Nervous System Functioning Flashcards
Divisions of nervous system
Central Nervous System and Peripheral Nervous system,
Parts of CNS
Brain and spinal cord
PNS branches
Somatic and Autonomic nervous system
Subparts of the Autonomic nervous system
Sympathetic and parasympathetic nervous system
Functions of CNS
communicates with the body by conveying messages to the PNS
processes interprets and stores information
issues orders to muscles, glands, organs
The brain
an intricate network of cells that plays a vital role in processing information received through neural pathways from the body and in directing actions within the body
Spinal cord upper/lower function
upper- communication with brain and upper parts of body
lower- communication between the brain and lower parts of the body
spinal cord functions
receive sensory information from the body and send these messages to the brain for processing
receive motor information from the brain and send it to relevant parts of the body( via PNS)- control muscle, organs and glands
spinal cord comprises of
white and grey matter
white- axons that run length of spinal cord uninterrupted and bundled together
grey- cell bodies, together with axons and dendrites, located near centre of spinal cord
what are interconnected axons in CNS called
tracts, circuits or pathways
Differentiate ascending/descending tracts
ascending tracts- somatosensory information, comes in from parts of body, through spinal nerves to brain
descending tracts- motor information, leaves brain travels down spinal cord and exit via spinal nerves to muscles, organs, glands
PNS function
sends messages to CNS via sensory neurons
carries out messages from CNS via motor neurons
transfer information from sensory organs to CNS, then convey info from CNS to muscles, organs and glands
distinguish afferent/efferent pathways
afferent- ascending, sensory tracts
efferent- descending, motor tracts
Somatic nervous system
controls our conscious voluntary responses
functions incontinuously
why is SNS called skeletal
has both a sensory and motor function
functions of SNS
transmits messages from sensory receptors to CNS
controls the voluntary movement of skeletal muscles through CNS messages
ANS
directs our unconscious/involuntary functioning
ANS function
keep homeostasis in body
autonomic=self governing, operate usually independently from the brain
controls visceral muscles( internal organs and glands muscles)
sympathetic nervous system functions
increases visceral muscle activity
mobilises body internal resources
prepares for vigorous action in times of stress/emergency
sends message to adrenal gland to release adrenaline and noradrenaline
body changes of sympathetic
dilate pupils/inhibit tears inhibits salivation increases heart rate, vasodilation/blood pressure increase increase respiration rate/bronchi dilate inhibits digestion sweat glands increase production of sweat release adrenaline releases sugar/glucose relaxes bladder/intestine inhibition of food intake gall bladder inhibits bile release
parasympathetic NS
calms bodily activity, conserves energy and returns internal system to homeostasis (balanced level of activity)
decreasing visceral muscle activity
reverse symp effects- dominates symp in relaxed times
why does it take longer to return body to homeostasis than arousal
lingering hormones such as adrenaline in blood
body changes of paraysympathetic
constricts pupils/stimulate tears stimulates salivation heart rate/blood pressure decrease decrease respiration/bronchi constrict decrease glucose release from liver inhibit liver hormone secretion stimulates digestion contracts bladder and intestines decrease production of sweat stimulates bile release from gall bladder
conscious responses to stimuli
reaction involving awareness paid attention to stimulus voluntary reaction often goal directed more complex can be learnt/controlled vary
unconscious responses to stimuli
reaction not involving awareness dont have to pay attention involuntary reflexive/automatic- increases survival chance most simple responses no learning may not control it tend to occur in same way each time
spinal reflex
unconscious, involuntary and automatically occurring response to certain stimuli without brain involvement
- spinal cord reacts to message directly before it is carried to the brain- automatically reflected from the spinal cord without initial brain input
- enables faster reaction time, fraction of second before sensory info reaches brain
- adaptive response- saves times in dangerous/harmful situation
two forms of reflex arc
monosynaptic/polysnaptic reflex
monosynaptic
only one synapse- effector neuron brings sensation from receptors and effector neurons carry motor messages to muscles of body
-knee jerk
polysynaptic
involving interneurons connecting affector and effector neurons, at least two synapses
spinal reflex script
When (persons name, action), his sensory receptors in his her (body part) are stimulated. This stimulation causes a signal to be sent up an ascending tract via afferent sensory neurons towards the integrating centre in his spinal cord. At the integrating centre, the signal synapses on to an interneuron which sends the signal down a descending tract via efferent motor neurons back towards (persons name) muscles in (body part). When the signal reaches (body part muscles), it causes them to unconsciously contract, thus (persons name) instinctively pulls away from (stimulus). This reflexive action happens a fraction of a second before the signal is sent to the brain to process memory and feel pain.
