Module 3 Chapter 13 & 14 Organization of the Neural Function and Somatosensory Function, Pain, Headache, and Temperature Flashcards
What are the two major cell types found in the nervous system? What are their basic functions?
Neurons - functioning cells of the nervous system. They are excitable and conduct impulses.
Neuroglial cells - protect and provide metabolic support for the nervous system.
CNS - components
The central nervous system is the control center for the body. It is made up of the brain and spinal cord.
PNS - components
The peripheral nervous system is the information highway, connecting the bodies parts with the brain. Transmits sensation, movement impulses, and many other things between the two.
Afferent VS efferent
These two pathways are found in both the PNS and CNS.
Afferent pathways are incoming, sensory pathways. Transmit information to the brain.
Efferent pathways are outgoing, motor pathways. Transmit information from the brain.
Parts of neuron
There are three main parts of a neuron.
1. Cell body
2. Dendrites - these are long branching extension of the nerve cell. Send and receive information from surrounding cells.
3. Axons - conduct nerve impulses. Long, unbranched.
Astrocytes
A type of neuroglial cell that plays a role in forming the blood-brain barrier. The blood brain barrier prevents toxic material from enter the brain.
These are the most prevalent neuroglial cells. Play a role in potassium uptake, scar tissue formation, gliosis, and communication with capillaries.
Oligodendrocytes and Schwann cells
These are two types of neuroglial cells. They play the role of forming myelin.
What is myelin/myelin sheaths? What does it do?
Myelin is a lipoprotein. It is primarily lipid substance that coats the neuron cell processes. The presence of myelin increases velocity of nerve impulse conduction (makes neurologic processes faster).
What is the white matter?
The white matter is the myelin sheaths. The primary lipid composition gives these structures a whitish color.
Microglia
Small phagocytic neuroglial cells.
What are the neuroglial cells of the PNS? What do they do?
Satellite - form a basement membrane to prevent the diffusion of large particles
Schwann cells - create myelin
White Vs Gray matter
White - myelin sheaths (tract system)
Gray - cell body
The autonomic nervous system
Considered part of the PNS system. Plays a role in blood vessel relaxation vs constriction, blood pressure, temperature, digestion, bowel and bladder function, respiration, and metabolism. Strongly tied to emotions.
- The sympathetic nervous system - “Fight or flight”. Hormones secreted from the adrenal glands on top of the kidneys result in activation of the sympathetic nervous system in times of stress. Results in:
- Increased BP, vasoconstriction, pupillary dilation, shunting of blood from skin into the heart and brain, constriction of the GI and Gu sphincters, increase in blood sugar. All these adaptations are to prepare the body for critical, life and death situations. - The parasympathetic nervous system has opposite effects. It promotes digestion, elimination, pupillary constriction gland secretion.
Somatic nervous system
Sensory and motor nerves
Metabolic requirements of the brain
The brain receives 15-20% of the total, resting CO.
Consumes 20% of oxygen.
Cannot store oxygen like other areas of the body, so when blood flow is cut off the results are immediate.
The brain without oxygen
The brain takes a hefty amount of the body’s total oxygenation to perform it’s functions. The brain has no oxygen or glucose reserve. The brain without oxygenation quickly fails and irreversible damage occurs within seconds.
Neurons
1. Division
2. Replacement
3. Plasticity
4. Requirements
- Neurons cannot divide.
- Neurons that die due to aging or injury cannot be replaced.
- Plasticity - the neurons ability to assume the functions of damaged neurons. How neurologic function can continue at the same level post injury and throughout the aging process.
- Neurons require a constant supply of oxygen and glucose to continue functioning. Vulnerable to hypoxia and hypoglycemia.
Plasticity of neurons
Neurons have the ability to assume the role of other neurons that are damaged or injured.
The Circle of Willis
Redundant way for the brain to receive blood supply. Promotes collateralization as well.
Anterior Cerebral artery
Frontal lobes
Middle cerebral artery
Frontal lobe and lateral surfaces of the temporal and parietal lobes.
Which cerebral artery is most frequently affected during strokes? How does this present and why?
The middle cerebral artery is the most commonly affected during strokes. This presents with the common symptoms of a stroke - trouble with speech, movement, and sensation. That is because the middle cerebral artery supplies blood to the frontal (movement/Wernicke), parietal (sensory), and temporal (speech) lobes.
Posterior cerebral artery
Supplies blood to temporal and occipital lobes
Choroid Plexuses
Where CSF is made. A collection of arteries and veins that come in close proximity and function to filter plasma to make CSF.
Function of CSF
Cushion and nourishes the brain
Hydrocephalus
Excessive accumulation of CSF
Ependymal Cells
One of the glial cells. Plays a role in filtering the blood for CSF.
How does the brain get blood flow?
The brain gets blood flow from the internal carotids and the vertebral arteries.
The circle of Willis ensures adequate flow to all parts of the brain. Does this by ensuring redundant flow is available for the brain tissue.
How does CO2 affect blood flow to the brain?
CO2 is a powerful vasodilator. Under conditions where there is adequate circulating volume, increased CO2 in the body will improve blood flow to the brain.
Synapse
1. Types
How neurons communicate. There is a presynaptic and postsynaptic cleft.
1. Electrical - the quicker form of passing information between neurons. Ions passing through the gap junctions allow action potentials to quickly pass along impulses.
2. Chemical - slower, more common. Communicate across the synaptic cleft via neurotransmitters. Two types - excitatory and inhibitory.
Excitatory VS Inhibitory and how they work
These are types of chemical synapses.
Excitatory function via depolarization.
Inhibitory function via hyperpolarization.
Where are synapses primarily located?
Thousands of synapses are located on the dendrites of the neurons.
What are neurotransmitters?
Substances that excite, inhibit, or modify neuron responses. Ach, norepinephrine, and epinephrine are examples.
Cholinergic receptors VS adrenergic receptors
Cholinergic receptors - activated by Ach. Part of the PNS system.
Adrenergic receptors - activated by norepinephrine and epinephrine. Part of the sympathetic nervous system.
What are interneurons?
connect the sensory (afferent) and motor (efferent) parts in the spinal cord
What two neurological conditions are associated with destruction of myelin? Describe these conditions.
- GBS - the immune system attack myelin layer. Happens in the PNS which results in ascending muscle paralysis as the demyelination works peripherally and then results are seen more centrally.
- MS - loss of myelin layer in the CNS. Symptoms are seen with brain and spinal symptoms.
Types of Sensory/Afferent innervation
- General somatic
- Special visceral
- General visceral
Types of Motor/Efferent Innervation
- General visceral
- Pharyngeal
- General somatic
Two important spinal reflexes
- Withdraw reflex - introduction to an offending stimulus result in withdrawal of the affected limb, typically by flexion. Takes precedence over other reflexes.
- Myotatic or stretch reflex - a reflex to maintain propriocception.
Where does interpretation of objects and events occur in the brain?
Interpretation of objects and events occur in the temporal lobe.
What important structures are located in the diencephalon?
- Thalamus
- Hypothalamus
Meninges
Pia
Arachnoid
Dura mater
These are spaces that are in place to protect the brain.