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AnatomyNervousSystem — Transcript

by Dr. Naveen Jalota, M.D. · 3,933 words · 599 segments · language en · Watch on YouTube

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0:00hello and welcome let's talk today about
0:03the nervous system and nervous tissue
0:04when we talk about the nervous system
0:07the nervous system is considered the
0:08master controlling and communicating
0:11system of the body now we'll visit first
0:15a few functions and then we'll progress
0:18further into the nervous system now when
0:21we talk function of the nervous system
0:22it's got three basic functions and these
0:24three basic functions will include
0:25number one sensory input when we talk
0:28about sensory input sensory input is one
0:31function where the nervous system uses
0:34its millions of sensory receptors to
0:38monitor changes inside and outside the
0:41body the second function then is
0:46integration the nervous system it
0:53processes and it interprets sensory
0:58input and then decides what to do with
1:01it
1:03for example there third then is motor
1:08output motor output and we talk motor
1:10output the nervous system it causes a
1:13response by activating effector organs
1:17when we say effector organs we're
1:19talking muscles and we're talking glands
1:28so here we could see sensory or afferent
1:33neurons are going to be responsible for
1:36conducting signals from our receptors to
1:39the central nervous system the brain in
1:41the spinal cord where then the inter
1:44neurons are Association neurons which
1:48are confined confined into in the CNS
1:51will be responsible for integrating that
1:53information and then they'll dictate out
1:56a motor response via our motor or
1:59efferent neurons which then we said
2:02conduct impulses to our effectors such
2:05as muscles and glands another example
2:11their patient becomes thirsty they see a
2:15glass of water
2:16integration activates those certain
2:19muscles which then are gonna be say we
2:31can see the same thing here when we talk
2:33about the same three basic functions
2:36sensory input integration and motor
2:39output patient is thirsty they see a
2:42glass of water with their sensory
2:43receptors found located inside the eye
2:45the brain says all right well let's
2:48activate the muscles that can pick up
2:50that glass that's there and let's drink
2:53it next let's move to the organization
3:00and we talk about the organization of
3:01the nervous system the division of the
3:03nervous system will see the nervous
3:05system gets divided into the central
3:07nervous system the CNS and the
3:10peripheral nervous system or the pns
3:15let's talk first CNS and then we'll move
3:19over to the pns then when we talk CNS
3:22our central nervous system will see our
3:25central nervous system is going to be
3:28made up of the brain and the spinal cord
3:31it will be made up of the brain and the
3:34spinal cord now when we talk about this
3:38central nervous system this central
3:40nervous system
3:41we can see that organization here as
3:43well we see that same organization here
3:48also I like to use this picture for the
3:52best illustrative purpose so we'll go
3:54from this picture now when we talk about
4:01the brain in the spinal cord if you
4:03recall the brain and spinal cord are
4:04going to be found in the dorsal body
4:05cavity in the dorsal body cavity now
4:10when we talk about this central nervous
4:12system the central nervous system is
4:15going to be the integrating and command
4:21center of this central nervous system of
4:25the nervous system so it is the
4:30integrating and command center of the
4:35nervous system
4:37it receives sensory input and it
4:41dictates a motor response as we
4:44described when we talk about the
4:48peripheral nervous system where the pns
4:50the peripheral nervous system is the
4:52nervous system outside the CNS so
4:57everything outside the central nervous
4:58system which is mainly nerves which are
5:02bundles of axons that are going to be
5:06found extending from the brain and
5:09spinal cord we'll see we have spinal
5:15nerves and cranial nerves that we're
5:17going to go through and we're going to
5:18check out and you'll be responsible for
5:19knowing about now when we talk about
5:23this peripheral nervous system this
5:26peripheral nervous system we can see is
5:28further subdivided it gets further
5:30subdivided into the sensory or the
5:34afferent division and the motor or
5:37efferent division so when we talk about
5:41the sensory or the afferent division
5:45here we'll see the nerve it's made up of
5:48nerve fibres and these nerve fibers here
5:51are going to be responsible for
5:53conveying impulses
5:55to the central nervous system from the
5:59sensory receptors located throughout the
6:01body
6:05now this division is made up of two
6:08fiber types the first fiber type here
6:11are going to be your somatic or your
6:13afferent fibers and second you have your
6:22visceral afferent fibers so first when
6:27we talk so Maddock afferent fibers these
