Human Biology Nervous System Quiz
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Questions and Answers

What is one of the primary roles of the central nervous system?

  • Processes sensory input and initiates responses (correct)
  • Regulates blood pressure
  • Controls digestive functions
  • Facilitates communication between limbs and organs

Which statement accurately describes the function of the blood-brain barrier?

  • It facilitates rapid communication between neurons
  • It serves as a pathway for neurotransmitter release
  • It protects the brain from harmful substances while allowing essential nutrients to pass (correct)
  • It enhances neural regeneration after injury

What are the two divisions of the autonomic nervous system?

  • Voluntary and involuntary
  • Sensory and motor
  • Cognitive and emotional
  • Sympathetic and parasympathetic (correct)

Which of the following structures has a primary role in sensory input?

<p>Neurons (C)</p> Signup and view all the answers

What is one of the functions of the meninges?

<p>To protect the brain and spinal cord (A)</p> Signup and view all the answers

What role does the myelin sheath play in nerve impulse transmission?

<p>It enhances the speed of nerve impulse propagation. (A)</p> Signup and view all the answers

Which neurotransmitter is associated with the parasympathetic division?

<p>Acetylcholine (D)</p> Signup and view all the answers

What happens during the repolarization phase of an action potential?

<p>Potassium ions leave the neuron. (A)</p> Signup and view all the answers

How does a local anaesthetic affect nerve impulses?

<p>It inhibits the action of sodium channels. (B)</p> Signup and view all the answers

What mechanism is responsible for restoring the resting membrane potential after an action potential?

<p>Activation of sodium-potassium pump using ATP. (A)</p> Signup and view all the answers

What is the primary function of motor output in the nervous system?

<p>To activate muscles or glands (B)</p> Signup and view all the answers

What role do descending tracts play in the spinal cord?

<p>They transmit motor information from the brain to muscles and glands (C)</p> Signup and view all the answers

Which lobe of the brain is primarily responsible for personality and decision-making?

<p>Frontal lobe (D)</p> Signup and view all the answers

Which lobe is the principal center for receiving and interpreting sensations such as touch and pain?

<p>Parietal lobe (A)</p> Signup and view all the answers

Which part of the brain is primarily concerned with processing visual information?

<p>Occipital lobe (A)</p> Signup and view all the answers

What type of division is the autonomic nervous system classified as?

<p>Involuntary and autonomic (C)</p> Signup and view all the answers

What is the largest part of the human brain?

<p>Cerebrum (C)</p> Signup and view all the answers

Which of the following sensations is primarily governed by the temporal lobe?

<p>Hearing (B)</p> Signup and view all the answers

What is the primary function of the basal ganglia?

<p>Coordinates voluntary motor activities (B)</p> Signup and view all the answers

Which condition is primarily associated with dysfunction of the basal ganglia?

<p>Parkinson's Disease (A)</p> Signup and view all the answers

What is the most common cause of cerebellar dysfunction?

<p>Alcohol poisoning (C)</p> Signup and view all the answers

What functions does the cerebellum contribute to in humans?

<p>Coordinating gait and maintaining posture (C)</p> Signup and view all the answers

What is the role of the thalamus in the brain?

<p>Acts as a relay station for sensory stimuli (A)</p> Signup and view all the answers

What is the composition of the brainstem?

<p>Midbrain, pons, and medulla oblongata (A)</p> Signup and view all the answers

What external factors can the blood-brain barrier effectively exclude?

<p>Fats and fat-soluble molecules (A)</p> Signup and view all the answers

What kind of issues would be expected in a patient with trauma to the pons?

<p>Inability to breathe without assistance (D)</p> Signup and view all the answers

What role do receptors play in neurotransmission?

<p>They allow neurotransmitters to bind, triggering new electrical signals in the postsynaptic neuron. (A)</p> Signup and view all the answers

Which of the following neurotransmitters are associated with the sympathetic nervous system?

<p>Epinephrine and Norepinephrine (A)</p> Signup and view all the answers

What is the main function of the parasympathetic nervous system?

<p>To promote a relaxed state and rest. (C)</p> Signup and view all the answers

How does the sympathetic nervous system primarily affect physiological responses?

