MCAT BIO CH. 8 PART 1 Flashcards
What is action potential?
Localized area of depolarization of the plasma membrane that travels along an axon
What is synaptic transmission?
Signal exiting the end of an axon at a synapse, transformed into a chemical signal with the release of neurotransmitter into the synaptic cleft
What is the soma?
Central cell body of the neuron
What does the soma contain?
The nucleus and biosynthetic activity takes place
What is the structure axons and dendrites?
Slender projections from the neuron; only one axon and multiple dendrites
What are bipolar neurons? What about multipolar neurons?
- Neurons with only one axon 2. Multipolar
What are synaptic knobs?
A button-like swelling on an axon where it has a synapse (connection) with another neuron
What is the synaptic cleft?
Small gap that chemical messengers travel across after being released from synaptic knob
What is the difference between a neuron and a nerve?
Neuron is a single cell; nerve is a large bundle of many different axons from different neurons
What are the two primary membrane proteins are required to establish the resting membrane potential?
- Na+/K+ ATPase
2. Leak K channels
How does the Na+/K+ ATPase work in regards to its ion pumping?
Pumps three Na out, two K in with hydrolysis of 1 ATP molecule
What type of transport s Na+/K+ ATPase?
Primary active transport
Are there only K+ leak channels?
No; very few sodium leak channels
Because the cells are negative on the inside and positive on the outside, they are described as _____?
Polarized
Action potential, based on the cell being always polarized, is a….?
Disturbance to the membrane potential, a wave of depolarization of the plasma membrane traveling along an axon
After depolarization, what returns the membrane potential normal?
Repolarization
Why is action potential considered electrochemical?
Because its no just movement of electrical impulse (electrons) but also ions
What are key proteins in the propagation of action potentials?
Voltage-gated sodium channels
What happens in response to a change in the membrane potential?
Ion channels open to allow sodium to flow down their gradient into the cell and depolarization
When are the voltage-gated sodium channels opened based on depolarization?
At threshold potential, approx -50 mV
When do the ion sodium channels become inactive? (To what voltage?) based on depolarization?
-35 mV
How does the neighboring neurons also go through depolarization?
Some sodium ions flow down the interior of the axon and depolarize the next section of the membrane
What happens in the beginning of repolarization?
- Na channel inactive
2. K+ channels open but more slowly and for longer
Does the K+ channels cause the mV to return to - 70mV?
No, it overshoots and reaches - 90 mV before the channels close
What is the axons wrapped in?
Insulating sheath called myelin
What are myelin sheaths created by?
Schwann cells
What is Schwann cell?
Type of glial cell; wrap layers of specialized membrane around axons
Where are Schwann cells found? What about the central nervous system?
Peripheral nervous system; myelination accomplished by oligodendrocytes
How does myelin affect the ions in the axons?
No ions can enter or exit the neuron, allowing it to travel and depolarize
What are gaps known in the myelin sheath termed?
Nodes of Ranvier
If there are no membrane depo. and no voltage-gated Na+ channels in regions wrapped in myelin, then where are they located?
Nodes of Ranvier
What is saltatory conduction?
Myelin sheath spending movement of action potential by forcing it to jump from node to node
What glial cells?
Specialized, non-neuronal cells that typically provide structural and metabolic support to neurons
Glial cells generate action potentials T/F
False: they only maintain a resting membrane potential
What are the five types of glial cells you should maybe remember?
- Schwann cells
- Oligodendrocytes
- Astrocytes
- Microglia
- Ependymal cells
Where are astrocytes located and what is their purpose?
CNS; Guide neuronal development and regulate synaptic communication (with neurotransmitters)
Where are microglia located and what is their purpose?
CNS; remove dead cells and debris
Where are ependymal cells located and what is their purpose?
CNS; produce and circulate cerebrospinal fluid
What is equilibrium potential?
No net movement of ions across the membrane
How are equilibrium potential measured (based on what it moves (hint)) ?
Equilibrium potential is specific for particular ion
How do the equilibrium potential of Na and K differ?
Na is + 50 mV while K+ is - 90 mV
What is the name of the equation that can predict the equilibrium potential for a specific ion?
Nersnt equation
What does Eion represent in the equilibrium potential equation?
The equilibrium potential for the ion
What does R represent in the equilibrium potential equation?
