Test: Nervous System - MCAT MCQ

Concept:-
Spinal nerves: it is a part of the peripheral nervous system.

• Spinal nerves are the path of communication between the spinal cord and the specific region of the body.
• These nerves leave the vertebral column by passing through the intervertebral foramina except the first spinal nerve which emerges b/w the occipital bone and atlas (first vertebra).

Explanation:-

• There are 31 pairs of spinal nerves that originate from both sides of the spinal cord.
  
  

Key Points

• Hippocampus is a complex brain structure embedded deep into the temporal lobe.
• It has a major role in learning and memory.
• It is a plastic and vulnerable structure that gets damaged by a variety of stimuli.
• Studies have shown that it is also gets affected by a variety of neurological and psychiatric disorders.

Key Points

• Medulla oblongata is the bottom-most part of your brain.
• ts location means it's where your brain and spinal cord connect, making it a key conduit for nerve signals to and from your body.
• It also helps control vital processes like your heartbeat, breathing and blood pressure.
• The medulla oblongata is responsible for regulating several basic functions of the autonomic nervous system, including respiration, cardiac function, vasodilation, and reflexes like vomiting, coughing, sneezing, and swallowing.
• The medulla sends signals to the muscles that initiate inspiration and expiration and controls non-respiratory air movement reflexes, like coughing and sneezing.
• It contains nerve fibers and nerve cells covered by myelin, a substance that gives the tissue its white color, protects it and speeds electrical signals. 

Additional Information

• Role of the spinal cord is to send motor commands from the brain to the body, send sensory information from the body to the brain, and coordinate reflexes.
• Spinal nerves send electrical signals between your brain, spinal cord and the rest of your body.
  • These electrical nerve signals help you feel sensations (sensory nerve) and move your body (motor nerves). There are 31 pairs of spinal nerves.
• Pituitary Gland regulates growth, metabolism, and reproduction through the hormones that it produces.
  • These hormone deficiencies can affect any number of your body's routine functions, such as growth, blood pressure or reproduction.

• Neurons, also known as nerve cells, send and receive signals from the brain.
• A neuron has 3 parts: the dendrites, the cell body (also called the "soma"), the axon.'
  • Dendrites - It takes information to the cell body.
  • Cell body (soma) - the part of the cell that contains the nucleus.
  • Axon - It takes information away from the cell body.

• The functional unit of the Kidney is the nephron.
• Red blood cells also called erythrocytes.
• Red blood cells help in carrying oxygen throughout the body.
• Hemoglobin is a pigment in the red blood cells which gives the cells their red color.
• White blood cells (WBCs) are also called leukocytes.
• These help in protecting the body against foreign invaders.

Key Points

• The medulla is the lowest part of the brain and the lowest portion of the brainstem.
• The medulla is connected by the pons to the midbrain and is continuous posteriorly with the spinal cord.
• The medulla plays a critical role in transmitting signals between the spinal cord and the higher parts of the brain and in controlling autonomic activities, such as heartbeat and respiration.

Additional Information

Key Points

• Brain organs will not feel any pain on being pricked by a needle. 
• The brain is a painless organ.
  • So pricking or even removing a part of the brain, while a person is conscious, does not cause any pain.
• Operating brain in a conscious state is a common procedure which is known as “awake craniotomy”.
  • A cover around the brain is a painful structure. Pricking it can cause severe pain.
• There are no pain nor tactile (touch) receptors of any type in the brain itself.
  • So, a needle or even more invasive brain surgery is not associated with any “sensation” of the brain being touched in the patient.
• Hence, option 2 is correct.

Key Points

• The medulla oblongata, also called the medulla, is the lowest part of the brain and the lowest portion of the brainstem.
• The Medulla oblongata or simply medulla is a long stem-like structure that makes up part of the brain.
• It is anterior and partially inferior to the cerebellum.
• The medulla oblongata (or medulla) controls the heartbeat, breathing, and blood pressure. 
• There are three groups of neurons called respiratory centers present in the medulla oblongata and pons the brain as follows:
  • Dorsal respiratory group
  • Ventral respiratory group
  • Pneumotaxis center

The cerebellum does not controls movements, speech, sight, smell, taste, hearing, intelligence etc.
Important Points

• The activities like walking in a straight line, riding a bicycle, picking up a pencil are possible due to a part of the hindbrain called the cerebellum.
• It is responsible for the precision of voluntary actions and maintaining the posture and balance of the body.
• It is a part of the hind brain.

