Nerve cell shape. All of these choices are correct.
Nerve cell shape. It is the axon that propagates the nerve .
Nerve cell shape This article provides an overview of neuron structure and function in the human nervous system. 1 – add to image the term axon, reference cells without one). Controlling cell shape Jan 1, 2014 · While in a nonneuronal tissue most cells have a roughly similar shape, nerve cells exhibit a great variety of forms. Nearly 86 billion neurons work co-ordinately within the nervous system to keep the body organized. The geometry of a neuron’s dendrites and axon also vary tremdously with its role in the neural circuit. the Dec 5, 2024 · WOODS HOLE, Mass. Find out how nerve cells transmit information through electrical impulses and what diseases affect them. Spheroidal. All of these choices are correct. Lamins: Components of the nuclear lamina. Aug 22, 2012 · Neurons are often named after their appearance. com / releases / 2019 / 04 Feb 15, 2024 · As these cardiac cells cannot divide, satellite cells are responsible for replacing the damaged ones. Anatomically, a nerve cell consists of several parts mentioned above. transcytosis. Q. Neutrophils Study with Quizlet and memorize flashcards containing terms like which anima possesses a brain, which part of a cell's cytoplasm is responsible for the diversity of nerve cell shape, Which scenario would be most likely to result in an action potential within the postsynaptic cell? Please choose the correct answer from the following choices, and then select the submit answer button. Each cell type has evolved a shape that is best related to its function. These neurons have one axon but several dendrites to form a pyramid type shape. phagocytosis. Justify its shape with regards to its function. They stretch from your hips all the way down to your toes! This is very uncommon for cells, which are usually very short. com Jan 16, 2024 · A neuron is a nerve cell that processes and transmits information through electrical and chemical signals in the nervous system. Mar 12, 2024 · The diagram of nerve cell includes the labelled structures of the nerve cell like axons, dendrites, and the cell body. Different parts of the body perform individual functions. , 2016). The popular cell biology text book written by Alberts et al. Microvilli, found in the epithelial cells of the small intestine, are How nerve cells stay in shape January 17 2006 Nerve cells with intact synapses. If a nerve cell has an abnormal shape, it is likely that the cytoskeleton is defective. Structure of a Nerve Cell: A nerve cell consists of three main parts: the cell body, dendrites, and an axon. They consist of a cell body (soma) which contains the nucleus, dendrites that branch out from the cell body to receive signals from other neurons, and a long axon that transmits signals to other neurons. the endomembrane system A nerve cell (neuron) consists of a large cell body and nerve fibers—one elongated extension (axon) for sending impulses and usually many branches (dendrites) for receiving impulses. True b. They are highly specialized cells that act as information processing and transmitting units of the brain. For instance, the nerve cell, which transmits the electrical impulse from our brain to the end of the toe finger may be the largest nerve cell. Nerve cells have a rather special shape compared to the rest of Dec 5, 2024 · In a provocative new study, scientists challenge a fundamental tenet in neuroscience about the shape of axons -- the long, thin filaments radiating from nerve cells that transmit electrical For example, a nerve cell is long and branched, meant for the transmission of signals throughout our body while a muscle cell is small and spindle-shaped which helps in movement. They are adapted to carry electrical impulses from one place to another. Unipolar cells are another subtype of neurons Jul 10, 2019 · TL;DR (Too Long; Didn't Read) The structure and shape of each type of human cell depends on what function it will perform in the body. This determines their capacity for interacting with their environment and with other nerve cells or neurons, hence their computational ability and roles. This shape is called a tetrakaidecahedron and is proposed to be most effective in fitting cells tightly together (Yokouchi et al. Synaptic connections allow communication between neurons, facilitating the relay of information throughout the body. both the shape of the cell and the proteins in its cytosol or membrane. Mar 18, 2019 · Experiments that confined dividing cells inside microscopic channels, restricting their dimensions, revealed that the spherical stage is essential for chromosomes to be distributed equally among daughter cells. Neurons consist of a cell body, dendrites (which receive signals), and an axon (which sends signals). Also, the “fingers” at the ends help transmit the messages to more than one other nerve cell so the message can reach either the brain or the spinal cord faster. These are the largest neuron cells and are mostly found Nerve cell shapes vary according to the number, branching and disposition of their projections or dendrites, collectively known as arborization. -- In