Nervous System and Function

Question 1

Central Nervous System

Answer 1

It’s the primary control centre of the human body, consisting of the brain and spinal cord. It is responsible for processing and integrating sensory information, coordinating motor functions, and controlling higher-level cognitive functions, such as thinking, memory, and emotions. The CNS is critical in regulating all bodily processes and is protected by the skull and vertebral column.

Question 2

Peripheral Nervous System

Answer 2

It’s the network of nerves and ganglia outside the Central Nervous System (CNS). The PNS connects the CNS to the rest of the body, transmitting sensory information from the body to the CNS and conveying motor commands from the CNS to muscles and glands. It is divided into two main components: the somatic nervous system and the autonomic nervous system

Question 3

Somatic Nervous System

Answer 3

It’s a division of the PNS responsible for the voluntary control of skeletal muscles and the processing of sensory information from external stimuli. It allows conscious control over muscle movements and is involved in activities like walking, talking, and gesturing. The SNS consists of motor neurons that transmit signals from the CNS to muscles and sensory neurons that transmit information from the body’s sensory receptors to the CNS, enabling us to perceive and interact with the external environment. Basically, it interacts with the external environment.

Question 4

Automatic Nervous System

Answer 4

It’s a branch of the PNS responsible for regulating involuntary bodily functions, such as heart rate, digestion, respiration, and glandular activity. It operates independently and continuously to maintain homeostasis, and it consists of two main divisions: the sympathetic nervous system, which prepares the body for “fight or flight” responses, and the parasympathetic nervous system, which promotes “rest and digest” functions. The ANS plays a crucial role in maintaining internal organ functions and responding to external and internal stressors.

Question 5

Parasympathetic Nervous System

Answer 5

It’s one of the two main divisions of the ANS and is responsible for promoting “rest and digest” responses in the body. The parasympathetic system is active during times of relaxation and recovery, reducing heart rate, promoting digestion, and conserving energy. It helps maintain bodily functions at a steady state, allowing the body to recover and repair after periods of stress or activity.

Question 6

Sympathetic Nervous System

Answer 6

It’s one of the two primary divisions of the Autonomic Nervous System (ANS), responsible for initiating the body’s “fight or flight” response to stress, danger, or excitement. When activated, the sympathetic system increases heart rate, dilates airways, redirects blood flow to the muscles, and prepares the body for rapid action. It plays a vital role in mobilizing the body’s resources to deal with immediate threats, stressors, or challenging situations, allowing for quick and intense physical and mental responses. Arousal.

Question 7

Afferent Nerves

Answer 7

Also known as sensory nerves, are a type of nerve in the Peripheral Nervous System (PNS) that transmit sensory information from the body’s sensory receptors (e.g., skin, eyes, ears) to the Central Nervous System (CNS), which includes the brain and spinal cord. These nerves allow us to perceive and process sensory stimuli such as pain, temperature, touch, taste, and sound. The input nerve.

Question 8

Efferent Nerves

Answer 8

Also known as motor nerves, are a type of nerve in the Peripheral Nervous System (PNS) that transmit signals from the Central Nervous System (CNS) to muscles, glands, and other effector organs. Efferent nerves play a crucial role in controlling and regulating bodily functions, allowing the CNS to initiate voluntary and involuntary actions, including muscle movements, hormone secretion, and organ functions. The output nerve.

Question 9

Spinal Cord Information

Answer 9

Information is input through the Dorsal stream (Back side) and output information is sent through the Ventral stream (front side)

Question 10

Forebrain

Answer 10

The forebrain is the largest and most complex part of the brain, forming the anterior (top) region of the brain’s three major divisions (forebrain, midbrain, and hindbrain). It plays a crucial role in various higher-order functions, including conscious thought, perception, emotion, memory, and complex motor functions. The forebrain is further subdivided into the diencephalon, which includes the thalamus and hypothalamus, and the telencephalon, which comprises the cerebral cortex, basal ganglia, and limbic system. It is responsible for processing sensory information, controlling voluntary and involuntary movements, regulating body temperature, and governing many other essential functions.

