midterm1 Flashcards
which system exerts control by sending hormones through the blood and lymphatic systems?
endocrine
T/F- all body cells have membrane potential
true
what are excitable tissues
They are tissues that when excited, change their resting potential to produce electrical signals.
when membrane potential becomes more positive (moving towards 0mV), it is said to be _____
depolarized
when the membrane returns to its normal resting potential after being depolarized
repolarization
when there is an increase in negative membrane potential, i.e. the potential becomes more polarized or more negative
hyperpolarization
channels which are always open (unregulated flow), that allow water soluble ions to cross the plasma membrane. Each ion has it’s own specialized channel it can leak through.
leak channels
this type of channel has gates which can either be opened or closed. Whether the gate is opened or closed is determined by the protein’s 3-dimensional conformation.
gated channels
gated channels which open or close in response to a change in membrane potential
voltage gated channels
gated channels which change in response to the binding of a specific chemical messenger to a membrane receptor in close association with the channel.
chemically gated channels
gated channels which respond to mechanical changes such as stretching or other types of deformation.
mechanically gated channels
gated channels which open or close in response to local changes in temperature (heat or cold)
thermally gated channels
substances what have low resistance and therefore provide little hindrance to current flow, ex. electrical wire, ICF and ECF.
conductors
substances which have high resistance and therefore impede the movement of charge, ex. plastic (which is why it surrounds wires), body lipids.
insulators
the gradual spread and loss of a graded potential
decremental loss
give examples of graded potentials
postsynaptic potentials, receptor potentials, end-plate potentials, pacemaker potentials, slow wave potentials
overshoot
the portion of the action potential during which the potential is reversed
when a excitable membrane is triggered to undergo an action potential
fire
Pna+
At threshold potential, there is an explosive increase in Na+ permeability, symbolized by Pna+, as the membrane swiftly becomes 600 times as permeate to Na+ as to K+
the part of the action potential due to the Na+ influx
rising phase
the part of the action potential brought on by K+ efflux
falling phase
the ____ and ___ of a neuron is the input zone
cell body and dendrites
Once initiated, the velocity, or speed, with which an action potential travels down the axon depends on which two factors
(1) whether the fibre is myelinated and (2) the diameter of the fibre. Contiguous conduction occurs in unmyelinated fibres
most common excitatory inhibitor in the brain
glutamate
most common inhibitor neurotransmitter
GABA
are EPSPs and IPSPs action or graded potentials?
graded potentials
membranous sacs containing hydrolytic enzymes
lysosomes
membranous sacs containing oxidative enzymes
peroxisomes
dispersed within the cytosol and facilitate intracellular reactions involving degradation, synthesis, and transformation of small organic molecules
intermediary metabolism enzymes
maintain asymmetric cell shapes, coordinate complex cell movements, transport of secretory vesicles, main structural and functional component of cilia/flagella
microtubules
the six organelles
the ER, Golgi, lyosomes, peroxisomes, mitochondria and vaults.
site of synthesis of proteins and lipids destined for the cell membrane and secretion
rough ER
muscle cells have a ____stores calcium, needed to facilitate muscle contraction and movement.
sarcoplasmic reticulum
membrane enclosed sacs, which are not in physical contact with one another. They are thin in the middle but have dilated, bulging edges.
cisternae
are peroxisomes smaller than lysosomes?
yes
an antioxidant enzyme that decomposes potent H2O2 into harmless H2O and O2
catalase
purpose of mitosis in multicellular organisms
growth and replacement
the interval of time between cell division (as all cells capable of dividing alternate between periods of mitosis and nondivsion)
interphase
chromatin condenses and duplicates (creates inter chromatids) but remain joined at the cetromere. Centrioles divide and the daughter centrioles move to opposite ends of the cell where they form mitotic spindles (made of microtubules). The membrane around the nucleus starts to break down
prophase
Nuclear membrane disappears. The chromosomes align in the middle and attach to the mitotic spindles at their centromeres.