Is the universal gas constant
What does T represent in the equilibrium potential equation?
Temperature in Kelvin
What does z represent in the equilibrium potential equation?
valence of the ion
What does F represent in the equilibrium potential equation?
Faraday’s constant
What does [X] represent in the equilibrium potential equation?
concentration of the ion on each side of the plasma membrane
What does the valence of the electron help determine based on the Nersnt equation? What about the concentrations of the ion?
Chemical gradient; electrical gradient
What is the Nersnt equation?
Eion = RT/zF In ( [X]outside /[X]inside)
Since the resting membrane potential is close to the equilibrium potential of K+ (-90 mV), what does that indicate?
There are a large number of K+ leak channels in the membrane
If the cell is almost completely permeable to potassium, which is there a slightly positive mV compared to the equilibrium potential of K+ ?
Because there are a few Na+ leak channels allowing Na+ in
What is the refractory period?
Neuron unresponsive to membrane depolarization and unable to transmit another action potential for a shot period of time
What are the two phases of the refractory period?
- Absolute refractory period
2. Relative refractory period
What is the absolute refractory period?
Neuron will not fire another action potential no matter how strong a membrane depo. is induced
Why can’t the neuron not fire another action potential during absolute refractory period?
Sodium channels have been INACTIVATED (not closed)
What is the relative refractory period?
Neuron can be induced but depo. required is greater than normal because the membrane is hyperpolarized
When do electrical synapses occur?
When the cytoplasm of two cells are joined by gap junctions
When do chemical synapses occur?
End of axons meet their target cells; action potential converted into chemical signal
What happens when the action potential goes through the axon, where does it end up? (based on synaptic transmission)
Synaptic knob
What does the depolarization in the synaptic knob from the action potential causes? (based on synaptic transmission)
Depolarization of the presynaptic membrane opens voltage-gated calcium channels
What does the opening of voltage-gated calcium channels cause? (based on synaptic transmission)
Calcium influx into the presynaptic cell; exocytosis of neurotransmitter stored in secretory vesicles
What happens after the exocytosis of the neurotransmitters that were stored in secretory vesicles? (based on synaptic transmission)
Diffuse across the synaptic cleft
What is the synaptic cleft?
Small space between cells
After the diffusion of neurotransmitter across the s. cleft, what does it do? (based on synaptic transmission)
Binds to receptor proteins in the postsynaptic membrane
What are included in the receptors proteins in the postsynaptic membrane? (based on synaptic transmission)
Ligand-gated ion channels
What does the opening of the ligand-gated ion channels cause? (based on synaptic transmission)
Changes the membrane polarization
What happens to the neurotransmitter that had bonded to the receptor protein? (based on synaptic transmission)
Degraded or removed; terminates signal
What is an example of a chemical synapse commonly used?
Neuromuscular junction between neurons and skeletal muscle
What neurotransmitter is released from the neuromuscular junction?
Acetylcholine (AChE)
What happens in the neuromuscular junction when an action potential reaches such a synapse, based on neuromuscular junction?
Acetylcholine is released into the synaptic cleft
Where does the acetylcholine go when it is released into the synaptic cleft, based on neuromuscular junction?
Binds to the acetylcholine receptor on the surface of the postsynaptic cell membrane
What happens when the acetylcholine receptor is binded to by ACh, based on neuromuscular junction?
The receptor opens its associated sodium channel, allowing sodium to flow down a gradient into the cell
Allowing sodium to flow down a gradient into the postsynaptic cell, does what (based on neuromuscular junction)?
Depolarizes the postsynaptic cell membrane
What happens to the acetylcholine that had bonded to the receptor (based on neuromuscular junction)?
Degraded by the enzyme acetylcholinesterase (AChE)
What is an excitatory neurotransmitter?
Depolarizes the postsynaptic membrane
What is an inhibitory neurotransmitter?
Induce hyper polarization of the postsynaptic membrane
It is not the neurotransmitter that determines the effect on the postsynaptic cell, it is the ________?
Receptor
What is summation?
The decision of a postsynaptic neuron to whether fire an action potential is determined by both excitatory and inhibitory effects of the synapses
What is temporal summation?
Pre-synaptic neuron fires action potentials so rapidly that the EPSPs and IPSPs pile up on top of another
What does EPSPs stand for?
