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CENTRAL AND PERIPHERAL NERVOUS SYSTEM · Understanding the Brain

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  Speaker 1: Welcome back today. We're going to be talking about the
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  Speaker 1: central and peripheral nervous systems. So the CNS central nervous
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  Speaker 1: system is the brain and the spinal cord. The P
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  Speaker 1: and S is all the nerves. Outside the CNS, they
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  Speaker 1: go to the rest of their body. The somatic nervous
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  Speaker 1: system controls voluntary movement, and the autonomic regulates involuntary functions.
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  Speaker 1: We'll get into those a little bit more later on.
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  Speaker 1: Sympathetic system triggers the fight or flight, while the parasympathetic
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  Speaker 1: promotes rest and digest. So you see a threat, whether
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  Speaker 1: physical or non physical, the sympathetic nervous system kicks in
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  Speaker 1: and back to the HPA access. If you remember that,
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  Speaker 1: the parasympathetic nervous system relaxes, so it's after your calming down.
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  Speaker 1: Meditation will also activate parasympathetic The Bell Mangendi law Bell
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  Speaker 1: mcgendy is m A G E n die law is
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  Speaker 1: the dorsal spinal nerves can very sensory input and the
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  Speaker 1: ventral nerves vd N t r L carry the motor output.
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  Speaker 1: So the dorsal spines are carrying the sensory input. Basically
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  Speaker 1: they're receiving the information from the body. So your hand
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  Speaker 1: touches a hot stove that sends a message to the dorsals,
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  Speaker 1: the dorsal spinal nerves, but they call the afferent a
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  Speaker 1: F F, E, R, E, N T nerves. The other one,
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  Speaker 1: the ventral nerves, carry motor put output out, so they
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  Speaker 1: send back a message to your hand to move it
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  Speaker 1: off the stove, and those are the efferent efferent nerves
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  Speaker 1: E F, F, E, R, N T. That's basically the
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  Speaker 1: Bell mcgindy law. Then we go to action potentials. There
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  Speaker 1: are all nothing electrical signals that propagate along axons, so
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  Speaker 1: action potentials all are non electrical signals that propagate along axons.
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  Speaker 1: Neuroplasticity underlies learning and recovery, so long term potentiation LTP
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  Speaker 1: strengthens connects while LTD weakens them. Autonomic overactivation is central
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  Speaker 1: to anxiety, so the ones that regulate in voluntary functions.
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  Speaker 1: You can see where anxiety can be causing involuntary activity
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  Speaker 1: in the body, while pain signals involve spinal thalamic pathways.
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  Speaker 1: So the nervous system is a communication network. That's the
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  Speaker 1: important thing about the nervous system. There's one part relay,
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  Speaker 1: one part highway, and one part surveillance, so it doesn't
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  Speaker 1: just send messages, and it integrates them, interprets them, and
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  Speaker 1: turns them into behavior, memory, or emotion. So we have
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  Speaker 1: a panic attack or something that starts somewhere in the system.
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  Speaker 1: The central nervous system includes the brain and spinal cor
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  Speaker 1: like we mentioned, and it's in case invertebrate or bone
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  Speaker 1: and protected by cerebral spinal fluid. The cerebral spinal fluid
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  Speaker 1: and the blood brain barrier also protect the brain and
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  Speaker 1: spinal cord. It's the command center. It interprets sensory data,
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  Speaker 1: issues motor commands, stores memory, and orchestrates everything from breathing
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  Speaker 1: to complex decision making. The brain is obviously divided into
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  Speaker 1: the cery broom, brainstem, as cerebellum. As we've learned before
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  Speaker 1: to those three areas. The frontal lobes manage planning and inhibition, language,
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  Speaker 1: and movement. We talked about that while back. The parietal
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  Speaker 1: lobes into great sensory input, touch, pain, temperature, and spatial awareness.
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  Speaker 1: The temporal lobes process auditory input and store long term memory.
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  Speaker 1: If you remember, the temporal lobe also is Wernicky's area.
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  Speaker 1: The frontal lobe is broken over in the excipital lobes.
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  Speaker 1: It handles visual processing, olympic structures like the amignalant hippocampus,
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  Speaker 1: regulated motion, and memory. The brain stem controls automatic functions,
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  Speaker 1: so you're thinking about heartbeat, breathing, alertness, things you don't
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  Speaker 1: have to think about. The cerebellum coordinates movement, balance, and
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  Speaker 1: procedural learning. Procedural learning could be things like riding a bike.
