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bi 232 > Exam 1 > Flashcards

Exam 1 Flashcards

0
Q

How heavy is the brain?

A

The size of brains varies considerably around a mean of 1.6 kg (3.5 lbs) in men.

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1
Q

Describe the primary functions of the brain.

A

The brain is the “supercomputer” of the body. It is the primary integration center (processes sensory input and motor output) and is responsible for higher order functions such as memory, planning, personality, emotions, and language.

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2
Q

What percentage of neurons are found in the brain?

A

97% in brain

2% in spinal cord; 1% in PNS

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3
Q

Describe the primary regions of the brain.

A

Cerebrum

  • Makes up 83% of the brain
  • Composed of 2 large lateral hemispheres

Cerebellum
-Contains half of the neurons in the brain

Brain Stem, composed of:

  • Diencephalon (thalamus and hypothalamus)
  • Midbrain
  • Pons
  • Medulla oblongata
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4
Q

What is the central cavity?

A

The central cavity consists of 4 spaces known as ventricles that contain CSF. It is continuous with the central canal of the spinal cord. Grey matter completely surrounds the central cavity in the brain stem but doesn’t completely surround the ventricles.

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5
Q

What type of matter makes up the cerebral and cerebellar cortex (cortex=bark or rind)?

A

Grey matter makes up the cerebral cortex and cerebellar cortex.

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6
Q

What makes up white matter? What makes up grey matter?

A

White matter is made up of myelinated axons; grey matter is made up of neuron cell bodies and dendrites.

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7
Q

What are nuclei?

A

Nuclei are collections of neuron cell bodies surrounded by white matter. Examples include basal nuclei of cerebrum and nuclei of brain stem.

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8
Q

What are the three layers of the cranial meninges from superficial to deep?

A

Dura Mater
-Periosteal layer: pressed against cranial bones; only layer not continuous with spinal meninges
-Meningeal layer: forms falx cerebri, tentorium cerebelli and falx cerebelli
Arachnoid Mater
Pia Mater

Note: No epidural space exists in the cranium.

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9
Q

Meningitis: Who is at risk? What is the cause? What are the s/sx? How is meningitis diagnosed?

A

Meningitis primarily affects young children ages 3 months-2 years.

Can be bacterial (Streptococcus, Escherichia, Listeria and Neisseria), viral or fungal. Often enters through nose or throat.

Infx can spread from arachnoid and pia mater to nervous tissue.

S/Sx: Drowsiness, intense headache, stiff neck, vomiting, rash (in some), photophobia, phonophobia, and high fever.

Lumbar puncture used to collect CSF for diagnosis.

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10
Q

Describe the location of the 4 ventricles of the central cavity and the connections between them.

A

One large lateral ventricle is located in each cerebral hemisphere. These two lateral ventricles are separated medially by the septum pellucidum. They connect to the third ventricle via the interventricular foramina.

The third ventricle is located deep inside the diencephalon. It connects to the fourth ventricle via the the cerebral aquaduct, which runs through the midbrain.

The fourth ventricle is located between the posterior pons and anterior cerebellum and is continuous with the central canal.

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11
Q

What is a choroid plexus? Where is it located? What is its function?

A

A choroid plexus is a cluster of pia mater (containing capillaries) and ependymal cells. One choroid plexus is found in each ventricle. The choroid plexus produces CSF. (CSF is also produced by ependymal cells that line the central cavity and central canal.)

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12
Q

How much CSF is present in the body (central cavity, central canal and arachnoid space)? How much CSF is produced daily?

A

500mL of CSF is produced daily; however, only 100-160mL is present in the body at any given time. The CSF is drained at the same rate it is produced.

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13
Q

Where is the CSF produced? Where is it drained?

A

CSF is produced in the choroid plexuses of the ventricles and from the ependymal cells that line the central cavity and central canal.

The CSF is drained through the arachnoid villi into the superior sagittal sinus (a space formed between the two layers of the cranial dura mater).

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14
Q

Compare the composition of CSF to that of blood plasma.

A

CSF is very similar in composition to blood plasma; however, it is slightly altered by the ependymal cells to contain more sodium and less potassium and protein. The higher sodium levels facilitate the conductivity of nervous tissue.

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15
Q

What are the functions of CSF?

A

1) Floats the brain, reducing the weight of the brain from 3 lbs to 50g
2) Absorbs shock when the skulls is hit
3) Transport of gases, wastes, and nutrients
4) Maintains appropriate environment for action potentials

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16
Q

What two factors contribute to the circulation of CSF?

A

1) Cranial blood pressure pulses cause CSF pressure pulses that cause CSF to circulate.
2) Cilia of ependymal cells also cause CSF to circulate.

17
Q

How does CSF move from the central cavity to the subarachnoid space?

A

The CSF flows from the central cavity to the subarachnoid space via two lateral apertures and one median aperture in the walls of the fourth ventricle.

18
Q

Describe the condition hydrocephalus.

A

Hydrocephalus occurs when a tube of the central canal is blocked by a tumor, inflammation, injury, hemorrhage, or developmental malformation. Because of the blockage, CSF cannot drain and pressure inside the central cavity increases, leading to compression of brain tissue which can kill neurons. Because of the malleability of the infant skull, an infant’s entire head can enlarge.

Hydrocephalus is treated by inserting a tube into the central cavity and draining CSF into a vein in the neck, abdomen or subarachnoid space.

19
Q

Which vessels deliver blood to the brain?

A

The internal carotid arteries deliver blood to the brain.

20
Q

Which vessels return blood to venous circulation, removing it from the head?

A

The blood returns to venous circulation and leaves the head via the internal jugular veins.

