Nervous Tissue

Study help/reviewing concepts. These questions will greatly help you do well in the  course and to learn the material. Not everything is covered. 

1. Define afferent and efferent. 

Afferent: carries sensory info from peripheral nervous system sensory receptors to central nervous system (towards CNS to transit sensory information)

Efferent: carries motor commands from central nervous system to peripheral nervous system (away from CNS for control actions)

2. What are the functions of the nervous system? 

Sensory input, integration, motor output

3. What are the differences between a sensory neuron and a motor neuron?  

Sensory neurons: transmits sensory information from sensory receptors towards CNS, afferent, located outside of the CNS

Motor neurons: transmits signals from CNS to muscles/glands for a response (involuntary/ voluntary movements, and glandular secretions) located inside CNS

4. What are receptors? 

structures/proteins that detect changes or respond to stimuli usually proteins that change shape


5. What is a neurotransmitter in general terms, what does it cross and what is its function? 

A chemical messenger that transmits signals across a synapse, it cross the synaptic cleft (gap between two neurons or a neuron and cell), 

Function is to excite or inhibit neural activity through direct effects (open close channels w ACh) or indirect effects (g-proteins , intracellular enzymes)

G-proteins: a neurotransmitter bits to an inactive g protein that activates adenylate cyclase that converts ATP to cAMP which is a secondary messenger that can activate enzymes and open ion channels (ex. Epinephrine + norepinephrine flight/fight response)

Intracellular enzymes: lipid-soluble gases (NO, CO) diffuse into cell and activate enzyme that will produce a secondary messenger to open channels and change metabolism/activity


6. What are the categories of neuroglia cells in both the CNS and PNS and what are their  primary functions? 

CNS | ependymal cells: line the central canal of spinal cord and ventricles of brain to secrete, circulate (with cilia or microvilli), and monitor CSF 

Astrocytes: maintain blood-brain barrier to isolate CNS to protect the brain from harmful substances, repair/support neurons through neurorehabilitation and neuroplasticity 

Oligodendrocytes: enhance signal transmission by wrapping around axons to form myelin sheaths (also makes part of the brain look white) 

Microglia: immune cells of CNS by migrating through neural tissue to clean up cellular debris, waste products, and pathogens

PNS | satellite cells: surround and support ganglia (cell bodies)by regulating environment 

Schwann cells: form myelin sheath (neurilemma) same function as oligodendrocytes


7. What does myelination do to conduction speed? Why? 

It increases speed by insulating nerves with myelin to block leakage channels so more nerves can pass through


8. What are the differences between gray and white matter? 

White matter: regions of  CNS has myelinated nerves

Gray: unmyelinated areas of CNS 


9. What is an action potential? What exactly happens step by step? 

Its an all-or-nothing response if the stimulus reaches a certain threshold that is important for nerve impulses, muscle contractions, and communication

  1. Unstimulated axon reaches resting potential of -70mV

  2. Graded potentials to reach -55mV (threshold)

  3. Depolarization voltage-gated Na+ channels open and Na+ enter rapidly changing the potential to +30mV

  4. Repolarization happens and the voltage-gated Na+ channels close and the voltage-gated K+ channels open and K+ leaves changing potential to -70mV

  5. Hyperpolarization happens voltage-gated K+ channels coles slowly close polarity reaches -80mV

  6. All channels close and resting conditions continue of Na+/K+ pumps and potential is back to -70mV


10. What is a resting potential? Why do you see a certain charge inside the cell (think ions,  etc.). Draw a basic image of a cell and the ions, etc involved. 

Resting potential is the charge when the membrane isn’t actively sending a signal (-70mV). The charge is typically negative because it pumps 3 Na+ ions out and 2 K+ in so it is easier for the K+ ions to leak out making the inside of the cell more negative. 

11. Na+, K+ ATPase. What does it do? 

Is is a pump that uses ATP to move sodium out and potassium into the cell against the gradient to maintain resting potential and normal cell function

12. Explain the difference in AP conduction between myelinated and non-myelinated  neurons? 

unmyelinated: use continuous conduction so many voltage-gated channels that are very closely together due to leakage channels making conduction speed slow

myelinated: use saltatory conductions due to myelination and action potential jumps to nodes of ranvier (gaps between the myelin sheaths) making conduction speed fast

13. Define depolarization, hyperpolarization. 

Depolarization: membrane potential becomes less negative due to Na+ channels opening up allowing Na+ to rush in

Hyperpolarization: the membrane potential becomes more negative because K+ channels open allowing K+ to leave the cell and Cl- to enter. 

14. What is the somatic nervous system? Autonomic nervous system? 

Somatic Nervous System (SNS): part are the PNS and controls skeletal muscle movements that is responsible for voluntary movements

Autonomic Nervous System (ANS): part of the PNS that controls smoot muscles, heart, glands etc and its responsible for involuntary control consisting of two parts sympathetic (fight or flight,) and parasympathetic (rest and digest)

15. Compare electrical and chemical synapses. 

Electrical: very fast biodirection signal transmission from one cell to another another through gap junctions always excitatory

Chemical: slower unidirectional signal transmission from presynaptic to postsynaptic cell with the use of a neurotransmitter that can either be excitatory or inhibitory depending on the protein bound

16. What is a graded potential? What channels are involved? 

The temporary change of a charge of a cell with the use of ligand-gated and mechanically-gated channels.

17. Compare the different fiber types.

A- fastest, myeinated, larger 

B- intermediate, myelinated, medium

C- slowest, unmyelinated, small


18. What are the types of channels?

Leakage: are always open, nerve cells have more K+ than Na+ leakage channels so permeability to K+ is higher

Chemically/ligand gated: open in the presence of certain chemicals (ex. ACh) at a binding site. chemicals=ligands

Voltage-gated: respond to changes in transmembrane potential, must have large enough voltage to open

Mechanically gated: respond to membrane distortion found in sensory receptors.


19. Describe the relationship between permeability and the amount of channels open.

Directly proportional relationship


20. Where are voltage-gated channels found?

Neural axons, skeletal muscle sarcolemma, and cardiac muscles


21. What happens when myelin degrades due to disease?

Communication stops, death due to respiratory failure


22. What is Adrenoleukodystrophy (ADL)

An X-linked recessive disorder that leads to an inflammatory effect due to mutating the gene that the protein the body needs to break down fat called VLCFA, leading to more VLCFA destroying the myelin sheath.