Additional Information

• The brain has three such major parts or regions, namely the forebrain, midbrain and hindbrain.
• The forebrain is the main thinking part of the brain. It has regions which receive sensory impulses from various receptors.
• There is another set of muscle movements over which we do not have any thinking control. Many of these involuntary actions are controlled by the midbrain and hindbrain.
• All these involuntary actions including blood pressure, salivation and vomiting are controlled by the medulla in the hindbrain.

Key Points

• Electroencephalography (EEG) is a method to record an electrogram of the spontaneous electrical activity of the brain.
• The biosignals detected by EEG have been shown to represent the postsynaptic potentials of pyramidal neurons in the neocortex and allocortex.
• It is typically non-invasive, with the EEG electrodes placed along the scalp (commonly called "scalp EEG") using the International 10-20 system, or variations of it.
• Electrocorticography, involving surgical placement of electrodes, is sometimes called "intracranial EEG".
• An EEG might also be helpful for diagnosing or treating the following disorders:
  • Brain tumors, Brain damage from a head injury, and Brain dysfunction can have a variety of causes (encephalopathy), Inflammation of the brain (encephalitis), Stroke, and Sleep disorders.

Additional Information 

Concept:
CNS (central neural system):

• The brain is the body's central information processing organ, and acts as the ‘command and control system’.
• It controls voluntary movements, the balance of the body, and the functioning of vital involuntary organs.

Explanation:
Reflex action:

• The entire process of response to peripheral nerve stimulation occurs involuntarily.
• Without conscious effort or thought and requires the involvement of a part of the central nervous system is called a reflex action.
• The reflex pathway comprises at least one afferent neuron (receptor) and one efferent neuron appropriately arranged in a series.
• The afferent neuron receives signals from a sensory organ and transmits the impulse via a dorsal nerve root into the CNS.
• The efferent neuron then carries signals from CNS to the effector.

Thus, the nerve cells are the control centre of reflex action.

Additional Information
Cerebrum:

• The cerebrum forms the major part of the human brain.
• A deep cleft divides the cerebrum longitudinally into two halves, which are termed the left and right cerebral hemispheres.

Cerebellum:

• It is a part of the hindbrain.
• Cerebellum has a very convoluted surface in order to provide additional space for many more neurons.

Vertebral cord:

• The vertebral column is formed by 26 serially arranged units called vertebrae and is dorsally placed.
• The vertebral column protects the spinal cord, supports the head and serves as the point of attachment for the ribs and musculature of the back.

Key Points

• The main thinking part of the human brain is Cerebrum.
• The cerebrum is the large and outer part of the brain
• It controls reading, thinking, learning, speech, emotions, and planned muscle movements like walking.
• The cerebrum (a major part of the forebrain) is the main thinking part of the brain. It has sensory, motor, and association areas.

Additional Information

• The human brain is divided into three parts or compartments with different functions: Fore-brain, Midbrain, and hindbrain.
• The human brain with the spinal cord makes the central nervous system.
• Fore-brain is the main thinking part and controls voluntary actions.
  • It processes sensory information which is collected from various organs of the body such as ears, eyes, nose tongue, skin, etc.
  • The forebrain consists of Cerebrum, thalamus, and hypothalamus.
  • The cerebrum is the biggest part of the brain and associate with the higher function of thinking and actions.
• Midbrain is a small central part of the brainstem, developing from the middle of the primitive or embryonic brain, the hypothalamus is a portion of the brain
  • It contains a number of small nuclei with a variety of functions, and the lower part of the brainstem, comprising the cerebellum, pons, and medulla oblongata. 
  • Midbrain connects the forebrain and hindbrain. 
  • It is a bridge to transmit signals.
  • The functions are vision, hearing, temperature regulation, and alertness, etc.
• The hindbrain controls the heart rate, breathing, blood pressure, sleep, and walking, etc.
  • the cerebellum is part of the hindbrain.
  • It is maintaining equilibrium, body balance, posture during walking, riding, etc.
    
