Chapter 1 - The Nervous System Flashcards
K+/Na+: which cation has a high concentration outside a neuron?
Na+
What is the purpose of a neuron’s ATPase pump?
It generates the asymmetrical concentration gradient of Na+ and K+ across the cell membrane. It pumps Na+ out and K+ in.
What cation movement generates an action potential?
a rush of Na+ ions entering the cell once a threshold potential has been reached
What are the ion channels in an axon called?
ionophores
What is hyperpolarization?
As K+ rushes out of the neuron during repolarization, the membrane potential passes its original resting state.
What is saltatory conduction?
An action potential on myelinated nerves seems to jump from node to node.
How does ATP affect the binding of actin and myosin?
It reduce’s myosin head affinity for actin.
What role does the pituitary gland play?
It is the master endocrine gland, receiving information from the hypothalamus.
Where do sympathetic nerves originate?
from the thoracic and lumbar portions of the spinal cord
Where do somatic nerves synapse?
directly on skeletal muscle
What are first-order sensory neurons?
They carry information from the receptive field to the spinal cord.
What is troponin?
a multi-subunit binding protein that interacts with actin, tropomyosin, and Ca2+
Which cerebral lobe is associated with touch and stretch sensation?
parietal
What hormones does the adrenal medulla release?
epinephrine and norepinephrine
Where and how do exocrine glands secrete substances?
into the lumen by way of a duct
Under aerobic conditions when glucose is oxidized to CO2 and H2O, how much ATP is formed?
36 molecules ATP
As a receptor potential increases above a threshold, what happens to the action potential of the neuron?
It will increase in frequency, not in amplitude.
An active neuron has greater permeability to Na+ or K+?
Na+
What is the purpose of histamines?
They cause an increase in blood flow to regions that have been affected by allergy, infection, or injury.
What is the purpose of erector muscles?
They straighten the hair shaft.
What is the protein that coils around actin?
tropomyosin
What do mast cells secrete?
histamines
Where is acetylcholine synthesized?
in the cytosol of a neuron
When muscle is in a relaxed state, what is bound to the myosin heads?
ATP
Where is reticulin found?
in the spleen and lymph nodes
Where are the ganglia in the parasympathetic division?
near or in the organs they innervate
How does calcium leave the cytosol of a muscle cell?
Ca2+ - ATPase pump
Under anaerobic conditions when glucose is metabolized to lactate, how much ATP is formed?
2 molecules ATP
How does the size of a motor unit affect the strength of contraction?
The smaller the motor unit, the smaller the strength of contraction.
What is the power stroke?
The myosin heads bind to actin, releasing ADP and Pi, causing a conformational change that cocks the heads to 45º, pulling the actin away from the Z-line.
What is a ganglion?
grouping of nerve cell bodies
What makes bone flexible?
collagen
The autonomic nervous system can be divided into what two systems?
sympathetic and parasympathetic
What is the contractile unit of a muscle?
sarcomere
Through exercise, do muscle cells multiply or grow larger?
They just grow larger, gaining actin and myosin.
What are the areas called between myelinated areas?
nodes of Ranvier
What comprises the A-band?
myosin
Which cerebral lobe is associated with hearing and memory?
temporal
What are the glial cells called in the peripheral nervous system?
Schwann cells
What role does the hypothalamus play?
It deals with visceral activities (autonomic nervous system).
Somatic sensory input from the right side of the body will be represented by which part of the brain?
somatosensory cortex of the left cerebral hemisphere
Large/small cross-section neurons: which conduct action potentials faster?
large cross-sections
What are the glial cells called in the central nervous system?
oligodendrocytes
What cells deposits myelin on an axon
glial cells
Nodes of Ranvier have many of which ion channel?
Na+
What structural proteins do fibroblasts secrete?
- collagen - reticulin - elastin
Synapse that makes just one synaptic connection
monosynaptic reflex arc
Somatic nervous system nerves release what neurotransmitter?
acetylcholine
In actin-based regulation, what allows the muscle to contract?
Calcium binds to troponin, which causes the tropomyosin to shift its position, revealing the myosin head binding sites on actin.
What neurotransmitter do pre-ganglionic parasympathetic nerves release?
acetylcholine
Which phyla has the simplest nervous system?
Cnidaria
What are the nerves called that released norepinephrine/epinephrine?
adrenergic
Define motor neuron.
nerve cells with cell bodies in the CNS, with myelinated axons innervating skeletal muscle
What is lateral inhibition?
Overlapping receptive fields have interneurons that inhibit impulses being sent from neighbors.
In a resting state, what direction does K+ diffuse across a neuron’s membrane?
inside ► out
Which part of a neuron receives information?
dendrites
Which cerebral lobe is associated with movement and personality?
frontal
What type of protein do osteoblasts secrete?
collagen found in the bone matrix
What role does the thalamus play?
It relays visual and auditory information.
What is collagen?
a triple-stranded, insoluble, fibrous protein
What are third-order sensory neurons?
They ascend from the thalamus to a particular region of the somatosensory cortex of the cerebral hemisphere.
Equation: Nernst equation of voltage
How does myelin affect action potential?