6:30somatic afferent fibers they convey
6:33impulses from your skin skeletal muscle
6:39and also our joints now the visceral
6:45afferent motor the visceral afferent
6:48fibers transmit impulses from our
6:55visceral organs the organs found in the
6:59ventral body cavity now the second
7:08division we have here our motor or
7:11efferent division it transmits impulses
7:15from the CNS to the effector organs to
7:19the muscles and glands and it gets
7:24further subdivided into the somatic or
7:28what we refer to as the voluntary
7:30nervous system and into the autonomic or
7:36involuntary nervous system so when we
7:42talk somatic or voluntary nervous system
7:45you'll see the somatic or voluntary
7:48nervous system it has somatic nervous
7:51and these somatic nerve fibers they
7:55conduct impulses from the central
7:58nervous system to your skeletal muscle
8:04then the autonomic or involuntary
8:08nervous system
8:09it's going to consist of visceral motor
8:14nerve fibers and it's going to regulate
8:20the activity of smooth muscle cardiac
8:24muscle and our glands
8:31now this autonomic nervous system we
8:36cannot control now when we talk about
8:43this autonomic nervous system you can
8:46see it gets further subdivided it's
8:49going to get further subdivided into the
8:50sympathetic division and parasympathetic
8:52division now when we talk sympathetic
8:56division sympathetic division is going
9:01to also be known as the fight-or-flight
9:03division and then the parasympathetic
9:06division is also known as the rest and
9:09digest division now so when we go
9:15through and we talked about the
9:16sympathetic division the sympathetic
9:20division I want you to know it mobilizes
9:23our body's systems it will mobilize our
9:29body systems during activity or under
9:35stress it mobilizes you can see our
9:39body's resources where our body's
9:42systems during activity or under stress
9:47now when the sympathetic division is
9:51activated it mobilizes body systems
9:58during activity so if we talk about the
10:01heart for example it will increase heart
10:04rate if we talk about the lungs and we
10:09talk about basically the bronchi it'll
10:12cause bronchodilation to allow more air
10:15to get it right under periods of stress
10:17or activity so if you're doing some type
10:20of activity or you're under
10:21stress you want to ensure your heart
10:24rate is high that way blood is going
10:26everywhere needs to go you're getting
10:28enough oxygen in right we talk about the
10:30eyes the eyes you're going to have
10:32you'll see a dilation take place pupils
10:36will dilate to allow more light in so in
10:37case you need to be said fight or flight
10:42when we talk about the circulation
10:44making its way to the digestive tract
10:46that circulation is going to be
10:49basically minimized in all that blood
10:52that's supposed to be going there is
10:54gonna be rerouted to are basically
10:56skeletal muscle in case again we need to
10:59fight or flight so you can see there
11:07when we go through and we talk organ by
11:09organ you've got specific changes that
11:11are going to be taking place then when
11:16we talk about rest and digest or this
11:18parasympathetic division when we talk
11:21about this parasympathetic division it
11:23conserves energy it conserves energy and
11:27it promotes housekeeping functions at
11:31rest it conserves energy and it promotes
11:35housekeeping functions at rest
11:37activities basically that occur at rest
11:39such as digestion or right we suppress
11:42and digest so this is where we would be
11:44resting and digesting now here let's go
11:50back and revisit the same examples with
11:52the heart will you have parasympathetic
11:55division activation heart rate is not
11:59going to be increased it will go back to
12:03being what it was at rest when you talk
12:09people's you won't have that dilation
12:12you have a constriction you're resting
12:14and digesting when you talk about the
12:20lungs you won't have that
12:22bronchodilation as you had with
12:26sympathetic activation so that'll go
12:28back to what it was doing resting so you
12:32see all these changes that take place
12:35whenever one system where the other is
12:37activate and you're always going to be
12:39in one state or the other
12:44next then two then the cells of nervous
12:48tissue cells of nervous tissue now we
12:51talk about the cells of the nervous
12:52tissue here we will check out neuroglia
12:54and our neurons so here we've got a nice
12:58table listing all of them and then here
13:01we've got nice illustration depicting
13:03all of them and here we'll go through
13:07each of them then one by one now when we
13:12go through and we talk about our
13:15neuroglia our neuroglia are also known
13:18as our glial cells also known as our
13:21glial cells we have six types we have
13:25four in the central nervous system and
13:27we have two in the peripheral nervous
13:29system now when we talk about neuroglia
13:33of the CNS here's the first cell we'll
13:36talk about in relation to the CNS and
