 Hi, everyone. This is Leah Medwig, your lead course instructor here at ACT. So I want to welcome all of you to our first anatomy and physiology lesson, part one. Today, we're going to talk about the nervous system. So functions of the nervous system. So the nervous system is important for connecting the central nervous system to your organs, to your arms, and to your legs, and to your skin. It also allows the brain and the spinal cord to receive and send information from other areas of the body. So, you know, from your legs and your arms and your organs back to the brain. And it also carries a sensory and motor function to and from the central nervous system. So you're hearing, you're seeing, you're smelling as far as your sense, your senses and then motor functions running, walking, things like that. And then it also helps to regulate involuntary muscle functions like heartbeat and breathing. So the nervous system is classified in two different ways. So it's that there's the central nervous system that consists of the brain and the spinal cord. And this is the integration and command center. And then you have the peripheral nervous system. And the peripheral nervous system consists of 31 pairs of spinal and 12 pairs of cranial nerves. And the peripheral nervous system is what carries messages to and from the spinal cord and the brain to the rest of your body. So the central nervous system, again, of course, consists of the brain. And at its highest level, the brain can be divided into three parts. The cerebellum, the cerebrum, the cerebellum and the brainstem, which you can see here. So the cerebrum or the front of the brain consists of gray matter, the cerebral cortex and white matter at its center. The largest part of the brain, the cerebrum initiates and coordinates movement and regulates temperature. Other areas of the cerebrum enable speech, judgment, thinking and reasoning, problem solving, emotions and learning. And other functions that the cerebrum regulates relate to vision, hearing, touch and other senses. Now the cerebellum can be considered the little brain and because it's a fist-sized portion of the brain, and it's located at the back of the head, below the temporal and occipital lobes and above the brainstem, which we can see here. Its function is to coordinate voluntary muscle movements and to mean posture, balance and equilibrium. And I found this interesting that new studies are exploring the cerebellum's role in thought, emotions and social behavior, as well as its possible involvement in addictions, autism and schizophrenia. Now the brainstem is the middle of the brain and this connects the cerebrum with the spinal cord. The brainstem includes the midbrain, the pons and the medulla. Now the midbrain is a very complex structure with a range of different nuclei in neuron clusters, neural pathways and other structures. And these features facilitate various functions from hearing and movement to calculating responses and environmental changes. The midbrain also contains the area that's most affected by Parkinson's disease. The pons is the original of four of the 12 cranial nerves which enable a range of activities such as tear production, chewing, blinking, focusing, vision, balance and hearing. Also facial expression. So the name for the Latin word for bridge, the pons is the connection between the midbrain and the medulla. And then we have the medulla here and at the bottom of the brainstem, the medulla is where the brain meets the spinal cord. And the medulla is absolutely essential for survival. Functions of the medulla regulate many bodily activities including your heart rhythm, your breathing, blood flow and oxygen and carbon dioxide levels. And the medulla is also responsible for producing reflective activities such as sneezing, vomiting, coughing and swabbling. It's also important to understand lobes of the brain. The frontal lobe that you can see here is the largest of the brain. It's located in the front of the head. So right through here, the frontal lobe is involved in personality characteristics, decision making and movements. Recognition of all smell usually involves parts of the frontal lobe as well. The frontal lobe contains bronchus area, which is associated with speech ability. The parietal lobe as we can see right here is the middle part of the brain. The parietal lobe helps a person identify objects and understand spatial relationships. The parietal lobe is also involved in interpreting pain and touch in the body. The parietal lobe houses Wernicke's area, which helps the brain understand spoken language. Next, towards the back of the head, we have the occipital lobe. And the occipital lobe is the back part of the brain that is involved with vision. And then we have the temporal lobe. And the sides of the brain temporal lobes are involved in short term memory, speech, musical rhythm and some degree of smell recognition as well. And then we have the deeper structures of the brain that consists of the pituitary gland, also known as the master gland. And the pituitary gland is very important as it's what's known as the master gland, which governs functions of other glands in the body that regulate flow of hormones from the thyroid, the adrenals, ovaries and testicles. We have the hypothalamus and the hypothalamus regulates your body temperature. It helps