chapter 12: Nervous tissue

Question 1

functions of the nervous system

Answer 1

Besides helping maintain
homeostasis, the nervous system is responsible for our perceptions, behaviours, and
memories. It also initiates all voluntary movements
**Sensory, motor and integration of information

Question 2

Describe the organization of the
nervous system.

Answer 2

Made of network of billions of
neurons and even more neuroglia.
** organized into two main subdivisions: the central nervous system and the peripheral nervous system.

devidedinto sensory and motor.
Sensory includes sensory and special sens

Question 3

What makes up the Central nervous system (CNS)

Answer 3

Brain and the spinal cord.
-Spinal cord is connected to the brain through the foramen magnum of the occipital bone and is encircled by the bones of the vertebral column. It contains many neurons.
** CNS processes many different kinds of incoming sensory information. Source of thoughts,
emotions, and memories Mot signals that stimulate muscles to
contract and glands to secrete originate in the CNS.

Question 4

What makes up the Peripheral nervous system (PNS)

Answer 4

anything outside CNS. Nerves and sensory receptor; ganglia, enteric plexuses, and sensory receptors.

Question 5

What is a nerve?

Answer 5

A bundle of hundreds to thousands of
axons plus associated connective tissue and blood vessels that lies
outside the brain and spinal cord.

Question 6

What are sensory receptors?

Answer 6

refers to a structure of the nervous system that monitors changes in the external or internal environment. Examples touch receptors in the skin, photoreceptors in the eye, and olfactory (smell) receptors in the nose.

Question 7

The PNS is divided into

Answer 7

**sensory division- Also called afferent division. Conveys input into
the CNS from sensory receptors in the body. Information includes somatic senses (tactile, thermal, pain, and proprioceptive sensations) and special senses (smell,
taste, vision, hearing, and equilibrium).
** motor divisions - Also called efferent devision. conveys output from the CNS to effectors (muscles and glands).

Question 8

Peripheral Nervous system is divided into

Answer 8

Somatic Nervous system
Enteric Nervous system
Autonomic Nervous system.

Question 9

Describe Somatic Nervous system (SNS)

Answer 9

** includes Somatic and
special sensory
receptors and
somatic sensory
neurons that conveys information TO the CNS. for instance special senses(vision, hearing, smell,taste). Somatic motor neurons on the other hand convey message FROM CNS. Only includes Skeletal muscles which are voluntary

Question 10

Enteric Nervous system (ENS)

Answer 10

-consists of approx. 100M neurons in enteric plexuses that extend most of the length of the gastrointestinal (GI) tract.
-function independently, though to some extent they also communicate with the CNS via sympathetic and parasympathetic neurons (in ANS).
- the neurons monitor chemical
changes within the GI tract as well as the stretching of its walls.
- functions are involuntary.

Question 11

Autonomic nervous system

Answer 11

** Convey information from sensory
visceral organs such as the stomach and lungs,
**motor neurons that conduct nerve impulses from the CNS to smooth muscle, cardiac muscle, and glands.

Question 12

Are actions of the motor sensory neurons in SNS voluntary or involuntary

Answer 12

voluntary

Question 13

Involuntary

Answer 13

Actions of ANS motor neurons.

Question 14

ANS is further divided into:-

Answer 14

**Sympathetic
-“fight/flight”
-Increases HR.
**Parasympathetic
-“Rest and digest”
-decreases HR.

Question 15

the CNS is grouped into 3 functions. Describe each

Answer 15

**sensory
- detect internal stimuli and send this information to the brain and spinal cord via cranial and spinal nerves
**integrative
-Occurs in the cell body.
- analyzing and storing
sensory information and by making decisions for appropriate
responses
**motor
-elicit an appropriate motor
response by activating effectors (muscles and glands) through cranial and spinal nerves. This causes muscles to contract and glands to secrete
:- stimuli is sensed-> info is analyzed and stored for effective response-> Effectors (contraction of glands/secretion by glands).

Question 16

What are the two types of the nervous tissue

Answer 16

**Neurons
** Neuroglia

Question 17

This type of nervous tissue function by sensing, thinking, remembering,
controlling muscle activity, and regulating glandular secretions

Answer 17

neurons

Question 18

Functions of neuroglia

Answer 18

support, nourish, and protect the neurons and maintain homeostasis in the interstitial fluid that bathes them.