    

There are four lobes in the human brain.

• Frontal lobe.
• Parietal lobe.
• Occipital lobe.
• Temporal lobe.

Important Points
Parietal lobe:

• Located behind the frontal lobe.
• Receive and transmit sensory information from the body and skin. Also connected other parts of the brain.
• Deals with many sensations including touch, pressure, pain, heat, cold, etc.

Frontal lobe:

• It is the largest part of four major lobes, located at the front of each hemisphere (brain’s cerebral cortex) and covered by the frontal cortex.
• The frontal lobe is separated from the parietal lobe by the central sulcus.
• The major role of the frontal lobe is decision making including self-management, Speech, and language, Comparing objects, memories, understanding, and reacting to feelings, behaviour, attention, etc.

Occipital lobe:

• It is the smallest of the lobes, located at the back portion of the brain and below the occipital bone.
• The primary visual cortex, which is located in the occipital lobe, receives and interprets information from the retinas of the eyes.
• The occipital lobe deals with aspects of vision, including face recognition, movement, object recognition, colour determination, distance, depth perception.

Temporal lobe:

• Located in the bottom section of the brain and sitting close to the ear level within the skull.
• The major functions are hearing, language recognization, speaking and understanding writing, memory acquisition, visual perception, etc.

Concept-

• Human brain is the central organ of the human nervous system
• The brain can be divided into three basic units: the forebrain, the midbrain, and the hindbrain.
• The brainstem network controls blood pressure
• Brain stem include
  • Medulla oblongata
  • Pons
  • Mid brain

Key Points  
Fore-brain:

• The forebrain structures include the cerebrum, thalamus, hypothalamus, pituitary gland.
• Cerebral hemispheres make up the uppermost portion of the brain and are involved in sensory mecahnism, control of voluntary movement, such as speech.
• The thalamus is the main relay centre between the medulla oblongata and the cerebrum.
• Hypothalamus is an important control center for sex drive, pleasure, pain, hunger, thirst body temperature, and other visceral functions.
• Hypothalamus produces hormones that control the secretions of the anterior pituitary gland, and it also produces oxytocin.

Mid-brain:

• The midbrain lies between the thalamus and pons.
• Midbrain serves important functions in motor movement, particularly movements of the eye, and in auditory and visual processing.  

Hind-brain:
There are three main parts of the hindbrain - pons, cerebellum, and medulla oblongata.

• Pons regulate respiration.
• Cerebellum helps with the coordination and movement related to motor skills, especially involving the hands and feet.
• Medulla Oblangata plays an essential role in passing messages between your spinal cord and brain.
• It's also essential for regulating your cardiovascular(Heart) and respiratory systems.
  

Additional Information

• Spinal cord is also a part of central nervous system.
• Primary role of the spinal cord is to relay sensory, motor, and autonomic messages between the brain and the rest of the body.

Key Points

• Blindspot 
  
• The eye lens focuses light on the back of the eye, on a layer called the retina.
• The retina contains several nerve cells.
• Sensations felt by the nerve cells are then transmitted to the brain through the optic nerve.
• At the junction of the optic nerve and the retina, there are no sensory cells, so no vision is possible at that spot.
• This is called the blind spot.

Concept:
Reflex action: 

• It is an extremely quick, automatic, sudden action in response to a stimulus.
• For example-
  • Immediately pulling back of fingers after touching a hot plate.
  • Closing of eyes when flashed with a high-intensity light.
  • Salivation when hungry.

Explanation:
Reflex arc:

• It is the pathway of nerves involved in a reflex action.
• Reflex arc involves-
  • Receptors- The sense organ that receives the message from the external environment.
  • Sensory neuron- The neuron that carries the message from the receptor to the central nervous system.
  • Relay neurons- They are found in the brain and spinal cord and link sensory and motor neurons.
  • Motor neuron- The neuron that carries the message from the central nervous system to the effector.
  • Effector- The organ/body part that responds against the stimulus.

So, there are three neurons involved in the reflex arc namely, sensory, relay, and motor neuron.