Neuroscience Quiz on Nervous System Functions

Nervous System Functions

• Nervous System functions include:
  • Sensory input : Gathering information about the external and internal environments
  • Integration : Processing information and making decisions
  • Motor output : Sending responses (either voluntary or involuntary) to muscles and/or glands
• Central Nervous System (CNS): Handles integration
• Peripheral Nervous System (PNS): Handles sensory input and motor output
  • Autonomic Nervous System : Controls involuntary functions (e.g., heart rate, digestion)
  • Somatic Nervous System : Controls voluntary movements (e.g., walking, talking)

Organs of the Nervous System

• CNS : Brain and spinal cord
• PNS : Nerves that connect the CNS to the rest of the body

Neuroglial Cells

• Astrocyte :

  • Function : Maintain the blood-brain barrier, provide structural support, regulate neurotransmitter levels, and contribute to neuron growth and repair.
  • Location : CNS

• Ependymal Cell :

  • Function : Line ventricles of the brain and central canal of the spinal cord, produce and circulate cerebrospinal fluid (CSF)
  • Location : CNS

• Microglial Cell :

  • Function : Act as phagocytes, engulfing cellular debris, microorganisms, and pathogens.
  • Location : CNS

• Oligodendrocyte :

  • Function : Wrap around axons in the CNS, forming a myelin sheath that insulates axons and increases nerve impulse conduction speed
  • Location : CNS

• Satellite Cell :

  • Function : Surround neuron cell bodies in ganglia (clusters of neuron cell bodies in the PNS), providing support and regulating the microenvironment of neurons.
  • Location : PNS

• Schwann Cell :

  • Function : Wrap around axons in the PNS, forming a myelin sheath that insulates axons and increases nerve impulse conduction speed
  • Location : PNS

Neuronal Transport Proteins

• Leak Channels :

  • Function : Allow ions to passively move across the cell membrane down their concentration gradient.
  • Transport : Passive Transport (diffusion)

• Voltage-Gated Channels :

  • Function : Open or close in response to changes in membrane potential.
  • Transport : Passive Transport (diffusion)

• Ligand-Gated Channels :

  • Function : Open or close in response to binding of a specific neurotransmitter or ligand.
  • Transport : Passive Transport (diffusion)

• Na+/K+ Pump :

  • Function : Actively pumps sodium (Na+) ions out of the cell and potassium (K+) ions into the cell using energy from ATP.
  • Transport : Active Transport

Neuron Structure & Function

• 3 Main Functions of Neurons :

  • Receive information from other neurons or sensory receptors.
  • Process information (integrate incoming signals).
  • Transmit signals to other neurons, muscles, or glands.

• Dendrite :

  • Function : Receive incoming signals from other neurons.

• Axon Hillock :

  • Function : Integrates incoming signals and generates action potentials.

• Axon :

  • Function : The pathway over which action potentials are conducted.

• Synaptic Bulb :

  • Function : Contain neurotransmitters that are released to communicate with other neurons, muscle fibers, or glands.

Action Potentials

• Threshold : The critical level of depolarization that must be reached for an action potential to be triggered.

• All-or-None Principle : An action potential either occurs with full amplitude or does not occur at all. The magnitude of the stimulus does not affect the amplitude of the action potential.

• Myelin :

  • Function : Insulates axons and increases the speed of nerve impulse conduction.
  • This is achieved by allowing action potentials to "jump" between gaps in the myelin sheath called nodes of Ranvier.

• Nodes of Ranvier :

  • Function : Gaps in the myelin sheath where action potentials are regenerated.

