model 3 Flashcards
how does the nervous system maintain homeostasis
Sensory function- receives sensory input.
Integrative function-analyses and interprets sensory input, determines appropriate responses, generates the motor output that causes the response.
Motor function- issues motor output to activate an effector to bring about a response.
whats Thermoreceptors-
detect temperature stimuli
whats noicreceptors
detect painful stimuli
whats Mechanoreceptors
tactile receptors, detect tough, pressure and vibration
- baroreceptors, detect changes in blood pressure
- propioceptors, detect changes in body position eg arms and legs
where are thermoreceptors, noicreceptors and mechanoreceptors located
kin, muscles, tendons, joints and visceral organs.
whats photoreceptors
detect light (vision)
whats chemoreceptors
detect chemicals in solution (taste and smell)
whats mechanoreceptors
called hair cell receptors in the ear- detect hearing and balance stimuli
where are photoreceptors, chemoreceptors and mechanorecptors found
eyes, ears, mouth and nose
what does the central nervous system do
Performs integrative function of the nervous system:
analyses/interprets sensory input
Determines appropriate responses
Generates motor output
Controls emotions, behaviours and personality
Performs intellectual functions
Stores memories
what nervous does the peripheral nervous system include
- cranial nerves, brain and branch to form the structures of the head, neck, Thorax and abdomen. Eg
- spinal nerves- extend from spinal cord branch to form peripheral nerves blow the head.
what does the PNS consist of
consists of sensory receptors and the cranial, spinal and peripheral nerves that link body to CNS.
what can the peripheral nervous system be divided into
sensory division and motor division
whats the sensory division
conveys sensory input from receptors to the CNS.
whats the motor division
conveys motor output from the CNS to a muscle or gland
what can the motor division be divided into
autonomic nervous system
somatic nervous system
whats the somatic nervous system
-conveys somatic motor output from CNS to skeletal muscles.
-includes voluntary skeletal muscle movements (consious)
controls somatic reflex which is involuntary
whats the autonomic nervous system
- autonomic motor output to the body glands, cardiac and smooth muscles.
- controls involuntary (automatic) activities.
what can the autonomic nervous system be divided into
sympathetic divison
parasympathetic divison
whats the sympathetic division
- prepares body for action
- controls flight/fight/freeze response
- increased heart rate, dilated pupils, inhibits digestive functions(salivation) and inhibits urinates.
whats the parasympathetic division
- controls rest and digest activities, conserves energy
- stimuliates digestion, decreases heart rat, constricts pupils
what does neural tissue of two main types of cells
- neuroglia
- neurons
whats neuroglia
(nerve glue) support neuron development and function
6 different types: collectivity nourish, protect, insulate and structurally support neurons
example of neuroglia inPNS
schwan cells
example of neuroglia in CNS
ependymal cells
oligodendrocytes
whats neurons
generate action potentials and grade potentially to conduct sensory or motor information to another part of the body.
Require oxygen and glucose for survival
Unable to divide and replace themselves especially in CNS
function of dendrites
main receptive region of a neutron, convert information into an electrical signal called graded potential (electrical signal) carries info to soma.
function of soma
contains nucleus and organelles, integration region in a neuron, analyses information and conveys outgoing information.
whats nuclei
culsters of cell bodies and their dendrites form integration enters in the CNS.
whats ganglia
clusters of cell bodies in the PNS
function axon
conducting region, generates action potential to carry information from cell body to axon terminals.
whats nerves
bundles of axon bound together by a membrane in PNS
whats tracts
bundles of axon bound together by a membrane in CNS
function myelin sheath
increases speed of signal conduction, segments between the gaps are called nodes of ranvier. Destruction= multiple sclerosis.
function of axon terminals
release neurotransmitters into the shapes that carry information from a neuron to another cell eg a neuron, muscle, gland
what can neutrons be structurally classified as
multipolar
bipolar
unipolar
whats a multipolar neutron
common in CNS and PNS (has many dendrites)
whats bipolar neuron
rare, has dendrites either end (special sense organs) (found in eyes and ears)
whats unipolar neuron
common in PNS
how can neutrons be functionally classified
sensory neurons
internerons
motor neurons
whats a sensory neuron
are unipolar in structure
- dendrites are sensory receptors
- call body located in ganglion
- axon located in nerve.
whats interneuron
mainly multipolar in structure
- cell body located in uncles
- axon located in a tract.
what motor neuron
lower motor neurone conduct somatic motor output
- preganglionic and postganglionic neutrons conduct autonomic motor output
- mainly multipolar in structure
- cell body located in nucleus
- axon located in a nerve
whats the charge of the external and internal surface of a plasma membrane
External surface=positive charge
-Internal surface=negative charge
whats membrane potential
The potential energy separating these charges between positive and negative
when do changes in the membrane potential occur
- ions(sodium and potassium) flow through specific ion channels across the plasma membrane.
