Central Nervous System Overview

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Questions and Answers

What are the main components of the Central Nervous System (CNS)?

Somatic and autonomic systems

Nerves and sensory receptors

Motor and sensory neurons

Brain and spinal cord (correct)

Which part of the brain is responsible for problem-solving and memory?

Spinal cord

Medulla Oblongata

Cerebrum (correct)

Cerebellum

Which division of the nervous system includes the somatic and autonomic systems?

Cortex System

Peripheral Nervous System (correct)

Central Nervous System

Cerebral System

What type of neurons are responsible for transmitting signals to muscles?

Motor neurons Signup and view all the answers

Which part of the nervous system is not part of the Central Nervous System?

Peripheral nerves Signup and view all the answers

The autonomic nervous system is further divided into which two systems?

Sympathetic and parasympathetic systems Signup and view all the answers

Which part of the brain controls involuntary functions such as breathing and heart rate?

Medulla Oblongata Signup and view all the answers

What functions does the brain provide, likened to a computer?

Memory and problem-solving Signup and view all the answers

Which function is primarily associated with the cerebellum?

Making automatic adjustments to inertia and momentum Signup and view all the answers

From which part of the body does the cerebellum NOT receive impulses?

Cerebral cortex Signup and view all the answers

What is the primary role of the thalamus?

Processing and relaying sensory impulses to the cortex Signup and view all the answers

Which structure is NOT part of the brain stem?

Thalamus Signup and view all the answers

What major function does the hypothalamus serve?

Integrating autonomic nervous system functions Signup and view all the answers

Which of the following structures contains the pineal gland?

Epithalamus Signup and view all the answers

What is another name for norepinephrine?

Noradrenaline Signup and view all the answers

What does the cerebellum predominantly influence?

Balance and coordination on the same side of the body Signup and view all the answers

Which cranial nerves do NOT originate from the brain stem?

Olfactory nerve Signup and view all the answers

What is the primary role of the cerebral cortex in the brain?

Management of conscious thought and complex nervous reactions Signup and view all the answers

Which neurotransmitter is recognized as inhibitory in the central nervous system?

GABA Signup and view all the answers

Which of the following accurately describes the relationship between the motor area in the cerebral cortex and muscle movements?

Motor impulses from the right hemisphere control movements on the left side of the body Signup and view all the answers

What is the function of lower motor neurons (LMNs)?

Innervate skeletal muscle effectors Signup and view all the answers

What must occur for a lower motor neuron to fire?

More excitatory neurotransmitter must be released than inhibitory neurotransmitter Signup and view all the answers

What characteristics differentiate the sensory areas in the cerebral cortex?

Receive impulses from various sensory fibers including body sense and smell Signup and view all the answers

What does a converging circuit allow for in neural pathways?

Integration from multiple sources into a single response Signup and view all the answers

What type of fibers connect the two hemispheres of the brain?

Commissural fibers Signup and view all the answers

What function do the basal nuclei primarily serve in the brain?

Control of complex semivoluntary movements Signup and view all the answers

Which type of neural circuit sends impulses back to the initial neuron?

Reverberating circuit Signup and view all the answers

Which statement best reflects the significance of the cerebellum?

It is primarily involved in unconscious coordination and balance Signup and view all the answers

What is characteristic of a diverging circuit?

One neuron sends branches to multiple neurons Signup and view all the answers

How does the development of the cerebral cortex in birds compare to that in humans?

Birds have a poorly developed cerebral cortex but highly developed basal nuclei Signup and view all the answers

The final common pathway in motor control refers to which neurons?

Lower motor neurons (LMNs) Signup and view all the answers

What type of nerve fibers are included in the white matter beneath the cerebral cortex?

Myelinated nerve fibers Signup and view all the answers

What type of neuron transmits the impulse to the spinal cord?

Afferent neuron Signup and view all the answers

In a spinal reflex, which muscle is primarily involved in counteracting stretch?

Quadriceps muscle Signup and view all the answers

What determines whether a reflex is classified as somatic or visceral?

The type of effector organs involved Signup and view all the answers

What is the primary purpose of the knee jerk reflex?

To oppose muscle stretch Signup and view all the answers

Which spinal reflex involves both flexor muscle contraction and inhibition of extensor muscles?

Crossed extensor reflex Signup and view all the answers

Where are the simplest reflexes associated mainly?

The spinal cord Signup and view all the answers

Which of the following locations houses most of the reflex centers associated with locomotion and posture?

Cerebellum Signup and view all the answers

What type of reflex uses the autonomic nervous system for regulation?

Visceral reflex Signup and view all the answers

What initiates the depolarization of a neuron's membrane?

Increase in permeability to Na+ Signup and view all the answers

Which process occurs immediately after depolarization?

Increased K+ permeability Signup and view all the answers

What is the primary effect of K+ flowing outward during repolarization?

