chapter 12: nervous tissue

Question 1

Describe the structures of the nervous system

Answer 1

The central nervous system contains the brains and spinal cord

The peripheral nervous system contains: cranial nerves, spinal nerves, enteric plexuses

Question 2

describe the functions of the nervous system

Answer 2

1.Sensory function. Sensory receptors detect internal stimuli, such as an increase in blood pressure, or external stimuli (for example, a raindrop landing on your arm).
2. Integrative function. The nervous system processes sensory information by analyzing it and making decisions for appropriate responses—an activity known as integration.
3. Motor function. Once sensory information is integrated, the nervous system may elicit an appropriate motor response by activating effectors (muscles and glands) through cranial and spinal nerves.

Question 3

what us a nerve and what are they made of?

Answer 3

nerves are made of neurons. a nerve is a bundle of hundreds or thousands of axons outside of the brain or spinal cord

Question 4

are nerves part of the CNS or PNS

Answer 4

PNS

Question 5

neurons vs neuroglia

Answer 5

neurons transmit signals

Neuroglia support, nourish, and protect neurons, and maintain the interstitial fluid that bathes them

Question 6

label the neuron

Answer 6

Question 7

describe the structure of neurons

Answer 7

a fiber is a single axon within the endoneurium. A fascicle is a bundle of fibers within a perineurium. both the endoneurium and the epineurium. a nerve is a bundle of fascicle within an epineurium.

LOTS AND LOTS OF BLOOD VESSELS WITHIN THESE COVERING

Question 8

endoneurium bs perineurium vs epineurium

Answer 8

endoneurium is the innermost one that covers a single axon (called fiber)

perineurium is the middle layer that covers a bundle of fibers (called a fascicle)

the epineurium is the outermost layer that covers a bundle of fascicles

Question 9

what is an axon

Answer 9

An axon is a long, thin, cylindrical projection that often joins to the cell body at a cone-shaped elevation called the axon hillock. It propagates nerve impulses toward another neuron, a muscle fiber or a gland cell

Question 10

describe the sensory division of the PNS

Answer 10

the sensory division of the PNS conveys input to CNS from sensory receptors in the body. provides information about the somatic senses and the special senses.

Question 11

somatic senses vs special senses

Answer 11

somatic senses: tactile, thermal, pain and proprioceptive sensation (position and movement of our body)

special senses: smell, taste, vision, hearing, equilibrium

Question 12

CNS vs PNS

Answer 12

Central nervous system: consists of the brain and spinal cord

CNS processes many different incoming sensory info. Is also the source of thoughts, emotions, and memories. Most signals stimulate muscles to contract and glands to secrete originate in the CNS

Peripheral nervous system: consists of all nervous tissue outside the CNS. Consists of nerves and sensory receptors

Question 13

describe the motor division of the PNS

Answer 13

coveys output from the CNS to effectors (muscles and glands). Division is further subdivided into a somatic nervous system and autonomic nervous system
- Somatic nervous system: conveys output from the CNS to SKELETAL MSCL ONLY because its motor responses can be consciously controlled, the action of this part of the PNS is voluntary
- The autonomic nervous system conveys output from the CNS to smooth muscle, cardiac muscle and glands. Because its motor response not under concious control the action of the ANS is involuntary

Question 14

parasympathetic vs sympathetic vs enteric plexus

Answer 14

parasympathetic: rest, chill, digest

Sympathetic: fight or flight

Enteric plexus: deals with smooth muscle and wall of GI tract. helps regulate the activity of smooth muscle and glands of the digestive canal.

Can function independently (e plexus), but still communicate with and are regulated by autonomic nervous system

Question 15

what do neurons do

Answer 15

have electrical excitability and produce action potentials. These action potential enable neurons to rapidly transmit signals from one cell to another

Question 16

draw out organization of the nervous system

Answer 16

Question 17

what are the different part of a neuron cell body

Answer 17

1. nucleus: surrouned by cytoplasm that contains typical cellular organs
2. Nissl bodies: rough ER and free ribosomes are found here for protein sythnthesis. new poteisn used to replace cellular components, as material for growth neurond and to regenerate damaged axons in PNS
3. neurofibrils (intermediate filaments) give shape and support; microtubules move material between the cell body and axon

Question 18

Answer 18

Question 19

dendrites vs axons

Answer 19

dendrites are the receiving portion of the neurons. they conduct impulses towards the cell body, are highly branched and unmyelinated and have contact with other neurons. (neurofibrils maintain their shape)

axons conduct nerve impulses from the neuron to other cells of the body (neuron, muscles or gland cell)
- conduct impulses away from cell body, end in fine processes called axon terminals; swollen tups called synaptic end bulbs contain vesicles filled with neurotransmitter

