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The nervous system is a network of nerves that connects to all our organs, muscles, and glands. It plays a role in everything we do, from moving our limbs to feeling sensations. Nervous tissue, which is found in the brain, spinal cord, and nerves, is responsible for coordinating and controlling these bodily activities. It stimulates muscle contraction through electrical nerve impulses, which are carried by neurons or nerve cells. These neurons carry messages from the brain via the spinal cord to the muscles, causing them to contract and move. This process is essential for various bodily functions, including breathing, swallowing, and speaking.
| Characteristics | Values |
|---|---|
| How nervous tissue causes action in muscles | Nervous tissue is made up of nerves, neurons, and glial cells. Neurons carry messages from the brain via the spinal cord to the muscles, causing them to contract and move. |
| Types of neurons | Motor neurons, sensory neurons, and interneurons |
| Function of motor neurons | Carry signals from the brain and spinal cord to muscles and glands, helping with movement, breathing, swallowing, and speaking |
| Function of sensory neurons | Carry information from the senses to the brain |
| Function of interneurons | Communicate between motor and sensory neurons, regulating movement and playing a role in learning, thinking, and memory |
| Types of nerves | Sensory nerves, motor nerves, spinal nerves, and cranial nerves |
| Function of sensory nerves | Carry signals to the brain to help with touch, taste, smell, and sight |
| Function of motor nerves | Carry signals to muscles or glands to help with movement and function |
| Function of spinal nerves | Provide sensory function, motor function, or both; control reflexes or involuntary responses |
| Function of cranial nerves | Help with facial expressions, eye movement, and processing smells |
| Role of nervous tissue | Stimulates muscle contraction, creates awareness of the environment, and plays a role in emotions, memory, and reasoning |
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What You'll Learn
- Motor neurons carry signals from the brain and spinal cord to muscles
- Neurons release chemicals, causing muscle fibres to contract
- The nervous system controls voluntary and involuntary actions
- The sympathetic nervous system prepares the body for activity
- Smooth muscle tissue contracts under involuntary nervous control
Motor neurons carry signals from the brain and spinal cord to muscles
The nervous system is responsible for coordinating and controlling many of the body's activities, such as stimulating muscle contraction, creating an awareness of the environment, and playing a role in emotions, memory, and reasoning. It is made up of nerve cells called neurons, which carry electrical signals between the brain, skin, organs, glands, and muscles.
Motor neurons, or motoneurons, are a type of neuron that carries signals from the brain and spinal cord to the muscles. They help the body move and assist with essential functions like breathing, swallowing, and speaking. These neurons comprise complex circuits that allow for both voluntary and involuntary movements through the innervation of effector muscles and glands.
The motor neurons can be further divided into upper and lower motor neurons, which together form a two-neuron pathway responsible for movement. The upper motor neurons originate in the cerebral cortex and travel down to the brain stem or spinal cord. The lower motor neurons begin in the spinal cord and innervate muscles and glands throughout the body. These lower motor neurons play a role in the somatic reflex arc, allowing for quick muscle responses to stimuli.
The nervous system has both voluntary and involuntary parts. The voluntary nervous system, or somatic nervous system, controls movements that we are aware of and can consciously influence, such as moving the muscles in our face, arms, legs, and torso. On the other hand, the involuntary nervous system, or vegetative/autonomic nervous system, regulates processes that occur without conscious influence, such as breathing, heart rate, and metabolic processes.
The nervous system's ability to transmit signals and coordinate activities is dependent on the proper functioning of these motor neurons and the larger network of neurons that make up the nervous tissue.
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Neurons release chemicals, causing muscle fibres to contract
The nervous system is made up of all the nerve cells in the body, or neurons. These neurons transmit electrical signals to and from the brain, skin, organs, glands, and muscles. Motor neurons, in particular, carry signals from the brain and spinal cord to the muscles, helping to control movement and muscle contraction.
Motor neurons release the neurotransmitter acetylcholine (ACh) at a synapse called the neuromuscular junction (NMJ). This is where the motor neuron's terminal meets the muscle fibre. When ACh is released by the neuron, it diffuses across the synaptic cleft and binds to ACh receptors on the motor end plate of the sarcolemma (the motor end plate membrane).
The ACh receptors are chemically-gated ion channels that open when they receive a neurotransmitter signal. This allows Na+ ions to pass through the membrane into the muscle cell, changing the voltage and creating an electrical signal called an action potential. This action potential triggers the contraction of the muscle fibre.
The rate of action potentials fired by the motor neuron determines the amount of force exerted by the muscle. If the neuron fires a single action potential, the muscle twitches slightly and then relaxes. However, if the rate of firing increases, the strength of the muscle contraction increases as well.
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The nervous system controls voluntary and involuntary actions
The nervous system is the body's command centre, controlling and coordinating many body activities and playing a role in everything we do. It is made up of nerve cells called neurons, which send electrical signals throughout the body, including to the brain, skin, organs, glands, and muscles. The nervous system has two parts: the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS includes the brain and spinal cord, while the PNS connects the CNS to other parts of the body.