It establishes a resting membrane potential Signup and view all the answers

What triggers a new action potential in a nerve fiber?

Membrane potential reaching a critical threshold Signup and view all the answers

During the depolarization phase, where does Na+ rush into the neuron from?

From the extracellular fluid where Na+ concentration is high Signup and view all the answers

How does the flow of current occur during a nerve impulse?

Current flows due to the charges attracting each other Signup and view all the answers

What role does depolarization play in the conduction of impulses in nerve fibers?

It facilitates the propagation of action potentials Signup and view all the answers

What is the typical resting membrane potential value in a neuron?

-70 mV Signup and view all the answers

Study Notes

The Nervous System

The nervous system allows animals to adjust to internal and external environmental changes. It acts as a control system.
The two main cell types in the nervous system are neurons and glial cells.
Neurons are the functional units of the nervous system
Glial cells support and protect neurons in the central and peripheral nervous systems.
Human brains contain approximately 100 million neurons and ten times more glial cells.

Neuron Structure

A neuron has a cell body, dendrites, and an axon.
Dendrites receive impulses toward the cell body.
Axons transmit impulses away from the cell body.
A nerve cell process is a dendrite if it conducts impulses toward the cell body, and an axon if it conducts impulses away from the cell body.

Nerve Structure

A nerve is a bundle of axons surrounded by connective tissue and blood vessels.
Axons, connective tissue, and blood vessels are contained within a nerve.

Neuron Types

Sensory neurons transmit impulses from sensory receptors to the central nervous system.
Interneurons connect sensory and motor neurons in the central nervous system.
Motor neurons transmit impulses from the central nervous system to effector organs (e.g., muscles).

Neurons and Synapses

A neuron has only one axon but typically many dendrites.
Dendrites receive information from other neurons to provide a large surface area for communication.

Neuronal Polarity

The polarity of a neuron refers to the number of poles or processes that extend from the cell body.
Bipolar neurons have one axon and one dendrite extending from the cell body (found in the retina of the eyes and olfactory region of the nose).
Pseudounipolar neurons have a single process near the cell body that branches into an axon and dendrite (commonly primary afferent neurons).
Multipolar neurons have many dendrites and a single axon extending from the cell body.

The Axon and Myelin Sheaths

The axon, often with a myelin sheath, is sometimes called a nerve fiber.
The axolemma covers the axon.
Myelin, formed by oligodendrocytes in the central nervous system (CNS) and Schwann cells in the peripheral nervous system (PNS), surrounds the axon and acts as insulation.
Interruptions in the myelin sheath are called nodes of Ranvier.
A group of nerve cell bodies in the CNS is called a nucleus, while outside of the CNS it's called a ganglion.
A bundle of parallel neuron fibers within the brain or spinal cord is a tract.

The Synapse

The synapse provides continuity from one neuron to the next.
There is no physical contact; a synaptic gap separates neurons.
Impulses are transmitted chemically across the synaptic gap via neurotransmitters.
Three characteristics of the synapse are one-way conduction, facilitation (with repeated impulses), and greater fatigability than a neuron.

Neurotransmitters

Neurons do not touch each other; instead chemicals called neurotransmitters are released.
Neurotransmitters are released from vesicles in the presynaptic neuron.
Neurotransmitters bind to receptors on the postsynaptic neuron, altering its membrane permeability.

Glial Cells

Glial cells are non-neuronal cells in the central nervous system.
The vast number of glial cells makes up about half the volume of nervous tissue.
Glial cells are metabolically active.
Macroglia, microglia, and ependymal cells are the classification for glial cells.
Types of macroglial cells are: Oligodendrocytes-myelin sheath forming in the CNS. Astrocytes-most prominent glial cells; their processes surround blood vessels, synaptic structures, and nerve cell bodies and processes; also have phagocytic function. Other functions include: maintaining homeostasis, forming myelin, and providing support and protection for neurons.
Microglia-phagocytic function.

Central Nervous System (CNS)

Composed of the brain and spinal cord.
Structures of the brain: Cerebrum (paired cerebral hemispheres) Cerebellum (unpaired) Brain stem (midbrain, pons, medulla oblongata)

Peripheral Nervous System (PNS)

Consist of spinal nerves and cranial nerves.
Spinal nerves arise from spinal cord (7cervical, 13thoracic, 7lumbar, 3 sacral and 20 caudal) and carry afferent/efferent fibers (mixed nerves).
Cranial nerves (12 pairs) innervate structures in the head and neck. The vagus nerve is an exception, as it innervates thoracic and abdominal viscera in addition to the head and neck.

Autonomic Nervous System (ANS)

The involuntary nervous system; associated with homeostatic functions.
Has three parts: Sympathetic (SNS) - associated with body response to stress; Parasympathetic (PSNS) – associated with homeostatic functions in the absence of stress; Enteric (ENS) – associated with regulation of digestive system;
ANS innervates smooth muscle, cardiac muscle, and glands.

