Flashcards in nuero Deck (114):
Central nervous system (CNS):
Consists of brain and spinal cord. At a very basic level they are responsible for integrating sensory input and coordinating motor output.
Peripheral nervous system (PNS)
: Functionally Divided into two parts
(1) Somatic (voluntary);
further divided into motor and sensory.
(2) Visceral (involuntary) or Autonomic (ANS).
ANS further subdivides into Sympathetic ("fight or flight") and Parasympathetic ("resting and digesting") divisions.
brain weighs approximately:
soft enough to
cut with a butter knife
the brain is a ___________ sized organ
outside the brain is
wrinkles (as part of the cerebral cortex)
folds on the brain allow for
maximum surface area
PNS Anatomically Divided into
12 pairs of cranial nerves and 31 pairs of spinal nerves.
The PNS provides:
innervation to the skin, joints and muscles that are under voluntary control.
Axons from "motor neurons" supply
muscles (cell bodies reside within the CNS)
sensory neurons bring information from
skin and joints to the CNS (cell bodies are found in dorsal root ganglia--outside the spinal cord).
ANS axons that innervated organs also
travel in peripheral nerves.
CN1 (CN I)
CN2 (CN II)
CNs 3,4,6 (CN III, IV, VI)
CN3 (III) also
constricts pupils and accommodates
(and moves eyes)
CN5 (CN V)
Feels front of face
CN7 (CN VII)
CN8 (CN VIII)
CN9 (CN IX)
and monitors blood pressure (via carotid bodies and sinuses in carotid arteries)
CN10 (CN X)
and is the most important parasympathetic nerve in body (i.e., for thoracic and abdominal organs).
CN11 (CN XI)
Turns head and lifts shoulders.
CN12 (CN XII)
Both divisions of the ANS (i.e., sympathetic and parasympathetic) possess
fibers (axons) that alter functions of, and monitor changes in, body organs (viscera ) and blood vessels.
All cell bodies for these axons/fibers are located outside the CNS in ganglia.
Cells of the Nervous System:
Neurons of Somatic PNS:
sensory nuerons convey
convey information from the skin and joints.
sensory nuerons carry signals to
cell bodies of sensory nuerons located:
within dorsal root of ganglion (a "ganglion" a collection of nerve cell bodies located outside the CNS).
Motor neurons convey
impulses away from the CNS to skeletal muscle fiber.
cell bodies of motor nuerons located
entire neuron and all fibers located within CNS. Integrate sensory input and motor output.
Almost All Neurons have Two Types of Fibers:
1)Dendrites2)Axons(Note: Know the structure of typical vertebrate neuron; see diagram in book).
-Chemicals that cross the synapse (i.e., gap between axon terminal and dendrite of follower neuron or effector cell).
Supporting Cells (Glial cells):-
Cells that structurally reinforce, protect, insulate and generally assist neurons.-Do not conduct impulses.-Outnumber neurons by 10 fold.
Glial Cells of the CNS:
control ionic environment, induce BBB, glial scar.
form myelin in CNS.
are phagocytic, originate outside CNS.
Ependymal cells -
secrete CSF (choroid plexus) and line brain ventricles.
Glial Cell of the PNS:
Schwann cells -
form the myelin sheaths around axons in PNS.
Satellite cells -
similar to astrocytes in function. ( control ionic environment, induce BBB, glial scar.)
Electrical insulation by concentric layers of membrane. Increases speed of impulse propagation.
Even though every living cell has a membrane potential,only
neurons and muscle cells/fibers can change theirs in response to stimuli.
membrane potential effect depends upon:
type of gated ion channel that opens.- Example: Na+ “wants” to diffuse into cell, down its conc. gradient.
At rest, inside relatively negative compared to outside.(Neg interior also results from presence of non-diffusible anions)
Membrane potential is due to
differential distributions of ions and charge.
Resting potential-of neuron =
-65 to -70mv.
outside/ inside cell (respectively) Na levels
150 mM (principal cation outside)
outside/ inside cell (respectively) K levels
5 mM (range = 4.5 – 5.5 mM)
100-150 mM (principal cation inside)
outside/ inside cell (respectively) Ca levels
outside/ inside cell (respectively) Cl levels
30 mM (125-150 mM) (principal anion outside)
13 mM (9-13 mM)
extra anion inside of cell
A-:65-100 mM (proteins anionic at pH 7.4;
occurs if K+ or Cl-channels open.
occurs if Na+or Ca2+channels open.
magnitude of change depends on strength of stimulus (
(-50 to -55 mV)
If graded potentials cause sufficient depolarization at axon hillock (initial segment) to reach threshold,an action potential is triggered.
rapid change in membrane potential caused by selective opening of voltage-gated ion channels.
