Final Exam Review: Neuro (12, 13, 14, 16) Flashcards
What are the two types of neural cells?
Nuerons and Neuroglia
Neurons are the functional unit of the NS; they send and receive signals
Nueroglia are the structural cells that support and protect the neurons
What are the two structural divisions of the nervous system?
Central Nervous System
Peripheral Nervous System
Explain what afferent and efferent mean
Afferent: the sensory information going from the periphery to the CNS
Efferent: the motor information going from the CNS to the PNS
“Efferent Exits”
Describe the somatic nervous system
The SNS
Controls skeletal muscle contractions
Can be voluntary or involuntary
Describe the autonomic nervous system
The ANS aka visceral motor system
Regulates smooth muscle, cardiac muscle, and glands
Involuntary
Divided into the Parasympathetic and Sympathetic systems
What are the three types of receptors?
Interoreceptors
Exteroceptors
Proprioceptors
Describe the structure of a typical neuron
A cell body contains the perikaryon (cytoplasm) and the nucleus
Many dendrites extend from one side of the cell body to reveive input
A single axon extends opposite the dendrites and branches at the end into telodendria
What are Nissl bodies?
The rough endoplasmic reticulum and free ribosomes within a neuron
These are the sites of neuronal protein synthesis
What portion of the neuron has the greates number of voltage gated sodium channels?
The axon hillock, which is located right where the cell body meets the axon.
What are neurotransmitters?
Chemical messengers that are released at the presynaptic membrane
They affect receptors located on the postsynaptic membrane
They are broken down by enzymes and reassembled in the synaptic terminal
What is the difference between a neurotransmitter and a hormone?
NTs diffuse across the synaptic cleft and act on postsynaptic cells
Hormones are chemicals released into the blood stream and travel to target tissues
**A single molecule can be a NT and a hormone depending on the circumstances, receptors…etc.
Can a single neuron release more than one type of neurotransmitter?
Yes. Many neurons are able to release multiple neurotransmitters.
Ex: neurons releasing dopamine and also a gas at the same time
What are the different types of synapses?
1) Synapses with another neuron
2) Synapses onto muscle “Neuromuscular Junctions”
3) Synapses onto gland cells “Neuroglandular Junctions”
What are the different types of neurons based on their structure?
Anaxonic: dendrites and axon are indistinguishable
Bipolar: cell body in middle, distinguishable dendrites and axon
Unipolar: dendrites and axon are continuous
Multipolar: cell body at end w/ dendrites, axon extending opposite
Describe interneurons
They are found between the sensory and motor neurons in the brain, spinal cord, and autonomic ganglia
They are responsible for distribution of sensory information and coordination of motor activity
Higher Functions: memory, planning, learning
What are the different types of neuroglia?
In the PNS: satellite cells and Schwann cells
In the CNS: Oligodendrocytes, Astrocytes, Microglia, and Ependymal cells
Where are ependymal cells found?
Lining the ventricles in the brain and the central canal of the spinal cord
Produce, circulate, and monitor CSF
Where are astrocytes found, and what is their function?
They are found in the blood brain barrier,
Tthey provide structural support, regulate ion/nutrient/gas concentrations, absorb and recycle NTs, and form scar tissue after neural injury
Is there thought to be communication between neurons and astrocytes?
Yes NTs can bind to astrocytes, thus providing cross communication between neurons and astrocytes
What is the main phagocytic cell in the CNS?
Microglial cells
They are the main phagocytic cell and antigen presenting cells in the CNS.
Provide immunological surveillance
What is the main function of oligodendrocytes?
They provide electrical insulation for axons called myelin, which is made up of fat
This allows for signals to travel node-node
How do schwann cells differ from oligodendrocytes?
Schwann cells are found in the PNS, rather than oligodendrocytes in the CNS.
An entire Schwann cell surrounds each segment of an axon, whereas oligodendrocytes have many extensions covering many different axon segments
What is Wallerian degeneration?
After an injury to a neural cell, the axon distal to the site of injury degenerates
How are Schwann cells related to injury response?
Following injury, Schwann cells are able to form paths for new growth and wrap the new axon in myelin.
Why can’t neurons regenerate in the CNS?
The regeneration machinery exists, but astrocytes block their function by releasing chemicals.
The neural growth is blocked, and scar tissue is produced in the place of damaged tissue
What are the steps in the repair of damaged PNS tissue?
1) Wallerian degeneration occurs in distal stump
2) Schwann cells form cord that grows into the cut and unites the stump; macrophages clean up
3) Axon sends buds into the network of Schwann cells and begins to grow across gap
4) Axon continues to grow and is enclosed by Schwann cells
Describe the ionic balances between the intracellular and extracellular fluid
ICF: High K+, Low Na+
ECF: High Na+, Low K+
What are the 3 main concepts of the transmembrane potential?
