Chapter 11: Autonomic And Motor Systems

The Autonomic Nervous System controls involuntary bodily functions such as heart rate, digestion, and breathing. These functions occur at a subconscious level, meaning that they are not under conscious control. The autonomic nervous system regulates these processes automatically, without us having to consciously think about them. Therefore, the autonomic nervous system is responsible for subconscious functions in the body.

Activation of adrenergic receptors usually produces excitation because adrenergic receptors are primarily involved in the sympathetic nervous system response, which is responsible for the "fight or flight" response. When these receptors are activated, they increase heart rate, blood pressure, and overall arousal, leading to excitation of the body. This response prepares the body for action and allows it to respond to stress or danger.

According to the concept of dual innervation by the autonomic nervous system, if sympathetic activity inhibits pancreatic secretions, then the parasympathetic nervous system should stimulate pancreatic secretions. This is because the autonomic nervous system has two branches, the sympathetic and parasympathetic, which often have opposite effects on target organs. In this case, if sympathetic activity inhibits pancreatic secretions, it means that the sympathetic branch is responsible for inhibiting pancreatic function. Therefore, the parasympathetic branch, which has the opposite effect, should stimulate pancreatic secretions.

The parasympathetic branch of the autonomic nervous system (ANS) is most active when the body is at rest. This branch is responsible for promoting rest and relaxation, conserving energy, and maintaining homeostasis. It helps to slow down heart rate, decrease blood pressure, stimulate digestion, and promote overall calmness and relaxation in the body. The PSN, which stands for parasympathetic nervous system, is another term for the parasympathetic branch of the ANS.

A motor unit refers to a motor neuron and all the muscle fibers it innervates. When a motor neuron is activated, it stimulates multiple muscle fibers to contract simultaneously. This coordinated contraction allows for precise control and movement of muscles. Each motor neuron can innervate multiple muscle fibers, and the group of muscle fibers innervated by a single motor neuron is called a motor unit. Therefore, the correct answer is motor unit.

The motor end plate contains nicotinic cholinergic receptors. Nicotinic receptors are found in the neuromuscular junction and are responsible for transmitting signals from motor neurons to muscle fibers. These receptors are activated by the neurotransmitter acetylcholine, leading to muscle contraction. Muscarinic receptors, on the other hand, are found in other parts of the body and are involved in various physiological processes. Therefore, the correct answer is nicotinic.

The statement is false because the communication between preganglionic neurons and postganglionic neurons in the autonomic nervous system (ANS) is not one-to-one. Preganglionic neurons transmit signals from the central nervous system to ganglia, where they synapse with multiple postganglionic neurons. These postganglionic neurons then relay the signals to various target organs or tissues, allowing for widespread and simultaneous activation or inhibition of multiple effector sites. Therefore, the communication in the ANS is one-to-many rather than one-to-one.

β2 adrenergic receptors have a greater affinity for epinephrine compared to norepinephrine. This means that epinephrine is more likely to bind to and activate β2 adrenergic receptors in the body. This affinity difference is important because it helps explain why epinephrine is often used as a medication to treat conditions such as asthma and bronchospasm, as activation of β2 adrenergic receptors can relax smooth muscles in the airways and improve breathing.

The motor end plate is a specialized region of a skeletal muscle fiber's plasma membrane located at the neuromuscular junction. It is the site where the motor neuron releases neurotransmitters, such as acetylcholine, to stimulate muscle contraction. The motor end plate contains a high concentration of acetylcholine receptors, which bind to the neurotransmitter and initiate the muscle action potential. This allows for the transmission of signals from the nervous system to the muscle fiber, leading to muscle contraction.

Cholinergic neurons are a type of neurons that release acetylcholine. Acetylcholine is a neurotransmitter that is involved in various functions in the body, including muscle movement, memory, and attention. These neurons are found in different parts of the nervous system, such as the brain and the peripheral nervous system. They play a crucial role in transmitting signals between neurons and are involved in regulating various bodily processes.