• Action Potential Steps :

  • Depolarization :
    • Na+ Channels Open : Sodium ions (Na+) rush into the cell, making the inside of the cell more positive (less negative).
    • Membrane Potential Becomes More Positive : The membrane potential moves closer to the threshold level.
  • Repolarization :
    • K+ Channels Open : Potassium ions (K+) rush out of the cell, making the inside of the cell more negative again.
    • Membrane Potential Becomes Less Positive : The membrane potential returns to its negative resting state.
  • Hyperpolarization :
    • K+ Channels Remain Open : The membrane potential briefly becomes more negative than the resting membrane potential due to the continued efflux of potassium ions.
  • Return to RMP :
    • Na+/K+ Pump : The sodium-potassium pump restores the original concentration gradients of sodium and potassium across the membrane.
    • Membrane Potential Stabilizes : The membrane potential returns to its resting membrane potential (RMP).

Graded Potentials

• Graded Potential : A localized change in membrane potential that can vary in amplitude depending on the strength of the stimulus.
  • Depolarizing Graded Potentials : Make the membrane potential more positive, increasing the likelihood of an action potential.
  • Hyperpolarizing Graded Potentials : Make the membrane potential more negative, decreasing the likelihood of an action potential.

Resting Membrane Potential (RMP)

• RMP : The electrical potential difference across the membrane of a neuron at rest. - Ionic Concentration Gradients :
  - The difference in concentration of ions across the membrane creates a potential difference. - Selective Permeability : - The cell membrane is more permeable to potassium ions (K+) than to sodium ions (Na+), leading to a net movement of potassium out of the cell.

Refractory Period

• Refractory Period : A period of time during which a neuron is less likely to generate another action potential.
  • Absolute Refractory Period : The neuron is completely unable to generate another action potential, no matter how strong the stimulus.
  • Relative Refractory Period : The neuron can generate an action potential but only if the stimulus is stronger than usual.

Signal Strength

• Frequency of Action Potentials : Neurons communicate the intensity of a stimulus by changing the frequency of action potentials, rather than changing the amplitude of a single action potential.
  • More Frequent Action Potentials : Correspond to stronger stimuli.
  • Less Frequent Action Potentials : Correspond to weaker stimuli.

Multiple Sclerosis (MS)

• Cause : An autoimmune disease in which the immune system attacks the myelin sheath of axons in the CNS.
• Outcome :
  • Slowed Nerve Impulse Conduction : The destruction of myelin disrupts the normal flow of nerve impulses, leading to a variety of neurological symptoms, such as weakness, fatigue, and numbness.
  • Muscle Spasms : The disruption of nerve signaling can also lead to muscle spasms and other motor problems.

Action Potential Speed

• Myelin :

  • Faster Conduction Velocity : Myelin significantly increases the speed of action potential propagation.

• Axon Diameter :

  • Larger Axon Diameter : Larger diameter axons have less resistance to current flow, leading to faster conduction velocities.

Neuron Classification

• Group A Neurons :

  • Fastest Conduction Velocity : These neurons have large diameters and are heavily myelinated.
  • Body Use : Carry sensory information from skin, skeletal muscles, and joints.

• Group B Neurons :

  • Intermediate Conduction Velocity : These neurons have smaller diameters and are lightly myelinated.
  • Body Use : Carry sensory information from internal organs and glands.

• Group C Neurons :

  • Slowest Conduction Velocity : These neurons have small diameters and are not myelinated.
  • Body Use : Carry sensory information from internal organs and glands, and also transmit pain signals.

Synaptic Transmission

• Goals of Synaptic Transmission :

  • Convey Information : To pass information from one neuron to another, to a muscle cell, or to a gland cell.
  • Integrate Information : To integrate information from multiple neurons.

• Process :

  • Action Potential Reaches Synaptic Bulb : An action potential travels down the axon to the synaptic bulb.
  • Calcium Ions (Ca++) Enters Synaptic Bulb : The depolarization of the synaptic bulb opens voltage-gated calcium channels, allowing calcium ions to diffuse into the synaptic bulb.
  • Neurotransmitter Release : The influx of calcium ions triggers the release of neurotransmitters from synaptic vesicles.
  • Neurotransmitter Diffuses into Synaptic Cleft : The released neurotransmitters diffuse across the synaptic cleft (the space between the presynaptic and postsynaptic neurons).
  • Neurotransmitter Binds to Receptors on Postsynaptic Neuron : The neurotransmitters bind to specific receptors on the postsynaptic neuron, causing a change in the membrane potential of the postsynaptic neuron.
  • Signal Transduction : The binding of neurotransmitters to receptors can lead to changes in the postsynaptic neuron's membrane potential, causing either depolarization (excitation) or hyperpolarization (inhibition).