neuron
an individual nerve cell that is specialised to receive, process and transmit information
communicate with themselves and muscles and glands
three types of neurons
sensory, motor and interneurons
sensory/motor found in the nervous system, interneurons only in CNS
dendrites
an extension of a neuron that detects and receives information from other neurons, by providing a site with receptors
axon
single tube like extension that transmits neural information to other neurons or muscles/glands
carries info from soma to axon terminal
myelin sheath
white fatty substance that surrounds and insulates the axon
allows efficient, uninterrupted, rapid transmission of electrical impulses
not continuous along axon, separated by nodes of ranvier- increases transmission
what disease results from a lack of myelin sheath
multiple sclerosis
axon terminals
small terminals at the end of collaterals, which contains small like knob-like swelling at its tip- terminal button
terminal button
small structure like a sac that stores and secretes neurotransmitters manufactured by neuron
synapse
junction between two neurons- site where communication occurs between adjacent neurons
composition of synapse
synaptic gap
terminal button-pre synaptic neuron
dendrites- post synaptic neurons
sensory neurons
carry messages from sensory organs through neurons in PNS up to spinal cord to brain
-receive internal and external sensory information- afferent neurons that carry somatosensory information
interneurons
enable connections between sensory and motor neurons
only exist in CNS-most numerous neuron type
motor neurons
carry messages away from CNS down efferent pathways to muscles, organs and glands
why are somatosensory/motor cortices close
adaptive evolutionary brain feature
neurotransmitters
chemical substances produced by a neuron that carry a message to other neurons or cells in muscles, organs
role of neurotransmitters
bind to specific receptor sites on dendrites of post synaptic neuron
any that don’t bind get reabsobred into pre synaptic terminal buttons- reuptake
two effects of neurons
excitatory- stimulates/activates postsynaptic neurons to perform functions
inhibitory- block or prevent postsynaptic neurons from firing
most common neurotransmitters
GABA and glutamate
Glutamate
primary excitatory neurotransmitter of CNS-second most abundant
enhances transmission by increasing postsynaptic neuron chances to fire
associated with learning and memory
too high- over excitation and neuronal death
GABA
primary inhibitory neurotransmitter in CNS
maintain neurotransmission at optimal level
counterbalances activity of glutamate and vice versa
low levels- anxiety, epilepsy, seizures, phobias
dopamine
facilitates movement, attention and learning
creates positive feelings of pleasure
excessive- schizophrenia
serotonin
regulate mood and controls behaviour
abnormal levels- depression
acetylcholine
- memory formation
- low levels- Alzheimers
difference between neurohormones and neurotransmitters
-neurotransmitters- secrete into synaptic gap
-faster transmission- shorter response
neurohormones- secrete into capillaries and bloodstream
-slower travel, more intense response
lock and key script
Each neurotransmitter has a chemically-distinct structure. When a neurotransmitter is released from axon terminal of pre-synaptic neuron, it searches for a receptor on the post-synaptic neuron’s dendrites, that has a complimentary shape. Like a lock and key, the neurotransmitter(key) released from pre-synaptic axon terminals, must have the exact shape to bind to the receptor (lock) on post synaptic dendrites. Furthermore,, like a lock and key, when the neurotransmitter binds to the post-synaptic dendritic receptors, it unlocks the effect of the neurotransmitter, which will either have an inhibitory effect, causing the post synaptic neuron to have a less chance of firing an action potential, or to have an excitatory effect, giving the post synaptic neuron a greater chance of firing an action potential.
agonist and antagonistic molecules
agonist- fills receptor site, and activates it, acts like neurotransmitter
antagonist- fills the receptor so neurotransmitter cant bind and activate the receptor
Parkinsons disease
symptoms caused by the degneration of dopamine releasing neurons in the substantial niagra
substantial niagra part of basal ganglia, located in the midbrain-responsible most importantly for movement coordination
dopamine needed to control messages as they pass between neurons in substantial niagra and stratum (balance and movement control)
-without enough dopamine- striatum fires uncontrollably
-primary motor cortex, cant execute voluntary movement due to inadequate info due to insufficient dopamine
symptoms of parkinsons
only occur when 80 percent drop in dopamine, plus 50 percent drop in substantial niagra neurons motor- tremors muscle rigidity bradykinesia postural instability non motor -ansomia-loss of smell -increased sensitivity to temperatures fatigue unrelieved by resting cognitive function impairment mental health- confusion, anxiety
causes of parkinsons
idiopathic- not having no known cause
risk factor is age
genetics- protein mutations havebeen linked to disease of blocking disposal of abnormal cells
environmental factors- pesticide rotenone
MPTP- contaminant in stress drugs
diet- vitamin B
GABA contribution to parkinsons
GABA decreases in parkinsons sufferers- causing restless leg syndrome
GABA could block dopamine effects
use L-DOPA, binds with GABA receptors and mimics GABA- agonist
treatment
no cure
motor symptoms can be relieved by medications that restore dopamine by increasing dopamine level
two types- mimic action of Dopamine- effectively stimulate reception of Dopamine
-converted into Dopamine by neurons
Deep brain stimulation is also a treatment
