Nervous system: Structure and function
Definitions & Key takeaways
The human nervous system functions as the control center for everything our body does. It controls voluntary and involuntary activities, including movements, breathing, thinking, digestion, etc. The nervous system consists of the central nervous system, which is made up of the brain and spinal cord; and the peripheral nervous system, which includes all the nerves that connect the central nervous system to the rest of the body. The brain includes the cerebrum, cerebellum, and brainstem, while the spinal cord carries information to and from the brain.
The peripheral nervous system can be divided into the somatic nervous system and the autonomic nervous system, which is further divided into the sympathetic and the parasympathetic systems. The somatic nervous system receives information from sensory organs and controls the voluntary muscles, while the autonomic nervous system receives information and controls the involuntary muscles and glands in organs.
Intro0:00–0:58
The nervous system is involved in nearly everything we do from how we see, to how we walk and talk. Now, the main cells of the nervous system are called neurons.
These make up the brain, the spinal cord, and the peripheral nerves that reach the rest of the body. The nervous system is responsible for detecting and reacting to changes happening both in and outside of the body.
To do that, it gathers sensory signals from the internal and external environment, which are then analyzed. Then, motor signals are sent, which results in an action in response to the change.
So, for example, if you sense pain from touching a hot stove, you jerk your hand away; if you sense your stomach is full, your digestive system starts working harder; if you sense your blood pressure is low, your heart pumps faster.
Okay, let’s start by looking at the neurons that make up the nervous system. These are composed of a cell body, which contains all the cell’s organelles, and nerve fibers that extend out from the cell body.
Cells of the nervous system0:58–1:37
These fibers are either dendrites that receive signals from other neurons or axons that send signals along to other neurons.
The space between where two neurons come together is called a synapse, and that’s where the axon of one neuron releases chemical messengers called neurotransmitters.
These will travel through the synapse and reach the dendrite of the next neuron, causing it to send a signal down its axon.
This is how a signal can pass from neuron to neuron. Now, the nervous system is divided into the central nervous system, including the brain and spinal cord, and the peripheral nervous system, which are the nerves that connect the central nervous system to muscles and other organs in the rest of the body.
Division of the nervous system 1:37–2:08
The peripheral nervous system is divided into the somatic nervous system, which controls the voluntary movement of our skeletal muscles and the autonomic nervous system, which is further divided into the sympathetic and parasympathetic nervous systems and controls the involuntary movement of smooth muscles and glands in our organs.Okay, let's start with the central nervous system.
Central nervous system2:08–4:19
The brain and spinal cord are both covered by the meninges, which are three protective layers of membranous tissue. The inner layer of the meninges is the pia mater; the middle, web-like layer is the arachnoid mater; and the thicker, outer layer is the dura mater.
These first two, the pia mater and arachnoid mater, form the subarachnoid space, which houses the cerebrospinal fluid, or CSF.
CSF is a clear, watery liquid that circulates around the spinal cord and brain, cushioning them from impact and bathing them in nutrients.Now, zooming in, the brain has a few regions.
The largest is the cerebrum, which is divided into two cerebral hemispheres held together by a thick bundle of fibers called corpus callosum.The right cerebral hemisphere controls the left side of the body, while the left cerebral hemisphere controls the right side of the body.
It also controls important functions, like language, learning, emotion, and making decisions. Next, there’s the cerebellum, which sits down at the base of the skull.
The cerebellum helps with coordinating movement, precision, and balance.And finally, there’s the brainstem, which is located right in front of the cerebellum.
The brainstem is made up of three parts—midbrain, pons, and medulla—and it connects to the spinal cord. It also helps regulate blood pressure, breathing, swallowing, coughing, vomiting, and digestion.
The spinal cord is a long rod of nervous tissue that extends down from the brainstem to the lumbar region, or the lower back, and is surrounded by the vertebral or spinal column.
The spinal column is formed by a series of bones called vertebrae, each of which has an opening that lets the spinal cord pass through.
Peripheral nervous system4:19–5:41
Now, the peripheral nervous system consists of twelve pairs of cranial nerves pairs that exit from the skull and 31 pairs of spinal nerves that exit various regions of the spinal cord and connect with the rest of the body.The peripheral nervous system is divided into the somatic and autonomic nervous systems.
The somatic nervous system is made up of sensory nerves; which carry incoming sensory information from the sensory organs, like the eyes, ears, and the skin back to the spinal cord; as well as motor nerves that carry motor information from the spinal cord to the voluntary, or skeletal, muscle.Now, the autonomic nervous system also includes sensory and motor nerves, but they go to involuntary muscles, like those in your heart, and glands, like the ones in your pancreas.
The autonomic nervous system includes a sympathetic and parasympathetic division, which have opposite effects on the body.
The sympathetic nervous system controls functions like increasing the heart rate and blood pressure as well as slowing digestion.
All of this maximizes blood flow to the muscles and brain and can help you either run away from a threat or fight it, which is why it’s also called the “fight or flight” response.
The parasympathetic nervous system, instead, slows the heart rate and stimulates digestion. These effects can be summarized as rest and digest.Like all body systems, the nervous system inevitably undergoes various normal structural changes as we age.
Effects of aging nervous system5:41–7:09
Some of them include a gradual loss of neurons as well as a degeneration of myelin sheaths that surround nerve fibers and changes in neurotransmitter concentration.
These may act together to slow down the conduction of nerve impulses along nerve fibers. In an elderly client, this can manifest as needing more time to respond to sensory stimuli, like sound or light.
And this can be dangerous, especially when a fast reaction is required, like avoiding an obstacle or stepping out of the way of an oncoming car.
So, when caring for elderly clients, it's important to pay special attention to all safety precautions so that potential injuries are avoided.
Another possible effect of aging on the nervous system might be an overall difficulty in retaining new information as well as a very subtle delay in recalling names, dates, or events.
Occasional lapses in short term memory, meaning that of more recent events, like a phone number somebody just mentioned, can be also expected.In contrast, long term memory, which refers to remembering anything that happened more than a few seconds ago, like the name of their spouse, remains unaffected.
The best thing a client can do to maintain a sharp memory over time is to regularly exercise their brain through puzzles; quizzes; reading; and taking up a new hobby, like learning a language or playing an instrument.
Recap7:09–8:13
Alright, as a quick recap... The nervous system includes the central nervous system, which is made up of the brain and spinal cord, and the peripheral nervous system, which includes all the nerves that connect the central nervous system to the rest of the body.
The brain includes the cerebrum, cerebellum, and brainstem, while the spinal cord carries information to and from the brain.
Finally, the peripheral nervous system can be divided into the somatic nervous system and the autonomic nervous system, which is further divided into the sympathetic and the parasympathetic systems.
The somatic nervous system receives information from sensory organs and controls the voluntary muscles, while the autonomic nervous system receives information and controls the involuntary muscles and glands in organs.
The overall function of the nervous system is to receive signals from the internal and external environment and coordinate an appropriate response.
Aging is accompanied by changes in the nervous system, which can lead to slow response times and memory
No notes for this video yet
Try adding a note below