The nervous system can be further divided into the voluntary nervous system (somatic nervous system) and the involuntary nervous system (vegetative or autonomic nervous system). The voluntary nervous system controls movements that we are aware of and can consciously influence, such as moving the muscles in our face, arms, legs, and torso. These movements involve the brain and are called voluntary actions. Examples include walking, eating, jumping, and running.
On the other hand, the involuntary nervous system regulates processes in the body that occur without our conscious influence, such as breathing, heart rate, digestion, and metabolic processes. It receives signals from the brain and passes them to the body, but it can also send signals back to the brain, providing information such as bladder fullness or heart rate. The involuntary nervous system can react quickly to changes, adjusting bodily processes to adapt. For example, if the body gets too hot, the involuntary nervous system increases blood circulation to the skin and stimulates sweating to cool the body down.
Both the central and peripheral nervous systems have voluntary and involuntary parts. While these parts are closely linked in the CNS, they are usually separate in other areas of the body. The sympathetic and parasympathetic nervous systems, which are part of the involuntary nervous system, typically work in opposition to each other. The sympathetic nervous system prepares the body for physical and mental activity by increasing heart rate, opening airways, and inhibiting digestion. In contrast, the parasympathetic nervous system stimulates digestion, activates metabolic processes, and helps the body relax when at rest. However, these two systems sometimes complement each other rather than working in opposition.
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The sympathetic nervous system prepares the body for activity
The human body is an incredibly complex system, with the nervous system acting as its command centre. The nervous system is made up of nerve cells, or neurons, which carry electrical signals and messages around the body. These messages help us to move, feel sensations, think, learn, and remember.
The nervous system can be divided into the voluntary nervous system, which controls the things we are consciously aware of, and the involuntary nervous system, which regulates processes that we cannot consciously influence, such as breathing and heart rate. The involuntary nervous system, also known as the autonomic nervous system, can be further divided into the sympathetic nervous system and the parasympathetic nervous system.
The sympathetic nervous system prepares the body for physical and mental activity. It is responsible for the "'fight or flight' response, which is activated when we are stressed, in danger, or physically active. When the sympathetic nervous system is activated, it increases our heart rate, strengthens our heart contraction, and dilates our bronchial passages to increase oxygen intake. It also inhibits digestion, slowing down processes in the digestive tract to divert energy elsewhere in the body. The sympathetic nervous system also improves our eyesight by enlarging our pupils to let more light in, and can cause us to sweat more.
The sympathetic nervous system works in conjunction with the parasympathetic nervous system, which is responsible for bodily functions when we are at rest. While the sympathetic nervous system puts our bodies on alert, the parasympathetic nervous system relaxes those systems, stimulating digestion, activating metabolic processes, and helping us to relax.
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Smooth muscle tissue contracts under involuntary nervous control
The nervous system plays a role in everything we do. It is the command centre for the entire body, helping us to think, learn, move, and remember. The nervous system is made up of nerve cells called neurons, which send electrical signals throughout our body, including to our muscles.
Smooth muscle is found throughout the body and serves a variety of functions. It is found in the stomach and intestines, the urinary system, and arteries and veins. Smooth muscle differs from skeletal muscle in that it can contract and be controlled involuntarily. Smooth muscle consists of thick and thin filaments that are not arranged into sarcomeres, giving it a non-striated pattern.
Smooth muscle contraction is dependent on calcium influx. Calcium enters the smooth muscle cell through two processes: depolarization, hormones, or neurotransmitters. Once calcium has entered the cell, it binds to calmodulin, which activates the enzyme myosin light chain kinase (MLCK). MLCK then phosphorylates a regulatory light chain on myosin.
The sympathetic and parasympathetic nervous systems play a role in contracting smooth muscle. The sympathetic nervous system prepares the body for physical and mental activity, while the parasympathetic nervous system is responsible for bodily functions when we are at rest. Smooth muscle cells contract involuntarily to push food through the digestive tract and blood through blood vessels.
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Frequently asked questions
Nervous tissue is made up of nerves, neurons, and glial cells. Neurons carry messages from the brain via the spinal cord to the muscles, causing them to contract and move.
Neurons are nerve cells that carry electrical signals or messages from the brain to other parts of the body.
There are three types of neurons: motor neurons, sensory neurons, and interneurons. Motor neurons carry signals from the brain and spinal cord to the muscles, helping with movement, breathing, swallowing, and speaking. Sensory neurons carry information from the senses to the brain. Interneurons communicate between motor and sensory neurons, regulating movement and playing a role in learning, thinking, and memory.
The nervous system uses neurons to send electrical signals to the muscles, causing them to contract and move. This process is essential for all voluntary and involuntary movements in the body.
The voluntary nervous system controls movements that we are consciously aware of and can influence, such as moving our facial muscles or limbs. The involuntary nervous system regulates processes that we cannot control, such as breathing, heart rate, and metabolic processes.
