Unit 8 - Nervous System Flashcards
1
Q
What are the four functions of the nervous system?
A
- sensory functions: detect sensations such as hot, cold, touch, pain, pressure
- integrative functions: gathering information, processing information, sending a response to alter/control the body
- motor functions initiate and regulate movement of body parts
- regulate secretions from glands
2
Q
What is a nerve cell called?
A
neuron
3
Q
What do neurons produce?
A
neurotransmitters which are chemical messengers
4
Q
Where do neurotransmitters send signals to?
A
other neurons
5
Q
What is synapses?
A
the short distance of travelling of a message from a neuron to a neurotransmitter to another neuron
6
Q
What does the short travel of neurotransmitters allow for?
A
quick reaction of the system
7
Q
What are the drawbacks to limited supplies of neurotransmitters?
A
does not allow it to sustain individual activities for a long period of time
8
Q
What can the nervous system be divided into?
A
central nervous system (CNS)
- brain
- spinal cord
peripheral nervous system (PNS)
- cordlike nerves that link the CNS with the rest of the body
9
Q
What does the PNS do?
A
gathers information about the external and internal environments
10
Q
What does the CNS do?
A
receives and integrates information from PNS and initiates appropriate movements of body parts, glandular secretion or behaviour in response
11
Q
What are the different parts to the neuron?
A
- dendrites
- central body/soma/perikaryon
- axons
- myelin sheath
12
Q
What are dendrites?
A
short, multi-branched projections extending from the central cell body
13
Q
What are the functions of the dendrites?
A
- receive impulses from other neurons
- conducts the impulse to the central body
14
Q
What can the dendrites be referred to as?
A
afferent processes because they conduct impulses toward the cell body
15
Q
What is the function of the central body?
A
- receives information or pulse brought by dendrites
- process or integrates the impulse
- sends this impulse on to the axon depending on the strength of the signal
16
Q
What are the functions of the axons?
A
- other type of process from the neuron cell body
- conduct nerve impulses away from the cell body toward another neuron or another cell
- each neuron gives rise to only one axon which usually branches
17
Q
What is the main difference in cells between dendrites and axons?
A
dendrites - contain granules
axons - granules are absent
18
Q
How are neurons classified?
A
morphologically according to their number of nerve processes
19
Q
What are the different types of neurons?
A
unipolar neurons
bipolar neurons
pseudo unipolar neurons
multipolar neurons
20
Q
What is a unipolar neuron?
A
only one process, seen during development and can not be seen in adult vertebrate
21
Q
What is a bipolar neuron?
A
contains two processes, one dendrite and one axon (common in sensory systems)
22
Q
What is a pesudo unipolar neuron?
A
have their single dendrite and axon fused so as to give the appearance of a single process
23
Q
What is a multipolar neuron?
A
have a number of dendrites in addition to their single axon, most neurons are multipolar in nature
24
Q
What is the myelin sheath and what is it made out of?
A
- sheath of fatty substance that covers the axons
- is made of the cell membranes of specialized glial cells called oligodendrocytes in the brain and the spinal cord and schwann cells in the nerves outside of the brain and spinal cord
25
What are the two types of glial cells that a myelin sheath can be made out of?
oligodendrocytes - brain and spinal cord
schwann cells - nerves outside
26
How many oligodendrocytes take up the axon?
multiple oligodendrocytes, lined up end to end to cover the entire length of the axon
27
What are the gaps in the myelin sheath called
nodes of ranvier
28
What do te oligodendrocytes and the nodes of ravier do?
work together to enhance the speed of conduction of nerve impulses along the axon
29
What do neuroglia cells do?
provide mechanical support, protection and nutrients to the nerve cells
30
What are astrocytes?
a type of neuroglia cells, they are cells with long projections that surround the blood vessels within the CNS
31
What are the functions of astrocytes?
contributes to the blood-brain barrier which prevents the brain of blood toxic substances in the blood, and harmful compounds from the brain to the bloodstream
32
What are microglia?