21
Q

What percentages of the body’s total blood, oxygen and glucose are used by the brain?

A

15% of the body’s blood supply is used by the brain

20% of the body’s O2 and glucose is used by the brain

22
Q

How long can neurons survive during oxygen deprivation? Why?

A

Neuronal death begins within 4 minutes from the onset of oxygen deprivation. This is because it takes 4 minutes for venous reserve (O2 not offloaded from hgb during normal circumstances) to be depleted.

23
Q

Describe the positive feedback loop that occurs when neuronal death begins to occur.

A

When a neuron dies, its lysosomes’ contents are released the extracellular space, including glutamate which causes neighboring cells to die and release glutamate from their lysosomes, and the process goes on and on.

24
Q

What is the purpose of the circle of Willis? What is another name for this structure?

A

The circle of Willis provides redundant blood flow to the brain so that the brain still receives blood if one side of the circles is obstructed.

The circle of Willis is also known as the cerebral arterial circle.

25
Q

Describe the two barriers make up the brain barrier system?

A

Capillaries in brain tissue have endothelium with tight junctions that require materials to pass through (not around) the cells. This is known as the blood-brain barrier.

Tight junctions between ependymal cells of the the choroid plexuses form the blood CSF barrier.

Collectively, these two barriers are known as the brain barrier system (BBS).

26
Q

What is the purpose of the brain barrier system (BBS)? What is a disadvantageous side effect of the BBS?

A

The purpose of the brain barrier system is to protect the brain by regulating what passes from the blood into the fluids and nervous tissue of the the brain. (Keeping out potentially dangerous substances.)

This can sometimes make it challenging to treat infections and cancers in the brain because antibiotics and cancer meds have a hard time crossing the BBS. It is important to know what drugs can cross the BBS when prescribing to treat brain disorders.

27
Q

List some substances that can freely pass the BBS.

A 
glucose 
water
oxygen 
carbon dioxide
alcohol
nicotine
caffeine
anesthetics
28
Q

List the primary structures of the CNS is order of complexity.

A

spinal cord
brain stem
cerebellum
cerebrum

29
Q

What structures are located on the anterior aspect of the medulla oblongata? What physiologically significant point is present here?

A

The pyramids of the medulla are located on the anterior aspect of the medulla oblongata. They contain descending fibers from the motor cortex of the cerebrum (corticospinal tracts). The crossover point for the motor fibers occurs here and is known as the decussation of the pyramids. This is the reason for contralateral function.

30
Q

Describe the flow of motor and sensory information in the medulla oblongata.

A

Motor information descends thru the pyramids of the medulla (anterior portion). Crossover of the fibers occurs at the decussation of the pyramids, allowing for contralateral function.

Sensory information ascends thru the posterior portion of the medula via the gracile fasciculi (medial) and cuneate fasciculi (lateral).

31
Q

What are some of the functions of the medulla oblongata?

A
  • Life support system that contains important ANS nuclei that regulate HR, blood vessel diameter, rate and depth of breathing.
  • Sensory info regarding BP and respiration
  • Sensations from tongue and pharynx
  • Gagging, swallowing and salivation
  • GI secretion, motility and sensations of discomfort
  • Tongue, head, neck and shoulder movements
32
Q

Which cranial nerve nuclei are found in the medulla oblongata?

A

glossopharyngeal (IX), vagus (X), accessory (XI), and hypoglossal (XII)

33
Q

Describe the 3 types of cerebellar peduncles.

A

The inferior cerebellar peduncles connect the medulla and the cerebrum.
The middle cerebellar peduncles are transverse tracts that connect the cerebellum to the pons.
The superior cerebellar peduncles connect the midbrain and the cerebrum.

34
Q

Where are the respiratory nuclei found?

A

The respiratory nuclei are found in the pons, which works with the medulla oblongata to regulate respiration.

35
Q

List 7 functions of the pons.

A

(1) Lateral eye movement
(2) Receiving somatosensory info from the head and face
(3) Chewing
(4) Gustatory information
(5) Secretion of tears and saliva
(6) Control of muscles of facial expression
(7) Hearing and equilibrium

36
Q

What are the cerebral peduncles? Where are they located?

A

The cerebral peduncles are descending motor tracts that go from the primary motor cortex, through the pons, to the cerebellum. They are located on the anterior portion of the midbrain.

37
Q

What structures make up the corpora quadrigemina? What is the function of each? Where are they located?

A

The corpora quadrigemina is located on the posterior aspect of the midbrain. It is made up of one pair of superior colliculi and one pair of inferior colliculi.

The superior colliculi are visual reflex centers that coordinate head and eye movements when we track an object. They allow us to blink and turn our head in response to movement.

The inferior colliculi are auditory reflex centers that relay auditory information to the thalamus. They are important for the startle reflex in response to loud noise.

38
Q

Nuclei for which CN are found in the midbrain?

A

oculomotor (III) and trochlear (IV) nerves

39
Q

Describe the location, composition and purpose of the red nucleus.

A

The red nucleus is located in the midbrain and contains lots of blood vessels (and Fe). Fibers leaving the red nucleus travel to the cerebellum and help to smooth out fine motor movements.

40
Q

Describe the location, composition and function of the substantia nigra.

A

The substantia nigra is located in the midbrain and is dark because it contains melanin. It functions to produce the precursor to dopamine and inhibit the thalamus and basal nuclei.

Degeneration of these neurons has implications in Parkinson disease.

41
Q

What is the name of the hollow structure that runs thru the midbrain?

A

the cerebral aquaduct (the duct that connects the third and fourth ventricles).

bi 232 (2 decks)

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