The Nervous System Flashcards
Function of the nervous system and the endocrine system (ductless glands)
The coordination of activities in the body in response to changes in the environment
quickest means of communication within the body
the nervous system
2 parts of the human nervous system
Central nervous system
Peripheral nervous system
Central nervous system
brain and spinal cord
Peripheral nervous system
Consists of cranial nerves and spinal nerves not in the central nervous system
function of PNS
these neurons carry impulses to and from the CNS
Recetors
sensory cells or sense organs that receive and respons to different stimuli
some stimuli
chemical (smell and taste) thermal electrical mechanical (touch, sound, stretching) osmotic light
2 places where receptors can be found
on the surface pf the body eg for touch
deep inside the body eg osmotic receptors for brain
effectors
tissues or organs that respond to a stimulus and carry out some action eg. muscles or glands
neuron
nerve cell
what are neurons capable of?
carrying electrical impulses
electrical impulses
provide a means of communication between receptors and effectors
what link the receptors to the effectors
neurons
3 types of motor neurons found in vertebrates
motor, sensory and interneurons
motor neurons
carry impulses from the CNS to the effectors
sensory neurons
carry impulses to the CNS from the receptors
Interneurons
carry impulses within the CNS, connect sensory and motor neurons
what does the cell body contain
nucleus, cytoplasm and other organelles
2 functions of the cell body
produces neurotransmitter chemicals
controls the passage of impulses
dendrites
short, branching fibres that pick up and carry impulses to the cell body
Axon
a long fibre that carries impulses away from the cell body along the neuron or carries impulses to the effector
function of schwann cells
produce the myelin sheath
myelin sheath
white fatty layer around the axon
2 functions of the myeline sheath
protect the axon
speed up the transmission of the impulse along the axon
Nodes of Ranvier
gaps in the myelin sheath where the axon is uncovered
function of the nodes of ranvier
speed up the transfer of impulses along the neuron
neurotransmitter swellings
swellings found at the end of the axon
function of neurotransmitter swellings
have vesicles that store neurotransmitter chemicals (released to carry an impulse from one neuron to another)
carriage of impulses in motor neurons
from the CNS to the effector organ
carriage of impulses in sensory neurons
to the CNS from the receptors
cell body in motor neurons
at one end of the axon
cell body in sensory neurons
somewhere along the neuron
vague location of cell body in motor neurons
inside the CNS
vague location of cell body in sensory neurons
outside the CNS in a ganglion
most cranial and spinal nerves
mixed nerves, contain both sensory and motor neurons
size of neurons
neurons in the brain are very small
those in the PNS connecting the spine to the foot may be over 1m long
when does a nerve transmit an impulse?
when it is stimulated strongly enough
what is an impulse?
an electrical current that travels along the neuron from the dendrites to the neurotransmitter swellings
what does the transmission of electrical impulses involve
the movement of ions across the membrane of the neuron
do impulses require energy
yes
where to the impulses get their energy
ATP
3 main ions
sodium (Na+), potassium (K+) and chloride (Cl-)
threshold intensity
minimum strength of stimulus needed for a nerve impulse to be transmitted
what type of response is a stimulus
an all-or-nothing response
below threshold
no impulse at all
speed and strength of different impulses
all the same speed and strength
can a nerve impulse be stopped?
no
what speeds up the rate of impulse transmission
the myelin sheath
refractory period
short delay of a few milliseconds between the transmission of impulses
can impulses travel in different directions?
no, one direction only
do neurons have protoplasmic connections between them?
no
what do neurons have in place of protoplasmic connections
a region called the synapse where neurons come into contact
synaptic cleft
each synapse’s tiny gap
what carries the impulses across the cleft?
neurotransmitters
3 examples of neurotransmitters
acetylcholine, serotonin, dopamine
where are neurotransmitters released from?
the neurotransmitter swellings
what occurs when an impulse arrives at the synapse
vesicles un the neuorotransmitter swellings release neurotransmitter into the synaptic cleft
what happens when the neurotransmitter has been released?
it diffuses across the synaptic cleft and generates an impulse in the next neuron
as soon as the neurotransmitter has worked?
it is broken down by an enzyme
at the end what happens to the neurotransmitters?
some are transported back into the neurotransmitter swellings and are reused
2 functions of the synapse
controls only one direction of the impulse, can travel in one direction only along a given pathway
Impulse can be blocked or enhanced here by certain chemicals (pain and psych meds)
what does the CNS do?