Each skeletal muscle cell is innervated by a single motor neuron. This motor neuron is responsible for transmitting signals from the brain or spinal cord to the muscle cell, causing it to contract. This one-to-one connection ensures precise control and coordination of muscle movements.

The autonomic nervous system innervates all effector organs except for skeletal muscle cells. This is because skeletal muscle is under voluntary control, meaning it is innervated by the somatic nervous system. The autonomic nervous system controls involuntary actions such as the contraction of cardiac muscle, smooth muscle, and the secretion of glands. Adipose tissue is also under the control of the autonomic nervous system, which regulates its metabolism and blood flow.

Acetylcholinesterase is the enzyme responsible for breaking down acetylcholine in the synaptic cleft. Acetylcholine is a neurotransmitter that is involved in transmitting signals between nerve cells. After acetylcholine has completed its function, it needs to be rapidly degraded to prevent continuous signaling. Acetylcholinesterase breaks down acetylcholine into choline and acetate, which can then be recycled or removed from the synaptic cleft. This ensures that the signaling process is tightly regulated and allows for proper functioning of the nervous system.

Motor neurons are responsible for transmitting signals from the central nervous system to the muscles, allowing for movement. The origin of these motor neurons is the ventral horn of the spinal cord. This region of the spinal cord contains cell bodies of motor neurons, which then send out their axons to connect with muscles throughout the body. The ventral horn is specifically involved in the control of skeletal muscles, which are responsible for voluntary movement. Therefore, the ventral horn of the spinal cord is the correct answer in this case.

The adrenal medulla releases epinephrine into the blood. This is because the adrenal medulla is a part of the adrenal gland, which is responsible for producing and releasing hormones. Epinephrine, also known as adrenaline, is a hormone that is released in response to stress or danger. It helps to prepare the body for a "fight or flight" response by increasing heart rate, blood pressure, and energy levels. Therefore, the adrenal medulla plays a crucial role in the body's stress response by releasing epinephrine into the bloodstream.

Nicotinic and muscarinic receptors are two types of cholinergic receptors. Nicotinic receptors are found in the central and peripheral nervous system, as well as in the neuromuscular junction, and they are activated by nicotine. Muscarinic receptors, on the other hand, are found in various tissues and organs, including the heart, smooth muscles, and glands, and they are activated by the neurotransmitter acetylcholine. These two types of receptors play different roles in mediating the effects of acetylcholine in the body.

Nicotinic cholinergic receptors are ligand-gated ion channels, which means they directly allow the flow of ions across the cell membrane when activated by acetylcholine. They do not activate G proteins. In contrast, muscarinic cholinergic receptors, ᵨ1 adrenergic receptors, ᵦ1 adrenergic receptors, and ᵦ3 adrenergic receptors are all G protein-coupled receptors, which means they activate G proteins upon binding to their respective ligands.

The correct answer is respiratory muscles. The autonomic nervous system controls involuntary actions in the body, such as heart rate, pupil dilation, sweating, and salivation. However, the control of respiratory muscles is not under the autonomic nervous system but rather under the control of the somatic nervous system, which is responsible for voluntary movements.

The motor end plate refers to the specialized region of skeletal muscle that is innervated by a motor neuron. This is where the motor neuron forms a synapse with the muscle fiber, allowing for the transmission of signals from the nervous system to the muscle, leading to contraction. The motor end plate contains numerous acetylcholine receptors, which are responsible for receiving the neurotransmitter acetylcholine released by the motor neuron. This interaction between the motor neuron and the motor end plate is essential for the control and coordination of muscle movement.

When acetylcholine binds to nicotinic cholinergic receptors, it causes depolarization of the motor end plate of a skeletal muscle fiber. This depolarization is known as the end plate potential (EPP). The EPP is a local change in membrane potential that occurs at the neuromuscular junction, where the motor neuron and muscle fiber meet. It is the initial step in the process of muscle contraction, as it triggers the release of calcium ions and the subsequent contraction of the muscle fiber. Therefore, the correct answer is End Plate Potentials (EPP).