a type of neuroglia, the smallest, act as a immune cell of the CNS
33
What is the function of microglia?
fight off and phagocytize viruses, bacteria, and other foreign invaders, they remove cellular debris to facilitate wound repair
34
What are ependymal cells?
a type of neuroglia, line all the cavities within CNS
35
What does the CNS deal with?
central or cranial/caudal axis of the body
36
What are the two types of PNS nerves?
cranial nerves: PNS nerves that originate from the brain
spinal nerves: PNS nerves that originate from the spinal cord
37
What are afferent vs efferent nerves?
afferent nerves: carries nerve impulses towards CNS
- includes sensory nerves which carry sensations from sensory receptors in the skin and other parts of body
efferent nerves: carries nerve impulses away from the CNS towards muscles and other organs
- called motor nerves as will cause skeletal muscle contractions
38
What is the autonomic nervous system?
sensory neurons - afferent (carry towards CNS)
- includes involuntary nerve function
motor neurons - efferent (carry away from CNS)
- includes contraction of intestines, change in heart rate in response to a threat, stimulate secretions of digestive juices etc.
38
What is the somatic nervous system?
sensory neurons - afferent (carry towards CNS)
- includes conscious or voluntary control of skeletal muscles
motor neurons- efferent (carry away from CNS)
- includes impulses sent from receptors in the muscle, skin, eye and ear to CNS which are consciously perceived by the brain
38
What is happening inside/outside the cell at resting state of the neuron?
Inside: higher concentration of potassium ions, lower concentration of sodium ions, presence of negative charges inside (e.g. proteins, Cl-)
Outside: higher concentration of sodium ions, lower concentration of potassium ions, presence of negative charges outside
38
When is the cell membrane of a neuron polarized?
keeping the sodium on the outside and the potassium on the inside, the cellular membrane separating the two is said to be polarized, it has two distinct poles of ions on either side of the membrane
39
What does the sodium-potassium pump do in the resting state of the neuron?
- specialized structure to help maintain cell resting state
- pumps Na2+ to the outside and pumps K+ to the inside
- pumps against the concentration gradient
40
What controls the ion flow through the channels in the polarized membrane of the neuron?
gates
41
What happens during the excitability of neurons?
- an impulse from an adjoining neuron or from a specific type of external stimulus stimulates a neuron
- it will cause the opening of the sodium channel
- the sodium channel will allow only the passage of Na+
- the Na+ will enter the neuron by a passive diffusion from outside (high conc) to inside (low conc)
42
What occurs during depolarization of a neuron?
opening of the sodium channels and the sudden influx of many sodium ions into the cell, the sodium influx results in the loss of the two distinct poles of sodium and potassium on either side of the membrane
43
How do the charges of the membrane change during depolarization?
- neuron goes from a negatively charged resting membrane potential to a net positive charge, this is due to the positive sodium ions flowing into the cell
44
What is action potential?
significant change in electric charge from negative to positive during depolarization
45
What occurs to the membrane during the beginning of repolarization?
- Na+ channels are closing, and K+ are opening
- K+ flow out of the cell, and the net charge is returning to negative direction
- membrane potential starts to decrease to the resting membrane stage
46
What occurs to the membrane during repolarization?
- more K+ outside the cell than inside, the converse is true for Na+
- Na/K pump will correct this by pumping K+ inside the cell and pumping Na+ outside the cell
- sufficient outflow of K+ ions restored net negative charge to inside of cell
47
What occurs to the membrane during the refractory period?
- brief period during and after a neuron has generated a nerve impulse and it cannot generate another impulse
- while the Na+ channel is opened, or if the K+ ions is flowing rapidly back into the cell, there won't be a second polarization
- if a stimulus happens during the refractory period, it will diet out
48
What are the steps to the conduction of action potential in an unmyelinated neuron?