Excitatory postsynaptic potentials
Whatdoes IPSPs stand for?
Inhibitory postsynaptic potentials
What is spatial summation?
The EPSPs and IPSPs from all the synapses on the postsynaptic membrane are summed at a given moment in time
What is the sensory function of a nerve? What is it carried by?
Receiving information; PNS
What Is the integrative function of a nerve? What is it carried by?
Processing the information; CNS
What is the motor function of a nerve? What is it carried by?
Acting on it; PNS
What are two types of effectors?
Muscles and glands
What do motor neurons do?
Carry information from the nervous system toward organs which can act upon that information
What are efferent neurons? Where do they go?
Carry information away from the central nervous system and intervene effectors; carry to effectors
What are sensory neurons?
Carry information towards the central nervous systems
What are afferent neurons?
Sensory neurons that carry information towards the central nervous systems
How do reflexes occur?
Sensory neuron transmits an action potential to synapse with a motor neuron in the spinal cord, causing an action to occur
What is an example of a reflex?
Muscle stretch reflex
What happens during the muscle stretch reflex?
Sensory neuron detects stretching of a muscle, using sensory neuron to contract i
What is a monosynaptic reflex arc?
A reflex involving only two neurons and one synapse
What is an inhibitory interneuron?
A short neuron that forms an inhibitory synapse with a motor neuron
The interneuron is the simple example of the ____ role of the nervous system?
Integrative
What is reciprocal inhibition?
Concurrent relaxation and contraction, basically one and the other
If a reflex occurs without the involvement of the brain, how are we aware of the action?
- Sensory neuron also branches to form a synapse with a neuron leaning to the brain
- Other sensory information is received after the action is taken
What is included in the CNS?
Brain and spinal cord
What is included in the PNS?
All nerves and sensory structures outside of the brain and spinal cord
What are the two categories of the PNS?
- Somatic
2. Autonomic
What is the somatic division of the PNS?
Conscious sensation and deliberate, voluntary movement skeletal muscle is the somatic division
What is the autonomic division of the PNS?
Concerned with digestion, metabolism, circulation, perspiration and other involuntary processes
Where are the two categories of the autonomic division?
- Sympathetic
2. Parasympathetic
What is the sympathetic system?
Fight or flight
What is the parasympathetic system?
Rest and digest
What system does the adrenal medulla use and what hormone is released?
Sympathetic system; epinephrine (adrenaline)
What are the differences between the CNS and PNS, based on what are included?
CNS: brain and spinal cord
PNS: axons, dendrites, and cell bodies
What is white matter?
Myelinated axons
What is the white matter in the brain? Spinal cord? PNS?
Tract, tract or column, nerve
What is grey matter?
Unmyelinated axons
What is grey matter in the brain? In the spinal cord? In the PNS?
Nucleus and cortex, horn and ganglion (p. 289)
What are the three subdivisions of the brain?
- Hindbrain
- Forebrain
- Midbrain
What is the cerebrospinal fluid (CSF)?
A clear liquid that serves various functions
What does the hindbrain include?
Medulla, pon and cerebellum
Where is the medulla located?
Below the pons and connects brain to the spinal cord
What is the function of the medulla?
Relaying information between other areas of the brain and regulates vital autonomic functions
Where is the pons located?
Below the midbrain and above the medulla; connection b/n brain stem and cerebellum
What is the function of the pons?
Controls some autonomic functions and coordinates movement; plays a role in balance and antigravity posture
Where is the cerebellum located?
Behind the pons and below the cerebral hemisphere
What is coordinated in the cerebellum?
Integrating center where complex movement are coordinated
What is the function of the cerebellum?
Execution of movements
What is the purpose of the midbrain?
Relay for visual and auditory information and contains much more of the reticular activating system (RAS)
What is the reticular activating system responsible for?
Arousal and wakefulness
What is the brainstem?
Medulla, pons, and midbrain
What is important about the brainstem?
Contains important processing centers and relays information to or from the cerebellum doc cerebrum
What does the forebrain include?
Diencephalon and telencephalon
What are the divisions of the diencephalon?
Thalamus and hypothalamus
Where is the thalamus located?
Near the middle of the bran
What is the purpose of the thalamus?
Relays and processing centers for sensory information
What is the purpose of the hypothalamus?
