BIO 209 Exam 4- Nervous Tissue
Nodes of ranvier
gaps in the myelin sheath. only place where ions can enter the axon. action potentials jump from node to node
Functions of ependymal cells
line ventricles of brain and central canal of spinal cord. monitor/produce/assist circulation of CSF
Grey matter is made of what?
neuronal cell bodies, unmyelinated axons, glial cells
What three things lead to resting potential?
separation of charges across membrane (gradients), most anions can't diffuse across membrane, sodium and potassium pumps
What is the fourth phase of an action potential?
sodium and potassium pumps restore the gradients (from +30mV to -70mV)
What are the three divisions of the PNS?
Somatic (SNS), Autonomic (ANS), Enteric (ENS)
What is the name for the electrical signal that neurons and muscles use?
action potential
Characteristics of leak channels
always open, specific or non specific ions
Anions and cations in a resting membrane potential.
anions build up negative charges in the cytoplasm, cations build up positive energy on the extracellular side of the membrane
What is the name for the plasma membrane of the axon?
axolemma
What is the name for the cytoplasm of the axon?
axoplasm
What structures are found in the CNS?
brain and spinal cord
Functions of microglia
clear cellular debris/waste. phagocytosis
What is the conduction down unmyelinated axons?
continuous
What are the two main phases of an action potential?
depolarization and repolarization
What is the second phase of an action potential?
depolarization. sodium channels open, sodium flows in and changes internal charge to positive
What is found in the PNS?
everything outside of the CNS
What are nerve signals that cause depolarization called?
excitatory postsynaptic potential (epsp)
What are two things that are required for graded and action potentials?
existence of a resting membrane potential and presence of specific ion channels.
What does the sympathetic nervous system do?
fight or flight
What is the term for when a membrane becomes more negative?
hyperpolarization (-90mV)
What is the 5th phase of an action potential?
hyperpolarization. membrane potential becomes more negative (-90mV). ensures energy only flows one direction.
What are nerve signals that cause hyperpolarization called?
inhibitory postsynaptic potential (ipsp)
What neurons communicate between afferent and efferent nuerons?
interneurons or association neurons. multipolar
What does the ENS do?
involuntary, controls muscles and functions of the GI tract
What does the ANS do?
involuntary, controls smooth and visceral muscles
Neurotransmitter
molecules that excite or inhibit an effector
What neurons bring information away from the brain?
motor (efferent) neurons. multipolar
White matter is made of what?
myelinated axons and glial cells
Functions of oligodendrocytes
myelination
Functions of schwann cells
myelination of PNS axons.
It's called a ganglia in the PNS: what is it called in the CNS?
nuclei
Characteristics of voltage channels
open/close in response to change in membrane potentials
Characteristics of ligand gated channels
open/close in response to ligand binding. specific or non specific ions
Characteristics of mechanical channels
open/close in response to mechanical stimuli. vibration/touch/hearing, etc.
Membrane potential
plasma membrane of excitable cells
Resting membrane potential (RMP)
potential energy at resting state, rests at -70mV
what to interneurons do?
process sensory info and generate a motor response
What is the 6th phase of an action potential?
refractory period. cell can't generate another action potential
What is the third phase of an action potential?
repolarization. sodium channels close, potassium channels open and potassium flows out. negative charge returns back to negative
What does the parasympathetic nervous system do?
rest and digest
What is the first phase of an action potential?
resting phase. ready to carry action potential
What is the conduction down myelinated axons?
saltatory
Relative refractory period
second action potential can be generated if second stimulus is large enough
Absolute refractory period
second action potential cannot be generated
What neurons bring information into the brain?
sensory (afferent) neurons. unipolar
What are the three functions of the nervous system?
sensory function (detects stimuli), integrative function (provides response to stimuli), motor function (effectors activated)
Functions of astrocytes
support, regulate chemical environment, creates BBB of the capillaries
Functions of satellite cells
surround neuron cell bodies in PNS. regulate exchange of materials between cell bodies and interstitial fluid.
What are the divisions of the ANS?
sympathetic and parasympathetic
Why do action potentials travel faster down myelinated axons?
they are able to jump from node to node of ranvier
What is an effector?
things that a nerve can communicate with (another nerve, muscles, or glands)
What is the term for the point that has to be reached to send an action potential?
threshold
It's called a nerve in the PNS: what is it called in the CNS?
tract
Characteristics of action potentials
travel long distances, independent of stimulus "all or nothing", always depolarization
Characteristics of graded potentials
travel short distances, strength of response depends on strength of stimulus. depolarizing and hyperpolarizing
What does the SNS do?
voluntary, receives info from sensory receptors, control of skeletal muscles
How many sodium and potassium are exchanged by the pumps?
+3 sodium ions, +2 potassium ions
What are the two divisions of the nervous system?
Central Nervous System (CNS) and Peripheral Nervous System (PNS)
What percent of the brain is glial cells?
90%