-Action potentials are
“all-or-none”, i.e., they either happen or they do not happen...and when they happen, amplitudes are always the same.
, amplitudes are never affected by the strength of stimulus. The strength of a stimulus is represented by
frequency of action potentials. Stronger stimuli produce higher frequencies of action potentials.
Action Potential Stage 1. Resting state (“Resting Membrane Potential”):
All voltage-gated channels closed. For Neurons, equals approximately -65mv to -70mv).
Action Potential Stage 2. Threshold:
Membrane voltage (potential) at which “activation gates” of “voltage-gated Na+ channels” open (approximately -55 mv). Triggered, at proximal end of axon by summation of EPSPs, and spontaneously propagated down axon by entry of sodium through preceding voltage-gated Na+ channels.
Action Potential Stage 3. Depolarization phase:
Sodium floods into the axon. Interior of axon becomes so positive that membrane potential goes to +40mv.
Voltage-gated Na+ channels have 2 gates:
a)Activation gates whichopen at threshold, to start “depolarization phase.”b)Inactivation gates which close at beginning of “repolarization phase.”
Action Potential Stage 4. Repolarizing phase:
Inactivation gates of voltage-gated Na+ channels close, and voltage-gated K+ channels open, allowing K+ to flood out of axon.Note: Voltage-gated K+ channels have only one gate.
Action Potential Stage 5. Undershoot phase:
Membrane potential temporarily more negative than resting state. Since voltage-gated K+ channels are slow to close.
Action Potential Stage 6. Sodium/Potassium Pumps
re-establish the original ion distribution, so that a subsequent action potential can occur.
Graded Potentials (EPSPs and IPSPs) only happen at
graded potentials occur at
synapses on dendrites and neuronal cell bodies.
It is the most abundant neurotransmitter in the body, but is less than 5% of the neurotransmitters in the brain.
It is released by all motor neurons that activate our skeletal/voluntary muscles.
It is also released by all preganglionic autonomic neurons (parasympathetic and sympathetic), as well as post-ganglionic parasympathetic neurons.
It is the second most important neurotransmitter for learning and memory.
Excitatory in brain;
inhibitory on heart.
In brain, produces depolarization and
EPSPs by opening
ligand-gated sodium (Na+) channels.
It is the most abundant excitatory neurotransmitter in the brain, and accounts for approx. 35% of all neurotransmitters in the brain.
It the most important neurotransmitter for learning and memory.
It is always excitatory,
produces EPSPs and
depolarization by opening
ligand-gated sodium channels and ligand-gated calcium (Ca2+) channels.
It is the most abundant neurotransmitter in the brain, and accounts for approx. 50% of all neurotransmitters in the brain.
It is always inhibitory,
produces hyperpolarization and
IPSPs by opening
ligand-gated chloride (Cl-) and ligand-gated potassium (K+) channels.
It is mimicked by anesthesias, barbiturates, benzo's (e.g., valium) and alcohol.
Most important neurotransmitter for motivation.
All addictions cause dopamine release, either directly or indirectly.
An unrelated function is that dopamine is necessary for planning movement.
Parkinson's Disease caused by loss of dopamine producing neurons.
Puts our brains on high alert (sympathetic, "fight or flight").
Increases awareness, learning and memory.
Elevated by Adderall and other amphetamines.
Reduces stress, anxiety, depression, fear, and violent behavior.
Also, suppresses sex drive and eating.
Makes a person feel content and "warm and fuzzy."
Best antidepressants elevated serotonin (e.g., SSRIs).
Ecstasy ("E") causes massive release of serotonin, but predisposes to profound depression/suicide two-three days later.
Anterior/ventral and posterior/dorsal horns of spinal cord;
Ventral horns are gray matter of the spinal cord ...contain cell bodies of lower motor neurons.Dorsal horns are gray matter of the spinal cord ...contain cell bodies of sensory interneurons whose axons make dorsal columns.
Part of temporal lobe...Learning fear, plays role in anxiety and aggression.
Collection of neuronal cell bodies inside the CNS, not including cortical gray of cerebral and cerebellar cortices
Collective term for medulla oblongata, pons and midbrain.
Brain ventricles (4);
Lateral Ventricle largest of 4 ventricles in the brain. There are left and right lateral ventricles. Third and Fourth Ventricles are associated with the thalamus/hypothalamus and brain stem. All ventricles contain cerebrospinal fluid (CSF).
Cerebral Aqueduct ;
Connects 3rd and 4th ventricles and also contains CSF.
means little brain. Controls balance, equilibrium, and proprioception (receives stretch/rate of stretch information from muscles and tendons).