- membrane potential changes
- a neuron generate electrical signals
or a resting neuron to generate an electrical signal their plasma membrane must:
- Exhibit a resting membrane potential
- contain ion channels which allow specific ions to diffuse down the concentration gradient.
whats types of ion channels
Leakage channels-always open
Gated channels-open and close in repose to a specific stimulus, large number of ions released.
whats types of gated channels
chemically gated channels
mechanically gated channels
voltage gated channels
whats chemically gated channels
- open in response to a chemical stimulus binds to it eg. Neurotransmitter and pain
located on dendrites
whats mechanically gated channels
- open in response to mechanical stimulation eg. Touch, vibration and pressure.
- located on dendrites.
whats voltage gated channels
- open and close in response to voltage changes eg. Changes in membrane potential
- located on axon and axon terminals
whats depolarisation
a decrease in the membrane potential eg membrane potential becomes less negative. Moves from -70 towards 0.
- if influx of sodium ions into the ICF (gains more positive charged ions)
- interior becomes less negative therefore membrane potential becomes less negative.
whats hyperpolarisation
an increasing membrane potential eg. The membrane potential becomes more negative. Mores from -70 towards -100
- if efflux of potassium ions out of ICF. (loses more positive changed ions)
- interior becomes more negative therefore membrane potential becomes more negative.
whats a graded potential
- short distance electric signals or short lived
- originate in dendrites, when a stimulus opens chemically-gated or mechanically-gated channels.
- small changes in the membrane potential (small depolarisation or hyperpolaristation)
if a stimulus is strong enough, a graded potential can
- travel from the dendrites to the region of the axon initial segment.
- depolarise the membrane potential at initial segment to -55 mV=threshold
- stimulate voltage-gated sodium channels open
- generate an action potential
whats action potentials
- normal way neurones send signals over a long distance
- long distance electrical signals
- originate at initial segment of an axon when voltage-gated channels open
- changes in membrane potential are always the same regardless of stimulus strength
- self propagating-once initiated, a wave of action potentials will travel along the entire axon to the axon terminals.
- if threshold isn’t reached then no action potential will be made.
generation of action potential steps
- Resting state- all gated sodium and potassium channels are closed. Only leakage channels are open
- Depolarisation- sodium channels open, which opens more and more, axon interior(membrane potential) becomes less negative. Eg. -70 to +30
- Repolaristation- sodium channels are inactivating and potassium channels open, axon interior returns for +30 to -70.
- Hyperpolarization- membrane potential becomes more negative. Eg. -70 to-90
sodium postasium ATPase and leakage channels make membrane potential return back to -70, - resting state- now ready to fire another action potential.
whats the two modes of propogation of action potential
continuous conduction
saltatory conduction
whats continuous conduction
occurs in unmyelinated axons, a wave of action potentials are generated at the voltage gated channels along the length of the axon, conduction occurs at speeds. Very slow conduction.
whats saltatory conduction
- occurs in myelinated axons
- fast mode conduction.
- action potential only generated along node of ranvier therefore jumps down the neuron.
factors that impair the generation or propogation of an action potential
Local aesthetics stop pain sensations by blocking voltage gated sod channels.
-no action potentials=no conduction of pain signals=no sensation of pain
Cold and pressure reduce pain sensations by impairing signal conduction. Pain signals conducted at a slower rate.
steps that occur at chemical synapse
Action potential arrives at and depolarises axon terminal
Depolarisation of axon terminal stimulates voltage-gated calcium channels to open and claim enter the axon terminal
Calcium entry triggers synaptic vesicles to releases stored neurotransmitters into the the synaptic cleft.
Neurotransmitter diffuses across the synaptic cleft and binds to chemically gated ion channels(receptors) on the postsynaptic membrane.
Binding of neurotransmitter opens chemically gated ion channels, influx of sodium ions into ICF, plasma membrane of dendrites depolarises, graded potential known as excitatory potential is produced.
Excitatory potential depolarises initial segment to threshold voltage gated sodium channels open= action potential generated.
how is a neurotranmitter removed from cleft after information is transferred
Neurotransmitter diffuses away from the synaptic cleft.
The neurotransmitter is degraded by enzymes present in the synaptic cleft
The neurotransmitter reenters the axon terms and destroyed by enzymes or reused. Process known as reuptake.
what does a unipolar neurone look like
cell body in middle with both ends having dendrites