1. at resting stage membrane is polarized
2. after a stimulus, the Na+ enters the cells
3. it causes a depolarization of a small portion of the membrane
4. Na+ diffuses into the surrounding areas
5. positive charges stimulates the opening of the adjacent Na+ channels
6. more Na+ enters, and these areas of the membrane are now depolarized
49
What is saltatory conduction?
the conduction of action potential in an myelinated neuron, the channels at each node of ranvier get depolarized at different rates because of the distance
50
What are the advantages of saltatory conduction?
- allows the action potential to travel a lot faster, as it will not travel across the entire membrane, but rather jump from node to node
- it also saves energy as a lot less sites for Na+ entrance appears (only at nodes)
- this means that less Na+ will be required to be pumped out by the Na+/K+ pump, saving energy
51
What are synapses?
specialized junctions where information is exchanged between neurons or between a neuron and the cell or cells that it innervates
52
What is the synaptic knob?
ending terminal of a neuron
53
What can the postsynaptic cell be?
not necessarily need to be a neuron. it can be a muscle, fiber, organ or tissue
54
What is milk fever or hypocalcemia?
not enough calcium at influx of neuron and neurotransmitters are lost and therefore action potential is lost
55
Are the cell membranes of the presynaptic and postsynaptic neurons in immediate contact?
no
56
What is the synaptic cleft?
small but distinct separation between the presynaptic and the postsynaptic neurons
57
how does information exchange occur between synapses?
release of chemical neurotransmitter from the presynaptic neuron
58
What does an individual neuron contain?
vesicles with a neurotransmitter
59
How does synaptic transmission work?
- the action potential arrives at the terminal end of the presynaptic neuron and changes the membrane potential
- it opens the calcium gates at the terminal and Ca2+ enters the cell by diffusion
- once Ca2+ enters the cell, it will trigger the exocytosis of the vesicles containing neurotransmitters
- Neurotransmitters bind to cell membrane receptors on postsynaptic neurons or target organs
- the binding changes the postsynaptic membrane permeability to ions
- produces a change in the membrane potential of the postsynaptic neuron
60
What happens if there is a Ca2+ deficiency in synapses?
deficiency results in no Ca2+ influx and thus no release of neurotransmitter into synaptic cleft, results in no stimulation of postsynaptic membrane across the synaptic cleft
61
What is the most common situations that calcium deficiency is observed in farm animals?
milk fever - common in dairy cows at parturition
62
What can most neurotransmitters be classified as?
amino acids or polypeptides
63
What are the two types of neurotransmitters?
excitatory: causes Na+ influx through postsynaptic membrane, which depolarizes the postsynaptic neuron
inhibitory: causes Cl- influx and/or K+ outflux through postsynaptic membrane, inside the cell will become more negatively charged, moving the charge within the postsynaptic cell farther away from the threshold
64
What is hyperpolarization?
cells are more negative than they are in their resting state
65
What do inhibitory neurotransmitters do?
allows the negatively charged chloride ions (Cl-) to enter the postsynaptic cell and allows potassium (K+) ions to leave the cell, making the inside of the cell more negatively charged
66
What forms the white versus the gray matter of the CNS?
gray - aggregates of neuronal cell bodies form the gray matter
white - rich in myelinated axons and glial cells
67
What are the four sections of the brain?
- cerebrum
- cerebellum
- diencephalon
- brainstem
68
What are some features of the cerebrum?
- largest part of the brain in domestic animals
- constitutes the area of the brain responsible for those functions associated with higher-order behaviours
- learning, reasoning and intelligence
69
What is the cerebral cortex vs the white matter?
cerebral cortex - made out of gray matter, the top layer of the brain
white matter - beneath the cortex
70
What is the surface of the cerebrum covered in?
wrinkles which serve to increase the area of the cerebral cortex therefore making more room for gray matter
71
What is the cerebrum divided into?
right and left cerebral hemispheres
72
What is each hemisphere in the cerebrum divided into?
divided by sulci into lobes?
