the nevous system Flashcards
what is the role of the endocrine system
it transmits chemical signals called hormones to receptive cells
are hormones generally slow or fast acting. can they affect more than one region throughout the body
relatively slow acting
they can affect one or more regions of the boy
name some of the simplest animals with nervous systems
hydras, jellies and other cnidarians
what features of an animal mean that it has a more specialised nervous system
elongated, bilaterally symmetrical bodies
what is cephalization
clustering of sensory neurons and interneurons at the anterior (front) end of the body. nerves that extend towards the posterior (rear) end enable these anterior neurons to communicate with cells elsewhere in the body
neurons that carry out integration form which type of nervous system
the central nervous system
neurons that carry information in and out of the CNS form what type of nervous system
the peripheral nervous system
what are ganglia
segmentally arranged clusters of neurons that act as relay points in transmitting information
what forms the CNS
the brain and the spinal chord
what forms the PNS
nerves (spinal nerves and cranial nerve) and ganglia
what are the two components of nervous tissue
neurons - transmit nerve impulses glia - nourish, insulate and replenish neurons
give an example of a glial cell and its function
schwann cells - produce myelin sheaths surrounding axons in the PNS and oligodendrocyte, their counterparts of the CNS
how are the simplest nervous systems arranged
in nerve nets (a series of interconnected neurons)
What does the PNS do
transmits information to and from the CNS
it regulates movement and the internal environment by nerves and glia
in the PNS ………… neurons transmit information to the CNS
afferent (sensory)
in the PNS ……….. neurons transmit information away form the CNS
efferent (motor/autonomic)
what are the 5 major glial cells in the nervous system
CNS - oligodendrocytes - astrocytes - microglia - ependymal cells PNS - schwann cells
during development, where does the central nervous system develop from
the dorsal nerve chord
the cavity of the dorsal nerve cord gives rise to the narrow………….. of the spinal cord and the ………. of the brain
central canal
ventricles
the canal and ventricles of the brain are filled with what
cerebrospinal fluid
how is cerebrospinal fluid made
in the brain by filtering arterial blood
what is the role of cerebrospinal fluid
it supplies the CNS with nutrients and hormones and carries away waste. it drains into the veins
what is a reflex
a rapid involuntary response to a particular stimulus
why are reflexes rapid
sensory information activates neurons without having to travel from the spinal cord to the brain and back
what are the 2 efferent components of the PNS
motor system and the autonomic nervous system
what do the neurons of the motor system do
carry signals to skeletal muscles
is motor control voluntary or involuntary
can be either
e.g. raising your hand is voluntary but the knee jerk reflex is controlled by the spinal chord
what do the neurons of the autonomic nervous system do
carry signals to smooth and cardiac muscle
is the autonomic nervous system voluntary or involuntary
involuntary
what are the 2 divisions of the autonomic nervous system
sympathetic and parasympathetic
what organ systems does the autonomic nervous system regulate
digestive, cardiovascular, excretory and endocrine
what is the enteric/intrinsic nervous system
network of neurons that exerts direct and partially independent control of the digestive tract, pancreas and gallbladder
what does activation of the sympathetic nervous system result in
arousal and energy generation e.g. the heart beats faster digestion is inhibited the liver converts glycogen to glucose adrenal medulla increases secretion of epinephrine
what does activation of the parasympathetic nervous system result in
promote calming and a return to self maintenance functions "rest and digest" e.g. heat rate decreases digestion id enhanced glycogen production increases
in which process does the parasympathetic nervous system complement the sympathetic nervous system rather than antagonizing it
regulation of reproductive activity
how do the parasympathetic and sympathetic nervous systems differ in organization and signals released
parasympathetic nerves exit the CNS at the base of the brain or the spinal cord and form synapses in ganglia near or within an internal organ