1) The ECF and ICF differ greatly in ionic composition
2) Cells have selectively permeable membranes
3) Membrane permeability varies by ion (Pk+ >Pna+)
What are the 5 main processes in neural activities?
1) Resting potential
2) Graded potential
3) Action potential
4) Synaptic activity
5) Information processing
Are K+ leak channels always open?
No. Some can close, but 99% of time they are open
What is the ratio of Na/K transfered by the Na/K exchange pump?
3Na are transfered out for every 2K in
What are the typical equilibrium potentials for K+ and Na+?
K+ = -90 mV
Na+ = +66 mV
What molecules are responsible for the electrical current and the resistance seen in neurons?
Electrical currents: Na and K channels allowing for propagation of action potential
Resistance: myelin sheaths
What is the potential energy involved with the membrane?
The electrochemical gradient
For a particular ion it is the sum of all of the chemical and electrical forces that act on an ion across a plasma membrane
What is the relationship between resting membrane potential and the potassium ion?
Because the plasma membrane is highly permeable to potassium ions, the resting potential of approximately -70mV is close to -90mV, which is the equilibrium potential of K+
How does the Na+ ion affect the resting membrane potential?
It only has a small effect on the normal resting potential because the membranes permeability to these ions is very low
What equation predicts the membrane potential using multiple ions?
The GHK Equation
What is the difference between passive and active channels?
- Passive channels = leak channels; almost always open, permeability changes with condition
- Active channels = gated channels; open and close in response to stimuli
*At resting potential, most gated channels are closed
What are the 3 classes of gated channels?
Chemically gated channels
Voltage gated channels
Mechanically gated channels
Why does the transmembrane potential exist across plasma membranes?
Because the cytosol and extracellular fluid have different chemical/ionic balance
The membrane is selectively permeable
What is repolarization?
When the stimulus is removed, transmembrane potential returns to normal
What is hyperpolarization?
Increasing the negativity of the resing potential due to the opening of K+ channels
Opposite of the effect of opening a sodium channel
What is depolarization?
Creating a more positive charge
Na+ moving into the cell
Explain spatial and temporal summation of stimuli
Spatial: channels in the same area, when stimulated, will create an electrical current and sum up
Temporal: rapid stimulation of one channel
Relative to the site of stimulation, where is the transmembrane potential most affected?
It is most affected at the site of stimulation
Are graded potentials associated with depolarization or hyperpolarization?
TRICK QUESTION
Both. They can do either, depending on which channels are opened in response to a stimulus.
Na+ channels open –> depolarization
K+ channels open –> hyperpolarization
What is the effect of graded potentials at the cell body and dendrite?
Specific cellular functions such as exocytosis of glandular segretions are triggered
Describe an action potential
a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a consistent trajectory
they link the graded potentials from the cell body with neurotransmitter release
Propagation occurs because of voltage gated channels that exist in the axon only
Describe the initial stimulus of an action potential
A graded depolarization of the axon hillock that is large enough to change the resting potential past the threshold level of voltage-gated sodium channels (~ -55 mV)
What is the all or none principle of action potentials?
If a stimulus exceeds a threshold amount, the actional potential has the same amplitude, no matter how large the stimulus is
The action potential is either triggered or it is not triggered
Explain the refractory period
The time period following the action potential when the membrane will not respond normally to additional stimuli.
Two types:
1) Absolute: sodium channels are open or inactivated; no action potential possible
2) Relative: Membrane potential almost normal; a very large stimulus can induce an action potential
How do the rates of Na and K channel opening differ during action potentials?
Na channels open quickly following depolarization, which causes the rising phase of the action potential
K+ channels open more slowly, which causes the peak and then the falling phase of the action potential
How does the extracellular potassium concentration alter the neuronal excitability?
Hyperkalemia: brings the membrane closer to the threshold lever, so a smaller stimulus will trigger an action potential (increased excitability)
Hypokalemia: Hyperpolarizes the membrane and makes the neuron less likely to fire an action potential in response to a normally sufficient stimulus (decreased excitability)
What are the two methods of propagating action potentials?
Continuous propagation: occurs in unmyelinated axons
Saltatory propagation: occurs in myelinated axons; preserves the signal and allows for faster signal transduction
What happens to neurons in the absence of ATP?
They stop functioning. ATP is required for maintaining the concentration gradients of Na+ and K+, which requires 1 ATP for each 2K+/3Na+ exchange
How are axon diameter and propagation speed related?
The are directly proportional: larger diameter axons have lower resistance and can therefore transmit the action potentials faster
What type of information is carried by large-diameter myelinated axons?
The most important information regarding vision, balance, and motor commands
What are the two types of synapses?
Electrical synapses: have direct physical contanct between pre and post-synaptic cells
Chemical synapses: the signal is transmitted across a gap (synaptic cleft) by chemical neurotransmitters
What are the two classes of neurotransmitter receptors?