Question 11

Telencephalon

Answer 11

The telencephalon is the most prominent and highly developed part of the forebrain, forming the bulk of the cerebral hemispheres in the brain. The telencephalon contains the cerebral cortex, which is divided into various lobes responsible for different functions, such as the frontal lobe for executive functions, the temporal lobe for auditory processing, and the occipital lobe for visual processing. It also includes structures like the basal ganglia and the limbic system, which are vital for motor control and emotional regulation, respectively.

Question 12

Diencephalon

Answer 12

The diencephalon is a division of the forebrain, positioned between the telencephalon (cerebral hemispheres) and the midbrain. It includes several important structures, most notably the thalamus and hypothalamus.

Question 13

Neocortex

Answer 13

It’s the outermost layer of the cerebral hemispheres in the brain. Key features of the neocortex include its six-layered structure, its immense size in humans (comprising about 80% of the brain’s volume), and its convoluted surface, marked by numerous gyri and sulci.

1.) Axons and dendrites, few cell bodies
2.) Densely packed stellate cells, a few small pyramidal cells.
3.) Loosely packed stellate cells, intermediate-sized pyramidal cells.
4.) Bands of densely packed stellate cells, no pyramidal cells
5.) Very large pyramidal cells, a few loosely packed stellate cells
6.) Pyramidal cells of various sizes, loosely packed stellate cells.
7.) White matter- Myelinated pyramidal cell axons, few cell bodies.

Question 14

Neurons

Answer 14

Are the fundamental building blocks of the nervous system. They are specialized cells that transmit electrical and chemical signals, allowing communication within the nervous system and between the nervous system and other parts of the body. Neurons consist of three main parts: the cell body (soma), dendrites, and an axon. Dendrites receive incoming signals, the cell body integrates these signals, and the axon transmits the signal to other neurons, muscles, or glands. Neurons play a critical role in processes such as sensation, perception, movement, and cognition, making them essential for the functioning of the nervous system and the body as a whole.

Question 15

Synapses

Answer 15

These are specialized junctions that allow communication between neurons in the nervous system. They serve as the connection points where one neuron (the presynaptic neuron) sends signals to another neuron (the postsynaptic neuron), or to a muscle cell or gland. The transmission of information across synapses occurs through the release of neurotransmitters from the presynaptic neuron’s axon terminals. These neurotransmitters traverse the synaptic cleft and bind to receptors on the postsynaptic neuron’s dendrites or cell body, leading to changes in the postsynaptic neuron’s membrane potential. Synapses can be excitatory, promoting the firing of the postsynaptic neuron, or inhibitory, preventing its firing, depending on the neurotransmitters involved and the receptor types on the postsynaptic neuron.

Question 16

Synaptic cleft

Answer 16

Is a tiny, fluid-filled gap or space that separates the axon terminal of one neuron (presynaptic neuron) from the dendrites or cell body of another neuron (postsynaptic neuron) or an effector cell, such as a muscle or gland cell. The transmission of information between neurons or between neurons and target cells occurs across the synaptic cleft. When an action potential reaches the axon terminal of the presynaptic neuron, it triggers the release of neurotransmitters into the synaptic cleft. These neurotransmitters diffuse across the cleft and bind to receptors on the postsynaptic neuron or target cell, initiating a response in the postsynaptic cell.

Question 17

Membrane Potential

Answer 17

Is the electrical voltage difference across the neuron cell membrane when the neuron is at rest. Neurons are polarized cells, meaning they have a difference in electrical charge between the inside and outside of the cell. The resting membrane potential is -70mV, with the inside of the cell being more negative relative to the outside.

Question 18

Graded Potential

Answer 18

These are small changes in the membrane potential of a neuron in response to a stimulus. These changes can be depolarizing (making the neuron less negative) or hyperpolarizing (making the neuron more negative) and vary in magnitude depending on the strength of the stimulus. Graded potentials occur in dendrites and the cell body of a neuron and are typically not sufficient to initiate an action potential. Instead, they serve to transmit and integrate information over short distances and can summate to reach the threshold required to trigger an action potential.

