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chapter 8 the nervous system Flashcards

1
Q

What are the functions of the nervous system?

A

detect changes and feel sensations

initiate responses to changes

organize information and store it

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2
Q

what does the nervous system consist of?

A

the CNS- brain and spinal cord

the PNS- cranial and spinal nerves and the ANS

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3
Q

What are nerve cells called?

A

neurons or nerve fibers

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4
Q

What are dendrite cells?

A

conduct nerve impulses towards the cell body

neurons may have hundreds of dendrites

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5
Q

What are Axons?

A

conduct nerve impulses away from the cell body

Neurons only have one axon

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6
Q

Where are neuron cell bodies found?

A

in the CNS

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7
Q

What kind of cells are found in the CNS?

A

Oligodendrocytes and microglia

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8
Q

What kind of cells are found in the PNS

A

schwann cells and myelin sheath

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9
Q

What are schwann cells?

A

consists of axons and dendrites

grow to surround the neuron processes, enclosing them in layers of Schwann cell membrane

produce myelin sheath around axons

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10
Q

What is the myelin sheath?

A

a phospholipid that electrically insulated neurons from one to another

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11
Q

What are the nodes of Ranvier?

A

spaces between adjacent Schwann cells or segments of the myelin sheath

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12
Q

What is the function of the Nodes of Ranvier?

A

parts of the neuron cell membrane that depolarize when an electrical impulse is transmitted

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13
Q

What is the neurolemma?

A

the nuclei and cytoplasm of the Schwann cells are wrapped around the outside of the myelin sheath

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14
Q

What is the function of neurolemmas?

A

essential for the regeneration of neurons

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15
Q

What are oligodendrocytes?

A

produce myelin sheaths around axons of the CNS

one of the neuroglia

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16
Q

Why doesn’t the regeneration of neurons happen in the CNS?

A

There are no Schwann cells present which means there is no neurolemma

This is why severing of the spinal cord results in permanent loss of function

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17
Q

What are the microglia?

A

another kind of neuroglia

they are phagocytes- they clean up cellular debris and damaged cells and phagocytize pathogens

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18
Q

What are asrocytes?

A

another kind of neuroglia

they provide framework for the migrating neurons that will form the brain

help regulated localized blood flow within the brain

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19
Q

What do Astrocytes contribute to?

A

Blood-Brain Barrier- which prevents potentially harmful waste products in the blood from diffusing out into brain tissue

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20
Q

What are disadvantages of the blood-brain barrier?

A

some useful medications cannot cross it

antibodies produced by lymphocytes cross only with difficulty

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21
Q

What is Polarization?

A

a neuron not carrying an impulse

more Na+ ions outside cell/ more K+ ions and negative ions inside the cell

results in positive charge outside of cell membrane and negative charge inside cell

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22
Q

What is depolarization

A

entry on na+ ions

reversal of charges on either side of the membrane

outside now has a negative charge and inside has positive charge

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23
Q

What is repolarization?

A

K+ ions exit the cell

this restores positive charge outside and the negative inside

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24
Q

What does the term action potential refer to?