a provocative new study, scientists challenge a fundamental tenet in neuroscience about the shape of axons -- the long, thin filaments radiating from nerve cells that transmit electrical signals from cell to cell – and propose a new model for understanding how information is transmitted in the brain. Answer A dendrite (from Greek δένδρον déndron, "tree") or dendron is a branched cytoplasmic process that extends from a nerve cell that propagates the electrochemical stimulation received from other neural cells to the cell body, or soma, of the neuron from which the dendrites project. To arrive at the more than 100 billion neurons that are the normal complement of a newborn baby, the brain must grow at the rate of about 250,000 nerve cells per minute, on average, throughout the course of pregnancy. Each nerve cell receives input from another nerve cell or cells and sends output to the other nerve cell or cells. Among these varied cell-types, nerve cells – the cells that make up the brain are considered the most proficient. They transmit electrical signals, called nerve impulses. A neuron varies in shape and size depending on its function and location. The tiny cell on the top right is called a cerebellar granule cell and the top left is a unipolar brush cell. The axon is The three-dimensional shape of these cells makes the immense numbers of connections within the nervous system possible. Oct 31, 2003 · To date, the functions of most neural intermediate filament (IF) proteins have remained elusive. Neurons can be classified with reference to morphology or functionality. Cell Size. The cell body contains the nucleus and most of the Apr 3, 2019 · IOS Press. Jan 19, 2006 · How Nerve Cells Stay In Shape Date: January 19, 2006 Source: Max Planck Society Summary: Max Planck Researchers have identified a protein that is essential for the maintenance of synapses: if the Jan 1, 2025 · However, these cells all have common abilities, such as obtaining and using food energy, responding to the external environment, and reproducing. the cytoskeleton C. See full list on vedantu. The large one is called a Golgi cell, named for Camillo Golgi who won the Nobel Prize in 1906. To simplify, we may say that most neurons possess a body and two types of process, called dendrites and axons (Fig. the synapse Jun 28, 2020 · Interneurons or relay neurons connect a sensory nerve cell to a motor nerve cell as shown in the neuron diagram below. These are branch-like structures that receive messages from other neurons and allow the transmission of messages to the It is responsible for transmitting information throughout the body via electrical and chemical signals. They form a meshwork beneath the nuclear envelope and help maintain the integrity of the nuclear envelope. Following are the different parts of a neuron: Dendrites. C. Connection between sensory, inter, and motor neurons. Nerve cells are also some of the longest cells in your body. The shape, size, and structure of nerve cells depend on their position and function in the body. difference in concentration of ions and charged molecules on the two sides of a cell's plasma membrane. Smooth muscle cells. We discussed these previously in Chapter 3. They are located in the brain and spinal cord and help to receive and conduct impulses. The nerve cell or neuron is the primary structural and functional unit of the nervous system. Each shape of the cell has a specific function of its own. e how long electrical impulse is transmitted within our body. 2) Cell shapes are classified as being either squamous (flattened and thin), cuboidal (boxy, as wide as it is tall), or columnar (rectangular, taller than it is wide). , 2013). the pattern of the nerve cells is a nerve cell and a long thin axon branching out behind it ALMOST connecting to another nerve cell. For example, they provide Dec 5, 2014 · The ostrich egg in the Figure above is over 10,000 times larger than the mouse cell. For example, the cells in our bones replace themselves frequently at a rate of about 10% each year. The nerve cell is a specialized individual cell that forms our nervous system. Since electrical signals travel much faster than chemical signals, neurons are long and thin to minimize the number of slower chemical signals that would be required between links in a chain of many shorter neurons. Nov 6, 2024 · Cell Shape and Membrane Modifications: allowing rapid communication between nerve cells. Study with Quizlet and memorize flashcards containing terms like Cephalization is associated with the development of a "head end" in an organism. For example, the long extensions that reach out in various directions from certain nerve cells allow the cell to send and receive nerve impulses. the cytoplasm C. There are nerve cells as long as a meter. Dendrites receive and integrate signals from other Jan 22, 2025 · Nervous system - Neurons, Signals, Reflexes: The watershed of all studies of the nervous system was an observation made in 1889 by Spanish scientist Santiago Ramón y Cajal, who reported that the nervous system is composed of individual units that are structurally independent of one another and whose internal contents do not come