Module 3 - Topic 1-2: The Nervous System Flashcards
functions of nervous tissue
acquire and transmit sensory information
process information
activate an appropriate response
Central Nervous System
processing and control of information
brain and spinal cord
Peripheral Nervous System
nervous tissue outside CNS
consists of nerves carrying information to and from CNS
Afferent
sensory - division of peripheral nervous system
carrying information from body to CNS
Efferent
motor - division of peripheral nervous system
carrying information away from CNS towards effector organs
Somatic
division of efferent
voluntarily and form synapses with skeletal system
Autonomic
division of efferent
involuntarily
send efferent signals from brain to smooth muscle, cardiac muscle and glands
Sympathetic
division of autonomic
fight or flight
activate target organs
Parasympathetic
division of autonomic
contentment, relaxation, digestion
inactivate target organs
Ganglia
collection of nerve cell bodies
lie outside the CNS
play important role in autonomic system
nervous tissue
consists of 2 types of cells
neuronal cells
glial cells
Neuronal cells
transmit signals throughout nervous system
electrical currents which pass from one end of cell to the other
how neuronal cells communicate
synapses
neurotransmitters
transmission of information across synapse, mediated by the release of chemical meesengers
Neuron makeup
soma
several dendrites
axon
soma
basic metabolic part of the nerve cell
dendrites
extension of cell that receives information
axon
transmits info away from cell body
Glial cells
dont transmit info but instead support the survival and function of other neuronal cells
Neuroglia
outnumber neurons 10 to 1
makeup 50% of brain mass
Astrocytes
create cohesion of central nervous tissue
hold things together and maintain structural relationships
Oligodendrocytes
form myelin
Ependymal cells
epithelial lining for cavaties
small amounts of cerebrospinal fluid is formed by secretion
Microglia
migrate into nerve tissue from blood stream
protective immune function
Satellite cells
formed in peripheral ganglia and supports the cell bodies
Schwann cells
PNS, involved in peripheral myelin formation and the formation of neurilemma
Myelin
phospholipid produced when plasma membrane becomes wrapped around axon of neuronal cell
myelin sheath gaps
have lots of gaps that speed up nerve impulse conduction
membrane potential
voltage that exists across plasma membrane
voltage
difference in electrical charge
major molecules responsible for membrane potential
sodium and potassium
sodium potassium pump
removes 3 sodium ions and replaces with 2 potassium ions
Plasma membrane - potassium
more permeable to potassium so there is an unequal exchange of positively charged ions
unequal charge
inside has a less positive state than outside
resting neuron potential
negative
-70mv
depolarisation
decrease in membrane potential, less negative
Repolarisation
return of cell to its resting potential
Chemically gated channel
opens in response to chemicals binding to receptors
Voltage gated channels
open in response to change in membrane potential
Initial Change
takes place when a nerve is activated
Action potential
when a receptor potential is strong enough to reach a region, trigger zone, action potential is generated
trigger zone - location
generally located in neuron near start of axon
Action potential - size
large
cause all or nothing changes in membrane potential
action potential - gating
voltage gated and only open if threshold change in membrane potential is reached
Repolarisation phase - action potential
eventual closing of voltage gated Na+ channels and opening of voltage gated K+ channels, allowing membrane potential to return to resting state
Myelin - purpose
increases rate at which action potential travels down axon by insulating selected portions of the axon
Action potential - location
generated at the gaps within nerve sheath
Myelin fibres
much faster
Non myelin fibres
much slower
CNS function
process sensory info and generate appropiate responses
White matter
mostly nerve fibres (axons) and appear white due to myelin
Grey matter
nerve cell bodies, no myelin present
Brain matter makeup
outer - grey
middle - white
inner - grey
Spinal cord matter makeup
outer- white
inner - grey
Cerebrospinal fluid
CNS floats in watery nutrient rich bath
produced by specialised clusters of tissue
Choroid plexuses