Excitatory receptors: cause depolarization of postsynaptic membrane and promote the propagation of action potentials
Inhibitory receptors: cause hyperpolarization of postsynaptic membrane and supress action potentials
What is more important for dictating the effect of a neurotransmitter: the neurotransmitter itself, or its receptor?
The receptor determines the NT effect
Some NTs are excitatory in some tissues, but inhibitory in others due to different receptors
What role does calcium play in the synaptic cleft?
When an actional potential arrives at the synaptic knob, extracellular calcium enters the presynaptic cell triggering the exocytosis of ACh
What enzyme breaks down ACh in the synaptic cleft?
Acetylcholinesterase (AChE)
It breaks ACh into Choline and Acetate, thus preventing constant stimulation of postsynaptic receptors
The Choline is taken back up by the presynaptic cell mitochondria where it is turned back into ACh via CoA
What are the different ways that neurotransmitters work?
Direct effects on membrane channels (ex: Ach)
Indirect effects via G proteins (ex: Epinephrine)
Indirect effects via intracellular enzymes (ex: NO)
Where are norepinephrine and epinephrine released from?
The adrenal medulla
What are the characteristics of neuromodulators?
- Effects are long term, slow to appear, remain in CSF
- responses involve multiple steps with intermediary compounds
- Affect presynaptic membrane, postsynaptic membrane or both
- released alone or with a neurotransmitter
- not reabsorbed by presynaptic cell or broken down into a metabolite
Describe the process of presynaptic inhibition by an interneuron
An action potential from the interneuron stimulates GABA release which inactivates the presynaptic calcium channels
When an action potential arrives from the presynaptic axon, less calcium enters than normal, leading to less neurotransmitter being released, and a smaller effect observed on the postsynaptic membrane.
Describe the process of presynaptic facilitation
An action potential arrives from an interneuron which triggers serotonin release. The serotonin activates the presynaptic calcium channels.
When the action potential arrives from the presynaptic cell, more calcium enters than usual, which leads to more neurotransmitter being released and an increased effect on the postsynaptic membrane
What is the simplest form of information processing in the nervous system?
A change in transmembrane potential that determines whether or not action potentials are generated
What is the mechanism of action of Acetyl Choline and where is it found?
Direct effect through binding to chemically gated channels
ACh is found in the CNS throughout the brain and the spinal cord and also in the PNS neuromuscular junctions, preganglionic synapses of the ANS
What is the mechanism of action of norepinephrine and epinephrine and where are they found?
Indirect via G proteins and second messengers
E: found in the thalamus, hypothalamus, midbrain and spinal cord
NE: found in the cerebral cortex, hypothalamus, brain stem, cerebellum and spinal cord as well as in the PNS neuromuscular and neuroglandular junctions of the ANS
What are the major excitatory neurotransmitters?
Glutamate and Asparatate
What are the major inhibitory neurotransmitters?
GABA and Glycine
Describe the gross anatomy of the spinal cord
The spinal cord is about 18 inches long and 1/2 inch wide
It ends between the L1 and L2 vertebrae
There are 31 spinal cord segments based on the vertebrae that the spinal nerves originate from
How many of each type of vertebrae are there?
7 cervical
12 Thoracic
5 Lumbar
1 Sacral (fused)
What is different about the names of the cervical spinal nerves than the thoracic and lumbar nerves?
There are 8 cervical nerves and only 7 cervical vertebrae.
The cervical nerves leave above their corresponding vertebrae, except for C8, which is between C7 and T1.
After the cerivical region, the peripheral nerves always exit the spinal column below the vertebrae they share a name with
Which regions of the spinal cord have large gray matter regions?
The cervical and the lumbar regions have enlargements because of increased interneurons
Describe the distal end of the spinal cord
The conus medullaris begins at L1, which is where the spinal cord technically ends.
The cauda equina extends from L2 to S5
What is the subarachnoid space?
At the distal end of the spinal cord, this space contains CSF and spinal nerve roots. This is often the target for lumbar punctures
What is the epidural space, and what can be found within it?
The space located superficial to the dura matter.
It contains areolar, adipose, and blood vessels
What is found within the subarachnoid space?
Between the arachnoid matter and the pia matter
CSF, matrix collagen and elastin, arachnoid trabeculae
What type of information passes through the ventral roots of spinal nerves?
Motor information from the CNS to the muscles (somatic NS)
What are the three layers of the spinal meninges?
Dura matter: dense irregular CT that fuses with the periosteum at the foramen magnum
Arachnoid matter: covered by simple squamous epithelium
Pia matter: elastin and collagen fibers; contains the denticulate ligaments and the blood vessels for the spinal cord
Which side of the spinal cord has a more prominent fissure/sulcus?
The anterior median fissure is much more prominant than the posterior median sulcus
Which nuclei are found within the posterior gray horn of the spinal cord?
Somatic and visceral sensory nuclei with information coming from the dorsal root
Which nuclei are found in the lateral gray horn of the spinal cord?