metaphase
The centromeres split and separate the chromatids, moving the chromosomes toward opposite ends of the cell. Molecular motors pul the chromosomes along the spindle fivers (46 chromosomes at either end of the cell)
anaphase
the cytoplasm divides through the formation of an actin contractile ring forming to diploid cells (each with a full set of chromosomes). The spindles disassemble and the chromosomes uncoil into their decondensed chromatin form while a new nuclear membrane forms.
telophase
Any flow of electrical charges is called a ___
current
T/F - An impulse may be triggered during the refractory period, provided the stimulus is strong
true
the part of the nueron that contains the nucleus and organelles; also called soma.
cell body
side branches that extend off the axon.
collateral
Because of the all-or-none nature of action potentials, the ____ of a stimulus affects the number of action potentials, not the speed of their propagation
strength
areas located between the myelinated regions where the axonal membrane is exposed to the ECF.
nodes of ranvier
which nerve fibres can regenerate?
Cut axons in the peripheral nervous system can regenerate, whereas those in the central nervous system cannot
a tube formed by Schwann cells when there is a cut axon in a peripheral
regeneration tube
the five events that occur at the synaptic cleft
- The action potential of the presynaptic neuron triggers voltage-gated calcium channels in the synaptic knob.
- This releases calcium ions into the cleft.
- The addition of calcium causes the release of neurotransmitters through exocytosis.
- The neurotransmitters diffuse across the gap and bind to postsynaptic receptors.
- This activates gated ion channels on the postsynaptic neuron.
These five events produce a graded potential in the postsynaptic neuron.
A neuron may terminate on what 3 structures
a muscle, a gland, or another neuron
when a neuron terminates on a muscle or a gland, the neuron is said to
innervate or supply the structure
____allow an influx of potassium or chloride ions, which hyperpolarizes the membrane and reduces the probability that the neuron will reach threshold
Inhibitory synapses - leading to an IPSP
neurotransmitters are removed from the synaptic cleft by______
diffusion, enzyme degradation, or absorption by the presynaptic axon terminal.
the total potential in the postsynaptic neuron; or sum total of all EPSPs and IPSPs occurring at approximately the same time
grand post synaptic potential
two ways a postsynaptic neuron can be brought to threshold
temporal and spatial summation
Only if an excitatory presynaptic signal is_______ through summation will the information be passed on.
reinforced by other supporting signals
why do action potentials initiate at the axon hillock?
because this region has a much greater density of voltage-gated Na+ channels than anywhere else in the neuron.
larger molecules made up of anywhere from 2 to about 40 amino acids
neuropeptides
where are neuropeptides synthesized?
in the neuronal cell body in the endoplasmic reticulum and Golgi complex and are subsequently moved by axonal transport along the microtubular highways to the axon terminal.
chemical messengers that do not cause the formation of EPSPs or IPSPs, but rather bring about long-term changes that subtly modulate – depress or enhance – traction of the synapse. They bind to neuronal receptors at non-synaptic sites – not at the sub synaptic membrane – and they do not directly alter membrane permeability and potential.
neuromodulators
the depression of synaptic effectiveness because a third neuron between a presynaptic ending and post synaptic ending can influence the activity.
presynaptic inhibition
results in the enhancement of synaptic effectives
presynaptic facilitation
any biological substance that when consumed will in some way alter the biological function of the organism.
a drug
4 possible drug actions
(1) altering the synthesis, axonal transport, storage, or release of a neurotransmitter; (2) modifying neurotransmitter interaction with the postsynaptic receptor; (3) influencing neurotransmitter reuptake or destruction; and (4) replacing a deficient neurotransmitter with a substitute transmitter.
injection of cocaine blocks _______
reuptake of the neurotransmitter dopamine at presynaptic terminals.
why is cocaine addictive?
it causes long-term molecular adaptations of the involved neurons such that they cannot transmit normally across synapses without increasingly higher doses of the drug. The postsynaptic cells become accustomed to high levels of stimulation and become ‘’hooked’’ on the drug
desensitization to an addictive drug so that the user needs greater quantities of the drug to achieve the same effect.