specialised clusters of tissue that make CFS and hang from roof of ventricles
knot of porous blood capillaries surrounded by ependymal cells
ependymal cells
process the filtrate passing and aid in formation of blood brain barrier
CSF
protects brain from injury
nourishes brain and removes wastes
carries hormones
constant motion of CSF
aided by movement of long cilia of ependymal cells lining ventricles
Meninges
three covering layers of connective tissue
dura mater
arachnoid matter
pia matter
Dura Matter
hard tough outermost covering connected to the inside of the skull
Arachnoid matter
middle covering, spider like
Pia Matter
tender, thin innermost covering attached to brain
sub arachnoid space
wide space between arachnoid and pia membranes where CSF flows
Hydrocephalus
when fluid accumulates and exerts pressure on brain
Brain subdivisions
left and right cerebral hemisphere
diencephalon
Brain stem
cerebellum
The left and right hemisphere
consist of outer cerebral cortex of grey matter
inner region of cerebral white matter
island of additional grey matter (basal nuclei)
Cerebral cortex
controls all activities of the body can be divided into lobes outer: grey middle: white matter inner: basal nuclei - grey
Frontal lobe
back of brain
consciousnesss and personality
primary motor region
Parietal lobe
at the side
Primary sensory region
every part mapped to different body part
temporal lobe
at temple
primary audio centre
occipital lobe
infront of eyes
primary vision region
cerebral cortex functional areas
sensory areas
motor
association
Sensory areas
percieves information
motor area
control of voluntary movement
association areas
integrate multiple pieces of info from various stimuli
commissural fibres
enables communication between left and right hemispheres
association fibres
enables communication with each hemisphere
projection fibres
links cortex to rest of NS
Basal nuclei
influences motor function
consists of caudate nuclei, putamen, globus pallidus
lentiform nucleus
putamen and globus pallidus
corpus striatum
caudate nucleus and lentiform nucleus
Diencephalon
2 lobed structure at middle brain on top of brain stem made of 3 components thalamus hypothalamus epithalamus
Thalamus
inner
relay station to higher cerbral cortex,
involved in memory processing
Hypothalamus
below
control centre of homeostasis
regulates many important functions
Epithalamus
back of diencephalon and contains pineal gland
pineal gland
secretes melatonin that controls sleep wake cycle and mood
Brain stem
critical to survival
contains specialised autonomic centres that controls heart rate, blood pressure, breathing
Brain stem - midbrain
top of stem - middle of brain
Brain stem -pons
bridge
Brain stem - medulla oblongata
lower part of stem
controls important functions
relay station of hypothalamus
Cerebellum
sits underneath cerebrum
coordinates motor activities
grey matter with thin branches of white matter
in charge of coordination
spinal cord - protection
protected by bone, coverings and CSF
spinal cord - function
two way conduction pathway
anterior tips of wing
ventral horns
arrangement of grey matter in spinal cord
butterfly shaped
posterior tips of wings
dorsal horns
lateral wings
to the side, located in thoracic and superior lumbar regions
Ventral horns
mainly somatic motor nerve cells with efferent fibres leaving the spinal cord via ventral root
Dorsal horns
somatic sensory nerve afferent fibres travelling from organs to CNS enter spinal cord
lateral horns
autonomic nerve cells which stimulate visceral organs
stimulate flight or fight `
outside spinal cord - ventral and dorsal
they fuse together to form on spinal nerve for each side of body
Ascending nerve fibres
carry sensory impulses towards higher centres
Descending nerve fibres
carry impulses from brain to lower parts
Traversing fibres
carry info from one side to the other
Gyrus
brain ridges
Sulcus
grooves in brain, folds back on itself to form grooves
Broca’s area
speaking (frontal)
Wernicke’s area
processing and comprehesion
temporal
Corpus Callosum
thick bundle of nerve fibres that hold brain hmispheres together
carries impulses and has many axonss
limbic system
emotional response
ring of structures
encircles the upper part of brain stem, corpus callosum and temporal lobes
Hippocampus
memory centre
olfactory bulbs and stalks
sense smell
Amygdala
instinctive behaviour and rage centre
response to pheromones
interneuron
link sensory and motor neuron that doesnt go through brain
