Week 1 Neuro Flashcards
What are the two main divisions of the nervous system
1) CNS: Brain and spinal cord
2) PNS: Peripheral nerves and ganglia
What two things do neurons do?
1) Conduct “electrical” signals (action potentials)
2) Release “chemical” signals (neurotransmitters)
What are the three functions of the nervous system?
1) Control of movement and some functions using motor nerves
2) Detection of external stimuli using sensory nerves
3) Association neurons in the CNS create connections like little highways, enabling behaviour, thoughts and emotions
What 3 components do neurons break down into?
Cell body, dendrites, axons
What are dendrites?
Recieves info from sensory receptors or other cells and sends it to the cell body
What are axons?
Delivers electrical signals from the cell body to another neuron or an effector group, which is a muscle or gland
How do neurons function?
Neurons move info quickly by sending electrical signals (action potential) from one location to another, and converting them to chemical signals at a synapse
What is the functional classification of neurons based on?
Based on the direction in which neurons conduct impulses
What do sensory or afferent neurons do?
Conduct impulses from sensory receptors (PNS) into the CNS
What do motor or efferent neurons do?
Conducts impulses from sensory receptors (PNS) out of the CNS, and to effector organs like muscles or glands
What do association or interneurons do?
Located in the CNS, they help integrate and coordinate CNS functions
What defines somatic motor neurons?
Reflex and voluntary control of skeletal muscles
What defines autonomic motor neurons?
Involuntary control of smooth muscle, cardiac muscle and glands
What can autonomic neurons be further subdivided as?
Can be further subdivided as sympathetic and parasympathetic
What are the 3 steps in a simple neural circuit?
1) Sensory, Afferent (carry signals to CNS).
2) Motor or Efferent (carry signals from CNS).
3) Interneurons - send signals from one neuron to another
What are the 4 types of neurons?
1) Pseudopolar (unipolar)
2) Bipolar
3) Multipolar
4) Anaxonic
What are pseudopolar (unipolar) neurons?
Sensory neurons with one process that splits into two ( meaning single extension divides into two branches, one branch acts like a dendrite to recieve signals and the other acts like an axon to send signals)
What are bipolar neurons?
Found in retina and cochlea, with two processes, meaning it has one dendrite and one axon to send signals, on opposite sides of the cell body.
What are multipolar neurons?
Most common type, used for motor and association functions, with many dendrites and one axon
What are anaxonic neurons?
Found in some CNS neurons, with no clear axon
What are the supporting cells in the PNS?
Schwann cells and satellite cells
What are schwann cells?
Supporting cells in the PNS, they form myelin sheaths around PNS neuron axons
What are satellite cells?
Supporting cells in the PNS, they support neuron cell bodies by wrapping around them, within ganglia of the PNS
What are the supporting cells of the CNS?
Oligodendrocytes, Microglia, Astrocytes, Ependymal cells
What are oligodendrocytes?
Supporting cells in the CNS, form myelin sheaths around CNS neuron axons (like schwann cells in the PNS)
What are Microglia?
Supporting cells in the CNS, MOve through CNS, and pick up and eat (phagocytose) debris
What are Astrocytes?
Supporting cells of the CNS, Star shaped, help regulate external environment of neurons in the CNS
What are ependymal cells?
Supporting cells of the CNS, lines the ventricles (cavities) of the brain and spinal cord
What are the most abundant glial cell in the CNS and how much nervous tissue does it take up in some areas of the brain?
Astrocytes are the most abundant glial cell in the CNS, making up up to 90% of the nervous tissue in some areas of the brain
Where do astrocyte processes end and why?
Astrocyte processes end on capillaries or on neurons (axon, cell body, dendrite), so they can influence interactions between neurons and blood
What 7 things do astrocytes/supporting cells of the CNS do?
1) Take up k+ from ECF which may help maintain proper ionic environment for neurons. The k+ is released when neurons fire.
2) Can take up glutamate and transform it to glutamine, which can be released back into neurons, which can use it to reform glutamate
3) The “end feet” surrounding blood capillaries take glucose from blood, metabolize it to lactate, then release it for neurons to use
4) Astrocytes are needed for formation of synapses in the CNS
5) Astrocytes regulate neurogenesis by aiding stem cells to become glial cells or neurons
6) Helps with the formation of the blood brain barrier
7) Releases neurotransmitters like glutamate, ATP, adenosine, D-serine, etc. that can stimulate or inhibit activity of neurons
How are capillaries in the brain different from those of most other organs?
Capillaries in the brain’s endothelial cells are joined by tight junctions, creating a barrier that controls what can enter the brain and can keep harmful substances out.
Other organs capillaries have pores between endothelial cells
What can cross the BBB and enter the brain?
