The nervous system and the endocrine system Flashcards
The nervous system
The nervous system consists of the central nervous system and peripheral nervous system. It communicates using electrical signals. It 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 central nervous system
The CNS is made up of the brain and the spinal cord.
The brain is the centre of all conscious awareness. The brain is divided into two hemispheres. There are many parts to the brain; some are concerned with vital functioning others are involved in higher thinking such as problem solving.
The spinal cord is an extension of the brain. It passes messages to and from the brain and connects nerves to the PNS. Responsible for reflex actions.
The peripheral nervous system
The PNS transmits messages via millions of neurons to and from the CNS.
The PNS is subdivided into the:
Autonomic nervous system – transfers info to and from internal organs to sustain life processes. Governs vital functions in the body. E.g. breathing, heart rate, digestion, sexual arousal, stress responses
ANS is further subdivided into the sympathetic nervous system and parasympathetic nervous system
Sympathetic NS – increases bodily activities
Parasympathetic NS – maintains or decreases bodily activities
Somatic nervous system – transmits info to and from senses and to and from CNS. Governs muscle movement and receives information from sensory receptors
The endocrine system
Endocrine system works alongside the nervous system to control vital functions in the body. Instructs glands to release hormones directly into the bloodstream and these hormones affect any cell in the body that has a receptor for that particular hormone. Endocrine system acts more slowly than the nervous system but has widespread and powerful effects. Communicates via chemicals.
The key endocrine gland is the pituitary gland, located in the brain. It controls the release of hormones from all other endocrine glands in the body.
Main endocrine glands
Hypothalamus
Pituitary
Thyroid
Parathyroid
Adrenals
Pancreas
Ovaries (female)
Testes (male)
Endocrine and ANS working together: fight or flight
When a stressor is perceived the hypothalamus activates the pituitary gland and this triggers activity in the sympathetic branch of the ANS. ANS changes from resting state to the physiologically aroused sympathetic state.
Adrenaline
stress hormone ‘adrenaline’ produced by the adrenal glands is released from the adrenal medulla into the bloodstream. Adrenaline triggers physiological changes in the body which creates physiological arousal needed for fight or flight response.
Immediate and automatic
this happens as soon as a threat is detected. This is an acute response and an automatic reaction.
Parasympathetic action
once the threat has passed, the parasympathetic NS returns the body to its resting rate. The parasympathetic branch’s actions are antagonistic to the sympathetic branch. Reduces the activities of the body that were increased by the actions of the sympathetic branch.
sympathetic state
increases heart rate
increases breathing rate
dilates pupils
inhibits digestion
inhibits saliva production
contracts rectum
parasympathetic state
decreases heart rate
decreases breathing rate
constricts pupils
stimulates digestion
stimulates saliva production
relaxes rectum
