Biopsychology Revision Notes
The Nervous System and The Endocrine System
The Nervous System:
• The nervous system is a specialised network of cells in the human body and is our
primary internal communication system.
• It is based on electrical and chemical signals whereas the endocrine system based on
hormones.
The nervous system has two main functions:
- To collect, process and respond to information in the environment.
- To co-ordinate the working of different organs and cells in the body.
The nervous system is divided into two subsystems:
- Central nervous system (CNS).
- Peripheral nervous system (PNS).
,The Central Nervous System (CNS):
• The CNS is made up of the brain and the spinal cord, the brain being the centre of all
conscious awareness.
• The brain's outer layer, the cerebral cortex, is only 3 mm thick.
• The brain is highly developed in humans and is what distinguishes our higher mental
functions from those of other animals.
• The brain is divided into two hemispheres.
• The spinal cord is an extension of the brain. It passes messages to and from the
brain and connects nerves to the PNS. It is also responsible for reflex actions.
The Peripheral Nervous System (PNS):
• The PNS transmits messages, via millions of neurons, to and from the CNS.
The PNS is subdivided into the:
- Autonomic nervous system (ANS) governs vital functions in the body such as
breathing, heart rate, digestion, sexual arousal and stress responses.
- Somatic nervous system (SNS) governs muscle movement and receives
information from sensory receptors.
,The Endocrine System:
Glands and Hormones:
• The endocrine system works alongside the nervous system to control vital functions
in the body.
• It acts more slowly than the nervous system but has very widespread and powerful
effects.
• Various glands in the body, such as the thyroid gland produce hormones.
• Hormones are secreted into the bloodstream and affect any cell in the body that has
a receptor for that particular hormone.
• Most hormones affect cells in more than one body organ, leading to many diverse
and powerful responses.
• E.g. The thyroid gland produces the hormone thyroxine. This hormone affects cells in
the heart (increases heart rate). It also affects cells throughout the body increasing
metabolic rates (the chemical processes taking place in the cells). This in turn affects
growth rates.
• The key endocrine gland is the pituitary gland, located in the brain. It is often called
the ‘master gland’ because it controls the release of hormones from all the other
endocrine glands in the body.
, Endocrine and ANS Working Together: Fight or Flight:
• The endocrine system and the ANS work in parallel with one another, for instance
during a stressful event.
• When a stressor is perceived the first thing that happens is a part of the brain called
the hypothalamus activates the pituitary gland and this triggers activity in the
sympathetic branch of the ANS.
• The ANS changes from its normal resting state (the parasympathetic state) to the
physiologically aroused sympathetic state.
Adrenaline
• The stress hormone adrenaline is released from the adrenal medulla into the
bloodstream.
• Adrenaline triggers physiological changes in the body (e.g. increased heart rate)
which creates the physiological arousal necessary for the fight or flight response.
Immediate and Automatic
• All of this happens in an instant as soon as the threat is detected.
• This is an acute response and an automatic reaction in the body.
Parasympathetic Action
• Finally, once the threat has passed, the parasympathetic nervous system returns the
body to its resting state.
• The parasympathetic branch of the ANS works in opposition to the sympathetic
nervous system.
• The parasympathetic system acts as a ‘brake’ and reduces the activities of the body
that were increased by the actions of the sympathetic branch. This is sometimes
referred to as the ‘rest and digest response’.
The Nervous System and The Endocrine System
The Nervous System:
• The nervous system is a specialised network of cells in the human body and is our
primary internal communication system.
• It is based on electrical and chemical signals whereas the endocrine system based on
hormones.
The nervous system has two main functions:
- To collect, process and respond to information in the environment.
- To co-ordinate the working of different organs and cells in the body.
The nervous system is divided into two subsystems:
- Central nervous system (CNS).
- Peripheral nervous system (PNS).
,The Central Nervous System (CNS):
• The CNS is made up of the brain and the spinal cord, the brain being the centre of all
conscious awareness.
• The brain's outer layer, the cerebral cortex, is only 3 mm thick.
• The brain is highly developed in humans and is what distinguishes our higher mental
functions from those of other animals.
• The brain is divided into two hemispheres.
• The spinal cord is an extension of the brain. It passes messages to and from the
brain and connects nerves to the PNS. It is also responsible for reflex actions.
The Peripheral Nervous System (PNS):
• The PNS transmits messages, via millions of neurons, to and from the CNS.
The PNS is subdivided into the:
- Autonomic nervous system (ANS) governs vital functions in the body such as
breathing, heart rate, digestion, sexual arousal and stress responses.
- Somatic nervous system (SNS) governs muscle movement and receives
information from sensory receptors.
,The Endocrine System:
Glands and Hormones:
• The endocrine system works alongside the nervous system to control vital functions
in the body.
• It acts more slowly than the nervous system but has very widespread and powerful
effects.
• Various glands in the body, such as the thyroid gland produce hormones.
• Hormones are secreted into the bloodstream and affect any cell in the body that has
a receptor for that particular hormone.
• Most hormones affect cells in more than one body organ, leading to many diverse
and powerful responses.
• E.g. The thyroid gland produces the hormone thyroxine. This hormone affects cells in
the heart (increases heart rate). It also affects cells throughout the body increasing
metabolic rates (the chemical processes taking place in the cells). This in turn affects
growth rates.
• The key endocrine gland is the pituitary gland, located in the brain. It is often called
the ‘master gland’ because it controls the release of hormones from all the other
endocrine glands in the body.
, Endocrine and ANS Working Together: Fight or Flight:
• The endocrine system and the ANS work in parallel with one another, for instance
during a stressful event.
• When a stressor is perceived the first thing that happens is a part of the brain called
the hypothalamus activates the pituitary gland and this triggers activity in the
sympathetic branch of the ANS.
• The ANS changes from its normal resting state (the parasympathetic state) to the
physiologically aroused sympathetic state.
Adrenaline
• The stress hormone adrenaline is released from the adrenal medulla into the
bloodstream.
• Adrenaline triggers physiological changes in the body (e.g. increased heart rate)
which creates the physiological arousal necessary for the fight or flight response.
Immediate and Automatic
• All of this happens in an instant as soon as the threat is detected.
• This is an acute response and an automatic reaction in the body.
Parasympathetic Action
• Finally, once the threat has passed, the parasympathetic nervous system returns the
body to its resting state.
• The parasympathetic branch of the ANS works in opposition to the sympathetic
nervous system.
• The parasympathetic system acts as a ‘brake’ and reduces the activities of the body
that were increased by the actions of the sympathetic branch. This is sometimes
referred to as the ‘rest and digest response’.
