Physio I Exam 3

What are the parts of the CNS?

Brain and spinal cord.

What are the 2 parts of the PNS?

Somatic and autonomic

Where are afferent nerve signals sent?

To the brain

Where are efferent nerve signals sent?

To the periphery

Which type of cells are more numerous?

Neurons vs Non-neuronal

Non-neuronal

True/False: Neurons can undergo cell division but non-neuronal cells can’t.

False, non-neuronal cells can but neurons can’t

What are the functions of the non-neuronal cells/neuroglia? (6 main ones)

1. Myelin formation

2. Control of extracellular environment

3. Axon development/regen

4. Immune function

5. BBB system

6. Synapse formation/removal

What are the non-neuronal cells in the PNS?

Satellite cells and Schwann cells

What are the non-neuronal cells in the CNS?

1. Astrocytes

2. Oligodendrocytes

3. Microglia

4. Ependyma

What shape are astrocytes?

Star-shaped

Where are astrocytes present?

Between nerve cells and blood vessels

What are the functions of the astrocytes?

1. Provide nutrients & regulate conc. of ions (Calcium)

2. Structural support for synapses

3. Forms blood brain barrier

What shape are oligodendocytes?

Marble shaped

What is the function of oligodendrocytes?

Form myelin sheaths around axons in CNS

What is the difference between myelination in the CNS vs in the PNS?

In the CNS, one axon can be myelinated by many olig. or one olig. can myelinate many axons.

In the PNS, one Schwann cell myelinates one axon.

What happens when there is a disruption to the oligodendrocytes?

Myelin sheath disorders occur, like multiple sclerosis

What is the function of microglia?

Scavenge and degrade dead cells & protect from invading microorganisms

What is the function of the ependyma cells?

Produce CSF and line fluid filled ventricles in the brain and central canal of spinal cord

What are the coverings for the CNS?

The cranium and the meninges

What makes up the meninges from top to bottom?

Top - Dura mater

Middle - Arachnoid mater

Bottom - Pia mater

What is meningitis?

A bacterial/viral/fungal infection leading to inflammation of the meninges that can cause paralysis and mental retardation

What layers does meningitis affect?

The arachnoid mater and pia mater

Who is most susceptible to meningitis?

Children and infants

What are the cerebral ventricles from top to bottom?

Top - Lateral ventricles

Middle - Third ventricle

Bottom - Fourth ventricle

Which ventricle is closest to the spinal cord?

The fourth ventricle

Which ventricle is the largest?

Lateral ventricle

What is the lateral ventricle made of?

Anterior, posterior, and inferior horns

What is the function of the third ventricle?

Communicate with lateral ventricle via interventricular foramens

What is the fourth ventricle bound by?

Bound ventrally by pons and medullar oblongata and dorsally by the cerebellum

What is the opening in the fourth ventricle for?

For CSF to exit the ventricular system

What happens when there is damage to the fourth ventricle?

Detrimental for walking and movement

Where is the choroid plexus?

In the ventricles of the brain

What is the choroid plexus made of?

Modified ependymal cells surrounding capillaries and loose connective tissue

What is the function of the choroid plexus?

Produce and secrete most of the CSF in the CNS

What is the source of CSF?

Cerebral ventricles and choroid plexus

What is the rate of CSF formation and the total volume of CSF?

0.5 mL/min and 140-200 mL

Where does the CSF drain to?

The cisterna megna to subarachnoid space to be absorbed into veins at arachnoid granulations

What are the functions of CSF? (4)

1. Buoyancy for brain and membranes

2. Mix with brain ECF

3. Maintain intracranial pressure

4. Protection during sudden movements

What is hydrocephaly?

An imbalance of CSF produced vs absorbed, causing buildup in the cavities of the brain, putting pressure on the brain and causing damage

Who most commonly suffers from hydrocephaly?

Children and infants

What is hydrocephaly most commonly characterized by?

Head enlargement from fluid buildup

What is the treatment for hydrocephaly?

A tube/shunt inserted in the lateral ventricle for drainage

What do the 2 internal carotid arteries form?

The Circle of Willis

What do the two vertebral arteries form?

The basilar artery

What percentage of total oxygen consumption does the brain account for?

18%

What causes cerebral ischemia?

An occlusion in the carotid in old people

What two properties affect cerebral blood flow?

Blood pressure and cerebrovascular resistance

What happens when arterial BP drops below 70 mmHg?

Cerebral flow is compromised, causing orthostatic hypotension (feeling faint after lying or sitting too much)

What is polycythemia?

A type of blood cancer where there is a high number of RBC in blood, making the blood thick

What is unique about cerebral capillaries?

