PSYCHOLOGY UNIT THREE
The Nervous System
KDP 1: the roles of different divisions of the nervous systems (central and peripheral nervous systems and
their associated subdivisions) in responding to, and integrating and coordinating with, sensory stimuli
received by the body
The Human Nervous System
The main functions (RPC)
Essentially, it allows messages to be sent between the brain and the rest of the body
1. Receive information
2. Process information
3. Coordinate a response to the information
EXAMPLE:
1. the vibrating air molecules are received at the ear and sent to the brain via the auditory nerve.
2. The brain processes the auditory information and interprets the sound as your mobile phone’s
ringtone.
3. The brain then sends messages along nerve pathways to activate muscles to pick up the phone
Central Nervous System
Processes information received from the body’s internal and external environments, and activates
appropriate responses.
Division Function
The Brain The control center of all human behaviour
o Processes information received from neural pathways (tracts) from the
body and directs a response
Ø Neural pathways/tracts: comprise of one or more circuits of
interconnected neurons that from communication networks
The Spinal Cord o Long, thin bundle of nerve tissue that run from the base of the brain to the
lower back
o Has two main functions: transmit sensory and motor information between the
brain and body
, PSYCHOLOGY UNIT THREE
Ø Passes sensory information (through a sensory pathway/ascending
tract) from the PNS to Brain
Ø Passes motor information (through a motor pathway/descending tract)
from the Brain to PNS
o Damage to the spinal cord = paralysis: brain is unable to receive sensory
information and send motor information
o The higher up on the spine the damage occurs, the greater the number of
nerve connections between brain and body that are severed
o Also initiates simple involuntary motor reactions: spinal reflex – independently
from the brain. Occurs prior to the sensory information reaching the brain. It is
a survival mechanism.
o The linking ‘pipeline’ that integrates our central and peripheral nervous
systems
Peripheral Nervous System
Division Function
Peripheral nervous The entire network of nerves that transmits sensory and motor information to and
system from the central NS
o The PNS carries information to the CNS from the sensory organs and the
body’s muscles, organs and glands (MOG) through the afferent pathways
o Carries information from the CNS to the body’s muscles, organs and
glands through the efferent pathways
MOG à CNS à MOG
Somatic nervous A network of nerves that carry sensory information to the CNS and motor
system information from the CNS
o Voluntary
o Involved in all skeletal muscle activity – that enables us to participate in
our relationship with the external environment
Sensory information: is received from sensory receptor sites in the body (skin,
muscles, tendons, joints), and is carried via sensory neural pathways by sensory
neurons, from the spinal cord to the brain the afferent tract
Motor information: is sent from the brain to the skeletal muscles along a motor
neural pathway by motor neurons, to control their activity the efferent tract
EXAMPLE:
1. Sensory neurons carry (afferent) messages to the brain via the spinal cord
(interneurons), that the foot is itchy
2. Sensory information of the foot being itchy is received and processed by
the brain (interneurons) and a response is coordinated.
3. Motor (efferent) neurons carry the motor message received from the
brain and the spinal cord (interneurons) to skeletal muscles of the hand
and forearm to scratch the itch.
SAME: Sensory, afferent, motor and efferent
, PSYCHOLOGY UNIT THREE
Autonomic nervous A network of nerves that connects CNS to the body’s internal organs (heart, liver,
system stomach) and glands (salivary and adrenal), providing feedback to the brain about
its activities.
o Involuntary, unconscious
o Regulates the functioning of visceral muscles, internal organs and glands
o Called ‘autonomous’ because the processes under its control are self-
regulating and occur without conscious effort and not usually under our
voluntary control
Ø Heartbeat
Ø Breathing
Ø Digestion
Ø Perspiration
o However, it is not completely self-regulating – can choose to voluntarily
control some automatic responses
Sympathetic nervous Activates internal muscles, organs and glands to prepare body for vigorous activity
system or a stressful or threatening situation
o Increases bodily arousal by activating the fight (confront the threat), flight
or freeze (run away) response, in response to a perceived threat
o When you perceive an emergency, or experience a crisis, the sympathetic
system activates specific organs and glands to respond
o Once activated, the adrenal gland releases adrenaline to start a chain of
psychological changes
EXAMPLE: playing tennis vigorously
Ø Speeds up heart rate to pump more blood & oxygen to your muscles
Ø Cause liver to release sugar into bloodstream for energy
Ø Induces sweating to keep your skin cool and prevent you from overheating
Parasympathetic Helps maintain the internal body environment in a steady, balanced state of
nervous system normal functioning (restores equilibrium)
o Counterbalances the activities of the sympathetic nervous system
o It restores the body to a state of calm once the need for the sympathetic
nervous system activation has passed.
o Takes longer to return the body to its normal state – hormones released
during sympathetic NS remain in blood stream
o Parasympathetic NS usually dominates over the sympathetic NS – in
routine, everyday activity
MAIN FUNCTIONS
- responsible for maintaining optimal levels of functioning of the organs,
muscles and glands
- returns them to their balanced and ideal levels of functioning after the
heightened arousal of a sympathetic response.