It greatly increases the rate that action potentials are conducted.
As an action potential reaches the pre-synaptic membrane, what causes the release of neurotransmitters?
Ca2+ channels on the terminal region open, allowing calcium to rush in. The calcium causes synaptic vesicles carrying neurotransmitters to fuse with the presynaptic membrane, releasing them into the synaptic cleft.
What is acetylcholinesterase?
It is an enzyme bound to the postsynaptic membrane that hydrolyzes acetylcholine into acetate and choline.
Where are mast cells found?
in the respiratory and digestive tracts
What is the purpose of microvilli?
They increase the total absorptive area of the cell.
If a synaptic connection is inhibitory, there will be an increased permeability in the postsynaptic membrane to what ion, causing what?
K+ and Cl-, causing hyperpolarization
What is the resting voltage potential of the inside of a neuron compared to the outside?
-80 mV
Which ANS system tends to conserve energy?
parasympathetic
What are the four types of tissues?
- epithelial - nervous - muscle - connective
What are the 3 main layers of skin going deeper?
epidermis –> dermis –> subcutaneous tissue
What neurotransmitter do post-ganglionic parasympathetic nerves release?
acetylcholine
How is ATP quickly produced in muscle cells?
anaerobic metabolism
Which type of muscle has myosin-based regulation of muscle contraction?
cardic and smooth
What is a byproduct of anaerobic metabolism that builds up in muscles? What does this cause?
lactic acid ► lowers pH ► regulatory enzyme in glycolytic pathway can no longer function ► cannot carry out metabolic processes ► fatigue
What neurotransmitter do post-ganglionic sympathetic nerves release?
norepinephrine
What makes bone rigid?
Inorganic crystals: calcium phosphate and calcium carbonate
Synapse that makes at least two synaptic connections (involving interneurons)
polysynaptic reflex arc
What are second-order sensory neurons?
They ascend the spinal cord to the thalamus.
What connects muscle to the skeleton?
tendons
What does the autonomic nervous system innervate?
glands and smooth and cardiac muscle
If a synaptic connection is excitatory, there will be an increased permeability in the postsynaptic membrane to what ion, causing what?
Na+, causing depolariztion
What is elastin and where is it found?
a cross-linked protein found in organs that require elasticity
What must be present on the myosin heads for it to bind to actin?
ADP + Pi
What two main components make up the CNS?
brain and spinal cord
Somatic sensory pathways typically have how many neurons?
three
How does the number of motor units affect the strength of contraction?
The more motor units utilized, the stronger the contraction.
What is the sympathetic trunk?
chains of sympathetic ganglia on either side of the spinal cord
In an active state, what direction does Na+ diffuse across a neuron’s membrane?
outside ► in
How does acetylcholine propagate an action potential to the next neuron?
It binds to postsynaptic membrane receptors, inducing a conformational change to allow Na+ through, allowing depolarization of the postsynaptic neuron.
Where do endocrine glands secrete substances?
into the blood
Which type of muscle has actin-based regulation of muscle contraction?
skeletal
What is the more prominent nerve in the parasympathetic system?
vagus nerve
In the PNS, which direction do afferent neurons carry information?
PNS ► CNS (they are sensory)
A resting neuron has greater permeability to Na+ or K+?
K+
What is the most abundant protein in mammals?
collagen
What is the ultimate determinant of muscle contraction?
concentration of ATP in muscle cells
Where do parasympathetic nerves originate?
from the sacral portion of the spinal cord and the midbrain and medulla
In the PNS, which direction do efferent neurons carry information?
CNS ► PNS (they are motor)
In the sympathetic division, which nerve complex does not synapse with post-ganglionic nerves?
Those that synapse directly on ganglia within the adrenal medulla.
What does the somatic nervous system innervate?
skeletal muscle
What is the purpose of tight junctions?
They act as a permeability barrier and hold cells together.
What is the purpose of desmosomes?
They hold cells together and to the basal lamina.
What is the region between actin filaments, where there is only myosin?
H-zone
What are the nerves called that release acetylcholine?
cholinergic
What type of connective tissue do chondrocytes secrete?
cartilage
As an action potential reaches a muscle cell, how and where does it affect the movement of calcium?
It passes down each T-tubule, stimulating the release of Ca2+ from the sarcoplasmic reticulum, where it has a high concentration. Ca2+ flows down its concentration gradient into the cytosol, where it binds to troponin.
What neurotransmitter do pre-ganglionic sympathetic nerves release?
acetylcholine
Sympathetic/parasympathetic: which system has longer preganglionic nerves?
parasympathetic
What protein unit makes up actin?
G actin (globular-actin)
What opens during an axon’s repolarization?
K+ channels
What is the purpose of gap junctions?
They allow water-soluble molecules to pass between cells’ cytoplasms, allowing cells to function as a unit.
Which cerebral lobe is associated with vision?
occipital
Which ANS system tends to prepare for “fight-or-flight”?
sympathetic
How does the CNS determine the magnitude of a stimulus being received?
it is based on the frequency of action potentials
Do pain receptors undergo sensory adaptation?
No