13:38this cell is your astral site when we
13:43talk about astrocytes astrocytes are the
13:45most abundant and most versatile glial
13:48cell they are star-shaped branching seon
13:56enemies is how they're described I think
13:58they all look like cien enemies now
14:01let's talk about their function so here
14:02you can see they have star-shaped we
14:05said right because you can see all these
14:07processes that are radiating from that
14:09cell body where the nucleus is found
14:13these processes what they do is
14:17basically they are going to number one
14:20support and brace and anchor our neurons
14:25those support brace and anchor our
14:28neurons to their nutrient supply lines
14:37now here with them clinging tight
14:42tightly to the nutrient supply lines
14:44this is going to then allow them to
14:48receive all the nutrients that they need
14:52they can extract basically out whatever
14:57they need to send over to the neurons
15:01now these astrocytes they also control
15:04the chemical environment around the
15:06neurons second and what they do is
15:20control the chemical environment around
15:22the neurons so here what they do is they
15:23mop up any leaked potassium ions and
15:28they recapture and recycle released
15:32neurotransmitters and then third they're
15:38going to influence neuronal function
15:42they participate in information
15:45processing in the brain the second cell
15:56type I'd like you to know about that is
15:58the microglial cells these microglial
16:02cells are small ovoid cells with long
16:07thorny processes now the function of
16:12these cells is to monitor the neurons
16:14helped and they also function as
16:18macrophages where they have the ability
16:21to phagocyte eyes dead material
16:26microorganisms or dead neurons or
16:30neuronal debris
16:38next then we have our ependymal cells
16:41our pendel cells their structure is
16:44going to range in shape from squamous to
16:47columnar and many are ciliated and when
16:54you talk about their function they're
16:56going to function by lining the central
16:59cavities of the brain and spinal cord
17:02and we talk lining the central cavities
17:06we're talking about the ventricles they
17:08line the ventricles of the brain in the
17:11spinal cord where they form a permeable
17:14barrier between cerebral spinal fluid
17:19that's going to fill those cavities as
17:23we see here on one side and the fluid so
17:27this fluid and basically this tissue
17:31this CNS tissue so they form a permeable
17:36barrier between cerebral spinal fluid
17:38that fills those ventricles and in the
17:41tissue that's basically found making up
17:46the CNS in the cilia that we see here
17:49it's going to help to circulate that CSF
17:56next then are our or LIGO dentro sites
17:59now we talk about our illegal Dender
18:01sites our illegal Dendera sites their
18:04structure is they look similar to
18:07astrocytes however they have fewer
18:09processes now we talked about
18:13oligodendrocytes their function is that
18:16they produce myelin in the CNS they
18:19produce myelin in the CNS next time
18:27let's talk about the neuroglia of the p
18:29NS when we talk about the neuroglia of
18:31the pms here we have first our satellite
18:35cells so for you saw in the CNS - in The
18:41Pianist satellite cells and schwann
18:44cells now satellite cells they're found
18:48located surrounding the neuron cell
18:50bodies
18:51located in the pns their function is the
18:56same as astrocytes then the Schwann
19:00cells we see here they're found located
19:04surrounding the nerve fibers found
19:08surrounding the nerve fibers in the pns
19:15now when you talk about the function the
19:18function of these Schwann cells is that
19:19they produce myelin for the pns they
19:23produce myelin for the pianist then the
19:29next cell then we have here is our VIP
19:32cell the neuron now when we talk about
19:35our neurons our neurons here's a couple
19:40of different images so we'll use this
19:41image it's a little bit more simpler our
19:43neurons first let's talk characteristics
19:46longevity they have longevity as long as
19:49they receive good nutrition so with good
19:52nutrition they can function for a
19:53lifetime right your neurons we don't get
19:58a transplant at the age of 50 or you
20:00know 40 or anything like that they last
20:04a lifetime they're a mitotic they lose
20:08the ability to divide and cannot be
20:10replaced if destroyed stem cell research
20:15hopefully is going to help with things
20:19like this excusing metabolic rate next
20:24they're very high metabolic rate
20:27requires they require high oxygen and
20:31glucose let's go through the different
20:36regions of the neuron first we have here
20:39what we call the cell body the cell body
20:42is also known as the soma and it
20:46consists you can see of a spherical
20:48nucleus nice spherical nucleus a
20:56conspicuous nucleolus that are both
21:01surrounded them by cytoplasm
21:04the nucleus right contains a nucleus
21:06along with that genetic information the
