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Questions and Answers
What is the purpose of the nervous system?
What is the purpose of the nervous system?
Maintain homeostasis
What are the two systems that help maintain homeostasis?
What are the two systems that help maintain homeostasis?
Astrocytes are electrically excitable cells.
Astrocytes are electrically excitable cells.
False
Neurons are responsible for sensing, thinking, memory, muscle activity control, and gland __________.
Neurons are responsible for sensing, thinking, memory, muscle activity control, and gland __________.
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Match the functions of the following types of neurons:
Match the functions of the following types of neurons:
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What type of channels respond to chemical stimuli in neurons?
What type of channels respond to chemical stimuli in neurons?
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What determines the Resting Membrane Potential (RMP) of a neuron?
What determines the Resting Membrane Potential (RMP) of a neuron?
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What are the two phases of an Action Potential?
What are the two phases of an Action Potential?
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Electrical synapses communicate faster than chemical synapses.
Electrical synapses communicate faster than chemical synapses.
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What is the effect of myelination on the propagation speed of nerve impulses?
What is the effect of myelination on the propagation speed of nerve impulses?
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What are the two layers that compose the cranial dura mater?
What are the two layers that compose the cranial dura mater?
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What does the blood-brain barrier (BBB) consist of?
What does the blood-brain barrier (BBB) consist of?
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Ataxia results from damage to the cerebellum.
Ataxia results from damage to the cerebellum.
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The ________ regulates the rate and rhythm of breathing.
The ________ regulates the rate and rhythm of breathing.
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What are the two structures of neurotransmitter receptors on the post-synaptic membrane?
What are the two structures of neurotransmitter receptors on the post-synaptic membrane?
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What are the two types of postsynaptic potentials?
What are the two types of postsynaptic potentials?
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Spatial and temporal summation refer to the ways in which multiple presynaptic end bulbs release neurotransmitter at the same time. True or False?
Spatial and temporal summation refer to the ways in which multiple presynaptic end bulbs release neurotransmitter at the same time. True or False?
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Excitotoxicity occurs due to increased levels of _________ in the interstitial fluid of the CNS.
Excitotoxicity occurs due to increased levels of _________ in the interstitial fluid of the CNS.
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Match the neurotransmitters with their descriptions:
Match the neurotransmitters with their descriptions:
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What is Guillain Barre syndrome?
What is Guillain Barre syndrome?
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Which autoimmune disease is characterized by immune-mediated inflammatory disease of the CNS?
Which autoimmune disease is characterized by immune-mediated inflammatory disease of the CNS?
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Remyelination leads to successively fewer effective ______, until a scar-like plaque is built up around the damaged axons.
Remyelination leads to successively fewer effective ______, until a scar-like plaque is built up around the damaged axons.
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Flexor reflex is a monosynaptic reflex arc.
Flexor reflex is a monosynaptic reflex arc.
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Match the following reflexes with their descriptions:
Match the following reflexes with their descriptions:
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What area is involved in the articulation of speech?
What area is involved in the articulation of speech?
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What type of information does the 1° Visual area receive?
What type of information does the 1° Visual area receive?
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Alzheimer's disease primarily affects children.
Alzheimer's disease primarily affects children.
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Loss of neurons that liberate _____ leads to Alzheimer's disease.
Loss of neurons that liberate _____ leads to Alzheimer's disease.
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Which neurotransmitters are primarily used in the Autonomic Nervous System?
Which neurotransmitters are primarily used in the Autonomic Nervous System?
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What are the two types of receptors where Acetylcholine binds in the ANS?
What are the two types of receptors where Acetylcholine binds in the ANS?
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In the Autonomic Nervous System, all sympathetic postganglionic synapses primarily use Norepinephrine as the neurotransmitter.
In the Autonomic Nervous System, all sympathetic postganglionic synapses primarily use Norepinephrine as the neurotransmitter.
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What is the function of the hypothalamus?
What is the function of the hypothalamus?
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Which region lies superior and posterior to the thalamus?
Which region lies superior and posterior to the thalamus?
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The pineal gland secretes cortisol.
The pineal gland secretes cortisol.
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The circumventricular organs monitor chemical changes in the blood because they lack a _____.
The circumventricular organs monitor chemical changes in the blood because they lack a _____.
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Match the following brain tracts with their functions:
Match the following brain tracts with their functions:
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What neurotransmitter is released by preganglionic neurons in the parasympathetic nervous system?
What neurotransmitter is released by preganglionic neurons in the parasympathetic nervous system?
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Which receptors are activated by muscarinic receptors in the parasympathetic nervous system?
Which receptors are activated by muscarinic receptors in the parasympathetic nervous system?
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NE lingers in the synaptic cleft for a longer time compared to ACh, resulting in longer-lasting effects triggered by ____________ neurons.
NE lingers in the synaptic cleft for a longer time compared to ACh, resulting in longer-lasting effects triggered by ____________ neurons.
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Parasympathetic responses reduce body functions that support physical activity.
Parasympathetic responses reduce body functions that support physical activity.