A

depolarization followed by repolarization

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25
What do the sodium and potassium pumps do?
they return Na+ ions outside and K+ ions inside the neuron is now ready to respond to another stimulus and transmit another impulse
26
What is saltatory conduction?
in a myelinated neuron only the nodes of Ranvier depolarize increase speed of impulses
27
How do nerve impulses differ?
they are all exactly the same but they different effects depending on on their various destinations (muscles,glands, or other neurons)
28
What is a nerve impulse considered as?
like a switch or signal that activates the cell, tissue, or organ of its destination
29
What is the synapse?
the small gap between the axon of one neuron and the dendrites or cell body of the next neuron
30
What happens during the process of a synapse?
A neurotransmitter carries the impulse across a synapse and is then destroyed by a chemical inactivator or absorbed
31
Many synapses are termed excitatory why?
the neurotransmitter causes the postsynaptic neuron to depolarize transmits an electrical pulse
32
Why are some synapses termed inhibitory?
the neurotransmitter causes the postsynaptic neuron to hyperpolarize
33
What is hyperpolarization?
the neuron membrane becomes even more positive outside as K+ ions leave the cell or Cl- ions enter the cell does not transmit an electrical impulse
34
What groups are neurons classified as?
Sensory neurons, motor neurons, and interneurons
35
What are sensory neurons?
carry impulses from receptors to the CNS may be somatic (from skin, skeletal muscles, joints) or visceral (from internal organs)
36
What are receptors?
structures that detect external or internal changes and generate impulses that travel along afferent neurons to the CNS
37
Sensory neurons from receptors in skin, skeletal muscles and joints are called?
somatic
38
Sensory neurons from receptors in internal organs are called?
visceral sensory neurons
39
What are motor neurons (efferent neurons)?
carry impulses from the CNS to effectors may be somatic (to skeletal muscle) or visceral (to smooth muscle, cardiac muscle, or glands)
40
What are the two general type of effectors?
muscles-contract or relax glands-secrete or do not
41
Sensory and motor neurons make up what system?
The PNS
42
Visceral motor neurons make up what system?
Autonomic nervous system (ANS)
43
What are interneurons?
carry only sensory or motor impulses, or to integrate these functions found entirely within the CNS some interneurons are concerned with thinking, learning and memory
44
What is a nerve?
a group of axons and/ or dendrites of many neurons, with blood vessels and connective tissue
45
What are sensory nerves?
are made only of sensory neurons ex: optic nerves-vision olfactory nerves-smell
46
What are motor nerves?
made only of motor neurons autonomic neurons are motor nerves
47
What is a mixed nerve?
contains both sensory and motor neurons Ex: peripheral nerves
48
What is a nerve tract?
groups of neurons within the CNS aka white matter
49
What is the function of the spinal cord?
transmits impulses to and from the brain, and integrates the spinal cord reflexes
50
Location of the spinal cord?
within the vertebral canal extends from the foramen magnum to the disc between the 1st and 2nd lumber vertebra
51
What is the H- shaped gray matter of the spinal cord?
contains cell bodies of motor neurons and interneurons
52
What is the external white matter of the spinal cord?
myelinated axons and dendrites of interneurons
53
What do the ascending tracts do?
carry sensory impulses to the brain
54
What do the descending tracts do?
carry motor impulses away from the brain
55
What is within the central canal?
cerebrospinal fluid and is continuous with the ventricles of the brain
56
How many pairs of spinal nerves?
31 pairs 8 cervical pairs 12 thoracic pairs 5 lumbar pairs 5 sacral pairs 1 small coccygeal pair
57
What is the cauda equina?
the lumbar and sacral nerves that extend below the end of the spinal cord
58
What does each spinal nerve have?
two roots: neurons entering or leaving the spinal cord
59
What is the dorsal root?
is made of sensory neurons that carry impulses into the spinal cord
60
What is the dorsal root ganglion?
an enlarged part of the dorsal root that contains the cell bodies of the sensory neurons
61
What is the ventral root?
the motor root made of the axons of motor neurons carrying impulses from the spinal cord to muscles or glands
62
What is a reflex?
involuntary response to a stimulus, automatic action
63
What is the reflex arc?
pathway that nerve impulses travel when a reflex is elicited
64
What does the reflex arc consist of?
1.Receptors 2.Sensory neurons 3.Central nervous system 4.Motor neurons 5.Effector
65
What is the stretch reflex?
a muscle that is stretched will contract patellar reflex is used clinically to determine whether the nervous system is functioning properly
66
What are flexor reflexes (withdrawal reflexes)
a painful stimulus will cause withdrawal of the body part
67
What are the ventricles of the brain?
four cavities: two lateral ventricles , the third ventricle, the fourth ventricle each contains a choroid plexus that forms cerebrospinal fluid