sympathetic nerves typically exit the CNS midway along the spinal cord and form synapses in ganglia located just outside the spinal cord
what are preganglionic neurons
they release acetyl choline as a neurotransmitter
what are postganglionic neurons
parasympathetic division - release acetyl choline
sympathetic division - release nor epinephrine
what is it that enables the sympathetic and parasympathetic divisions to bring about posit e effects in organs
the difference in neurotransmitters
what are the 3 major regions of the vertebrate brain
forebrain, midbrain and hindbrain
what are the components and function of the forebrain
olfactory bulb, cerebrum, thalamus and hypothalamus
functions - smell, regulation of sleep, learning ad any complex processing
what is the function of the midbrain
coordinates routing of sensory input
what are the components and function of the hindbrain
cerebellum function - controls involuntary activities, such as blood circulation and coordinates motor activities such as locomotion
which part of the brain generally increases in size with evolution of the brain
the cerebrum (forebrain)
what is the role of the cerebrum
controls skeletal muscle contraction and is the centre for emotion, learning, memory and perception
what is the outer layer of the cerebrum called and what are its functions
cerebral cortex
function - perception, voluntary movement and learning
left side controls the right side of the body and voice versa
what does the cerebellum coordinate
coordinates movement and balance and helps in learning and remembering motor skills
generation and experience of emotions involve the brain structures grouped as what system
the limbic (reward) system - contains the amygdala, olfactory bulb, nucleus accumbens hippocampus and parts of the thalamus
what is the function of the amygdala
storage and recall of emotional memory
what are the 4 lobes of the cerebral cortex
frontal
parietal
temporal
occipital
what are the functions of the frontal lobe of the cerebral cortex
decision making, planning, control of skeletal muscles, forming speech
what are the functions of the parietal lobe of the cerebral cortex
sense of touch, integration of sensory information
what are the functions of the occipital lobe of the cerebral cortex
processing visual stimuli and pattern recognition, combining images and object recognition
what are the functions of the temporal lobe of the cerebral cortex
hearing
what are neurons
nerve cells that transfer information within the body
most of a neurons organelles, including its nucleus are located where
in the cell body
the cells body of a neuron is studded with dendrites. what are dendrites
highly branched extensions that receive signals form other neurons
as neuron has a single axon. what is an axon
an extension that transmits signal to other cells
which is longer, axons or dendrites
axons
e.g. those that reach from the spinal cord in the giraffe to the muscle cells in its feet
the junction at the end of the axon that branches to the receiving cell is called what
the synapse
the part of the axon branch that forms the synapse is called what
synaptic terminal
what are neurotransmitters
chemical messengers
what do neurotransmitters do
pass information from the transmitting neuron to the receiving cell
in describing a synapse what is the transmitting neuron referred to as
presynaptic cell
in describing a synapse what is the receiving cell (neuron, muscle gland cell etc) referred to as
post synaptic cell
what are neuron supporting cells called
glia
what are the 3 stages of information processing by a nervous system
sensory input, integration ad motor output
what are sensory neurons
transmit information about external stimuli e.g. light, touch or smell
or internal conditions such as blood pressure or muscle tension
what are interneurons
they form the local circuits connecting neurons in the brain or ganglia
they are responsible for integration (analysis and interpretation) of sensory input
what are motor neurons
they transmit signals to muscle cells, causing them to contract
what happens at the synapse
the electrical signal is converted into a chemical signal
what is resting potential
the membrane potential characteristic of a non conducting excitable cell, with the inside of the cell more negative than the outside - imbalance in charge
what is action potential
an electrical signal that propagates (travels) along the membrane of a neuron or other excitable cell as a non graded (all-or-one) depolarization.
