1. nervous and endocrine system

nervous system definition

• consists of the central nervous system and the peripheral nervous system

• communicated using electrical and chemical signals

main functions of the nervous system

1. to collect, process and respond to information in the environment

2. to coordinate the working of different organs and cells in the body

CNS definition

consists of the brain and spinal cord, and is the origin of all complex commands and decisions

CNS and the brain

• brain is the centre of all conscious awareness

• outer layer (cerebral cortex) is 3mm thick and covers the brain - only found in mammals

• brain is highly developed in humans - it is what distinguished our higher mental functions from those of other animals (only a few living creatures eg sponges, sea squirts and jellyfish don’t have a brain)

• brain is divided into two hemispheres

functions of the brain

• regulating body temp, heart rate and breating

• language (production and comprehension)

• coordinating movement

• problem solving and planning

CNS and the spinal cord

• the spinal cord is an extension of the brain

• passes messages to and from the brain and connects nerves to the PNS

• responsible for reflex actions eg pulling your hand away from a hot plate

PNS definition

sends information to the CNS from the outside world, and transmits messages from the CNS to muscles and glands in the body

• transmits messages throughout the whole body from the brain and relays messages back to the brain

subdivisions of the PNS

1. autonomic nervous system (ANS)

2. somatic nervous system (SNS)

ANS

• transmits information to and from internal bodily organs

• autonomic as the system operates involuntarily

• governs vital functions eg breathing and heart rate

ANS divisions

• has 2 main divisions

  1. sympathetic nervous system

  2. parasympathetic nervous system

SNS

• transmits and receives messages from the senses (apart from sight) ie taste info from the tongue

• governs muscle movements - directs muscles to move appropriately

• responsible for the relflex arc - although autonomic, it still involves the use of muscle movement

endocrine system definition

• instructs glands to release hormones directly into the bloodstream

• these hormones are carried towards target organs in the body

• communicates via chemicals

• slower than the nervous system

how do hormones work

1. glands produce hormones

2. they are secreted into the bloodstream

3. affect any cell in the body that has a receptor for that particular hormone

thyroid gland

• produces thyroxine

• affects cells in the heart by increasing heart rate

• affects cells throughout the body increasing metabolic rates - in turn affects growth rates

diagram of glands

pituitary gland

• located in the brain

• often called the master gland

• controls the release of hormones from all the other endocrine glands in the body

gland definition

an organ in the body that synthesises substances such as hormones

hormones definition

• chemical substances that circulate in the bloodstream and only affect target organs

• produced in very large quantities but disappear quickly

• their effects are powerful

what systems can work in parallel together

endocrine and ANS - eg fight or flight

1. when a stressor is percieved the hypothalamus activates the pituitary gland

2. this triggers activity in the sympathetic branch of the ANS

3. the ANS changes from parasympathetic state to sympathetic state

4. adrenaline is released from the adrenal glands to fuel any physical activity required of the body along with other physiological changes

adrenal gland

• adrenaline is released from the adrenal medulla (part of the adrenal gland near kidneys) into the bloodstream

• triggers physiological changes in the body eg increased heart rate - creating the physiological arousal necessary for the fight or flight response

• has a strong effect on the cells of the cardiovascular system - stimulating heart rate, contracting blood vessels and dilating air passages

adrenal gland image

type of response from adrenaline

it is immediate and automatic

parasympathetic and sympathetic state examples

final stage of adrenaline

once the threat has passed, the PNS returns the body to its resting state

• it works in opposition to the SNS as its actions are antagonistic

• acts as a ‘brake’ 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