The visceral motor nuclei
Which nuclei are found in the anterior gray horn of the spinal cord?
The somatic motor nuclei are found in the anterior gray horn of the spinal cord
How is the white matter of the spinal cord divided?
It is divided into regions or columns
Each column contains tracts or fasciculi that share functional and structural characteristics.
What are the 2 major dorsal columns fo the spinal cord?
The cuneate fasciculus and the gracile fasciculus are two sensory tracts that ascend through the posterior white matter in the spinal cord
Cuneate: discriminative touch and proprioception in the upper limb; located laterally to the gracile
Gracile: discriminative touch in the lower limb
Describe the path of the dorsal and ventral roots out of the spinal cord.
The dorsal root leaves posterior to the ventral root. After passing through the dorsal root ganglion, the dorsal root joins with the ventral root to form a spinal nerve
What are mixed nerves?
Nerves that contain both afferent (sensory) and efferent (motor) fibers
What is the difference between the white and gray ramus?
They carry visceral motor fibers to and from a nearby autonomic ganglion associated with the sympathetic NS
The white ramus is white because the preganglionic axons are myelinated
The gray ramus is gray because postganglionic fibers are unmyelinated. These fibers rejoin with the spinal nerve proximal to the white ramus and then travel to their target tissue
Compare the dorsal and ventral rami of the motor nerves
The dorsal ramus contains somatic and visceral motor fibers and innervates the back.
The ventral ramus is the larger branch and innervates the ventrolateral structures and the limbs
Describe the organization of spinal (peripheral) nerves?
Organized similar to skeletal muscles.
An Epineurium coverst the entire peripheral nerve.
The perineurium covers each fascicle within the nerve.
The endoneurium surrounds each individual myelinated axon
How does the path of visceral motor neurons out of the spinal cord differ from the path of somatic motor neurons?
Both travel out of the spine through the ventral root.
The visceral motor neurons travel through the white ramus to the ganglion. There they synapse with a postganglionic cell that returns the signal through the gray ramus to the spinal nerve
The somatic motor neurons travel through the ventral root and go directly to their destinations without synapsing within a ganglion.
Both, after rejoining divide into the ventral and dorsal rami
What are dermatomes?
Bilateral of the skin supplied mainly by a single spinal nerve
Which spinal nerves join together to form the phrenic nerve?
C3, C4, and C5 join together to form the phrenic nerve
The phrenic nerve passes down between the lung and the heart to reach the diaphragm
“C3, C4, C5 keep the diaphragm alive”
Which spinal nerves are involved in the brachial plexus?
C5 through T1
What are the different segments of the plexus?
Going from medial to lateral:
Roots, Trunks, Divisions, Cords, and Peripheral Nerves
How many trunks are there in the brachial plexus?
3: Superior, middle and inferior
What are the terminal branches of the brachial plexus?
Musculocutaneous n.
Axillary n.
Radial n.
Median n.
Ulnar n.
“UM….ARM”
Which side of the palm does the median nerve innervate?
The median nerve innervates the lateral side of the palm
Which spinal nerves contribute to the lumbar plexus?
T12 through L5
What is the major nerve emerging from the sacral plexus?
The sciatic nerve, which contains the anterior tibial and fibular nerves wrapped together in connective tissue
What are the nerves that innervate the foot region?
Saphenous: medial side of ankle/foot
Sural: lateral side of ankle/foot
Tibial: Bottom of foot and posterior heel region
Fibular: Top of foot
What are the different classifications of neuronal pools?
Divergence
Convergence
Serial processing
Parallel processing
Reverberation
What are neural reflexes?
Rapid automatic responses to specific stimuli that are the basic builiding blocks of neural function
The reflex arc occurs without input through the brain, only via a synapse within the spinal cord
They generally oppose the original stimulus (negative feedback)
Describe the path from stimulus to effector in a typical reflex arc
1) Sensory neurons are activated from the stimulus
2) They travel through the dorsal root ganglion and into the dorsal grey horn
3) Synapse with an interneuron that branches to a ventral root neuron and also passes info contrallaterally to the brain
4) The ventral root motor neuron is activated
5) The effector muscle contracts in response to stimulation by the motor neuron.
What is a monosynaptic reflex?
A reflex arc without an interneuron. The only synapse is between the sensory and motor neurons within the spinal cord.
What are the five general charactersistics of polysynaptic reflexes?
1) Involve pools of neurons
2) Are intersegmental in distribution
3) Involve reciprocal inhibition
4) Have reverberating circuits
5) Several reflexes cooperate
example: pain reflex when touching hot pan
What are ipsilateral reflex arcs?
They occur on the same side of the body as the stimulus
ex: stretch, tendon, and withdrawal reflexes
Opposite: contralateral reflex arc
What is the Babinski sign?
When the plantar reflex is wrong. Normally, by stimulating the bottom of the foot, the patient will respond with plantar flexion.