They are non-fenestrated with tight junctions between their endothelial cells

What are cerebral capillaries surrounded by?

Astrocyte feetsies

What can pass easily through the cerebral capillaries?

CO2, O2, and water

What is the blood brain barrier?

A highly selective semipermeable border of endothelial cells

What forms the blood brain barrier?

1. Endothelial cells of capillary walls

2. Astrocyte end feets

3. Pericytes in capillary basement membranes

What is the function of the blood brain barrier?

To prevent passage of pathogens, toxins, and solutes into the brain, and also to insulate the brain from damage

What is the definition of a circumventricular organ?

An area in the brain in and around the hypothalamus where the BBB doesn’t exist

What are the circumventricular organs?

PP-ASS:

P- post pituitary

P- pineal body

A- area postrema

S- supraoptic crest

S- subfornical organ

What could breakdown the BBB?

Infection, irradiation, tumors, sudden increases in BP

What is a column of nervous tissue continuous with brain?

The spinal cord

Where does the spinal cord begin and end?

Begins just outside cranial cavity and ends between 1st and 2nd lumbar vertebrae

How many segments of the spinal cord are there, and what are the categories?

31 total segments

Cervical (8)

Thoracic (12)

Lumbar (5)

Sacral (5)

Coccygeal (1)

What kind of matter is the spinal cord made of?

Gray matter with posterior, lateral, and anterior horns

What are the functions of the spinal cord? (2)

1. Conduction of info to and from brain

2. Integrative center for reflexes (patellar, withdrawal, evacuation)

Where does sensory information travel on the ascending tracts?

From the periphery to the brain

Where does sensory information travel on the descending tracts?

From the brain to the periphery

What are the parts of the ascending tract of the spinal cord, and what sensations do they account for?

1. F. gracilis & cuneatus - touch, pressure, and body movement

2. Spinothalamic - pain and temperature

3. Spinocerebellar - muscle coordination in legs and trunk

What are the parts of the descending tract of the spinal cord, and what impulses do they account for?

1. Corticospinal (pyr) - voluntary movement

2. Reticulospinal (expyr) - muscle tone and sweat

3. Vestibulospinal (expyr) - equilibrium and posture

4. Rubrospinal (expyr) - muscle coordination and posture control

5. Tectospinal (expyr) - head and eye movements

What would happen if there were an injury to the corticospinal tract of the spinal cord, and is this in the ascending or descending tract?

Descending. The person would experience flaccid paralysis

Contrast the symptoms of flaccid and spastic paralysis

Flaccid - loss of muscle tone and muscle atrophy

Spastic - increased muscle tone (stiffness) and no atrophy

What are the 4 parts of the brain?

1. Brain stem

2. Diencephalon

3. Cerebellum

4. Cerebrum

Where does the brain stem start and end?

Starts: base of cerebrum

Ends: foremen magnum

What type of matter is the brain stem composed of?

White and grey matter

What are the three parts of the brain stem?

1. Medulla oblongata (myelencephalon)

2. Pons (metencephalon)

3. Midbrain (mesencephalon)

What do the visceral activity centers of the medulla oblongata regulate?

Cardiac, vasomotor, respiratory, and swallowing activities

What is the bulging area of the brain?

The pons of the brain stem

The reticular activating system (RAS) connects what parts of the brain?

The hypothalamus to higher brain centers

What acts as a sensory gating system for ascending and descending tracts of the brain?

RAS formation

What is the RAS formation associated with?

Sleep/wake cycles

What formation is affected by hypnotics and anesthetics?

RAS formation

What part of the brain is the hypothalamus and limbic cortex located in?

The diencephalon

What is associated with the hypothalamus?

Hunger/thirst, body temp control, water and electrolyte balance

What is associated with the hippocampus?

Learning/memory

What is the function of the cerebellum?

Coordination of skeletal muscle activities

How many lobes are in the cerebrum and what are they called?

Four: Frontal, parietal, temporal, occipital

What comprises the cerebrum?

Cortex, white matter, and basal ganglia

What does the motor area of the cerebrum regulate?

Skeletal muscle movement

What does the sensory area of the cerebrum regulate?

Reception of sensations

What does the association area of the cerebrum regulate?

Higher order thinking like learning to speak

Which hemisphere of the brain is usually dominant in humans?

The left

What two areas regulate our ability to talk?

Broca’s area and Wernicke’s area

What are defects in the Broca’s area associated with?

Trouble speaking properly

What part of the basal ganglia of the cerebrum is associated with Parkinson’s disease?

The substantia nigra

What system is the amygdala and hippocampus a part of?

The limbic system

What is the fear center of the brain?

Amygdala

What is the learning and memory center of the brain?

Hippocampus