BIO 474 Lecture Notes - Lecture 8: Axon Hillock, Axon Terminal, Neuroglia

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17 May 2018

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What are the two main types of cells in the nervous system?

Neurons and Glial cells

What do neurons do?

Transmit signals

What do glial cells do?

Support the neurons

What are the four main structural components of the neuron?

Soma/cell body/perikaryon, dendrites, axon, axon terminal

Where are signals received?

Dendrites

Where are signals sent away?

Axon

What kind of shape does the soma have?

Pyramidal

Where are excitatory synapses formed?

Dendritic spines

Where are inhibitory synapses formed?

Dendritic shaft

Do neurons have a single axon or more than one?

A single axon (and it does not have spines.)

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Intrinsic axon projections

Terminate within the same structure that has the cell body in it

Extrinsic axon projections

Terminate elsewhere, outside of the structure that has the cell body in it

What is the Neuron Doctrine and who came up with it?

Says that the basic component of the nervous system is the individual neuron, and not a web of

neurons. Formed by Cajal.

When a signal is received, what is the flow of information (where does it start and end up?)

Dendrites --> Soma --> Axon --> Axon Terminal

Passive conductance

Response is generated, but it doesn't reach the threshold for an action potential to form.

Active conductance

All or none response

Backpropagation of signals

Retrograde transmission of signals back up the axon

Neuronal morphologies

Unipolar, Bipolar, Pseudopolar (one side skin, one side spinal cord), and Multipolar

Where is the Purkinje cell located?

Cerebellum

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What are the four functional components of the neuron? Describe them.

Input component: Soma, where input is received.

Integrative component: Axon hillock, where if the signal reaches a certain threshold, you get a response.

Conductile component: axon, where if you get a response, it's all or none down to the terminal.

Output component: axon terminal, where neurotransmitters are released as output

What is a graded response?

A response in which the amplitude and duration of the input is proportional to that of the output.

Which functional components have graded responses?

Input

What is a non-decremental response?

A response in which the level of input is not proportional to the level of output.

Which functional components have non-decremental responses?

Integrative and conductile

If a signal goes, is it 1) excitatory or inhibitory and 2) polarizing or depolarizing?

1) Excitatory 2) Depolarizing

Describe the difference in input/output ratios in passive and active responses.

PASSIVE RESPONSE

Input: Synaptic potential is EQUAL to Output: Membrane potential change

ACTIVE RESPONSE

Input: Synaptic potential is NOT EQUAL to Output: Membrane potential change

The conductile component has what kind of response?

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Document Summary

A single axon (and it does not have spines. ) Terminate within the same structure that has the cell body in it. Terminate elsewhere, outside of the structure that has the cell body in it. Says that the basic component of the nervous system is the individual neuron, and not a web of neurons. When a signal is received, what is the flow of information (where does it start and end up?) Dendrites --> soma --> axon --> axon terminal. Response is generated, but it doesn"t reach the threshold for an action potential to form. Retrograde transmission of signals back up the axon. Unipolar, bipolar, pseudopolar (one side skin, one side spinal cord), and multipolar. Integrative component: axon hillock, where if the signal reaches a certain threshold, you get a response. Conductile component: axon, where if you get a response, it"s all or none down to the terminal. Output component: axon terminal, where neurotransmitters are released as output.

Related Questions

Nerve cells that conduct messages are called (1) ____. (2) _____ cells, which support and nurture the activities of neurons, make up less than half the volume of the nervous system. (3) _______ neurons respond to specific kinds of environmental stimuli, (4) ______ connect different neurons in the spinal cord and brain, and (5) ______ neurons are linked with muscles or glands. All neurons have a (6) _______ ________ that contains the nucleus and the metabolic means to carry out protein synthesis. (7) _______ are short, slender extensions of the (6), and together these two neuronal parts are the neuronsâ âinput zoneâ for receiving (8) _____. The (9) _____ is a single long, cylindrical extension away form the (10) ______; in motor neurons, the (11) ______ has finely branched (12) ________ that terminate on muscle or gland cells and are âoutput zones,â where messages are sent on to other cells. A neuron at rest establishes unequal electric charges across its plasma membrane, and a(n) (13) ____ ____ is maintained. Another name for (13) is the (14) _____ _____ _____; it represents an ability for the membrane to be disturbed. Weak disturbances of the neuronal membrane might set off only slight changes across a small patch, but strong disturbances can cause a(n) (15) _______ ______, which is an abrupt, short-lived reversal in the polarity of charge across the plasma membrane of the neuron. For a fraction of a second, the cytoplasmic side of a bit of membrane becomes positive with respect to the outside. The (16) ______ that travels along the neural membrane is nothing more than short-lived changes in the membrane potential. A. Neurons H. Sensory B. Motor I. Endings C. Interneurons J. Disturbance D. Cell body K. Signals (stimuli) E. Axon L. Voltage differential F. Dendrites M. Resting membrane potential G. Neuroglial N. Action potential

azureelk922

Which of the following statements is TRUE regarding sea anemones?