tolerance
attributable to a deficiency of dopamine in the basal nuclei, a region of the brain involved in controlling complex movements. This movement disorder is characterized by muscular rigidity and involuntary tremors at rest, such as involuntary rhythmic shaking of the hands or head
parkinsons disease
act at different synaptic sites to block inhibitory impulses while leaving excitatory inputs unchecked
tetanus toxin and strychnine
prevent the release of GABA from inhibitory presynaptic input terminating at neutrons that supply skeletal muscles. Unchecked excitatory input to these neurons result in uncontrolled muscle spams (early in the disease this is the jaw- lockjaw)
tetanus toxin
ompetes with glycine at the postsynaptic receptor site. This poison combines with the receptor but does not directly alter the potential of the postsynaptic cell in any way, instead it blocks the receptor so that it is not available for interaction with glycine when the latter is released from the inhibitory presynaptic ending
strychnine
the branching of axon terminals so that a single cell synapses with and influences many other cells.
divergence
the four types of chemical messengers
- paracrines, concerned with local cells;
- neurotransmitters, operating in neuronal synapses;
- hormones, produced upon demand by endocrine glands and ranging over the whole body; and
- neurohormones, released by neurosecretory cells.
tiny tunnels that bridge the cytoplasm of neighbouring cells. Act as the most intimate means of intercellular communication. Small ions and molecules are directly exchanged between interacting cells without ever entering the extracellular fluid.
gap junctions
the presence of identifying markers on the surface of some cells allows them to directly link up transiently and interact with cells; for ex. phagocytes recognize and selectively destroy only undesirable cells by this means.
transient direct linkup
local chemical messengers whose effect is exerted only on neighbouring cells in the immediate environment of their site of secretion. They are chemical messengers specifically released to accomplish a a particular response.
- They are distributed by simple diffusion and therefore only act within short distances.
- The are inactivated quickly by local enzymes so they never enter the blood stream.
paracrines
long-range chemical messengers that are specifically secreted into the blood by endocrine glands in response to an appropriate signal. The blood carries these messengers to their target, where they exert their effect
hormones
hormones released into the blood by neurosecretory neurons; which can respond and conduct electrical signals like ordinary neurons.
neurosecretory hormones
a device that receives energy from one system and transmits it in a different form to another system.
transducer
the process by which incoming signals are conveyed to the target cell’s interior for execution
signal transduction
synapses which involve rapid responses. Ex. some neurotransmitters function through intracellular second-messenger systems
fast synapses
mode of synaptic transmission used by some neurotransmitters, such as serotonin, involves the activation of intracellular second messengers.lead to responses take longer and often last longer than those accomplished by fast synapses.
slow synapses
the study of homeostatic chemical adjustments and other activities accomplished by hormones, which are secreted into the blood by endocrine glands.
endocrinology
highly water-soluble hormones which have low lipid solubility. Most of these hormones are peptide or protein hormones
hydrophilic hormones
one group of hydrophilic hormones, consisting of specific amino acids arranged in a chain of varying length depending on the hormone itself.
peptides
another group of hydrophilic hormones which are derived from the amino acid, tyrosine, and are specifically secreted by the adrenal medulla.
catecholamines
hormones with a high lipid-solubility and poor water-solubility.
lipophilic hormones
a lipophilic hormone secreted specifically by the thyroid gland. It is an iodinated tyrosine derivative, but still behaves very differently from catecholamines (even though they are sometimes grouped together as amine hormones.
thyroid hormone
hormones secreted by the adrenal cortex and sex hormones which are derived from cholesterol.
steroid hormones
hydrophilic hormones dissolve in ______
plasma
Preprohormones, or precursor proteins, are synthesized by______
ribosomes on the ER
lipophilic hormones are transported by____
plasma proteins
the common precursor for all steroid hormones.
cholesterol
hormones that are poorly soluble in lipid, cannot pass through the lipid membrane barriers of their target cells. Instead, they bind with specific receptors located on the outer plasma membrane surface of the target cell.
