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Nervous Coordination

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Biology

What makes a plant a plant and an animal, an animal? An animal feeds on already made (organic matter) food by the producers such as plants. Animals have a specialised nervous system to respond to stimuli (e.g. temperature change) rapidly.

Arguably, some plants also feed on organic matter in the soil or trap insects and have specialised sense organs in their root tips. Plants also react to stimuli in their environment, sometimes even rapidly, like the mimosa pudica plant. Trees, for example, send more resources to their neighbours when they are hurt and communicate via vast underground root networks.

Nervous Coordination an underground root network of wheat grass StudySmarterFigure 1. An underground root network of wheatgrass. Source: Jannoon028, via Freepik

One aspect distinguishing animals from plants is the nervous system. In animals, the nervous system is based on the smallest functional unit, the neurone, which is in charge of the nervous coordination, making fast responses to stimuli in animals the rule rather than the exception (like in plants).

What is the definition of nervous coordination?

Nervous coordination is when all the parts of an organism work together smoothly. There are different types of nervous coordination, such as reflexes (involuntary) and voluntary movement.

Reflexes are an automatic reaction to stimuli entering the body through sensory neurones, which causes muscle cells to contract. You have probably had your reflexes checked by a doctor. A small hammer is used to hit the tendon just below the knee cap (Figure 2) to check the integrity of the nervous system.

Nervous Coordination Checking the knee reflex StudySmarterFigure 2. Checking the knee reflex. Source: turkkub, via flaticon.com.

Voluntary movement is also a reaction to a stimulus - the difference being that voluntary movement requires conscious control of the muscles.

The interplay between the different parts of the body - the eyes, the nerve fibres, the spinal cord and muscles- is referred to as nervous coordination.

What is the role of the nervous system in nervous coordination?

Nervous coordination is ensured by the nervous system, a network in the body of animals that is in charge of communication. All activity in the body is controlled by passing on information via its specialised neurone cells. Nerves are bundles of neurones grouped together.

The two main functions of the nervous system are:

  1. To receive sensory input, process it, and react to it.

  2. To coordinate all the different elements in the body (cells, glands, etc.).

Neurones communicate with each other using synaptic transmission, the majority of which is electrochemical. Most neurones have a gap between them which is bridged via neurotransmitters (e.g., acetylcholine).

Depending on the location or the function of the different nerves, the nervous system can be subdivided again.

The nervous system is quite complex. The divisions aren't always clear cut, especially not over different species, so there is some disagreement between researchers on the exact boundaries of the subdivisions of the nervous system. If in doubt, follow your specific textbook's definitions.

What are the two main subdivisions of the nervous system?

There are two main subdivisions of the nervous system - the central nervous system (CNS) and the peripheral nervous system (PNS) (Figure 3).

The CNS is the centre of control for the entire organism. The central nervous system includes the brain and spinal cord and is responsible for conscious decisions and automatic reactions (reflexes) to stimuli.

The nervous system sends impulses from the peripherals to and from the CNS. The peripheral nervous system then is subdivided by function into the autonomic nervous system and the somatic nervous system. The autonomic nervous system can either be aroused or calmed depending on the response; it is overseen by the sympathetic nervous system (fight-or-flight response) and the parasympathetic nervous system (rest and digest response).

In biopsychology texts, acronyms of the names of the nervous system divisions are used because the full terms are so long. You can remember the different functions for the acronyms of the nervous system divisions like this: C as in Control in the Central nervous system, A as in Automatic in the Autonomic nervous system.

The components of the central nervous system

The CNS includes the brain and the spinal cord.

Defending from the toxins

The CNS has physiological measures to prevent harmful toxins from entering the central nervous system. A specific plasma-like fluid circulates in and around the central nervous system called the cerebrospinal fluid (CSF). CSF has several molecular structures and membranes functioning as security gates, preventing toxins from entering the brain even if they're already circulating in the body in substances such as blood. This means that although the brain and spinal cord connect to the other nerves, the central nervous system is a closed system in itself.