Question 19

Neurons

Answer 19

possess electrical excitability,
the ability to respond to a stimulus (change in the environment) and convert it into an action potential (signals travelling along a neuron/muscle fibre).

Question 20

Parts of a neuron

Answer 20

**a cell body- Contains nucleus surrounded by cytoplasm.
-In the cytoplasm, organelles include mitochondria, Rough ER (nissl bodies), lysosomes, Golgi apparatus.
-Cytoskeleton in the cell body includes neurofibrils composed of bundles of intermediate filaments that provide
the cell shape and support, and microtubules which assist in moving materials between the cell body and axon.
** dendrites,- Both The cell body and the dendrites are the receiving or input parts of a neuron.
**an axon conducts nerve impulses toward another neuron, a muscle cell, or a gland cell.
-It contains mitochondria, microtubules, and neurofibrils. Lacks mitochondrion therefore no protein synthesis.

nisslbodies are composed of rough endoplasmic reticulum (ER) and polyrib

Question 21

What is a synapse?

Answer 21

The site where two neurons or a neuron and an effector cell
can communicate.

Answer 22

The tips of
most axon terminals swell into synaptic end bulbs. These bulbshaped
structures contain synaptic vesicles, tiny sacs that store
chemicals called neurotransmitters. The neurotransmitter molecules
released from synaptic vesicles are the means of communication
at a chemical synapse.

Question 23

What is a ganglion

Answer 23

A collection of neuron cell bodies outside the CNS.

Question 24

What is an axon?

Answer 24

A long, thin, cylindrical projection that often joins to the cell body at a
cone-shaped elevation called the axon hillock .

Question 25

where do most nerve impulses Journey start ?

Answer 25

most neurons, nerve impulses arise at the junction of the
axon hillock and the initial segment, an area called the trigger zone,
from which they travel along the axon to their destination

Question 26

Parts of an axon

Answer 26

cytoplasm is known as axoplasm,
surrounded by a plasma membrane known as the axolemma.

Question 27

Where are neurotransmitters stored

Answer 27

Both synaptic end bulbs and varicosities contain many tiny membrane-enclosed sacs called synaptic vesicles that store a chemical called a neurotransmitter.

Question 28

What is a neurotransmitter?

Answer 28

A molecule released from a synaptic vesicle that excites or inhibits another neuron, muscle fiber, or gland cell.cMany neurons contain two or even three types of neurotransmitter

Question 29

transport systems that carry materials from the cell body to the axon terminals and back.

Answer 29

**slow axonal transport that conveys axoplasm in one direction only—from the cell body toward the
axon terminals
*Fast axonal transport capable of moving materials long distance in both direction(towards and away from cell body) and uses proteins that function as “motors” to move materials along the surfaces of microtubules of the
neuron’s cytoskeleton.

Question 30

In fast Axonal transport, describe anterograde and retrograde.

Answer 30

**transport that occurs in an anterograde (forward) direction moves organelles and synaptic vesicles from the cell body to the axon terminals.
**Retrograde (backward)
direction moves membrane vesicles and other cellular materials from the axon terminals to the cell body to be degraded or recycled.

Question 31

classifications of neurons

Answer 31

• structural (according to the number of processes extending from the cell body)
• Multipolar several dendrites and one axon. motor neurons are multipolar.
  -Bipolar neurons have one main dendrite and one axon example retina of the eye, inner ear, olfactory area of the brain.
  -Unipolar have dendrites and one axon that are fused together to form a continuous process that emerges from the cell body. most act as sensory receptors that detect a sensory stimulus such as touch, pressure, pain, or thermal stimuli.
  -Functional classifications
• sensory neurons, interneurons, and motor

Question 32

main difference between multipolar, unipolar and bipolar

Answer 32

**A multipolar neuron has many processes extending from the cell body
**a bipolar neuron has two,
**unipolar neuron has one.cell body is out of the whole cell.

Question 33

What are neuroglia??

Answer 33

-smaller than neurons.
-glia do not generate
or propagate action potentials, and they can multiply and divide in
the mature nervous system.
highly malignant and to grow rapidly

Question 34

Name 6 types of glia(neuroglia)

Answer 34

-Found in the CNS -astrocytes, oligodendrocytes, microglia, and ependymal cells.
-present in the PNS- Schwann cells
and satellite cells.