The hydrophilic peptides and catecholamines
hormones that can easily pass through the surface membrane to bind with specific receptors located inside the target cell
The lipophilic steroids and thyroid hormone
hormonal responses are________than neural responses:
slower and longer-lasting
amblyopia
lazy eye
the CNS is composed of….
the brain and spinal cord
the PNS is composed of
nerve fibres that carry information between the CNS and other parts of the body (the periphery).
division - away from the periphery, carries information to the cns
afferent
division that carries instructions FROM the cns to the effector organs
efferent
consists of the fibres of the motor neurons that supply the skeletal muscles
somatic nervous system
consists of fibres that innervate smooth muscle, cardiac muscle, and glands
autonomic nervous system
three classes of neurons
afferent (sensory), efferent (motor), or interneurons
which classification of neuron is shaped differently than the other two?
afferent neurons
generates action potentials in response to a particular type of stimulus
sensory receptor
passes from the cell body into the spinal cord
control axon
lie entirely within the CNS, about 99% of neurons belong to this category
interneurons
type of neuron: important in integrating peripheral responses to peripheral information and interconnections between these neurons are responsible for the abstract phenomena associated with the ‘’mind’’ such as thoughts, emotions, memory, creativity, intellect, motivation – the least understood functions of the nervous system
interneurons
_____ cellsserve as the connective tissue of the CNS and help support neurons physically and metabolically
glial cells
90% of the cells within the CNS are NOT NEURONS, BUT ________
GLIAL CELLS or neuroglia
homeostasis is usually controlled by which feedback loop?
negative feedback loop
responsible for detecting any disruptions to the balance between internal and external environments, and helps to identify when the loop has reached the set point, or the state required for homeostasis
sensor
(feedback loop)initiates the appropriate response after taking into consideration the degree of variation from the set point and how much the variable needs to adjust
integrator
an react against those changes as necessary to restore a state of homeostasis
effector
this feedback loop is less common in the body
positive feedback loop
Mitosis occurs in ______ for growth and repair of cells
somatic cells
while meiosis occurs in _____of cells for reproduction.
germ line
type of protein: loosely attached to either the inner or outer surface of the membrane
Peripheral proteins(enzymes, cytoskeleton anchors, etc.)
type of protein: extend across the phospholipid bilayer
Integral proteins(channels, transporters, etc.)
is epinephrine a neurotransmitter?
no, its a hormone
is norepinephrine a neurotransmitter?
yes
___ serve as connective tissue in the CNS and help support neurons both physically and metabolically.
glial cells
the most abundant glial cells.
astrocytes
form the insulating myelin sheaths around axons in the CNS. Each one has several long projections which wrap around a section of an interneuronal axon to form a patch of myelin and play a role in defence of brain as phagocytic scavengers
ogliodendrocytes
CNS phagocytes. immune cells of the CNS. cousins of monocytes. derived from bone marrow tissue that gives rise to monocytes
microglia
In instances of potential harm, ____ retract their branches, and become highly mobile, moving toward the affected area to remove foreign invaders or tissue debris. Here they release destructive chemicals to assault the invader.
microglial
line the fluid-filled cavities of the CNS and produce CSF. They also serve as neural stem cells with the potential to form new neurons and glial cells.
ependymal cells
four interconnected chambers within the interior of the brain that are continuous with the narrow, central canal.
ventricles
a hollow tunnel through the middles of the spinal cord which connects to the ventricles and contains CSF.
central canal
three membranes that lie between the bony covering and the nervous tissue.
meninges
the outermost layer which is tough and inelastic. These layers adhere closely except for some regions which are separated by cavities.
dura matter
blood filled cavities which separate some regions of the dura-mater.
dural sinuses
larger blood filled cavities found in the dura mater.
venous sinuses
a delicate, richly vascularized layer with a cobweb-like appearance.