The brain

If you compare the size of other mammals to human brains, the human brain-to-body ratio is the same as that of a mouse or monkey. In other words, if a rat or mouse were as tall as a human, their brains would be the same size as the human brain.

Brains vary from organism to organism - some animals don't have a brain - such as jellyfish (only a loose network of neurones). In contrast, some animals, such as octopuses, have much larger brain-to-body ratios than humans.

However, the major structural difference between humans and other animals is that the brain's surface area, called the cerebral cortex is much larger than other mammals'. The human cortex is folded up, different from a rat's smooth brain. The cerebral cortex's increased surface area makes humans better at integrating information and planning than other animals. Conscious and unconscious decisions are made in the brain.

The spinal cord

The spinal cord is a tubular structure of nerves that extend from the brain into the peripheral nervous system. It reaches from the base of the brain, called the hindbrain, to the second lumbar vertebra in the lower back, about 5 cm above the pelvis.

To enable the body to react quickly, specialised neurones, called relay neurons, carry out unconscious reactions to stimuli known as reflexes. Pulling your hand away from a hot plate, jumping when startled, and your knee jerking up when a doctor hits it are all examples of reflexes. The spinal cord includes the nerve endings that connect to the peripheral nervous system.

The components of the peripheral nervous system

In the PNS, nerves extend from clusters of neurone cell bodies called ganglions into all the muscles and senses in the body. In the PNS, information gets passed to the CNS and from the CNS to muscles and organs. Here, the information processed by the senses (smell, taste, sight) and other receptors (touch, heat, pain) are passed to the CNS for integration.

These two aspects are subdivided into the somatic nervous system and the autonomic nervous system. The divisions of the nervous system run parallel to each other.

Somatic nervous system: This part of the peripheral nervous system communicates with your senses ("soma"). It also is responsible for the voluntary control of your muscles. Any activity that you consciously control, such as moving fingers or speaking, fall under the banner of the somatic nervous system.

Autonomic nervous system: This is the part of the peripheral nervous system in charge of the involuntary and unconscious control of processes of the body such as heart rate, blinking, digestion, relaxation and arousal. It works autonomously and is controlled by a specific part of the brain called the hypothalamus. The autonomic nervous system is divided into two functional units - the sympathetic and parasympathetic nervous systems.

What is a neurone?

Neurones are specialised cells found in the nervous systems of all animals. Their job is to transmit nerve impulses. A mind-boggling 86,000,000,000 (yes, that's 86 billion!) of them form a dense network in the brain, which is why in everyday language, called "brain cells".

They're not only found passing on information in the brain but also throughout the body. Neurones collect information from the outside world through the senses and pass information from the brain to the muscles, which makes all movement and communication possible - for instance, without your brain controlling the movement of your eye muscles, you wouldn't be able to read this text right now.

What's the structure and function of a neurone?

All cells start as embryonic stem cells. Later, these begin to differentiate, meaning they develop different shapes according to their function in the body. Like other animal cells, the neurone has a membrane, nucleus and cytoplasm. But what sets a neurone's cell structure apart is that its form specialises in transmitting information - it generally has an input (the dendrites) and an output (the axon).

Dendrites

Dendrites are branch-like structures that grow from the cell body. The word comes from the Greek "dendritos", meaning tree-like. And like in trees, usually the centre stem develops first, and the newest growth is at the tips. It's here that information is taken in from neighbouring cells.

Axon

The axon is the long part of a neurone along which impulses travel from the cell body to other cells. An axon can be anywhere from a few micrometres to one metre long in humans (in the leg) and up to a whopping 25 metres long in whales.

The nerve impulse always travels away from the cell body via the axon to the thick bits at the end of the axon. They are called terminal buttons or axon terminals. Nerve impulses are unidirectional because of how nerve impulses travel, called the action potential.

The axons can also branch out, but not as much as the dendrites. These branches are called collaterals. Where the axon terminals or buttons meet another cell is a synapse. Nerve impulses are passed on from one neuron to the next via the synapse.

