Question 36

Resting membrane potential. What is it and why is there a voltage difference?

Answer 36

• 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

Question 37

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 _____.

Answer 37

Extracellular: high Na+ and low K+
Intracellular: high K+ and low Na+

Question 38

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?

Answer 38

-70 mV