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The brain is a complex organ that controls thought, memory, emotion, touch, motor skills, vision, respiration, and every process that regulates the human body. It is the central computer that controls all the functions of the body, while the nervous system is like a network that relays messages back and forth from the brain to different parts of the body. The cerebrum, the biggest part of the brain, controls voluntary muscles, which move when you want them to. The cerebellum, on the other hand, controls balance, movement, and coordination (how your muscles work together). The brain stem controls involuntary muscles, such as those in the heart and stomach, and is responsible for vital functions such as breathing, digestion, and blood circulation.
| Characteristics | Values |
|---|---|
| Brain weight | 3 pounds |
| Brain composition | 60% fat, 40% water, protein, carbohydrates, and salts |
| Brain regions | Gray matter, white matter |
| Brain functions | Controls thought, memory, emotion, touch, motor skills, vision, respiration, temperature, hunger, heart rate, digestion, and every process that regulates the body |
| Brain control | Sends messages to the muscles to contract and move |
| Brain parts | Occipital lobes, parietal lobes, temporal lobes, cerebrum, cerebellum, brain stem |
| Brain nerves | Cranial nerves, oculomotor nerve, trochlear nerve, trigeminal nerve, abducens nerve, facial nerve, vestibulocochlear nerve, vagus nerve, accessory nerve, hypoglossal nerve |
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What You'll Learn
The cerebrum controls voluntary muscles
The brain is a complex organ that controls thought, memory, emotion, touch, motor skills, vision, breathing, temperature, hunger, and every process that regulates our body. It is one of the two main parts of the central nervous system, which also includes the spinal cord.
The cerebrum, located at the front of the brain, is the largest part of the brain and plays a critical role in controlling voluntary muscles. It comprises gray matter (the cerebral cortex) and white matter at its center. The cerebral cortex, which is the outer surface of the cerebrum, is divided into two halves or hemispheres: the left and right hemispheres. These two halves communicate with each other through a structure called the corpus callosum, which is a collection of nerve tissue that transmits signals from one side of the brain to the other.
Each hemisphere of the cerebrum has four sections, or lobes: the frontal, parietal, temporal, and occipital lobes. These lobes control specific functions, including movement. For example, the frontal lobe, located in the front of the head, is involved in personality characteristics, decision-making, and movement. It contains Broca's area, which is associated with speech ability. The parietal lobe, located in the middle part of the brain, helps individuals identify objects and understand spatial relationships. It also plays a role in interpreting pain and touch in the body and houses Wernicke's area, which helps the brain understand spoken language. The occipital lobe, located in the back of the brain, allows individuals to process and interpret visual information from the eyes.
The cerebrum sends signals to the muscles, telling them what to do when they need to be used. This is how it controls voluntary movements. For example, when picking up a pencil off a table, the cerebrum sends signals to the muscles in the arms, and the cerebellum helps calculate and control the movements so that the hand goes right to the pencil. The cerebellum also manages conscious thoughts, planning, and actions, such as deciding to be physically active, choosing what to eat, or setting aside time to see a healthcare provider.
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The brain stem controls involuntary muscles
The brain is a complex organ that controls thought, memory, emotion, touch, motor skills, vision, breathing, temperature, hunger, and every process that regulates our body. The brain and spinal cord comprise the central nervous system. The brain itself is not a muscle, but it does contain blood vessels and nerves, including neurons and glial cells.
The brain stem is a critical component of the brain, acting as an automatic control center for several involuntary actions, including heartbeat, breathing, blood pressure, and many reflexes. It is also a pathway for impulses travelling between the body and the rest of the brain. For example, the medulla oblongata, located just above the spinal column, regulates rhythmic breathing and variations due to changing body needs, such as running. Similarly, the pons, a horseshoe-shaped section of nerves, is involved in both voluntary and involuntary movements.
While voluntary muscles are controlled by the motor cortex, a zone of the cerebrum located behind the frontal lobe, involuntary muscles are controlled by other regions of the brain, such as the hypothalamus. The hypothalamus, located deep within the brain, controls involuntary muscle contractions in organs like the stomach wall during digestion.
The brain stem also plays a role in regulating sleep and alertness through the reticular formation, which can be influenced by stimulants and daily activity levels. Additionally, the brain stem is involved in coordinating breathing patterns through the coordination of the medulla and pons, which manage purposeful alterations in breathing, such as blowing out candles or warming hands by exhaling.
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The oculomotor nerve controls pupil response and eye movement
The oculomotor nerve, also known as Cranial Nerve III, is responsible for controlling pupil response and eye movement. It is one of the three nerves that control the muscles that move the eye. The oculomotor nerve is a pair of nerves, one for each eyeball, that branch out from the area in the brainstem where the midbrain meets the pons.
The oculomotor nerve helps to adjust pupil width, also known as pupil constriction, to let more or less light into the eye. This is known as the pupillary light reflex. When the eyes adjust to sudden light changes, the oculomotor nerve is the muscle that reacts. Signals travel through the optic nerves to tell the brain when it's too bright or dim, and the brain then tells the oculomotor nerve to adjust the pupil's width. The oculomotor nerve supplies input to the sphincter pupillae muscle, which is arranged in a circular pattern around the pupil. When the muscle fibres of the sphincter pupillae are activated, they contract and constrict the pupil, reducing its size.
