Brain Pt 1. Flashcards
How many total neuroglia are found in the brain?
10-50 trillion.
How many neurons are there in the brain?
100 billion.
How many synapses does each neuron form with another neuron in the brain?
1000 for a total of 10^15 synapses.
What does the average human brain weigh?
3 lbs. .
*2% of body weight.
What composes the CNS along with the brain?
The spinal cord.
Number of cranial nerves?
12.
What embryonic structure did the brain develop from?
Neural tube.
What are the 3 early embryonic portions of the brain?
- Prosencephalon (Forebrain).
- Mesencephalon (Midbrain).
- Rhombencephalon (Hindbrain).
What is the function of the cranial meninges?
To surround and protect the brain.
*Continuous with spinal meninges.
What are the 3 cranial meninges?
- Dura mater.
- Arachnoid mater.
- Pia mater.
Where is the dura mater located?
Innermost meninge and in direct contact with the brain.
What are the 3 extensions of the dura mater?
- Falx cerebri.
- Falx cerebelli.
- Tentorium cerebelli.
What does the falx cerebri separate?
The two hemispheres of the cerebrum.
What does the falx cerebelli separate?
The two hemispheres of the cerebellum.
What does the tentorium cerebelli separate?
The cerebrum from the cerebellum.
What are the 4 major parts of the brain?
- Brain stem.
- Cerebellum.
- Cerebrum.
- Diencephalon.
What is the BBB made up of?
Specialized brain capillaries and astrocytes.
What is the function of the BBB?
Prevent the passage of potentially harmful substances and pathogens from the blood to the CSF and brain.
What type of connections maintains the BBB?
Tight junctions.
What passes through the BBB via active transport?
- Glucose.
- Some water soluble molecules.
What passes through the BBB via passive transport?
- Alcohol.
- Anesthetic agents.
- CO2.
- O2.
*Lipid soluble substances.
What cannot passes through the BBB?
- Proteins.
- Antibiotics.
What % of O2 and glucose does the brain consume?
20%.
What is the main, almost exclusive, energy source of the brain?
Glucose.
What happens to the brain when the body is hypoglycemic?
- Confusion.
- Dizziness.
- Loss of consciousness.
What happens to blood flow in the brain when an area is stimulated?
Blood flow to that area increases.
What happens when blood flow to the brain ceases, even momentarily?
Unconsciousness.
What two spaces does CSF circulate through?
- Subarachnoid space.
- Ventricles (CSF-filled cavities in brain).
How many ml of CSF are present in the body?
8-150 ml.
What does CSF contain?
- Anions.
- Cations.
- Glucose.
- Proteins.
- Urea.
How does CSF contribute to homeostasis?
- Chemical protection (accurate neuron signaling).
- Circulation and exchange of nutrients and waste products.
- Mechanical protection (shock-absorbing medium).
What are the choroid plexuses?
Networks of ependymal cell-lined capillaries in the walls of ventricles.
What is produced in the choroid plexuses?
Sites of production.
What are ependymal cells connected by?
Tight junctions.
What do ependymal cells form?
The blood-CSF barrier, allowing certain substances to enter the CSF.
What is meningitis?
Inflammation of the meninges from a bacterial or viral infection.
Which infectious agent for meningitis is more serious: the virus or the bacteria?
The bacteria.
What are the symptoms of meningitis?
- Confusion.
- Drowsiness.
- Fever.
- Headache.
- Lethargy.
- Stiff neck.
- Vomiting.
What two parts of the brain does the brain stem connect?
The spinal cord and diencephalon.
What are the 3 parts of the brain stem?
- Medulla oblongata.
- Midbrain.
- Pons.
What is the medulla oblongata composed of?
Nuclei.
What cranial nerves is the medulla oblongata associated with?
Cranial nerves VIII-XII
What are the nuclei that compose the medulla oblongata responsible for?
- Conscious proprioception.
- C/H/S/V.
- Touch.
- Vibration.
What 5 essential body functions does the medulla oblongata control?
- Arousal
- Blood vessel diameter.
- Breathing rhythm.
- Consciousness.
- Force and rate of heartbeat.
What is the medulla oblongata a relay station for?
Sensory input and motor output between other parts of the brain and spinal cord.
What is the pons composed of?
A bundle of axons.
What cranial nerves is the pons associated with?
Cranial nerves V-VIII.
What is the pons a relay station for?
- Messages from one side of the cerebellum to the other.
- Messages between the medulla and midbrain.
What essential body function does the pons help control?
Breathing.
What is the alternate name for the midbrain?
Mesencephalon.
What ventricles are located in the midbrain?
The 3rd and 4th, connected by a cerebral aqueduct.
What is the midbrain a relay station for?
- Motor outputs from the cerebral cortex to the pons.
- Sensory input from the medulla to the thalamus.
What are the functions of the midbrain?
- Coordinate eye movement in response to stimulus.
- Coordinate head and trunk movement in response to auditory stimulus.
What 2 brain structures contribute to midbrain function?
- Red nucleus.
- Substantia nigra.
What portion of brain mass is the cerebellum?
1/10th.
What is the cerebellum’s primary function?
To evaluate how well movement initiated by cerebrum motor areas is being carried out and correct for any deficits.
*Regulates balance and posture.
How does the cerebellum correct movement deficits?
- Corrects errors.
- Smooths the movements out.
- Coordinates complex sequences of skeletal muscle contractions.
What two structures is the cerebellum connected to?
- Red nucleus.
- Thalamus.
What are the reciprocal connections between the cerebellum and cerebral cortex related to?
- Cognition.
- Language processing.
What is ataxia?
Lack of muscle coordination or precision.
What are the 3 potential causes of ataxia?
- Alcohol consumption.
- Damage by disease or trauma.
- Disruption of muscle coordination.
