Human Nervous System: Components, Functions, and Neural Processes

What are the main components of the human nervous system?

The brain, spinal cord, and nerves.

What are the two main divisions of the nervous system?

The central nervous system (CNS) and the peripheral nervous system (PNS).

What is the function of the central nervous system?

It processes information and coordinates responses by sending signals to muscles, organs, or glands.

What is the role of neurons in the nervous system?

Neurons transmit electrical signals called nerve impulses.

What are the parts of a neuron?

Dendrites, axon, and cell body.

What is the function of dendrites?

They receive nerve impulses from other cells.

What is an axon?

A long projection from a neuron that carries nerve impulses to target cells.

What are nerve impulses?

Electrical signals transmitted by neurons.

How do nerve impulses travel compared to hormonal messages?

Nerve impulses travel faster than hormonal messages, which are carried through the bloodstream.

What are the two subdivisions of the peripheral nervous system?

The autonomic nervous system and the somatic nervous system.

What does the somatic nervous system control?

Voluntary activities, such as moving muscles.

What does the autonomic nervous system regulate?

Involuntary activities, such as heart rate and digestion.

What are the three main divisions of the autonomic nervous system?

The sympathetic division, parasympathetic division, and enteric division.

What is the function of the sympathetic division?

It controls the fight-or-flight response during emergencies.

What is the function of the parasympathetic division?

It manages routine 'housekeeping' functions of the body.

What is neurogenesis?

The process of forming new neurons, which was thought to stop after prenatal development.

What can happen when the central nervous system is damaged?

Various functions can be impaired, leading to loss of control over voluntary and involuntary actions.

What is the role of sensory receptors in the nervous system?

They detect information from the internal and external environments.

How does the brain respond to information received from sensory receptors?

It processes the information and sends signals to elicit an appropriate response.

What is the relationship between nerves and neurons?

Nerves are bundles of axons from neurons that connect the CNS to the rest of the body.

What is the significance of rapid responses controlled by the nervous system?

They allow for immediate reactions to stimuli, such as avoiding accidents.

What is the typical speed of the fastest nerve impulses?

Greater than 100 meters per second.

What happens to a cell that receives a nerve impulse?

It may be excited to perform a function, inhibited from action, or otherwise controlled.

What are neuroglial cells?

They are the other type of cell in the nervous system, supporting and protecting neurons.

What are the two main types of matter in nervous tissue?

Gray matter and white matter.

What does gray matter primarily contain?

Non-myelinated structures, including the cell bodies and dendrites of neurons.

What is the composition of white matter?

Mainly axons covered with a myelin sheath, which gives them their white color.

What are sensory neurons also known as?

Afferent neurons, which carry nerve impulses from sensory receptors to the central nervous system.

What is the function of motor neurons?

Efferent neurons that carry nerve impulses from the central nervous system to muscles and glands.

What role do interneurons play in the nervous system?

They carry nerve impulses back and forth, often between sensory and motor neurons.

What are neuroglia?

Also called glial cells, they provide support for neurons and help them carry out their functions.

What is the primary function of oligodendrocytes and Schwann cells?

They generate the lipids that make up myelin sheaths, increasing the speed of nerve impulse transmission.

How do neuroglia contribute to neuron support?

They hold neurons in place, supply nutrients, regulate repair, destroy pathogens, and remove dead neurons.

What is the relationship between neuroglia and intelligence?

A higher ratio of neuroglia to neurons is associated with greater intelligence.

What is the resting potential of a neuron?

The difference in electrical charge across the plasma membrane when the neuron is not actively transmitting a nerve impulse.

How does the sodium-potassium pump function?

It maintains resting potential by moving sodium ions out of cells and potassium ions into cells, using energy from ATP.

What is the significance of the myelin sheath?

It insulates axons and increases the speed of nerve impulse transmission.

What is the tiny gap between an axon terminal and a neighboring dendrite called?

A synapse.

What type of exercise may increase neurogenesis in the adult brain?

Sustained aerobic exercise, such as running.

What is the longest nerve in the human body?

The nerve that runs from the base of the spine to the toes.

What happens to neurons as they age?

They may die without being replaced, although neurogenesis can occur in limited capacity.

What are the primary roles of neuroglia?

Support neurons, nourish them, create myelin sheaths, and assist in the transmission of nerve impulses.

What is the difference between sensory and motor neurons?

Sensory neurons carry impulses to the central nervous system, while motor neurons carry impulses away to muscles and glands.

What is the function of the nodes of Ranvier?

They are gaps in the myelin sheath that facilitate rapid conduction of nerve impulses along the axon.

What is resting potential?

An electrical gradient across the cell membrane that is critical for the transmission of nerve impulses.

What role does the sodium-potassium pump play in a neuron?

It maintains the resting potential by pumping sodium out and potassium into the cell.

What initiates an action potential in a neuron?

A chemical signal from another cell or a strong enough stimulus that reaches threshold.

What are the three stages of an action potential?

1. Depolarization, 2. Repolarization, 3. Refractory/Recovery Period.

What occurs during depolarization?

Voltage-gated sodium channels open, allowing Na+ ions to rush into the neuron, making the inside positively charged.

What happens during repolarization?

Voltage-gated potassium channels open, allowing K+ ions to exit the cell, reversing the charge back to negative.