<p>By raising pulse rate and blood pressure. (D)</p> Signup and view all the answers

What structure is involved in the release of neurotransmitters during synaptic transmission?

<p>Synaptic vesicle (D)</p> Signup and view all the answers

Which component acts as the initial site for transmitting nerve impulses?

<p>Presynaptic membrane (D)</p> Signup and view all the answers

What effect does the activation of adrenergic receptors have on the body?

<p>Prepares the body for emergency by elevating energy levels (D)</p> Signup and view all the answers

What is the primary function of neurotransmitters once they are released into the synaptic cleft?

<p>To bind with receptors on the adjacent cell to transmit signals (B)</p> Signup and view all the answers

What characterizes a reflex arc?

<p>Includes an interneuron between the sensory neuron and the effector (C)</p> Signup and view all the answers

Which condition is characterized by the destruction of nervous tissue without regeneration?

<p>Contusion (A)</p> Signup and view all the answers

What is the primary consequence of a cerebrovascular accident (CVA)?

<p>It results from a ruptured or obstructed blood vessel. (D)</p> Signup and view all the answers

Which of the following is NOT a characteristic of Alzheimer’s disease?

<p>Normal cognitive function in its early stages (D)</p> Signup and view all the answers

Which type of nociceptor responds to fast pain, such as a needle puncture?

<p>Type A myelinated nerve fibers (B)</p> Signup and view all the answers

What defines visceral sensation?

<p>It refers to sensations from internal organs only. (B)</p> Signup and view all the answers

Which of the following statements about pain is incorrect?

<p>Nociceptors can only respond to pleasant stimuli. (B)</p> Signup and view all the answers

Which classification of sensations includes taste and hearing?

<p>Special senses (D)</p> Signup and view all the answers

What is the primary role of the nervous system in maintaining balance within other systems?

<p>Interpreting sensory information and deciding on actions (D)</p> Signup and view all the answers

Which structure primarily separates the brain from potentially harmful substances in the blood?

<p>The blood-brain barrier (D)</p> Signup and view all the answers

Which division of the nervous system is responsible for sensory input and integrating that information?

<p>Central nervous system (C)</p> Signup and view all the answers

What function is primarily impaired in individuals with disorders of the nervous system?

<p>Integration and interpretation of sensory input (A)</p> Signup and view all the answers

What role do meninges play in the nervous system?

<p>They provide protective covering for the brain and spinal cord. (C)</p> Signup and view all the answers

What process occurs immediately after depolarization during an action potential?

<p>Potassium ions rush out of the neuron (C)</p> Signup and view all the answers

Which of the following is a result of the sodium-potassium pump's action?

<p>It restores the original ion configuration after an action potential (C)</p> Signup and view all the answers

How does the presence of a myelin sheath influence nerve impulse transmission?

<p>It increases the velocity of nerve transmission (C)</p> Signup and view all the answers

In multiple sclerosis, which aspect of nerve function is primarily affected?

<p>The integrity of the myelin sheath (D)</p> Signup and view all the answers

What initiates an action potential in a neuron?

<p>A sufficient depolarization of the membrane (C)</p> Signup and view all the answers

Damage to which brain structure primarily results in loss of fine motor control?

<p>Cerebellum (A)</p> Signup and view all the answers

Which brain region acts as a relay station for all sensory stimuli?

<p>Thalamus (A)</p> Signup and view all the answers

What type of breathing problems are likely to arise from trauma to the pons?

<p>Apnea (D)</p> Signup and view all the answers

Which of the following is a consequence of alcohol poisoning on the cerebellum?

<p>Loss of ability to maintain posture (A)</p> Signup and view all the answers

What does the cerebrospinal fluid NOT provide for the brain?

<p>Nutrient absorption (A)</p> Signup and view all the answers

In addition to sensory exclusion, what else does the blood-brain barrier do?

<p>Excludes harmful substances (A)</p> Signup and view all the answers

Which of the following neurologic conditions is closely related to basal ganglia dysfunction?

<p>Parkinson's Disease (A)</p> Signup and view all the answers

What is the primary role of the sensory (afferent) division of the peripheral nervous system?