Controlling emotions and autonomic function, hormone production and release
What is different with the telencephalon compared to the diendcelphalon?
Consists of two separate cerebral hemispheres
What is the corpus callous?
Thick bundle of axons connecting the cerebral hemispheres
What is the largest region of the human brain?
Cerebrum
What is the cerebral cortex?
Outer layer of gray matter
What part of the brain contains cerebral cortex?
Hemispheres of the cerebrum
What is the cerebral hemisphere responsible for?
Conscious thought processing and intellectual functions
What are the four categories of the cerebral hemispheres?
- Frontal lobe
- Parietal lobe
- Temporal lobe
- Occipital lobes
Function of the frontal lobe?
Initiate voluntary movement; involved in reasoning and problem solving
Function of the parietal lobes?
Involved in general sensations and gustation
Function of temporal lobe?
Auditory and olfactory sensation; short-term memory, language, emotion
Function of the occipital lobe?
Visual sensaiton
What is the function of the basal nuclei of the brain (basal ganglia)?
Voluntary motor control and learning related to habits
How do the basal ganglia and cerebellum work together?
- Basal nuclei: Inhibitory
2. Cerebellum: Excitatory
What is the function of the limbic system of the brain?
Emotion and memory
What is a homunculus?
Motor and sensory regions of the cortex are organized such that a particular small area of cortex controls a particular body part
The neurons entering and exiting the CNS are carried by what?
12 cranial nerves and 13 spinal nerves
What is the function of cranial nerves?
Convery sensory and motor information to and from the brainstem
What is the function of the spinal nerves?
Convey sensory and motor information to and from the spinal cord
What is an important example of the cranial nerve?
The vagus nerve
What structures does the vagus nerve effect?
The heart and GI
What is the function of the vagus nerve?
Decrease the heart rate and increase GI activity
What is the vagus nerve apart of based on systems?
The parasympathetic division of the autonomic nervous system
What is the physical structure of the vagus nerve?
Bundle of axons that end ing anglia not he surface of the heart, stomach and visceral organs
Where do the axons in the vagus nerve come from?
Preganglionic and come from cell bodies located in the CNS
What do the somatic motor neurons supply?
Skelete muscle cells
What neurotransmitter do somatic motor neurons use?
ACh
Where are the somatic motor neurons cell bodies located?
In the bran stem or the ventral portion of the spinal cord
What do all somatic sensory neurons have?
A long dendrite
Where does the long dendrite of the somatic sensory neuron extend from and towards?
Extends from sensory receptor towards the soma
Where is the soma located, based on somatic sensory neurons?
Outside the CNS in a dorsal root ganglion
What is the dorsal root ganglion?
Bunch of somatic and autonomic sensory neuron cell bodies located dorsal to the spinal cord
What are meninges?
Protective sheath of the brain and cord
Are the dorsal root ganglion located in meninges? Then what are they not included with?
No; CNS
What are the dorsal root ganglion protected by?
The vertebral column
In all somatic sensory neuron, the axon is located where?
Either synapses in the cord or stretches all the way up to the brain stem before its first synapse
The efferents of the sympathetic and parasympathetic systems consists of two neurons, what are they?
Preganglionic and postganglionic neuron
How is the preganglionic cell body, based on autonomic PNS anatomy?
Its cell body int he brainstem or spinal cord
What does the preganglionic cell body send, autonomic PNS anatomy?
An axon to an autonomic ganglion
Once the preganglionic cell body sends the axon to an autonomic ganglion, what does hat axon do, based on autonomic PNS anatomy?
Axon synapses with postganglionic neuron
The postganglionic neuron sends an axon to an _____? Based on autonomic PNS anatomy?
Effector (smooth muscle or gland)
All autonomic preganglionic neuron release __ as her neurotransmitter?
Acetylcholine
All parasympathetic postganglionic neurons release _____?
Acetylcholine
All sympathetic postganglionic neurons release _____?
Norepinephrine
Which part of the autonomic PNS anatomy have the cell bodies in the thoracic (chest) or lumbar (lower back) regions of the spinal cord?
All sympathetic preganglionic efferent neurons
What is the parasympathetic system known as and why?
Craniosacral system; all preganglionic neurons have cell bodies in the brainstem or lower portion of spinal cord
The sympathetic postganglionic cell sends a long axon to____? The parasympathetic postganglionc cell sends a long axon to _____?
