4 - Brain Flashcards
The central driving component of the excitatory system is the _______
reticular substance of the pons and mesencephalon
a.k.a. the bulboreticular facilitory area
Signals from the reticular excitatory area pass to _______
the thalamus, and the thalamus sends signals on to the cerebral cortex
Are the following hormones excitatory or inhibitory?
Norepinephrine
Dopamine
Serotonin
Excitatory
Both
Inhibitory
Where are the neurohormones primarily located:
Norepinephrine
Serotonin
Dopamine
virtually every area of the brain
midline structures
basal ganglion regions
Identify which neurohormone is associated with the following structures:
Locus ceruleus
Substantia Nigra
Raphe Nuclei
Reticular Excitatory Area Giant Cells
Norepinephrine
Dopamine
Serotonin
Acetylcholine
What is the limbic system?
the entire neuronal circuitry that controls emotional behavior and motivational drives
What is the most obvious area that causes natural sleep?
Raphe Nuclei
What are two endogenous substances that induce sleep?
muramyl peptide
delta sleep-inducing peptide
what causes narcolepsy?
defects in orexin signalling
Which brain waves are associated with very deep sleep?
Delta
Generalized tonic-clonic (grand mal) seizures are characterized by:
sudden loss of consciousness in all areas of the brain
Seizure activity transmitted down the brain results in tonic and spasmodic (clonic) muscle activity
How long does a generalized seizure usually last?
3-4 minutes
What is the usual cause of generalized seizure?
Usually unknown
What are 5 epileptogenic factors?
Strong emotional stimuli
alkalosis from overbreathing
drugs
fever
loud noises/flashing lights
What are petit mal seizures?
Absence seizures
Most common in children
Usually disappear by age 30
Describe the function of the adrenal medulla
preganglionic sympathetic nerve fibers pass without synapsing from the spinal cord, through the sympathetic chains, and then through the splanchnic nerves all the way to the adrenal medulla
The adrenal medulla contains secretory cells that are actually embryologically nervous tissue, which is why they secrete epinephrine and norepinephrine as a hormone into the blood supply
What percentage of parasympathetic nerve fibers are within the vagus?
75%
In parasympathetic fibers, where are pre and post ganglionic fibers found?
The preganglionic fibers pass all the way to the organs they end on,
the postganglionic neurons are located in the walls of the organs they end on
Which fibers are cholinergic?
Which are adrenergic?
acetylcholine
adrenergic (short for adrenaline)
All preganglionic neurons are _______
cholinergic
Most of the postganglionic sympathetic neurons are _______
Most of the postganglionic parasympathetic neurons are ____
adrenergic
cholinergic
Acetylcholine is caused a _____ transmitter
Norepineprhine is called a _____ transmitter
parasympathetic
sympathetic
Where does acetylcholine synthesis occur?
terminal endings and varicosities
Where does norepinephrine synthesis occur?
begins in terminal nerve endings, completed inside the secretory vessicles
_______ is converted into norepinephrine in secretory vessicles
dopamine
In the adrenal medulla, norepinephrine is converted _______
about 80% is converted into epinephrine
When secreted into the blood, norepinephrine and epinephrine remain active for ________
10-30 seconds,
decline to extinction over a couple/several minutes via the liver
Acetylcholine activates two types of receptors:
muscarinic
nicotinic
Describe muscarinic receptors
use G proteins as their signaling mechanisms
found on all effector cells that are stimulated by postganglionic cholinergic neurons
Describe nicotinic receptors
ligand-gated ion channels
Found at the synapses between preganglionic and postganglionic neurons
Which lasts longer: direct sympathetic stimulation or hormonal sympathetic stimulation?
hormonal is 5-10x more long lasting
Complete cessation of blood flow to the brain causes unconsciousness after how long?
5 - 10 seconds
Which four arteries form the circle of willis?
Carotids (2)
Vertebrals (2)
What is the Virchow-Robin Space?
an extension of the subarachnoid space that penetrating vessels travel through
What is the average normal blood flow through the brain?
750-900ml/min
2% of bodyweight receives 15% of CO!
What effect on cerebral blood flow occurs when CO2/H levels are ELEVATED?
increased blood flow
How does CO2 cause vasodilation?
Converted to carbonic acid then bicarb and H
H causes direct vasodilation of the cerbreal vessels
Do other substances that increase the acidity of the brain have the same effect of CO2 increases?
Yes
Your brain will respond to H+ concentration, regardless of origin
A lactic acidosis will still cause increased respiration/cerebral blood flow
What is the role of astrocytes in cerebral blood flow?
couples neuronal activity with cerebral blood flow
Cerebral autoregulation is effective between _________ mmHg of arterial MAP
60-150
What causes seizures in pre-eclampsia?
cerebral blood flow autoregulation is impaited
leads to pressure-dependent increases in cerebral blood flow
Disrupts/damages vascular endothelium
causes brain edema and even seizures
Which uses more blood: gray or white matter?
Gray matter
about 4x as many capillaries are in gray matter
Brain capillaries are way less ______ than systemic capillaries
leaky
supported on all sides by glial feet, which provide structural support and prevent stretching/trauma
What is the average amount of CSF?
150ml
What “valve” controls flow of CSF and therefore CSF pressure?
The Arachnoid Villi
What is the neuromatrix theory?
Gate control ++
patterns of nerve impulses drawn from a multitude of factors
Stimuli may trigger the patterns but do no produce them
What is the role of serotonin and norepinephrine in pain modulation?