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Study Notes
Introduction to the Nervous System
- The nervous system helps maintain homeostasis and responds rapidly to external stimuli
- Two main systems: endocrine (hormones, slow response) and nervous (neurotransmitters, rapid response)
Organization of the Nervous System
- Central nervous system (CNS): brain and spinal cord
- Peripheral nervous system (PNS): nerves outside CNS
- Somatic nervous system: voluntary muscle control
- Autonomic nervous system: involuntary functions (heart rate, digestion)
Functions of the Nervous System
- Sensory: receives and interprets stimuli
- Motor: responds to stimuli with muscle or gland action
- Integrative: processes and integrates information
Histology of the Nervous System
- Two main cell types: neurons and neuroglia
- Neurons: electrically excitable, responsible for sensing, thinking, and controlling muscle activity
- Neuroglia: support, nourish, and protect neurons
Neurons
- Electrically excitable, with axons that transmit signals
- Classified structurally (multipolar, bipolar, unipolar) or functionally (sensory, motor, inter)
Neuroglia
- Not electrically excitable
- Five types: astrocytes, oligodendrocytes, microglia, ependymal cells, and satellite cells
- Functions: support, nourish, and protect neurons, as well as maintain the BBB (blood-brain barrier)
Myelination
- Insulates and increases nerve impulse speed
- In CNS: oligodendrocytes myelinate multiple axons
- In PNS: Schwann cells myelinate single axons
Electrical Signals in Neurons
- Ion channels allow movement of specific ions across the membrane
- Ion flow creates an electrical current that alters membrane potential
- Types of ion channels: leakage, ligand-gated, mechanogated, and voltage-gated
Resting Membrane Potential
- Result of unequal ion distribution and selective membrane permeability
- Na+/K+-ATPase pumps maintain the resting potential
Graded Potentials
- Small, localized changes in membrane potential
- Can be added together (summation) to create a larger response
Action Potentials
- Rapid sequence of events: depolarization, repolarization, and refractoriness
- All-or-none principle: the neuron either fires or doesn't
Refractory Periods
- Absolute refractory period: cannot fire again immediately
- Relative refractory period: can fire again, but with less intensity### Neurotoxins and Local Anesthetics
- Neurotoxins act on the nervous system, while local anesthetics block pain and somatic sensations.
- Tetrodotoxin (TTX) is a type of neurotoxin that prevents the opening of voltage-gated sodium channels.
- When TTX inserts into VG-Na+ channels, it prevents the opening of the channels, and pain signals do not reach the CNS.
Conduction of Nerve Impulses
- Continuous conduction occurs in unmyelinated fibers and muscle fibers, involving step-by-step depolarization and repolarization.
- Impulses propagate over short distances in continuous conduction.
- Saltatory conduction occurs in myelinated axons, where the impulse "leaps" from node to node.
- In saltatory conduction, the uneven distribution of voltage-gated channels leads to faster conduction.
Factors Affecting Propagation Speed
- Axon diameter, amount of myelination, and temperature affect the propagation speed of nerve impulses.
Encoding of Stimulus Intensity
- All nerve impulses are the same size, but the frequency of impulses and the number of sensory neurons activated by the stimulus encode stimulus intensity.
Signal Transmission at Synapses
- Synapses are junctions between neurons or between a neuron and an effector.
- There are two types of synapses: electrical and chemical synapses.
Electrical Synapses
- Electrical synapses involve the direct transmission of ions through gap junctions, allowing for faster communication and synchronization.
- Advantages of electrical synapses include faster communication, direct connection, and synchronization.
Chemical Synapses
- Chemical synapses involve the release of neurotransmitters (NTs) from the presynaptic neuron into the synaptic cleft, which then bind to receptors on the postsynaptic neuron.
- The binding of NTs to receptors leads to a postsynaptic potential, which can be either excitatory or inhibitory.
Postsynaptic Potentials
- Excitatory postsynaptic potentials (EPSPs) are depolarizing, while inhibitory postsynaptic potentials (IPSPs) are hyperpolarizing.
- A postsynaptic neuron can receive many signals at once, and the sum of these signals determines the effect on the neuron.
Neurotransmitters
- Neurotransmitters are classified into small molecule neurotransmitters, neuropeptides, and gas neurotransmitters.
- Examples of small molecule neurotransmitters include acetylcholine, amino acids, and biogenic amines.
- Examples of neuropeptides include substance P, enkephalins, and endorphins.
Acetylcholine
- Acetylcholine is an excitatory neurotransmitter at neuromuscular junctions and opens ligand-gated cation channels.
- It is inactivated by acetylcholinesterases.
Amino Acids
- Glutamate and aspartate are excitatory neurotransmitters, while GABA and glycine are inhibitory neurotransmitters.
- Glutamate is inactivated via reuptake.
Excitotoxicity
- Excitotoxicity occurs when there is an excess of glutamate in the interstitial fluid of the CNS, leading to the destruction of neurons.
Biogenic Amines
- Biogenic amines include dopamine, serotonin, and norepinephrine, which are involved in various physiological processes such as emotional response, addictive behavior, and regulation of mood.