If they dorsiflex instead, this is indicative of WM damage to the spinal cord
What are the four functional classifications of the cranial nerve fibers?
1) Sensory nerves
2) Special sensory nerves (smell, hearing, balance)
3) Motor nerves
4) Mixed nerves
What are the cranial nerves, in order?
I) Olfactory nerve
II) Optic nerve
III) Oculomotor nerve
IV) Trochlear nerve
V) Trigeminal nerve
VI) Abducens nerve
VII) Facial nerve
VIII) Vestibulocochlear nerve
IX) Glossopharyngeal nerve
X) Vagus nerve
XI) Accessory nerve
XII) Hypoglossal nerve
What is the mneumonic for the cranial nerve names? and their types?
Oh, Oh, Oh, To Touch A Female’s Vagina Gives Vinay A Hard-on
Some Say Marry Money, But My Brother Says Big Boobs Matter Most
What is the function of the vestibulocochlear nerve (VIII)?
The vestibular branch is important for balance and equilibrium
The cochlear branch if important for hearing
What does the hypoglossal nerve (XII) do?
Tongue movements
What is the largest cranial nerve?
The trigeminal nerve
it has 3 major branches: the opthalmic, maxillary, and mandibular branches
What are the 5 branches of the facial nerve (VII)?
Temporal, zygomatic, buccal, mandibular, cervical
What are the main functions of the Glossopharyngeal nerve (IX)?
Innervates the posterior third of the tastebuds on the tongue
Also important for regulating blood pressure by carotid body pressure receptors
What is the longest cranial nerve?
The vagus nerve (X)
The only CN to leave the head
Extends down into the abdomen for visceral motor functioning of the digestive, respiratory and CV systems
What are the somatic cranial reflexes?
Corneal reflex: causes blinking upon contact with cornea (V –> VII)
Tympanic reflex: loud noise (VIII —>VII)
Auditory reflex: loud noise causis eye/head movements (VIII –> III,IV,VI,VII, X and cervical nerves)
Vestibulo-ocular reflexes: movement of eyes opposite rotation of head (VIII —> III,IV,VI)
Describe the size and weight of a typical adult human brain
Volume between 750cc and 2100 cc
Weight about 1.4 kg
How many primary brain vesicles are there?
3: Prosencephalon, Mesencephalon, Rhobencephalon
How many secondar brain vesicles are there?
5: Telencephalon, Diencephalon, Mesencephalon, Metencephalon, Myelencephalon
From what vesicle is the cerebrum formed?
The telencephalon develops into the cerebrum at birth
From what vesicle do the cerebellum and the pons develop from?
The metencephalon develops into the cerebellum and the pons
What are the major regions of the diencephalon?
The thalamus, hypothalamus, and epithalamus
What is the function of the thalamus?
Relay and processing center for sensory information
What is the function of the hypothalamus?
Contains centers for controlling emotion, autonomic functions, and hormone production
4 Fs: Fighting, Fleeing, Feeding and Fucking
What is the difference between a sulci and a fissure?
Sulci are shallow ridges in the cerebral surface, fissures are deeper more prominent ridges
What is the oldest part of the brain (evolutionarily)?
The medulla oblongota
Contains the autonomic centers for regulation of visceral function (CV, respiratory, and digestive systems)
How is the brain protected and supported?
Physical protection: cranial bones, cranial meninges, and cerebrospinal fluid
Biochemical isolation: blood brain barrier
What is the difference between the cranial dura matter and the peripheral dura matter?
The cranial dura matter is subdivided into two parts: osteo and meningal layers
What is the dorsum sellae?
“back of the saddle”
A double layer of pia mater that holds the pituitary gland in place
What are the major ventricles of the brain?
The lateral ventricles and the thrid and fourth ventricles
What segarates the left and right lateral ventricles?
The septum pellucidum
It runs as a sheet from the corpus callosum down to the fornix
What connects the third and fourth ventricles?
The aqueduct of the midbrain
What are arachnoid granulations?
Small protrusions of the arachnoid mater into the dura mater.
The allow CSF to exit the sub arachnoid space and enter the blood stream
What are the functions of the CSF?
Cusion the neural structures
Support the brain
Transport, nutrients, chemical messengers, and waste products
How is CSF formed?
CSF is produced by ependymal cells in the choroid plexus of the brain (50-70%).
Carbonic anhydrase and the sodium potassium pump are crucial for CSF formation
Describe the blood-csf barrier
Choroid epithelial cells joined together by tight junctions separate the capillaries from the CSF
These capillaries have fenestrations and intercellular gaps that allow for free movement of molecules across the endothelial cell
The CSF facing sides of the epithelial cells have microvilli that increase surface area for diffusion, facilitated diffusion and active transport into the CSF, and active transport of metabolites into the blood.
Where are the 4 breaks in the blood brain barrier?
1) Hypothalamus: for hormone secretion
2) Posterior lobe of pituitary gland: ADH and oxytocin
3) Pineal gland
4) Choroid plexus
What is the cerebral arterial circle?