<p>To receive and carry sensory information to the central nervous system (C)</p> Signup and view all the answers

Which lobe of the brain is primarily involved in processing sensory input such as touch and temperature?

<p>Parietal lobe (A)</p> Signup and view all the answers

Which statement accurately describes the function of descending tracts in the spinal cord?

<p>They carry motor commands from the brain to muscles and glands (C)</p> Signup and view all the answers

What function is primarily associated with the temporal lobe of the brain?

<p>Governing the sense of hearing and smell (B)</p> Signup and view all the answers

What occurs at the synapse when an electrical impulse reaches a neuron?

<p>Release of neurotransmitters. (B)</p> Signup and view all the answers

The autonomic nervous system is classified as which type of division?

<p>Involuntary division that regulates internal organs (A)</p> Signup and view all the answers

The spinal cord functions primarily to:

<p>Carry information to and from the brain (D)</p> Signup and view all the answers

Which neurotransmitters are primarily involved in the sympathetic nervous system?

<p>Epinephrine and Norepinephrine. (B)</p> Signup and view all the answers

Which division of the autonomic nervous system is associated with a relaxed state?

<p>Parasympathetic Nervous System. (C)</p> Signup and view all the answers

Which of the following best describes the functions of the cerebrum?

<p>Involved in higher-order brain functions including decision-making (B)</p> Signup and view all the answers

What happens to the digestive system when the sympathetic nervous system is activated?

<p>It is temporarily suppressed. (B)</p> Signup and view all the answers

Activation of which lobe would most likely impair the ability to recognize visual stimuli?

<p>Occipital lobe (B)</p> Signup and view all the answers

Where does the binding of neurotransmitters occur in synaptic transmission?

<p>On the postsynaptic receptor. (A)</p> Signup and view all the answers

What role do mitochondria play in the synapse?

<p>They provide energy for neurotransmitter release. (B)</p> Signup and view all the answers

What physiological changes are primarily associated with the 'fight or flight' response?

<p>Increased pulse rate and heightened alertness. (A)</p> Signup and view all the answers

What is the primary function of the synaptic cleft?

<p>To facilitate the transmission of chemical signals. (B)</p> Signup and view all the answers

What is the primary characteristic of a concussion?

<p>It is a slight brain injury. (D)</p> Signup and view all the answers

Which of the following best describes cerebral edema?

<p>Swelling resulting from the inflammatory response. (D)</p> Signup and view all the answers

What type of receptors are nociceptors?

<p>Receptors that only respond to noxious stimuli. (D)</p> Signup and view all the answers

What is a significant consequence of a cerebrovascular accident (CVA)?

<p>Death of brain tissue supplied by an obstructed blood vessel. (A)</p> Signup and view all the answers

Which factor characterizes slow pain transmitted through C nerve fibers?

<p>Begins slowly and increases in intensity. (A)</p> Signup and view all the answers

Which statement about Alzheimer’s disease is correct?

<p>It is characterized by abnormal protein deposits within neurons. (C)</p> Signup and view all the answers

Which of the following is NOT a general sensation classification?

<p>Visual sensations. (C)</p> Signup and view all the answers

What role does pain serve in human physiology?

<p>It helps in recognizing potential tissue damage. (A)</p> Signup and view all the answers

Flashcards

What is the nervous system?

The nervous system is a complex network responsible for controlling and coordinating all body functions.

What is the central nervous system (CNS)?

The central nervous system (CNS) is the command center, composed of the brain and spinal cord. It receives, processes, and sends out information.

What is the peripheral nervous system (PNS)?

The peripheral nervous system (PNS) is a network of nerves that extends from the CNS to the rest of the body. Its role is communication between the CNS and organs, muscles, and glands.

What are the functions of the nervous system?

The nervous system gathers information from internal and external environments (sensory input), processes and interprets that information (integration), and then sends out commands to initiate appropriate responses (motor output).

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How does the nervous system maintain balance in the body?

The nervous system ensures the body's internal environment remains stable (homeostasis) by regulating everything from breathing and heart rate to digestion and temperature.

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Motor output

A response to integrated stimuli that activates muscles or glands.

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Sensory (afferent) Division

Nerve fibers that carry information from the body to the central nervous system.