	None of the answer options is correct.
	Spongesânot sea anemonesâpossess what is considered to be the âsimplestâ nervous system found in animals.
	Because sea anemones are âsimpleâ organisms, these animals only possess motor neurons; sensory neurons or interneurons are never found in sea anemones.
	Although sea anemones possess ânet-likeâ nervous systems, these animals have brains located at their bases (near where they would attach to rocks).
	Although sea anemones lack definitive brains, they do possess ganglia that serve a similar function to the paired ganglia of flatworms.

Some people have low levels of calcium circulating in the blood, a condition known as hypocalcemia. While for many this disorder has little to no effect, for some it can be life-threatening. How could low levels of calcium harm an individual?

	Low levels of calcium would not have any effect on synaptic transmission.
	Low levels of calcium would cause sustained depolarization of the presynaptic cell.
	Low levels of calcium would result in fewer signals sent between the pre- and postsynaptic cell.

Cephalization is: the

	All of these choices are correct.
	development of a brain within the head of an animal.
	concentration of sensory organs within the head end of an animal.
	development of a âhead endâ in an organism.

Which of the following are TRUE about the resting membrane potential? (Select all that apply.)

	It results from voltage-gated sodium channels remaining open for long periods of time.
	It results from K⁺ ions diffusing out of the cell.
	It results from the sodium-potassium pump moving more Na⁺ ions out of the cell than K⁺ ions into the cell.

Afferent and efferent neurons differ in:

	their size.
	the directionality of the information they send.
	their pattern of myelination.

A neuron that responds to the environment is a(n):

	interneuron.
	homeostatic neuron.
	motor neuron.
	sensory neuron.

Which of the following is NOT the role of an interneuron?

	stimulating a muscle to contract
	conveying information from the internal environment of an animal
	relaying information from sensory to motor neurons
	maintaining homeostasis

Where are postsynaptic cell receptor proteins synthesized?

	the Golgi apparatus
	the lysosome
	the cytoplasm
	the rough endoplasmic reticulum

Inhibition of the flexor muscle during the knee-extension reflex is an example of:

	homeostasis.
	reciprocal inhibition.
	negative feedback.
	All of these choices are correct.

10.

What type of cells produce myelin for sensory neurons?

	pyramidal neurons
	glial cells
	melanocytes
	astrocytes

Amy is cooking dinner for her family. She moves to pull a pot off the stove and accidently touches the burner. She reflexively pulls her finger away from the stove and immediately feels the pain. Which receptor neuron is responsible for sending information from her finger to her peripheral nervous system? Is this receptor neuron, an afferent or efferent neuron? Explain where the information from the receptor neuron is sent and how does it result in Amy moving her finger away from the stove. How many neurons are typically involved in this response? What are the names of these neurons? Evolutionarily, why do you think the human body has this system in place? What might happen if we did not have this response?

Glen, who is 45 years old, begins to notice that his hands shake (tremors) when he is performing everyday tasks such as signing his signature. His family members have noticed that he also has muffled speech and tends to shuffle when he walks. He is diagnosed with Early Onset Parkinsonâs disease. What is Early Onset Parkinsonâs disease? What specific cell type is affected in Parkinsonâs disease? What is dopamine? What effects does dopamine have on the body? Explain the structure of a synapse and why Glenâs neurologist would prescribe him a dopamine agonist? Glen has genetic testing performed and it is determined that he does carry an autosomal dominant mutation in the SNCA gene associated with Early Onset Parkinsonâs disease. Glen has three children. Would you advise his children to have genetic testing performed to determine if they also carry the disease mutation? Why or why not?

Patricia, who is 37 years old, discusses with her physician recent symptoms that she has experienced including blurred vision, numbness in her fingers and face, dizziness, fatigue and weakness. The physician performs multiple neurological tests and she is diagnosed with multiple sclerosis (MS). What is MS? Is MS a disease of the central or peripheral nervous system? What is the main cell structure affected in MS? How is the action potential of a neuron affected in MS? The origins of MS are not clear. What do scientists hypothesize to be the causes of MS?

BIO 474 Lecture Notes - Lecture 8: Axon Hillock, Axon Terminal, Neuroglia

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