into direct contact. We are constantly replacing non-neuronal cells. endocytosis. number and types of ion-channel proteins present in Study with Quizlet and memorize flashcards containing terms like The release of neurotransmitter from the presynaptic cell is an example of: A. Cell body Jan 11, 2024 · Nerve cells (neurons) form the structural and functional units of the central and peripheral nervous systems. A nerve cell is a cell, and it is also called a neuron or simply a nerve. Their shape and size can vary depending on their location and function within the body. the concentration of sensory organs within the head end of an animal. iv. Usually, the size of nerve cells varies depending on how long the electrical impulses are to be transmitted. the rough endoplasmic reticulum B. A group of neurons forms a nerve. They A nerve cell (neuron) consists of a large cell body and nerve fibers—one elongated extension (axon) for sending impulses and usually many branches (dendrites) for receiving impulses. Feb 2, 2023 · Neurons or nerve cells are the basic building blocks or units of the nervous system. Each cell has a shape that has evolved to allow the cell to perform its function effectively. Some also consists of long and branched like nerve cell which is used to transfer and receive the signals. They carry an electrical message or impulse when stimulated. The neuron is a specialized and individual cell, which is also known as the nerve cell. The axon ends in multiple axon terminals. Apr 4, 2024 · Learn about the different types and functions of nerve cells, also called neurons, which are the cells of the nervous system. Unipolar. May 29, 2024 · For example, a nerve cell's elongated shape allows for rapid transmission of electrical signals, while a red blood cell's small, disc-like shape maximizes its ability to carry oxygen. Despite the specific molecular, morphological, and functional features of any particular nerve cell type, the basic structure of neurons resembles that of other cells. May 3, 2011 · Neurons and NervesNeurons are unique for many reasons. Jul 1, 2022 · These connections were mainly possible because of the cells’ unique shape. Plant cells are much more rigid and rectangular in shape. Plant cells and animal cells have almost permanent shapes. B. The key parts of a nerve cell are then enumerated and defined, including the cell body, nucleus, dendrites, axon, axon terminals, node of Ranvier, Schwann's cells, myelin sheath. Smooth muscle cells are elastic, not striated, spindle-shaped and contain a single central nucleus. The endomembrane system does not affect shape, as its location is associated with the nucleus, which also has no bearing on the shape morphology of a nerve cell. These nerve cells have a lengthy fibrous structure. We are constantly replacing non-neuronal cells. The cell's constituent is enclosed in a membrane, which provides shape to the plant and animal cells. Parts of Neuron. A typical multipolar neuron is comprised of soma or cell body, an axon, and dendrites. The variety of cell shapes seen in prokaryotes and eukaryotes reflects the functions that each cell has, confirming the structure-function relationship seen throughout biology. This morphology enables neurons to What part of a cell's cytoplasm is responsible for the diversity of nerve cell shape? the cytoskeleton The cytoskeleton is responsible for controlling cell size and shape. A nerve cell is made up of three main parts; the cell body, the dendrites, and the axon. sciencedaily. A new study shows how they can change the shape of nerve endings and distinguish between the different types Jan 11, 2023 · Why is the nerve cell that shape? Nerve cell shapes vary according to the number, branching and disposition of their projections or dendrites, collectively known as arborization. It is the axon that propagates the nerve . Study Materials. the shape is hard to pinpoint because it has dendrites branching out in different directions. They develop embryologically as bipolar in shape, and are thus termed pseudounipolar instead of unipolar. Neurons are the structural and functional units of the nervous system. Some of the cells are long and pointed on both ends such are spindle shape cells which helps in movement. Dendrites and axons are nerve fibres. Some neurons have a single long extension (axon) that reaches great distances, others are very small, star shaped cells without obvious axons (See Figure 12. The size of Study with Quizlet and memorize flashcards containing terms like Ganglia were the evolutionary precursor to the centralized concentration of neurons that we now call a brain. Nerve cells, also known as neurons, have a unique shape to facilitate their function. Nerve cells are adapted to carrying impulses. These cells are found in the vestibulocochlear (hearing), olfactory and ocular (viz. 3. . Abnormalities in a protein affecting how nerve cells change shape. Nerve cells allow communication between different parts of the body through electrical signaling What function do nerve cells perform? Login. The neuron has three main components: (1) the dendrites, thin fibers that extend from the cell in branched tendrils to