Q1 Flashcards
What is the effect of sympathetic stimulation on the eyes?
Contracts the meridional fibers of the iris, dilating the pupil
Parasympathetic stimulation contracts the circular muscle of the iris, constricting the pupil.
What is the effect of parasympathetic stimulation on the GI tract?
Increases activity by promoting peristalsis and relaxing sphincters
Strong sympathetic stimulation inhibits peristalsis and increases sphincter tone.
How does sympathetic stimulation affect the heart?
Increases both rate and force of heart contraction
Parasympathetic stimulation decreases rate and strength of contraction.
What is the effect of sympathetic stimulation on the liver?
Causes glucose to be released
Parasympathetic stimulation causes slight glycogen synthesis.
What is the effect of sympathetic stimulation on the lungs?
Causes bronchodilation
Parasympathetic stimulation causes bronchoconstriction.
What is a key characteristic of electrical synapses?
They have direct cytoplasmic continuity via gap junctions, causing no synaptic delay
Located in CNS, smooth muscle, and cardiac muscle.
What distinguishes chemical synapses from electrical synapses?
Chemical synapses have synaptic delays due to the transit time of chemical mediators
Majority of neurons in the CNS have chemically mediated synapses.
What is the primary function of the dorsal column-medial lemniscal system?
Transmits sensory information rapidly with a high degree of spatial orientation
Signals are transmitted at velocities of 30-110 m/sec.
What is the anatomy of a synapse?
A junction point between neurons, with a synaptic cleft usually 200 to 300 angstroms wide
Contains transmitter vesicles and mitochondria for neurotransmitter synthesis.
What triggers the release of neurotransmitters at a synapse?
Depolarization of the presynaptic membrane opens voltage-gated calcium channels, allowing calcium to flow in
Calcium binds with proteins to cause release of neurotransmitters.
What percentage of the body’s total metabolism does brain metabolism account for?
15%
Neuronal metabolism can increase by 100% to 150% during high brain activity.
What is the primary energy source for the brain under normal conditions?
Glucose derived from the blood
Transport through the neuronal cell membrane is not dependent on insulin.
What are the major levels of the central nervous system?
Spinal cord, subcortical level, cortical level
Each level has distinct functions and controls.
What functions does the spinal cord perform independently of the brain?
Walking movements, reflexes to withdraw from pain, support against gravity, control of local blood vessels
It acts as a conduit for signals between the body and brain.
What structures are included in the subcortical level of the brain?
Medulla, pons, mesencephalon, hypothalamus, thalamus, cerebellum, basal ganglia
Most subconscious activity occurs here.
What is the role of the cortical level in the CNS?
Converts functions of lower brain centers into precise functions
Essential for thought processes and requires lower brain centers for wakefulness.
What is the effect of sympathetic stimulation on the eyes?
Contracts the meridional fibers of the iris, dilating the pupil
Parasympathetic stimulation contracts the circular muscle of the iris, constricting the pupil.
What is the effect of parasympathetic stimulation on the GI tract?
Increases activity by promoting peristalsis and relaxing sphincters
Strong sympathetic stimulation inhibits peristalsis and increases sphincter tone.
How does sympathetic stimulation affect the heart?
Increases both rate and force of heart contraction
Parasympathetic stimulation decreases rate and strength of contraction.
What is the effect of sympathetic stimulation on the liver?
Causes glucose to be released
Parasympathetic stimulation causes slight glycogen synthesis.
What is the effect of sympathetic stimulation on the lungs?
Causes bronchodilation
Parasympathetic stimulation causes bronchoconstriction.
What is a key characteristic of electrical synapses?
They have direct cytoplasmic continuity via gap junctions, causing no synaptic delay
Located in CNS, smooth muscle, and cardiac muscle.
What distinguishes chemical synapses from electrical synapses?
Chemical synapses have synaptic delays due to the transit time of chemical mediators
Majority of neurons in the CNS have chemically mediated synapses.
What is the primary function of the dorsal column-medial lemniscal system?
Transmits sensory information rapidly with a high degree of spatial orientation
Signals are transmitted at velocities of 30-110 m/sec.
What is the anatomy of a synapse?
A junction point between neurons, with a synaptic cleft usually 200 to 300 angstroms wide
Contains transmitter vesicles and mitochondria for neurotransmitter synthesis.
What triggers the release of neurotransmitters at a synapse?
Depolarization of the presynaptic membrane opens voltage-gated calcium channels, allowing calcium to flow in
Calcium binds with proteins to cause release of neurotransmitters.
What percentage of the body’s total metabolism does brain metabolism account for?
15%
Neuronal metabolism can increase by 100% to 150% during high brain activity.
What is the primary energy source for the brain under normal conditions?
Glucose derived from the blood
Transport through the neuronal cell membrane is not dependent on insulin.
What are the major levels of the central nervous system?
Spinal cord, subcortical level, cortical level
Each level has distinct functions and controls.
