Nervous system Flashcards
CNS
central nervous system, comprised of the brain and spinal chord. It a neuron is in the CNS, the whole neuron has to be included in either the brain of spinal cord. Dreaming and thinking and even memory storage can be kept entirely within the CNS without need for PNS stimulus
PNS
peripheral nervous system, all nerves that extend out past the brain and spinal cord. Included afferent and efferent neurons
Afferent neurons
sensory input
Efferent neurons
somatic sensory neurons (sympathetic, parasympathetic), autonomic neurons
Information transmission pattern
Stimulus-receptor-afferent pathway-control center-efferent pathway-effector-response. Sends information from the PNS to the CNS, if action is needed to maintain homeostasis, the CNS sends signal to PNS
Somatic nervous system (PNS)
controls the voluntary movements of skeletal muscles
Autonomic nervous system (PNS)
controls involuntary movements of muscles like lungs and heart and smooth muscle tissue. further subdivided into sympathetic and parasympathetic systems
Enteric nervous system (PNS)
controls gastrointestinal tract, semi-independent, contains more neurons than the whole spinal chord
Neuron structure
cell body (soma), dendrites, axon, and axon terminals. Have very high metabolic rates and require high levels of oxygen and glucose
Cell body or soma
surrounds nucleus, major role in synthesizing proteins
Dendrites
branches the shoots off of soma, receive information through numerous receptors on membrane, through chemical neurotransmitters
Axon
long branch that goes off of soma, the point of origin where it branches off of the cell body is called the axon hillock which functions to send information. Axon can extend to more than a meter! Because of this the axon has microtubules surrounded by myelin.
Anterograde transport
motor proteins “walk” along the microtubules in the axon away from the soma
Retrograde transport
motor proteins “walk towards the soma through microtubules in he axon
Myelin
totally separate cells that wind and coil around axon. Essential for insulation and sped up action potential propagation. Comes from oilgodendorcyte in CNS and schwann cell in PNS
Axon terminals
The end of an axon. Converts electrical signal into a chemical one through synaptic transmission.
Amitotic nuerons
most are this way, Neurons that have lost the ability to divide. Lifespan of more is 100 years. Exception neurons are olfactory (smell), and hippocampal (memory).
Multipolar neurons
most common type in humans, 99%. Defined as having three or more processes (dendrites) that extend from the body
Bipolar neurons
Rare, appear in retinas and olfactory, have a cell body and a process in both directions. One is called a dendrite and one is called and axon.
Unipolar neurons
have a single, short process that branches into two more processes. One is directed in the peripheral direction and one in the central. Primarily associated with sensory neurons and are found in PNS
Sensory neurons
afferent neurons transmit signals from external environment or organs to CNS for processing. Almost all are unipolar
Motor neurons
Efferent neurons transmit information from CNS to effectors. Most are multipolar
Interneurons
located between motor and sensory, most are confined to CNS
Astrocyte
located in CNS, it is the protector/mother of the neuron. It wraps its processes around blood vessel and hooks onto neuron. It stores glycogen, absorbs extra K+, synthesizes neurotransmitters, secretes growth factor, and modulates blood flow.