receive information from other neurons; (2) the cell body, which carries out most of the neuron’s basic cellular functioning; and (3) the axon, a long, thin fiber that carries nerve impulses to other neurons. Neuron or a nerve cell looks like a star-shaped cell with a tail. Study with Quizlet and memorize flashcards containing terms like What part of a cell's cytoplasm is responsible for the diversity of nerve cell shape? A. Nerve cells are required for the transmission of electrical impulses. False, Membrane potential is determined by the: a. Dec 2, 2024 · WOODS HOLE, Mass. Movement of gases across plasma membrane occurs through ______________ Neurons carry information from the brain and spinal cord to the rest of the body by means of electrical signals. This system ensures that cells maintain their proper structures, allowing them to function correctly. Nerve cells are elongated and have divisions because they require more surface area to transmit the signals to different cells with the help of the nervous system. Smooth muscle cells are arranged together in sheets and this organisation means that they can contract simultaneously. Nerve cells can contain fibres that are over The size of nerve cells is usually based on their functions i. Star-shaped cell. the axon. Jun 12, 2024 · Nerve cells, or neurons, have a unique shape with long, branching extensions called dendrites and axons that allow them to communicate with other neurons. Neurons are connected to other neurons at synapses and connected to effector organs or cells at neuroeffector junctions. D. All nerve cells are collectively referred to as neurons although their size, shape, and functionality may differ widely. Anatomy of a Nerve Cell. ScienceDaily. Functions of the cytoskeleton include: Structural support: It acts as the skeleton of the cell, maintaining its shape and preventing it from collapsing. Considering an animal cell, we can generalize the shape of a cell as round (spherical) or irregular. It serves as an educational tool to help the readers get a visual representation of the nerve cell that will help them understand various concepts of neuroscience. Feb 28, 2022 · The creation of new nerve cells is called neurogenesis. Every neuron is made of a cell body (also called a soma), dendrites and an axon. the nucleus D. The only exception to this rule is nerve cells that are connected to sensory receptors and Sep 29, 2020 · How does nerve cell shape and structure help it to do? The nerve cell’s thin and dainty shape helps it transmit signals. Epithelial tissues are classified according to the shape of the cells composing the tissue and by the number of cell layers present in the tissue. ii. Some cells, like a moeba and white blood cells, can change their shape. For example, red blood cells (RBCs) are very small, flat discs, which allows them to easily fit through narrow capillaries and around sharp corners in the circulatory system to deliver oxygen throughout the body. Cells that line the stomach Nerve cells Liver cells Cells that line the esophagus. A pseudounipolar neuron is a type of neuron which has one extension from its cell body. It is impossible in a single chapter to delineate comprehensively the extensive structural, topographical and functional variation achieved by this cell type. Draw a diagram of the human nerve cell. Cell Shape. Glial cells provide support for neurons. (Figure 4. A neuron, neurone, [1] or nerve cell is an excitable cell that fires electric signals called action potentials across a neural network in the nervous system. Using the latter classification scheme, three types of neurons can be defined: sensory neurons, connected to sensory receptors, motor neurons, connected Apr 11, 2016 · Glial cells nourish, protect, and support neurons, but their role is far from passive. Dec 10, 2024 · Interfering with certain components of the cytoskeleton, the network of protein filaments that serve as a scaffold that determines nerve cell shape, affected connector length and width, the researchers found. The cell body of a neuron contains many organelles that are surrounded by neuroplasm, which is the specialized name for the cytoplasm of nerve cells. Neurons are the basic units of the nervous system and its most important part is the brain. Nerve cells i. Thus, each nerve cell has a cell body containing a nucleus, endoplasmic reticulum, ribosomes, Golgi apparatus, mitochondria, and other organelles that are essential to the function of all cells (). Neurons employ both electrical and chemical components in the transmission of information. They have a single axon projecting from one end of the oval cell body and a lone dendritic tree extending from the other end. But it is not the volume of growth alone that makes the production Jul 24, 2023 · Neurons are electrically excitable cells that transmit signals throughout the body. (1983) lists 210 cellular phenotypes in the human body. b. retina) systems. However, because details of nerve cell shape are so closely associated with the electrical behavior of nerve cell membranes, this section offers an outline sketch (without illustrations) of how nerve cells manipulate localized changes in cell