• Type of Transport :

  • Exocytosis : The process of neurotransmitter release from synaptic vesicles.

Neurotransmitter Release

• Calcium Ions (Ca++) : Calcium ions are essential for the release of neurotransmitters from synaptic vesicles.
  • Severe Loss of Body Calcium : A severe loss of body calcium can disrupt the release of neurotransmitters, leading to a coma, because it impairs communication between neurons.

Termination of Synaptic Transmission

• Mechanisms :
  • Reuptake : The presynaptic neuron reabsorbs the neurotransmitter from the synaptic cleft.
  • Enzymatic Degradation : Enzymes in the synaptic cleft break down the neurotransmitter.
  • Diffusion : The neurotransmitter simply diffuses away from the synaptic cleft.

EPSPs and IPSPs

• Excitatory Postsynaptic Potential (EPSP) :

  • Depolarizes Postsynaptic Neuron : These cause the membrane potential of the postsynaptic neuron to become more positive, increasing the likelihood of an action potential.

• Inhibitory Postsynaptic Potential (IPSP) :

  • Hyperpolarizes Postsynaptic Neuron : These cause the membrane potential of the postsynaptic neuron to become more negative, decreasing the likelihood of an action potential.
  • Example : Opening chloride (Cl-) channels and allowing Cl- to enter the postsynaptic neuron

Brainstem

• Medulla Oblongata :

  • Function : Controls vital functions such as heart rate, breathing, and blood pressure. Also works with the pons to help control breathing.

• Pons :

  • Function : Relays impulses between the cerebrum and cerebellum. Also works with the medulla oblongata to help control breathing.

• Midbrain :

  • Function : Governs visual and auditory reflexes and helps control movement. Also functions as a relay center for sensory information and as a center for some auditory and visual reflexes.

Parkinson's Disease

• Cause : Degeneration of dopamine-producing neurons in the substantia nigra of the midbrain.
• Patient Outcomes : Tremors, rigidity, bradykinesia (slow movement), and postural instability.

Diencephalon

• Thalamus :

  • Function : Relay center for sensory information.

• Hypothalamus:

  • Function : Controls autonomic functions, emotions, and drives, including hunger, thirst, and body temperature.
    • Hormonal Regulation : Releases hormones that regulate the pituitary gland and other endocrine glands.

• Epithalamus (Pineal Gland) :

  • Function : Regulates circadian rhythms (sleep-wake cycles) through the production of melatonin.

Hypothalamic Tumors

• Patient Outcomes :
  • Disturbed Appetite : Increased hunger or excessive eating.
  • Temperature Regulation Issues : High fever or shivering.
  • Sleep Disturbances : Insomnia or excessive sleepiness.
  • Hormonal Imbalances : Changes in menstrual cycles, growth hormone levels, etc.

Cerebrum

• Frontal Lobe :

  • Function : Controls voluntary movement, personality, planning, memory, and higher cognitive functions.

• Parietal Lobe :

  • Function : Processes sensory information from the body, including touch, temperature, pressure, pain, and taste.

• Occipital Lobe :

  • Function : Processes visual information.

• Temporal Lobe :

  • Function : Processes auditory information, memory, and language.

• Insula :

  • Function : Processes taste information and some aspects of interoception (awareness of internal body states).