Question 20

what is the different in the structural classifications of neurons? what are the 3 different types and what does it look like

Answer 20

Question 21

describe multipolar neurons (location)

Answer 21

it has several dendrites and one axon. They make up the majority of the neurons in CNS (interneurons).
Most neurons in the brain and spinal cord are of this type, as well as all motor neurons

Question 22

describe bipolar neurons

Answer 22

they have one dendrite and on axon. they are found in the retina of your eye, the inner ear and the olfactory area of the brain

Question 23

describe unipolar/ psuedounipolar neurons

Answer 23

consists of a single fused axon and dendrite. the dendrites act as sensory receptors (such as touch, pressure, pain or thermal)

Question 24

what are the functional classification of neurons

Answer 24

1. sensory neurons that relay sensory info to the CNS
2. interneurons (90% of neurons in body) connect sensory to motor neurons in the CNS; involved in
   integration of sensory info
3. motor neurons (efferent) send commands from CNS to target cells

Question 25

Which of the following conduct nerve
impulses from body tissues to the CNS?

a) Sensory neurons
b) Motor neurons
c) interneurons

Answer 25

a) Sensory neurons

Question 26

The dendrites of a neuron:
a) Are the main receiving region of a neuron
b) Secrete neurotransmitters
c) Conduct impulses toward another neuron
d) Do not carry action potentials, only axons do
e) Are only found in the CNS

Answer 26

a) Are the main receiving region of a neuron

Question 27

describe neuroglial cells

Answer 27

“glue” that held nervous tissue together, but do participate in the activities of nervous. make up half of the CNS. They are small and numerous. These cells can divide (gliomas) tend to be be highly malignant and to grow rapidly

Question 28

what are the 4 neuroglial cells in CNS and 2 type of neuroglial cell types

Answer 28

CNS: astrocytes, oligodendrocytes, microglia and ependymal cells

PNS: schwann cells and satellite cells

Question 29

neuroglia vs microglia

Answer 29

Neuroglia are non-neuronal cells that provide support and protection for neurons in the central and peripheral nervous systems [1]. Microglia are specialized macrophages derived from hematopoietic stem cells, are capable of phagocytosis, and protect neurons of the central nervous system

Question 30

describe astrocytes

Answer 30

star shaped cells have many processes and are the largest and most numerous of neuroglia; their processes cover blood capillaries and help form the blood-brain barrier. they provide structural support for neurons and maintain appropriate ion and neurotransmitter concentrations

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 mainly located in white matter.

Question 31

describe oligodendrocytes

Answer 31

processes of oligodendrosites are responsible for forming and maintaining the myelin sheath around CNS axons

Question 32

what is a myelin sheath

Answer 32

multilayered lipid and protein covering around some axons that insulates them and increases the speed of nerve impulse conductions

Question 33

describe microglia

Answer 33

these are phagocytic cells. They remove cellular debris formed during normal development of the nervous system and phagocytize microbes and damaged nervous tissue

Question 34

describe ependymal cells

Answer 34

have microvili and cilia. line the ventricles of the brain and central canal of spinal cord (spaced filled with cerebrospinal fluid).
These cells produce, possibly monitor and assist in the circulation of cerebrospinal fluid. also form blood-cerebrospinal fluid barrier

Question 35

what is the function of cerebrospinal fluid

Answer 35

protects and nourished the brain and spinal cord

Question 36

Which of the following neuroglial cells are
epithelial cells?
a) Astrocytes
b) Oligodendrocytes
c) Microglia
d) Ependymal cells

Answer 36

d) ependymal cells

Question 37

describe satellite cells

Answer 37

flat cells surround the cell bodies of PNS ganglia. Besides providing structural support, satellite cells regulate exchanges of materials between neuronal cell bodies and interstitial fluid

Question 38

What CNS cell are satellite cells analogous to?
a) Astrocytes
b) Oligodendrocytes
c) Microglia
d) Ependymal cells

Answer 38

a) Astrocytes

Question 39

describe Schwann cells

Answer 39

encircle PNS axons; like oligodendrocytes they form the myelin sheath around axons. a single oligodendrocyte myelinates several axons, but each chwann cell myelates a single axon (that lacks myelin sheath).

Schwann cells participate in axon regeneration, which is more easily accomplished in the PNS than in the CNS.