EXAMPLE: playing tennis vigorously
o Slows down the heart rate
o Constricts the blood vessels in you muscle so the blood flow is diverted to
internal organs
, PSYCHOLOGY UNIT THREE
Activities of the sympathetic and parasympathetic nervous systems
Organs Function Sympathetic Parasympathetic
Pupil Regulates the amount of light Dilate (expand) Contracts
entering the eye
Salivary glands Digestion Decreases salivation Increases salivation
Heart Pumps blood Accelerates heart rate Slows heart rate
Lungs Breathing Dilate (expand) Contract
Gallbladder Stores bile Inhibits the release of Stimulates the release of
bile bile
Stomach Digestion Decreases contractions Increases contractions
Liver Produce bile to aid digestion. Increases the release of Decreases the release of
Maintains blood sugar levels glucose (energy) glucose
Adrenal glands Secretes hormones: adrenaline Stimulates hormone Inhibits hormone
(epinephrine), noradrenaline secretion resulting in secretion
(norepinephrine) increased heart rate,
blood pressure and
breathing rate and
relaxation of internal
muscles
Bladder Stores urine Relaxes Increases contractions
Intestines Digestion Relaxes Increases contractions
Genitals Reproduction Excite Relax
Sweat glands Regulate temperature Increase the production Decrease the production
of perspiration of perspiration
CONSCIOUS AND UNCONSCIOUS RESPONSES
KDP 2: the distinction between conscious and unconscious responses by the nervous system to sensory
stimuli, including the role of the spinal reflex
Conscious VS unconscious responses
Our brain and nervous system constantly process both internal and external sensory stimuli; responses to
these may be conscious or unconscious
CONSCIOUS RESPONSES
A conscious response to sensory stimuli is a reaction that involves awareness is voluntary, intentional and
goal directed (purposeful) and we can exercise conscious control over it
EXAMPLE:
o Internal sensory stimulus: choosing to eat food when your tummy has rumbled
o External sensory stimulus: When you walk outside and feel the air temperature you will make a
conscious response when you decide whether to put on a jacket
UNCONSCIOUS RESPONSES
Reaction that does not involve awareness is involuntary, unintentional, automatic and we can’t control it.
o E.g. ANS functioning (regulation of bodily functioning such as heartbeat and digestion) and reflexive
responsive blinking, spinal reflex or breathing (autonomic reflexes)
The Nervous System
KDP 1: the roles of different divisions of the nervous systems (central and peripheral nervous systems and
their associated subdivisions) in responding to, and integrating and coordinating with, sensory stimuli
received by the body
The Human Nervous System
The main functions (RPC)
Essentially, it allows messages to be sent between the brain and the rest of the body
1. Receive information
2. Process information
3. Coordinate a response to the information
EXAMPLE:
1. the vibrating air molecules are received at the ear and sent to the brain via the auditory nerve.
2. The brain processes the auditory information and interprets the sound as your mobile phone’s
ringtone.
3. The brain then sends messages along nerve pathways to activate muscles to pick up the phone
Central Nervous System
Processes information received from the body’s internal and external environments, and activates
appropriate responses.
Division Function
The Brain The control center of all human behaviour
o Processes information received from neural pathways (tracts) from the
body and directs a response
Ø Neural pathways/tracts: comprise of one or more circuits of
interconnected neurons that from communication networks
The Spinal Cord o Long, thin bundle of nerve tissue that run from the base of the brain to the
lower back
o Has two main functions: transmit sensory and motor information between the
brain and body
, PSYCHOLOGY UNIT THREE
Ø Passes sensory information (through a sensory pathway/ascending
tract) from the PNS to Brain
Ø Passes motor information (through a motor pathway/descending tract)
from the Brain to PNS
o Damage to the spinal cord = paralysis: brain is unable to receive sensory
information and send motor information
o The higher up on the spine the damage occurs, the greater the number of
nerve connections between brain and body that are severed
o Also initiates simple involuntary motor reactions: spinal reflex – independently
from the brain. Occurs prior to the sensory information reaching the brain. It is
a survival mechanism.
o The linking ‘pipeline’ that integrates our central and peripheral nervous
systems
Peripheral Nervous System
Division Function
Peripheral nervous The entire network of nerves that transmits sensory and motor information to and
system from the central NS
o The PNS carries information to the CNS from the sensory organs and the
body’s muscles, organs and glands (MOG) through the afferent pathways
o Carries information from the CNS to the body’s muscles, organs and
glands through the efferent pathways
MOG à CNS à MOG
Somatic nervous A network of nerves that carry sensory information to the CNS and motor
system information from the CNS
o Voluntary
o Involved in all skeletal muscle activity – that enables us to participate in
our relationship with the external environment
Sensory information: is received from sensory receptor sites in the body (skin,
muscles, tendons, joints), and is carried via sensory neural pathways by sensory
neurons, from the spinal cord to the brain the afferent tract
Motor information: is sent from the brain to the skeletal muscles along a motor
neural pathway by motor neurons, to control their activity the efferent tract
EXAMPLE:
1. Sensory neurons carry (afferent) messages to the brain via the spinal cord
(interneurons), that the foot is itchy
2. Sensory information of the foot being itchy is received and processed by
the brain (interneurons) and a response is coordinated.
