Nervous System CH2

Peripheral Nervous System

Autonomic NS and Somatic NS

All the neurons in your body outside the CNS

Transmits neurons between CNS and the body

Carries messages to and from the CNS

MADE UP OF SENSORY NEURONS AND MOTOR NEURONS

Somatic Nervous system

Apart of the PNS

Carries messages from sensory receptors in body TO the CNS

And motor messages FROM the CNS to the skeletal muscles

skeletal muscles regulation that’s mostly voluntary

Has both sensory and motor neurons

RESPONSIBLE FOR REFLEX ARC

Autonomic nervous system

Regulates non skeletal muscles, internal organs and glands. (INTERNAL ENVIRONMENT)

Connects CNS to internal organs and glands, sends messages to CNS on the activity of the non skeletal muscles, internal organs/glands

doesnt have to be conscious

IS SELF REGULATING

has 3 subtypes: sympathetic NS, Parasympathetic NS, Enteric NS

Parasympathetic nervous system

Autonomic NS Subdivision

Calms body down after action

Controls body’s internal environment in an autonomous/ self regulated manner

Maintains homeostasis

Takes longer to activate in comparison to the sympathetic N.S as hormons such as adrenaline and cortisol can take time to fade away

Dominates normal activities that calm us - regulates our digestion, body temp, etc

Returns our body to calm state after a stressful/threatening situation

Dominates the ‘freeze’ response when the body is still/’stuck’

Sympathetic NS is still partially active in background to keep body alert just in case action is needed

Enteric nervous system

Autonomic NS Subdivision

Dedicated to the functioning of the gastrointestinal (digestive) tract

Consists of neurons lining the gastrointestinal (G.I) tract and controls digestive system

Largest Autonomic NS component, has 200-600 million neurons

90% of bodies serotonin in the digestive system

Controlled by the parasympathetic and sympathetic NS

Works independent from brain

Central nervous system

Brain and spinal cord

Carries messages to and from the PNS

MADE UP OF INTERNEURONS

Sympathetic N.S

Autonomic NS subdivision

‘S’ for STRESS

Prepares body for action

Activates visceral muscle organs, glands, etc to prepare body to respond to a perceived threat/stressor

Activated by hypothalamus when threat is perceived (physical or psychological)

Triggers fight or flight as a survival response (eg. faster heartbeat, pupils dilate, adrenaline and cortisol hormones released into blood stream, stop digestion to save energy, etc)

Brain

Responsible for virtually everything we think, feel and do

Coordinates mental processes and behaviours and regulates body

Controls activity of entire N.S EXCEPT FOR SPINAL REFLEX

Spinal cord and its 3 roles

cable of nerve tissues that extends from brain connecting it to PNS

1 Carry sensory info from PNS to CNS for processing

2 Carry motor info initiated from CNS towards the body PNS

3 Spinal reflex (involuntary and unconcious

S.A.M.E

S ensory

A fferent

M otor

E fferent

Afferent Neurons

Efferent Neurons

Motor

Nervous system

organised system for coordinating and directing the bodies actions

provides basis for conscious experience (perceptions, thoughts, feelings in mental life)

Complex combo of neurons

receives, processes, and coordinates info

CNS steps (3)

1 receives neural messages from senses (PNS)

includes internal and external sensations

2 After recieving the message it processes it and decides what to do with it

3 Intitiate a response

Can be involuntary/automatic/unconscious ORR voluntary/conscious commands

Enteric N.S Function (4)

1 controls digestion/gut movement and muscle gut contractions (moves food along)

2 releases acids and enzymes to break down food

3 aids in nutrient absorption

4 monitors what’s happening/the status of the gut

sensory neuron

motor neuron

interneuron

dendrites

receives neural messages

the very end of the neuron with the big circle

axon terminal

sends of neural messages

on one side of neuron - the one without big circle

axon

the line in the middle of the neuron

under the myelin

myelin

insulates neurons and prevents disturbance from other neurons

the yellow cubes things along the axon

neurons

enable communication of info around the body

do this by receiving, transmitting and processing info in the from of neuronal messages

sensory neurons

transmits/carry info from sensory receptors in skin and internal organs to CNS

Myelinated which allows faster transmission

Location in PNS

Interneuron

neuron that connects sensory input (brought via sensory neurons) with motor output (carried via motor neurons)

bridges sensory and motor neurons so they can connect

located in CNS

Motor neurons

transmits/carry neural messages about motor movement from the CNS to the body

myelinated

located in PNS, axons reach into the muscles

conscious response

deliberate and voluntary actions initiated by the brain

intentional

involves thinking, learning, decision making, etc

can be performed by body and therefor involes PNS and somatic NS

Unconscious response

automatic and involuntary actions performed without conscious awareness in response to internal and external sensory stimuli

eg. spinal reflexes, digestion, blinking, etc

Spinal reflex and its 4 steps

unconscious response to sensory stimulus that is initated by interneurons in the spinal cord INDEPENDENTLY of the brain so it can act fast to the danger

1 dangerous/harmful sensory stimulus is picked up by sensory receptors, which transmit this sensory message via sensory neurons in the somatic N.S to the spinal cord