Myelin sheaths

Often, axons are wrapped with a protein and fat compound called myelin. Myelin sheaths insulate the electrical activity of the axon to prevent electrical interference with the other nerve impulses in the closely packed neurone network of the central nervous system. It's similar to the rubber insulation that wraps around the wires in your phone charger cable.

Myelin also speeds up the transmission of nerve impulses, so the more myelin is wrapped around an axon, the faster the electrical impulse is sent to the next cell. It will provide more insulation. Myelin is made up of glial cells wrapping around the axon. The bits of the axon where there are no myelin sheaths are called the nodes of Ranvier.

Types of neurones

There are three classifications of neurones:

  1. Sensory neurones gather information and send it to the brain and spinal cord.

  2. Interneurons (relay neurones) connect one neurone with another in the brain and spinal cord.

  3. Motor neurones send the information back from the brain and spinal cord to the muscles.

Ideally, the three types of neurones work together smoothly. If one of the elements is affected, this will lead to severe illnesses in the organism. The conduction of nerve impulses through these three types of neurones is the process that takes place in all actions, including reflexes.

Let's look at a scenario.

  1. You feel something wet on your cheek. Sensory neurones send a nerve impulse into the body. This is also called an afferent nerve impulse (towards CNS).
  2. Your brain decides how to react. Relay neurones pass nerve impulses from neurone to neurone in the central nervous system. Conscious as well as automatic decisions get made here as to which action to take.
  3. A command is sent to your muscles. They contract to make your head jerk away from your dog. Motor neurones send nerve impulses to the muscles to move away from the surprising stimulus. This is also called an efferent nerve impulse.

You can remember afferent and efferent by; afferent neurons accept nerve impulses (AA), efferent neurones exit the control centre (EE).

What's the function of motor neurones?

Motor neurons make the body move (the muscles) - like a motor moves a machine. They pass nerve impulses from the brain or spinal cord to a muscle or gland. They send impulses to the muscles and make them contract. All life is movement - from the heart beating, the diaphragm moving up and down to create breathing in the lungs, to conscious movement of the muscles in your legs when you walk to the kitchen in the morning.

The brain constantly sends nerve impulses to the body via the motor neurones. These neurones have some of the longest axons in the human body, with some of them stretching from the spine to the foot. Specialised myelin sheaths, called Schwann cells, surround the axons. Schwann cells allow the electrical impulse to travel faster, so they are ideally suited to transmit signals over long distances (from the brain to the big toe) without loss of charge. They can also repair damaged cells, which their counterparts in the central nervous system, the oligodendrocytes, can't.

Damaged motor neurones

When motor neurones are damaged, individuals have problems moving or controlling vital functions such as breathing, chewing and swallowing. Muscle movement and coordination can be impaired, and individuals might have twitching limbs or become paralysed. This is the case with ALS and other motor neurone diseases such as multiple sclerosis.

What is the difference between the endocrine and nervous systems?

The nervous and endocrine systems are responsible for passing information, responding to stimuli, and creating homeostasis (biological balance) in the body.

Table 1. Examples for comparison between nervous and endocrine systems.

Nervous systemEndocrine system
Electrical impulses transfer information.Hormones transfer commands in the form of chemical signals.
Via neurones.Via bloodstream.
The brain and spinal cord regulate the nervous system.Many organs such as testes, and glands such as thyroid.
Voluntary and involuntary actions are controlled.Involuntary control.
Signal transmission is fast.Signal transmission is relatively slow.
Cells interconnected.Hormones are transferred into the bloodstream.
Electrical signals enter cells through the synapse using neurotransmitters.Hormones bind with target receptors and enter specific cells.