Question 19

Action Potential

Answer 19

Is a brief but large change in the membrane potential of a neuron that propagates along the axon. It is an all-or-nothing event that occurs when the membrane potential reaches a critical threshold. During an action potential, there is a rapid depolarization phase, followed by repolarization and, in some cases, hyperpolarization. Action potentials are essential for long-distance neural communication and serve to transmit information from one end of the neuron to the other. They are characterized by their consistent magnitude and speed of propagation, ensuring reliable transmission of signals in the nervous system.

Question 20

Action Potential Propagation

Answer 20

Refers to the process by which an action potential travels along the length of a neuron’s axon. It involves a series of events that ensure the rapid and unidirectional transmission of electrical signals from the neuron’s cell body to its axon terminals.

1.) An action potential begins at the axon hillock when the membrane potential reaches a critical threshold. This is usually triggered by a sufficient depolarizing graded potential. (more positive)

2.) Depolarization: Once initiated, the axon’s membrane depolarizes as voltage-gated sodium channels open, allowing sodium ions(+) to enter the axon. This causes a rapid and substantial increase in the membrane potential.

3.) Propagation: The depolarization at the axon hillock triggers adjacent segments of the axon to reach their threshold, initiating new action potentials. This domino-like effect allows the action potential to propagate along the axon.

4.) Repolarization: As the action potential travels, voltage-gated potassium (-) channels open, allowing potassium ions to leave the axon. This causes the membrane to repolarize, returning to a negative resting potential.

5.) Hyperpolarization: In some cases, there is a brief hyperpolarization (undershoot) following repolarization, where the membrane potential temporarily becomes more negative than the resting potential. This helps prevent the neuron from immediately firing another action potential.

6.) Refractory Period: After an action potential, there is a brief refractory period during which the neuron cannot generate another action potential. This ensures that action potentials propagate in one direction and do not backtrack.

Question 21

Hodgkin-Huxley Cycle

Answer 21

Understanding how action potentials are generated and propagated along neuronal axons.

Depolarization of membrane —> Opening of voltage-gated Na+ channels —> Na+ flows into neuron—> Depolar…..

Question 22

Ion Flow Through Ion Channels

Answer 22

Neuronal membranes contain various types of ion channels, Voltage-gated ion channels respond to changes in the membrane potential (voltage) of the neuron. They can be either sodium channels or potassium channels. When the membrane potential changes, the channels open or close based on their specific voltage thresholds. Sodium Channels: Voltage-gated sodium channels open when the membrane depolarizes (becomes less negative), allowing sodium ions to rapidly flow into the neuron. This influx of sodium is responsible for the depolarization phase of an action potential. Potassium Channels: Voltage-gated potassium channels open during the action potential, allowing potassium ions to flow out of the neuron. This efflux of potassium contributes to repolarization, helping to restore the membrane to its resting potential.

Question 23

Myelination

Answer 23

Myelination is the process by which nerve fibres, or axons, are insulated and protected by a fatty substance called myelin. Myelin acts as an electrical insulator, greatly enhancing the speed and efficiency of electrical impulse conduction along the axon. This process is essential for the proper functioning of the nervous system. This speeds up action potential propagation. The myelin forms a sheath around axons, covering them in segments with small gaps. these segments allow for saltatory conduction, where the action potential “jumps” from one node to another, significantly speeding up the transmission of electrical signals. The myelin serves to insulate the axon, preventing the leakage of ions across the membrane. This, in turn, accelerates the propagation of action potentials and allows for the conservation of energy within the neuron. Myelination is crucial for proper sensory and motor function. Conditions affecting myelin, such as demyelinating diseases (e.g., multiple sclerosis), can lead to impaired nerve conduction and various neurological symptoms.

Question 24

Multiple Sclerosis

Answer 24

Numbness or weakness in one or more limbs, partial or complete loss of central vision usually in one eye, double vision or blurring, tingling or pain in parts of your body, electric-shock sensations that occur with certain head movements, tremor, lack of coordination or unsteady gait, slurred speech, fatigue, dizziness.