The effector; a small ganglion which is close to the effector
Why is the adrenal gland named that way?
Ad-above and renal - kidney
Where are the adrenal glands located?
One above each kidney
What is the medulla? What about the cortex?
Inner portion of the adrenal; outer portion of the adrenal
What does the cortex secrete that is very important, based on the adrenal gland?
- Glucocorticoids (cortisol)
- Mineralcorticoids (Aldosterone)
- Sex hormones
What nervous system is the adrenal medulla apart of?
Sympathetic nervous system
What is the adrenal gland stimulated to release?
Epinephrine (or adrenaline)
What is an important effect of epinephrine?
Stimulation of the heart
Where do sensory receptors send the information for processing?
Central nervous system
What is sensation? What is perception?
The act of receiving information; the act of organizing, assimilating and interpreting
How does the brain know the difference between stimulation of visual receptors and olfactory receptors?
Brain distinguishes sensory stimuli based on which sensory neurons are signaling
What are exteroceptors?
Sensory receptors that detect stimuli from the outside world
What are interoceptors?
Sensory receptors that respond to internal stimuli
What do mechanoreceptors respond to?
Respond to mechanical disturbances
What are two important examples of a mechanoreceptor?
- Pacinian corpuscles
2. Auditory hair cell
What are pacinian corpuscles?
Pressure sensors located deep in the skin
What is the physical structure of Pacinian corpuscles?
Concentric layers of specialized membrane
What happens when the Pacinian corpuscles membranes are distorted by firm pressure on the skin?
The nerve ending becomes depolarized and the signal travels up the dendrite
Where is the auditory hair cell is found? How does it get stimulated?
In the cochlea of the inner ear; vibrations caused by sound waves
Where are vestibular hair cells located?
Within special organs called semicircular canals also found in the inner ear
What is the role of the vestibular hair cell?
Detect acceleration and position relative to gravity
What do chemoreceptors respond to?
Respond to particular chemicals
What are two types of chemoreceptors?
- Olfactory receptors
2. Gustatory receptors
What do olfactory receptors detect?
Detect airborne chemicals and allow us to smell things
What do gustatory receptors detect?
Taste buds
What are nocireceptors?
Pain receptors
What do nocireceptors respond to?
Stimulated by tissue injury
What does the nocireceptor consist of?
Generally consisting of a free nerve ending that detects chemical signs of tissue damage
What are the types of nocireceptors?
- Somatic
2. Autonomic
What do autonomic pain receptors lack?
Do not provide the conscious mind with clear pain information
What is referred pain?
Illusion of pain on the skin, when their nerves cross paths with somatic afferents from the skin
What do electromagnetic receptors respond to?
Stimulated by electromagnetic waves
What is an example of the electromagnetic receptors?
Rod and cone cells of the retina of the eye
What is an example of a photoreceptors in humans?
Rod and cone cells of the retina of the eye
What are the four properties of sensory receptors that must be communicated to the CNS?
- Modality
- Location
- Intensity
- Duration
What is stimulus modality?
The type of stimulus
How does the CNS determine the stimulus modality?
Type of receptor is firing
What is stimulus location?
The receptive field of the sensory receptor sending the signal
How is the stimulus intensity processed?
By the frequency of action potentials
What is the dynamic range based on stimulus intensity?
Range of intensities that can be detected by sensory receptors
How can the dynamic range of sensory receptors be expanded?
By range fractionation; multiple groups receptors with limited ranges to detect a wider range overall
What is stimulus duration?
Important for communicating changes stimulus and adapt immediately if a stimulus continues at the same level
What is adaptation based on sensory stimuli?
Decrease in firing frequency when the intensity of a stimulus remains constant
Why receptors do not adapt regardless of the constant stimuli?
Nocireceptors
What is proprioceptors? What is it also known as?
Refers to awareness of self; your kinesthetic sense
What are examples of a proprioceptor?
- Muscle spindle; also a mechanoreceptor
- Golgi tendon organs
- Joint capsule receptors
What is a muscle spindle mechanoreceptor?
Sensory organ specialized to detect muscle stretch
What is the purpose of the Golgi tendon organs?
Monitor tension in the tendons
What is the purpose of the joint capsule receptors?