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  Speaker 1: Spinal cord a thick cord of nerve tissue extending from
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  Speaker 1: the brain stem. It's segmented and relays messages between the
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  Speaker 1: brain and the body. The white matter, if you remember that,
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  Speaker 1: transmits the signals rapidly in the myelinated axons, gray matter
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  Speaker 1: processes them. It's organized into dorsal, which means posterior and
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  Speaker 1: ventral anterior roots. So dorsal's posterior ventral is anterior, which
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  Speaker 1: brings us to one of the areas in the triple
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  Speaker 1: p that you'll need to remember is the Bell mcgendi law. Again,
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  Speaker 1: sensory in motor out, so you're taking the information from
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  Speaker 1: the senses, processing it, and then sending a message back out.
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  Speaker 1: The Bell mcgendi law explains this. Spinal nerve organization. Right,
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  Speaker 1: we talked about dorsal roots carry sensory afferent information into
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  Speaker 1: the spinal cord while the ventral roots carry motor efforent
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  Speaker 1: commands out to the muscles. If you have damage to
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  Speaker 1: the dorsal root, it means numbness or sensory loss. If
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  Speaker 1: you have damage to the ventral route, this can cause
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  Speaker 1: weakness or paralysis. Right, because there's no message, there's no
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  Speaker 1: signal or a weak signal going out to the muscles
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  Speaker 1: and to the dorsal root. You won't feel anything because
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  Speaker 1: there's numbness or sensory loss that there's a dorsal root issue.
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  Speaker 1: The distinctions distinction helps in localizing lesions, so it helps
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  Speaker 1: the medical professionals or understand the reflex arc which bypass
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  Speaker 1: the brain entirely. So the peripheral nervous system now this
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  Speaker 1: includes all nerves outside the brain and spinal cord. It's
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  Speaker 1: the link between the central nervous system and the rest
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  Speaker 1: of the body. And it's subdivided into somatic nervous system
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  Speaker 1: and autonomic. As we talked about earlier, it control soomatic
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  Speaker 1: controls the voluntary movement, It transmits sensory information. It operates
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  Speaker 1: through cranial which there are twelve of them, and spinal nerves.
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  Speaker 1: When you reach for your phone or feel cold air
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  Speaker 1: in your skin, this is the system at work, the
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  Speaker 1: autonomic Again regularly, it's heart rate, digestion, respiratory rate, pupil dilation,
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  Speaker 1: and it's also subdivided into sympathetic and parasympathetic nervous systems.
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  Speaker 1: Sympathetic to the fight, flight or freeze. Parasympathetic calms the body, rest, digest,
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  Speaker 1: and restore. Let's look how it affects different parts of
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  Speaker 1: your body. So sympathetic dilates pupils increases heart rate, inhibits
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  Speaker 1: GI gastrointestinal motility, movement, lungs broncho dilation, so it expands it.
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  Speaker 1: Bladder inhibits urination and salivation decreases. So this is where
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  Speaker 1: you get really thirsty. When the sympathetic nervous system is
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  Speaker 1: kicking in for a while, especially the parasympathetic will constrict
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  Speaker 1: the pupils, make them smaller, decrease heart rate, stimulate GI
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  Speaker 1: motility to lead to diarrhea or other issues, so that
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  Speaker 1: broncho constrictions, so it constricts your lungs harder to breathe.
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  Speaker 1: Bladder remotes urination and then salivation is increased. And what
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  Speaker 1: you'll see a lot of significance right after UH an
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  Speaker 1: event that kicks in your sympathetic nervous system. When you
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  Speaker 1: kick your parasympathetic nervous system, it's restoring everything back to normal.
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  Speaker 1: So when I said Brocco constriction of lungs, it isn't
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  Speaker 1: a bad thing. It's actually trying to return it back
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  Speaker 1: to normal. The push pull balance is just it's not
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  Speaker 1: only physiology though, it's psychology, right, So in anxiety it's
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  Speaker 1: orders if you think about it, Sympathetic overactivation does what
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  Speaker 1: what It manifests into a rapid heart rate, tight chest,
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  Speaker 1: disruption in the GI and hypervigilance. So what you're really
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  Speaker 1: you're doing here when you're doing therapies, you're trying to
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  Speaker 1: downregulate the sympathetic nervous system and activate the parasympathetic system
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  Speaker 1: through brief breathwork, grounding or vagal stimulation. And the vegus
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  Speaker 1: nerve is one of the cranial nerves, one of the twelve.
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  Speaker 1: It kind of hits the brake on the sympathet nervous system.
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  Speaker 1: Action potentials and synaptic transmission neurons communicate using electrical impulses
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  Speaker 1: called action potentials. These are all or none signals that
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  Speaker 1: travel along the axon when the neurons threshold potential is reached.
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  Speaker 1: So let me explain a little bit more. It's not
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  Speaker 1: going to be super in depth because they're not going
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  Speaker 1: to get into that in the exam like that, so
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  Speaker 1: we'll just kind of cover some of the basics. Resting
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  Speaker 1: potential is when the neuron is polarized the negative seventy millivolts.