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Motor (efferent) Division

Nerve fibers that carry impulses away from the central nervous system to activate muscles or glands.

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Somatic Nervous System

The part of the motor division that controls voluntary movements.

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Autonomic Nervous System

The part of the motor division that controls involuntary processes like heartbeat and digestion.

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Ascending Tracts

Tracts within the spinal cord that carry sensory information from the body to the brain.

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Descending Tracts

Tracts within the spinal cord that carry motor information from the brain to muscles and glands.

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Cerebrum

The largest part of the brain responsible for higher functions like personality and language.

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Frontal Lobe

The part of the cerebrum responsible for personality and voluntary movements.

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Parietal Lobe

The part of the cerebrum that processes sensory information like touch, temperature, and pain.

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Occipital Lobe

The part of the cerebrum responsible for processing visual information.

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Temporal Lobe

The part of the cerebrum associated with hearing, smell, and memory.

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What are the Basal Ganglia?

A group of structures deep within the cerebrum that regulate voluntary movement. It plays a key role in smooth, purposeful movements.

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What is the Cerebellum?

Located at the back of the brain, it coordinates movement, posture, and balance. It's essential for graceful and precise movements.

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What is the Brainstem?

The lower part of the brain that connects the brain to the spinal cord. It controls vital functions like breathing, heart rate, and blood pressure.

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What is the Thalamus?

A relay station in the brain that directs sensory information (like sight, sound, and touch) to the appropriate areas of the cerebrum.

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What is the Hypothalamus?

A small but powerful part of the brain that controls vital functions like body temperature, hunger, thirst, and hormone release.

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What is the Limbic System?

A network of brain structures involved in emotions, learning, and memory. It helps us experience and process emotions like love, fear, and anger.

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What is Cerebrospinal Fluid?

A clear fluid that surrounds the brain and spinal cord. It acts as a cushion, protects, and helps transport nutrients and remove waste.

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What is the Blood-Brain Barrier?

A protective barrier that surrounds the brain and spinal cord, controlling what substances can enter.

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What is a synapse?

The synapse is the specialized junction between two neurons, or between a neuron and a target cell. It allows for communication through the release and reception of chemical signals called neurotransmitters.

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What is the synaptic cleft?

The synaptic cleft is the narrow gap separating the presynaptic neuron (sender) from the postsynaptic neuron (receiver) at the synapse.

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What is the presynaptic membrane?

The presynaptic membrane is the membrane of the axon terminal, which releases neurotransmitters into the synaptic cleft.

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What is the postsynaptic membrane?

The postsynaptic membrane is the membrane of the dendrite or cell body that receives the neurotransmitter signal.

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What are neurotransmitters?

Neurotransmitters are chemical messengers released by neurons that transmit signals across the synapse to other neurons or target cells.

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What is the autonomic nervous system?

The autonomic nervous system controls involuntary bodily functions, such as heart rate, digestion, and breathing.

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What is the sympathetic nervous system?

The sympathetic nervous system prepares the body for 'fight or flight' responses, increasing heart rate, breathing, and blood pressure.

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What is the parasympathetic nervous system?

The parasympathetic nervous system promotes relaxation and conserves energy, slowing down heart rate, breathing, and blood pressure.

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Parasympathetic Division

The parasympathetic division of the autonomic nervous system is responsible for stimulating the digestive system's processes, including breaking down food. This system relies on acetylcholine as its neurotransmitter, making it a cholinergic system.

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Myelin Sheath Function

The myelin sheath, a fatty covering surrounding nerve fibers, acts as an insulator, allowing nerve impulses to travel faster. It provides a protective layer and aids in efficient signal transmission.

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Depolarization

Depolarization is the initial stage of an action potential, where the inside of the neuron becomes more positive due to the influx of positively charged sodium ions (Na+). This shift in charge initiates the nerve impulse.

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Repolarization

Repolarization follows depolarization, bringing the neuron back to its resting state by the outward flow of potassium ions (K+). This restores the negative charge within the neuron.

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Sodium-Potassium Pump

The sodium-potassium pump actively transports sodium ions out of the neuron and potassium ions back in, using energy (ATP). This restores the original ion balance and maintains the resting membrane potential.