The oculomotor nerve also controls other eye movements. Its branches connect to muscles on multiple sides of the eyeballs, delivering movement commands from the brain to those muscles. These include the levator palpebrae superioris, which raises the upper eyelid, and the superior tarsal muscle, which keeps the eyelid elevated. The oculomotor nerve is involved in accommodation, which is the ability to continuously focus on an object as it moves towards or away from you. It also controls scanning eye movements, known as saccades, which are quick back-and-forth eye movements that help to scan the field of view.
The oculomotor nerve is vulnerable to various conditions due to its path through different brain areas. When it is damaged or not functioning correctly, it can result in oculomotor nerve palsy or dysfunction, characterised by a 'down and out' position of the eye and a dilated pupil.
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The trochlear nerve controls muscles in the eye
The brain is a complex organ that controls thought, memory, emotion, touch, motor skills, vision, breathing, temperature, hunger, and every process that regulates our body. It is not a muscle, but it does contain blood vessels and nerves, including neurons and glial cells.
The trochlear nerve, also known as the fourth cranial nerve, cranial nerve IV, or CN IV, is a cranial nerve that controls muscles in the eye. It is one of the ocular motor nerves that control eye movement. The trochlear nerve is the smallest of the cranial nerves, yet it has the longest intracranial course. This is because it is the only nerve to exit the brainstem dorsally.
The trochlear nerve innervates a single muscle: the superior oblique muscle of the eye. This muscle is the longest and thinnest of the extraocular muscles. It originates from the back of the roof of the orbit near the common tendinous ring and passes through a fibrous loop (the trochlea) located on the frontal bone. The trochlea is a sling of connective tissue that houses the tendon of the superior oblique, acting as a pulley to allow for the muscle's functions of depression, abduction, and intorsion of the eye.
The trochlear nerve allows for voluntary eye movement, such as looking down and toward or away from the nose. It originates in the midbrain and passes through several areas before reaching the superior oblique muscle near the top of the eyeball. These areas include the trochlear nucleus, ambient cistern, cavernous sinus, and orbit. Damage to the trochlear nerve can cause diplopia (double vision) or blurry vision, particularly when looking down, as the nerve is responsible for innervating the superior oblique muscle and controlling eye movement.
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The trigeminal nerve conveys sensation and allows chewing
The brain is a complex organ that controls thought, memory, emotion, touch, motor skills, vision, breathing, temperature, and hunger, among other processes that regulate the body. The brain itself is not a muscle, but it does contain blood vessels and nerves, including neurons and glial cells.
The trigeminal nerve, also known as the fifth cranial nerve, cranial nerve V, or CN V, is a cranial nerve responsible for sensation in the face and motor functions such as biting and chewing. It is the largest and most complex of the cranial nerves, with both sensory and motor functions. It originates from the pons and conveys sensation from the scalp, teeth, jaw, sinuses, parts of the mouth and face to the brain.
The trigeminal nerve is a three-part nerve in the head that sends signals from the brain to parts of the face and vice versa. There are two trigeminal nerves, one on each side of the face, and they are one set of 12 cranial nerve pairs. The three major branches of the trigeminal nerve are the ophthalmic nerve (V1), the maxillary nerve (V2), and the mandibular nerve (V3). The ophthalmic and maxillary nerves are purely sensory, while the mandibular nerve supplies motor as well as sensory (or "cutaneous") functions.
The mandibular division (V3) of the trigeminal nerve controls the movement of eight muscles, including the four muscles of mastication: the masseter, the temporal muscle, and the medial and lateral pterygoids. The other four muscles are the tensor veli palatini, the mylohyoid, the anterior belly of the digastric, and the tensor tympani. With the exception of the tensor tympani, all these muscles are involved in biting, chewing, and swallowing. The mandibular nerve carries sensory information from the lower lip, the lower teeth and gums, the chin and jaw, parts of the external ear, and parts of the meninges. It carries touch-position and pain-temperature sensations from the mouth.
In summary, the trigeminal nerve conveys sensation from the face and mouth and allows for chewing and other motor functions through the movement of muscles in the head and face.
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Frequently asked questions
The brain is an essential organ that controls thought, memory, emotion, touch, motor skills, vision, respiration, and every process that regulates your body.
The brain controls muscles through the neuromuscular system, which connects muscles and nerves. Nerves called motor neurons send messages from the brain to muscles, making them contract and move.
Voluntary muscles are those that move when you want them to. The cerebrum, the largest part of the brain, controls these muscles. Examples of voluntary muscle movements include dancing, kicking a soccer ball, or pressing the accelerator while driving.
Involuntary muscles are those that work automatically without conscious thought. The brain stem controls these muscles, including those in the heart and stomach. For example, when you are biking, the brain stem tells your heart to pump more blood.
When the brain cannot control muscles properly, it may be due to a neuromuscular disease. Symptoms can include tiredness, muscle weakness, cramps, pain, and in severe cases, difficulty swallowing, speaking, and breathing.