The cardiovascular regulatory centers are located in the medulla oblongata. This region of the brainstem is responsible for controlling and regulating various cardiovascular functions such as heart rate, blood pressure, and blood flow. It receives information from various sensors in the body and sends signals to the heart, blood vessels, and other organs to maintain homeostasis and ensure proper functioning of the cardiovascular system.

Acetylcholine and norepinephrine are two primary neurotransmitters in the peripheral nervous system. Acetylcholine is involved in various functions such as muscle contraction, memory, and learning. It is released at the neuromuscular junction, where it stimulates muscle contraction. Norepinephrine is involved in the "fight or flight" response, regulating heart rate, blood pressure, and stress response. It is released by sympathetic nerve fibers and acts as a stress hormone. These neurotransmitters play crucial roles in transmitting signals between nerve cells in the peripheral nervous system.

Terminal boutons are structures found at the end of axon terminals of a motor neuron. These boutons store and release a neurotransmitter called acetylcholine. Acetylcholine is responsible for transmitting signals between neurons and muscle cells, allowing for muscle contraction and movement. Therefore, the presence of terminal boutons suggests that the motor neuron in question is involved in transmitting signals to muscles, likely controlling voluntary movement.

The ANS, also known as the Involuntary Nervous System, controls involuntary bodily functions such as heart rate, digestion, and breathing. It operates automatically, without conscious control, and is responsible for maintaining homeostasis in the body. The ANS consists of two divisions: the sympathetic nervous system, which prepares the body for "fight or flight" responses, and the parasympathetic nervous system, which promotes relaxation and restorative processes. Together, these divisions work to regulate various bodily functions and maintain internal balance.

The correct answer is varicosity. A varicosity is a swollen portion along the length of an axon terminal where neurotransmitters are released from a postganglionic neuron. It contains numerous synaptic vesicles filled with neurotransmitters that are released into the synaptic cleft to transmit signals to the next neuron or target cell.

Muscle fibers are innervated by only one motor neuron, meaning that each motor neuron is responsible for activating a specific group of muscle fibers. This arrangement allows for precise control and coordination of muscle movements. When the motor neuron is activated, it signals the muscle fibers it innervates to contract, leading to the desired movement. This one-to-one innervation ensures that the muscle fibers receive a direct and specific command from the motor neuron, allowing for efficient and targeted muscle contractions.

Sympathetic postganglionic neurons are adrenergic because they release the neurotransmitter norepinephrine (also known as noradrenaline). Adrenergic neurons are part of the sympathetic division of the autonomic nervous system and play a role in the "fight or flight" response. Norepinephrine acts on adrenergic receptors in target tissues, leading to various physiological responses such as increased heart rate, dilation of blood vessels, and increased blood pressure.

A decrease in cAMP is associated with the a2 adrenergic receptor. Adrenergic receptors are classified into alpha and beta subtypes, with the a2 adrenergic receptor belonging to the alpha subtype. Activation of the a2 receptor inhibits adenylate cyclase, leading to a decrease in the production of cyclic adenosine monophosphate (cAMP). This decrease in cAMP has various physiological effects, such as decreased smooth muscle relaxation, decreased insulin secretion, and decreased release of norepinephrine.

Adrengergic neurons are responsible for releasing norepinephrine. Norepinephrine is a neurotransmitter that plays a role in the body's "fight or flight" response, increasing heart rate, blood pressure, and alertness. Adrengergic neurons are found in various parts of the brain and spinal cord, and their activation can have widespread effects on the body.

The correct answer is neuromuscular junction. The neuromuscular junction is the synapse between a motor neuron and a skeletal muscle cell. It is a specialized connection where the motor neuron releases neurotransmitters, such as acetylcholine, which bind to receptors on the skeletal muscle cell and initiate muscle contraction. This junction allows for the transmission of signals from the nervous system to the muscles, enabling voluntary movement.

Cholinergic neurons are those that release the neurotransmitter acetylcholine. In the peripheral nervous system, cholinergic neurons include parasympathetic preganglionic and postganglionic neurons, sympathetic preganglionic neurons, and motor neurons. These neurons play a role in various physiological processes such as regulating heart rate, digestion, and muscle movement.