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  Speaker 1: Depolarization is when sodium na plus channels open, rushing positive ions.
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  Speaker 1: In repolarization as potassium K plus exits, restoring the charge
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  Speaker 1: the negative charge, and then the refractory periods neuron briefly
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  Speaker 1: cannot fire again. So the resting potential is already negative.
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  Speaker 1: You're depolarize it by making it positive, and you're repolarize
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  Speaker 1: it by making it negative. The speed of conduction is
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  Speaker 1: increased by myelin and myolin, if you remember, is a
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  Speaker 1: fatty insulating layer produced by glial cells. Gaps in mylin
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  Speaker 1: called nodes of red and allow for slitary conduction, where
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  Speaker 1: the signal jumps between these nodes, similar to skipping stones
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  Speaker 1: across water. At the synapse, the electrical signal becomes chemical.
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  Speaker 1: Neurotransmitters are released from presynaptic vesicles, cross the synaptic left
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  Speaker 1: and bind to receptors on the post synaptic neuron. This
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  Speaker 1: process can either excite or inhibit the next neuron. Disruptions
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  Speaker 1: here are central to psychiatric illness. Think about this for
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  Speaker 1: a second. Schizophrenia is linked to dopamine. We talked about
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  Speaker 1: that as dopamine dysregulation. Depression is linked to impaired serotonin transmission.
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  Speaker 1: So many of the psychotropic or psycho the medications work
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  Speaker 1: by alerting the synaptic chemistry or altering I'm sorry, altering
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  Speaker 1: the chemic street, blocking reuptake, mimking neurotransmitters, or inhibiting degradation.
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  Speaker 1: If you remember with the MLIES neuroplasticity, it's learning and adaptation.
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  Speaker 1: Neuroplasticity is the brain's ability to change its structure and
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  Speaker 1: function based on experience. This happens in multiple forms. The
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  Speaker 1: famous heavy in learning the quote. The famous quote is
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  Speaker 1: Neurons that fire together, wire together, strengthening of synapses that
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  Speaker 1: are used repeatedly long term potentiation. You enhanced synaptic strength
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  Speaker 1: following repeated stimulation, especially in the hippocampus. It underlies learning
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  Speaker 1: and memory. LTD decreased its long term depression, decreased synaptic
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  Speaker 1: strength after under use. This happens a lot as an adolescent.
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  Speaker 1: It helps true unnecessary connection. Neuroplasticity explains how therapy works,
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  Speaker 1: how new habits form, and how people recover from trauma.
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  Speaker 1: It's also why in early intervention matters. Young brains are
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  Speaker 1: very plastic, but even adults can rewire. This is something
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  Speaker 1: we've learned about a decade or two ago that we
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  Speaker 1: can still create new neurons and new rewiring. Plasticity is
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  Speaker 1: seen as an exposure therapy for trauma rewires fear circuits
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  Speaker 1: in the amigla and prefunnel cortex. Stroke rehab builds new
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  Speaker 1: motor pathways, and CBTE changes patterns of thought and emotion
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  Speaker 1: by neural connectivity. Last thing we'll be covering is pain,
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  Speaker 1: the pain pathways and perception. Pain isn't just a sensation.
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  Speaker 1: What happens. It's an experience that has processed through the
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  Speaker 1: spinal thomic tract, which carries no susceptive or pain signals,
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  Speaker 1: as well as temperature signals from the body to the
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  Speaker 1: relay station that we learned the thalmas. Remember the thalmus
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  Speaker 1: it's the relay station, so the pain and temperature signals
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  Speaker 1: go to the thalmis and then the selma seta somatosensory
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  Speaker 1: cortex on top of the brain. There are two types
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  Speaker 1: of pain fibers a delta fast sharp pain like a
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  Speaker 1: paper cut, sea fiber, slow dull burning pain. Chronic pain
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  Speaker 1: involves central sensitization and form of maladaptive plasticity where the
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  Speaker 1: brain amplifies pain signals even in the absence of injury,
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  Speaker 1: and this is tied to mood, memory, and stress, highlighting
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  Speaker 1: the biocycle sol model that occurs with pain. So the
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  Speaker 1: more we understand the nervous system, the better we can
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  Speaker 1: understand both behavior and dysfunction at their root. Every psychiatric
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  Speaker 1: symptom is a story of neural pathways either firing too much,
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  Speaker 1: too little, or out of sync. So that's it for today.
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  Speaker 1: Tomorrow we're going to be covering biological bases of major
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  Speaker 1: psychological disorders, so we'll be looking at depressions, schizophrenia, anxiety, bipolar,
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  Speaker 1: and ADHD to see what the biology says about those
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  Speaker 1: psychiatric issues. Thanks for listening.