arachnoid matter
the spaces between the arachnoid layer and the underlying pia mater which is filled with CSF.
arachnoid space
protrusions of arachnoid tissue, which penetrate through gaps in the overlying dura and project into the dural sinuses. CSF is reabsorbed across the surfaces of these villi into the blood circulating the sinuses.
arachnoid villi
the most fragile layer. It is highly-vascular and closely adheres to the surface of the brain and spinal cord, running along all the ridges and valleys. In certain areas it dips deeply into the brain to bring a rich blood supply into close contact with the ependymal cells lining the ventricles. This relationship is important in the formation of CSF.
pia matter
richly vascularized mass found in particular regions of the ventricle cavities of the brain.
choroid plexus
four subsections of the brain
From the most primitive to the most advanced, these are the brain stem, cerebellum, diencephalon, and cerebrum.
the brains largest region
the cerebrum
the oldest (in evolutionary terms) part of the brain which is continuous with the spinal cord. It consists of the midbrain, pons, and medulla. plays a role in sleep/wake cycle
- It is the origin of most peripheral cranial nerves.
- Regulates muscles reflexes involved with equilibrium and posture.
- Receives and integrates synaptic input from spinal cord; arousal and activation of cerebral cortex.
brain stem
Maintains balance, proprioception, enhances muscle tone and coordinates planned skilled voluntary muscle activity.
cerebellum
located on top of the brain stem, in the interior of the cerebrum. houses the hypothalamus and thalamus.
The diencephalon
controls homeostatic functions important for maintaining stability of the internal environment.
hypothalamus
responsible for the inhibition of muscle tone, the coordination of slow, sustained movements and the suppression of useless patterns of movement.
basal nuclei
area of the cerebrum that connects the left and right hemispheres and acts as an “information highway.”
corpos callosum
located in regions of the cortex responsible for perception of senses in layer 4, These cells are responsible for initial processing of sensory input in the cortex.
stellate cells
cells located in the cortical areas that control the output to skeletal muscles, located in layer 5. These cells send fibres down the spinal cord from the cortex to terminate on efferent motor neurons that innervate skeletal muscles.
pyramidal cells
located posteriorly (at the back of the head), carry out the initial processing of visual input.
occipital lobes
responsible for receiving and processing sensory input. They are located on top of the head and are separated from the frontal lobes by a deep infolding central sulcus (which runs roughly down the middles of the lateral surface of each hemisphere).
parietal lobes
the site for initial cortical processing and perception of somesthetic input as well as proprioceptive input.
somatosensory cortex
represents the relative distribution of cortical sensory processing for each area of the body. Different parts of the body are not equally represented, for ex. the face, tongue, hands and genitalia have a higher degree of sensory perception.
sensory homunculus
the area in the rear portion of the frontal lobe immediately in front of the central sulcus. It confers voluntary control over movement produced by skeletal muscles and the motor cortex on each side of the brain primarily controls muscles on the opposite side of the body.
primary motor cortex
- lies in the medial surface of each hemisphere anterior to the primary motor cortex.
- Plays a preparatory role in programming complex sequences of movement, for example, those requiring simultaneous use of both hands and feet.
- Stimulation of various regions of this motor area brings about complex patterns of movement.
supplementary motor area
the ability of the brain to change or be functionally remodelled in response to demands placed on it. New neural pathways can be formed in response to changes in experience. This pathway formation is mediated by alterations in dendritic shape, resulting from modifications in certain cytoskeletal elements.
plasticity
part of the cortex which governs speaking ability. It is located in the left frontal lobe in close association with the motor areas of the cortex that control muscles necessary for speech.
brocas area
another area of the cortex located on the left side at the juncture of the parietal, temporal and occipital lobes which is concerned with language comprehension. It plays a role in understanding written and spoken messages and is responsible for formulating coherent patterns of speech that are transferred via a bundle of fibres to Broca’s area.
wernickes area
This is the part of the brain that, “brainstorms.”