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Reflex

A rapid, automatic, and involuntary response to a stimulus, bypassing conscious thought.

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Reflex Arc

The pathway of nerve impulses during a reflex, involving a sensory neuron, interneuron, and effector.

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Concussion

A mild traumatic brain injury resulting in temporary disruption of brain function.

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Contusion

More severe brain injury causing damage to nervous tissue with no regeneration.

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Cerebral Edema

Swelling in the brain due to inflammation, potentially leading to compression and damage.

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Stroke

A cerebrovascular accident (CVA) caused by a ruptured or blocked blood vessel in the brain, leading to tissue death.

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Alzheimer's Disease

A progressive brain disease causing memory loss, confusion, and death.

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Pain

The ability to sense pain, a crucial warning system for tissue damage.

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What makes up the CNS?

The central nervous system (CNS) is the command center, composed of the brain and spinal cord. It receives, processes, and sends out information.

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What is the PNS?

The peripheral nervous system (PNS) is a network of nerves that extends from the CNS to the rest of the body. Its role is communication between the CNS and organs, muscles, and glands.

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What are the 3 key functions of the nervous system?

The nervous system gathers information from internal and external environments (sensory input), processes and interprets that information (integration), and then sends out commands to initiate appropriate responses (motor output).

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How does the nervous system maintain balance?

The nervous system ensures the body's internal environment remains stable (homeostasis) by regulating everything from breathing and heart rate to digestion and temperature.

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What is a neuron?

A neuron is the basic functional unit of the nervous system. It's composed of a cell body, dendrites, and an axon. Dendrites receive signals, the cell body processes them, and the axon carries signals to other neurons or target cells.

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Brain Stem

A vital part of the brain that connects the brain to the spinal cord, controlling functions like breathing and heart rate.

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Cerebellum

A structure at the back of the brain that coordinates movement, posture, and balance. Think smooth movements.

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Basal Ganglia

A collection of structures deep within the cerebrum that help regulate voluntary movements.

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What are nerve cells?

Nerve cells are specialized cells that transmit electrical signals throughout the body. They are responsible for communication between the central nervous system and the rest of the body.

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What is the myelin sheath and what does it do?

The myelin sheath is a fatty covering surrounding nerve fibers. It acts as an insulator that speeds up nerve impulse transmission, like a protective layer.

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What is depolarization?

Depolarization is the initial phase of an action potential where the inside of a neuron becomes more positive due to sodium ions rushing in. This change initiates the nerve impulse.

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What is repolarization?

Repolarization is the process that follows depolarization, where the neuron returns to its resting state by potassium ions flowing out. This restores the negative charge inside the neuron.

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What is the sodium-potassium pump?

The sodium-potassium pump is a protein pump that actively transports sodium ions out of the neuron and potassium ions back in, using energy (ATP). This maintains the neuron’s resting potential.

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How do neurons communicate at a synapse?

A neurotransmitter is released from the presynaptic neuron's synaptic terminal, crossing the synaptic cleft, and binding to receptors on the postsynaptic neuron. This binding triggers an electrical signal in the receiving cell.

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What is a reflex arc?

A rapid, predictable, and involuntary response to stimuli. It involves a direct pathway from a sensory neuron to an interneuron and then to an effector.

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What is a concussion?

A type of traumatic brain injury that involves a slight brain injury with no permanent damage.

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What is a contusion?

A more severe brain injury where nervous tissue destruction occurs. This type of damage is permanent because nervous tissue does not regenerate.

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What is a cerebrovascular accident (CVA)?

A cerebrovascular accident (CVA) is a stroke. It occurs when a blood vessel supplying a region of the brain ruptures or is blocked by a clot.

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What is Alzheimer's Disease?

A progressive degenerative brain disease that primarily affects the elderly but can begin in middle age. It involves abnormal protein deposits within neurons.

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What are nociceptors?

Special receptors in the body that respond only to noxious stimuli, generating nerve impulses interpreted as pain.

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What is fast pain (acute)?

Fast pain is felt quickly after a stimuli, is sharp and intense, and is usually limited to superficial tissues. It's transmitted by myelinated type A nerve fibers.

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What is slow pain (chronic)?