68
What is the function of the medulla?
regulates the vital functions of heart rate, breathing, and blood pressure regulates reflexes of coughing, sneezing, swallowing and vomiting
69
What are within the pons?
respiratory centers that work with those in the medulla
70
What is within the midbrain?
centers for visual reflexes, auditory reflexes, and righting (equilibrium) reflexes
71
What is the function of the cerebellum?
regulates coordination of voluntary movement, muscle tone, stopping movements and equilibrium contributes to sensations involving texture and weight
72
What are the functions of the hypothalamus?
-produces ADH -produces oxycotin -produces releasing hormones -regulated body temp -regulates food intake -integrates the functioning of the ANS -regulates body rhythms
73
What are the functions of the thalamus?
-groups sensory impulses as to body part before relaying them to the cerebrum -awareness of pain but inability to localize -suppresses unimportant sensations to permit concentration -contributes to alertness and awareness and to memory
74
What is the the cerebrum?
largest part of the brain consists of two hemispheres separated by the longitudinal fissure
75
what is the corpus callosum?
a band of 200 million neurons that connects the right and left hemispheres of the cerebrum
76
What is the cerebral cortex?
the surface grey matter of cerebrum which consists of cell bodies of neurons and is folded extensively into convulsions
77
What is the internal white matter of the cerebrum?
consists of nerve tracts that connect the lobes of the cerebrum to another and other parts of the brain
78
What is within the frontal lobes?
motor areas-initiate voluntary movement premotor area- regulates sequence of movements for learned skills prefrontal area- for aspects of social behavior broca's motor speech area- regulates the movements involved in speech
79
What is within the parietal lobes?
general sensory area- feels and interprets the cutaneous senses and conscious muscle sense taste area- extends into temporal lobe, for sense of taste speech areas- (left hemisphere) for thought before speech
80
What is within the temporal lobes?
auditory areas- for hearing and interpretation olfactory areas- for sense of smell and interpretation speech areas- for thought before speech
81
what is within the occipital lobes?
visual areas-for vision interpretations areas- for spatial relationships
82
what is within the association areas?
in all lobes for abstract thinking, reasoning, learning, memory, and personality. The hipocampi are essential for the formation of memories neural plasticity- the ability of the brain to adapt to changing needs
83
What is the basal ganglia?
small masses of gray matter within the cerebral hemispheres regulate accessory movements such as gestures and facial expressions as well as muscle tone
84
What are meninges?
the connective tissue membranes that cover the brain and spinal cord three layers
85
What are the three layers of meninges?
outermost layer- dura matter; lines the skull an vertebral canal middle layer- arachnoid membrane web like strands of connective tissue inner layer- pia matter' on surface of the spinal cord and brain
86
What is the subarachnoid space?
between the arachnoid and pia matter that contains cerebrospinal fluid
87
How is cerebrospinal fluid (CSF) formed?
formed continuously in the ventricles of the brain by choroid plexus, from blood plasma
88
How does CSF circulate?
from the ventricles to the central canal of the spinal cord and to the cranial and spinal subarachnoid spaces
89
How is CSF reabsorbed?
from the cranial subarachnoid space through arachnoid villi into the blood in the cranial venous sinuses rate of reabsorption equals the rate of production
90
How does CSF contribute to the CNS?
as tissue fluid, it brings nutrients to the CNS neurons and remove wastes products. CSF also acts a shock absorber to cushion the CNS
91
Function of the cranial nerves?
concerned with vision, hearing and equilibrium, taste and smell and man other functions within the head and viscera
92
What is the Autonomic nervous system?
part of the PNS consists of motor neurons to visceral effectors has two divisions sympathetic and parasympathetic
93
What does an ANS pathway consist of?
two neurons that synapse in a ganglion preganglionic neurons- from the CNS to the ganglia postganglionic neurons- from the ganglia to the effectors
94
Sympathetic division
most sympathetic ganglia are in two chains just outside the vertebral column dominates during stressful situations;responses prepare the body to meet physical demands
95
parasympathetic division
parasympathetic ganglia are very near or in the visceral effectors dominates in relaxed situations to permit normal functioning
96
What is Acetlychloline?
the transmitter released by all preganglionic neurons both sympathetic and parasympathetic inactivator is cholinesterase
97
What do sympathetic postganglionic neurons release?
norepinephrine inactivator is catechol-o-methyl transferase (COMT) or monoamine oxidase (MAO)

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