Nervous Coordination - Key takeaways

  • Nervous coordination is when all parts of an organism, including cells and organs, work together smoothly. The nervous system is a system of the body in charge of communication.
  • The nervous system has two main divisions: the central nervous system (brain and spinal cord) and the peripheral nervous system (other parts excluding the brain and spinal cord).
  • Nerves are a group of neurones. A cluster of neurone cell bodies is a ganglion. Like other cells, neurones have a cell membrane, cell body and nucleus. Unlike other cells, neurones have dendrites and an axon. There are three types of neurones; sensory, relay and motor neurones.
  • The peripheral system can have voluntary and involuntary responses.

Nervous Coordination

The four main functions of the nervous system are to maintain homeostasis, facilitate learning, control movement and spinal cord reflexes.

The central nervous system is sometimes referred to as the nervous system coordinator, as it controls and coordinates all voluntary and involuntary functions in the body.

The nervous system has three functions - sensing, processing and reacting. When divided by functions, the functions depend on the types of neurones.

Coordination of the nervous system refers to the way neurones ensure that all the cells and organs in the body work together smoothly.

The nervous systems helps coordinate all of the cells and organs in the body so that it functions optimally.

Final Nervous Coordination Quiz

Question

What is a nerve?

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Answer

A group of neurones.

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Question

What is the nervous system?

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Answer

A network in the body in charge of communication.

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Question

Which one of the following statements is not a main function of the nervous system?


  1. Receive, process and react to sensory input
  2. Circulate nutrients
  3. Coordinate different cells and glands in the body


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Answer

Circulate nutrients

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Question

What are the six subdivisions of the nervous system?

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Answer

  1. Central nervous system
  2. Peripheral nervous system
  3. Autonomic nervous system
  4. Somatic nervous system
  5. Sympathetic nervous system
  6. Parasympathetic nervous system

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Question

Which nervous system connects the central nervous system to the muscles?


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Answer

The peripheral nervous system connects the central nervous system to the muscles.

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Question

Which nervous system includes the spinal cord?


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Answer

The central nervous system includes the brain and spinal cord.

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Question

What's the liquid called that is only found in the central nervous system?


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The liquid that can only be found in the central nervous system is called the cerebrospinal fluid.

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What is the main function of the brain?


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Answer

 All conscious and unconscious decisions in the organism are made in the brain.

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Question

Which nervous system division controls reflexes?


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Answer

The central nervous system controls reflexes - specifically relay neurones in the spinal cord.

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Question

Which nervous system division controls voluntary movement?

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Answer

The somatic nervous system controls voluntary movement.

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Question

Which nervous system division controls automatic movements in the body such as your heartbeat and blinking?

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Answer

The autonomic nervous system controls automatic movements.

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Question

Which two responses are controlled by the autonomic nervous system?


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Answer

The autonomic nervous system controls the sympathetic and the parasympathetic nervous systems.

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Question

In general, animals have different types of neurones when compared to humans. 


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Answer

False.

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Only neurones have a cell body, membrane, and nucleus. 


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False.

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The dendrites of the neurone receive the input. 


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True.

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What does the axon do?


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The axon passes on an electric impulse to another cell.

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What's the name of the protein/fat layer around axons which insulates the electrical signal?


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Answer

The protein and fat layer around axons is called myelin.

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What are the three types of neurones?


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Answer

Sensory, inter (relay) and motor neurones.

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Question

You hear an alarm close to you. You startle. Describe how the three functional types of neurones work together to create your startle response.

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Answer

Sensory neurones in your ear transmit a nerve impulse to your central nervous system. A relay neurone sends the nerve impulse to your brain. Motor neurones send an impulse to your muscles that make your muscles contract and startle.

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Which type of neurones connect the brain to muscles?


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Motor neurones.

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What is a synapse?

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A synapse is the contact site where a neurone and another neurone or other cell meet.

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What is synaptic transmission of the chemical synapse?

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Synaptic transmission is when a neurone communicates with another neurone or cell by releasing neurotransmitters into the synaptic cleft.

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What are the two main types of synapses?


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Chemical and electrical synapses.

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Do electrical synapses use neurotransmitters?