membrane potentials in order to carry out their functions of processing and transmitting information. If this shape change is prevented, the cell division fails (Lancaster et al. How is the axon part of the nerve cell? The human brain contains about 86 billion nerve cells. Dramatic increases in peripherin expression have been shown to coincide with the initiation and outgrowth of axons during development and regeneration, suggesting that peripherin plays an important role in axon formation. Similarly, cells in A nerve cell (neuron) consists of a large cell body and nerve fibers—one elongated extension (axon) for sending impulses and usually many branches (dendrites) for receiving impulses. There can be more than one interneuron in a circuit. Apr 26, 2021 · In this way, nerve cells relay information about your external environment (known as stimuli) to the brain for interpretation and trigger responses to those stimuli. “Together, these results suggest that the cytoskeleton contributes to nanopearling by determining the connector dimensions,” they wrote. They are found in the brain, spinal cord and peripheral nerves. It is also the major IF protein expressed in PC12 cells, a widely used model for studies of peripheral neurons. exocytosis. The impulses from the axon cross a synapse (the junction between 2 nerve cells) to the dendrite of another cell. iii. Since the cell body helps determine whether to send the information to the axon, it is often called the “control center” of the neuron. All neurons have three different parts – dendrites, cell body and axon. , Where are postsynaptic cell receptor proteins synthesized? A. Long, thin extensions (axons and dendrites) connect these nerve cells to other nerve cells. Study with Quizlet and memorize flashcards containing terms like What cellular component of a sensory neuron would account for its specialization in response to physical or chemical cues?, Before the evolution of complex nervous systems, animals with very simple nervous systems, such as the nerve nets of cnidarians, could engage in all of the behaviors except:, T/F: all animals sense and Sep 26, 2023 · Animal cell is rounded, spherical or elongated in shape whereas plant cells are rectangular and rigid in shape. Columnar. Nerve Cells. Nerve cells are usually shaped like trees or like elongated wires. This type of neuron contains an axon that has split into two branches. Nerve cells are also called neurons close neurons Nerve cells. The extensions aid the neuron in swiftly transmitting chemical and electrical information throughout the body. Nerve cells consist of a cell body (soma), dendrites, an axon and a specialized cytoskeleton. Dec 31, 1989 · to state that nerve cell shape and function are one and the same. Why are nerves shaped like that? Study with Quizlet and memorize flashcards containing terms like Pre-class review questions 35. , The action potential travels down: both the dendrite and axon. Additionally, the shape of neurons and the organization of the neurons on a microscopic level make them effective for sending signals in a very specific direction. (2019, April 3). Dec 16, 2024 · Nerve Cells are long and branched because they need to make contact with other nerve cells and carry signals over long distances (from brain to other parts of the body) Muscle cells are spindle shaped because muscles contract and relax. Peripherin is a type III intermediate filament (IF) protein that is expressed in developing and in differentiated neurons of the peripheral and enteric nervous systems. Dec 21, 2023 · The cell body of a neuron, also known as the soma, is typically located at the center of the dendritic tree in multipolar neurons. Although the nervous system is very complex, nervous tissue consists of just two basic types of nerve cells: neurons and glial cells. Mar 10, 2024 · What is a Nerve Cell? A nerve cell, also known as a neuron, is responsible for receiving and transmitting information throughout the body. 2. While different types of nerve cells make up the nervous system, they all contain these primary structures: Cell body (Soma) The soma is the cell body of the nerve cell that contains the nucleus. a. the endomembrane system B. Interneurons are found in the spinal cord where they play a significant role in reflex arcs. , What part of a cell's cytoplasm is responsible for the diversity of nerve cell shape? A. The development of the nervous system proceeds in three phases: first, nerve cells are generated through cell division; then, having ceased dividing, they send out axons and dendrites to form profuse synapses with other, remote cells so that communication can begin; last, the system of synaptic connections is refined and remodeled according to Aug 11, 2023 · Neurons come in many shapes and sizes, but most have three essential parts: a cell body, or soma, that contains the nucleus of the cell; dendrites, short branching structures that receive signals from other neurons and convey them towards the cell body; and an axon, a long slender projection that transmits signals away from the cell body to other neurons or muscle cells. 