2 Interneuron in spinal cord relays the danger stimulus message to a motor neuron initiating an automatic motor response

3 motor messages is transmitted via motor neurons in somatic NS to the skeletal muscles to carry out an unconscious motor response to the dangerous sensory stimulus (eg. such as moving away)

4 the original sensory message continues to travel via afferent pathway in spinal cord to brain so the brain finally recieves the dangerous sensory stimulus that triggered the spinal reflex

reflex arc

the path along which the neural signal is transmitted as part of the spinal reflex

neural transmission

an electrical impulse (‘action potential’) occurs when a neuron is activated

‘an fires’ (couldnt make out notes lmao)

neurotransmission

transfer of info between neurons

specifically the pre synaptic neuron and the post synaptic neuron

vesicles

lil sacks / hole like things in the neurons that hold neurotransmitters and neuromodulators

What triggers/activates neurons

neuron is stimulated by a sensory stimulus

Neural transmission process

neural impulse reaches the axon terminals of presynaptic neuron

causes the vesicles to release neurotransmitters into the synaptic gap

the neurotransmitters then bind to recpetor sites on the dendrites of the post synaptic gap

the neurotransmitters then makes the post synaptic neuron either more likely to fire (excitatory) or less (inhibitory)

neurochemicals

2 types: neurotransmitters and neuromodulaters

Neurotransmitter

When released can have an excitatory or inhibitory effect of post synaptic neuron

chemically produced and released by neurons to communicate across neurons via synapse

allows neurons to further communicate with muscles, glands, etc.

ONLY binds to receptor sites specific to the neurotransmitter. Neurotransmissions wont wonk if neuroransmitters dont bind to its recpetor.

Neuromodulators

subclass of neurotransmitters

modulate = modify/adjusting

alter the strength of neural transmission, by increasing or decreasing the responsiveness of neurons to neurotransmitter signals

when released they activate multiple far away receptor sites - therefor larger affect around brain

can go BEYOND the synapse to affect more

Bind to metabotrophic recpetors causing them to:

act more slowly

doesn’t directly cause excitation/inhibitory

influence MANY neurons (up to 100,000)

excitatory neurotransmitters

increase the likelihood that the post synaptic neuron will fire an action potential (by stimulating it)

inhibitory neurotransmitters

decreases the likelihood of post synaptic neuron firing an action potential/neural impulse

How: released by vesicles into synapse, binds to Post synaptic neuron recpetor sites

GABA

main inhibitory neurotransmitter in our nervous system

counterbalances glutamate and vice versa

Key role in preventing over excitation of neurons, a balance between both is ideal

Glutamate and what too much/too little means

Excitatory neurotransmitter

Main excitatory neurotransmitter in our nervous system

counterbalances GABA and vice versa

involved in memory and learning - allows synaptic connections to strengthen

Too much: over stimulation of neurons which can cause seizures, epilepsy and anxiety

Too little: reduced learning and memory, low cognitive, etc.

Serotonin

inhibitory neurotransmitter and neuromodulator

primarily responsible for mood and sleep regulation

90% made in gastrointentstinal tract, 10% made in brain

Dopamine

Neuromodulator

gives feelings of pleasure and satisfaction when u do smth enjoyable

function: memory, mood, motivation

apparently can be both excitatory and inhibitory

Synapse

gap between neurons where neurotransmission lowkey be happening

serotonin pathway

starts at brainstem (where 10% is produced)

travels and spreads widely throughout brain - influences large regions

modulates/adjusts brain activity

Synaptic plasticity and its 3 modifications

Specific (physical/structural) changes (strengthening/weakining) that occur within the synapse, between neurons, in response to activity or experience

Is about SPECIFIC CHANGES OCCURING WITHIN THE SYNAPSE BETWEEN NEURONS

is NOT neural plasticity where its abt the entire brain

mostly occurs through 3 modifications: sprouting and rerouting (LTP) and pruning (LTD)

Synaptic plasticity’s link to glutamate

When a neural pathway is activated during learning/memory formation, glutamate is released

glutamates excitatory so activity increases in that pathway

repeated activation = stronger connection

more a pathway is used = stronger it becomes

Neural Plasticity

2 important processes in neural and synaptic plasticity

Long term potentiation (LTP) and Long term depression (LTD)

Long term potentiation

Rerouting and Sprouting

relatively permanent

strengthening of synaptic connections as a result of repeated activation of a neural pathway

each time a pathway is activated, it will become stronger and easier

Long term depression

Pruning

Relatively permanent

weakening of synaptic connections as a result of repeated low-level activation

‘prunes’ neural connections that are no longer useful to make room for new pathways

How LTP and LTD work together

weakens and prunes useless pathways (LTD) + strengthens useful pathways (LTP) = more efficient neural pathways

Sprouting

LTP

Result of long term LTP process

Growth of dendrites (Post.S.N) or/and axon terminal branches (Pre.S.N) at the synapse

Process establishes connections to other neurons

Rerouting

LTP

Formation of new neural connections to establish alternative neural pathways

occurs when a damaged or less used neural pathway is replaced by a new one

Pruning

LTD

Removal of synaptic connections that are not frequently activated (eg. weak, ineffective, etc)

helps to increase the efficiency of neural transmission

‘pruning’ away those excess branches from sprouting