forms a bridge between sensory and motor functions of the peripheral nervous systems
top of brain
meninges
under meninges
cerebrum
bottom back of brain
cerebellum
bottom front tiny part of brain
pituitary gland
above pituitary gland
hypothalamus
under cerebellum
medulla oblongata
is the CNS full?
no its hollow
what are the cavities of the brain and spinal cord filled with
cerebro-spinal fluid
cerebro-spinal fluid
fluid that is filtered from the blood
function of cerebro-spinal fluid 2
brings food, O2, etc. to nerve tissue
removes waste from the nerve tissue
protects the CNS as a shock absorber
what covers the CNS
3 protective membranes called the meninges
where is cerebro-spinal fluid found
between the 2 inner membranes
what encloses the CNS
the axial skeleton
what protects the brain?
the cranium
what protects the spinal cord?
the vertebral column
3 main parts of the brain
forebrain, midbrain and hindbrain
main part of the forebrain
cerebrum
largest part of the brain
cerebrum
what is the cerebrum divided into
left and right cerebral hemispheres
outer grey part of cerebrum
cerebral cortex
what is the cerebral cortex made up of?
cell bodies and dendrites
most complex part of the brain
cerebral cortex
inner white part of the cerebrum
medulla
what is the medulla composed of?
axons with myelin sheaths
functions of cerebrum
voluntary movements, personality, memory, learning, hearing, vision, speech and language, intelligence
part of the forebrain below the cerebrum
hypothalamus
where is the main site of homeostasis
hypothalamus
functions of hypothalamus
hunger, thirst, osmoregulation, regulation of body temperature
what is connected to the hypothalamus
the pituitary gland
is the pituitary gland part of the brain
no
what is the pituitary gland part of
the endocrine system
what part of the brain is the cerebellum part of `
hind brain
second largest part of the brain
the cerebellum
2 functions of the cerebellum
muscular co-ordination (movement, balance)
hand-eye co-ordination
what part of the brain is the medulla oblongata?
hindbrain
what does the medulla oblongata do
connects the brain to the spinal cord
functions of medulla oblongata
involuntary muscles (eg.intercostals), breathing swallowing salivation vomiting blood pressure
from where does the brain recieve impulses
from sensory organs of the body
what does the brain do as a result of sensory impulses
sends out impulses to the effectors and causes them to react
in its association centres and motor areas, what does the brain do?
it coordinates the various stimuli from several receptors before sending out impulses to the appropriate affectors
what stores information and why?
the forebrain, so that behaviour can be modified as a result of past experience (memory and learning)
to what is the spinal chord attached?
the medulla oblongata
2 components of the spinal chord
central core of grey matter
outer layer of white matter
grey matter
cell bodies and dendrites
white matter
axons with myeline sheaths
outside of spinal chord
membrane called the meninges
what pass between the vertebraun
pairs of spinal nerves
what attaches the nerve to the spinal cord
2 roots; the dorsal and the ventral
what are spinal nerves
mixed nerves
sensory neurons in spinal cord
enter the spinal cord via the dorsal root
motor neurons in the spinal cord
leave via the ventral root
2 functions of the spinal cord
spinal reflexes eg.stretches
transmits impulses to and from the brain
Reflex action
an automatic response to a stimulus that is not under conscious control
2 reflex actions
knee jerk
blinking
advantage of refelx actions
fast responses that protect the body from damage
structural basis of reflex action
the reflex arc
Mechanism of spinal reflex action:
first step
receptor cell is stimulated
Mechanism of spinal reflex action:
once receptor cell is stimulated
impulse moves along sensory neuron into spinal cord
Mechanism of spinal reflex action:
once the impulse has gotten to the spinal cord
impulse is passed to an interneuron in the spianl cord
Mechanism of spinal reflex action:
once impulse reaches interneuron
impulse moves along interneuron to a motor neuron
Mechanism of spinal reflex action:
once impulse has gotten to motor neuron
impulse moves out of the spinal cord along a motor neuron to the effector
Mechanism of spinal reflex action:
when impulse gets to effector
effector is stimulated and reacts
simple reflex actions
automatic and involuntary and do not involve the brain
2 simple reflex actions
withdrawal of hand after pricked with a pin
iris-pupil reflex
1 disorder of the nervous system
parkinson’s disease
cause of parkinson’s disease
not enough dopamine produced due to degeneration of part of the brain
symptoms of parkinson’s disease
hand tremor
rigid and stoops and walks with small shuffling steps
3 corrective measurements of parkinson’s disease
drug treatment
exercise
stem cells
exercise for parkinson’s disease
most important therapy used to strengthen all of the muscles