Contribute to pain inhibition in the medulla, but excite peripheral nerves
what part of the brain is responsible for temperature management?
hypothalamus
What happens in the brain when heat is needed?
TSH-RH released from hypothalamus
stimulates anterior pituitary to release TSH
acts on thyroid to stimulate release of thyroxine
thyroxine acts on adrenal medulla
adrenal medulla releases epinephrine
How is heat distributed?
the circulatory system
Term infants produce heat primarily through:
metabolism of brown fat
What causes a fever
temporary resetting of the hypothalamic thermostat in response to pyrogenic cytokines and exogenous pyrogens
Where do exogenous pyrogens and pyrogenic cytokines come from?
exogenous pyrogens are released by rupture of the microbe’s cell wall
pyrogenic cytokines are released by phagocytic cells as they destroy microbes within the host
What is the final common step for fever generation?
Production of PGE2
acts on warm centers in the hypothalamus to reset the temp goal
Why do people feel hot when a fever breaks?
The set point in the hypothalamus is returned to normal
the hypothalamus starts executing measures to reduce heat, including peripheral vasodilation, sweating, flushed skin
the person suddenly feels hot, throws off the covers and stretches out
Higher body temperatures decreases serum levels of _______,
which are needed for bacterial replication
iron, zinc, copper
RLS is more common in ______
women
individuals with iron deficiency
_______ is a cofactor in dopamine production
iron
What kind of virus causes pink eye?
viral conjunctivitis
Which three cranial nerves are involved in ocular movement?
oculomotor
trochlear
abducens
What is strabismus?
deviation of one eye from the other when a person is looking at an object
weak or hypertonic muscle in one of the eyes
What is myopia?
nearsighted, difficulty seeing objects that are far away
axis of the eyball is too long
what is hyperopia?
farsightedness, difficult seeing things that are near
axis of the eyeball is too short
What kind of lens corrects myopia
Hyperopia?
concave
convex
What is presbyscusis?
Loss of hearing in old age
Which cranial nerves are involved in olfaction?
Olfactory
Trigeminal
pupils are helpful in evaluating which part of the CNS?
brainstem
A large dose of _______ will fully dilate and fix pupils
anticholinergics
atropine and scopolamine
Overdosing on opioids will exhibit what pupillary changes?
Pinpoint pupils
What does vomiting without nausea indicate?
direct involvement of the central neural mechanism
Vomiting often accompanies CNS injuries that:
- involve the vestibular nuclei, esp with diplopia
- impinge directly on the fourth ventricle
- produce brainstem compression 2/2 increased ICP
What is the difference between brain death and cerebral death?
Irreversible cessation of function of the ENTIRE brain (including brainstem).
Cerebral death is the death of the cerebral hemispheres but not the brainstem and cerebellum
Damage/dysfunction in what area causes aphasia?
Left cerebral hemisphere (Broca’s and Wernicke’s Area)
Aphasia is usually associated with CVAs that involve with artery?
Middle cerebral artery (or one of its branches)
What is agnosia?
defect of pattern recognition
can’t tell what a safety pin is by feeling it, but can by seeing it or vice versa
Lots of varieties
What is the difference between expressive aphasia and dysarthria?
Expressive aphasia involves cognitive inability to form words
dysarthria is more to do with the physical inability to form words 2/2 nerve dysfunction. It’s not cognitive
What causes Alzheimer’s?
Acculumation of neuritic plaques containing a core of abnormally folded amyloid beta and tau proteins
intraneuronal tangles
degeneration of basal forebrain cholinergic neurons leads to loss of acetylcholine
What diseases cause seizures?
Anything that alters the neuronal environment
What is the tonic phase of a seizure?
muscle contraction with increased muscle tone
excitation of the subcortical, thalamic, and brainstem areas
What is the clonic phase of a seizure?
alternating contraction and relaxation of muscles
begins when inhibitory neurons in the cortex react to the cortical excitation
What qualifies as status epilepticus? (3)
- continuous tonic clonic seizures lasting more than 5 minutes
- rapidly recurring seizures before the person has fully regained consciousness
- a single seizure lasting more than 30 minutes
What is an optimal cerebral perfusion pressure?
70-90
What is the ideal MAP for a patient with altered cerebral flow?
90
What are the three types of cerebral edema?
vasogenic (most common, increased permeability)
cytotoxic (usually ischemia/hypoxia)
interstitial (noncommunicating hydrocephalus)
What is the difference between communicating and non-communicating hydrocephalus?
noncommunicating (obstructive): obstruction within the ventricular system
communicating (nonobstructive): impaired reabsorption of CSF
What is the most common cause of communicating hydrocephalus?
Subarachnoid hemorrhage
What are the hallmark pathologic features of Parkinson’s?
loss of dopaminergic pigmented neurons in the substantia nigra
degeneration of the basal ganglia with formation of Lewy bodies
What do “amyotrophic” and “lateral” refer to in ALS?
amyotrophic: refers to the progressive muscle wasting (lower motor neuron component)
Lateral: refers to the scarring of the corticospinal tract in the lateral column (the upper motor neuron component)
What are the two pyramidal tracts?
Corticospinal
Corticobulbar
Which two types of motor dysfunction comprise the extrapyramidal motor syndromes?
basal ganglia motor syndromes
cerebellar motor syndromes