1). Dendrites–A branch-like structure that functions by receiving messages from other neurons and allow the transmission of messages to the cell body. Nerve cells send impulses around the body of animals in order to aid sensation and movement. the development of a brain within the head of an animal. Feb 23, 2022 · A nerve cell’s size and shape depend on its role and location, but nearly all nerve cells have three main parts: Dendrites that extend like branches and receive signals; A cell body containing the nucleus that holds the genetic material of the cell and controls its actions; An axon, a long structure that transmits messages Jul 17, 2023 · Bipolar cells are only associated with afferent impulses. Neurons are “forever” cells. So, spindle shape makes it easier to contract and relax What is shape of amoeba? Jan 30, 2024 · Our nervous system is a complex network of diverse nerve cells or neurons, as well as glial cells, that work together to coordinate the system's overall function. Jan 6, 2021 · Each cell type has evolved a shape that is best related to its function. Neurons are nucleated cells with specialized structural properties. 1, Which of the following is NOT the role of an interneuron? maintaining homeostasis relaying information from sensory to motor neurons conveying information from the internal environment of an animal stimulating a muscle to contract, Cephalization is thought to be an adaptation for: (Select all that It is also the major IF protein expressed in PC12 cells, a widely used model for studies of peripheral neurons. In part, a cell's shape determines its function. Cell Body–Each neuron has a cell body with a nucleus, Golgi apparatus The cells that make up living things are complex, versatile systems, capable of diverse functions. The propagation of a nerve impulse is due to changes in the permeability of the nerve cell membrane that allow for a voltage difference across the membrane. The specific Each nerve cell comprises the cell body, which contains the nucleus, the main dividing fiber, called the axon, and several smaller dividing fibers called the dendrites. Nerve cells have the task of sending signals between each other to carry information throughout the body. If cells are the main structural and functional unit of an organism, why are they so small? And why are there no organisms with huge cells? Oct 31, 2019 · Structure of Nerve Cell. From the round, pyramidal or spindle-shaped cell body the dendrites (greek: dendrites = tree-like) branch out like the top of a tree and the single axon travels out like the trunk. Nerve cells communicate by using electrical signals. The cell shape indicated by the pointer is _____. the Golgi apparatus D. How are nerve cells specialised? Long axon – they have a long axon to move the impulse from one part of the body to another. Retrieved January 29, 2025 from www. The cells were observed to have a 14 sided geometric shape, with 6 rectangular sides and 8 hexagonal sides. Sep 22, 2014 · The previously unknown nerve cell shape is now presented in the journal Neuron by a research team from Heidelberg, Mannheim and Bonn. I. Jan 15, 2020 · What is the cell shape of a nerve cell? Neuronal cell bodies also vary widely both in size (small, medium, large, and giant) and in shape (star-shaped, fusiform, conical, polyhedral, spherical, pyramidal). Aug 11, 2023 · Nerve cell (neuron) is the smallest functional structure of the nervous system and consists of three parts: cell body, dendrite, and axon. Neurons are classified into different categories based on different criteria, such as morphology, function, connections and neurotransmitters . Nerve cells are found in the brain, spinal cord, and peripheral nervous system. The animal brain has been deemed the most complex machine on earth, capable of functions even a computer cannot replicate. View More. The cell body, also called the soma, consists of a nucleus and its surrounding cytoplasm, named the perikaryon. Jan 24, 2023 · Fig: Muscle cells. It is spherical or polygonal in shape and relatively small, making up one-tenth of the total cell volume. For one, they have a shape that is not like any other cells. The making of the human brain from the tip of a 3 millimeter neural tube is a marvel of biological engineering. In the microscope, synapses from hippocampus nerve cells look like small, mushroom-shaped protuberances called dendritic Nov 9, 2017 · BRAIN CANDY A new database offers a deep look at living human nerve cells, revealing elaborate branching structures and myriad shapes, such as in this neuron called a pyramidal cell (cell image From a historical standpoint, no other cell type has attracted as much attention or caused as much controversy as the nerve cell. They help form and support the characteristic (and extreme!) shape of a nerve cell. Their function is to receive stimuli and transmit nerve impulses to the target organ. Nov 11, 2019 · It defines the nerve cell as the basic unit of the nervous system. Dramatic increases Additionally, the shape of neurons and the organization of the neurons on a microscopic level make them effective for sending signals in a very specific direction. The permeability of a nerve cell membrane depends upon the: number of open channels.