This type of pain starts slowly but increases gradually, experienced both superficially and in deeper tissues. It's transmitted by unmyelinated, slower C nerve fibers.

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Study Notes

Introduction to the Nervous System

  • The nervous system is a highly complex system divided into two major parts:
    • Central nervous system (CNS)
    • Peripheral nervous system
  • The nervous system controls all other organ systems and is essential for maintaining balance within those systems.
  • Nervous system disorders are numerous and often difficult to diagnose and treat.

Objectives

  • Explain the difference between the central and peripheral nervous systems.
  • Describe the functions of the nervous system.
  • Describe the structure of a neuron.
  • Describe the structure and function of a synapse.
  • Describe the function of the blood-brain barrier.
  • Describe functions of meninges.
  • Describe the functions of the spinal cord.
  • List the major divisions of the brain and give the general functions of each.
  • Explain the two divisions of the autonomic nervous system.

Organization of the Nervous System

  • The nervous system is divided into the central nervous system (CNS) and the peripheral nervous system (PNS).
  • The CNS consists of the brain and spinal cord.
  • The PNS consists of nerves that carry sensory and motor information between the CNS and the rest of the body.
    • Afferent (sensory) division
    • Efferent (motor) division
      • somatic nervous system
      • autonomic nervous system

Functions of the Nervous System

  • Sensory input: gathering information; monitoring changes inside and outside the body.
  • Integration: processing and interpreting sensory input and deciding if action is needed.
  • Motor output: a response to integrated stimuli activates muscles or glands.

Functional Classification of the Peripheral Nervous System

  • Sensory (afferent) division: carries information to the CNS.
  • Motor (efferent) division: carries impulses away from the CNS.
    • Somatic: voluntary nervous system
    • Autonomic: involuntary nervous system

Spinal Cord - Ascending and Descending Tracts

  • The spinal cord carries information to and from the brain.
  • Ascending tracts carry sensory information up to the brain.
  • Descending tracts carry motor information down from the brain to muscles and glands.

Apply Your Knowledge - Answer

  • Descending tracts carry motor information down from the brain to muscles and glands.

The Brain

  • Four parts:
    • Cerebrum
    • Diencephalons
    • Brain stem
    • Cerebellum

Functions of the Cerebrum

  • The largest part of the brain.
  • Composed of different lobes: frontal, parietal, temporal, and occipital.
  • Frontal lobe: influences personality.
  • Parietal lobe: receives and interprets sensations.
  • Occipital lobe: sense of vision.
  • Temporal lobe: senses of smell and sound.

Layers of the Cerebrum

  • Basal ganglia - internal islands of gray matter that regulates voluntary motor activities- dysfunction may result in tremors (Parkinson's Disease)

The Cerebellum

  • Located at the back of the brain.
  • Coordinates gait, equilibrium, and voluntary muscle activity.
  • Damage to this area results in loss of control of fine movements, posture, and motor learning.

The Brainstem

  • Composed of the midbrain, pons, and medulla oblongata.
  • Crucial for respiration and cardiovascular system function.

The Diencephalon

  • Thalamus: relays sensory stimuli to the brain.
  • Hypothalamus: controls body temperature, appetite, body fluids, and endocrine functions.

Limbic system

  • Series of structures involved in learning, memory, and emotional responses (e.g., pain, pleasure, affection, anger).

Cerebrospinal Fluid

  • Supports, protects, and exchanges materials.
  • Forms a watery cushion to protect the brain.
  • Circulates to monitor levels of CO2, O2, and pH.

Blood Brain Barrier

  • Includes the least permeable capillaries of the body, excluding many potentially harmful substances.
  • However, it is not effective against some substances like fats, fat-soluble molecules, respiratory gases, alcohol, nicotine, and anesthesia.

Apply Your Knowledge

  • Trauma to the pons can result in the inability to breathe without assistance.

The Synapse

  • Region where communication occurs between two neurons or between a neuron and a target cell.
  • A neurotransmitter is released from the nerve cell towards the other receiving cell with receptor.

Transmission of Chemical Signals Across the Synapse

  • When an electrical impulse reaches the end of a neuron, neurotransmitters are released.
  • The neurotransmitters bind to receptors in the next neuron generating a new electrical signal.