73
What are sulci?
divided the brain into lobes
74
What are some features of the cerebellum?
- located caudal to the cerebrum
- second largest component of the brain
- allows the body to have coordinated movement, balance, posture, and complex reflexes
- also involved in motor memory
75
What is a feature of the diencephalon?
serves as a nervous system passageway between the brainstem and the cerebrum?
76
What are the three major structures in the diencephalon?
- thalamus: regulates sensory inputs to the cerebrum
- hypothalamus: interface between the nervous system and endocrine system
- pituitary: endocrine gland that regulates production and release of hormones throughout the body
77
What is the brainstem the connection of?
connection between the rest of the brain and the spinal cord
78
What are the three parts of the brainstem?
medulla oblongata
pons
midbrain
79
What is the most primitive part of the brain?
brainstem
80
What is the function of the brainstem?
involved in autonomic control functions related to breathing, circulation and digestion
81
What are the meninges?
set of connective tissue layers that surround the brain and spinal cord
82
What is the function of the meninges?
supply nutrients and oxygen to the superficial tissues of the brain and spinal cord
83
What are the parts of the meninges?
pia mater
arachnoid mater
subarachnoid space
dura mater
84
What is the function of the pia mater in the meninges?
innermost very thin layer than layers in the tissue brain
85
What is the arachnoid mater in the meninges?
slightly thicker than the pia mater
86
What is the subarachnoid space in the meninges?
place underneath the arachnoid mater, and contains the cerebrospinal fluid, its chemical composition is also involved in autonomic functions
87
What is the dura mater in the meninges?
thicket layer of all meninge's layers that sits on top of the arachnoid mater
88
What is the spinal cord?
the caudal continuation of the brainstem outside the skull
89
What is the function of the spinal cord?
conducts sensory information and motor instructions between the brain and the periphery of the body
90
Do meninges surround the spinal cord?
yes
91
What are dorsal and ventral roots?
present in the spinal cord
dorsal roots: contain sensory fibers
ventral roots: contain motor fibers
92
What is the function of the dorsal and ventral roots?
spinal cord sends off dorsal and ventral nerve roots that link the spinal cord with the peripheral nerves
93
What is the autonomic nervous system?
part of the nervous system that regulates activity in viscera and other structures not normally under voluntary control
94
What are the two components to the autonomic nervous system?
sympathetic nervous system
parasympathetic nervous system
95
What is the sympathetic nervous system?
- prepares the organism to meet a stress
- produce a combination of physiologic changes
96
What is the parasympathetic nervous system?
- its activity leads to digestion and storage of fuel molecules
- acts to bring the organism to a state of rest
97
What is the action of the sympathetic nervous system?
fight or flight instincts
- raising the heart rate
- constriction of blood vessels
- trigger the release of glucose from the liver
98
What is the action of the parasympathetic nervous system?
rest and digest actions
- digestion process
- expulsion of waste
- maintenance-related processes
99
Where do the nerves for the sympathetic nervous system emerge from?
thoracic and lumbar vertebral regions in the back
100
How many neurons do motor nerves of the autonomic nervous system consist of?
two neurons
101
What are the functions of the two neurons of the motor nerves in the ANS?
preganglionic neuron - has its cell body in the brain or spinal cord, it extends its axon out from the CNS to a cluster of neuronal cell bodies outside of the CNS called ganglion
postganglionic neuron - carries the impulse from the ganglion to the target organ
102
What is the difference between parasympathetic and sympathetic in the length of pre and postganglionic neurons?
sympathetic
preganglionic neurons are short and originates in the thoracic and lumbar segments of the spinal column, it connects to a ganglia that forms the sympathetic ganglion chain
parasympathetic
preganglionic neuron is long, it travels directly to its target organ, where it synapses with a short post ganglionic neuron in the target organ
103
What is the sympathetic ganglion chain?
when the preganglionic neuron attaches to ganglia
