General Physiology: Neurons and Action Potential

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Questions and Answers

What condition must be met for another action potential to occur during the relative refractory period?

The neuron must repolarize completely first.

Any normal stimulus can initiate the action potential.

No stimulus can occur during this period.

The stimulus must be greater than the normal stimulus. (correct)

What is the approximate resting membrane potential for neurons?

-50mV

-90mV

-70mV (correct)

-100mV

What is the role of voltage-gated Na+ channels during the action potential?

They initiate depolarizing stimulus. (correct)

They help maintain the resting membrane potential.

They are primarily responsible for saltatory conduction.

They close during repolarization.

What best describes the absolute refractory period?

No action potential can occur, regardless of the stimulus strength. Signup and view all the answers

Which statement describes saltatory conduction?

It involves the jumping of action potentials between nodes of Ranvier. Signup and view all the answers

What primarily occurs in the frontal lobe of the cerebrum?

Voluntary motor control and higher intellectual processes Signup and view all the answers

Which structure is primarily involved in the coordination of movements and receives input from proprioceptors?

Cerebellum Signup and view all the answers

What type of matter is primarily found in the cerebral cortex?

Gray matter Signup and view all the answers

Which part of the brain acts as a relay center for auditory information?

Inferior colliculi Signup and view all the answers

What is the primary function of the medulla oblongata?

Control of autonomic functions like heart rate and breathing Signup and view all the answers

Which lobe of the cerebrum is responsible for interpreting textures and shapes?

Parietal Lobe Signup and view all the answers

What is the function of the basal nuclei?

Control subconscious contractions of skeletal muscles Signup and view all the answers

Which structure is considered part of the emotional brain?

Cingulate gyrus Signup and view all the answers

What is the role of the thalamus in the diencephalon?

Relaying sensory and motor signals between brain regions Signup and view all the answers

What does the cingulate gyrus contribute to?

Emotional regulation and memory processing Signup and view all the answers

Which component of the brainstem is involved in respiratory control?

Pons Signup and view all the answers

What is the primary function of the occipital lobe?

Visual perception and coordination Signup and view all the answers

Which structure is responsible for initiating and terminating movements?

Basal nuclei Signup and view all the answers

What primary role does the hypothalamus serve among the brain's structures?

Regulation of circadian rhythms Signup and view all the answers

What role do oligodendrocytes play in the central nervous system?

They form myelin sheaths around axons. Signup and view all the answers

What distinguishes a multipolar neuron from other types?

It has many dendrites and an axon. Signup and view all the answers

What is the primary function of sensory or afferent neurons?

They transmit impulses from receptors to the CNS. Signup and view all the answers

Which supporting cell type regulates the external environment of neurons in the CNS?

Astrocytes Signup and view all the answers

What is a key factor that can influence action potential propagation?

Axon diameter Signup and view all the answers

Which of the following statements is true about resting membrane potential?

It is constant under resting conditions. Signup and view all the answers

What type of neurons are responsible for connecting sensory and motor pathways?

Association neurons Signup and view all the answers

What is the primary function of Schwann cells in the peripheral nervous system?

They form myelin sheaths around peripheral axons. Signup and view all the answers

Which structures are primarily responsible for the conduction of impulses away from the neuron cell body?

Axons Signup and view all the answers

Study Notes

Neurons

Neurons are specialized nerve cells responsible for transmitting impulses.
Cell body (soma) contains the nucleus and is the central part of the neuron.
Neurons have two processes:
- Dendrites, which carry impulses toward the soma.
- Axons, which carry impulses away from the soma.

Types of Neurons

Unipolar: One extension from the cell body.
Bipolar: Two extensions from the cell body.
Multipolar: Multiple dendrites and one axon.

Neuron Functions

Sensory (afferent): Transmit impulses from receptors to the CNS.
Motor (efferent): Relay impulses from the CNS to effectors (muscles or glands).
Association (interneurons): Connect sensory and motor neurons.

Supporting Cells (CNS)

Oligodendrocytes: Form myelin sheaths around CNS axons.
Microglia: Migrate to phagocytose foreign materials.
Astrocytes: Regulate the external environment of neurons in the CNS.
Ependymal cells: Line brain ventricles and the spinal cord's central canal.

Supporting Cells (PNS)

Schwann cells: Form myelin sheaths around peripheral axons.
Satellite cells: Support neuron cell bodies within ganglia of the PNS.

Nervous System Structure

CNS (Central Nervous System): Comprises the brain and spinal cord.
PNS (Peripheral Nervous System): Includes somatic (motor sensory) and autonomic (involuntary) nervous systems.

Terminologies

Nerve: Bundle of axons in the PNS containing sensory and motor fibers.
Ganglion: Grouping of neuron cell bodies outside the CNS.
Nucleus: Grouping of neuron cell bodies within the CNS.
Tract: Grouping of axons that interconnect CNS regions.

Resting Membrane Potential

A constant membrane potential in excitable and non-excitable cells when at rest.
Neurons typically have a resting membrane potential of -70mV.
The interior of the cell is negatively charged compared to the outside.

Action Potential

Involves rapid changes in membrane potential (approximately 100mV).
Generated by depolarization of excitable membranes due to voltage-gated Na+ channels.
Involves phases of depolarization, repolarization, and hyperpolarization.

Propagation Factors

Degree of myelination affects impulse transmission speed.
Larger axon diameters enhance conduction velocities.
Temperature influences action potential propagation.

Refractory Periods

Absolute Refractory Period: No action potential can occur during this time regardless of stimulus.
Relative Refractory Period: A stronger-than-normal stimulus can initiate a new action potential.

Central Nervous System Organization

Cerebrum: The largest brain part (80% of brain mass) with lobes controlling various functions (voluntary movement, personality, speech).
Cerebral Cortex:
- Contains sensory, motor, and association areas.
- Gray matter consists of cellular bodies, while white matter includes axon tracts.

Lobes of the Cerebrum

Frontal Lobe: Involved in voluntary motor control, personality, and intellect.
Parietal Lobe: Processes somatosensory information and language.
Temporal Lobe: Handles auditory information and memory.
Occipital Lobe: Focuses on visual processing and perception.

Limbic System

Known as the "emotional brain," it plays a key role in emotions and memory.
Key components include the cingulate gyrus, amygdala, hippocampus, and septal nuclei.

Diencephalon

Central core of the brain housing sensory and motor processing nuclei.
Includes thalamus (sensory relay), hypothalamus (homeostasis), and epithalamus (includes pineal gland).

Brainstem Regions

Midbrain: Contains nuclei for visual and auditory reflexes.
Pons: Relays signals between different brain regions and assists in regulating respiration.
Medulla Oblongata: Controls autonomic functions like heart rate and respiration, and houses vital centers.

Cerebellum

Located at the back of the brain, involved in coordination and balance through input from proprioceptors.

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Description

This quiz covers fundamental concepts of neurons and action potentials, focusing on their role in the central nervous system. It explores how neurons stimulate or inhibit muscle contractions and affect gland activities. Enhance your understanding of neurophysiology and its critical functions in the body.