what is the membrane potential
the voltage (difference in electrical charge) across the plasma membrane
in most neurons the concentration of ………….. is higher inside the cell and the concentration of ………… is higher outside the cell
potassium
sodium
what maintains the sodium and potassium gradient of a neuron
the sodium potassium pump
how does the sodium potassium pump maintain the ion gradient
3 sodium ions bind pump hydrolyses ATP phosphorylation conformation change sodium ions released 2 potassium ions bind dephosphorylation conformation change potassium ions released cycle repeats
how many potassium ions are pumped into the cell
2
how many sodium ions are pumped out of the cell
3
what is a gated channel
a channel that opens or closes in response to a stimulus
e.g. voltage change or ligand binding/unbinding
what is hyperpolarization
increase in the magnitude of the membrane potential, making the inside of the cell even more negative
what is depolarization
reduction in the magnitude of the membrane potential the inside of the cell gets less negative
if hyperpolarization or depolarization only causes a shift in the membrane potential what is this known as
graded potential - they decay with time and distance from their source
action potential
if a depolarization shifts the membrane potential sufficiently the result is a massive change in membrane voltage
how are action potentials different to graded potentials
action potentials have a constant magnitude and can regenerate in adjacent regions of the membrane
action potentials can therefore spread along axons, making them well suited for transmitting
if a depolarization increases the membrane potential to a level called ………… the voltage gated sodium channels open
threshold
describe the steps in generation of action potential
1: the gated sodium and potassium channels are closed. ungated channels maintain the resting potential
2: a stimulus opens some sodium channels. Sodium inflow depolarizes the membrane
3: depolarization opens most sodium channels while the potassium channels remain closed. sodium influx makes the inside of the membrane positive with respect to the outside
4: most sodium channels become inactivated blocking sodium inflow. most potassium channels open permitting potassium outflow which makes the inside of the cell negative again
5: the sodium channels close but some potassium channels are still open. as these potassium channels close and the sodium channels become unblocked (though still closed) the membrane returns to its resting state.
what are the 5 steps in generation of action potential
resting state depolarisation rising phase of the action potential falling phase of the action potential undershoot
describe the resting state in generation of an action potential
the membrane of the axon is a at resting potential most voltage gated channels are closed. some potassium channels are open
describe depolarization in generation of an action potential
a stimulus (neurotransmitter) depolarizes the membrane. sodium channels open allowing an influx of sodium into the cell. if the stimulus is sufficiently strong to reach the threshold then sodium inflow persists causing further depolarisation this opens more gated sodium channels allowing even more sodium influx
describe the rising phase of the action potential
once the threshold is crossed, the positive feedback cycle rapidly increases the membrane potential
describe the falling phase of the action potential
voltage gated sodium channels inactivate stopping the influx into the cell
voltage gated potassium channels open causing rapid outflow of potassium
this rapidly decreases the membrane potential
describe the undershoot
the membrane’s permeability to potassium is higher than at rest
gated potassium channels close
membrane returns to resting potential
what is the refractory period
the downtime when a second action potential cannot be initiated due to inactivation of sodium gated channels at the end of the previous action potential cycle
is the magnitude and duration of the action potential the same along the entire axon
yes - because an action potential is an all or none event
where does a nerve impulse start and finish
cell body (axon hillock) synaptic terminal
why don’t action potentials ever travel back towards the cell body
the area behind the travelling zone of depolarization has its sodium channels inactivated and is in the refractory period so can’t respond to further input
the rate of action potential production is proportional to what
signal strength
a wide axon provides ……… resistance to the current associated with action potential
less
vertebrates have narrow axons but are insulated which increases the rate of action potential. what is the layer of insulation called
myelin sheath
what are myelin sheaths produced by
glia:
oligodendrocytes in the CNS
Schwann cells in the PNS
the myelin sheaths are mainly made from lipids which are poor conductor, so good insulators
which disease is caused by destruction of myelin sheaths
multiple sclerosis
what are the gaps in the myelin sheath called
nodes of ranvier - voltage gated sodium channels are restricted to these
what is saltatory conduction
rapid transmission of a nerve impulse resulting from action potential jumping from one node of ranvier to another, skipping the myelin sheathed regions of the membrane
what carries information across a synapse
neurotransmitters
Near the synapse the action potential activates voltage-gated…………… channels
calcium channels
calcium ions enter through the membrane and cause what
synaptic vesicles to fuse with the synaptic membrane releasing the neurotransmitters