Motor Neurons of Autonomic and Somatic Nervous Systems

Autonomic: preganglionic and postganglionic neurons Neurotransmitter: acetylcholine (ACh) or norepinephrine
Somatic: have one neuron from neuron to effector

Sympathetic and Parasympathetic Nervous Systems (ANS)

The sympathetic system prepares the body for "fight or flight" responses.
The parasympathetic system is active when the animal is at rest or not under stress (e.g., "rest and digest").
The ganglia of the sympathetic system are located in the thoracic and lumbar regions of the spinal cord.
The ganglia of the parasympathetic system are located in or near the effector organs.

Neurotransmitters in the Nervous System

Somatic: Acetylcholine (ACh)
Sympathetic: Acetylcholine (ACh) as a preganglionic transmitter, and norepinephrine (NE) as a postganglionic transmitter.
Parasympathetic: Acetylcholine (ACh) as both preganglionic and postganglionic transmitters.
Central Nervous System: Acetylcholine (ACh), norepinephrine (NE), dopamine, gamma-aminobutyric acid (GABA), and glycine

Reflexes

Unconditional reflexes are inherent and invariable.
Conditional reflexes are learned and can be modified by experience.

Spinal Reflexes

Types of spinal reflexes: flexor, extensor pushing, crossed extensor, itching, stepping, and withers in horses, plantar.

Neural Conduction

Irritability: Ability to respond to stimuli.
Conductivity: Ability to transmit impulses (nerve impulses from receptors to effectors).
Correlation: Integration of impulses (decision-making process by synapses.
Reaction: A response to the integrated impulses.

Cerebrospinal Fluid

Thin, watery fluid derived from blood plasma.
Functions: acts as a shock absorbing fluid for the brain and spinal cord

Central Nervous System (CNS) Metabolism

The CNS's primary energy source is glucose.
Glucose is transported into the CNS by simple diffusion.
CNS has relatively high metabolism
Blood delivers the nutrients it needs for high rate of metabolism.
The tolerance of an adult brain to hypoxia is lower than the tolerance of a newborn brain.

Blood-Brain Barrier

The blood-brain barrier protects the brain from many substances in the blood.
Tight junctions between the endothelial cells of blood vessels in the CNS limit diffusion of many substances from blood capillaries into the brain.
Astrocytes play a role in the movement of substances across this barrier.

The Nerve Impulse and its Transmission

Stimulation causes electrical signals in nerve cells.
These signals are based around changes in the permeability of the cell membrane to certain ions.
The nerve signal flows along the axon away from the cell body.

Action potential

Changes in the membrane potential along the axon are called action potentials.
Changes in membrane potential are based on changes in the permeability of the neuron's cell membrane to ions (i.e., sodium and potassium).
Depolarization of the membrane occurs when the membrane becomes more permeable to Na+ which flows into the neuron; this event results in a positive charge inside the neuron and a negative charge outside of the neuron.
Repolarization is the process in which the membrane returns to its original charge across the neuron's membrane by allowing K+ to flow out of the neuron.

Excitatory and Inhibitory Postsynaptic Potentials (EPSPs and IPSPs)

Graded potentials that cause depolarization (EPSPs) or hyperpolarization (IPSPs) cause changes in the neuron's membrane potential. This process is what makes the neuron's membrane more or less excitable.
Neurotransmitters like acetylcholine (ACh) and glutamate cause an EPSP by opening ligand-gated Na+ channels and thus bringing about an influx of Na+ into the cell thus creating a positive charge inside the cell.
Neurotransmitters like glycine and GABA cause an IPSP by increasing the permeability of the membrane to Cl- which thus brings about an influx of Cl- into the cell thus creating a negative charge inside the cell.

Saltatory Conduction

Saltatory conduction is the mode of action potential transmission that involves leaping from node of Ranvier to the next node on the unmyelinated axon. The myelination of the axon prevents the flow of current to the areas of the axon membrane between the nodes.
The myelination of the axon permits the leaping from one node to the next.
This method is faster than continuous conduction.

Postsynaptic Potentials

Generated at the cell body or dendrites.
Two main types: Excitatory postsynaptic potential (EPSP)--depolarizing (more positive) Inhibitory postsynaptic potential (IPSP)--hyperpolarizing (more negative)
The sum of EPSPs and IPSPs in the neuron's cell body determine if the action potential has been reached. If the potential is sufficiently depolarized, then the neuron's threshold is reached triggering the generation of an action potential.

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Test your knowledge on the components and functions of the Central Nervous System (CNS). This quiz covers various aspects, including brain regions responsible for memory, problem-solving, and involuntary functions. Explore how the nervous system is structured and its critical roles in bodily functions.