Question 40

Answer 40

Question 41

Answer 41

Question 42

why do axons in CNS display little regrowth after injury

Answer 42

his is thought to be due, in part, to the absence of a neurolemma, and in part to an inhibitory influence exerted by the oligodendrocytes on axon regrowth

Question 43

describe myelination in the CNS

Answer 43

oligodendrocytes myelinate axons in the CNS

cell processes wrap around CNS axons, but the cell bodies do not surround the axons

Question 44

white matter vs gray matter

Answer 44

White matter:
myelinated axons,
where information
travels

Gray matter: neural cell bodies, dendrites, axon terminals, unmyelinated
axons, neuroglial cells; where information is
processed

Question 45

Which of the following does NOT represent a
structural classification of neurons?
a) Multipolar neuron
b) Motor neuron
c) Bipolar neuron
d) Unipolar neuron
e) Myelinated axon

Answer 45

b) Motor neuron
because its not based on appearance

Question 46

Which of the following is NOT a neuroglial
cell of the CNS?
a) Astrocytes
b) Oligodendrocytes
c) Satellite cells
d) Microglial cells
e) All the above are neuroglial cells of the CNS.

Answer 46

c) Satellite cells

Question 47

nucleus bs ganglion

Answer 47

Nucleus = a cluster of neuronal cell bodies in CNS
Ganglion = a cluster of neuronal cell bodies in PNS

Question 48

tracts vs nerves

Answer 48

Tracts = bundles of myelinated axons in CNS (white matter)
Nerves = bundles of axons in PNS

Question 49

If neurons were not excitable, they would
not be able to:
a) Become myelinated
b) Communicate with other neurons
c) Grow
d) Die
e) Migrate within tissue

Answer 49

b) Communicate with other neurons

Question 50

what are the two ways that muscle fibers, cells and neurons communicate with each other (two types of electrical signlas)

Answer 50

1. graded potential which are used for short-distance communication only

2.Action potentials that allow communication over long distances within the body

Question 51

why are nerve cells excitable

Answer 51

Nerve cells are excitable because of
1. membrane potential - cell is “polarized”
◦ The concentration of ions (and net charge) is different inside vs. outside
the cell
2. The presence of specific types of ion channels
More negative ions inside cell and positive ions outside
◦ Potential energy difference (voltage) across the cell membrane at rest is -70 mV

Question 52

what is the energy difference across the cell membrane at rest

Answer 52

-70mV

Question 53

what needs to happen for electrical signals (action potentials) to take place

Answer 53

For electrical signals (action potentials) to take place, ions must flow in and out
of the cell
The flow of ions occurs through ion channels located in the cell membrane
◦ When ion channels are open, they allow the flow of ions
◦ Ions move from an area of high concentration to an area of low
concentration (diffusion)
◦ Ions also move towards an area of opposite charge

Question 54

explain this photo

Answer 54

1. As you touch the pen, a graded potential develops in a sensory receptor in the skin of the fingers.
2. The graded potential triggers the axon of the sensory neuron to form a nerve impulse, which travels along the axon into the CNS and ultimately causes the release of neurotransmitter at a synapse with an interneuron.
3. The neurotransmitter stimulates the interneuron to form a graded potential in its dendrites and cell body.
4. In response to the graded potential, the axon of the interneuron forms a nerve impulse. The nerve impulse travels along the axon, which results in neurotransmitter release at the next synapse with another interneuron.
   5.This process of neurotransmitter release at a synapse followed by the formation of a graded potential and then a nerve impulse occurs over and over as interneurons in higher parts of the brain (such as the thalamus and cerebral cortex) are activated. Once interneurons in the cerebral cortex, the outer part of the brain, are activated, perception occurs and you are able to feel the smooth surface of the pen touch your fingers the conscious awareness of a sensation, is primarily a function of the cerebral cortex.

6.A stimulus in the brain causes a graded potential to form in the dendrites and cell body of an upper motor neuron, a type of motor neuron that synapses with a lower motor neuron farther down in the CNS in order to contract a skeletal muscle. The graded potential subsequently causes a nerve impulse to occur in the axon of the upper motor neuron, followed by neurotransmitter release.
7. The neurotransmitter generates a graded potential in a lower motor neuron, a type of motor neuron that directly supplies skeletal muscle fibers. The graded potential triggers the formation of a nerve impulse and then release of the neurotransmitter at neuromuscular junctions formed with skeletal muscle fibers that control movements of the fingers.
8. The neurotransmitter stimulates the muscle fibers that control finger movements to form muscle action potentials. The muscle action potentials cause these muscle fibers to contract, which allows you to write with the pen.