Contralateral Control

• Definition : The left side of the brain controls movement and sensation on the right side of the body, and vice versa.
• Region : Cerebrum

Ipsilateral Control

• Definition : Control of movement or sensation on the same side of the body by the corresponding side of the brain.
• Region : Cerebellum

Aphasia

• Broca's Aphasia :

  • Description : Damage to Broca's area in the frontal lobe, resulting in difficulty speaking fluently.
  • Symptoms : Slow, hesitant speech, difficulty forming grammatically complex sentences.

• Wernicke's Aphasia :

  • Description : Damage to Wernicke's area in the temporal lobe, resulting in difficulty understanding language.
  • Symptoms : Fluent speech that is often meaningless, difficulty comprehending spoken or written language.

Cerebellum

• Function : Coordinates movement, balance, and posture. Also plays a role in learning motor skills.

Neuroendocrine Functions

• Hypothalamus :

  • Function :
    • Produces releasing and inhibiting hormones that control the release of hormones from the pituitary gland.
    • Produces antidiuretic hormone (ADH) and oxytocin.

• Pituitary Gland :

  • Function :
    • Produces a variety of hormones that regulate growth, metabolism, and reproduction.
    • It is controlled by the hypothalamus.

Meninges & Cerebrospinal Fluid (CSF)

• Meninges :

  • Function : Protective membranes that surround the brain and spinal cord.
  • Dura Mater : The outermost, tough layer.
  • Arachnoid Mater : The middle, web-like layer.
  • Pia Mater : The innermost, delicate layer that adheres to the brain and spinal cord.

• Cerebrospinal Fluid (CSF) :

  • Function : Protects the brain and spinal cord from shock and injury, and helps to transport nutrients and remove waste products.
  • Produced by Choroid Plexuses : They are specialized blood vessels that are located in the ventricles of the brain.

Cauda Equina

• Medical Significance : A bundle of spinal nerve roots extending from the end of the spinal cord, important because it can be damaged during surgery or injury.

Epidural Space

• Medical Significance : The space between the dura mater and the vertebrae, commonly used for epidural anesthesia during childbirth.

Spinal Cord Damage

• Dorsal Horns :

  • Loss : Loss of sensory perception.

• Ventral Horns :

  • Loss : Loss of motor control.

• Lateral Horns :

  • Loss : Disruption of autonomic nervous system function.

• Dorsal Roots :

  • Loss : Loss of sensory input from the corresponding spinal nerve.

• Ventral Roots :

  • Loss : Loss of motor control to the corresponding spinal nerve.

• Spinal Nerve :

  • Loss : Complete loss of sensory and motor function in the area supplied by that nerve.

Neurological Terms

• Paralysis : Loss of muscle function.
• Parathesias : Abnormal sensations, such as tingling, numbness, or burning.
• Paraplegia : Paralysis of the lower limbs.
• Quadriplegia : Paralysis of all four limbs.
• Hemiplegia : Paralysis of one side of the body.

Diseases

• Spina Bifida :
  • Patient Outcomes : A birth defect in which the spinal cord does not close completely during pregnancy.
• Amyotrophic Lateral Sclerosis (ALS) :
  • Patient Outcomes : A progressive neurodegenerative disease that affects motor neurons, leading to muscle weakness and atrophy.

Concert Example

• Sensory Input:
  • Pressure of shoe on toe : This sensory information is conveyed by sensory neurons from the big toe to the spinal cord.
  • Pain of shoe on toe : This sensory information is conveyed by sensory neurons from the big toe to the spinal cord via different pathways than pressure information.
• Integration: The spinal cord processes this sensory information and determines that the pressure is not damaging, but the pain is.
• Motor Output: The spinal cord sends a signal to the muscles in the leg to move the foot, which creates a reflex action to remove the foot from harmful pressure.
• Pain Perception: The pain signal is then sent up the spinal cord to the brain for further processing, resulting in the conscious perception of pain.

Test your knowledge on the functions and mechanisms of the nervous system, including the role of astrocytes, action potentials, and synaptic transmission. This quiz covers various aspects of neuroglial cells and brain functions. Ideal for students studying neuroscience or related fields.