Divided into two cerebral hemispheres, each containing four major lobes (i.e., frontal, parietal, temporal and occipital). Also contains other major brain regions including the thalamus and hypothalamus.
Largest commissure in the brain (i.e., a commissure is white matter connection between both cerebral hemispheres); therefore, it connects the left and right cerebral hemispheres.
There are 12 pairs of cranial nerves. They are an extremely important part of the peripheral nervous system and connect directly to the brain . (Spinal nerves [see below] connect directly to the spinal cord.) Knowledge of cranial nerve connections and function essential in neurological diagnosis.
Dorsal, lateral ventral columns of spinal cord;
These are the white matter of the spinal cord. They contain bundles of myelinated axons that carry information up and down the spinal cord. For example, the dorsal columns convey sensory information (e.g., touch) up the spinal cord to the brain. Lateral columns convey motor information from the brain down the spinal cord, as well as pain and temperature info up the spinal cord to the brain.
Dorsal root ganglion;
Part of the peripheral nervous system, located adjacent spinal cord, one for each spinal nerve, contains cell bodies of vast majority of sensory neurons .
Frontal lobe(s) –
(1 of 4 major lobes of each cerebral hemisphere); contains precentral gyrus (for motor control) and prefrontal cortex (see below).
Collection of neuronal cell bodies located outside of the central nervous system.
Gray and white matter of brain and spinal cord;
Gray matter appears “gray” because contains high density of neuronal cell bodies, located in the CNS.White matter appears “white” because contains high density of myelinated axons , located in the CNS.
Ridges and bumps of the cerebrum.
Part of temporal lobe, for memory consolidation, spatial navigation, plays role in emotions. Damaged in Alzheimer’s.
Controls appetitive behaviors and much of endocrine system. Also plays major role in emotions.
Divides right and left cerebral hemispheres of the cerebrum.
Massa intermedia (intermediate mass of thalamus);
Seen in mid sagittal view of thalamus.
Most posterior part of the brain (hind brain). Contains many cranial nerve nuclei, tracts (i.e., collections of axons) from sensory and motor neurons, vestibular and auditory centers, cardiac center, and inspiratory center (breathing)
It does not include the thalamus or hypothalamus , as is often and mistakenly suggested in lay publications. Specifically located behind the hypothalamus and anterior to the pons. Contains the substantia nigra, some cranial nerve nuclei and .important motor and sensory tracts.
Motor neurons (upper and lower);
Upper motor neurons indirectly initiate movement; cell bodies located in precentral gyri and axons project to lower motor neurons.Lower motor neurons directly initiate movement; cell bodies located in ventral horn of spinal cord and axons project to skeletal muscle.
Occipital lobe(s) –
(1 of 4 major lobes of each cerebral hemisphere); Contains primary visual cortex.Note: Each main cerebral hemisphere lobe has primary regions and association areas which provide more complex information regarding each main function
Parietal lobe(s) –
(1 of 4 major lobes of each cerebral hemisphere); peripheral body sensation such as pain, touch, temperature, vibration, or itch. Contains postcentral gyrus (primary sensory cortex)
Pineal gland/body ;
“3rd eye”. Descartes’ seat of the soul. Makes melatonin for circadian rhythms . Will be discussed further with endocrine system.
Primary sensory cortex , located in parietal lobes.
Means bridge. Part of the brain stem. Contains sensory and motor tracts going up and down spinal cord, cranial nerve nuclei, and tracts interconnecting cerebellum with rest of the brain and spinal cord.
Primary motor cortex, located in the frontal lobes.
highest intellectual functions (executive functions ), decision making , self-control, morality.
Perceive sensations from skin (e.g., touch, pain, temperature) and convey to spinal .
Simple reflex arch (e.g., monosynaptic reflex);
Sensory neurons synapses with a lower motor neuron in the spinal cord. For example, stretch of patellar tendon is detected by a sensory neuron. The signal travels to the spinal cord where the sensory neuron synapses with a lower motor neuron that stimulates contraction of the quadriceps femoris
Shallow groves between gyri.
31 pairs, part of peripheral nervous system. Are mixed, i.e., they contain axons from motor and sensory neurons.
Superior & inferior colliculi(us);
together they comprise the corpora quadrigemina and roof of the midbrain. Involved in complex visual reflexes: Superior causes us to turn head when we see something in periphery. Inferior links auditory input to visual reflexes
Temporal lobe(s) –
(1 of 4 major lobes of each cerebral hemisphere); controls hearing, has primary auditory cortex (superior temporal gyrus), amygdala, and hippocampus.