BIO 168 Chapter 11: Functional Organization of Nervous Tissue

True or False: The nervous system and the endocrine system are the major control systems of the body.

TRUE

a nerve is

a bundle of many axons that connects the CNS to sensory receptors, muscles, and glands.

electrical synapse

a gap junction that allows an ionic current to flow between adjacent cells

The central nervous system consists of the _____, which is found within the skull, and the ____ ____, which is found within the vertebral canal.

brain, spinal cord

tract

bundles of axons and their myelin sheaths in the CNS

nerve

bundles of axons and their myeline sheaths in the PNS

All of the bases for neuron classification:

-function -structure

axons

-a single axon arises from a cone shaped area of the neuron cell body called the axon hillock -as the axon hillock narrows it transitions into the initial segment (the actual beginning of the axon) -the combo of the axon hillock and initial segment is called the trigger zone (where action portentials are generated) -the cytoplasm of an axon is called axoplasm -plasma membrane can be called axolemma -axons terminate by branching to form small extensions with enlarged ends called presynaptic terminals -the presynaptic terminals store many secretory vesicles that contain signal molecules called neurotransmitters.

Dendrites

-extensions of the cell body and are the receiving portion of the neuron - short and often highly branched cytoplasmic extensions - many have small extensions (dendritic spines) where axons of other neurons form synapses with the dendrites - generate small electric currents that are conducted towards the neuron cell body

the PNS

-links the CNS with various parts of the body -carries information to different tissues of the body to the cns and carries commands from the cns that alter body activities -has 2 subdivisions: sensory (afferent) and motor (efferent) division

Which type of neuroglia helps promote and regulate synapse formation?

Astrocyte astrocytes also release chemicals that promote the development of synapses and help regulate synaptic activity by synthesizing, absorbing, and recycling neurotransmitters.

True or false: Motor neurons transmit nerve signals toward the CNS.

FALSE

True or False: The myelin sheath consists of connective tissue wrapped around the cell body and axon of a neuron.

FALSE myelin is formed from living cells and consist of multiple layers of cell membrane wrapped around only the axon.

Select all of the cell types that are components of the nervous system

Neurons and Neuroglia

Types of Neurons

Neurons are classified in two different ways: functionally or structurally. The functional classification is based on the direction in which action potentials are conducted. Sensory neurons (afferent neurons) conduct action potentials toward the CNS; motor neurons (efferent neurons) conduct action potentials away from the CNS toward muscles or glands. Interneurons conduct action potentials within the CNS from one neuron to another. The structural classification scheme is based on the number of dendrites. The three major structural categories are multipolar, bipolar, and pseudo-unipolar. Multipolar neurons (multi-, many) have many dendrites and a single axon. The dendrites vary in number and in their degree of branching (figure 11.5a). Most of the neurons within the CNS and motor neurons are multipolar.

The neuroglial cells of the ____ that provide insulation around the bodies of neurons in ganglia are called satellite cells.

PNS

Match the parts of the neuron with the correct description.

SOMA - also known as the cell body NISSL BODY - rough endoplasmic reticulum of a neuron responsible for protein synthesis COLLATERALS - branches of an axon PRESYNAPTIC TERMINAL - enlarged end of axon containing vesicles filled with neurotransmitters AXOPLASM - cytoplasm of an axon

arrangement of cell proceses relative to the neuron cell body is the basis for

STRUCTURAL neuron classification

The specific cell that is responsible for producing myelin in the PNS is the ____ cells.

Schwann

the blood-brain barrier

The endothelial cells with their tight junctions determines what substances can pass from the blood into the nervous tissue of the brain and spinal cord. vThe blood-brain barrier protects neurons from toxic substances in the blood, allows the exchange of nutrients and waste products between neurons and the blood, and prevents fluctuations in blood composition from affecting brain functions.

neuron

The structural features of a neuron are a cell body and two types of cell projections: dendrites and an axon

chemical synapse

a synapse where one cell releases a neurotransmitter to communicate with another cell

The PNS consists of

all the nervous tissue outside the CNS (nerves and ganglia)

astrocytes

are glial cells that are star-shaped because cytoplasmic processes extend from the cell body Astrocytes help regulate the composition of extracellular brain fluid. They do this by releasing chemicals that promote the formation of tight junctions between the endothelial cells of capillaries

Which neuroglial cell is involved in forming the blood-brain barrier?

astrocytes

enteric nervous system

consists of plexuses within the wall of the digestive tract the CNS can override enteric functions via parasympathetic and sympathetic actions.

