UNIT 8: Homeostasis and Neurophysiology Flashcards
What are the two systems involved in homeostasis?
the nervous and endocrine system
What roles does the nervous system play in Homeostasis?
Provide rapid sensory information, regulate the processing of sensory information and the generation of responses, and trigger specific target organ responses within seconds or minutes
What primary role does the nervous system have in Homeostasis?
it has a primary role in the complex behavioural processes that are responsible for maintaining homeostasis and reproductive functions
What role does the endocrine system have in Homeostasis?
they act as chemical messengers, regulate most aspects of metabolism, tissue growth, and reproduction
What are the two main cell types in the nervous system?
Neurons and Glia
What is a neuron?
Neurons are organized into circuits and control every activity in the body. Neurons also conduct electrical signals and release chemical signals to other cells (they cannot divide)
What is glia?
They act as support cells for neurons or neuronal processes (they can divide)
How many classifications of neurons are there, and what are they?
- Sensory Neurons, Motor Neurons, and Association/interneurons.
What is a sensory neuron?
they conduct impulses from sensory receptors to the central nervous system
What are motor neurons?
They conduct impulses from the central nervous system to target organs (muscles or glands)
What are association/interneurons?
they are located completely within the central nervous system and they integrate functions of the nervous system
What are motor neurons particularly classified?
Somatic motor neurons and autonomic motor neurons
What are somatic motor neurons?
they are the neurons that are responsible for reflexes and voluntary control of skeletal muscles
What are autonomic motor neurons?
supply involuntary targets such as smooth muscles, cardiac muscles, and glands
How many structural components are neurons classified as?
5: anaxonic, unipolar, pseudounipolar, bipolar, multipolar
What is anaxonic?
has no obvious axon (primarily in the CNS)
What is unipolar?
means there is only one axon
What is pseudounipolar?
this means that there is one axon that is branching into two
What is bipolar?
this means there are 2 axons
What is multipolar?
this has a large dendritic tree that receives information and one main output axon
Where do neurons receive information?
sensory receptors or other neurons
What are Glia cells?
Nonconducting but support neurons. There are 2 types found in the peripheral nervous system, and 4 are found in the central nervous system.
What are the 2 called in the PNS?
Schwann Cells and Satellite cells
What are Schwann Cells?
they produce myelin sheaths around the myelinated axons in the PNS. they surround these axons to form neurilemmal sheath (sheath of Schwann)
What are Satellite cells?
They support the functions of neurons within sensory and autonomic ganglia
What are the 4 called in the CNS?
Oligodendrocytes, microglia, astrocytes, and Ependymal cells
What are oligodendrocytes?
they form the myelin sheath around the central axons, producing “white matter” of the CNS
What is Microglia?
Phagocytose pathogens and cellular debris in the CNS
What are Astrocytes?
They cover capillaries in the CNS and induce the blood-brain barrier
What are Ependymal Cells?
They form the epithelial of brain cavities and the central canal of the spinal cord
What is Neurotransmission?
This is when neurotransmitters are released by the axon terminal of a neuron binding to and reacting with the receptors on the dendrites of another neuron
How are signaling neurons measured?
signalling by neurons involves electrical potentials and this can be measured by placing electrodes on the surface of the skull (electroencephalogram or EEG)
How is neural transmission achieved?
transient changes in the membrane potential
What is membrane potential?
this is the difference in ion electric potential between the inside and the outside of a cell (denoted as mV)
What is resting membrane potential?
this is a result of a combination of factors
What does this difference in charge mean?
This is the membrane potential
What are equilibrium membrane potentials?
The extent to which each ion contributes to the potential difference across the plasma membrane - or membrane potential - depends on its concentration gradient and membrane permeability
What is membrane potential determined by?
Since the plasma membrane is more permeable to K+ ions, the membrane potential is determined by K+ concentration gradient
What is the Nernst equation?
Allows for theoretical membrane equilibrium potential to be calculated for a particular ion when its concentrations are known
What is the Action Potential?
rapid change in the membrane potential of a neuron and is required to conduct nerve impulses (signals) along the length of the axon and on to the next
How are changes in membrane potential to resting potential caused?
They are caused by mechanical or ligated ion channels opening in response to stimuli
What happens when a threshold is reached?
Na+ will rush into the cell and the membrane potential will suddenly depolarize (become more positive) so that it moves toward the resting membrane potential of sodium
When will the Na+ channels close again?
This will occur when the membrane potential reaches ~+30mV
What happens when voltage-gated K+ channels open?
they repolarize the cells (the cell becomes more negative). The membrane potential will then shoot below the normal resting potential, close to the K+ equilibrium potential
What is the relative refractory period?
This is when cells are still excitable but there is more current required to bring it back to its threshold for another action potential.
What is the All or None Law?
this is once the threshold has been reached, and action potential will happen
What happens if an action potential does occur?
The size of the depolarizing stimulus will not affect the size of the action potential; it will always reach +30mV
What happens if action potential does not occur?
The size of the depolarizing stimulus will not affect the action potential duration
Where is action potential initiated?
at the axon hillock