Detect pressure, tension and movement in the joints
What does the prioreceptive component of the musculoskeletal system do?
The component of the somatic sensory system allows us to know the positions of our body parts
What are the five flavors taste buds can distinguish?
- Sweet 2. Salty 3. Bitter 4. Sour 5. Unami
What is the composition a taste bud?
Center is a taste pore, with taste hairs that detect food chemicals
Where is the information of taste transmitted?
Transmitted by cranial nerviest an area of the brain’s temporal lobe
Where are the olfactory receptors found?
Roof of he nasopharynx
How do the olfactory receptors detect chemicals?
Detect airborne chemicals that dissolve in the mucus covering the nasal membrane
What do the nerves do once olfactory receptors have been stimulated?
Olfactory nerves project directly to the olfactory bulbs of the brain
Where are the olfactory bulbs located?
The temporal lobe of the brain near the limbic system, an area important for memory and emotion
What are pheromones?
Chemical signals that cause a social response in members of the same species
What compromises the outer ear?
The auricle (pinna) and the external auditory canal
How is the middle ear divided from the outer ear?
The tympanic membrane (eardrum)
What does the middle ear consists of?
- Ossicles
- Malleus (hammer)
- Incus (anvil)
- Stapes (Stirrup)
What divides the middle and inner ear?
Th oval window which is under stapes
What are the structures of the inner ear?
- Semicicurlar canals
- Utricle
- Saccule
What part of the inner ear is important for balance?
- Semicicurlar canals
- Utricle
- Saccule
What is the round window?
A membrane covered hole in the cochlea near the oval window
What is the purpose of the round window?
Releases excess pressure
What is the Eustachian tube based on the air and what else it is known as?
Passageway from the back of the throat to the middle ear; auditory tube
What happens when the eardrums vibrate, what does it pass to?
Malleus receives vibrations and passed it to the incus and then the stapes then the oval window
What happens when vibration reaches the oval window?
Creates pressure waves in the perilymph and endolymph
What are the perilymph and endolymph?
Fluids in the cochlea
How are the sounds conveyed through the ear?
From air to bone and through liquid before being sensed
What does the pressure waves in the endolymph cause?
Vibration of the basilar membrane
What is the basilar membrane?
A thin membrane extending throughout the oiled length of the cochlea
What is the basilar membrane covered with?
Auditory receptor cells also known as hair cells
What do auditory receptor cells or hair cells have?
Cilia
What do the hair cells on the basilar membrane contact?
The tectorial membrane
What happens when the basilar membrane moves?
The hairs are dragged across the tectorial membrane and they bend
What happens when the hair (cilia) from the basilar membrane bend based on the basilar membrane moving?
Opens ion channels and neurotransmitters are released
What is the organ of Corti?
The basilar membrane, hair cells and tectorial membrane
When neurotransmitters are released based on the work of the basilar membrane, what does it stimulate and what does it lead to?
Dendrites from bipolar auditory afferent neurons are stimulated and sound vibrations are converted to nerve impulses
The outer ear and middle ear convey sound to the….? The organ of Corti in the ______ is the the primary site at which _______?
cochlea, cochlea, auditory stimuli are detected
How is pitch (frequency) distinguished?
By the regions of the basilar membrane vibrate which stimulates different auditory neurons
How does the size and structure of the basilar membrane differ in different regions?
Narrow, thick and sturdy near the oval window and gradually becomes wider, thin and floppy near the apex of the cochlea
Lower frequency / Longer wavelength sounds stimulate hair cells at the _______?
Apex of the cochlear duct, farthest away from the oval window
Higher frequency / Shorter wavelength sounds stimulate hair cells at the ________?
Base of the cochlea, near the oval window
How is the loudness of sounds distinguished?
By the amplitude of vibration
What is the purpose of the auditory cortex based on sound?
That is where sound is processed, located in the temporal lobe of the brain
What is the vestibular complex made up of?
Three semicircular canals, the utricle, the saccule and the ampullae
What do the vestibular complex have in each component?
Tubes filled with endolymph, cotton hair cells that detect motion
What is the function of the vestibular complex?
Rotational acceleration of the head
What are present in the vestibular complex based on neurons?
Innervated by afferent neurons which send balance information
What does the vestibular complex monitor?
Static equilibrium and linear acceleration, which contribute to sense of balance