PNS (peripheral nervous system)

cranial nerves and spinal nerves

Branched cytoplasmic extensions of the neuron that receive input and transmit signals toward the cell body are _____.

dendrites

Neuroglial cells that aid in the production of cerebrospinal fluid are the ____ cells.

ependymal

The free surface of ____ cells assists in the movement of cerebral spinal fluid.

ependymal

Sympatheric Nervous System

fight or flight most active during physical activity

the brain and spinal cord connect with eachother at the

foramen magnum of the skull

synapse

functional membrane-to-membrane contact of a nerve cell within another nerve cell, muscle cell, gland cell, or sensory receptor; functions in the transmission of action potentials from one cell to another; also called a neuromuscular junction

The category of cells of the nervous system that support and protect neurons are called ____ cells.

glial

Myelin has a high ____ concentration.

lipid

A cell that receives stimuli and transmits action potentials to other nerve cells or effector organs is a(n) _____.

neuron

The cell body of a neuron is also known as the _____.

soma

Arrangement of cell processes relative to the neuron cell body is the basis for ____ neuron classification.

structural

nucleus

a cluster of cell bodies and their dendrites in the CNS

galglion

a cluster of cell bodies and their dendrites in the PNS

On neurons, the process that is cylindrical and relatively unbranched is called a(n) ____.

axon

On the image, label A indicates _____ and label B indicates a(n) _____.

dendrites, axon *refer to screenshot*

the sensory division (afferent)

detects stimuli and transmits information in the form of action potentials to the CNS The CNS processes information, initiates responses, and integrates thoughts, emotions, and other mental processes.

groups of related nerve cell bodies located outside the central nervous system are called

ganglia

The general class of cells in the nervous system that protect nerve cells and help in their functioning are called ____ cells.

glial

the cells that account for over half the brain's weight and outnumber neurons by at least 10 times are called _____.

glial

The general types of cells that make up the nervous system are ____ and ____.

glial and neurons

support and protect neurons

glial cells

sensory receptors are located

in the skin, muscles, joints, internal organs, and specialized sensory organs, such as eyes and ears

Name the type of neuron found between an afferent pathway and an efferent pathway.

interneuron

ganglion

is a collection of neuron cell bodies located outside the CNS

the motor (efferent) division

is further divided into two subdivisions: somatic nervous system and the autonomic nervous system

The neuroglial cells that phagocytize dead tissue and foreign substances within the CNS are the ____.

microglia microglia become mobile and phagocytic in response to inflammation.

A neuron with one axon and multiple dendrites is called a _____ neuron.

multipolar

Select the item that is NOT a component of a neuron. Myelin, Dendrite, Cell body, Axon, Presynaptic Terminal

myelin

The layer called the ___ ___ insulates axons, both in the CNS and PNS.

myelin sheath

The brain, nerves, and sensory receptors are all part of the ____ system.

nervous

Supporting cells such as olgiodendrocytes and ependymal cells are examples of ____ cells.

neuroglia

cells of the nervous system are

neurons -neurons send electrical messages from their cell body to other cells with long extensions called axons.

neuron structure

neurons, nerve cells, are the electrically excitable cells of the nervous system. they receive stimuli and transmit action potentials to other neurons or effector organs three parts to a neuron: a cell body, two types of cellular projections the cell body is called the neuron cell body (soma); as with any other type of cell, the cell body's nucleus is the source of information for protein synthesis. one type of cellular production is called a dendrite (branching organization) the other type of cellular projection is called the axon (nerve fiber)

The neuroglial cells that form myelin sheaths around axons in the CNS are ____.

oligodendrocytes

A neuron with ____ processes extending from the cell body is called a pseudo-unipolar neuron.

one

convergent pathway

pathways that allow different parts of the nervous system to affect the activity of a neuron

divergent pathway

pathways that allow one part of the nervous system to affect more than one part of the nervous system

Schwann cells and satellite cells are examples of neuroglial cells in the ____ nervous system.

peripheral

parasympathetic nervous system

regulates resting functions, such as digesting food or emptying the urinary bladder

Two subdivisions of the PNS

sensory (afferent) and motor (efferent) sensory: transmits electrical signals, called action potentials, from sensory receptors in the body to the CNS The cell bodies of sensory neurons are located near the spinal cord in ganglia (dorsal root ganglia) or ganglia near the origin of certain cranial nerves. motor: transmit action potentials from the CNS to effector organs, such as muscles and glands.

List the components of the peripheral nervous system.

sensory receptors and nerves

CNS consists of

the brain and spinal cord

the brain is located

within the skull, the spinal cord is located within the vertebral canal formed by the vertebrae

the nervous system allows

1. maintaining homeostasis 2. receiving sensory input 3. integrating information 4. controlling muscles and glands 5. establishing and maintaining mental activity

how many pairs of nerves originate from the brain and spinal cord?

12 pairs originating from the brain, cranial nerves 31 pairs of nerves originating from the spinal cord, spinal nerves.

Identify the descriptor that is NOT a structural type of neuron. Pseudo-unipolar neuron Afferent neuron Bipolar neuron Multipolar neuron

AFFERENT NEURON

Match each cell of the nervous system with the correct description.