- Plans voluntary activity
- Involved in decision making (i.w. weight consequence and choosing between different options in various social or physical situations)
- Creativity
- Personality traits.
- Working memory (where the brain temporarily stores and actively manipulates information used in reasoning and planning).
prefrontal association cortex
hemisphere that excels in logical, analytical, sequential and verbal tasks like math, language forms and philosophy. Processes information in a fine detail, fragmentary way. Language areas are usually found on this side of the brain and is dominant for motor control
left hemisphere
hemisphere that excels in non language skills, especially spatial perception and artistic and musical talents. Processes information in a big picture, holistic way.
right hemisphere
a graphic record of the electrical activity within the cerebral cortex which is created by placing electrodes on the scalp. These brain waves are representations of the momentary collective postsynaptic potential activity (not action potentials).
electroencephalogram
One of the most common neurologic diseases accompanied by a distinctively abnormal EEG. Typically there is too little inhibitory compared with excitatory activity, as with compromised functioning of the inhibitory neurotransmitter GABA or prolonged action of the excitatory neurotransmitter glutamate.
epilepsy
indication of brain death
electrocerebral silence
- consist of several masses of grey matter located within the cerebral white matter.
- Inhibits muscle tone throughout the body (proper muscle tone is normally maintained by a balance of excitatory and inhibitory inputs to the neurons that innervate skeletal muscles)
- Selects and maintains purposeful motor activity while suppressing useless or unwanted patterns of movement
- Helps coordinate slow, sustained contractions (posture and body support)
- To accomplish these complex integrative roles, the basal nuclei receive and send out much information, as is indicated by the tremendous number of fibres linking them to other regions of the brain.
basal nuclei/ basal ganglia
a midline structure that forms the walls of the third ventricular cavity. It is located deep within the brain near the basal nuclei. It contains the thalamus and hypothalamus.
diancephalus
- the “relay station” and synaptic integrating centre for preliminary (primitive) processing of all sensory input on its way to the cortex.
- Screens out insignificant signals and directs the important sensory impulses to appropriate areas of the somatosensory cortex, and other regions of the brain.
- Important in the ability to direct attention to stimuli of interest.
thalamus
collection of specific nuclei and associated fibres that lie beneath (inferior) the thalamus. It is an integrating centre for homeostatic functions and is an important link between the autonomic nervous system and the endocrine system.
hypothalamus
the neural change responsible for retention or storage of knowledge. Generally, concepts, not verbatim information, are stored.
memory trace
are memories for the performance of particular actions. When needed, these memories guide procedures involved in both cognitive and motor skills. They are accessed and used without the need for conscious control or attention.
procedural memories
maintains balance and controls eye movements.
vestibulocerebellum
- enhances muscle tone and coordinates skilled, voluntary movement.
- Ensures the accurate timing of various muscle contractions to coordinate movements in multiple joints.
- Acts as “middle management,” comparing the “intentions” or “orders” of the higher centres with the “performance” of the muscles and then correcting any “errors” or deviations from the intended movement.
spinocerebellum
plays a role in planning and initiating voluntary activity by providing input to the cortical motor areas. This is also the cerebellar region that stores procedural memories
cerebrocerebellum
receptors for taste and smell
chemoreceptors
cluster of neuronal cell bodies in the brain stem
vestibular nuclei
____ detect sensory information from outside of the body
Exteroceptors
detect information regarding the body’s internal environment
interoreceptors
detect information about the body’s position and movement
proprioceptors
detect changes in body fluid concentrations
osmoreceptors
types of receptors that adapt rapidly, creating an impulse only if the stimulus changes
phasic and chemoreceptors
receptors that adapt slowly or not at all
Tonic receptors, particularly nociceptors and proprioceptors
when receptors convert energy into electrical signals it’s called…..
transduction
adequate stimulus
receptors in the eye are most sensitive to light, receptors in the ear to sound waves, etc
the predominant effect for stimulation of a receptor
inward flux of Na+, depolarizing the membrane