to synchronize sleep patterns, controls hunger and thirst and also plays a role in some aspects of memory and emotion. You have the amygdala and the amygdala helps to regulate emotion and memory. And is also associated with stress and the fight or flight response when someone perceives a threat, which we'll talk about that more in another slide that's coming up. And then you have the hippocampus and that supports memory learning, navigation and perception of space. It receives information from the cerebral cortex and they play a role in Alzheimer's disease. And then we have the penile gland and this responds to light and dark and secret melatonin, which of course helps us regulate our circadian rhythms and our sleep awake cycle. The second part of the central nervous system we have is the spinal cord. Now the spinal cord is a part of the central nervous system and it consists of tightly packed column of nerve tissues that extends downwards from the brainstem through the central canal of the spine and is crucial in facilitating our daily activities. Examples of these key functions include carrying signals away from the brain, which we talked about in the beginning. The spinal cord receives signals from the brain that control movement and autonomic functions. Also, the spinal cord helps to carry information from the rest of the body, your arms or legs or organs back to the brain. And the spinal cord also transmits messages such as sensations of touch, pressure and pain. The spinal cord is also very important in reflex responses. The spinal cord also acts independently of the brain in conducting motor reflexes, which I find to be very fascinating. One example is the patellar reflex, which causes a person's need to involuntary jerk when tapped in a certain spot. I'm sure we all had a doctor do that to us at some point in time. And these functions of the spinal cord transmit the nerve impulses for movement, sensation, pressure, temperature, pain and more. I also wanted to just make a slide regarding spinal cord anatomy. So the spinal cord comprises of three parts. The cervical, which is closer to the neck, the thoracic, which is when you think about your mid back towards where your chest is and the lumbar lower region, the lower back. Three layers of tissue protect the spinal cord, the dural matter, the arachnoid matter and the pia matter, and doctors call these layers meninges. The layers are as follows. So the dural matter is the outermost layer of the spinal cord's meninges and is a tough protective coating. You also have the epidural space between the dura and the arachnoid space is the epidural space. So this is where doctors may insert a local anesthetic to reduce pain during childbirth and some surgical procedures such as those to operate on the longer and abdominal aneurysm. And then you have the arachnoid matter and the arachnoid matter is the middle layer of the spinal cord covering. And then you have the sub arachnoid space and this is located between the arachnoid matter and the pia matter. The cerebral spinal fluid is located in this space. And sometimes a doctor has to sample the cerebral spinal fluid to test for the presence of infection. So like a spinal tap such as meningitis, they can also inject a local anesthetic into this space for some surgical procedures. And then there's the pia matter. This is the layer that directly covers the spinal cord. Next, I just wanted to show a cross section of the spinal cord. So this picture represents if you would take something and you took a knife and you sliced through the spinal cord and you were looking at it like this. So the spinal cord was your hand and you flipped it up like this. This is what we would be looking at here. Key areas of a cross section of the spinal cord include gray matter, which we talked about. And the gray matter is the dark butterfly shaped region of the spinal cord made up of nerve cell bodies. There's the white matter that surrounds the gray matter in the spinal cord and contains cells coding and myelin, which makes nerve transmission occur more quickly. Nerve cells in the gray matter are not as heavily coded with myelin. We also have the posterior root. And this posterior root is a part of the nerve that branches off from back of the spinal column. You also have the anterior root. This is the part of the nerve that branches off from the front of the spinal column, the spinal ganglion. And this is a cluster of nerve bodies that contain sensory neurons. And then you have the spinal nerve and the posterior and anterior roots come together to create a spinal nerve. So now we're going to begin to talk about the peripheral nervous system. So remember in the beginning in the nervous system, we have the central nervous system, which contains or consists of the brain and the spinal cord, which we just talked about. And now we're going to talk about the peripheral nervous system, which is the second half of the nervous system itself. And the peripheral nervous system consists of the sensory division, which consists of nerves that carry information to the central nervous system. And then the motor division consists of nerves that carry information away from the central nervous system. Now the peripheral nervous system is then broken down into the somatic and the autonomic. So the somatic peripheral nervous system controls