new one Flashcards
The two roles of the human nervous system
To collect, process and respond to information in the environment
to co-ordinate the working of different organs and cells in the body
the two subsystems of the nervous system
peripheral nervous system
central nervous system
The divisions of the peripheral nervous system
autonomic nervous system
somatic nervous system
The autonomic nervous system function
governs all vital functions in the body such as breathing, heart rate, digestion, sexual arousal and stress responses
Split into the sympathetic nervous system and the parasympathetic nervous system
The parts of the central nervous system
The brain: centre of all conscious awareness, the outer layer is called the cerebral cortex and is divided into two hemispheres
The spinal cord: an extension of the brain, responsible for reflex actions
The peripheral nervous system
sends information to the CNS from the outside world and transmits messages from the CNS to muscles and glands
The central nervous system
is the origin of all complex commands and decisions
The endocrine system
One of the body’s major information systems that instructs glands to release hormones directly into the bloodstream, these hormones are carried towards target organs in the body
Gland
An organ in the body that synthesises substances such as hormones
Hormones
chemical substances that circulate in the bloodstream and only affect target organs, they are produces in large quantities but disappear quickly
The pituitary gland
The main endocrine gland, often called the master gland because it controls the release of hormones from all other endocrine glands in the body
Fight or Flight response
- when a stressor is perceived the hypothalamus triggers activity in the sympathetic branch of the autonomic nervous system
- The ANS changes from its normal resting state (the parasympathetic state) to the physiologically aroused sympathetic state
- The stress hormone adrenaline is released into the bloodstream - adrenaline triggers physiological changes in the body e.g. increased heart rate, necessary for the response
- once the threat has passed the parasympathetic nervous system returns the body to its resting state, it acts as a break and reduces the activities of the body that were increased by the actions of the sympathetic branch, sometimes referred to as the rest and digest response
sympathetic state
- increases heart rate
- increases breathing rate
- dilates pupils
- inhibits saliva production
- contracts rectum
Parasympathetic state
- decreases heart rate
- decreases breathing rate
- contracts pupils
- stimulates digestion
- stimulates saliva production
- relaxes rectum
The structure of a neuron
- Vary in size from less than a millimeter to up to a meter long
- the cell body (or soma), dendrites, axon, myelin sheath, nodes of Ranvier and terminal buttons
Cell body (soma) of a neuron
includes a nucleus, which contains the genetic material of the cell
Dendrites
branch-like structures that protude from the neuron cell body
Axon
carries the impulses away from the cell body
Myelin sheath
fatty layer that protects the axon and speeds up chemical transmission
Nodes of Ranvier
where the myelin sheath is segmented to maintain the speed of chemical transmission
Terminal buttons
Communicate between neurons
electric transmission - firing of a neuron
- when a neuron is in a resting state the inside of the cell is negatively charged compared to the outside
- when a neuron is activated by a stimulus, the inside of the cell becomes positively charged for a split second causing an action potential to occur
- this creates an electrical impulse that travels down the axon towards the end of the neuron
types of neuron
motor neurons, sensory neurons and relay neurons
neural networks
Groups of neurons communicating with each other