Formerly called the “Circle of Willis”
A loop of arteries that supply blood to the brain.
Made up of: Anterior communicating, anterior cerebral, posterior communicating, and posterior cerebral arteries
Main feeds: R&L internal caratids, basilar artery
How is the fluid from the brain separated from the fluid in the blood circulation?
The blood-brain-barrier and the blood-CSF barrier separate the chemicals
Prevents chemicals from blood stream that would interfere with neurons from entering the CSF
Describe the medulla oblongata
The lower half of the brainstem
Contains the cardiac, respiratory, vomiting and vasomotor centers and deals with autonomic, involuntary functions
Where is the pons located?
above the medulla, below the midbrain, and anterior to the cerebellum
What does the pons do?
The pons conduct signals from the cerebrum down to the cerebellum and medulla(descending tracts), and ascending tracts that carry the sensory signals up into the thalamus
Where is the pneumotaxic center and what does it do?
It is located within the Pons
It regulates the change from inspiration to expiration
What is the mesencephalon?
The midbrain
Made up of the tectum and the cerebral peduncles
associated with vision, hearing, motor control, sleep/wake, arousal (alertness), and temperature regulation
Describe the cross sectional view of the midbrain
What is the major function of the reticular formation of the brainstem?
It filters the incoming stimuli to discriminate irrelevant stimuli
Very important for consciousness
What do the cerebaellar peduncles connect?
They connect the cerebellum to the brainstem
What is the function of the olivary nucleus?
Relays info to the cerebellum. Important for motor learning.
What are the two major things that the cardiovascular centers of the medulla oblongota regulate?
1 part regulates the rhythm of heart beating
1 part regulates vasoconstriction
What is the function of the nucleus gracilis and the nucleus cuneatus?
They relay somatic sensory information to the thalamus
What are the major regions contained in the midbrain?
The superior and inferior colliculi on the dorsal surface make up the “tectum”
The substantia nigra and the red nucleus are found within the ventral portion “tegmentum”
Describe the red nucleus
The red nucleus is a gray matter region found in the midbrain.
It controls subconcious motor movements such as swinging your arms when you walk.
What are the major functions of the cerebellum?
It plays an important role in motor control
Also: cognitive functions like attention and language; recording rapid stimuli
What are the lobes of the cerebellum?
The Anterior Lobe
The Posterior Lobe
The Flocculonodular Lobe
What are the 4 deep cerebellar nuclei?
Dentate
Emboliform
Globose
Fastigal
“Dont Eat Greasy Food’ lateral to medial
What are the major cells contained in cerebellar circuits?
Purkinje cells
Mossy fibers
Granule cells
Parallel fibers
Climbing fibers
What is the ultimate destination of the afferent pathways to the cerebellar cortex?
The purkinje cells
They receive input from the excitatory parallel fibers and the modulatory climbing fibers
Describe the structure of the cerebellar circuitry
Purkinje cells are highly branched cells that occupy planes within the cerebellum.
They receive input from parallel fibers, which travel perpendicular to the Purkinje plane after bifurcating from the granule cell axons.
Climbing fibers provide modulatory input to purkinje cells and granule cells
Describe the synapses within the cerebellum as inhibitory or excitatory.
The parallel fiber and climbing fibers, mossy fibers are excitatory
The purkinje cell synapses onto the deep cerebellar nuclei and is inhibitory
What is ataxia?
Damage to the cerebellum due to trauma or stroke. It disturbs muscle coordination.
Intoxication can also cause temporary impairment
What is the main component of the diencephalon?
The thalamus
Which sensory system does not have a corresponding thalamic nucleus?
The olfactory system
What embryological region is said to be the bridge between the endocrine and the nervous system?
The diencephalon is the bridge between the endocrine and the nervous system. The hypothalamus produces hormones (oxytocin and ADH) that are secreted into the blood stream by the pituitary gland.
What are the major things that the hypothalamus controls?
body temperature, hunger, thirst, fatigue, sleep, and circadian cycles
What regions are considered to be part of the limbic system?
hippocampus, amygdalae, anterior thalamic nuclei, septum, limbic cortex and fornix
What is the limbic system primarily responsible for?
Emotions and formation of memories
What links the conscious cortex with the autonomic brainstem?
The limbic system
What is the primary responsibility of the amygdaloid body?
It regulates fear responses
What is the fornix?
The white matter tracts connecting the hippocampus with the hypothalamus
What are the 4 lobes of the cerebrum?
Frontal
Temporal
Parietal
Occipital
What is the insula?
a portion of the cerebral cortex folded deep within the lateral sulcus, the fissure separating the temporal and the frontal lobes
What are the association areas of the brain, and in which lobes are each found?
The somatic sensory association area is in the parietal lobe
The visual association area is in the occipital lobe
The auditory association area is in the temporal lobe
Which Brodman’s areas are associated with the primary motor cortex and the somatosensory cortex?