AFFERENT NEURON- A neuron that transmits action potentials toward the CNS EFFERENT NEURON- A neuron that transmits action potentials away from the CNS towards muscle and glands INTERNEURON- A neuron that conducts action potentials between neurons within the CNS

Types of Glial Cells

CNS Astrocytes -Astrocyte foot processes cover the surfaces of neurons, blood vessels, and the pia mater membrane of the brain and spinal cord. The astrocytes provide structural support and play a role in regulating what substances from the blood reach the neurons. Ependymal cells -Ciliated ependymal cells lining the ventricles of the brain and the central canal of the spinal cord help move cerebrospinal fluid. -Ependymal cells on the surface of the choroid plexus secrete cerebrospinal fluid. Microglia -Microglia are phagocytic cells within the CNS. Oligodendrocytes -Extensions from oligodendrocytes form part of the myelin sheaths of several axons within the CNS. PNS Schwann cells and satellite cells -Neuron cell bodies within ganglia are surrounded by satellite cells. Schwann cells form the myelin sheath of an axon within the PNS.

Neuron Cell Body

Each neuron cell body contains a single, relatively large, and centrally located nucleus with a prominent nucleolus. Extensive rough endoplasmic reticulum (ER) and the Golgi apparatuses surround the nucleus, and mitochondria and other organelles are present. Large numbers of intermediate filaments (neurofilaments) and microtubules form bundles that organize the cytoplasm into different regions. The neurofilaments separate abundant rough ER, called Nissl (nis′l) bodies, which are located primarily in the cell body and dendrites. Nissl bodies are the primary sites of protein synthesis in neurons.

True or False: Neurons consist of a cell body, a single dendrite and multiple axons.

FALSE neurons frequently possess multiple dendrites and generally a single axon.

Str uctural Classes of Neurons

Neurons are classified structurally by the number of cellular projections extending from their cell bodies. Dendrites and sensory receptors are specialized to receive stimuli, and axons are specialized to conduct action potentials.

There are two cell types that make up the nervous system: neurons and glial cells.

Neurons receive stimuli, conduct action potentials, and transmit signals to other neurons or effector organs. Glial (glī′ăl, glē′ăl) cells support and protect neurons and perform other functions. Glial cells account for over half of the brain's weight, and there can be 10 to 50 times more glial cells than neurons in various parts of the brain.

Organization of the Nervous System

Organization of the Nervous System The sensory division of the peripheral nervous system (PNS) detects stimuli and conducts action potentials to the central nervous system (CNS). The CNS interprets incoming action potentials and initiates action potentials that are conducted through the motor division to produce a response. The motor division is divided into the somatic nervous system and the autonomic nervous system. The enteric nervous system is an independent branch of the PNS and is not illustrated in this figure.

somatic nervous system

a voluntary (conscious) division example: allows you to decide to move your skeletal muscles, as when you raise your hand. the CNS generates action potentials that are transmitted by the somatic nervous system to the skeletal muscles in your arm the cell bodies of somatic motor neurons are located within the CNS and their axons extend through nerves to form connections with skeletal muscle cells. each of these connections is called a synapse. synapse - the junction of a neuron with another cell neuromuscular junction, the synapse between a neuron and skeletal muscle fiber neurons can also form synapses with other neurons, smooth muscle cells, cardiac muscle cells, and gland cells.

In the nervous system, the term ____ refers to signal conduction toward the CNS.

afferent

A plexus is

an extensive network of axons and, in some cases, neuron cell bodies, located outside the CNS

efferent neurons carry information _____.

away from the CNS.

autonomic nervous system

an involuntary (unconscious) division example: contractions of smooth muscle, cardiac muscle, and secretion by certain glands. the ANS has two sets of neurons in a series between the CNS and the effector organs. Cell bodies of the first neurons are within the CNS, they send their axons to autonomic ganglia, where neuron cell bodies of the second neurons are located. synapses exist between the first and second neurons within the autonomic ganglia, and the axons of the second neurons extend from the autonomic ganglia to the effector organs. two subdivisions of the ANS: the sympathetic and the parasympathetic division sympathetic = fight-or-flight division parasympathetic = rest-and-digest division

sensory receptors

are the endings of neurons, or separate, specialized cells that detect temperature, pain, touch, pressure, light, sound, odor, and other stimuli.

The star-shaped neuroglia with cytoplasmic processes extending outward from the cell body are _____.

astrocytes

The division of the motor nervous system that is under involuntary control and innervates glands, smooth muscle, and cardiac muscle is the ____ division.

autonomic

glands, smooth muscles, and cardiac muscles are innervated by the ___ division of the motor nervous system

autonomic

the nerve is defined as a bundle of _____.

axons within the peripheral nervous system

A neuron with one axon and one dendrite is a _____ neuron.

bipolar

CNS (central nervous system)

brain and spinal cord

The brain and spinal cord are the two components of the ____.

central nervous system