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Questions and Answers
Which of the following is NOT a characteristic of a reflex?
Which of the following is NOT a characteristic of a reflex?
A reflex arc consists of two types of neurons: sensory and motor neurons.
A reflex arc consists of two types of neurons: sensory and motor neurons.
False
What type of reflex involves the activation of skeletal muscles?
What type of reflex involves the activation of skeletal muscles?
Somatic reflexes
The first component of a reflex arc is the ____, which detects a stimulus.
The first component of a reflex arc is the ____, which detects a stimulus.
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Match the type of reflexes with their characteristics:
Match the type of reflexes with their characteristics:
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What is the primary ability of a neuron to respond to stimuli called?
What is the primary ability of a neuron to respond to stimuli called?
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The plasma membrane at rest has more positive ions inside the cell than outside.
The plasma membrane at rest has more positive ions inside the cell than outside.
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What charge is slightly inside the nerve membrane during polarization?
What charge is slightly inside the nerve membrane during polarization?
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The resting membrane is described as being ______.
The resting membrane is described as being ______.
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Match the following elements of a neuron with their definitions:
Match the following elements of a neuron with their definitions:
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Study Notes
Nervous System Organization
- The nervous system has different structural classifications, including the central nervous system (CNS) and the peripheral nervous system (PNS).
- The CNS consists of the brain and spinal cord.
- The PNS consists of nerves.
- Specific nerves include cranial nerves and spinal nerves.
Nervous System Functions
- Gathering information (sensory input): Monitoring changes inside and outside the body.
- Processing and interpreting sensory input and deciding on an appropriate response (integration).
- Muscles or glands respond to an integrated stimulus (motor output).
Neuron Structure
- Neuron = nerve cell. Cells specialized for transmitting messages.
- Cell body: Includes the nucleus and a large nucleolus.
- Dendrites: Extensions outside the cell body, conducting impulses toward the cell body.
- Axons: Extensions outside the cell body, conducting impulses away from the cell body.
- Axon terminals: Branching ends of the axon, filled with vesicles containing neurotransmitters.
Neuron Anatomy
- Neuron components: dendrites, nucleus, soma, axon, myelin, Schwann cell, node of Ranvier, axon terminal.
Structural Classification of Neurons
- Multipolar neurons: Multiple extensions (axons and dendrites) from the cell body - motor and interneurons are of this type.
- Bipolar neurons: Two processes (one axon, one dendrite) - seen in special sensory organs.
- Unipolar neurons: Single process leaving the cell body (sensory neurons in ganglia of the PNS)
White Matter vs. Grey Matter
- White matter: Myelinated fibers (axons).
- Grey matter: Cell bodies and unmyelinated fibers (axons)
Nerve Impulse Propagation
- Irritability: Ability to respond to stimuli.
- Conductivity: Ability to transmit an impulse.
- Resting membrane: Polarized (fewer positive ions inside the cell than outside the cell).
Starting a Nerve Impulse
- Stimulus: Depolarizes the neuron's membrane.
- Depolarization: Loss of negative charge inside the nerve membrane.
- Action potential: Initiated by ion exchange; transmitted along the axon.
- Repolarization: Potassium ions rush out , and negative ions restore inside
- Sodium Potassium pump: Restores the original configuration of positive and negative ions; requires ATP
Nerve Impulse Propagation
- Propagation: Impulse travels along the fiber or axon.
Nerve Repolarization
- Potassium ions rush out of the neuron.
- Sodium (Na+) ions rush in, and negative ions restore to the inside of the neuron, re-establishing the membrane's polarity, which is the resting status.
Neurotransmitters
- Released at axon terminals into the synaptic cleft
- Diffuse across the synapse to stimulate the next neuron.
- Inactivated by an enzyme.
Synapses
- Synapse: Junction between two neurons (or a neuron and an effector).
- Chemical Synapse: Stimulation of the second neuron is caused by chemical released by the first neuron (presynaptic neuron).
- Synaptic cleft: narrow gap that separates the neurons.
- Neurotransmitters: Chemicals that carry the signal across the synapse; released from synaptic vesicles into the synaptic cleft; combine with receptor sites on the membrane of the receiving neuron.
- Chemical Inactivator: Inactivates the neurotransmitter once it combines with the receptor.
Reflex Arc
- Reflex: Rapid, predictable, involuntary responses to stimuli.
- Reflex arc: Direct route from sensory neuron, to an interneuron, to an effector.
- Receptor
- Sensory neuron
- Integration center
- Motor neuron
- Effector
Reflex Arc: Components
- Receptor: Receives the stimulus, eg. skin.
- Sensory neuron (afferent): Carries impulses away from the receptor to CNS
- Interneuron (association neuron): Process information in the CNS
- Motor neuron (efferent): Carries impulses from the CNS to the effector
- Effector: Muscle or gland that produces the response.
Types of Reflexes
- Autonomic reflexes (involuntary): Regulate smooth muscles, heart rate, blood pressure, glands, and digestive system functions.
- Somatic reflexes (voluntary): Activate skeletal muscles (e.g. knee-jerk reflex).
Homeostasis and Feedback
- Negative feedback: Maintains stability.
- Stimulus causes change in variable
- Receptors detect the change
- Information sent to control center
- Control center sends signal to effector
- Effector response feeds back to influence the stimulus
- Variable returns to homeostasis
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Description
Explore the organization and functions of the nervous system through this quiz. Delve into the structural classifications of the central and peripheral nervous systems, and understand the roles of neurons in transmitting messages throughout the body.