Primary motor= BA4
Somatosensory = BA1
What are the different white matter fiber types of the cerebrum?
Association: connect different parts of same hemisphere
Commussural: connect the two hemishperes of the cerebrum
Projection: connect inferior to superior regions
Describe the basal nuclei (basal ganglia)
situated at the base of the forebrain
Components:caudate, putamen, globus pallidus, the substantia nigra, and the subthalamic nucleus
Movement planning, and feelings at a subconscious level
What are the differences between the left and right hemisphere of the cerebrum?
The left hemisphere controls: reading, writing and math, decision making, speech and language
The right hemisphere relates to: senses, recognition of faces, voice inflections
Where are the integrative centers for the ANS located?
in the hypothalamus
“the control center”
What are postganglionic fibers?
The axons of ganglionic neurons
Where are the nuclei for the preganglionic motor neurons located?
The are located in the primary motor cortex
Compare and contrast the functions of the Sympathetic and Parasympathetic divisions of the ANS
Sympathetic: Fight or Flight; increases alertness, metabolic rate and muscular abilities while stopping digestion
Parasympathetic: Rest and Digest; reduces metabolic rate and promotes digestion
Which ANS division innervates sweat glands?
Sympathetic NS
Describe the fiber lengths of the sympathetic nervous system
Preganglionic fibers are short
Postganglionic fibers are long
(with the exception of the adrenal medulla)
What are the 7 responses of increased sympathetic activity?
1) Heightened mental alertness
2) Increased metabolic rate
3) Reduced digestive and urinary functinos
4) Energy reserves activated
5) Increased respiratory rate
6) Increased heart rate and blood pressure
7) Sweat glands activated
Where do the parasympathetic preganglionic fibers originate from?
The brain stem and the sacral segments of the spinal cord (craniosacral)
Describe the fiber lengths of the parasympathetic nervous system
Preganglionic fibers are long
Postganglionic fibers are short
What are the 5 responses to increased parasympathetic activation?
1) Increased metabolic rate
2) Decreased heart rate and blood pressure
3) Increased secretion by salivary and digestive glands
4) Increased motility and blood flow in GI tract
5) Urination and defecation stimulation
What is the enteric nervous system?
A third division of the ANS that is only in the GI tract and does not require communication from the CNS
Where are the sympathetic preganglionic neurons originating from?
Between segments T1-L2 of the spinal cord
Where are the sympathetic ganglionic neurons found?
Near the vertebral column in the “sympathetic chain”
Also some are collateral ganglia (ENS function?)
Adrenal medullae
What are the inputs and outputs to sympathetic chain ganglia?
White rami are inputs
Gray rami are outputs
Do neurons traveling to collateral ganglia go through white rami, gray rami, or both?
They travel through the white rami, but NOT the gray rami. They go straight from the through the chain ganglion without synapsing and head to the collateral ganglion
Which sympathetic response route is the strongest: chain ganglia, collateral ganglia, or adrenal medulla?
The adrenal medulla response is the strongest because hormones are released straight into the bloodstream in the kidneys leading to a rapid global response
How is the signal amplified in the sympathetic chain ganglia?
One preganglionic fiber synapses on many ganglionic neurons
Are postganglionic fibers myelinated or unmyelinated in the sympathetic division?
Unmyelinated. Leave the ganglia through the gray rami
The regions corresponding with which cranial nerves are innervated by postganglionic parasympathetic fibers?
CN III, VII, IX, and X
What are splanchnic nerves?
They are nerves formed by preganglionic fibers that innervate collateral ganglia in the dorsal wall of the abdominal cavity (just in front of retroperitoneal cavity)
Many spinal nerves join together to form the splanchnic nerves.
Where do the preganglionic fibers from the seven inferior thoracicc segments end?
They end at the celiac ganglion or the superior mesenteric ganglion (Collateral Ganglia)
What organs do the postganglionic fibers of the celiac ganglion innervate?
Stomach, liver, gallbladder, pancreas, spleen
What do the mesenteric ganglion postganglionic fibers innervate?
Superior mesenteric: The small intestine and proximal 2/3 of the large intestine
Inferior mesenteric: Large intestine, kidney, bladder, sex organs
What do the preganglionic fibers synapse on in the adrenal medulla?
Neuroendicrine cells that secrete hormones into the bloodstream in a matter of seconds
What are the neurotransmitters associated with the adrenal medulla?
Epinephrine (adrenaline)
Norepinephrine
What neurotransmitter is typically released at sympathetic synapses?
Acetyl choline (ACh)
What are sympathetic varicosities?
Swollen areas at the end of unmyelinated postganglionic fibers.
Filled with vesicles containing neurotransmitters
These enlargements form the synaptic contact with the target tissue
What is the difference between cholinergic and andrenergic neurons?
Cholinergic neurons release acetyl choline and andrenergic neurons release norepinephrine
How does the release of NE and E lead to sympathetic stimulation?
