Nervous System Flashcards
which animals dont have nervous systems?
sponges.
jellyfish have “nerve nets” but this still counts. many animals lack cephalization (a brain), so instead have clustered ganglia that act as integrating centres.
how do neurons communicate?
chemical and electrical signals
which are the 3 main divisions of neurons
afferent sensory
integrating
efferent motor
which division of neurons are in the CNS?
integrating centres
which division of neurons are in the PNS
efferent and afferent
how do afferent neurons transmit information?
they send information from the stimulus to the integrating centre
how do efferent neurons transmit information
information from integration centre to the effector
describe the vertebrate nervous system
high degree of cephalization (large brains)
unique hollow dorsal nerve cord (spinal cord)
part if nervous system encased in bone/cartilage (CNS)
part of nervous system extends into periphery of body (PNS)
nervous system, top to bottom
cerebrum
cerebellum
brainstem
cervical nerves
spinal cord
thoracic nerves
lumbar nerves
sacral nerves
coccygeal nerves
draw it! (slide 14)
what is in the CNS?
brain and spinal cord
(interneurons perform integrating functions of CNS, including processing sensory info from afferent neurons and sending commands to efferent neurons)
draw the organization of the nervous system!
slide 15
CNS feeds into two divisions:
afferent and efferent
efferent branch has two divisions:
somatic (voluntary) and autonomous (involuntary)
what does the somatic nervous system feed into
skeletal muscle, since it’s voluntary control
what are the 3 divisions of the autonomic system?
sympathetic nervous system
parasympathetic nervous system
(both are smooth muscle, cardiac muscle, exocrine glands and some endocrine)
enteric nervous system (digestive organs)
2 major cell types in nervous system
glia and neurons
describe glial cells
not electrically excitable!
important for development and support, homeostasis of extracellular fluid around neurons and synapses, and helps with electrical insolation (forms myelin sheaths)
more abundant than neurons, ~90% of NS
describe neurons
fundamental, electrically excitable cells (signal via APs)
make up only 10% of NS
structurally and functionally distinct
carry out electrical and chemical communication
5 main types of vertebrate glial cells
ependymal cells
astrocytes
microglia
oligodendrocytes
schwann cells
ependymal cells
line fluid filled cavities of CNS, which circulate cerebrospinal fluid
astrocytes
transport nutrients, remove debris in CNS, regulate neurotransmitter levels around synapse.
*in PNS, neurotransmitter levels are controlled by satellite cells
microglia
neuronal maintenance, remove debris and dead cells from CNS
oligodendrocytes
forms myelin on neurons of CNS to increase electrical insulation and increase electrical conduction speed. one oligodendrocytes may wrap around the axon of several neurons
schwann cells
deposit myelin on motor and sensory neurons of PNS
increase electrical conduction speed along the axon
what do oligodendrocytes and schwann cells do for their respective neurons?
they reduce electrical/ion lead across the membrane, increasing AP signal transmission
draw the different kinds of neurons on slide 20!
most important:
purkinje cell
motor neuron
retinal neuron
olfactory neuron
efferent and afferent sensory neurons
interneurons
how do 3 functional classes of neurons differ in structure?
draw them from slide 20!
efferent neurons look like the typical neurons with their cell body and dendrite position
interneurons are all cell body and dendrites
afferent/sensory neurons are p much all axon, cell body off to the side
4 functional zones of the vertebrate neuron
signal reception
signal integration
signal conduction
signal transmission
Draw it! (Slide 21)
what structure is responsible for signal reception?
dendrites and cell body
what structure is responsible for signal integration ?
axon hillock
what structure is responsible for signal conduction?
axon
what structure is responsible for signal transmission?
axon terminals
explain membrane potential
all animal cells maintain a voltage difference across their cell membranes. this voltage difference is the membrane potential.
explain voltage difference
a source of potential energy for the cell, 2 functions:
- provide energy for membrane transport
- change in membrane potential is used by cells in cell-to-cell signalling
what can excitable cells do with their cell permeability?
they can alter cell permeability to generate changes in membrane potentials over time
what is the difference between non-excitable and excitable cells?
excitable cells have the ability to significantly change their electrical activity and propagate a signal.
explain the electrical properties of neuron membrane
cell membranes have varying degrees of permeability to different ions with varying concentrations across the membrane.
which ions are most influential on membrane potential? why?
K+
Na+
Cl-
they move readily across the cell membrane and have differences in extra/intracellular concentrations
what is the function of the sodium potassium pump?
running on ATP, it maintains Na+ and K+ gradients across the membrane
explain chemical gradient
concentration gradient for an ion across the plasma membrane
describe electrical gradient
created by attraction between opposite charges (+/-) or repulsion between like charges (+/+ or -/-)
describe electrochemical gradient
form of potential energy determined by the combination of an ion’s chemical and electrical gradients
describe equilibrium potential
membrane potential at which an ion’s electrical and chemical gradients are in balance. No net movement of ions across the membrane.
what sort of signal is in the cell body?
chemical