21:08nobilis is responsible for producing our
21:11RNA as you've learned so then here we
21:14have cytoplasm
21:20basically surrounding those structures
21:24next that here we can see the function
21:27let's talk about the function the
21:28function of the cell body or the
21:29function of the soma is that it is the
21:32major biosynthetic center of the neuron
21:35it contains the usual organelles so when
21:43we say it's the major biosynthetic
21:44center here that means it's responsible
21:49for producing proteins and various types
21:51of neurotransmitters so the nucleus
21:57contains a nucleolus we've talked about
22:00there and genetic information and all of
22:02that here then we have what we call
22:04missile bodies missile bodies are
22:08basically the rough ER the rough
22:10endoplasmic reticulum and what they do
22:13they produce proteins as we mentioned
22:16then we have in here also Nero fibrils
22:20neurofibroma our neural filaments which
22:23are important in maintaining cell shape
22:26and integrity next let's classify our
22:35cell bodies when we classify our cell
22:38bodies they can be classified as either
22:40nuclei or ganglia now when we talk
22:44nuclei when we use the term nuclei we're
22:46talking about clusters collections of
22:50cell bodies in the CNS in the CNS now
22:55when we use the term ganglia we're
22:57talking about clusters of cell bodies in
22:59the p NS in The Pianist next time let's
23:07talk about the various process let's
23:09talk about the processes when we talk
23:11about processes we're going to be
23:13talking about extensions found from the
23:16cell body of
23:17neurons now here we have first dendrites
23:23we'll talk about when we talk dendrites
23:25dendrites their function is that they
23:29are the main receptive or input regions
23:34they provide an enormous surface area
23:37for receiving signals when you talk
23:44about their structure they're short
23:46they're tapering and you can see very
23:52diffuse lis branching extensions like we
24:02said they're the main receptive or input
24:04region they receive the incoming signals
24:06this soul mother cell body can also
24:09receive incoming signals as well it
24:11could serve as basically the region that
24:13receive receives incoming signals too
24:17next then we have the axon and we talked
24:20about the axon the axon is basically any
24:23long you can see process coming off of
24:27that cell body we can also refer to it
24:32as we said the nerve fiber now the
24:37function of the axon is it's the
24:39conducting region it will generate here
24:44at the axon hillock
24:44and then it will transmit then it will
24:50transmit nerve impulses electrical
24:53impulses then when you talk about the
24:57structure of the axon here you have
25:00first the axon hillock this is the
25:03cone-shaped initial region of the axon
25:08it is the cone-shaped initial region of
25:12the axon and this is where the action
25:14potential starts you've got a region
25:18inside called the trigger zone and
25:20that's where you see the action
25:21potential starts next in here we can
25:25appreciate the Schwann cells and how
25:27they're producing myelin
25:30so when we talked first Toledo Dendera
25:33sites we saw here they produced Milan in
25:35the CNS we said so their function was to
25:40produce Milan in the CNS and you can see
25:42one oligo dendera site produces Milan
25:45for many nerve fibers but when we talked
25:50about Schwann cells which also produce
25:54myelin however in the pns you can see
25:57many Schwann cells are required to
26:00produce Milan for wonder fiber many
26:06Schwann cells so this is one chuan cell
26:08producing the mile in that region
26:10another chuan so Prince Milan for that
26:12region another chuan so this is Milan
26:14for that region so here you can see then
26:16when they produced Milan as you can see
26:20from this view as well so here we've got
26:27the Schwann cells they produce the
26:29myelin sheet so here you can see the
26:30Schwann cell is going to basically
26:32encircle one segment and once it
26:37encircle the one segment then it
26:39continues to produce these concentric
26:40circles wrapping around basically you
26:43can see the plasma membrane and then
26:48finally completing myelination where you
26:50have then this outer husk the Neri lemma
26:53formed and then you can see the myelin
26:56sheath right underneath and then here's
26:58the nerve fiber the myelin sheath does a
27:02whitish fatty segmented nerve fiber
27:07covering and the neural mo we said is
27:11the outer husk the outermost layer
27:13basically now what does this myelin
27:21sheath do it helps to conduct nerve
27:23impulses faster helps to conduct nerve
27:25impulses faster so if you were to
27:28compare what we're seeing here this is
27:32not a complete myelination right here we
27:36have unmyelinated regions which we said
27:40are called nodes of Randee a
27:44here what happens is we also spoke of
27:48that action potential gets regenerated
27:50so if we were to compare this the speed