3. Motor (efferent) neurons carry the motor message received from the
brain and the spinal cord (interneurons) to skeletal muscles of the hand
and forearm to scratch the itch.
SAME: Sensory, afferent, motor and efferent
, PSYCHOLOGY UNIT THREE
Autonomic nervous A network of nerves that connects CNS to the body’s internal organs (heart, liver,
system stomach) and glands (salivary and adrenal), providing feedback to the brain about
its activities.
o Involuntary, unconscious
o Regulates the functioning of visceral muscles, internal organs and glands
o Called ‘autonomous’ because the processes under its control are self-
regulating and occur without conscious effort and not usually under our
voluntary control
Ø Heartbeat
Ø Breathing
Ø Digestion
Ø Perspiration
o However, it is not completely self-regulating – can choose to voluntarily
control some automatic responses
Sympathetic nervous Activates internal muscles, organs and glands to prepare body for vigorous activity
system or a stressful or threatening situation
o Increases bodily arousal by activating the fight (confront the threat), flight
or freeze (run away) response, in response to a perceived threat
o When you perceive an emergency, or experience a crisis, the sympathetic
system activates specific organs and glands to respond
o Once activated, the adrenal gland releases adrenaline to start a chain of
psychological changes
EXAMPLE: playing tennis vigorously
Ø Speeds up heart rate to pump more blood & oxygen to your muscles
Ø Cause liver to release sugar into bloodstream for energy
Ø Induces sweating to keep your skin cool and prevent you from overheating
Parasympathetic Helps maintain the internal body environment in a steady, balanced state of
nervous system normal functioning (restores equilibrium)
o Counterbalances the activities of the sympathetic nervous system
o It restores the body to a state of calm once the need for the sympathetic
nervous system activation has passed.
o Takes longer to return the body to its normal state – hormones released
during sympathetic NS remain in blood stream
o Parasympathetic NS usually dominates over the sympathetic NS – in
routine, everyday activity
MAIN FUNCTIONS
- responsible for maintaining optimal levels of functioning of the organs,
muscles and glands
- returns them to their balanced and ideal levels of functioning after the
heightened arousal of a sympathetic response.
EXAMPLE: playing tennis vigorously
o Slows down the heart rate
o Constricts the blood vessels in you muscle so the blood flow is diverted to
internal organs
, PSYCHOLOGY UNIT THREE
Activities of the sympathetic and parasympathetic nervous systems
Organs Function Sympathetic Parasympathetic
Pupil Regulates the amount of light Dilate (expand) Contracts
entering the eye
Salivary glands Digestion Decreases salivation Increases salivation
Heart Pumps blood Accelerates heart rate Slows heart rate
Lungs Breathing Dilate (expand) Contract
Gallbladder Stores bile Inhibits the release of Stimulates the release of
bile bile
Stomach Digestion Decreases contractions Increases contractions
Liver Produce bile to aid digestion. Increases the release of Decreases the release of
Maintains blood sugar levels glucose (energy) glucose
Adrenal glands Secretes hormones: adrenaline Stimulates hormone Inhibits hormone
(epinephrine), noradrenaline secretion resulting in secretion
(norepinephrine) increased heart rate,
blood pressure and
breathing rate and
relaxation of internal
muscles
Bladder Stores urine Relaxes Increases contractions
Intestines Digestion Relaxes Increases contractions
Genitals Reproduction Excite Relax
Sweat glands Regulate temperature Increase the production Decrease the production
of perspiration of perspiration
CONSCIOUS AND UNCONSCIOUS RESPONSES
KDP 2: the distinction between conscious and unconscious responses by the nervous system to sensory
stimuli, including the role of the spinal reflex
Conscious VS unconscious responses
Our brain and nervous system constantly process both internal and external sensory stimuli; responses to
these may be conscious or unconscious
CONSCIOUS RESPONSES
A conscious response to sensory stimuli is a reaction that involves awareness is voluntary, intentional and
goal directed (purposeful) and we can exercise conscious control over it
EXAMPLE:
o Internal sensory stimulus: choosing to eat food when your tummy has rumbled
o External sensory stimulus: When you walk outside and feel the air temperature you will make a
conscious response when you decide whether to put on a jacket
UNCONSCIOUS RESPONSES
Reaction that does not involve awareness is involuntary, unintentional, automatic and we can’t control it.
o E.g. ANS functioning (regulation of bodily functioning such as heartbeat and digestion) and reflexive
responsive blinking, spinal reflex or breathing (autonomic reflexes)