all the voluntary muscular systems and the process of voluntary reflex arcs. The autonomic nervous system that's part of the peripheral nervous system controls all of your vital functions. So breathing, digestion, heart rate, linking, many of all of these things, you know, we're just not consciously aware of. Back up here. Now backing all the way up, like I said, the peripheral nervous system is then broken down into the somatic and then the autonomic. Furtherly breaking down is the autonomic nervous system. Now the autonomic nervous system subdivisions include the sympathetic and the parasympathetic. And now the sympathetic is responsible for increasing activity in most systems. And this is known as your flight or fight response. So as you can see here in this visual, so your sympathetic nervous system is going to do things. So if you were being chased by a bear and you're very scared and you have that flight or fight response, so your body needs to ramp itself up to get away. So the sympathetic nervous system is going to help with that. It's going to dilate your pupils so you're able to see for you're able to see a longer distance and more and more with more depth. It has to inhibit your salivation and also relaxes your bronchi increases your heart rate. It also inhibits your digestive activity because if you're being chased by a bear, you don't want to be digested. So if you're eating food, you also it stimulates glucose released by the liver. And it stimulates that epinephrine and norepinephrine and that is what you feel when you are afraid. It's that rush of those neurotransmitters and then it also relaxes your bladder. Now the parasympathetic nervous system on the other hand or conversely is responsible for slowing the activity and all of those systems that we just talked about. So this is known as the housekeeping response. So as you can see here, the parasympathetic nervous system will constrict your pupils, stimulate salivation. It will stimulate your digestive activity and it inhibits adrenaline production. So really is what helps you calm down. So when we're talking about the nervous system, we talked about the central nervous system and then the peripheral nervous system. And so we have to talk about neurons and because neurons are all otherwise known as nerve cells. And so neurons are what help to send and receive these signals from your brain down your spinal cord to the rest of your body. And then also back from your body, your limbs, your organs back up to the spinal cord and back to the brain. So they're very, they're very important otherwise, you know, none of this would work without them. So there are three main parts or three main structures of the neuron. And you can see here there's the cell body, which contains genetic information. It helps to maintain the cell neuron structure provides energy to drive activities. Then you have the dendrites that you can see here coming off of the cell body. And these are fibrous roots that branch out from the cell body. They're like a teni. Dendrites receive and process signals from the axons and other neurons. And then you have the axons and an axon is a long-tailed structure. And it joins the cell body at a specialized junction junction called the axon hillock. It's also important to know that many axons are insulated with a fatty substance called myelin. And myelin helps to, helps the axons to conduct electrical signals. Now there are three types of neurons. There's sensory neurons and these help you see, they help you hear, they help you smell, they help you taste and fill things around you. You know, they're sensory neurons, so they help with your senses. And then there's the motor neurons and these allow the brain in the spinal cord to communicate with your muscles, your organs, your glands all over your body. And then you have the interneurons and these are neural intermediaries found in your brain and spinal cord. And they are the most common type of neuron. And they help to pass signals from your sensory neurons and other interneurons to motor neurons and back. So oftentimes they form complex circuits to help you react to external stimuli. So how do neurons work? So neurons work in two main ways. First is by a chemical response through chemical synapses. So in a chemical synapse, the neuron releases chemical messengers called neurotransmitters and these molecules cross the synaptic cleft and bind to other receptors and then in the other neuron and the receiving neuron and the postsynaptic ending of a dendrite. And then the neurons also work by electrical synapses. And so electrical synapses can only excite. So these synapses form when two neurons are conducted by a gap junction and this gap is much smaller than a chemical synapse and is made up of ion channels that help transmit positive electrical signals. Alright, so I hope that you all enjoyed our first anatomy and physiology lesson here. There will be more to come. Please, you know, reach out to me always with any questions that you might have. You know, if there's something that you need me to clarify for you, you know, I was happy to do that. All you have to do is send me an email. And don't forget that you can also schedule office hours with me if you need a little bit more one on one. So thanks so much, everybody. Thanks for listening and we will see you soon. Bye.