Via the action of G proteins with Alpha receptors or beta receptors that activate enzymes on the inside of cell membranes
Where are cholinergic sympathetic terminals found?
The sympathetic synapses to sweat glands of the skin and blood vessels of the muscles and brain are cholinergic
Stimulates sweat secretion and dilation of blood vessels
What is the major effect of nitric oxide (NO) as a neurotransmitter?
It produces vasodilation, increased blood flow
Where are parasympathetic terminal ganglia usually found?
Near the target organ
Long preganglionic and short postganglionic fibers
Which nerve provides ~75% of all parasympathetic outflow?
The Vagus Nerve (CN IX)
Does the parasympathetic NS have a global effect?
No, just local effects.
A global effect would set the heart rate to 0
What are the major effects of the parasympathetic NS?
1) Constriction of pupils
2) Secretion by digestive glands
3) Secretion of hormones that promote absorption and utilization of nutrients by peripheral cells
4) Increase smooth muscle activity
5) Stimulation and coordination of defacation
6) Contraction of urinary bladder during urination
7) Constriction of respiratory passageways
8) Reduction in HR and in force of contraction
What is the neurotransmitter for all parasympathetic neuromuscular and neuroglandular junctions?
Acetylcholine
What is the difference between a drug and a toxin?
A drug produces a controlled response, whereas a toxin produces an exaggerated uncontrolled response
What are the signs and symptoms of a muscarinic toxin?
DUMBELLS: diarrhea, urination, miosis, bradycardia, emesis (vomitting), lacrimation, lethargy, salivation
blind as a bat, mad as a hatter, red as a beet, hot as a hare, dry as a bone, the bowel and bladder lose their tone, and the heart runs alone
Drugs: antihistamines, anticholinergics, antiparkinsonians, antidepressants
Describe the dual innervation by sympathetic and parasympathetic onto major organs
Most vital organs receive instructions from both S and PS divisions, which provide opposing effects, allow for fine tuning and regulation
Describe autonomic plexuses
Nerve networks in the thoracic and abdominopelvic cavities
Contain sympathetic postganglionic and parasympathetic preganglionic fibers
What is autonomic tone, and why is it important?
The nerves maintain a resting level of spontaneous activity so that they can increase OR decrease in response to stimuli
What is the difference between a short reflex arc and a long reflex arc?
Short reflex arcs are found in the GI tract and go directly from sensory neurons to autonomic ganglia without passing through the spinal cord
Long reflex arcs pass through the spinal cord before passing back out through the autonomic ganglia
Where are complex reflexes such as salivation and swallowing controlled?
In the medulla oblongata, regulated by the hypothalamus
What are the three characteristics of higher order functions?
1) require the cerebral cortex
2) involve conscious and unconscious information processing
3) Are not part of programmed “wiring” of the brain (they are reprogrammable)
What are the two types of memory?
Declarative (fact memories): specific bits of information
Procedural (skill memories): learned motor behaviors
What brain regions are involved with procedural memories?
Basal nuclei, cerebral cortex, and cerebellum
What is memory consilidation?
Conversion from short-term to long-term memory
What are the two types of long-term memory?
Secondary memories: fade and require effort to recall
Tertiary memories: permanent imprints (ex: middle name)
What are the brain regions involved with memory consolidation and access?
The amygdaloid body and hippocampus, nucleus basalis, and cerebral cortex
What is anterograde amnesia? Damage to what region can cause this?
The inability to convert short-term memories to new long-term memories
Damage to amygadaloid body and hippocampus
What is the cellular mechanism for memory formation and storage?
Increased neurotransmitter (Glutamate) is released and binds to NMDA receptors
This leads to facilitation at the synapses: more glutamate released next time, more receptors present
Leads to additional synaptic connections and synaptic growth
Why is procedural memory harder to forget completely?
It involves more complex circuits involving more senses
Describe an NMDA receptor
Chemically gated calcium channels that are linked to consolidation
Activated by glutamate
Blocking these receptors prevents long term memory formation
During REM, are you more or less aware of outside stimuli than in deep sleep?
Less aware because of dreaming
Why does muscle tone decrease markedly during REM sleep?
So that sleeping people don’t act out their dreams, decoupling of peripheral motor neurons and CNS
What is the relationship between the RAS activity and the cerebral cortex?
When the RAS is inactive, so is the cerebral cortex
This is why a stroke in the RAS causes a coma
What happens to patients with Huntington’s disease?
The ACh-secreting and GABA secreting neurons in the basal nuclei are destroyed
This leads to difficulty controlling movements and gradual decline of intellectual ability
What is the effect of LSD?
A powerful hallucinogenic drug that activates serotonin receptors in the brain stem, hypothalamus, and lymbic system
What happens when serotonin is inhibited?
Compounds that inhibit or block serotonin cause severe depression and anxiety
SSRIs