The Autonomic Nervous System

  • Part of the peripheral nervous system that innervates cardiac muscles, smooth muscles, and glands.
  • Functionally divided into:
    • Sympathetic nervous system: prepares the body for stressful situations (fight or flight)
      • increased heart rate and blood pressure; slows down digestive system; releases adrenaline/noradrenaline (adrenaline-ergic).
    • Parasympathetic nervous system: responsible for resting / digesting
      • decreases heart rate and blood pressure, stimulates digestive system. Releases Acetylcholine (choline-ergic).

Nerve Physiology

  • Nerve cells are excitable cells.
  • Any stimulus changes the membrane potential leading to an impulse (action potential).
  • The myelin sheath increases the velocity of nerve transmission.

Starting a Nerve Impulse

  • A stimulus depolarizes the neuron's membrane.
  • A depolarised membrane allows sodium ions (Na+) to flow inside the membrane.
  • The exchange of ions initiates an action potential in the neuron.

The Action Potential

  • The action potential (nerve impulse) propagates over the entire axon.
  • Potassium ions rush out of the neuron, repolarising the membrane.
  • The sodium-potassium pump restores the original ion configuration.
  • This action requires ATP.

Action Potential (Nerve Impulse)

  • Depolarization: Sodium ions (Na+) pass into the neuron.
  • Repolarization: Potassium ions (K+) pass out of the neuron.
  • Return to resting potential: by closure of potassium channels and activation of the sodium-potassium pump.
  • Local anesthetic blocks sodium channels, preventing pain signal transmission to the brain.

Nerve Impulse Propagation

  • Impulses travel faster when nerve fibers have a myelin sheath.
  • In multiple sclerosis, the myelin sheath is destroyed (autoimmune disease)

The Reflex Arc

  • Reflex: rapid, predictable, and involuntary response to stimuli.
  • Reflex arc: direct route from a sensory neuron, to an interneuron, to an effector.

Traumatic Brain Injuries

  • Concussion: slight brain injury, no permanent damage.
  • Contusion: nervous tissue destruction, nervous tissue does not regenerate, cerebral edema (swelling) may compress and kill brain tissue.

Cerebrovascular Accident (CVA)

  • Commonly called a stroke.
  • Result of a ruptured blood vessel or clot.
  • Brain tissue supplied with oxygen from that blood source dies.
  • Loss of some functions or death may result.

Alzheimer's Disease

  • Progressive degenerative brain disease.
  • Mostly seen in the elderly, can begin in middle age.
  • Structural changes include abnormal protein deposits in neurons.
  • Victims experience memory loss, irritability, confusion, and eventually hallucinations and death.

Classification of Sensation

  • General sensations: superficial (touch, heat, cold), deep, visceral (abnormal conditions).
  • Special senses: taste, smell, vision, hearing.

Pain

  • An unpleasant emotional and sensory experience that accompanies actual or potential tissue damage.
  • Gives conscious awareness of tissue damage.
  • Serves as a protection mechanism, prompting removal of the body from danger, promoting healing and avoiding noxious stimuli.

Nociceptors

  • Special receptors responding only to noxious stimuli.
  • Generate nerve impulses interpreted by the brain as pain.

Fast Pain (Acute)

  • Occurs rapidly after stimulus (0.1 second).
  • Sharp pain (e.g., needle puncture, cut).
  • Not felt in deeper tissues.
  • Transmitted to the brain by type A (myelinated) nerve fibers.

Slow Pain (Chronic)

  • Begins more slowly and increases in intensity.
  • Felt in both superficial and deeper tissues.
  • Smaller C nerve fibers (unmyelinated).
  • Transmitted to the brain by slowly conducting C nerve fibers.

Visceral Pain

  • Often accompanied by strong autonomic and/or somatic reflexes.
  • Poorly localized, may be referred.
  • Mostly caused by distension of hollow organs or ischemia (localized mechanical trauma may be painless).

Referred Pain

  • Pain originating from organs perceived as coming from the skin.
  • Site of pain may be distant from the organ.
  • Examples: Pain from the heart to the left shoulder; pain from gallbladder to the right shoulder.

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