Neural Circuits
- Neural circuits are complex networks of interconnected neurons.
- Types of circuits include simple series, diverging, converging, reverberating, and parallel after-discharge circuits.
Regeneration and Repair of Nervous Tissue
- The nervous system exhibits plasticity, but neurons have a limited ability to regenerate themselves.
- Regeneration is possible in the PNS, but not in the CNS.
Neurological Disorders
- Guillain-Barré syndrome is an acute, demyelinating disorder of the PNS, characterized by demyelination and acute inflammatory demyelinating polyneuropathy.
- Multiple sclerosis is an immune-mediated inflammatory disease of the CNS, characterized by demyelination and sclerosis of the white matter.Here are the study notes in bullet points:
The Spinal Reflexes
- A spinal reflex is a fast, automatic, unplanned sequence of actions that occurs in response to a particular stimulus.
- There are different types of reflexes:
- Somatic reflex: contraction of skeletal muscle
- Autonomic reflex: via autonomic nervous system (ANS)
- Cranial reflex: integration in brain stem
- Spinal reflex: integration in spinal cord grey matter
Components of a Reflex Arc
- A reflex arc consists of:
- Receptor (detects stimulus)
- Afferent neuron (transmits signal to CNS)
- Integration center (spinal cord or brain stem)
- Efferent neuron (transmits signal to effector)
- Effector (responds to stimulus)
Types of Reflexes
- Stretch reflex:
- Controls muscle length by causing muscle contraction in response to stretching of the muscle
- Examples: tapping on tendons attached to knee, wrist, elbow, and ankle joints
- Monosynaptic, ipsilateral reflex arc
- Tendon reflex:
- Feedback mechanism to control muscle tension by causing muscle relaxation
- Ipsilateral, polysynaptic reflex arc
- Receptors: tendon (Golgi tendon) organs detect and respond to changes in muscle tension
- Flexor (withdrawal) reflex:
- Polysynaptic, ipsilateral, intersegmental reflex arc
- Withdrawal of limb from stimulus
- Crossed extensor reflex:
- Acts with the flexor reflex
- Helps maintain balance
- Contralateral, polysynaptic reflex arc
- Reciprocal innervation prevents muscle immobilization
Reflexes and Diagnosis
- Reflexes can be used to diagnose neurological disorders
- Examples: patellar reflex, Achilles reflex, Babinski reflex
The Brain
- The brain is protected by:
- Cranial bones
- Cranial meninges (pia, arachnoid, and dura mater)
- Cerebrospinal fluid (CSF)
- The brain is supplied with blood via internal carotid and vertebral arteries
- The blood-brain barrier (BBB) protects the brain from harmful substances
- The brain is composed of:
- Cerebrum
- Cerebellum
- Brain stem (midbrain, pons, and medulla oblongata)
- Diencephalon (thalamus, hypothalamus, and epithalamus)
Blood Flow to the Brain
- The brain utilizes about 20% of the body's oxygen supply
- Any interruption of oxygen supply can result in weakening, permanent damage, or death of brain cells
Blood-Brain Barrier (BBB)
- The BBB is a barrier between the blood and the brain
- It is composed of tight junctions between endothelial cells of capillaries and a thick basement membrane
- Astrocytes secrete chemicals that maintain the permeability characteristics of the BBB
- The BBB can prevent the entry of therapeutic drugs
Cerebrospinal Fluid (CSF)
- CSF is a clear, colorless liquid that:
- Carries oxygen, glucose, and chemicals
- Circulates through ventricles and subarachnoid space
- Total volume: 80-150 mL in adults
- Formation of CSF:
- Produced by choroid plexuses in ventricles
- Reabsorbed into blood via arachnoid villi at a rate of 20 mL/hr
Hydrocephalus
- Excess CSF accumulates in ventricles, causing CSF pressure to rise
- Can occur after head trauma, meningitis, or subarachnoid hemorrhage
- Can be relieved by draining excess fluid
Brain Stem
- The brain stem is composed of:
- Midbrain
- Pons
- Medulla oblongata
- The medulla oblongata is the most inferior part of the brain stem
- It contains:
- Respiratory rhythmicity center
- Cardiovascular center
- Reticular formation
The Midbrain
- The midbrain lies between the pons and the diencephalon
- It contains:
- Cerebral peduncles
- Superior and inferior colliculi
- Red nucleus
- Substantia nigra
The Cerebellum
- The cerebellum is attached to the brain stem via three pairs of cerebellar peduncles
- It regulates posture, balance, and movement
- Damage to the cerebellum can result in ataxia (loss of muscle coordination)
The Diencephalon
- The diencephalon is composed of:
- Thalamus
- Hypothalamus
- Epithalamus
- The thalamus is a major relay station for sensory impulses
- The hypothalamus regulates autonomic functions, such as hunger, thirst, and body temperature
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This quiz is based on the copyright permission form CP241/PA2 for legal services, specifically designed for BSPD 211 and 212 courses in the physiology department.