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Electrical synapses don't use neurotransmitters, the transmission of electrical charge and molecules is direct.

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Name two advantages of the electrical synapse.


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Impulse is fast and bi-directional.

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Which type of synapse is the most common in humans?


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The chemical synapse.

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The presynaptic membrane is where neurotransmitters bind to let positive or negative ions enter. True or False?


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False.

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Synaptic transmission or neurotransmission is when a neurone communicates with another neurone or cell by releasing neurotransmitters into the synaptic cleft. True or False?


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Answer

True.

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Question

Fill in the blank: Some medication such as SSRIs which are used to treat depression by blocking the reuptake of neurotransmitters into the __________ cell.


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Answer

Presynaptic.

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Fill in the blank: A synapse that transmits Acetylcholine is called ___________.


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Cholinergic.

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Which of the following is not a way in which synapses interface? Choose one correct answer.


  1. Axodendritic
  2. Axosomatic
  3. Axoribosomic
  4. Axo-axonal

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Answer

Axoribosomic

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Which type of connection of a synapse is the most common? Choose one correct answer.


  1. Axodendritic
  2. Axosomatic
  3. Axoribosomic
  4. Axo-axonal

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Answer

Axodendric

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What is the neurotransmitter used at an adrenergic synapse?

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Adrenaline.

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What’s the protein that gap junctions are made of? Choose one correct answer.


  1. Connexon
  2. Connexin
  3. Interstitium
  4. Receptors

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Connexin

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You can look at synapses using any common light microscope. True or False?

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False.

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What is synaptic transmission?

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Synaptic transmission is when a neurone communicates with another neurone or cell by releasing neurotransmitters into the synaptic cleft.

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Do electrical synapses use neurotransmitters for transmission across the synapse?

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Answer

Electrical synapses don't use neurotransmitters, transmission of electrical charge and molecules is direct.

Show question

Question

The presynaptic membrane is where neurotransmitters bind to let positive or negative ions enter. True or False?


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False.

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Synaptic transmission or neurotransmission is when a neurone communicates with another neurone or cell by releasing neurotransmitters into the synaptic cleft. True or False?


Show answer

Answer

True.

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Question

When the opening of an ion channel leads to positive ions streaming into the cell, this is called exhibitory. True or False?


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False.

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When action potential flows into the presynaptic axon terminal, if excitatory neurotransmitters are diffused into the synaptic cleft, this always leads to action potential in the postsynaptic cell. True or False?


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False.

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After diffusing into the synaptic cleft, neurotransmitters enter the postsynaptic cell. True or False?


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Answer

False.

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Question

Fill in the blank. Some medication such as SSRIs which are used to treat depression by blocking the reuptake of neurotransmitters into the ________ cell.


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Answer

Presynaptic.

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What is exocytosis?

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Exocytosis is when the membrane of the vesicles that hold the neurotransmitters fuse with the presynaptic membrane.

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Fill in the blank. The liquid in the synaptic cleft is called _______.

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Answer

Interstitium.

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Question

What is special about transmission across neuromuscular junctions?


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In transmission across neuromuscular junctions, the postsynaptic cell is muscle and they are all cholinergic. 


The successful reaching of the excitatory threshold after synaptic transmission at the neuromuscular junction leads to contraction of the muscle.

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What is the name given to drugs that mimic neurotransmitter?

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Answer

Antagonist/antagonistic.

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Give an example of a drug that interacts with molecular components of the neurone cells.

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Answer

Marijuana.

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Question

What is a nerve impulse?

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Answer

A nerve impulse is a wave of electrical chemical changes across a neuron that assists in the formation of an action potential in response to a stimulus.

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Question

Why is continuous conduction slower?

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Answer

Continuous conduction is a slower mechanism that requires more energy to transmit impulses. It takes longer to conduct signals because it employs a greater number of ion channels to change the neuron's resting state. Continuous conduction is slow as there are always voltage-gated Na + channels opening, and more and more Na + is rushing into the cell. 

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