Question 35

Neuroglia of the CNS

Answer 35

** star-shaped. Largest of the 4
* * There are two types:-
-Protoplasmic
astrocytes have many short branching processes and are found in
gray matter.
-Fibrous astrocytes have many long
unbranched processes and are located mainly in white matter.
-processes of astrocytes make contact with blood capillaries, neurons, and the pia mater.

Question 36

functions of astrocytes

Answer 36

support neurons, protect neurons from harmful substances,play a role in learning and memory, help form BBB, assist with growth and
migration of neurons during brain
development.

Question 37

oligodendrocytes are responsible for

Answer 37

-forming and maintaining the myelin sheath around CNS axons.

Question 38

removes cellular debris
formed during normal development of the nervous system and
phagocytize microbes and damaged nervous tissue

Answer 38

microglia

Question 39

ependymal cells( cuboidal to columnar cells arranged in a single
layer that possess microvilli and cilia)

Answer 39

-produce, possibly monitor, and
assist in the circulation of cerebrospinal fluid. Also form the BBB.

Question 40

Schwann cells

Answer 40

Produce and maintain myelin sheath

Question 41

Satellite cells

Answer 41

Support neurons in PNS ganglia
around a single axon of a PNS neuron; (SAT-i-lı¯t) and regulate exchange of materials
participate in regeneration of PNS axons between neurons and interstitial fluid

Question 42

What does myelinated means?

Answer 42

Axons surrounded by a multilayered lipid
and protein covering, called the myelin sheath.

Answer 43

**ganglion refers to a cluster of neuronal cell bodies located
in the PNS.
* nucleus is a cluster of
neuronal cell bodies located in the CNS.
**a nerve is a bundle of axons
that is located in the PNS.
*Cranial nerves connect the brain to the
periphery, whereas spinal nerves connect the spinal cord to the
periphery.
*A tract is a bundle of axons that is located in the CNS.

Question 44

What section is composed of white matter

Answer 44

White matter is composed primarily of myelinated axons.

Question 45

What section is composed of gray matter

Answer 45

contains neuronal cell bodies,
dendrites, unmyelinated axons, axon terminals, and neuroglia.

Answer 46

If a stimulus causes the membrane to depolarize to a critical level,
called threshold

Question 47

neurons are electrically excitable. They communicate with one another using two types of electrical signals

Answer 47

Graded -used for short-distance communication only
Action potentials -allow communication over long distances within the body

Question 48

Electrical Signals in Neurons
** there are tow types of communicataion types that Excitable cells communicate with each other

Answer 48

Action Potentials (AP) over both long and short distances. Voltage gated
Graded Potentials (GP) Over short distances only.occurs in response to the opening of
a mechanically gated or ligand-gated ion channel.
-production of this two types of action potentials depend on the existence of a resting membrane potential
and certain ion channels.

Question 49

Ion channels found in the plasma membrane that allows the formation of a nerve impulse

Answer 49

**leakage channels- randomly open.
**ligand-gated channels- respond to chemical stimuli (the ligand binds to the receptor.
**mechanically- gated channels- respond to mechanical vibration or pressure stimuli.
**voltage-gated channels- respond to direct changes in membrane potential

Question 50

Graded potentials occur mainly in the dendrites and cell body of a neuron.

Answer 50

**hyperpolarizing graded potential. When the response makes the membrane
less polarized (inside less negative), it is termed a depolarizing
graded potential.
as the charges are lost across the membrane through
leak channels.
**This mode of travel by which graded potentials die out
as they spread along the membrane is known as decremental conduction.

Question 51

Continuous and Saltatory Conduction propagation

Answer 51

-Continuous conduction
occurs in unmyelinated axons and in muscle fibers.
- Nerve impulse propagation in which the impulse “leaps” from one node of
Ranvier to the next along a myelinated axon is saltatory conduction. Saltatory
conduction is faster than continuous conduction

Question 52

Factors that Affect Propagation Speed

Answer 52

-Axon diameter
-Amount of myelination
-Temperature

Question 53

what is a synapse

Answer 53

A synapse is the functional junction between one neuron and another, or
between a neuron and an eff ector such as a muscle or a gland. The two types of synapses are electrical and chemical.