27:54from this nerve fiber to one that's
27:58fully myelinated the one that's fully
27:59monitored its potential is gonna be
28:01traveling faster and the one that's non
28:05myelinated zero myelin and we compare
28:08that to this one here obviously this one
28:10is going to be faster than the one
28:11that's non myelinated so you can see we
28:15can have various types of nerve fibers
28:18depending on central nervous system
28:21peripheral nervous system or where we're
28:22at whether they're myelinated or even
28:24non myelinated next time when we talk
28:28myelin inversion on money we're getting
28:30into white matter in gray matter white
28:32matter is regions of the brain and
28:35spinal cord that contains dense
28:38collections of myelinated fibers which
28:43are grey matter grey matter contains
28:45mostly nerve cell bodies and unny
28:49myelinated fibers so let's scoot along
28:55the neuron and here then we can see that
28:59axon is gonna split and it splits into
29:02the terminal branches splits into the
29:05terminal branches the terminal branches
29:08are branches or extensions from the
29:13opposite end of the cell body from the
29:15opposite end of the axon these terminal
29:20branches then are going to end they're
29:23going to end as the terminal Bouton's or
29:26the axon terminals we see here and
29:29that's the secretory region that's where
29:32they're going to secrete from their
29:33neurotransmitters so here what we could
29:36do is let's magnify that region there
29:38and when we magnify that region there
29:40you can see what we have is we'll have
29:42something that looks like this here's
29:44the axon terminals and then here's the
29:47branches and we'll grab one of these
29:52branches and here we'll see
29:57this is what it actually will look like
30:04kind of enlarged is out like that and
30:07inside of here we're going to have
30:09vesicles and these vesicles are filled
30:14with neurotransmitter right we saw if
30:17we're talking muscle skeletal muscle
30:19that neurotransmitter was acetylcholine
30:23so it depends on where you're at what
30:25you're talking about
30:28now this region in here this is what it
30:31looks like so that's the axon terminals
30:34they're filled with their first let me
30:37tell you the axon terminals are nob like
30:38distal endings of the terminal branches
30:42and they're filled with
30:45neurotransmitters that are found within
30:47vesicles next and we have the term
30:53synapse synapse is going to be a
30:56junction that mediates information
31:00transfer from one neuron to the next or
31:04from one neuron to an effector cell
31:06basically saying here if we have another
31:10neuron let's say or a muscle cell okay
31:13let's draw a muscle cell and we'll put
31:16some striations in there right and so
31:23forth now here is basically the synapse
31:30now so again it's the junction that
31:32mediates information transfer from one
31:35cell over to the next so that's what we
31:41have you're a junction where two things
31:43come together so right here we call it a
31:44synapse
31:51and next let's talk about the
31:54classification of neurons no we can
31:57classify our neurons by structure or by
31:59function so here we can see they are
32:01classified by structure we structurally
32:06classify our neurons as multi polar
32:07neurons which is a typical neuron that
32:10we've been talking about multi polar
32:11because they've got you can see multiple
32:14dendrites multiple processes basically
32:16multiple dendrites and one axon so many
32:22processes extending now our bipolar
32:24neurons have two processes extending
32:27from the cell body a dendrite and an
32:30axon unipolar only one process and that
32:35one process is an accent so according to
32:41structure this is some various types of
32:47neurons according to structure and then
32:53also according to function we talk
32:56according to function we saw that here
32:58then in the beginning where we have
33:01basically sensory neurons inter neurons
33:10and then motor or efferent neurons so
33:15sensory or afferent inter neurons or
33:19Association yards and then motor or even
33:22neurons and last what we have here then
33:28is the classification of these processes
33:31now which process we're going to be
33:33classifying it's going to be you'll see
33:34the axons now when we classify these
33:36axons they get classified according to
33:39two different terms as either tracks or
33:42as nerves now we've already established
33:45the term nerves we said are bundles of
33:47axons in the p NS now i want you to add
33:50they're in the p NS less than our tracks
33:54they're bundles of neuron axons right
33:57neuron processes in the CNS in the CNS
34:03we have various tracks at the scene
34:05they're responsible for controlling
34:06various functions in the body as well
34:09and these tracks can get very specific
34:12to where they're going to be controlling
34:14specific functions in specific areas of
34:16the body it's a very interesting subject
34:18as well

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