The Nervous System And The Endocrine System

What is the nervous system?

A specialised network of cells in the human body and is our primary internal communication system.

What are the two main functions of the nervous system?

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

2. To co-ordinate the working of different organs and cells in the body.

How does the nervous system communicate?

Through electrical signals

What is the nervous system divided into?

• Central nervous system.

• Peripheral nervous system.

What is the central nervous system?

It consists of the brain and the spinal chord and is the origin of all complex commands and decisions.

What is the central nervous system made up of?

• The brain.

• The spinal chord.

What is the role of the brain in the central nervous system?

The brain is the centre of all conscious awareness. The brain’s outer layer, the cerebral cortex, is only 3mm thick and covers the brain and is only found in mammals.

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.

What is the role of the spinal chord in the central nervous system?

The spinal chord is an extension of the brain. It passes messages to and from the brain and connects nerves to the PMS. It is also responsible for reflex actions.

What is the role of the peripheral nervous system?

The PNS sends information from receptor cells in the sense organs to the CNS from the outside world, and transmits messages from the CNS to muscles and glands in the body.

What is the peripheral nervous system made up of?

• The autonomous nervous system.

• The somatic nervous system.

What is the role of the autonomic nervous system?

The ANS transmits information to and from internal bodily organs, it operates involuntarily and has two main divisions.

What does the autonomic nervous system govern?

Vital functions in the body such as breathing, heart rate, digestion, sexual arousal and stress responses.

What are the two branches of the autonomic nervous system?

• Sympathetic nervous system.

• Parasympathetic nervous system.

What is the role of the sympathetic nervous system?

It gets the body ready for response, it’s the ‘fight or flight‘ system.

What is the role of the parasympathetic nervous system?

It calms the body down, its the ‘rest and digest‘ system.

What is the role of the somatic nervous system?

The SNS sends information from the receptor cells in the sense organs to the CNS. It also receives information from the CNS that directs the muscles to act.

What does the somatic nervous system govern?

Muscle movement and receives information from sensory receptors.

What is 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.

How does the endocrine system communicate?

Via chemicals.

What does the endocrine system work along, and what do these two systems do?

It works alongside the nervous system to control vital functions in the body.

Which communication system works faster?

The endocrine system acts more slowly than the nervous system, but has very widespread and powerful effects.

What is a gland?

An organ in the body that synthesises substances such as hormones.

What do various glands in the body do?

Produce hormones that are secreted into the bloodstream and affect any cell in the body that has a receptor for that particular hormone.

What are some examples of endocrine glands in the body?

• Pancreas - releases insulin and glucagon to regulate blood sugar levels.

• Gonads (ovaries and testes) - produce sex hormones.

• Thymus gland - regulates the immune system.

• Parathyroid glands - produce parathyroid hormone which controls the levels of minerals in the body.

What is a hormone?

A biochemical substance that circulates in the blood but only affects target organs. They are produced in large quantities but disappear quickly. their effects are very powerful.

How do most hormones affect cells?

In more than one body organ, leading to many diverse and powerful responses. For example, thyroxine, produced by the thyroid gland, affects cells in the heart increasing heart rate and also affects cells throughout the body increasing metabolic rates, which in turn may affect growth rates.

What is the key endocrine gland?

The pituitary gland, located in the brain. It controls the release of hormones from all the other endocrine glands in the body.

What is the fight or flight response?

The way an animal response when stressed. The body becomes physiologically aroused in readiness to fight an aggressor or in some cases, flee.

What system does the endocrine system usually work in parallel with?

The autonomous system.

When happens when a stressor is perceived?

The hypothalamus in the brain activates the pituitary gland, which triggers activity in the sympathetic branch of the autonomic nervous system.

What happens in a flight or fight response after activity is triggered in the sympathetic branch of the autonomic nervous system?

The autonomic nervous system changes from its normal resting state (parasympathetic state) to physiologically aroused sympathetic state.

What hormone is released from the adrenal medulla (a part of the adrenal gland)?

Adrenaline.

What is adrenaline?

A hormone produced by the adrenal gland.

What is the effect of adrenaline on the body?

It triggers psychological changes in the body such as increased heart rate, creating the physical arousal necessary for the fight or flight response.

What is the speed of the fight or flight response?

It happens in an instant as soon as the threat is detected. This is an actuate response and an automatic reaction in the body.

What are the physiological changes associated with the sympathetic (fight or flight) response?

• Increased heart rate - to get blood quickly to the areas it is needed.

• Increased breathing rate - more oxygen can be sent to the muscles.

• Dilated pupils - more light can enter the eye to allow for clearer vision.

• Inhibition of digestion - blood can be directed to the brain and muscles.

• inhibition of saliva production - as the digestive system is not needed, leads to dry mouth.

What happens once a threat has passed?

The parasympathetic nervous system returns the body to its resting state.

What does the parasympathetic branch of the ANS work in opposition to?

The sympathetic nervous system - its actions are antagonistic to the sympathetic system.

What does the parasympathetic branch do once the threat has passed?

It acts as a ‘brake‘ and reduces the activities of the body that were increased by the actions of the sympathetic branch - rest and digest response.

What are the physiological changes associated with the parasympathetic state?

• Decreased heart rate.

• Decreased breathing rate.

• Constricted pupils.

• Stimulation of digestion.

• Stimulation of saliva production.