What is the refractory period?

A brief period after an action potential during which another action potential cannot be generated.

How does the sodium-potassium pump restore resting potential?

By moving sodium ions out of the cell and potassium ions into the cell in a 3:2 ratio.

What is the threshold potential for an action potential?

Generally about 15 millivolts (mV) more positive than the cell's resting membrane potential.

What is the role of myelin sheath in nerve impulse transmission?

It allows action potentials to jump between nodes, increasing the speed of transmission.

What is a synapse?

The junction where an axon terminal meets another cell, facilitating the transmission of nerve impulses.

What are the two types of cells involved in a synapse?

Presynaptic cell (sends the impulse) and postsynaptic cell (receives the impulse).

What are neurotransmitters?

Chemicals released from synaptic vesicles that transmit signals across the synaptic cleft.

What happens when an action potential reaches the axon terminal?

Calcium channels open, allowing calcium to enter, which triggers the release of neurotransmitters.

What are the two general types of receptors for neurotransmitters?

Chemically gated ion channels and second messenger systems.

How do chemically gated ion channels affect target cells?

They allow specific ions to flow across the membrane, which can be excitatory or inhibitory.

What is the effect of second messenger systems?

They initiate a cascade of molecular interactions inside the target cell, leading to complex effects.

What is the difference between glutamate and GABA neurotransmitters?

Glutamate can be excitatory or modulatory, while GABA is inhibitory in adults.

What can problems with neurotransmitters or their receptors lead to?

Neurological disorders.

What is myasthenia gravis?

A disease caused by antibodies blocking receptors for acetylcholine in muscle cells, leading to muscle weakness and fatigue.

What role does serotonin play in mental health?

Serotonin helps regulate mood and is involved in conditions like depression, where its imbalance can lead to symptoms.

How do some antidepressant drugs work?

They help alleviate depression by normalizing the activity of serotonin in the brain.

What is a nerve impulse?

An electrical signal that travels along a neuron.

What triggers an action potential?

A significant change in membrane potential that occurs when a neuron is sufficiently depolarized.

How is a signal transmitted at a chemical synapse?

An electrical signal in the presynaptic neuron causes the release of neurotransmitters, which bind to receptors on the postsynaptic cell.

What determines the effects of a neurotransmitter on a postsynaptic cell?

The type of receptor it binds to and the specific cellular mechanisms activated.

What are three general types of effects that neurotransmitters may have on postsynaptic cells?

Excitatory, inhibitory, or modulatory effects.

What ion flow results in an action potential?

The influx of sodium ions (Na+) into the neuron.

What is the function of the sodium-potassium pump?

To maintain the resting potential by actively transporting sodium out of and potassium into the neuron.

Name three neurotransmitters.

Acetylcholine, serotonin, and dopamine.

What is the central nervous system (CNS)?

The part of the nervous system that includes the brain and spinal cord.

What protects the central nervous system?

The meninges, cerebrospinal fluid, and the blood-brain barrier.

What is the role of the brain?

To control mental processes, interpret sensory information, and regulate bodily functions.

What are the three major regions of the brain?

The hindbrain, midbrain, and forebrain.

What is the function of the cerebellum?

To coordinate voluntary movements, balance, and posture.

What does the medulla oblongata control?

Heart rate, respiration rate, blood pressure, and reflexes.

What is the function of the pons?

To relay sensory information and regulate breathing and sleep cycles.

What is the midbrain's role?

To serve as a connection between the brain and spinal cord.

What is the reticular activating system (RAS)?

A network responsible for regulating wakefulness and the sleep-wake cycle.

What is the blood-brain barrier?

A selective barrier that protects the brain from harmful substances while allowing necessary molecules to pass.

How does the brain utilize energy?

It uses about 20% of the body's total energy, primarily from glucose.

What happens if the brain is deprived of glucose?

It can lead to unconsciousness.

What is a homunculus?

A representation of the human body in the brain, showing areas associated with different body parts.

What three structures make up the brainstem?

The medulla oblongata, the pons, and the midbrain.

What is the function of the reticular activating system (RAS)?

It regulates the sleep-wake cycle, wakefulness, attention, ability to focus, and arousal.

What is the forebrain responsible for?

Processing sensory information, performing complex cognitive activities, and governing voluntary motor movements.

What structures are included in the forebrain?

The cerebrum, thalamus, hypothalamus, hippocampus, amygdala, and limbic system.

What is the largest part of the brain?

The cerebrum.

What functions does the cerebrum control?

Conscious intellectual functions such as reasoning, language, memory, sight, touch, and hearing.

What connects the left and right hemispheres of the cerebrum?

The corpus callosum.

What is lateralization in the context of the brain?

The concentration of certain functions in one hemisphere of the brain over the other.

Which hemisphere of the brain is typically associated with language functions?

The left hemisphere.

What are the four lobes of the cerebrum?

Frontal, parietal, temporal, and occipital lobes.

What functions are associated with the frontal lobes?

Executive functions such as attention, self-control, planning, problem solving, reasoning, abstract thought, language, and personality.

What is the role of the parietal lobes?

Involved in sensation, including temperature, touch, taste, and functions related to reading and arithmetic.

What functions do the temporal lobes serve?

Enable hearing, formation and retrieval of memories, and integration of memories and sensations.