What functions does the spinal cord perform independently of the brain?
Walking movements, reflexes to withdraw from pain, support against gravity, control of local blood vessels
It acts as a conduit for signals between the body and brain.
What structures are included in the subcortical level of the brain?
Medulla, pons, mesencephalon, hypothalamus, thalamus, cerebellum, basal ganglia
Most subconscious activity occurs here.
What is the role of the cortical level in the CNS?
Converts functions of lower brain centers into precise functions
Essential for thought processes and requires lower brain centers for wakefulness.
What does the autonomic nervous system (ANS) control?
Most visceral functions of the body
The ANS influences involuntary bodily functions such as heart rate and digestion.
How quickly can the ANS change heart rate?
In three to five seconds
The ANS can rapidly adapt bodily functions to environmental changes.
What are the two main components of the autonomic nervous system?
- Sympathetic nervous system
- Parasympathetic nervous system
What activates the autonomic nervous system?
Centers located in the spinal cord, brain stem, and hypothalamus
Additionally, portions of the cerebral cortex also play a role.
What type of reflexes does the ANS operate through?
Visceral reflexes
These reflexes involve subconscious sensory signals from visceral organs.
What is the average blood flow through the brain of an adult?
50 to 65 mL/100 g of brain tissue/min
This flow is critical for maintaining brain metabolism.
What anatomical structures form the circle of Willis?
- Two carotid arteries
- Two vertebral arteries
Which factors contribute to the regulation of cerebral blood flow?
- CO2 concentration
- H+ concentration
- O2 concentration
- Substances released from astrocytes
Which type of brain tissue has a higher number of capillaries?
Gray matter
The metabolic rate of gray matter is about four times greater than that of white matter.
True or False: Brain capillaries are more leaky than blood capillaries elsewhere.
False
Brain capillaries are less leaky due to supportive glial cells.
What are the three major components of the analgesia system?
- Periaqueductal gray and periventricular areas
- Raphe magnus nucleus
- Pain inhibitory complex in the dorsal horns
What substances are released as part of the analgesia system?
- Enkephalin
- Serotonin
What are the breakdown products of the large protein molecules related to the endogenous opiate system?
- β-endorphin
- Met-enkephalin
- Leu-enkephalin
- Dynorphin
What is the ‘alarm’ response also known as?
‘Fight or flight’ response
This response is triggered by strong activation of the sympathetic nervous system.
List the results of the ‘alarm’ response.
- Increased arterial pressure
- Increased blood flow to active muscles
- Decreased blood flow to non-essential organs
- Increased rates of cellular metabolism
- Increased blood glucose concentration
- Increased glycolysis
- Increased muscle strength
- Increased mental activity
- Increased rate of blood coagulation
What occurs during neuronal inhibition?
Inhibition occurs via the opening of chloride ion channels, increase in potassium ion conductance out of the neuron, and activation of receptor enzymes.
How do chloride ions contribute to neuronal inhibition?
Chloride ions diffuse into the postsynaptic neuron, increasing negativity inside and causing hyperpolarization.
What is presynaptic inhibition?
Presynaptic inhibition occurs at the presynaptic terminals due to the release of an inhibitory substance, often GABA, which opens anion channels.
What is the role of cerebrospinal fluid (CSF)?
CSF cushions the brain, is present in the ventricles and subarachnoid space, and forms at a rate of 500 mL/day.
Where does CSF primarily originate?
About 2/3 of CSF originates from the choroid plexus in the lateral ventricles.
Describe the flow of CSF.
CSF flows from the lateral ventricles to the third ventricle, then down the aqueduct of Sylvius to the fourth ventricle, and into the cisterna magna.
How is CSF absorbed?
CSF is absorbed through arachnoidal villi into the venous blood, acting as valves to prevent backflow.
What does the anterolateral pathway transmit?
The anterolateral pathway transmits sensory signals such as pain, heat, crude tactile sensations, and itch.
Where do anterolateral fibers originate?
Anterolateral fibers mainly originate in dorsal horn laminae I, IV, V, and VI.
How does signal transmission occur in the anterolateral pathway?
Signals cross into the anterior commissure and ascend via the anterior and lateral spinothalamic tracts to the brain.
What is the process of neuronal excitation?
Excitation occurs through the opening of sodium channels, depressed conduction of chloride or potassium channels, and metabolic changes in the postsynaptic neuron.
What is the excitatory postsynaptic potential?
The excitatory postsynaptic potential raises the resting membrane potential from -65 mV to -45 mV.
What are synaptic transmitters?
Synaptic transmitters include over 50 chemical substances, such as small-molecule transmitters and neuropeptides.
What are examples of small-molecule, rapidly acting transmitters?
Examples include acetylcholine, norepinephrine, and ATP.
What is the function of neuropeptides?
Neuropeptides usually cause more prolonged actions compared to small-molecule transmitters.
