Nervous and Hormonal Control

The cells in our body don’t work independently, they communicate with other cells all throughout your body. There are two lines of communication around your body that we are going to discuss: The Nervous system and the endocrine system.

Imagine that the Nervous system is like a phone call between your brain and your muscles/organs (fast, immediate communication), and the Endocrine system is like an email conversation (slow, takes a bit more time for signals to get from A to B).

Nervous System
The nervous system has many functions. It allows sensation, movement, sight, hearing and coordination.
The nervous system is made up of the central nervous system and the peripheral nervous system. The central nervous system (**CNS**) is made up of the brain and spinal cord. The peripheral nervous system is made up of peripheral nerves (all nerves outside of the CNS).
This little image breaks up our nervous systems.

Neurones
The cells of the nervous system are called **neurones**. These cells allow extremely rapid communication between cells via electrical impulses.
Receptors pick up signals at the end of neutrons. These signals are called neurotransmitters. These neurotransmitters travel across little gaps between neurones called synapses.
There are three types of neurones that you need to be aware of at National 5 level:
Sensory neurones - These detect changes, like when you touch something you “sense” it, thanks to your sensory neurones.
Inter neurones - these link between sensory and motor neurones, like passing the baton in a relay race
Motor neurones - These are neurones that allow movement, they stimulate muscle to move.

Brain Structure
You need to be aware of three structures in the brain and their jobs:
The Cerebrum is the large, wrinkly part of the brain in charge of conscious thought, memory, emotions, movement, and processing sensory information.
The Cerebellum refines fine movement and controls your balance and coordination.
The medulla is part of the brainstem and controls unconscious actions like regulating heart rate, breathing and peristalsis.

Reflexes
Reflex arc is a defence mechanism.
When you touch something hot, or cut your hand on something, your body automatically pulls you hand away from the source of pain. This is a reflex, meaning an automatic response to something without conscious thought.
You have these reflexes due to reflex arcs. These reflex arcs are a path of neurones from sensory neurones -> interneurones (in spinal cord) -> motor neurones. It doesn’t even travel to the brain because that would take too long.

Endocrine System
Hormones are chemical messengers. They travel in the bloodstream to receptors on target cells in the body.
Think of a receptor as a post-box for messages. Imagine you are sending a letter to your friend. You send a letter and the postman delivers it and pops it in your friends post box. Your friend can then read your letter and think of a response. In this scenario, you are an organ of the endocrine system, which sends a message through the blood (postman) to the receptor (letterbox) of a target organ.
The pancreas is an endocrine organ which sends signals throughout the body to control your blood sugar.

High Blood Glucose Control
The pancreas is an endocrine organ which sends signals throughout the body to control your blood sugar.
Blood glucose regulation is very important, as glucose (sugar) provides us with energy. Too little glucose in your blood can be dangerous, making you sluggish, shaky, and feeling faint. Too much blood glucose can also be very dangerous, however this really only occurs when you have an issue regulating blood glucose.
If a high amount of blood glucose is detected (for example just after a meal), your pancreas detects this glucose and releases insulin (a hormone). This insulin travels in the blood to your liver. Your liver then converts glucose to glycogen, which reduces blood glucose.
High blood glucose -> pancreas detects this and releases insulin -> insulin travels in blood to liver -> liver converts glucose to glycogen -> blood glucose is reduced.

Low Blood Glucose Control
If there is a low amount of blood glucose detected (like if you haven’t eaten all day), your pancreas detects this and releases glucagon (a hormone). This glucagon travels in the blood to your liver. Your liver then converts glycogen to glucose, which increases blood glucose.
Low blood glucose -> pancreas detects this and releases glucagon -> glucagon travels in blood to liver -> liver converts glycogen to glucose -> blood glucose is raised.
Diabetes is a common and well-known condition where there is an issue with blood glucose regulation.
Type 1 diabetes, more commonly occurring in young people, happens when there is an abnormal immune response to your pancreas cells that make insulin. This makes blood glucose control difficult, and so people with type 1 diabetes then need to monitor their blood glucose and take insulin injections daily.
Type 2 diabetes, more commonly occurring in older people, happens when there is an issue with producing enough insulin, or there is a low insulin response.

Key Points!

Nervous System

The nervous system has many functions. It allows sensation, movement, sight, hearing, coordination.
The nervous system is made up of the central nervous system and the peripheral nervous system. The central nervous system (CNS) is made up of the brain and spinal cord. The peripheral nervous system is made up of peripheral nerves (all nerves outside of the CNS).
Neurones

The cells of the nervous system are called neurones. These cells allow extremely rapid communication between cells via electrical impulses.
Sensory neurones - These detect changes, like when you touch something you “sense” it, thanks to your sensory neurones.
Inter neurones - these link between sensory and motor neurones, like passing the baton in a relay race
Motor neurones - These are neurones that allow movement, they stimulate muscle to move.
Brain Structure

Cerebrum - controls conscious thought, emotions, memory
Cerebellum - balance and coordination
Medulla - control of unconscious actions like regulating heart rate and refining movement.
Reflexes

You have these reflexes due to reflex arcs. These reflex arcs are a path of neurones from sensory neurones -> interneurones (in spinal cord) -> motor neurones. It doesn’t even travel to the brain because that would take too long.
Endocrine System

Hormones are chemical messengers. They travel in the bloodstream to receptors on target cells in the body.
Blood Glucose Control

High blood glucose -> pancreas detects this and releases insulin -> insulin travels in blood to liver -> liver converts glucose to glycogen -> blood glucose is reduced.
Low blood glucose -> pancreas detects this and releases glucagon -> glucagon travels in blood to liver -> liver converts glycogen to glucose -> blood glucose is raised.