-Nonpolar molecules like O2 and CO2, as well as substances like alcohol and barbiturates can pass through the phospholipid components of the cell membrane.
-Other molecules need specific processes like active transport or endocytosis to get through
What kind of molecules can’t enter the brain?
Molecules that are too highly charged, too large and not lipid soluble can’t enter the brain.
What do astrocytes influence about the BBB?
Astrocytes influence the structure and function of the BBB.
What does nicotine do in the brain?
Nicotine hijacks and binds to acetylcholine receptors which increases the level of dopamine and other neurotransmitters
What do components other than nicotine in tobacco smoke do in the brain?
Other components decreases MAO activity which is an enzyme that is needed to breakdown neurotransmitters like dopamine, seratonin, etc, so there will be elevated levels of these, which increases mood
How does alcohol impact the CNS?
-Crosses BBB
-Alcohol is a CNS depressant that slows brain activity, affecting areas that control behaviour, speech and memory.
-It makes people more social, slurred speech, slower reaction time and memory issues.
-Effects vary based on dose, body size, gender, genetics
What does tylenol do in the brain?
-Crosses BBB
-Inhibition of nitric oxide through a variety of neurotransmitter receptors including N-methyl-D-aspartate and substance P
What is rabies and why is it so bad? Is there a cure?
-Rabies is a deadly viral infection from being bit by an animal. Rabies crosses BBB and infects the brain, and immune cells and antibodies can’t enter the brain to help
-Once symptoms appear, rabies has no cure, but early treatment with anti-rabies antibodies can help slow infection
Why are neurological disorders difficult to treat?
Therapies and drugs can’t get across the BBB to treat the disorders
How was it discovered that the BBB can be crossed?
Using an ultrasound to disrupt the BBB allowed access into the brain
What is muscle atrophy?
Shrinking or weakening of muscles due to lack of use, disease or nerve damage
What does the autonomic nervous system do?
Helps regulate activities of glands, smooth muscles and cardiac muscle. They are an integral aspect of the physiology of most body systems
What does the ANS subdivide into, and what are these subdivisions associated with
Into the Parasympathetic and sympathetic nervous system.
PSNS: Nightime, rest and digest
SNS: Daytime, Fight or flight
How do most organs function regarding PSNS and SNS? What is this called?
Organs recieve input from both systems, and they mediate opposing responses in effector organ. This is called dual innervation
What 4 organs don’t use dual innervation, and the SNS takes over? How is this regulated?
-Adrenal Medulla: in adrenal gland, produces adrenaline and noradrenaline
-Arrector pili muscles in the skin: muscles associated with goosebumps
-Sweat gland in the skin
-Most blood vessels
*Regulation achieved by increases or decreases in firing rate of sympathetic fibres, since theres no PSNS to mediate
How are autonomic nerves classified? What do Cholinergic neurons and adrenergic neurons release? How do the neurotransmitters mediate target organ response?
-Autonomic nerves release a main neurotransmitter across the synapses
*Cholinergic neurons -> release acetylcholine (ACh)
*Adrenergic neurons -> release NE (or E)
-ACH and NE bind to different receptors to mediate target organ response
What is the neurotransmitter for all preganglionic fibers? What is the transmission at these synapses?
-ACh is the neurotransmitter
-Transmission is cholinergic
What neurotransmitter is released by most parasympathetic postganglionic fibers? What is the transmission at the synapses?
-Neurotransmitter is ACH
-Transmission is cholinergic
What neurotransmitter is released by most sympathetic postganglionic fibers? What is the transmission at the synapses?
-Neurotransmitter is NE
-Transmission is adrenergic
What functions of the body does the ANS control?
HR, BP, peristalsis, sweating, etc.
What can cause dysautonomia (dysfunction of ANS)?
Lyme disease, POTS, brain injury, diabetes, genetics, etc.
What is lyme disease?
-Causes dysfunction of ANS
-Bit by an infected tick, infected saliva disrupts local immune response, allowing spirochetes to multiply in the skin. Immune response causes circular lesion, but neutrophils needed to fight the infection don’t appear. Bacteria spread via the bloodstream to joints, nervous system, and distant skin sites.
What is POTS?
- A type of dysautonomia
POTS (Postural Orthostatic Tachycardia Syndrome) is a condition where your heart rate increases abnormally when you stand up, often causing dizziness, lightheadedness, fatigue, or even fainting. It happens because your body has trouble regulating blood flow and circulation when you change position.
What are common forms of synesthesia?
-When letters or numbers are involuntarily seen as having specific colours
-Sounds can have colour, taste, etc
How many digits can the average person hold in working memory at any given time?
7 digits
